Thesis

Modular synthesis and applications of chiral Tunable Dyes and Fluorophores

WALLABREGUE, Antoine

Abstract

The goal of this PhD was to explore the reactivity of a novel N-aminoacridinium salt. This derivative has been used for the preparation of pH-sensitive and fluorescent diaza [4]helicene dyes thanks to particularly facile N-N bond cleavage reactions. This compound has also been used as nitrogen source for the stereospecific aziridination and sulfoximination of unfunctionalized olefins and sulfoxides under metal-free oxidative conditions respectively. The corresponding NH aziridines and sulfoximines were then obtained using mild photoreductive conditions. Moreover, N-aminoacridinium salt was utilized for the preparation of the fisrt small fluorophore (pKa 5.3) which specifically stains for late endosome compartments (pH 4.8-6) and for the synthesis of chiral (helical) BODIPY and azobenzene derivatives.

Reference

WALLABREGUE, Antoine. Modular synthesis and applications of chiral Tunable Dyes and Fluorophores. Thèse de doctorat : Univ. Genève, 2015, no. Sc. 4831

URN : urn:nbn:ch:unige-761582 DOI : 10.13097/archive-ouverte/unige:76158

Available at: http://archive-ouverte.unige.ch/unige:76158

Disclaimer: layout of this document may differ from the published version.

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UNIVERSITÉ DE GENÈVE FACULTÉ DES SCIENCES

Section de chimie et biochimie Département de chimie organique Professeur Jérôme Lacour

Modular Synthesis and Applications of Chiral Tunable Dyes and Fluorophores

THÈSE

présentée à la Faculté des sciences de l’Université de Genève

pour obtenir le grade de Docteur ès sciences, mention chimie

par

Antoine WALLABREGUE

de

Dakar (SENEGAL)

Thèse N° 4831

GENÈVE

Atelier d’impression ReproMail

2015

Publications:

“Modular synthesis of pH-sensitive fluorescent diaza[4]helicenes” Wallabregue, A.; Sherin, P.; Guin, J.; Besnard, C.; Vauthey, E.; Lacour, J.; Eur. J. Org. Chem. 2014, 6431. “Selective imaging of late endosomes with a pH-Sensitive diazaoxatriangulene fluorescent probe” Wallabregue, A.; Moreau, D.; Sherin, P.; Vauthey, E.;Gruenberg, J.; Lacour, J.; Manuscript Submitted. “Stereospecific synthesis of unprotected aziridines and sulfoximines using acridinium ion as photoremovable group” Wallabregue, A.; Popper, M. L.; Moneva Lorente, P.; Lacour, J.; Manuscript in preparation.

à ma fille Sarah, ma famille et en mémoire de mes grand parents

Remerciements

Remerciements

Les résultats rapportés dans ce manuscrit ont été obtenus dans le cadre d’un travail de thèse réalisé au sein du laboratoire du Prof. Jérôme Lacour, dans le département de chimie organique de l’Université de Genève, du 1er Octobre 2010 au 25 Septembre 2015. J’exprime toute ma gratitude et ma reconnaissance au Prof. Jérôme Lacour pour m’avoir donné l’opportunité d’intégrer son groupe de recherche, pour ses conseils, pour la confiance et le soutien qu’il m’a toujours accordé. Je tiens aussi à remercier le Prof. Nathalie Katsonis (Université de Twente) et le Prof. Nicolas Winssinger (Université de Genève) d’avoir eu l’amabilité de bien vouloir juger ce travail de thèse. Je désire ensuite remercier les équipes du service d’analyse: RMN (André Pinto, Marion Pupier et le Dr. Damien Jeannerat), Mass (Eliane Sandmeier, Harry Theraulaz et le Dr. Sophie Michalet) et ainsi que le service de cristallographie (Dr. Laure Guénée et Céline Besnard) pour leur indispensable contributions. Un remerciement particulier à Marie-Louise Popper, Mahesh Vishe, Irene Hernandez, Cecilia Tortoreto, Pau Moneva (alias Mr Pel), au Dr. Amalia Isabel Poblador-Bahamonde, au Dr. Thierry Achard et Dr Florian Médina, pour de nombreuses raisons que je ne peux détailler ici, mais travailler avec vous, a été une expérience enrichissante et spéciale. Une mention spéciale aux Dr. Petr Sherin et Dr. Dimitri Moreau pour nos collaborations enrichissantes et fructueuses. Je tiens ensuite à remercier le Dr. Florian Medina, le Dr. Sébastien Goudedranche, le Dr. Johann Bosson et le Dr. Romain Duwald pour les corrections apportées à ce manuscrit. Il me reste à remercier mes collègues du laboratoire et du département, en particulier: Sté, p’tit Jéjé, Joël, Léo, Alvina, Irene, Alex Combi, Alex Boss, Alejandro (alias Mme Pel), Géraldine, Maya, Danièle, Sandip, Steven, Radim, David, Franck, Jérémy, Manon, David Alonso, Jezabel, Ludovic, Marta, Julio, Christophe, Xiao, Les Sonia, Mireille, pour avoir rendu chaque jour au laboratoire un peu spécial et ces cinq ans inoubliables. Enfin un grand merci à ma famille à qui je dois tout et sans qui rien de tout ça n’aurait été possible. Tout d’abord mes parents, vos sacrifices quotidiens et les valeurs que vous m’avez transmis m’ont quotidiennement inspirés et permis d’en être à ce stade aujourd’hui. Je ne puis vous témoigner toute ma gratitude et ma reconnaissance tellement elles sont grandes, mais je peux vous dire une chose, je vous aime et je suis plus que fier d’être votre enfant. Merci

Remerciements

également à Yérim et Robert qui il y a 14 années de cela m’ont accueilli, soutenu financièrement et moralement et m’ont permis de poursuivre mes études secondaires et universitaires. Merci à Noël, Jean-Marc, Elisabeth, Pierre, Paméla, Tiffany et Thérèse ,vous êtes des frères et sœurs que tout le monde rêverait d’avoir, je demande à dieu que nous restions toujours unis et que chacun d’entre vous puisse s’épanouir et réaliser son rêve. Merci également à Fati pour ces nombreuses années à mes côtés et ton soutien, nos chemins se sont peut être séparés mais la vie nous a donné un merveilleux cadeau qui nous lie à jamais, notre princesse Sarah. A tous et toutes, merci pour votre soutien indéfectible et votre amour.

Abbreviations

Rf: Retardation factor s: Singulet Abbreviations, symbols and units S Ar: Electrophilic aromatic substitution E S Ar: Nucleophilic aromatic substitution Abbreviations N BODIPY: Boron-dipyrromethene SM: Starting material brs: Broad singulet t: Triplet CD: Circular dichroism td: Triplet of doublets COSY: Correlation spectroscopy TD-DFT: Time-dependent density functional theory d: Doublet TLC: Thin layer chromatography DCM: Dichloromethane UV: Ultraviolet dd: Doublet of doublets Vis: Visible DFT: Density functional theory

DIPEA: N,N-Diisopropylethylamine

DMF: N,N-Dimethylformamide Symbols DMQA: Dimethoxyquinacridine δ: Chemical shift dt: Doublet of triplets ε: Extinction coefficient EDG: Electron donating group λ: Wavelength Equiv: Equivalent(s) Φ : Quantum yield ESI-MS: Electrospray ionization mass f υ: Wavenumbers spectrometry J: Coupling constant EWG: Electron withdrawing group τ: lifetime HMBC: Heteronuclear multiple-bond correlation spectroscopy Units HOMO: Highest occupied molecular °C: Degree(s) Celsius orbital µl: Microliter(s) HPLC: High-performance liquid g: Gram(s) chromatography h: Hour(s) HRMS: High-resolution mass Hz: Hertz spectrometry M: Molarity HSQC: Heteronuclear single-quantum mg: Milligram(s) correlation spectroscopy MHz: Megahertz IR: Infrared min: Minute(s) LUMO: Lowest unoccupied molecular orbital ml: Milliliter(s) mmol: Millimole(s) m: Multiplet MO: Molecular orbital mol: Mole(s) MS: Molecular sieves nm: Nanometer(s)

NBS: N-Bromosuccinimide NCS: N-Chlorosuccinimide NIS: N-Iodosuccinimide NMP: N-Methyl-2-pyrrolidone NMR: Nuclear magnetic resonance No.: Number NOESY: Nuclear Overhauser effect spectroscopy PEG: Polyethylene glycol PET: Photoinduced electron transfer ppm: Part(s) per million

Résumé

Modular Synthesis and Applications of Chiral Tunable Dyes and Fluorophores

Récemment une classe particulière d’hélicènes cationiques dénommés dimethoxyquinacridinium DMQA+ 1.43 a été synthétisé à partir d’un simple précurseur cationique 1.45 (Schéma 1).1

Schéma 1: Synthèse du DMQA+ 1.43.

Ces dérivés, qui peuvent contenir des atomes d'oxygène et/ou d'azote substitués sont ‡ -1 2 chimiquement et configurationnellement stables (ΔGracem ≈ 42 kcal.mol à 200 °C). Cette + stabilité a été mise en évidence par des valeurs de PKR mesurées assez élevées (comprises entre 14 et 19) et a ainsi permis l’étude de ces hélicènes cationiques dans différents domaines allant de la chimie-physique à la biologie.3 En plus, ces colorants présentent des propriétés optiques dans le domaine du rouge et du proche infrarouge du spectre électromagnétique de la lumière, faisant de ce fait de ces molécules, des membres de la sous famille des hélicènes azotés fluorescents. En général, la grande stabilité des DMQA+ 1.43 les rend insensibles aux variations de pH (2

1 a) B. W. Laursen, F. C. Krebs, Chem. Eur. J. 2001, 7, 1773-1783; b) B. W. Laursen, F. C. Krebs, Angew. Chem. Int. Ed. 2000, 39, 3432-3434. 2 a) J. Gouin, T. Bürgi, L. Guénée, J. Lacour, Org. Lett. 2014, 16, 3800; b) J. Guin, C. Besnard, J. Lacour, Org. Lett. 2010, 12, 1748; c) C. Herse, D. Bas, F. C. Krebs, T. Bürgi, J. Weber, T. Wesolowski, B. W. Laursen, J. Lacour, Angew. Chem., Int. Ed. 2003, 42, 3162

3 a) J. Bosson, J. Gouin, J. Lacour, Chem. Soc. Rev. 2014, 43, 2824; b) F. Dumitrascu, D. G. Dumitrescu, I. Aron, ARKIVOC 2010, 1. i

Résumé reporté. C’est donc logiquement, qu’il a été décidé d'introduire un atome d'azote basique à la périphérie du squelette du [4]hélicène afin de résoudre ce problème.

Cela a été réalisé grâce à l’utilisation d’un nucléophile α tel que l’hydrazine, qui a été utilisé comme donneuse d’atome d’azote. C’est ainsi qu’avec l’usage de deux stratégies de synthèse complémentaires, dont la plus convergente (voie B) s’appuie sur l’utilisation de l’ion acridinium 2.5j comme précurseur central, qu’une grande variété de colorants racémiques 2.4 (11 molécules) avec divers substituants a été synthétisé en deux étapes seulement (Schéma 2). Les rendements de cette réaction varient entre 60 et 90%.4

Schéma 2: Les différentes voies de synthèse utilisées pour la préparation des colorants 2.4.

Les quinacridines hélicoïdales 2.4, résultante de la rupture spontanée de la liaison N-N de l’hydrazine, sont des colorants qui possèdent un pKa de 8,95 et qui plus est, présentent une activité optique dans la partie visible du spectre électromagnétique de la lumière (de 550 à 625 nm, Figure 1). La séparation bien définie des propriétés optiques (absorption et émission) et chiroptiques (pouvoir rotatoire spécifique et dichroïsme circulaire) des composés 2.4 peut être modulée avec le pH. Les énantiomères (M) et (P) du dérivé 2.4f ont pu être séparé par HPLC ‡ sur phase stationnaire chirale et ils présentent une grande stabilité configurationnelle (ΔGracem > 30.7 ± 4.0 kcal·mol-1 à 140 °C). La configuration absolue de ces dérivés a été déterminée par comparaison des spectres de dichroïsme circulaire des formes protonées 2.4f•H+ avec ceux des DMQA+ 1.43 (R = Pr), déjà reportés.4

4 A. Wallabregue, P. Sherin, J. Guin, C. Besnard, E. Vauthey, J. Lacour, Eur. J. Org. Chem. 2014, 6431 ii

Résumé

Figure 1: quinacridinium (gauche), quinacridine (droite) 2.4 et leurs photos correspondantes.

Cependant, le pKa élevé de ces composés, combiné à leurs faibles propriétés d’émission en milieu aqueux (rendement quantique de fluorescence ΦF = 0.6 % et temps de demie de l’état excité τf = 0.45 ns) font des quinacridines 2.4 de mauvais colorants pour la détection d’éventuelles variations du pH intracellulaire. C’est ainsi, que l’aplanissement de ces dérivés hélicoïdaux en diazaoxatriangulenes (DAOTA) a été effectué en une seule étape en les chauffant à 150 °C en présence d’acide, pendant 4 heures. Ces nouveaux colorants 3.3 et 3.4 sont obtenus avec des rendements allant de 30 à 94% sous forme de sels hexafluorophosphate (3.3) et de 90 à 98% sous forme de sels trifluoroacétate (3.4). De plus, ces dérivés présentent des propriétés optiques (ΦF varie entre 13 au 16 % et τf entre 6,5 et 7,8 ns, en milieu aqueux) dans le domaine rouge de la lumière visible (580-600 nm) qui sont nettement supérieures à celles des quinacridines 2.4 et des valeurs de pKa relativement basses (entre 4,8 et 6,6) qui dépendent de la nature de la chaine latérale R.

Schéma 3: Synthèse des sels de diazaoxatriangulenes 3.3 et 3.4. a) pyrH+Cl- (50 equiv), 150 °C, 4 h et puis métathèse avec une solution à 2 M de KPF6, b) solution de NaHCO3 sat puis solution de 1M de CF3CO2H.

Ainsi, en collaboration avec le docteur Dimitri Moreau du laboratoire du professeur Jean Grunberg (Université de Genève), ces nouveaux colorants ont été testé comme marqueur biologique des endosomes. Ces compartiments cellulaires fonctionnent comme des plaques tournante du trafic majeur dans la cellule à l’intersection de l’endocytose, l’autophagie et de la dégradation dans les lysosomes. Habituellement, l’identification et la caractérisation des endosomes, plus particulièrement les précoces est obtenue par microscopie à fluorescence, en iii

Résumé utilisant des anticorps couplés à des colorants ou à des protéines génétiquement modifiées telle que la GFP (protéine fluorescente verte).5 Toutefois, il existe un intérêt croissant pour les techniques rapides et non invasives basés sur l’utilisation de molécules de faible poids moléculaire.6 Cependant, le principal défi est de parvenir à une détection sélective de l'organite d'intérêt,7 surtout si ces organelles présentent des caractéristiques similaires comme par exemple le pH des endosomes précoces et tardives qui est respectivement de 6,2 et 5–5.5.8 Par conséquent, il a été décidé d’utiliser ces dérivés 3.4 comme marqueur sélectif des endosomes tardifs, et qui plus est, d’employer le pH comme vecteur de discrimination. De façon intéressante, lorsque les DAOTA 3.4 (qui sont soluble dans le tampon phosphate salin, PBS) sont incubés avec des cellules de type HeLA pendant 5 heures, la forme protonée du DAOTA 3.4a•H+ (R = Hexadecyl) provoque un marquage sélectif des endosomes tardifs (Figure 2, partie A). En effet, l’analyse au microscope à fluorescence des cellules en temps réel ou fixé avec le paraformaldéhyde (PFA) montre très clairement une colocalisation du colorant avec la protéine Lamp 1 et le phospholipide non conventionnel LBPA, tous deux exprimés par les endosomes tardifs.9 Le marquage de cellules fixées est une caractéristique très importante de ce colorant, car il n’y a pas de molécules à notre connaissance qui possèdent cette propriété. Les expériences contrôle réalisées démontre que l’origine de cette fixation est une quaternisation de l’azote hybridé sp2 de 3.4a, lorsque ce dernier est en présence de PFA. De plus, une perte totale du marquage cellulaire a été observé lors de l’utilisation d’inhibiteurs des pompes à proton cellulaire V-ATPase tels que la concanamycin B et bafilomycine A et le protonophore ionomycine (Figure 2, partie C). Tout cela, met en exergue l'importance de l’atome d'azote faiblement basique (pKa 4,8) à la fois pour la sélectivité et la fixation du colorant.

5 Y. Urano, D. Asanuma, Y. Hama, Y. Koyama, T. Barrett, M. Kamiya, T. Nagano, T. Watanabe, A. Hasegawa, P. L. Choyke, H. Kobayashi, Nat Med 2009, 15, 104; G. Miesenbock, D. A. De Angelis, J. E. Rothman, Nature 1998, 394, 192. 6 J. Han, K. Burgess, Chem. Rev. 2009, 110, 2709. 7 a) A. Sampedro, R. Villalonga-Planells, M. Vega, G. Ramis, S. Fernandez de Mattos, P. Villalonga, A. Costa, C. Rotger, Bio. chem. 2014, 25, 1537; b) D. Soulet, B. Gagnon, S. Rivest, M. Audette, R. Poulin, J. Biol. Chem. 2004, 279, 49355. 8 a) C. C. Scott, J. Gruenberg, Bioessays 2011, 33, 103; b) V. Marshansky, M. Futai, Curr Opin Cell Biol. 2008, 20, 415. 9 T. Kobayashi, E. Stang, K.S. Fang, P. de Moerloose, R.G. Parton, J. Gruenberg, Nature 1998, 392, 193. iv

Résumé

Figure 2: Partie A. Cellules HeLa traitées avec 50µM (3.4a) pendant 5h, et fixé avec du PFA. Les cellules ont ensuite été marquées avec des anticorps dirigés contre LBPA et Lamp 1, puis avec des anticorps secondaires marqués, et analysées par microscopie à fluorescence. Les noyaux sont colorés avec du DAPI. Partie B. Cellules HeLa traitées avec 300 µm (3.4a) pendant 18 heures et analysées comme ci-dessus en utilisant des anticorps dirigés contre EEA1. Partie C. Cellules HeLa traitées pendant 3 heures avec 30 µM (3.4a) avec 1 µM d'ionomycine, 0,1 µM de concanamycin B ou 1 µM de bafilomycine A, ont été analysés en temps réel, sans fixation, par microscopie à fluorescence

v

Résumé

La rupture relativement facile de la liaison N-N survenant dans la formation des quinacridines 2.4 a été vue comme opportunité pour utiliser l’acridinium 2.5j en tant que source d’azote. Ainsi, il a été décidé de développer une nouvelle méthode de synthèse de substrats intéressants en chimie organique tels que les aziridines et sulfoximines basée sur l’utilisation de 2.5j. En effet, ces dérivés sont présents dans plusieurs composés biologiquement actifs (antibiotiques et anti tumoraux) et sont également utilisés en chimie organique comme précurseurs pour la synthèse de molécules diverses et variées.10 En général, la préparation d’aziridines protégées est très bien documentée, et est réalisée selon deux approches différentes.11 La première est la cyclisation d’amino-alcools ou de composés analogues. Ces dérivés sont aussi les intermédiaires de l’addition des groupements diazo ou des ylures de soufre sur une imine protégé.12 La seconde est l’addition de nitrenes (générés thermiquement, photochimiquement ou par oxydation) ou de précurseurs (nitrenoides) tels 13 que les azotures organiques (ArN3 et TosN3) ou les iminoiodinanes sur un alcène (Figure 3). Toutefois, les aziridines générés par ces méthodes sont protégés avec groupements fonctionnels (sulfonamides et phthalimide) qui sont difficilement clivable sans porté atteinte à l’hétéroccyle. L’addition de nitrenes ou nitrenoides est aussi la voie de choix qui est utilisée pour la préparation de sulfoximines et sulfimides.14

10 a) M. Lautens, K. Fagnou, V. Zunic, Org. Lett. 2002, 4, 3465; M. T. Reetz, R. Jaeger, R. Drewlies, M. Hubel, Angew. Chem. Int. Ed. Engl. 1991, 30, 103 and références citées. 11 Aziridines and Epoxides in Organic Synthesis (Ed.: A. Yudin),Wiley-VCH, Weinheim, 2006 12 a) D. V. Kashelikar, P. E. Fanta, J. Am. Chem. Soc. 1960, 82, 4927; b) P. A. Leighton, W. A. Perkins, M. L. Renquist, J. Am. Chem. Soc. 1947, 69, 1540; c) H. Wenker, J. Am. Chem. Soc. 1935, 57, 2328. d) S. E. Larson, G. L. Li, G. B. Rowland, D. Junge, R. C. Huang, H. L. Woodcock, J. C. Antilla, Org. Lett. 2011, 13, 2188; e) A. L. Williams, J. N. Johnston, J. Am. Chem. Soc., 2004, 126, 1612; f) J. S. Yaday, B. V. S. Reddy, P. N. Reddy, M. Shesha Rao, Synthesis, 2003, 1387; g) J. C. Antilla, W. D. Wulff, Angew. Chem. Int. Ed. 2000, 39, 4518; h) J. C. Antilla, W. D. Wulff, J. Am. Chem. Soc. 1999, 121, 5099; i) L. asarrubios, J. A. Perez, M. Brookhart, J. L. Templeton, J. Org. Chem. 1996, 61, 8358; j) W. Xie, J. Fang, J. Li, P. G. Wang, Tetrahedron 1999, 55, 12929 k) E. J. Corey, M. Chaykovsky, J. Am. Chem. Soc., 1965, 87, 1353;l) A. W. Johnson , R. B. LaCount, J. Am. Chem. Soc., 1961, 83, 417 13 a) Copper catalyzed asymmetric synthesis (Ed: A. Alexakis), John Wiley & Sons, Wiley-VCH, 2013, 13 T. Siu, A. K. Yudin, J. Am. Chem. Soc. 2002, 124, 530; b) L. B. Krasnova, R. M. Hili, O. V. Chernoloz, A. K. Yudin, Arkivoc, 2005, 4, 26; c)J. Li, J.-L. Liang, P. W. H. Chan, C.-M. Che, Tetrahedron Lett. 2004, 45, 2685. 14 V. Bizet, C. M. M. Hendriks, C. Bolm, Chem. Soc. Rev., 2015, 44, 3378. vi

Résumé

Figure 3: Synthèse d’aziridines protégés

Cependant, de récentes publications décrivant de nouvelles méthodes permettant l’accès à ces dérivés non protégé NH ont été reporté.15 Malgré cela, de nouvelles procédures sont toujours nécessaires. Il a été donc décidé d’utiliser l’acridinium 2.5j comme précurseur pour l’aziridination oxydante des oléfines et la préparation de sulfoximines et sulfimides grâce à l’emploi d’iodosobenzene diacetate 4.7 (Figure 4). Divers produits protégés ont été obtenus (22 exemples) avec des rendements allant de 16 à 99% dans le cas des aziridines protégées 4.41 et de 70 à 99% pour les sulfoximines et sulfimides, respectivement 4.66 et 4.67. Ces réactions sont stéréospécifiques et leurs mécanismes passent probablement par la formation d’un précurseur de nitrene de type singulet, expliquant ainsi la stéréochimie des produits.16 Dans le cas des alcènes non activés comme les aliphatiques ou les thioethers, l’utilisation d’une base inorganique comme MgO a été cruciale pour l’isolation des produits correspondants avec des rendements élevés.17

Schéma 4: Aziridination des alcènes et imidation des sulfoxides et thioethers

15 Y. Zhu, Q. Wang, R. G. Cornwall, Y. Shi, Chem. Rev. 2014, 114, 8199 16 R. S. Atkinson, Tetrahedron 1999, 55, 1519. 17 C. G. Espino, J. Du Bois, Angew. Chem. Int. Ed. 2001, 40, 598. vii

Résumé

De façon intéressante, lorsque des alcènes riches en électron comme le p- methoxystyrene ou des dérivés analogues sont utilisées comme substrats seuls les produits aminoacétoxyls 4.49 ont été isolés avec des rendements allant de 70 à 90% (4 exemples, Schéma 5). Des mécanismes passant par l’ouverture en milieu acide de l’aziridine correspondant ou l’oxydation directe de l’alcène précédent une attaque nucléophile de 2.5j, ont été proposés.18

Schéma 5: Aminoacétoxylation des dérivés de styrènes

Après l’addition de l’azote, le groupement acridine a été enlevé en utilisant des conditions de clivage photoréductrices relativement douces. En effet, l’emploi de LED verte (530 nm) à 1 W comme source lumineuse et de TMEDA comme source d’électron et probablement de proton a permis la préparation d’aziridines (10 exemples), de sulfoximines (5 exemples) et d’un sulfimide non protégés NH (Schéma 6).19 Cette réaction est particulièrement efficace pour les aziridines substituées avec des groupements électroattracteurs 4.41a-g et les sulfoximines 4.66 avec des rendements allant respectivement de 77 à 90 % et de 78 à 90%. Néanmoins, l’utilisation d’une quantité catalytique (20%) d’acide de Lewis B(C6F5)3 est nécessaire pour promouvoir la rupture N-N des aziridines issues d’alcènes aliphatiques et de styrènes, ainsi que les sulfimides. Toutefois, à cause de leur grande polarité, les aziridines aliphatiques ont été isolés sous forme protégé avec Cbz avec des rendements oscillants entre 82 et 95%. Malheureusement, les aziridines non protégés NH

18 a) H. M. Lovick, F. E. Michael, J. Am. Chem. Soc. 2010, 132, 1249; b) G. F. Koser, Top. Curr. Chem. 2000, 208, 137 c) N. S. Zefirov, V. V. Zhdankin, Y. V. Dan’kov, V. D. Sorokin, V. N. Semerikov, A. S. Koz’min, R. Caple, B. A. Berglund, Tetrahedron Lett. 1986, 27, 3971; d) G. F. Koser, L. Rebrovic, R. H. Wettach, J. Org. Chem. 1981, 46, 4324. 19 a) P. Klán, T. Šolomek, C. G. Bochet, A. Blanc, R. Givens, M. Rubina, V. Popik, A. Kostikov, J. Wirz, Chem. Rev. 2013, 113, 119; b) D. E. Falvey, C. Sundararajan, Photochem. Photobiol. Sci. 2004, 3, 831 viii

Résumé dérivées de styrènes et les sulfimides non protégés n’ont pu être isolés à cause de leur instabilité.

Schéma 6: Déprotection photoréductrice des aziridines, sulfoximines et sulfimides

De plus, cette réaction de clivage est stéréospécifique, comme l’atteste la déprotection du composé 4.66b qui se produit avec rétention de configuration.20 De surcroît, l’expérience de clivage menée dans le CD2Cl2 a prouvé que ce solvant n’était pas la source de protons.

Schéma 7: Déprotection stéréospécifique du sulfoximine énantiopur 4.65b

Comme il a déjà été présenté, les quinacridines 2.4 précédemment synthétisés, sont des hélicènes stables qui présentent des propriétés optiques et chiroptiques intéressantes dans le domaine du visible de la lumière pouvant être modulé avec le pH (vide supra). Mais, ces propriétés sont relativement faibles. C’est dans ce contexte qu’il a été décidé de retourner cette situation à notre avantage, et nous nous sommes demandé si une simple modification structurelle ou l’introduction d’un groupement fonctionnel ne pouvait pas permettre la synthèse de quinacridines avec des propriétés optiques et chiroptiques plus élevées.

ix

Résumé

Pour résoudre ce problème, une approche contre intuitive basée sur la fonctionnalisation électrophiles des DMQA+ 1.43 cationique a été développée. En effet, l’introduction d’électrophiles fortement électroattracteurs c’est avéré être une bonne stratégie non seulement pour la régiosélectivité de la réaction mais aussi pour les propriétés optiques du + DMQA 1.43 (Schéma 8). En outre, l’introduction de groupements nitro (NO2) et aldéhyde

(CHO) entraine une rupture de la symétrie C2 de la molécule, mais aussi un déplacement chimique des protons du CH2 et du CH3 de la chaine propyl adjacent au groupement fonctionnel introduit, à des basses fréquences (par exemple de 1,2 à 0,4 ppm pour le CH3, Figure 4).

Figure 4: Spectres 1H NMR du DMQA+ 1.43 (haut) et de 5.2 (bas).

Plus important encore, c’est la forte augmentation des propriétés optiques de ces nouveaux dérivés. En général, un déplacement hypsochromique des bandes d’absorption à faibles énergies sont observés (respectivement, de 625 et 550 nm à 550 et 525 nm) ainsi qu’une forte augmentation des valeurs de fluorescence mesurées (respectivement, ΦF = 40 and

42% and τf = 14.5 and 16.2 ns pour 5.1 et 5.2, contre 7% and 5.5 ns pour 1.43 dans CH3CN).

20 a) H. Okamura, C. Bolm, Org. Lett. 2004, 6, 1305; b) C. R. Johnson, R. A. Kirchhoff, H. G. Corkins, J. Org. Chem. 1974, 39, 2458. x

Résumé

Schéma 8: Nitration et formylation du DMQA+ 1.43

Par conséquent, l’approche de la fonctionnalisation (la nitration et la formylation en particulier) a été utilisée pour augmenter les propriétés optiques des quinacridines 2.4 et ainsi générer de nouveaux colorants chiraux. La nitration, la formylation et le couplage diazoïque de la quinacridine 2.4e avec respectivement un mélange 1:1 d’acide nitrique et de CH2Cl2,

DMF et POCl3 (12 et 24 équivalents) et un sel de diazonium a permis l’obtention des quinacridines 5.3, 5.4 et 5.8 avec respectivement des rendements de 96, 85 et 57%. (Schéma 9)

Schéma 9: Fonctionnalisation de la quinacridine 2.4e

Les dérivés 5.3 et 5.4 sont de très bons colorants possédant des optiques et chiroptiques qui peuvent être modulé avec le pH. La quinacridine 5.3 possède un pKa = 7 et présente une augmentation de ces propriétés de fluorescence (ΦF de 2% à 22% et τf de 5.2 à 10.2 ns) et chiroptiques avec l’acidification du milieu environnant (figure 4). xi

Résumé

Δε

+ ____ + Figure 4: Spectre ECD de (P)-(+)-[5.3•H ][BF4] ( ) et (M)-(–)-[5.3•H ][BF4] (- - -); et de (P)-(+)-5.3 (°°°°°)

-5 and (M)-(–)-5.3 (˟˟˟˟˟). Solutions dans CH3CN, 20 °C, C = 1·10 M.

Cette augmentation est très probablement dû à la formation de liaison hydrogène 2 intramoléculaire entre le NO2 et l’azote sp protonée NH. En effet, les calculs effectués en collaboration avec Mr. Pau Moneva de l’université de Genève ont révélé que la quinacridinium 5.3•H+ présente une énergie de rotation autour de la liaison carbone azote reliant le groupement le NO2 avec le cycle benzénique de l’hélicène, supérieure (13.6 kcal.mol-1) à celle de la quinacridine 5.3 (2.6 kcal.mol-1).21

Figure 5: 5.3•H+ and 5.3 and their corresponding photo after excitation at 365 nm.

La quinacridine 5.4 quant à elle, présente de grandes valeurs de propriétés optiques aussi bien en milieu acide que basique. Dans le premier cas (5.4•H+) la formation d’une liaison hydrogène intramoléculaire entre la paire libre de l’oxygène du carbonyle et l’azote sp2 protoné NH a été postulé. Alors que pour le second 5.4, une rotation bloquée du carbonyle autour de la liaison C-C le reliant avec cycle benzénique de l’hélicène a été invoquée (Figure

21 Pau Moneva computational chemistry project, University of Geneva, 2015 xii

Résumé

6). 22 Tout comme la quinacridine 5.3, la quinacridine 5.4 présente aussi une augmentation de ces propriétés chiroptiques avec l’acidification.

Figure 6: Propriétés des quinacridine 5.4•H+ and 5.4.

S’appuyant sur le constat que de simples substituants tels qu’un NO2 ou un CHO ont une profonde influence sur les propriétés optiques et chiroptiques des quinacridines asymétriques et sur le fait que ces groupes fonctionnels sont aussi des synthons facilement transformables en une variété d'autres groupes fonctionnels ou systèmes, il a été décidé d’utiliser la quinacridine 5.4 pour synthétiser une nouvelle famille de BODIPY chirale. En effet, ces colorants ont été intensivement étudiés et utilisés dans de nombreux domaines pour leurs propriétés de luminescence.23 Néanmoins, il y a peu de publications reportant la synthèse de BODIPY chiraux.24 Par conséquent, il a été décidé d’utiliser la géométrie hélicoïdale de l’hélicène portant un ligand diamine pour développer une nouvelle famille de BODIPY chiral.

Le composé 5.15 a donc été préparé en deux étapes avec un bon rendement de 82% (Schéma 10). L’étude de ces propriétés a montré que 5.15 présente un déplacement hypsochromique de ses bandes d’absorption à faibles énergies par rapport à 5.4•H+ (de 628 à 580 nm). De surcroît son rendement quantique de fluorescence est nettement inférieur à son précurseur 5.4•H+ (39% contre 26% pour 5.15) ainsi que les valeurs du pouvoir rotatoires et de ces effets Cotton de ces énantiomères.

22 a) M. Rabinovitz,A. Ellencweig, Tetrahedron Lett. 1971, 46, 4439; b) F. A. L. Anet , M. Ahmad, J. Am. Chem. Soc., 1964, 86, 119. 23 a) Treibs, A.; Kreuzer, F.-H. Liebigs Ann. Chem. 1968, 718, 208; b) Boens, N.; Leen, V.; Dehaen, W. Chem. Soc. Rev. 2012, 41, 1130; c) A. Loudet, K. Burgess, Chem. Rev. 2007, 107, 4891; Frath, D.; Massue, J.; Ulrich, G.; Ziessel, R. Angew. Chem. Int. Ed. 2014, 53, 2290 24 a) E. M. Sanchez-Carnerero, F. Moreno, B. L. Maroto, A. R. Agarrabeitia, M. J. Ortiz, B. G. Vo, G. Muller, S. de la Moya, J. Am. Chem. Soc. 2014, 136, 3346; b) E. M. Sánchez-Carnerero, F. Moreno, B. L. Maroto, A. R. Agarrabeitia, J. Bañuelos, T. Arbeloa, I. López-Arbeloa, M. J. Ortiz, S. de la Moya, Chem. Commun. 2013,49, 11641. xiii

Résumé

Schéma 10: Synthèse du BODIPY 5.15.

Finalement, une dernière famille de colorants basée sur le groupe fonctionnel azo a aussi été développée. Ces colorants synthétiques sont d’une grande importance dans l'industrie.25 Cependant, il n'y a que peu d'exemples d’azobenzenes fluorescents à cause de la facile photoisomérisation de ces dérivés azoïques dans leurs états photoexcités.26 Une stratégie développée par le groupe de Kawashima et de fixer la paire d’électrons libre de l’azote, rendant ainsi la photoisomérisation improbable dans l'état excité.27 Toutefois, il n’y a aucune publication faisant état de dérivés azoïque chiraux. Nous avons donc vu dans le composé 5.8 une opportunité de changer cette situation. Le dérivé azoïque a été traité avec du

BF3•OEt2 en présence de diisopropylethylamine (DIPEA) comme représentée dans le schéma 11.

Schéma 11: Synthèse des azobenzenes fluorescents 5.18a and b

Un composé majoritaire a pu être isolé, cependant sa nature chimique exacte reste en ce moment discutable. En fait, il y a deux régioisomères possibles avec un cycle à 6 ou 5 chaînons. Alors que des publications précédentes favorisent le cycle à 5 5.18b, les données

25 a) J. Griffiths, Chem. Soc. Rev. 1972, 1, 481; b) K. Venkataraman, The chemistry of synthetic dyes, Academic Press, New York, 1956; b) F. Hamon, F. Djedaini-Pilard, F. Barbot, C. Len, Tetrahedron 2009, 65, 10105. 26 a) Y. Wakatsuki, H. Yamazaki, P. A. Grutsch, M. Santhanam, C. Kutal, J. Am. Chem. Soc. 1985, 107, 8153; b) M. Shimomura, T. Kunitake, J. Am. Chem. Soc. 1987, 109, 5175; c) M. Ghedini, D. Pucci, G. Calogero, F. Barigelletti, Chem. Phys. Lett. 1997, 267, 341; d) M. Ghedini, D. Pucci, A. Crispini, I. Aiello, F. Barigelletti, A. Gessi, O. Francescangeli, Appl. Organomet. Chem. 1999, 13, 565; e) I. Aiello, M. Ghedini, M. La Deda, J. Lumin. 2002, 96, 249; f) M. Han, M. Hara, J. Am. Chem. Soc. 2005, 127, 10951; g) M. R. Han and M. Hara, New J. Chem. 2006, 30, 223. 27 a) J. Yoshino, N. Kano, T. Kawashima, Dalton Trans. 2013, 42, 15826; b) J. Yoshino, N. Kano, T. Kawashima, Chem. Commun. 2007, 559. xiv

Résumé récoltées plaident pour le cycle à 6 5.18a.28 C’est ainsi que 5.18a a été considéré comme le produit obtenu, même si la détermination exacte de la structure dans le futur peut nous démontrer le contraire. En termes de propriétés optiques, 5.18a présente une bande d’absorption large et intense dans la partie jaune de la lumière visible, centré sur 570 nm. La fluorescence de ce produit est centrée sur 595 nm avec des rendements quantiques respectivement de 7 et 17 % et des temps de demi de 1,7 et 2,8 ns dans l’acétonitrile et le dichlorométhane. Ces valeurs sont prometteuses car les azobenzenes fluorescents le sont principalement dans des solvants apolaires et de plus les composés de ce type dont le bore est substitué par des atomes de fluor sont en général non fluorescents.27a Des expériences supplémentaires de fluorescence (temps de demie vie et spectre d’excitation) ont été réalisés en excitant le composé à différentes longueurs, et d’après les données la fluorescence observée est issu d’une seule espèce chimique. Ceci tend à confirmer que le produit obtenu est le composé 5.18a car pour le composé 5.18b deux espèces en équilibre sont attendues comme montré dans le Schéma 12.24

Schéma 12: Isomérisation du compose 5.19b induite par la lumière visible

28 a) X. Su, I. Aprahamian, Chem. Soc. Rev. 2014, 43, 1963; b) Y. Yang, R. P. Hughes, I. Aprahamian, J. Am. Chem. Soc. 2014, 136, 13190; c) Y. Yang, R. P. Hughes, I. Aprahamian, J. Am. Chem. Soc. 2012, 134, 15221 xv

Table of contents

Table of Contents

Chapter I: General Introduction 1

1.1 Preamble 1 1.2 Helical Chirality 2 1.3 Nomenclature of Helicenes 2 1.4 Synthesis and Properties of Carbohelicenes 3 1.5 Configurational Stability and Racemization Barrier 7 1.6 Resolution Methods 9 1.7 Applications of Carbohelicenes 13 1.8 Synthesis of Azahelicenes 14 1.9 Applications of Azahelicenes 18 1.10 Highly Stable Cationic Aza[4] and [6]Helicenes 19

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines 30

2.1 Preamble 30 2.2 Synthesis of Quinacridine Derivatives 31 2.3 Mechanism of N-N Bond Cleavage 38 2.4 Resolution and Configuration Stability of Quinacridine Derivatives 40 2.5 Photophysical Properties 44 2.6 Applications 49

Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangulenes as Late Endosomes Probes 50

3.1 Preamble 50 3.2 Synthesis and Properties of pH-Sensitive Diazaoxatriangulenes 51 3.3 Application 56

Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines 61

4.1 Preamble 61 4.2 Synthesis of Protected Aziridines 62 4.3 Synthesis of Unprotected Aziridines 66 4.4 Synthesis of Protected Aziridines, Sulfoximines and Sulfimides, using N-Aminoacridinium Salt as Nitrogen Source 73 4.4.1 Preparation of Protected Aziridines 73 4.4.2 Aminoacetoxylation of Electron rich Olefins 78 4.4.3 Preparation of Protected Sulfoximines and Sulfimides 81 4.4.4 Synthesis of Protected Sulfoximines and Sulfimides using N-aminoacridinium Ion 84 4.5 Stereospecific Synthesis of NH Aziridines and Sulfoximines, Mediated by Visible Light Photoirradiation 86

Table of contents

Chapter 5: Synthesis and Properties of Chiral pH-Sensitive Quinacridines, BODIPY-like and Azobenzene Fluorophores. 101

5.1 Preamble 101 5.2 Electrophilic Functionalizations of Symmetrical DMQAs (preliminary results) 102 5.3 Functionalization of Quinacridine 2.4e 106 5.4 Synthesis of pH-Sensitive and (Chir)Optical Switch Quinacridine 108 5.5 Chiral BODIPY Based on Quinacridine Scaffold 117 5.6 Chiral and Fluorescent Azobenzene Based on Quinacridine 120

Experimental Part 127

General Remarks 127 Synthesis of pH-Sensitive and Fluorescent Quinacridines 129 Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangulenes as Late Endosomes Probes 153 N-aminoacridinium Ion as Nitrogen Source For The Synthesis of Unprotected Aziridines and Sulfoximines 157 Synthesis and Properties of Chiral pH-Sensitive Quinacridines, BODIPY-like and Azobenze Fluorophores 187 Appendix 194 Spectral and Photophysical Properties of Triangulenes 3.3 and 3.4 in Organic Solvents 194 X-Ray Datas 202 Racemisation barrier determination 205

Chapter 1:General Introduction

Chapter I: General Introduction

1.1 Preamble

This manuscript will mainly deal with the development of new fluorophores based on

[4]helicene and triangulene scaffolds. This chapter will give a brief introduction on the chemistry of carbohelicenes and their properties, the nitrogen containing aza-analogues, and finally a special class of cationic [4]helicenes known as the quinacridinium salts.

Helicenes are particular class of molecules made of ortho-fused aromatic rings. These compounds adopt a twisted conformation due to the steric repulsion arising from their terminal aromatic rings or substituents. Since helical conformations often minimize the strain, it can be formed as a way for molecules to relieve their intrinsic tension. Indeed nature has adopted this conformation for the most important biomolecules such as DNA (A, B, Z),29

RNA (m, t) and proteins, even if these biopolymers are not aromatic. In fact, these biomolecules are constituted of base pairs or amino acids which are involved in inter and intramolecular hydrogen bonding interactions leading to the formation of the helices (Figure

1.1).

Figure 1.1: Representation of the helical shape of B-DNA double-strand (Left) and proteins alpha helix (Right).

29 J. D. Watson, F. H. C. Crick, Nature 1953, 171, 737.

1

Chapter 1: General Introduction

1.2 Helical Chirality

In term of stereochemistry, helicity is an important and intriguing type of molecular chirality. In fact, helicenes are chiral despite the absence of stereogenic centers in the

30 molecular backbone. They often display C2 symmetry with an axis perpendicular to the helical one (Figure 1.2, right). Thus, two enantiomers exist and are defined as right and left- handed helices for P and M configurations respectively31 (Figure 1.2, left).

Figure 1.2: a) Schematic representation of P and M enantiomers of carbo[6]helicene; b) Helical and C2 symmetry axis.

1.3 Nomenclature of Helicenes

The helicene nomenclature was introduced by Newman and Lednicer in 1956.32 The different derivatives are named by using a Greek prefix or a number in bracket [n] before the helicene name, denoting the number of ortho-fused aromatic rings in the framework.

Therefore penta, hexa and heptahelicene are simply referred as [5], [6] and [7]helicene respectively. Later, to differentiate fully carbon helicenes from the ones containing heteroatoms, Wynberg brought up the term heterohelicenes33 and thus for products containing

30 a) M. Gingras, Chem. Soc. Rev. 2013, 42, 968; b) M. Gingras, G. Felix, R. Peresutti, Chem. Soc. Rev. 2013, 42, 1007; c) Y. Shen, C. Chen, Chem. Rev. 2012, 112, 1463; d) A. Urbano, Angew. Chem. Int. Ed. 2003, 42, 3986; e) T. J. Katz, Angew. Chem., Int. Ed. 2000, 39, 1921; f) A. E. Rowan, J. M. Nolte, Angew. Chem., Int. Ed. 1998, 37, 63; g) K. P. Meurer, F. Vögtle, Top. Curr. Chem. 1985, 127, 1; h) W. H. Laarhoven, W. J. C. Prinsen, Top. Curr. Chem. 1984, 125, 63; i) R. H. Martin, Angew. Chem. 1974, 86, 727. 31 a) Eliel, E. L.; Wilen, S. H. Stereochemistry of Organic Compounds; Wiley: New York, 1994, Chapter 14, 1121, 1163; b) R. S. Cahn; C. K. Ingold; V. Prelog Angew. Chem., Int. Ed. Eng. 1966, 5, 385. 32 M. S. Newman, D. Lednicer, J. Am. Chem. Soc. 1956, 78, 4765. 33 M. B. Groen, H. Schadenberg, H. Wynberg, J. Org. Chem. 1971, 36, 2797.

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Chapter 1: General Introduction

nitrogen, oxygen, and sulfur atoms; the prefix aza, oxa and thia usually preceded the word helicene respectively.

1.4 Synthesis and Properties of Carbohelicenes

Though known since the beginning of the 20th century, with the seminal work of Meisenheimer and Witte34 who synthesized in 1903 the first diaza [5]helicenes 1.2 and 1.3 (Scheme 1.1, via reductive cyclization of 2-nitronaphthalene helicenes), helicenes remained scarcely described until the 1950s. Indeed Weitzenböck and Klingler35 prepared carbo[5]helicene 1.4 (Scheme 1.1) in 1918, nevertheless structural evidence was brought by Cook36 in 1933 after synthesizing carbo[5]helicene 1.5 by series of Pschorr cyclizations (Scheme 1.1). Fuchs and Niszel37 synthesized and characterized aza [6]helicene 1.6 via a double Bucherer reaction in 1927.

Scheme 1.1: Structures of first helicenes prepared.

The study of helicenes only reemerged with the groundbreaking work of Newman and co-workers, who reported the preparation and the resolution of 1,12-dimethylbenzo[4]helicene 1.7 (in 8 steps) and [6]helicene 1.1 (in 12 steps) (Scheme 1.1) using cinchonidine and α-

34 J. Meisenheimer, K. Witte, Chem. Ber. 1903, 36, 4153. 35 R. Weitzenböck, A. Klinger, Monatsh. Chem. 1918, 39, 315. 36 R. Weitzenböck, A. Klinger, J. W. Cook, J. Chem. Soc. 1933, 1592. 37 W. Fuchs, F. Niszel, Ber. Dtsch. Chem. Ges. 1927, 60, 209.

3

Chapter 1: General Introduction

(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)-propionic acid (TAPA) 1.8 respectively. 38 In the latter case, the resolution occurs by selective precipitation of the complex arising from interaction between the electron deficient TAPA and electron rich [6]helicene 1.1 (This will be discussed more in detail in section 1.6 of this chapter). The absolute configuration of these compounds could not be assigned at that time.

A great achievement was then realized in the field, during the following decade with the photochemical preparation of [7]helicene disclosed by Martin and co-workers in 1967.39 This discovery opened the “avenue” of photoinduced cyclizations which became the standard method for the synthesis of helicenes (from [5] to [14]) during several decades. In fact, the success of this methodology relies on the particular simplicity of the photochemical procedure and the easy accessibility to stilbene precursors by Wittig olefination (see Scheme 1.2).40 Moreover, Wynberg extended the scope of this reaction to the synthesis of sulfur containing helicenes.41

Yet, photocyclization process can give rise to regioisomers or over oxidized products like 1.9 and 1.10 respectively, (Scheme 1.2) which are generally difficult to separate from helicenes products. To overcome this problem, Katz developed an efficient bromo-directed photocyclization method which controls the regioselectivity of the reaction, affording helicenes in good yield (75%, Scheme 1.3 method a).42

38 a) M. S. Newman, D. Lednicer J. Am. Chem. Soc. 1956, 78, 4765; b) M. S. Newman, R. M. Wise J. Am. Chem. Soc. 1956, 78, 450; c) M. S. Newman, W. B. Lutz, D. Lednicer, J. Amer. Chem. Soc. 1955, 77, 3420. 39 a) R. H. Martin, M. Baes, Tetrahedron 1975, 31, 2135; b) R. H. Martin, Angew. Chem. Int. Ed. Engl. 1974, 13, 649; c) R. H. Martin, M. J. Marchant, Tetrahedron 1974, 30, 347; d) R. H. Martin, M. J. Marchant, Tetrahedron Lett. 1972, 13, 3707; e) R. H. Martin, N. Defa, H. P. Figeys, M. Flammang, J. P. Cosyn, M. Gelbcke, J. J. Schurter, Tetrahedron 1969, 25, 4985; f) R. H. Martin, M. Flammang, J. P. Cosyn, M. Gelbcke, Tetrahedron Lett. 1968, 9, 3507; g) M. Flammang, J. Nasielsk, R. H. Martin, Tetrahedron Lett. 1967, 8, 743. 40 a) K. P. Meurer, F. Vogtle, Top. Curr. Chem. 1985, 127, 1. b) W. H. Laarhoven, W. J. C. Prinsen, Top. Curr. Chem. 1984, 125, 63. 41 a) J. H. Dopper, D. Oudman, H. Wynberg, J. Org. Chem. 1975, 40, 3398; b) J. H. Dopper, D. Oudman, H. Wynberg, J. Am. Chem. Soc. 1973, 95, 3692; c) J. Tribout, H. Wynberg, M. Doyle, R. H. Martin, Tetrahedron Lett. 1972, 13, 2839; H. Wynberg, Acc. Chem. Res. 1971, 4, 65; d) M. B. Groen, H. Schadenb, H. Wynberg, J. Org. Chem. 1971, 36, 2797. e) M. B. Groen, H. Wynberg, J. Am. Chem. Soc. 1971, 93, 2968; f) M. B. Groen, G. Stulen, G. J. Visser, H. Wynberg, J. Am. Chem. Soc. 1970, 92, 7218. g) H. Wynberg, M. B. Groen, J. Am. Chem. Soc. 1970, 92, 6664; h) H. Wynberg, M. B. Groen J. Chem. Soc. D: Chem. Commun. 1969, 964; i) H. Wynberg, M. B. Groen, J. Am. Chem. Soc. 1968, 90, 5339. 42 L. Liu, T. J. Katz, Tetrahedron Lett. 1991, 32, 6831.

4

Chapter 1: General Introduction

Scheme 1.2: Photodehydrocyclization of trans-stilbene type into [5]helicene 1.4.

Furthermore, the group of Katz also found that utilizing an excess of propylene oxide (propylene oxide being an in situ scavenger for HI, Scheme 1.3 method b) together with a stoichiometric amount of iodine give higher yields (85%) and lower amount of impurities.43

Scheme 1.3: Synthesis of [7]helicene 1.12.

However, the reduced scope of the photocyclization reaction (only stilbenoïd precursors), as well as its low functional groups tolerance, have directed increasing efforts at finding other alternatives. Consequently, several efforts have been engaged for the preparation of helicenes in larger scale and the widening of the range of products. Among them, a Diels- Alder reaction approach was introduced by Katz and Liu in 1990 using electron rich p- divinylbenzene and electron-poor p-benzoquinone as substrates for the synthesis of [5]helicene and larger.44 An elegant asymmetric version of this reaction was then developed

43 L. Liu, Yang, B.; Katz, T. J.; Poindexter, M. K. J. Org. Chem. 1991, 56, 3769. 44 a) K. Paruch, L. Vyklick, D. Z. Wang, T. J. Katz, C. Incarvito, L. Zakharov, A. L. Rheingold, J. Org. Chem. 2003, 68, 8539; b) S. D. Dreher, K. Paruch, T. J. Katz, J. Org. Chem. 2000, 65, 806; c) K. Paruch, T. J. Katz, C. Incarvito, K. C. Lam, B. Rhatigan, A. L. Rheingold, J. Org. Chem. 2000, 65, 7602; d) C. Nuckolls, T. J. Katz, G.

5

Chapter 1: General Introduction

by Careño and Urbano. Enantioenriched helicenes 1.15 were obtained in good yields and enantiomeric excesses (84%) using enantiopure (+)-(S)-2-(p-tolyl-sulfinyl)-1,4-benzoquinone 1.13 and vinyl naphthalene 1.14 as substrate for this reaction (Scheme 1.4).45

Scheme 1.4: Synthesis of enantioenriched [5]helicene 1.15 by Diels-Alder reaction.

Intramolecular oxidative cyclization,46 cyclizations of ammonium or phosphonium salts,47 metal-catalyzed [2+2+2] cycloisomerization,48 olefin metathesis,49 carbenoid couplings,50 and cross coupling strategies51 were also elaborated to obtain helicenes in an

Katz, P. J. Collings, L. Castellanos, J. Am. Chem. Soc. 1999, 121, 79; e) J. M. Fox, N. R. Goldberg, T. J. Katz, J. Org. Chem. 1998, 63, 7456. f) T. J. Katz, L. B. Liu, N. D. Willmore, J. M. Fox, A. L. Rheingold, S. H. Shi, C. Nuckolls, B. H. Rickman, J. Am. Chem. Soc. 1997, 119, 10054; g) N. D. Willmore, D. A. Hoic, T. J. Katz, J. Org. Chem. 1994, 59, 1889; h) L. Liu, Yang, T. J. Katz, Tetrahedron Lett. 1990, 31, 3983; 45 a) M. C. Careño, R. Hernandez-Sanchez, J. Mahugo, A. Urbano, J. Org.Chem. 1999, 64, 1387. b) M. C. Careño, S. Garcia-Cerrada, A. Urbano, J. Am. Chem. Soc. 2001, 123, 7929. 46 a) J. Larsen, K. Bechgaard, J. Org. Chem. 1996, 61, 1151; b) D. E. Pereira, Neelima; N. J. Leonard, Tetrahedron 1990, 46, 5895; c) H. Rau, O. Schuster, Angew. Chem. Int. Ed. Engl. 1976, 15, 114 47 a) H. J. Bestman, W. Both, Angew. Chem. 1972, 84, 293; b) I. G. Stara, I. Stary, M. Tichy, J. Zavada, V. Hanus, J. Am. Chem. Soc. 1994, 116, 5084. 48 a) A. Jančařík, J. Rybáček, K. Cocq, J. Vacek Chocholoušová, J. Vacek, R. Pohl, L. Bednárová, P. Fiedler, I. Císařová, I. G. Stará, I. Starý, Angew. Chem. Int. Ed. 2013, 52, 9970; b) J. Storch, J. Čermák, J. Karban, I. Císařová, J. Sýkora, J. Org. Chem. 2010, 75, 3137; c) O. Songis, J. Míšek, M. B. Schmid, A. Kollárovič, I. G. Stará, D. Šaman, I. Císařová, I. Starý, J. Org. Chem. 2010, 75, 6889; d) J. Misek, F. Teply, I. G. Stara, M. Tichy, D. Saman, I. Cisarova, P. Vojtisek, I. Stary, Angew. Chem. Int. Ed. 2008, 47, 3188; e) I. G. Stara, Z. Alexandrova, F. Teply, P. Sehnal, I. Stary, D. Saman, M. Budesinsky, J. Cvacka, Org. Lett. 2005, 7, 2547; f) F. Teply, I. G. Stara, I. Stary, A. Kollarovic, D. Saman, S. Vyskocil, P. Fiedler, J. Org. Chem. 2003, 68, 5193; g) F. Teply, I. G. Stara, I. Stary, A. Kollarovic, D. Saman, L. Rulisek, P. Fiedler, J. Am. Chem. Soc. 2002, 124, 9175; h) I. G. Stará, I. Starý, A. Kollárovič, F. Teplý, D. Šaman, M. Tichý, J. Org. Chem. 1998, 63, 4046 49 S. K. Collins, A. Grandbois, M. P. Vachon, J. Côté, Angew. Chem. Inter. Ed. 2006, 45, 2923. 50 M. Gingras, F. Dubois, Tetrahedron Lett. 1999, 40, 1309; F. Dubois, M. Gingras, Tetrahedron Lett. 1998, 39, 5039. 51 a) M. Weimar, d. C. R. Correa, F.-H. Lee, M. J. Fuchter, Org. Lett. 2013, 15, 1706; b) W. Lin, G.-L. Dou, M.- H. Hu, C.-P. Cao, Z.-B. Huang, D.-Q. Shi, Org. Lett. 2013, 15, 1238; c) E. Kaneko, Y. Matsumoto, K. Kamikawa, Chem. Eur. J. 2013, 19, 11837; d) D. Waghray, J. Zhang, J. Jacobs, W. Nulens, N. Basarić, L. V. Meervelt, W. Dehaen, J. Org. Chem. 2012, 77, 10176; e) H. R. Talele, S. Sahoo, A. V. Bedekar, Org. Lett. 2012, 14, 3166; f) H. Kelgtermans, L. Dobrzanska, L. Van Meervelt, W. Dehaen, Org. Lett. 2012, 14, 1500; g) O. Crespo, B. Eguillor, M. A. Esteruelas, I. Fernandez, J. Garcia-Raboso, M. Gomez-Gallego, M. Martin-Ortiz, M. Olivan, M. A. Sierra, Chem. Commun. 2012, 48, 5328; h) M. R. Crittall, H. S. Rzepa, D. R. Carbery, Org. Lett. 2011, 13, 1250; i) N. Takenaka, R. S. Sarangthem, B. Captain, Angew. Chem. Int. Ed. 2008, 47, 9708.

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efficient manner. More recently, a well-designed and elegant tin-mediated non-reducing tandem radical cyclisation was reported by Harrowven and coworkers in 2002 (Scheme 1.5),52 this reaction afforded a new short and effective route to the parent [5]helicenes 1.4 and some of its derivatives in modest to good yields (35-49%, 58% for [5]helicene) starting from readily available di phosphonium 1.16.

Scheme 1.5: Tandem radical cyclization process for the synthesis of [5]helicene 1.4.

1.5 Configurational Stability and Racemization Barrier

The first observation of a racemization phenomenon was made by Newman and Wise38b and measurement of racemization barriers became common practice; 53 in short, within a family of derivatives, the smaller the helicenes, the lower the barrier. For example, [4]helicene 1.17 displays a racemization barrier lower than 16 kcal.mol-1 at 23 °C, which does not allow the physical separation of the enantiomers at room temperature, 1.17 is thus configurationally labile. In another hand, the configurationally stable [6]helicene 1.1 has a racemization barrier of 36 kcal.mol-1 at 27 °C (Scheme 1.6). The configuration stability of helicenes can be increased by using two analogous strategies: substituting the helicenes at terminal positions, or by increasing the number of ortho-fused rings. In both cases, these modifications lead to an increase of the corresponding racemization barriers directly related to the steric hindrance of the terminal rings or substituents. Typical examples of these strategies are exhibit with [4], [5] and [6]helicene (Scheme 1.6). In fact compound 1.18 bearing two methyl groups at the terminal positions is configurationally more stable (racemization barrier at least ≥ 100 kJ.mol-1) than non-substituted 1.17.

52 Harrowven, D. C.; Nunn, M. I. T.; Fenwick, D. R. Tetrahedron Lett. 2002; 43, 7345. 53 H. J. Roland, H. Günter, E. U. Würthwein, J. H. Borkent, J. Am. Chem. Soc. 1996, 118, 6031 and references therein; b) S. Grimme, S. D. Peyerimhoff, Chem. Phys. 1996, 204, 411.

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Chapter 1: General Introduction

The racemization process was furthermore rationalized by Martin and co-workers, who postulated a plausible conformational.54 Lindner and co-workers have also calculated the energy differences between the ground state conformation and some assumed transition states for carbo[6]helicene. They reported that the most plausible geometry for a transition state is one in which the terminal parts of the molecule are parallel or face-to-face to each other such as in a Cs transition state (Figure 1.3).55

Scheme 1.6: Racemization barrier values of some helicenes derivatives.

Based on Lindner’s work (difference of energy between GS and assumed TS) several helicenes racemization mechanisms were computed and then proposed. In short, small helicenes like 4,5-dimethyl[3]helicene and [4]helicene are believed to racemize via a C2v planar transition state (TS) while the higher member ([5], [6], [7] and [8]helicenes) of the homologous series are thought to racemize through a twisted Cs transition state (Figure 1.3). The longer [9]helicene undergo racemization through a more complicated process involving more than one TS.

54 Martin, R. H.; Marchant, M. J. Tetrahedron 1974, 30, 347. 55 Lindner, H. J. Tetrahedron 1975, 31, 281.

8

Chapter 1: General Introduction

Figure 1.3: Ground state (left) and Transition state (right) structures of [4] and [5]helicenes.

As a matter of fact, the low energy racemization barriers for these derivatives especially in the case of [3] to [4]helicene, can be justified by the fact that these molecules are more flexible than originally thought. All the necessary molecular deformations (bond torsions, stretching and bending) are spread all over the molecule.

1.6 Resolution Methods

We have seen from the previous sections that helicenes undergo thermal racemization at various temperatures depending on the number of ortho-fused aromatic rings in the helical structure. Thus, to study their chiroptical properties and investigate their application, it is of great importance to have efficient and robust resolution methods. During the last 60 years numerous approaches have been created. The aim of this section is to give an overview of some of the most outstanding approaches.

In the early research, crystallization in the presence of enantiopure reagents was the principal resolution procedure of helicenes. Nevertheless, the usefulness was somewhat limited as single crystals could only be handpicked limiting thus the procedure to rather small cases. Using this concept Newman and Lednicer achieved in 1955 the first resolution of purely hydrocarbon [6]helicene 1.1 with the α-(2,4,5,7-tetranitro-9-fluorenylideneaminooxy)- propionic acid (TAPA) 1.8 (Figure 1.4), as resolving reagent.38c The resolution process occurs via charge transfer complex of type 1.19 (Figure 1.4). Indeed, enantiopure π-acceptor TAPA reacts efficiently with each π-donor enantiomer of the [6]helicene to form diastereomers

9

Chapter 1: General Introduction

complexes of different stability (in general (+)-(S)-TAPA has stronger interaction with (-)- (M)-helicenes and vice versa). In a typical procedure, the racemic [6]helicene 1.1 is dissolved in a benzene solution with the optically active TAPA. Then subsequent addition of ethanol to the benzene mixture affords crystallization of the active complex [helicene/TAPA]. This resolving agent is known nowadays as Newman’s reagent.

Figure 1.4: Use of TAPA, “Newman’s reagent” for the resolution of 1.1.

TAPA was then used for the resolution of [6] to [14]helicene racemates.5c Newman and Lednicer also reported the resolution of 1,12-dimethylbenzo[4]helicene-5-acetic acid 1.7 (scheme 1.1), by selective precipitation of diastereomeric salts formed by interaction of 1.7 with cinchonidine amine 1.20 (Figure 1.5).38b Later, Yamaguchi described an analogous method for the resolution of 1,12-dimethylbenzo[c]phenanthrene-5,8-dicarboxylic acid using enantiopure quinine 1.21.56 Others chiral reagents were also employed: Stary utilized O,O’- dibenzoyl-d-tartaric acid 1.22, Wang used brucine 1.23 and interestingly optical active molecules such as α-pinene 1.24 were applied as solvent for the resolution of [7]heterohelicenes.57

56 H. Okubo, M. Yamaguchi, C. Kabuto, J. Org. Chem. 1998, 66, 957. 57 a) W. H. Laarhoven, T. J. H. M. H. Cuppen, J. Chem. Soc., Perkin Trans. 2 1978, 315 b) W. H. Laarhoven, T. J. H. M. H. Cuppen, J. Chem. Soc., Chem. Commun. 1977, 47; c) Wynberg, M. B. Groen, J. Am. Chem. Soc. 1970, 92, 6664.

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Chapter 1: General Introduction

Figure 1.5: Other chiral reagents used for the optical resolution of helicenes.

However, with the development of (semi) preparative HPLC techniques, the direct separation of racemic helicenes became a reliable approach. Indeed, this strategy was first used by Mikes in 1976.58 This technique is one of the most important and in the beginning short silica gel column coated with optically active TAPA (10-25%) was prepared. Since the report of Mikes and co-workers, and thanks to high improvement of HPLC methods, a variety of chiral stationary phases have been created. However, despite the efficiency of these methods, CSP-procedures are still limited in view of the small amount of material that can be separated under standard conditions.

Therefore, the use of covalently bonded chiral auxiliaries to obtain chromatographically separable diastereomers is attractive and this method is nowadays the standard. For example, Katz has utilized (S)-camphanate 1.25 (Figure 1.6) as chiral resolving agent to afford optically pure helicene-quinone derivatives, after removal of the auxiliary.59 Noteworthy, the presence of the camphanate auxiliary was also useful in determining the relative and absolute configurations of the isolated diastereomic helicenes. As a general rule, the M helicene attached to the (1S)-camphanates eluted faster than the one bearing the P helicity.

58 F. Mikes, G. Boshart, E. Gilav, J. Chem. Soc., Chem. Commun. 1976, 99. 59 T. Thongpanchang, K. Paruch, T. J. Katz, A. L. Rheingold, K.-C. Lam, L. Liable-Sands, J. Org. Chem. 2000, 65, 1850.

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Chapter 1: General Introduction

Figure 1.6: Selected examples of helicene-like compounds resolved by introducing (1S)-camphanate moiety as chiral auxiliary.

Such a tendency was also described by Venkatamaran60 and Dötz.61 Later, Careño and Urbano utilized enantiopure (+)-(S)-2-(p-tolyl-sulfinyl)-1,4-benzoquinone 1.13 (Scheme 1.4) as a chiral auxiliary for the synthesis of enantioenriched heterohelicenes.45 Functionalized helicenes containing carboxylic acid and hydroxyl functional groups and heterohelicenes (thiaheterohelicenes) were resolved by covalently attached chiral auxiliaries like for instance camphanoyl chloride 1.26,62 camphorsultam 1.27,63 phenylacetyl chloride of type 1.2864 and menthol derivatives of type 1.2965respectively (Figure 1.7).

Figure 1.7: Other chiral auxiliaries used for helicenes resolution.

60 J. E. Field, G. Muller, J. P. Riehl, D. Venkataraman, J. Am. Chem. Soc. 2003, 125, 11808. 61 J. F. Schneider, M. Nieger, K. Naettinen, B. Lewall, E. Niecke, K. H. Doetz, Eur. J. Org. Chem. 2005, 1541 62 a) K. E. S. Phillips, T. J. Katz, S. Jockusch, Lovinger, J. A. N. J. Turro, J. Am. Chem. Soc. 2001, 123, 11899; b) S. D. Dreher, D. J. Weix, T. J. Katz, J. Org. Chem. 1999, 64, 3671; c) C. Nuckolls, T. J. Katz, G. Katz, P. J. Collings, L. Castellanos, J. Am. Chem. Soc. 1999, 121, 79; d) J. M. Fox, N. R. Goldberg, T. J. Katz, J. Org. Chem. 1998, 63, 7456. 63 H. Okubo, M. Yamaguchi, C. Kabuto, J. Org. Chem. 1998, 63, 9500 64 J. L. Cheung, L. D. Field, T. W. Hambley, S. Sternhell, J. Org.Chem. 1997, 62, 62. 65 A. Rajca, M. Miyasaka, M. Pink, H. Wang, S. Rajca, J. Am. Chem. Soc. 2004, 126, 15211.

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1.7 Applications of Carbohelicenes

Thanks to their screwed backbone, helicenes present a chiral geometry which gives rise to a variety of properties such as chiroptical ones66 and multiple applications have been reported in diverse areas like for instance self-assembly,67 asymmetric catalysis,68 supramolecular chemistry,69 molecular machines70 and material sciences.71

To enhance their efficiency in catalysis and widen their application, peripheral functionalization of helicene skeletons have also been explored,72 since the functionalization could account for many changes in their properties. Therefore introduction of hydroxy, amines, carboxylates or diphosphines groups have given access to applications in catalysis, molecular recognition73 and DNA interaction.74

So far, most of the helicenes discussed, were pure carbohelicenes and carbohelicenes functionalized at the peripheral, therefore they have properties different from the

66 a) S. Graule, M. Rudolph, N. Vanthuyne, J. Autschbach, C. Roussel, J. Crassous, R. Réau, J. Am. Chem. Soc. 2009, 131, 3183; b) W. T. Shen, S. Graule, J. Crassous, C. Lescop, H. Gornitzka, R. Reau, Chem. Commun. 2008, 850; c) B. Champagne, J.-M. Andre, E. Botek, E. Licandro, S. Maiorana, A. Bossi, K. Clays, A. Persoons, ChemPhysChem. 2004, 5, 1438; d) F. Lebon, G. Longhi, F. Gangemi, S. Abbate, J. Priess, M. Juza, C. Bazzini, T. Caronna, A. Mele, J. Phys. Chem. A 2004, 108, 11752; e) J. E. Field, G. Muller, J. P. Riehl, D. Venkataraman, J. Am. Chem. Soc. 2003, 125, 11808 f) C. Wachsmann, E. Weber, M. Czugler, W. Seichter, Eur. J. Org. Chem. 2003, 2863; g) T. Verbiest, S. Sioncke, A. Persoons, L. Vyklicky, T. J. Katz, Angew. Chem. Int. Ed. 2002, 41, 3882; h) T. B. Norsten, A. Peters, R. McDonald, M. T. Wang, N. R. Branda, J. Am. Chem. Soc.2001, 123, 7447 i) F. Furche, R. Ahlrichs, C. Wachsmann, E. Weber, A. Sobanski, F. Vögtle, S. Grimme, J. Am. Chem. Soc. 2000, 122, 1717 67 C. Nuckolls, T. J. Katz, Castellanos, L. J. Amer. Chem. Soc. 1996, 118, 3767; Dai, Y.; Katz, T. J. J. Org. Chem. 1997, 62, 1274-1285. Nuckolls, C.; Katz, T. J. J. Am. Chem. Soc. 1998, 120, 9541. 68 Reetz, M. T.; Beuttenmuller, E. W.; Goddard, R. Tetrahedron Lett. 1997, 38, 3211; Terfort, A.; Gorls, H.; Brunner, H. Synthesis 1997, 79-86. Reetz, M. T.; Sostmann, S. J. Organomet. Chem. 2000, 603, 105; Reetz, M. T.; Sostmann, S. Tetrahedron 2001, 57, 2515. 69 Murguly, E., R. McDonald, N.R. Branda, Org. Lett. 2000, 2, 3169; Kitahara, Y. and K. Tanaka, Chem. Commun 2002, 932; Tanaka, K., H. Osuga, and Y. Kitahara, J. Org. Chem. 2002, 67, 1795. 70 Kelly, T. R.; Cai, X.; Damkaci, F.; Panicker, S. B.; Tu, B.; Bushell, S. M.; Cornella, I.; Piggott, M. J.; Salives, R.; Cavero, M.; Zhao, Y.; Jasmin, S. J. Amer. Chem. Soc. 2006, 129, 376. 71 a) M. Miyasaka, A. Rajca, M. Pink, S. Rajca, J. Am. Chem. Soc. 2005, 127, 13806; b) M. T. Stone, J. M. Fox, J. S. Moore, in Org. Lett. 2004, 6, 3317; c) M. Miyasaka, A. Rajca, M. Pink, S. Rajca, Chem. Eur. J. 2004, 10, 6531; d) T.J Katz,. Angew. Chem. Int. Ed. 2000, 39, 1921; e) J. M. Fox, D. Lin, Y. Itakagi, T. Fujita, ibid.1998, 63, 2031; f) Y. J. Dai, T. J. Katz, J. Org. Chem. 1997, 62, 1274. 72 a) K. Paruch, L. Vyklicky, D. Z. Wang, T. J. Katz, C. Incarvito, L. Zakharov, A. L. Rheingold, J. Org. Chem. 2003, 68, 8539-8544; b)S. D. Dreher, K. Paruch, T. J. Katz, J. Org. Chem. 2000, 65, 806; c) J. M. Fox, N. R. Goldberg, T. J. Katz, J. Org. Chem. 1998, 63, 7456. 73 a) D. Z. Wang, T. J. Katz, J. Org. Chem. 2005, 70, 8497; b) M. T. Reetz, S. Sostmann, Tetrahedron 2001, 57, 2515;c) E. Murguly, R. McDonald, N. R. Branda, Org. Lett. 2000, 2, 3169; d) L. Owens, C. Thilgen, F. Diederich, C. B. Knobler, Helv. Chim. Acta 1993, 76, 2757. 74 a) Y. Xu, Y. X. Zhang, H. Sugiyama, T. Umano, H. Osuga, K. Tanaka, J. Am. Chem. Soc. 2004, 126, 6566; b) S. Honzawa, H. Okubo, S. Anzai, M. Yamaguchi, K. Tsumoto, I. Kumagai, Bioorg. Med. Chem. 2002, 10, 3213.

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heterohelicenes, where heteroatom(s) are included in the helical frame and in particular azahelicenes. Thus, emphasis will be first made on the synthesis and properties of these latter derivatives and finally on a special class of azahelicenes which are cationic diazahelicenes and quinacridinium salts in particular.

1.8 Synthesis of Azahelicenes

Azahelicenes are helical derivatives made of ortho fused aromatic rings containing at least one sp2-hybridized nitrogen atom.75 Like their carbon analogues, they possess distinctive twisted conformations that result from steric repulsions between the terminal aromatic rings or their substituents. These moieties have more recently caught the attention of the scientific community76 and have been therefore utilized for a variety of applications due to the combined presence of an inherently chiral geometry and of nitrogen donor atom(s). In fact, studies have been reported in many different fields, such as solid state self–assembly,77 asymmetric catalysis,78 chemosensors79 and enantioselective biomolecular recognition.10 Their synthesis is mostly based on three different approaches. The first method relies on photocyclization like their carbon analogues (Scheme 1.7). For example, [5]helicene of type 1.32 are prepared from good to excellent yields after a sequence of photoisomerization and

75 a) J. Bosson, J. Gouin, J. Lacour, Chem. Soc. Rev. 2014, 43, 2824; b) F. Dumitrascu, D. G. Dumitrescu, I. Aron, ARKIVOC 2010, 1. 76 Sato, K.; Arai, S. Heterohelicenes Containing Nitrogen Aromatics: Azahelicenes and Azoniahelicenes In Cyclophane Chemistry for the 21st Century Takemura, H., Ed., Research Signpost: Kerena, India, 2002, 173 77 a) T. Kaseyama, S. Furumi, X. Zhang, K. Tanaka, M. Takeuchi, Angew. Chem. Int. Ed. 2011, 50, 3684; b) S. Graule, M. Rudolph, W. Shen, J. A. G. Williams, C. Lescop, J. Autschbach, J. Crassous, R. Réau, Chem. Eur. J. 2010, 16, 5976; c) I. Alkorta, F. Blanco, J. Elguero, D. Schroeder, Tetrahedron-Asymmetry 2010, 21, 962; d) M. A. Shcherbina, X.-b. Zeng, T. Tadjiev, G. Ungar, S. H. Eichhorn, K. E. S. Phillips, T. J. Katz, Angew. Chem. Int. Ed. 2009, 48, 7837; e) S. b. Graule, M. Rudolph, N. Vanthuyne, J. Autschbach, C. Roussel, J. Crassous, R. Réau, J. Am. Chem. Soc. 2009, 131, 3183; f) W. Shen, S. Graule, J. Crassous, C. Lescop, H. Gornitzka, R. Reau, Chem. Commun. 2008, 850; g) C. Bazzini, T. Caronna, F. Fontana, P. Macchi, A. Mele, I. Natali Sora, W. Panzeri, A. Sironi, New J. Chem. 2008, 32, 1710; h) T. J. Katz, Angew. Chem. Int. Ed. 2000, 39, 1921, i) E. Murguly, R. McDonald, N. R. Branda, Org. Lett. 2000, 2, 3169; h) J. Howarth, J. Finnegan, Synth. Commun. 1997, 27, 3663. 78 a) L. Kötzner, M. J. Webber, A. Martínez, C. De Fusco, B. List, Angew. Chem. Int. Ed. 2014, 53, 5202; b) Takenaka, N.; Chen, J.; Captain, B.; Sarangthem, R. S.; Chandrakumar, A. J. Am. Chem. Soc. 2010, 132, 4536; c) J. Chen, N. Takenaka, Chem. Eur. J. 2009, 15, 7268; d) N. Takenaka, R. S. Sarangthem, B. Captain, Angew. Chem. Int. Ed. 2008, 47, 9708. 79 a) T. Caronna, F. Castiglione, A. Famulari, F. Fontana, L. Malpezzi, A. Mele, D. Mendola, I. N. Sora, Molecules 2012, 17, 463; b) R. Hassey, E. J. Swain, N. I. Hammer, D. Venkataraman, M. D. Barnes, Science 2006, 314, 1437.

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cyclization, starting from the readily accessible precursor 1.30. The position of the nitrogen was varied in the end target by modifying the precursor 1.30.80

Scheme 1.7: Photochemical approach to diverse mono and diaza derivatives 1.32.

The second method is based on transition-metal catalyzed cyclotrimerization. This interesting approach was pioneered by Starý and co-workers.81 Especially, a Cobalt complex catalyzes the [2+2+2] cycloisomerization in the formation of the azahelicenes ([5] and [6]) of type 1.34 from triyne precursor 1.33. An efficient enantioselective version of this methodology was recently reported by the same author using Nickel catalyst and chiral binaphthyl ligands to access dibenzohelicenes in good and good enantiomeric excesses.82

80 a) F. Aloui, R. E. Abed, A. Marinetti, B. B. Hassine, Tetrahedron Lett. 2008, 49, 4092; b) F. Aloui, R. E. Abed, B. B. Hassine, Tetrahedron Lett. 2008, 49, 1455; c) S. Abbate, T. Caronna, A. Longo, A. Ruggirello, V. T. Liveri, J. Phys. Chem. B 2007, 111, 4089; d) S. Abbate, C. Bazzini, T. Caronna, F. Fontana, C. Gambarotti, F. Gangemi, G. Longhi, A. Mele, I. N. Sora, W. Panzeri, Tetrahedron 2006, 62, 139; e) C. Bazzini, S. Brovelli, T. Caronna, C. Gambarotti, M. Giannone, P. Macchi, F. Meinardi, A. Mele, W. Panzeri, F. Recupero, A. Sironi, R. Tubino, Eur. J. Org. Chem. 2005, 1247; f) K. Sato, T. Yamagishi, S. Arai, J. Heterocycl. Chem. 2000, 37, 1009; g) E. Murguly, R. McDonald, N. R. Branda, Org. Lett. 2000, 2, 3169; h) J. Howarth, J. Finnegan, Synth. Commun. 1997, 27, 3663; i) S. Arai, M. Ishikura, K. Sato, T. Yamagishi, J. Heterocycl. Chem. 1995, 32, 1081; j) M. Rentzea, M. Diehm, H. A. Staab, Tetrahedron Lett. 1994, 35, 8361. 81 a) J. Storch, J. Čermák, J. Karban, I. Císařová, J. Sýkora, J. Org. Chem. 2010, 75, 3137; b) O. Songis, J. Míšek, M. B. Schmid, A. Kollárovič, I. G. Stará, D. Šaman, I. Císařová, I. Starý, J. Org. Chem. 2010, 75, 6889; c) J. Misek, F. Teply, I. G. Stara, M. Tichy, D. Saman, I. Cisarova, P. Vojtisek, I. Stary, Angew. Chem. Int. Ed. 2008, 47, 3188; d) I. G. Stará, I. Starý, A. Kollárovič, F. Teplý, D. Šaman, M. Tichý, J. Org. Chem. 1998, 63, 4046 82 A. Jančařík, J. Rybáček, K. Cocq, J. Vacek Chocholoušová, J. Vacek, R. Pohl, L. Bednárová, P. Fiedler, I. Císařová, I. G. Stará, I. Starý, Angew. Chem. Int. Ed. 2013, 52, 9970

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Scheme 1.8: [2+2+2] cycloisomerisation to form aza[6]helicene 1.34.

The third protocol takes advantageous of the impressive growth and powerful technology of cross-coupling reactions catalyzed by transition-metal.83 For instance, azahelicene 1.37 is synthesized in three steps after cross coupling reaction between 1.34 and

1.35 catalyzed by CuI and cyclization by PtCl4. The cross coupling step affords a mixture of products 1.36 which is directly use in the next step without purification.

Scheme 1.9: Transition metal catalyzed synthesis of [6]azahelicene 1.37.

A Cross-coupling approach was also employed for the preparation of completely different type of azahelicene by the group of Venkatamaran.84 This latter was inspired by the

83 a) M. Weimar, d. C. R. Correa, F.-H. Lee, M. J. Fuchter, Org. Lett. 2013, 15, 1706; b) W. Lin, G.-L. Dou, M.- H. Hu, C.-P. Cao, Z.-B. Huang, D.-Q. Shi, Org. Lett. 2013, 15, 1238; c) E. Kaneko, Y. Matsumoto, K. Kamikawa, Chem. Eur. J. 2013, 11837; d) D. Waghray, J. Zhang, J. Jacobs, W. Nulens, N. Basarić, L. V. Meervelt, W. Dehaen, J. Org. Chem. 2012, 77, 10176; e) H. R. Talele, S. Sahoo, A. V. Bedekar, Org. Lett. 2012, 14, 3166; f) H. Kelgtermans, L. Dobrzanska, L. Van Meervelt, W. Dehaen, Org. Lett. 2012, 14, 1500; g) O. Crespo, B. Eguillor, M. A. Esteruelas, I. Fernandez, J. Garcia-Raboso, M. Gomez-Gallego, M. Martin-Ortiz, M. Olivan, M. A. Sierra, Chem. Commun. 2012, 48, 5328; h) M. R. Crittall, H. S. Rzepa, D. R. Carbery, Org. Lett. 2011, 13, 1250; i) N. Takenaka, R. S. Sarangthem, B. Captain, Angew. Chem. Int. Ed. 2008, 47, 9708. 84 a) R. Hassey, E. J. Swain, N. I. Hammer, D. Venkataraman, M. D. Barnes, Science 2006, 314, 1437; b).J. E. Field, G. Muller, J. P. Riehl, D. Venkataraman, J. Am. Chem. Soc. 2003, 125, 11808; c) J. E. Field, T. J. Hill, D. Venkataraman, J. Org. Chem. 2003, 68, 6071.

16

Chapter 1: General Introduction

work of Hellwinkel for the synthesis of non-functionalized bridged triarylamine.85 Product

1.41 was obtained after a sequence of Ullmann coupling/cyclization with SnCl4 (scheme 1.10). These conditions were carefully chosen to avoid chlorination of the helicene core.84c Moreover, the central nitrogen atom could be oxidized to a radical cation without any evidence of dimerization, which could be expected if the radical form is not stable enough in solution to exist as such. Such a theory was confirmed by cyclic voltammetry studies which showed a quasi-reversible one-electron oxidation of the heterohelicenes.84c

Scheme 1.10: Synthesis of helicene-like molecules 1.41 by the method of Venkatamaran; a) Cu or CuI, K2CO3,

Ph2O or nBu2O,150-190 °C, 2-5 days; b) NaOH, H2O/EtOH (1:1), reflux for 1-3 days then HCl; c) (COCl)2,

CH2Cl2, reflux for 0.5 h then SnCl4, reflux for 2-3 h.

Finally, the group of List reported recently the first organocatalytic synthesis of heterohelicenes using chiral phosphoric acids to promote the Fisher indolization (Scheme 1.11).86 Starting from protected 3,5-dimethylphenylhydrazine and polycyclic ketone, they were able to get excellent enantiomeric ratio up to 96:4 with 98% yield

Scheme 1.11: Enantioselective organocatalytic synthesis of aza[6]helicene.

85 a) D. Hellwinkel, W. Schmidt, Chem. Ber. 1980, 113, 358; b) D. Hellwinkel, M. Melan Chem. Ber. 1971, 104, 1001; 86 L. Kötzner, M. J. Webber, A. Martínez, C. De Fusco, B. List, Angew. Chem. Int. Ed. 2014, 5202.

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Chapter 1: General Introduction

1.9 Applications of Azahelicenes

Currently, azahelicenes are applied in solid state self–assembly,87 asymmetric catalysis,88 chemosensors,89 material sciences,90 molecular machines,91 Biochemistry92 and chiral luminescence.84a,b,93 Among this latter application, circularly polarized luminescence (CPL) which is the differential emission of right-circularly polarized light versus left- circularly polarized light by chiral molecular systems has attracted a lot of attention during the two last decades and several studies dealing with chiral lanthanide complexes have been reported.94 However there has been a growing interest in developing organic molecules that

87 a) T. Kaseyama, S. Furumi, X. Zhang, K. Tanaka, M. Takeuchi, Angew. Chem. Int. Ed. 2011, 50, 3684; b) S. Graule, M. Rudolph, W. Shen, J. A. G. Williams, C. Lescop, J. Autschbach, J. Crassous, R. Réau, Chem. Eur. J. 2010, 16, 5976; c) I. Alkorta, F. Blanco, J. Elguero, D. Schroeder, Tetrahedron-Asymmetry 2010, 21, 962; d) M. A. Shcherbina, X.-b. Zeng, T. Tadjiev, G. Ungar, S. H. Eichhorn, K. E. S. Phillips, T. J. Katz, Angew. Chem. Int. Ed. 2009, 48, 7837; e) S. b. Graule, M. Rudolph, N. Vanthuyne, J. Autschbach, C. Roussel, J. Crassous, R. Réau, J. Am. Chem. Soc. 2009, 131, 3183; f) W. Shen, S. Graule, J. Crassous, C. Lescop, H. Gornitzka, R. Reau, Chem. Commun. 2008, 0, 850; g) C. Bazzini, T. Caronna, F. Fontana, P. Macchi, A. Mele, I. Natali Sora, W. Panzeri, A. Sironi, New J. Chem. 2008, 32, 1710; h) E. Murguly, R. McDonald, N. R. Branda, Org. Lett. 2000, 2, 3169; i) T. J. Katz, Angew. Chem. Int. Ed. 2000, 39, 1921. 88 a) P. Aillard, A. Voituriez, A. Marinetti, DaltonTrans. 2014, 43, 15263; b) N. Takenaka, J. S. Chen, B. Captain, R. S. Sarangthem, A. Chandrakumar, J. Am. Chem. Soc. 2010, 132, 4536; c) J. S. Chen, N. Takenaka, Chem. Eur. J. 2009, 15, 7268; d) T. Kawasaki, K. Suzuki, E. Licandro, A. Bossi, S. Maiorana, K. Soai, Tetrahedron: Asymmetry 2006, 17, 2050; e) D. Nakano, M. Yamaguchi, Tetrahedron Lett. 2003, 44, 4969; f) I. Sato, R. Yamashima, K. Kadowaki, J. Yamamoto, T. Shibata, K. Soai, Angew. Chem., Int. Ed. 2001, 40, 1096; g) S. D. Dreher, T. J. Katz, K. C. Lam, A. L. Rheingold,. J. Org. Chem. 2001, 65, 815; h) Reetz, M. T.; Sostmann, S. J. Organomet. Chem. 2000, 603, 105; i) S. D. Dreher, T. J. Katz, K. C. Lam, A. L. Rheingold, J. Org. Chem. 2000, 65, 815; j) H. Okubo, M. Yamaguchi, C. J. Kabuto, Org. Chem. 1998, 66, 957; k) M. T. Reetz, E. W. Beuttenmuller, R. Goddard, Tetrahedron Lett. 1997, 38, 3211; l) A. Terfort, H. Gorls, H. Brunner Synthesis 1997, 79; 89 a) T. Caronna, F. Castiglione, A. Famulari, F. Fontana, L. Malpezzi, A. Mele, D. Mendola, I. N. Sora, Molecules 2012, 17, 463; b) R. Hassey, E. J. Swain, N. I. Hammer, D. Venkataraman, M. D. Barnes, Science 2006, 314, 1437; c) M. T. Reetz, S. Sostmann, Tetrahedron 2001, 57, 2515. 90 a) Y. J. Dai, T. J. Katz, J. Org. Chem. 1997, 62, 1274; b) J. M. Fox, D. Lin, Y. Itakagi, T. Fujita, ibid.1998, 63, 2031; c) M. T. Stone, J. M. Fox, J. S. Moore, in Org. Lett. 2004, 6, 3317; d) M. Miyasaka, A. Rajca, M. Pink, S. Rajca, Chem. Eur. J. 2004, 10, 6531; e) M. Miyasaka, A. Rajca, M. Pink, S. Rajca, J. Am. Chem. Soc. 2005, 127, 13806. 91 T. R. Kelly, X. Cai, F. Damkaci, S. B. Panicker, , B. Tu, , S. M. Bushell, I. Cornella, M. J. Piggott, R. Salives, M. Cavero, Y. Zhao, S. Jasmin, J. Amer. Chem. Soc. 2006, 129, 376. 92 a) Y. Xu, Y. X. Zhang, H. Sugiyama, T. Umano, H. Osuga, K. Tanaka, J. Am. Chem. Soc. 2004, 126, 6566; b) S. Honzawa, H. Okubo, S. Anzai, M. Yamaguchi, K. Tsumoto, I. Kumagai, Bioorg. Med. Chem. 2002, 10, 3213. 93 S. Graule, M. Rudolph, N. Vanthuyne, J. Autschbach, C. Roussel, J. Crassous, R. Réau, J. Am. Chem. Soc. 2009, 131, 3183 94 J. P. Riehl, F. S. Richardson, Chem. Rev. 1986, 86, 1.

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Chapter 1: General Introduction

are capable of emitting circularly polarized light such as heterohelicenes,84a,b,95 due to their potential applications in display devices,96 optical storage devices,97 and asymmetric photochemical synthesis.98 This property will be discuss in chapter V as new fluorophores such as pH-switchable [4]helicenes, chiral BODIPY-like and azobenzenes were developed during this PhD.

Finally, besides these classes of derivatives in which the nitrogen atom is positioned at the center or in the lumen of the helicenes, there are compounds for which the nitrogen atoms are located at the outer rim of the twisted scaffold.

1.10 Highly Stable Cationic Aza[4] and [6]Helicenes

+ Recently, thanks to the pioneer work of Laursen and Krebs, several highly stable (pKR value varying from 11 to 24) aza-bridged heterocyclic carbenium ions (1.42 to 1.44) have been reported (Figure 1.8).99

Figure 1.8. Highly stable heterocyclic carbenium ions 1.42 to 1.44 (R = n-alkyl).

95 a) N. Saleh, B. Moore II, M. Srebo, N. Vanthuyne, L. Toupet, J. A. G. Williams, C. Roussel, K. K. Deol, G. Muller, J. Autschbach, J. Crassous, Chem. Eur. J. 2015, 21, 1673 b) H. Maeda, Y. Bando, Pure Appl. Chem. 2013, 85, 1967; 96 a) P. Dyreklev, M. Berggren, O. Inganas, M. R. Andersson, O. Wennerstrom, T. Hjertberg, Adv. Mater. 1995, 7, 43; b) M. Grell, D. C. Bradley, Adv. Mater. 1999, 11, 895; c) M. Grell, M. Oda, K. S. Whitehead, A. Asimakis, D. Neher, D. D. C. Bradley, Adv. Mater. 2001, 13, 577 97 S. H. Chen, D. Katsis, A. W. Schmid, J. C. Mastrangelo, T. Tsutsui, T. N. Blanton, Nature 1999, 397, 506 98 a) R. D. Richardson, M. G. J. Baud, C. E. Weston, H S. Rzepa, M. K. Kuimova, M. J. Fuchter, Chem. Sci. 2015, 6, 3853; b) I. Sato, R. Yamashima, K. Kadowaki, J. Yamamoto, T. Shibata, K. Soai, Angew. Chem., Int. Ed. 2001, 40, 1096; c) B. L. Feringa, R. A. van Delden, Angew. Chem., Int. Ed. 1999, 38, 3418; d) L. D. Barron, J. Am. Chem. Soc. 1986, 108, 5539; e) H. B. Kagan, G. Balavoine, A. Moradpour, J. Mol. Evol. 1974, 4, 41; 99 a) B. Laleu, P. Mobian, C. Herse, B. W. Laursen, G. Hopfgartner, G. Bernardinelli, J. Lacour, Angew. Chem., Int. Ed. 2005, 44, 1879; b) C. Herse, D. Bas, F. C. Krebs, T. Buergi, J. Weber, T. Wesolowski, B. W. Laursen, J. Lacour, Angew. Chem., Int. Ed. 2003, 42, 3162. c) B. W. Laursen, F. C. Krebs, Chem. Eur. J., 2001, 7, 1773; d) Laursen, B. W. Ph. D. Thesis, Univ. Copenhagen 2001, RisØ-R-1275; e) B. W. Laursen, F. C. Krebs, Angew. Chem., Int. Ed. 2000, 39, 3432; f) B. W. Laursen, F. C. Krebs, M. F. Nielsen, K. Bechgaard, J. B. Christensen, N. Harrit, J. Am. Chem. Soc. 1999, 121, 4728; g) B. W. Laursen, F. C. Krebs, M. F. Nielsen, K. Bechgaard, J. B. Christensen, N. Harrit, J. Am. Chem. Soc. 1998, 120, 12255.

19

Chapter 1: General Introduction

+ The stability of a carbenium ion is generally defined by its pKR value, which expresses the affinity of the cation towards hydroxide anion. This value is defined by the equilibrium between the cationic ion and its corresponding carbinol as shown equation 1.1. This thermodynamic parameter depends on several non-intrinsic contributions such as the carbinol stability.99c,d The conversion of the carbocation into the corresponding carbinol is + usually monitored using UV-Vis spectrometry. The pKR values of several carbeniums have been reported and they span from 6 to 24 for dioxa[4]helicenium (vide infra) to triazatriangulenium 1.44. As it could be expected, the more nitrogen atoms present within the core (helicenium and triangulenium) or as peripheral substituents, the higher the stability of + the resulting carbenium ions and their pKR values.

+ Equation 1.1: Definition of pKR .

+ + For the “least stable” derivatives (pKR <14), the pKR values are calculated by direct 100 + measurement of the equilibrium constant KR in water. Otherwise (pKR >14), measurements cannot be performed in pure aqueous solutions and special experimental conditions are required. Typical studies performed in a DMSO/water/Me4NOH solvent system, the DMSO:water ratio controlling the strength of the hydroxide ions and the basicity of the 99d medium which is quantified via an acidity function HX.

These polycyclic moieties (Figure 1.8) display also other interesting chemical and (photo) physical properties.101 These compounds have been studied as attractive synthetic targets for the development of novel and original synthetic,102 asymmetric,103 photochemical,104 topological105 and biological applications.106 Appropriately, all these

100 N. Mathivanan, R. A. McClelland, S. Steenken, J. Am. Chem. Soc. 1990, 112, 8454 101 a) J. Hamaceck, C. Besnard, N. Mehanna, J. Lacour, Dalton Trans. 2012, 41, 6777; b) O. Kel, P. Sherin, N. Mehanna, B. Laleu, J. Lacour, E. Vauthey, Photochem. Photobiol. Sci. 2012, 11, 623 102 a) J. Guin, C. Besnard, P. Pattison, J. Lacour, Chem. Sci. 2011, 2, 425; b) D. Conreaux, N. Mehanna, C. Herse, J. Org. Chem., 2011, 76, 2716; c) Nicolas, C.; Lacour, J. Org. Lett. 2006, 8, 4343; d) B. Laleu, M. S. Machado, J. Lacour, Chem. Commun. 2006, 2786; e) B. Laleu, P. Mobian, C. Herse, B. W. Laursen, G. Hopfgartner, G. Bernardinelli, J. Lacour, Angew. Chem., Int. Ed. 2005, 44, 1879; f) B. Laleu, C. Herse, B. W. Laursen, G. Bernardinelli, J. Lacour, J. Org. Chem. 2003, 68, 6304; g) C. Herse, D. Bas, F. C. Krebs, T. Buergi, J. Weber, T. Wesolowski, B. W. Laursen, J. Lacour, Angew. Chem., Int. Ed. 2003, 42, 3162 103 C. Villani, B. Laleu, P. Mobian, J. Lacour, Chirality 2007, 19, 601. 104 C. Nicolas, C. Herse, J. Lacour, Tetrahedron Lett. 2005, 46, 4605.

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Chapter 1: General Introduction

derivatives (1.42 to 1.44) are easily prepared from a single chemical precursor that is the tris(2,6-dimethoxybenzene) methylium ion 1.45 (Scheme 1.12).107 Consecutive nucleophilic aromatic substitution (SNAr) of the methoxy groups of 1.45 by primary amines affords efficiently and successively 1.42, 1.43 and 1.44 depending on the reaction conditions. In fact, each introduction of a nitrogen bridge is more difficult than the previous one. It is therefore possible to obtain selectively the different products in which two, four, or six of the ortho- methoxy groups of 1.45 are substituted by a nitrogen atom.99c,d,e

In term of synthesis, the reaction at room temperature (20 °C) of the readily available 1.45 with alkylamines in slight excess (2.5 equiv.) and NMP as polar solvent give tetramethoxyphenylacridinium salts 1.42 (TMPA+) in excellent yields after 20 hours (70- 90%). For the formation of the double nitrogen bridged dimethoxyquinacridinium (DMQA+) 1.43 the reactions proceed also in NMP, but much faster (~ 1 hour) at elevated temperatures (80-110 °C) with a large excess of amines (25 equiv.). The DMQA+ cations (1.43) are usually obtained in moderate to good yields (50 to 80%).99c The triply nitrogen-bridged triazatriangulenium (TATA+) salts 1.44 require even higher temperatures and longer reaction times and are formed after heating to 130-190 °C. In this case, reactions cannot be achieved with low boiling point amines except with the addition of benzoic acid to the reaction mixture allowing the reflux temperature to be raised.99e Finally, partially bridged 1.43 can be converted into another fully ring-closed derivative, this time with an oxygen bridge instead of nitrogen. The diazaoxa-triangulenium salts (DAOTA+, 1.48) are obtained by intramolecular ring closure upon heating with molten PyrH+Cl- (~ 170 °C) as solvent or LiI as reagent ( Scheme 1.12).

105 a) Baisch, B.; Raffa, D.; Jung, U.; Magnussen, O. M.; Nicolas, C.; Lacour, J.; Kubitschke, J.; Herges, R. J. Am. Chem. Soc. 2009, 131, 442; b) Mobian, P.; Nicolas, C.; Francotte, E.; Bürgi, T.; Lacour, J. J. Am. Chem. Soc. 2008, 130, 6507; c) Mobian, P.; Banerji, N.; Bernardinelli, G.; Lacour, J. Org. Biomol. Chem. 2006, 4, 224. 106 O. Kel, A. Fürstenberg, N. Mehanna, C. Nicolas, B. Laleu, M. Hammarson, B. Albinson, J. Lacour, E. Vauthey, Chem. Eur. J. 2013, 19, 7173 107 J. C. Martin, R. G. Smith, J. Am. Chem. Soc. 1964, 86, 2252.

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Chapter 1: General Introduction

1 Scheme 1.12: Stepwise synthesis of highly stable aza- and oxa-bridged heterocyclic carbenium ions: a) R NH2, 2 3 NMP, 25 °C, 20 h; b) R NH2, NMP, 110 °C, 1h; c) R NH2, NMP, 190 °C, 10-24 h; d) LiI, NMP, 190 °C or PyrH+Cl-, 190 °C, 1h.

Each step introducing a new nitrogen atom constantly decreases the reactivity of the associated products. This is mainly due, on one hand, to the increased planarity of these structures that facilitates electron resonance delocalization of the central charge and also because nitrogen atoms are much better electron-donating groups than oxygen atoms thus stabilizing more and more the central electron poor carbon. The structural modifications due to the introduction of the aza-bridges induce a lowering of the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecules which thus have two consequences. This is the main reason of carbenium ions photophysical properties.99a

Indeed, these molecules (1.42 to 1.48) are dyes, ranging from red orange (1.42), green (1.43) to pink (1.44 and 1.48). Products 1.43 to 1.48 are also highly fluorescent (fluorescence quantum yield ΦF up to 46% in MeCN) in the red and near infrared domain of light when submitted to UV/Vis light. This latter property will be extensively used in the course of this Ph.D (Chapters III and V). The introduction of nitrogen atoms renders the associated products more electron rich and readily oxidable. Clearly, the more nitrogen atoms present in the core

22

Chapter 1: General Introduction

(or as substituent) the easier the oxidation of the corresponding carbenium ion as shown by Figure 1.9.108

In fact, the reduction ability of the compound is tremendously diminished going from triply oxygen-bridged TOTA+ (1.46) to triply nitrogen-bridged nitrogen TATA+ (1.44). Therefore, it is noteworthy that owing to its stepwise and irreversible nature, this process provides a powerful tool for the synthesis of a large variety of dyes which can be accessible by simple structural variations of the nitrogen residues.

Figure 1.9: Oxidation and reduction potential of some stable carbenium ions.

Taking advantage of the high modularity and reactivity of these carbenium ions, an oxidative coupling was achieved between carbenium ion 1.45 and π- electron rich nucleophiles such as anilines and indoles. In fact, 1.45 acts as electrophile and oxidant in this spontaneous process leading to π-conjugated chromophores 1.49 with strong hyper and bathochromism (Figure 1.10.). However, compound 1.49 was obtained in low yields < 50%, therefore commercially available triarylmethane chloride derivatives was used as external oxidant, improving strongly hence the yield of 1.49.109

Figure 1.10: Oxidative coupling of carbenium ion 1.45 and indoles.

108 a) T. J. Sørensen, M. F. Nielsen, B. W. Laursen, ChemPlusChem 2014, 79, 1030; b) S. Dileesh, K. R. Gopidas, J. Photochem. Photobiol. A: Chem. 2004, 162, 115 109 R. Vanel, F. Miannay, E. Vauthey, J. Lacour Chem. Commun., 2014, 50, 12169

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Chapter 1: General Introduction

The Lacour’s group became also highly interested in the particular family of quinacridinium ions or DMQA+ 1.43 (Figure 1.11) for their attractively helical chirality and interesting photophysical properties. In fact, due to a strong steric repulsion between the MeO substituents (at positions 1 and 13), these compounds display a helical conformation which was confirmed by the X-ray diffraction analysis of the tetra phenyl borate salt of 5,9-di-n- propyl-1,13-dimethoxyquinacridinium cation and a very slow interconversion between the two helical forms was noticed. Two strategies were therefore developed by the group for the resolution and the study of these cationic derivatives. The first rely on crystallization method already presented (vide infra) using an NMR chiral solvating reagent namely BINPHAT 1.50 previously reported (Figure 1.11).110 This chiral anion forms diastereomic salts with the cationic helicenes, which differentially cristallize allowing the separation of these ion pairs.

After anion metathesis with persistence PF6, the salts of quinacridinium 1.43 was obtained with excellent enantiomeric ratio (>49:1).111 However the moderate yields at the precipitation stage along with the limited range of this method prompted the group to find a more effective resolution process. (+)-(R)-methyl-p-tolylsulfoxide 1.51112 was selected as chiral auxiliary and was put to react in the presence of a strong base with DMQA+ 1.43 to give chromatographically separable diastereomers (Scheme 1.13). The resolution affords each enantiomer with excellent ee values >98% after an unprecedented Pummerer fragmentation owing to the high electrofugal ability of DMQA+ 1.43.113

110 a) C. Pasquini, V. Desvergnes-Breuil, J. J. Jodry, A. Dalla Cort, J. Lacour, Tetrahedron Lett. 2002, 43, 423; b) J. Lacour, L. Vial, C. Herse, Org. Lett. 2002, 4, 1351; c) L. Vial, J Lacour, Org. Lett. 2002, 4, 3939; d) L. Pasquato, C. Herse, J. Lacour, Tetrahedron Lett. 2002, 43, 5517; e) J. Lacour, A. Londez, C. Goujon-Ginglinger, V. Buss, G.Bernardinelli, Org. Lett. 2000, 2, 4185. 111 C. Herse, D. Bas, F. C. Krebs, T. Buergi, J. Weber, T. Wesolowski, B. W. Laursen, J. Lacour, b) Angew. Chem., Int. Ed..2003, 42, 3162. 112 G. Solladié, Synthesis 1981, 185 113 B. Laleu, P. Mobian, C. Herse, B. W. Laursen, G. Hopfgartner, G. Bernardinelli, J. Lacour, Angew. Chem., Int. Ed. 2005, 44, 1879

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Chapter 1: General Introduction

Scheme 1.13: synthesis of M and P 1.43; a) (+)-(R)-1.51, LDA, THF, 0 °C, 1:1 mixture of diastereomers; b) column chromatography (SiO2); c) aq HPF6, acetone. Tol = Tolyl.

A racemization barrier of ca. 40 kcal.mol-1 was determined for 1.43 at 200 °C which is among the highest for helicenes (vide supra, § 1.5). This molecule is therefore part of the few [4]helicene-like molecules that were proven to be configurationally stable as the ones shown in Figure 1.11.38b,114,115,84b

Figure 1.11: Configurationally stable [4]helicenes, DMQA+ 1.43, (P enantiomers arbitrarily depicted) and resolving agent used for their resolution.

114 a) Y. Saiki, H. Sugiura, K. Nakamura, M. Yamaguchi, T. Hoshi, J. Anzai, J. Am. Chem. Soc. 2003, 125, 9268; b) Y. Saiki, K. Nakamura, Y. Nigorikawa, M. Yamaguchi, Angew. Chem., Int. Ed. 2003, 42, 5190. 115 M. C. Carreno, S. Garcia-Cerrada, M. J. Sanz-Cuesta, A. Urbano, J. Org. Chem. 2003, 68, 4315.

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Chapter 1: General Introduction

The group has also undertaken the challenging synthesis and study of some unknown cationic [4]helicenes such as the dioxa 1.52, azaoxa 1.53 and the azathia 1.54 analogues of DMQA+ 1.43 (Figure 1.12).116 In short these derivatives exhibit lower racemization barrier compare to cation 1.43. For instance dioxa 1.52 and azaoxa 1.53 show racemization values of 27.7 and 33.3 kcal.mol-1 at 20 and 160 °C respectively. These values reveal that nitrogen atoms have a significant influence on the racemization process, probably owing to the intrinsic rigidity of bridge nitrogen atoms 117 and their higher electron-donating ability compare to oxygens.

Figure 1.12: dioxa, azaoxa and thiaza derivatives 1.52, 1.53 and 1.54 respectively, P enantiomers arbitrarily depicted.

Finally, a new family of cationic dioxa-, azaoxa- and diaza[6]helicenes, compounds 1.55, 1.56 and 1.57 respectively, were also recently disclosed.118 Conveniently, all these compounds were prepared from a common identical advanced intermediate 1.58 (Scheme 1.14). This latter was obtained in five steps (59% overall yield, on 10 g scale) from commercially available materials. Rapid treatment of 1.58 in molten pyridinium hydrochloride afforded 1.55 in 95% yield. The azaoxa compound 1.56 was obtained in a two steps sequence (40% overall yield). First, 1.58 was reacted with a primary amine at 50 °C followed, after evaporation of the excess of amine, by a thermal treatment at 200 °C. Finally, treatment of 1.56 with a large excess of RNH2 (25 equiv, NMP, 170 °C, 5 min, µW) afforded the diaza[6]helicenes 1.57 (40-50% yield).

116 J. Guin, C. Besnard, J. Lacour, Org. Lett. 2010, 12, 1748. C. Nicolas, G. Bernardinelli, J. Lacour, J. Phys. Org. Chem. 2010, 23, 1049. 117 G. Pieters, A. Gaucher, S. Marque, F. Maurel, P. Lesot, D. Prim, J. Org. Chem. 2010, 75, 2096. 118 F. Torricelli, J. Bosson, C. Besnard, M. Chekini, T. Bürgi, J. Lacour, Angew. Chem. Int. Ed. 2013, 52, 1796.

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Chapter 1: General Introduction

Scheme 1.14: Synthesis of [6]helicenes derivatives. a) PyrHCl, 224 °C, 2 min; b) RNH2, 50 °C, 30 min, then neat 200 °C, 5 min; c) RNH2, NMP, 170 °C (µW), 5 min.

Interestingly, and quite unusually, regioselective post-functionalization of helicenes of type 1.57 was possible, which was not reported in the [4]helicene chemistry. Nevertheless, in chapter IV we will see that functionalization of diaza[4]helicenes was disclosed during this PhD and new type of luminophores created. Diaza[6]helicenes substituted at positions 5 and 13, or 8 and 10 were readily obtained (Figure 1.12). In fact, thanks to the contribution and proximity of the two nitrogen atoms, the more electron-rich benzo group can react with electrophilic reagents while the naphthyl subunits undergo reactions with nucleophilic moieties under vicarious conditions.119 Further transformations of the functionalized diaza[6]helicenes were possible through cross-coupling chemistry for instance using halogen- containing derivatives.

Figure 1.12: Diaza[6]helicene post-functionalization.

119 M. Makosza, J. Winiarski, Acc. Chem. Res. 1987, 20, 282.

27

Chapter 1: General Introduction

This survey has for now mostly detailed the synthetic state-of-the-art in the literature prior to this Ph.D. To further extend the scope of applications of the DMQA+ (1.43) family, it was thus decided to synthesize new chiral and unsymmetrical pH-sensitive fluorophores bearing non-substituted nitrogen atom. This chemistry led to the discovery of a facile hydrazine N-N bond cleavage while trying to synthesize the corresponding quinacridines which is reported in Chapter II. It was then decided to look for biological applications of these pH-sensitive derivatives and extended this concept to the synthesis of pH-sensitive diazaoxatriangulenes. Together with Dr. Petr Sherin from the group of Eric Vauthey (Department of physical chemistry, University of Geneva) and Dr Dimitri Moreau from the group of Prof. Jean Gruenberg (Department of Biochemistry, University of Geneva), studies on the selective interaction of these pH-sensitive diazaoxatriangulenes with late endosomes compartment of cell were conducted. Results are reported in Chapter III. Using the same precursor synthesized for the preparation of pH-sensitive derivatives a novel photoreductive protecting group (PRPG) centered on acridinium chromophores has been created. This methodology allows the efficient and direct synthesis of biorelevant non-protected aziridines and sulfoximines compounds (Chapter IV). Finally, we pursued our investigation for the development of original luminophores based on DMQA+ and we discovered the selective electrophilic (SEAr) functionalization of DMQA+ and quinacridines derivatives. These latter were used to prepare chiral and fluorescent BODIPY like and azobenzene dye (Chapter V).

28

Chapter 1:General Introduction

29

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

This chapter will deal with the synthesis of configurationally stable pH-sensitive and fluorescent quinacridines as well as their optical and chiroptical properties. For this purpose an efficient synthetic procedure using nucleophilic hydrazine as single nitrogen atom donor was developed. This simple protocol affords a family of configurationally stable quinacridines dyes after a spontaneous and facile N-N bond cleavage. This latter has been extensively studied and a mechanistic rationale presented.120

2.1 Preamble

Regular cationic DMQA+ [4]helicene containing oxygen and / or substituted nitrogen bridged + atoms are configurationally and chemically stable derivatives which display high pKR values (between 14 and 19).121 Thanks to the properties highlighted in the previous chapter, such cationic helicenes have been studied in different fields ranging from chemistry to biology. Moreover, these dyes exhibit optical features in the red and near infrared domain of light making these derivatives part of a fluorescent azahelicene sub-family. As a whole due to their stability, DMQA+ are insensitive to pH variations (2 < pH < 8) and their interesting absorption and emission properties do not vary with the acidity of the medium in which they are dissolved. This pH-insensitivity was actually seen as a limitation. Compounds that would behave otherwise would have in fact, the possibility to be interesting chiral pH-sensors. In the literature, there are few compounds of this type. Some azahelicenes have been used only as a proton sponge.122 Care was thus taken at the beginning of this PhD to address this problem

120 This work have been already published see: A. Wallabregue, P. Sherin, J. Guin, C. Besnard, E. Vauthey, J. Lacour, Eur. J. Org. Chem. 2014, 6431. 121 a) B. W. Laursen, F. C. Krebs, Chem. Eur. J. 2001, 7, 1773; b) B. W. Laursen, F. C. Krebs, Angew. Chem. Int. Ed. 2000, 39, 3432. 122 a) H. A. Staab, M. Diehm, C. Krieger, Tetrahedron Lett. 1994, 35, 8357; b) H. A. Staab, M. A. Zirnstein, C. Krieger, Angew. Chem. Int. Ed. Engl. 1989, 28, 86; c) H. A. Staab, T. Saupe, Angew. Chem. Int. Ed. Engl. 1988, 27, 865; d) M. A. Zirnstein, H. A. Staab, Angew. Chem., Int. Ed. Engl. 1987, 26, 460; e) F. J. Hibbert, Chem. Soc. Perkin Trans. 2, 1974, 1862.

30

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

and attempt to introduce a basic nitrogen atom at the periphery of the [4]helicene skeleton and this using a simple synthetic procedure.

2.2 Synthesis of Quinacridine Derivatives

Previously, to form cation of type 2.1 containing two unsubstituted nitrogen atoms, Takui, Morita and coworkers relied on a three-step protocol related to the classical procedure for the making of DMQA+1.43 (See chapter 1).123 First, compound 2.2 was prepared after four consecutive SNAr in modest yield, using N,N-dimethylethylenediamine as nucleophile and cation 2.3 as precursor. Then, the aminoalkyl side chains were removed through a Hoffmann elimination sequence using an excess of methyl iodide in basic conditions followed by an acidic treatment (Scheme 1.1).

Scheme 1.1: a) N,N-dimethylehylene diamine, NMP, 110 °C, 60% b) 1. MeI, MeOH, 110 °C, 2. t-BuOK, DMF,

20 °C, 3. aq HBF4 aq, 20 °C, 100%; c) 1. aq HBF4, MeOH, 70 °C, 2. aq Na2CO3, CH2Cl2, 20 °C, 94%.

Despite the efficiency of this method, an alternative straightforward and milder protocol was sought for the introduction of “naked” nitrogen atom in the synthesis of quinacridines of type 2.4. Several amine sources such as ammonia, ammonium hydoxyde and sulfamic acid were first tested with cation 2.5a as substrate (R = nPr, prepared by reaction of starting cation 1.45 with 2.5 equiv of propylamine at 25 °C). In a sealed vessel several set of conditions were tried under thermal and microwave heating. All the reactions led to complex mixtures of inseparable products. The results are summarized in Table 2.1.

123 A. Ueda, H. Wasa, S. Suzuki, K. Okada, K. Sato, T. Takui, Y. Morita, Angew. Chem. Int. Ed. 2012, 51, 6691.

31

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Table 2.1. Amines screening. Entry Amines Conditions Temperature Time Conversion

1 NH3 a 90 °C 14 h 0

b 110 °C 2 h 0

2 NH4OH a 90 °C 14 h 0

b 110 °C 2 h 0

3 NH2SO3H a 90 °C 14 h 0

b 110 °C 2 h 0

Conditions a: thermal, b: microwave

Hydrazine (NH2NH2) was then considered as a substitute to the others nitrogen sources for its availability, reasonable cost, lower volatility and higher nucleophilicity as shown by Mayr’s table.124 The often-difficult breakage of the N-N bond 125 due to its high bond dissociation energy ~ 60 kcal.mol-1 at 298 K 126 was a problem not to be underestimated but it was decided to consider it only later. The reaction between acridinium 2.5a and NH2NH2 (64-65% solution in water, 25 equiv, NMP, 110 °C) was thus attempted. To our satisfaction, the reaction occurred as planed and the desired quinacridine 2.4a was obtained directly (Table 2.2, entry 1, 50% yield); the cleavage of the N-N bond occurring seemingly during the formation of the helical adduct. Care was then taken to generalize this observation and optimize the conditions.

124 a) T. A. Nigst, A. Antipova, H. Mayr, J. Org. Chem. 2012, 77, 8142; b) H. Mayr, A. R. Ofial, J. Phys. Org. Chem. 2008, 21, 584. 125 a) K. Umehara, S. Kuwata, T. Ikariya, J. Am. Chem. Soc. 2013, 135, 6754; b) S. E. Denmark, O. Nicaise, J. P. Edwards, J. Org. Chem. 1990, 55, 6219; c) S. F. Nelsen, M. R. Willi, J. Org. Chem. 1984, 49, 1; d) J. M. Mellor, N. M. Smith, J. Chem. Soc., Perkin Trans. 1 1984, 2927. 126 a) J. A. Kerr, R. C. Sekhar, A. F. Trotman-Dickinson, J. Chem. Soc., 1963, 3217; b) N. S. Foner, R. L. Hudson, J. Phys. Chem., 1958, 29, 442; c) V. H. Dibeler, J. L. Franklin, R. Reese, J. Am. Chem. Soc. 1958, 81, 68.

32

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Table 2.2. Direct synthesis of quinacridine 1a. Reaction conditions. [a] [b] Entry Solvent T °C NH2NH2 Time Yield

1 NMP 110 °C 25 8 h 50%

2 NMP 110 °C 25 14 h 85%

3 DMSO 110 °C 25 14 h 80%

4 DMF 110 °C 25 14 h 85%

5 DMF 90 °C 25 14 h 83%

6[c] DMF 90 °C 25 8 h 92%

7 DMF 90 °C 10 8 h 70%

8 DMF 90 °C 10 17 h 82%

[a] Number of equivalents. [b] Isolated yields (%). [c] Reaction performed in red-tainted glassware.

The results are summarized in Table 2.2. With NMP as solvent, a longer reaction time was beneficial (85% yield, entry 2). DMSO and DMF performed equally well. However, as reactions were easier to purify in DMF, this solvent was kept for further studies. Indeed with DMF, addition of brine (aqueous solution of CuSO4 or LiCl) to the crude reaction mixtures leads to a selective precipitation of quinacridines 2.4a. Reaction yields were further improved by performing the reaction at 90 °C and in red-tainted glassware to limit the exposure to light (92%, entry 6). It was noticed that a decrease of the amount of hydrazine was detrimental (Table 2.2, entry 7). Finally it should be emphasized that quinacridine 2.4a was obtained under these conditions in 82% yield using a prolonged reaction time 17 h (entry 8).

With the optimized conditions in hands (Table 2.2, entry 6), a series of acridinium ions 2.5 were prepared by treating the carbenium ion 1.45 with the corresponding amines (see Table

33

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

2.3). The reactions generally proceeded smoothly and afforded after 30 minutes the desired “bloody” red ions in high yields after a selective precipitation.

Table 2.3. Preparation of acridiniums. Entry R Product Yield 1 Methyl 2.5b 95% 2 Hexyl 2.5c 97% 3 Hexadecyl 2.5d 94% * 4 Phenyl 2.5e 94% 5 Benzyl 2.5f 91%

6 CH2CH2NMe2 2.5g 80%

7 CH2CH2OH 2.5h 65%

8 CH2CH2OCH2CH2OH 2.5i 80%

9 NH2 2.5j 95% 10 Allyl 2.5k 94%

* reaction proceeded after 22 hours

These latter derivatives were then tested as substrates. The results are summarized in Table 2.4. In short, the reaction is general and alkyl, aryl and benzyl side chains are compatible (entries 1 to 5). Heteroatoms are also tolerated either as substituents on the side chains (entries 6 to 8) or as bound to a nitrogen atom (entry 9). Only in the case of 2.6k containing an allyl moiety was the reaction unsuccessful; the allyl group being systematically reduced to a propyl chain during the reaction to form 2.4a in good yield (90%) instead of 2.4k. This result will be later discussed in the mechanism section. Product 2.4e was found to be moderately soluble in a 4:1 mixture of hexane and dichloromethane. Single crystals were obtained that were analyzed by X-ray diffraction. Compound 2.4e adopts the twisted helical conformation typical of this type of [4]helicene.

34

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Table 2.4. Reaction scope (first approach). Entry Substrates R Product Yield[a]

1 2.5b Methyl 2.4b 97%

2 2.5c Hexyl 2.4c 82%

3 2.5d Hexadecyl 2.4d 80%

4 2.5e Phenyl 2.4e 94%

5 2.5f Benzyl 2.4f 78%

6 2.5g CH2CH2NMe2 2.4g 89%

7 2.5h CH2CH2OH 2.4h 85%

8 2.5i CH2CH2OCH2CH2OH 2.4i 88%

9 2.5j NH2 2.4j 85%

10 2.5k Allyl 2.4k 0% [b]

[a] Isolated yields (%). [b] Instead of desired product 1k, adduct 1a (R = n-Pr) was actually obtained in good yield (90%).

+ Unlike classical cationic DMQA that present a perfect C2 symmetry in their solid state conformation,127 compound 2.4e presents two different halves. On one hand the domain of the molecule containing the substituted nitrogen atom is essentially planar and constituted by a sequence of three rings with the middle heterocycle containing a sp2-hybridized nitrogen atom N1. The other half with the “naked” nitrogen N2 is bent and accommodates the deformation that gives rise to the helical structure.

127 a) J. Guin, C. Besnard, P. Pattison, J. Lacour, Chem. Sci. 2011, 2, 425; b) P. Mobian, N. Banerji, G. Bernardinelli, J. Lacour, Org. Biomol. Chem. 2006, 4, 224.

35

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Figure 2.1: Olex2 view of the crystal structure of 2.4e (one molecule of CH2Cl2 omitted). The thermal ellipsoids are draw at 50 % probability level.

Regardless of the positive results, a second approach was considered in order to shorten the synthetic strategy, obtain some mechanistic information and be able to work with unsaturated side chains (eg allyl). This approach used salt [2.5j][BF4] (Table 2.5, entry 9) as single precursor for all derivatives of type 2.4. As outlined in Scheme 2.2, it was considered that 2.5j ought to react with primary amines and afford as final products quinacridinium salt 2.6 or, ideally, quinacridines 2.4 if the spontaneous N-N bond cleavage would operate again.

Scheme 2.2: Second convergent synthetic approach.

To our satisfaction, salt [2.5j][BF4] reacted with n-propylamine and methylamine (25 equiv) at 90 °C to afford directly quinacridine 2.4a and 2.4b in excellent yields (90% and 91%, Table 2.5, entries 1 and 2). Reactions with benzyl, 2-(N, N’-dimethylamino)ethyl and allyl amines were then attempted knowing that competing oxidation, elimination and hydrogenation reactions might occur with such amines. Indeed, with benzyl amines, it has been noticed that acridinium salts of type 2.5 are effective photocatalysts for the efficient oxidation of these substrates into their corresponding imines as shown in Scheme 2.3.128

128 C. Nicolas, C. Herse, J. Lacour, Tetrahedron Lett. 2005, 46, 4605.

36

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Scheme 2.3: Photo-oxidation of benzylamine into benzylimine using acridinium 2.5.

With dimethylaminoethyl chains, elimination reactions can occur as shown at the beginning of this section (vide supra). Satisfactorily, adducts 2.4f, 2.4g and 2.4k were obtained in 88%, 84% and 60% yields respectively. In the reaction with allylamine, evidences for the reduction of the side-chain were not found this time. This functional group tolerance was further confirmed in the reaction of [2.5j][BF4] with regular hydrazine (entry 6). Amino- substituted quinacridine 2.4j (85%) was obtained without traces of a second deamination reaction. Ethanolamine also reacted with [2.5j][BF4] to afford the expected product 2.4h (Table 2.5, entry 5).

37

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Table 2.5. Reaction scope (second approach). Entry R Product Yield[a]

1 Propyl 2.4a 90%

2 Methyl 2.4b 91%

3 Benzyl 2.4f 88%

4 CH2CH2NMe2 2.4g 84%

5 CH2CH2OH 2.4h 83%

6 NH2 2.4j 85%

7 Allyl 2.4k 60%

[a] Isolated yields (%)

2.3 Mechanism of N-N Bond Cleavage

Having established the scope of this reaction we then turn our attention on the mechanism of this facile N-N bond cleavage. This reactivity is explained considering the existence of quinacridinium salts 2.6 as intermediates (Scheme 2.4). In fact, additions of hydrazine to “regular” acridinium salts (1st approach) or additions of primary amines to 2.5j (2nd approach) generate in both instances derivatives of type 2.6. The difference in the two approaches is only the nature of the nucleophilic reactant in excess in the crude mixtures. Herein, it is proposed that the remaining nucleophiles attack the exocyclic amino group of 2.6 and generate the corresponding quinacridine derivatives. Different byproducts are then generated. In the 1st approach, a triazane (NH2NHNH2) is obtained that decomposes spontaneously to generate diimide and ammoniac. In fact, a distant similarity can be found with the reaction of

38

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

hydroxylamine with hydroxylamine-O-sulfonic acid in basic media as reported by Durckheimer (equation 2.1).129 The reaction generates sulfonic acid and diimide by a similar reaction sequence. In the 2nd strategy, alkylhydrazines are produced that do not evolve further. If an unsaturated side chain is present on the molecule, then the second approach is better as it avoids the undesired reduction of the double (triple) bond by the in-situ generated HN=NH.

Scheme 2.4: Mechanistic rationale.

To establish some evidence for this mechanism, a compound of type 2.6 was prepared and isolated. It was performed by treatment of acridinium [2.5j][BF4] with only 5 equivalents of n- propylamine; the reaction being monitored by ESI-MS (Scheme 2.5). Compound 2.6a was isolated in 85% yield.

Equation 1: Hydroxylamine-O-sulfonic acid decomposition in basic media.

This compound was then reacted with an excess (20 equiv) of both hydrazine and propylamine to give in both cases the expected product 1a (90 and 80% respectively).

129 W. Durckheimer, liebigs. Ann. Chem. 1969, 721, 240.

39

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Scheme 2.5: a) n-propylamine (5 equiv), DMF, 90 °C, Ar, 8 h, without light, 85% yield. b) H2NNH2•H2O or n- propylamine (20 equiv), DMF, 90 °C, Ar, 3 h, without light, 100% conversion, 90 and 80% respectively.

2.4 Resolution and Configuration Stability of Quinacridine Derivatives

With these results in hands, the resolution of one of the helical quinacridines was pursued. In a first set of experiments, racemic 2.4a (R = n-Pr) was treated with common enantiopure acids (e.g. tartaric acid, dibenzoyl tartaric acid, mandelic acid).130 However, conditions that would induce a selective precipitation of a diastereomeric salt were not found. A semi- preparative chromatographic resolution of rac-2.4f (R = Benzyl) on a chiral stationary phase was then attempted because 2.4f was displaying higher solubility in mixtures of hexane and isopropanol. As a result, successful conditions were found using a Chiralpak IB® column and, as eluent, a mixture of n-hexane, isopropanol (60:40) with 0.1% of ethanolamine as additive. Starting from 25 mg of rac-2.4f and after several runs (see the experimental part), 10.0 mg (ee > 99%, 40% yield) and 8.0 mg (ee 99%, 32% yield) were afforded for the first and second eluted fractions corresponding to the dextrorotatory and levorotatory enantiomers of 2.4f 20 -4 respectively ([α] 365 +16500 and -16000 respectively, CH3CN, 10 M). The electronic circular dichroism (ECD) spectra of the two fractions are displayed on Figure 2.2 (250-700 nm).

130 J. Misek, F. Teply, I. G. Stara, M. Tichy, D. Saman, I. Cisarova, P. Vojtisek, I. Stary, Angew. Chem. Int. Ed. 2008, 47, 3188.

40

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Δε

ε

/ / LM

-

1

Cm

- 1

+ ____ + Figure 2.2: (Top) ECD spectra of (+)-[2.4f•H ][BF4] ( ) and (–)-[2.4f•H ][BF4] (- - -). (Bottom) Absoprtion

+ -6 spectrum of 2.4f•H . Solution in CH3CN (20 °C, 5·10 M).

The two fractions spectra display perfect mirror image and four Cotton effects are noticeable. The major transition are seen in high energy (UV) part of light at 250 305 and 390 respectively and finally a slight variation is seen at 550 nm.

However in order to establish the absolute configuration of these separated enantiomers, + (+)-2.4f and (−)-2.4f were transformed into their conjugated acids, namely (+)-[2.4f•H ][BF4] + and (−)-[2.4f•H ][BF4]. Dextrorotatory and levorotatory enantiomers of 2.4f afforded + 20 dextrorotatory and levorotatory salts [2.4f•H ][BF4]: [α] 365 = +10500 and -10000 -5 -1 respectively, CH3CN, 5.10 g.ml . Their ECD spectra were then compared with that of classical enantiopure cations of type 1.43. In fact, it was considered that the protonation of quinacridines 2.4 ought to generate species with chiroptical properties similar to that of permanently charged quinacridiniums 1.43. It was indeed the case as seen on Figure 2.3. In the top window are presented the ECD spectra of [(P)-1.43a][BF4] and [(M)-1.43a][BF4] (R = R’ = Pr) of which configurations were unambiguously assigned by VCD spectroscopy and X-ray crystallography in the presence of a chiral auxiliary of known configuration.131 These spectra + + are virtually superposable to that of (+)-[2.4f•H ][BF4] and (−)-[2.4f•H ][BF4] displayed in

131 a) C. Herse, D. Bas, F. C. Krebs, T. Bürgi, J. Weber, T. Wesolowski, B. W. Laursen, J. Lacour, Angew. Chem. Int. Ed. 2003, 42, 3162; b) B. Laleu, P. Mobian, C. Herse, B. W. Laursen, G. Hopfgartner, G. Bernardinelli, J. Lacour, Angew. Chem. Int. Ed. 2005, 44, 1879.

41

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

the bottom section. The only difference can be observed around 625 nm. Salt [(P)-1.43a][ + BF4] display a slightly positive Cotton effect while (+)-[2.4f•H ][BF4] presents a negative one. As such, it is safe to consider that the first and second eluted fractions on Chiralpak IB® correspond to (+)-(P) and (−)-(M)-2.4f respectively.

____ Figure 2.3: Top: ECD spectra of (P)-[1.43a][BF4] ( ) and (M)-[1.43a][BF4] (- - -). Bottom: ECD spectra of + ____ + (+)-[2.4f•H ][BF4] ( ) and (–)-[2.4f•H ][BF4] (- - -) derived from (+)- and (–)-[2.4f] respectively. Solutions in

-6 CH3CN (20 °C, 5·10 M).

Nevertheless, it should be emphasized, that protonation and deprotonation processes induce strong modifications in the enantiomers CD spectra. In fact, a shift and disappearance of Cotton effects are clearly seen when comparing the ECD spectra of neutral 2.4f and cationic 2.4f•H+ as shown in Figure 2.4. This was attributed to a change in the electronic distribution in the helical scaffold when going from the neutral quinacridine to the cationic quinacridinium (or vice versa). Indeed, one can consider that quinacridinium which present a perfect delocalization of the cationic charge have different electronic transition compared to quinacridine inducing therefore a modification of their corresponding ECD spectra. This pH-

42

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

switchable chiroptical property of azahelicenes has been recently reported by Crassous and co- workers.132

Δε

+ ____ + Figure 2.4: ECD spectra of (+)-[2.4f•H ][BF4] ( ) and (–)-[2.4f•H ] (dashed line) derived from (+)- and (–)-

-6 [2.4f] respectively; and of (+)-2.4f (°°°°°) and (–)-2.4f (˟˟˟˟˟). Solutions in CH3CN (20 °C, 5·10 M).

Finally, the determination of the racemization barrier was attempted by ECD, monitoring a single wavelength every 5 seconds (357 nm, see supporting information). It was necessary to heat dibutyl sulfoxide solutions of (+)-(P)-2.4f at 130 °C to start observing a decrease of the Cotton effect. After 1000 seconds, only a 20% loss of enantiomeric purity was observed at that temperature. Samples were then heated at 140 and 150 °C and analyzed for the same period of time. At 160 °C, the start of decomposition was observed. Measurements were thus not performed at that temperature and higher. Kinetic constants were calculated and activation parameters determined (Ea, A, ΔH‡, ΔS‡ and ΔG‡, see the Supporting Information). The racemization of 2.4f (ΔG‡ 30.7 ± 4.0 kcal.mol-1 at 140 °C) occurs quite faster than that of ‡ -1 [1.43a][BF4] for which a rather high barrier was measured (ΔG 41.3 kcal.mol at 200 °C).131a Clearly, the absence of an alkyl substituent on a nitrogen atom brings a large degree of flexibility. The very high positive value for the entropy tends to indicate that this transformation involves a strong solvent involvement and/or an ion pairing reorganization. The racemization barrier for 2.4f remains however slightly higher than that reported for analogous derivative 2.1 (ΔG‡ 28.4 kcal.mol-1, 28 °C).123

132 N. Saleh, B. Moore II, M. Srebo, N. Vanthuyne, L. Toupet, J. A. G. Williams, C. Roussel, K. K. Deol, G. Muller, J. Autschbach, J. Crassous, Chem. Eur. J. 2015, 21, 1673

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Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

With these compounds in hand, care was then taken to study and characterize their optical properties.

2.5 Photophysical Properties

The photophysical properties of quinacridine of 2.4 have been achieved in collaboration with Dr. Petr Sherin from Prof Eric Vauthey’s group (University of Geneva)

Absorption, pH titration and fluorescence measurements were performed with quinacridines 2.4b and 2.4j (R = Me and NH2 respectively) in aqueous solution containing 0.1% DMSO. Protonation strongly affects the electronic structure of the quinacridines and, thus, leads to significant changes in their absorption spectra as illustrated in Figure 2.5. For both 2.4b and 2.4j, the lowest energy absorption band shifts from 560 to 625 nm and a new band appears at 420 nm. The presence of the hydrazino substituent in 2.4j has very little effect on the absorption spectrum of both its neutral and cationic forms, pointing to a minor involvement of the exocyclic NH2 group in the lowest optical transitions. Consequently, a possible acid-base reaction on this group should have only a minor impact on the electronic absorption spectrum.

The pH-dependence of the absorbance at 620 nm (2.4b) and 625 nm (2.4j) is depicted in Figure 2.5 C and D (2.4j). These titration curves were analyzed assuming one and two acid- base equilibria for 2.4b and 2.4j, respectively (eq. 2.2 and 2.3) and the best fits were obtained + + with pK1 = 8.9 for 2.4b•H , and pK1 = 6.9 and pK2 = 9.1 for 2.4j•H .

44

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

Figure 2.5: Electronic absorption spectra and titration curves recorded with aqueous solutions of 2.4b (A, C) and 2.4j (B, D). The solid lines in C and D are the best fits of equations (2.2) and (2.3), respectively.

+ + The similarity of pK2 of 2.4j•H and pK1 of 2.4b•H points to an average pKa value of about 9.0 for the equilibrium between quinacridium and quinacridine conjugates. On the other + hand, the pK1 value found for 2.4j•H can be associated with the NH2 substituent and, as anticipated above, this equilibrium has a minor effect on the absorption spectrum.

A ×10- pH + A 10- pK1 A(625) = 1 2 (Eq. 2.2) 10- pH +10- pK1

A ×10-2 pH + A ×10- pH-pK1 + A ×10- pK1- pK2 A(625) = 1 2 3 (Eq. 2.3) (10- pK1 +10- pH )(10- pK2 +10- pH )

where, Ai is the absorbance to the form i at .

Equation 2.2 and 2.3: Equations used for the determination of quinacridines pKa.

The steady-state absorption and emission spectra of the quinacridine and quinacridinium forms of 2.4b and 2.4j are shown in Figure 2.6. The weak feature above 700 nm in the absorption spectrum of 2.4b at high pH is due to the scattering from small particles in suspension, most probably aggregates. Indeed, [4]helicene of type 1.43 have been shown to form dimeric aggregates already at modest concentration in aqueous solution.133 Moreover,

133 O. Kel, P. Sherin, N. Mehanna, B. Laleu, J. Lacour, E. Vauthey, Photochemical & Photobiological Sciences 2012, 11, 623

45

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

the quinacridine form that predominates at high pH is expected to be less hydrophilic and more prone to the formation of large aggregates.

Figure 2.6: Absorption and emission spectra of (A) 2.4b and (B) 2.4j in aqueous solutions at various pH.

The quinacridines 2.4b and 2.4j fluoresce weakly above 600 nm with quantum yields, ΦF, of the order of 5·10-3 (Table 2.6). Upon protonation, the emission band shifts to longer wavelength and peaks around 700 nm. Protonation has a negligible effect on the fluorescence quantum yield as illustrated in Table 2.6. The fluorescence spectrum and quantum yield of

2.4j with the protonated NH2 substituent are essentially the same as those of the non- protonated form, as could be expected from the quasi-identical absorption spectra.

The fluorescence decays of the various forms of 2.4b and 2.4j recorded at the maximum emission wavelength by time-correlated single photon counting (TCSPC) upon 395 nm excitation134 are depicted in Figure 2.7. Whereas marked differences can be seen for the acid and basic forms of 2.4b (Figure 2.7 A); all three forms of 2.4j exhibit very similar fluorescence dynamics. These time profiles could be well reproduced by a sum of two (2.4j) or three exponential functions (2.4b) convolved with the instrument response function, the resulting time constants being listed in Table 2.6. A component with a time constant larger than 4 ns and a relative amplitude smaller 0.01, was attributed to impurities present at very small concentrations (< 0.1 %) and will not be further considered.

46

Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

The structure of the quinacridiniums 2.4•H+ is very similar to that of type 1.43 [4]heliceniums investigated previously,133 which because of the presence an alkyl substituent on both N atoms, are not pH sensitive. Therefore, a similar interpretation of the biphasic nature of the fluorescence decay of 1b can be proposed, viz., the faster decay component is attributed to 2.4b, whereas the other is assigned to an aggregate. This explanation is comforted by further time-correlated single photon counting (TCSPC) measurements with a solution of 2.4b diluted by a factor two: the relative amplitude of the slower component was found to decrease from 0.19 to 0.11.

Figure 2.7: Fluorescence time profiles measured with 2.4b (A) and 2.4j (B) in water at various pH, instrument response function (IRF) and best fits (black).

In the case of 2.4j, the fluorescence of all three forms decays exponentially with the same time constant. No aggregate formation could be detected in both neutral and basic conditions. This can be explained by the presence of the polar and hydrophilic amino group that effectively counteracts hydrophobic effects.

Compared with the non pH-sensitive cationic [4]helicenes 1.43,133 the fluorescence quantum yield and lifetime of 2.4b and 2.4j are smaller by a factor of ca. 4. The excited-state dynamics

134 a) A. Fürstenberg, E. Vauthey, Photochem. Photobiol. Sci. 2005, 4, 260; b)P.-A. Muller, C. Högemann, X.

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Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

of 1.43 was found to be dominated by a non-radiative decay to the ground state, whose efficiency increased with the hydrogen-bond donating property of the solvent. Such H-bond- assisted non-radiative deactivation has been shown to be an efficient quenching mechanism for a large number of organic molecules in aqueous solutions.135 The faster non-radiative decay found here with compound 2.4 could be explained by the presence of the unsubstituted nitrogen atom that most likely forms hydrogen bonds with water molecules. Comparing 2.4b and 2.4j (Table 2.6), the somewhat lower ΦF and τf values of 2.4j speak in favour of a higher efficiency of this non-radiative process because of the presence of the hydrophilic amino group.

Table 2.6. Fluorescence properties of 2.4b and 2.4j.

-3[a] [b] [b] Product pH ΦF˟10 τf1/ns τf2/ns

2.4b 4.4 6 0.45 0.92

12 4 (0.81) (0.19)

0.48 -

2.4j 4.4 4 0.35 -

7.2 3 0.35 -

12 4 0.35 -

[a] Fluorescence quantum yield (error: ±2·10-3). [b] Fluorescence lifetime (error: ±10 %), the values in brackets are the relative amplitudes. A > 4 ns component with relative amplitude smaller than 0.01 has been omitted.

Allonas, P. Jacques, E. Vauthey, Chem. Phys. Lett. 2000, 326, 321. 135 a) S. R. Flom, P. F. Barbara, J. Phys. Chem. 1985, 89, 4489; b) T. Yatsuhashi, H. Inoue, J. Phys. Chem. A 1997, 101, 8166; c) P. S. Sherin, J. Grilj, Y. P. Tsentalovitch, E. Vauthey, J. Phys. Chem. B 2009, 113, 4953; d) P. Fita, M. Fedoseeva, E. Vauthey, Langmuir 2011, 27, 4645.

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Chapter 2: Synthesis of pH-Sensitive and Fluorescent Quinacridines

2.6 Applications

These helical quinacridines are effective dyes presenting interesting absorption and emission properties that can be modulated as a function of pH. Despite their weak fluorescence and relatively modest changes in the emissive properties upon protonation, the large difference in the absorption spectrum was sought to be advantageously used for sensing the variations of pH in biological systems. Unfortunately we have not been able to detect any fluorescence variation in cells and this was attributed to the high pKa values of quinacridines. Therefore two different strategies were sought for decreasing this pKa value and enhancing at the same time their optical properties, their quantum yield of fluorescence in particular.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangulenes as Late Endosomes Probes

In this chapter the pH-sensitive quinacridine derivatives prepared in chapter 2 has been used to synthesize novel triangulenes chromophores. After the preparation, the optical properties of these fluorophores are reported and their application as selective late endosome probes presented. This application was developed in collaboration with Doctor Peter Sherin and Doctor Dimitri Moreau from Professor Eric Vauthey and Professor Jean Gruenberg group respectively.

3.1 Preamble

Endocytosis,136 which is the uptake of extracellular materials by cells, regulates fundamental cellular processes, including nutrient uptake, cholesterol homeostasis, immunity, signaling, adhesion, membrane turnover, and development.137 As a consequence, the dysfunction of endocytic organelles is associated with a number of diseases, including in particular lysosomal storage disorders.138 Endocytotic organelles are intensively studied, and their identification and characterization is usually achieved by fluorescence microscopy using antibodies coupled to fluorophores139 or ectopically expressed proteins coupled to intrinsically fluorescent and genetically modified proteins (e.g. green fluorescent protein, GFP).140 However, there is a growing need and interest for rapid and non-invasive techniques based on small molecules (MW < 500-600), for instance in turn-on fluorescence or ratiomeric assays.141 Because specificity is not easily obtained with small molecules, one of the main challenges is

136 a) McMahon, H. T.; Boucrot, E., Nat. Rev. Mol. Cell Biol. 2011, 12, 517; b) Gruenberg, J.; Stenmark, H., Nat. Rev. Mol. Cell Biol. 2004, 5, 317; c) Mukherjee, S.; Ghosh, R. N.; Maxfield, F. R., Endocytosis. 1997, 77, 759 137 C. C. Scott, S. Vossio, F. Vacca, B. Snijder, J. Larios, O. Schaad, N. Guex, D. Kuznetsov, O. Martin, M. Chambon, G. Turcatti, L. Pelkmans, J. Gruenberg, EMBO Rep. 2015, 16, 741. 138 A. H. Futerman, G. van Meer, Nat Rev Mol Cell Biol 2004, 5, 554. 139 Y. Urano, D. Asanuma, Y. Hama, Y. Koyama, T. Barrett, M. Kamiya, T. Nagano, T. Watanabe, A. Hasegawa, P. L. Choyke, H. Kobayashi, Nat Med 2009, 15, 104. 140 G. Miesenbock, D. A. De Angelis, J. E. Rothman, Nature 1998, 394, 192. 141 J. Han, K. Burgess, Chem. Rev. 2009, 110, 2709.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes to achieve selective detection and imaging of the organelle of interest,142 in particular when these organelles display relatively similar pH values e.g. early endosomes pH ≈ 6.2 and late endosomes and lysosomes pH ≈ 5.0–5.5.143 With previously synthesized quinacridine derivatives 2.4, we saw an opportunity to develop new pH-sensitive fluorophores that could achieve a high selectivity and to use the organelle pH as a mean for distinction.

3.2 Synthesis and Properties of pH-Sensitive Diazaoxatriangulenes

As highlighted in chapter 1, cationic triangulenes of type 3.1 and 3.2 have been studied in different fields ranging from material sciences to biology.144 For this latter application lipophilic variant of compounds 3.1 and 3.2 have been synthesized and studied with biorelevant DOPC vesicles as a membrane localized fluorescent probe.145 However, as these derivatives are unresponsive to pH variations (2 < pH < 8), it seemed unlikely that these core structures would provide a selectivity. Modifications were then looked for and derivatives 3.3a, 3.3b and 3.3c containing a basic nitrogen atom were thus targeted (Scheme 3.1, R = hexadecyl, phenyl and propyl respectively).

Figure 3.1: Cationic diazaoxatriangulene 3.3a•H+ (hexadecyl side chain) and conjugated base 3.3a. Previously reported cationic triangulenes (R = alkyl, aryl).

The synthesis of triangulenes of type 3.3 was achieved using the previously prepared quinacridines 2.4a, 2.4d and 2.4e (Scheme 3.1). Dissolution of these compounds in molten

142 a) A. Sampedro, R. Villalonga-Planells, M. Vega, G. Ramis, S. Fernandez de Mattos, P. Villalonga, A. Costa, C. Rotger, Bio. chem. 2014, 25, 1537-46. b) D. Soulet, B. Gagnon, S. Rivest, M. Audette, R. Poulin, J. Biol. Chem. 2004, 279, 49355. 143 a) C. C. Scott, J. Gruenberg, BioEssays 2011, 33, 103; b) V. Marshansky, M. Futai, Curr. Op. Cell Biol 2008, 20, 415-426 144 J. Bosson, J. Gouin, J. Lacour, Chem. Soc. Rev. 2014, 43, 2824 145 B. P. Maliwal, R. Fudala, S. Raut, R. Kokate, T. J. Sorensen, B. W. Laursen, Z. Gryczynski, I. Gryczynski, PloS one 2013, 8, e63043

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes pyridinium hydrochloride (150 °C, 4h) afforded the O-ring closure. Compounds 3.3a, 3.3b and 3.3c were then isolated as their hexafluorophosphate salts after anion exchange metathesis

(KPF6). With these compounds in hand, care was taken to study their pH-sensitivity and characterize the optical properties as a function of the acidity.

Scheme 3.1: Synthesis of diazaoxatriangulenes salts 3.3. a) molten pyrH+Cl- (50 equiv), 150 °C, 4 h and then metathesis with a 2 M solution of KPF6, b) NaHCO3 sat solution then 1M solution CF3CO2H.

In fact, absorption and fluorescence measurements were performed with all the triangulenes in aqueous solutions containing 0.03% DMSO and cetyltrimethyl ammonium bromide (CTAB, 4 mM) to prevent the precipitation of neutral 3.3a, 3.3b and 3.3c respectively; the ammonium salt having little influence on the spectral properties of the triangulenes. To our satisfaction, protonation strongly affected the electronic structure and led to significant changes in the absorption and emission spectra (Figure 3.2, part A: 3.3a•H+ and part B: 3.3a).146 A loss of vibronic structure and a red shift of both absorption and emission bands are seen upon protonation of the neutral form. The mirror image symmetry of absorption and fluorescence spectra indicates one emissive state. This is supported by the fluorescence excitation spectra, which exhibit full coincidence with the absorption spectra. It is noteworthy that the aliphatic or aromatic nature of the side chain (R) has very little effect on the absorption spectrum of both neutral and cationic forms (Figure 3.3); a similar lack of influence has been noticed in the quinacridine series of type 2.4 (cf chapter 2).

146 The absorption and emission spectra were recorded for both protonated and neutral forms of 3.3a and 3.3b in various organic solvents (see appendix). The increase of solvent polarity and hydrogen bond donor ability gives rise to monotonic but modest bathochromic shifts (approximately 10 nm) of both absorption and emission spectra of 3.3a and 3.3b. However no clear influence of classical solvent parameters on the spectral properties of 3.3a•H+ and 3.3b•H+ can be seen.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

Figure 3.2: Electronic absorption and fluorescence spectra recorded with aqueous solutions of 3.3a at various pH (part A: 2.0, part B: 11.2).

In Figure 3.3 are depicted the pH-dependence of the absorption spectra (A, C and E: 300-650 nm) and of the specific absorbance at 575 nm (B, D and F) for 3.3a, 3.3b and 3.3c. The titration curves were analyzed assuming one acid-base equilibrium according to the equation Eq. 3.1 and the best fits were obtained for pKa values of 4.8, 5.3 and 6.6 for 3.3a, 3.3b and 3.3c respectively.

(Eq. 3.1)

(Eq. 3.2)

In which OD1(λ) and OD2(λ) are absorptions of protonated and neutral forms and [H] the concentration of protons in the sample, [H]=10-pH.

Equation 3.1 and 3.2: Equations used for the determination of triangulenes pKa

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

Interestingly, the nature of the nitrogen substituent has an influence on the acidity as changing the hexadecyl chain (3.3a) by a phenyl or propyl group increases the pKa value from 4.8 to 5.6 and 6.6 for 3.3b and 3.3c respectively (see Figure 3.3 and Table E1 in appendix).147

A B

C D

E F

Figure 3.3. Electronic absorption spectra and titration curve recorded with aqueous solutions of 3.3a (A, B), 3.3b (C, D) and 3.3c. The titration curves B, D, F recorded at 575 nm for 3.3a and 3.3b and at 518 nm for 3.3c. The solid lines in B, D and F are the best fit of equation (3.1).

The neutral diazaoxatriangulenes 3.3a and 3.3b fluoresce near 580 nm with a quantum 148 yield (ΦF) of 16 and 14% in aqueous solutions respectively (Table 3.2). These quantum yields values are higher in organic solvents varying between 20 and 40% (Table E2, in Appendix). Upon protonation, the emission band shifts to longer wavelength and peaks around 600 nm. Yet the protonation has a negligible effect on the fluorescence quantum yield of both forms of 3.3a and 3.3b in aqueous solution (Table 3.2).

147 Preliminary DFT calculations indicate that the HOMO orbitals and charge distributions of compounds 3.3a, 3.3b, 3.3c (and their conjugated acids 3.3•H+) are very similar. Depending on the side chain, large differences in solvation must therefore occur between species 3.3•H+and 3.3. 148 Compounds 3.3b and 3.3c display similar photophysical properties, as in 2.4 series the substitution has no influence on these properties, therefore only the values of 3.3b are presented.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

Table 3.2. Fluorescence properties of protonated and neutral forms of 1a and 1b in aqueous solutions. Standard error 10%.

Products pH λabs, nm λem, nm ΦF, % τF, ns

3.3a 11.1 556 578 16 7.8

3.3b 11.2 559 580 14 6.5

3.3a•H+ 2.0 562 601 14 7.7

3.3b•H+ 2.0 558 595 13 7.7

The fluorescence decays of protonated and neutral forms of 3.3a and 3.3b were recorded at the maxima of emission bands by time-correlated single photon counting (TCSPC) upon excitation at 375 nm. These fluorescence decays could be well reproduced using a monoexponential function (see appendix Figure E3) with the time constants (τF) listed in Table 3.2 for aqueous solutions and in Table E2 (appendix) for organic solvents. Significant isotopic effect indicates a participation of intermolecular hydrogen bonds in the acceleration of excited state decay for diazaoxatriangulenes as it has been already noticed for quinacridine of type 2.4 (cf chapter 2).133 The photochemical stability of protonated and neutral forms of 3.3a in acetonitrile was examined under anaerobic and aerobic conditions. The presence of oxygen visibly reduces the degradation of 3.3a form and has a minor influence on the + photostability of 3.3a•H form. Rough estimations of the photodegradation yields (Φdeg) give -3 -4 the following values: Φdeg < 1×10 for 3.3a under anaerobic conditions and as Φdeg < 5×10 for other cases (see Appendix for details).

With all these information in hands the solubility of diazaoxatriangulenes 3.3 in biorelevant phosphate buffer saline PBS was examined. Not too surprisingly, an imminent precipitation of the dyes was observed. Therefore an anion metathesis was considered to render the triangulenes soluble in PBS buffer. The whole derivatives 3.3 were converted in good yields (from 90 to 98%) to their corresponding trifluoroacetate salts 3.4, by washing them successively with 1 M solutions of NaHCO3, and after basification, the compounds are acidified with CF3CO2H acid (Scheme 3.2). The effect of the counter ion on the pKa of the triangulenes was also verified. Importantly, and of relevance for the remainder of study – – changing PF6 by CF3CO2 the counter ion has little effect on the pKa see Figure 3.4 and Table E2.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

Figure 3.4. (A, C) Electronic absorption spectra of 3.4a•H+ recorded in aqueous solution in absence (A) and in presence (C) of 4 mM of CTAB. Titration curves of 3.4a•H+ recorded in aqueous solution in absence (B) and presence (D) of 4 mM of CTAB. The solid line in (B) is the best fit according to the equation (Eq. 3.2) and in (D) to the equation (Eq. 3.1).

3.3 Application

To evaluate our initial hypothesis, HeLa cells were treated with the three compounds 3.4, and a characteristic punctate staining was observed only with the more lipophilic 3.4a by fluorescence microscopy (Figure 3.5, part A; nuclei are stained with DAPI). The 3.4a labeling colocalized to a very large extent with well-established markers of late endocytic compartments, the unconventional phospholipid lysobisphosphatidic acid (LBPA) detected with a monoclonal antibody and the transmembrane protein LAMP1.136 The staining was highly specific since little if any 3.4a was found in structures lacking LBPA or LAMP1. Moreover, no colocalization could be observed between 3.4a and the early endosomal marker EEA1 (Figure 3.5 part B).149 These data show that 3.4a serves as a selective marker of late endocytic organelles. The staining with 3.4a was abolished after neutralization of the endosomal pH with the protonophore ionomycin or with inhibitors of the V-ATPase concanamycin B or bafilomycin (Figure 3.5, part C),150 demonstrating that 3.4a accumulation is strictly dependent on the

149 A. Simonsen, R. Lippe, S. Christoforidis, J.-M. Gaullier, A. Brech, J. Callaghan, B.-H. Toh, C. Murphy, M. Zerial, H. Stenmark, Nature 1998, 394, 494. 150 C. C. Scott, J. Gruenberg, BioEssays 2011, 33, 103.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes acidic environment of late endocytotic organelles, As such, it is more than likely that the active form of 3.3a is the conjugated acid form 3.4a•H+. While 3.4a staining was easily detected without fixation in living cells (Figure 3.5, part C) as anticipated, the staining pattern was retained after fixation in paraformaldehyde (PFA) (Figure 3.5, part A and B). Hence, 3.4a is not only selective for late endosomes, but, in contrast to most lysosomotropic dyes, it also serves as a fixable reporter of the pH in this organelle.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

Figure 3.5: A. HeLa cells treated with 50µM (3.4a) for 5h, and fixed in PFA. The cells were then labeled with antibodies to LBPA and Lamp1, and then with labeled secondary antibodies, and analyzed by fluorescence microscopy. Nuclei are stained with DAPI. B. HeLa cells treated with 300µM (3.4a) for 18h were processed and analyzed as above using antibodies to EEA1. C. HeLa cells treated for 3h with 30µM (3.4a) together with 1µM ionomycin, 0.1 µM concanamycin B or 1 µM bafilomycin A, were analyzed live, without fixation, by fluorescence microscopy

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

To understand the molecular basis of this useful and practical fixation, a few experiments were performed. First, the addition of 3.4a to a PBS buffer solution containing 4% of PFA. Interestingly, after 10 minutes only a complete transformation of the UV-vis spectra of 3.4a was achieved (Figure 3.6). The resulting spectrum was virtually superimposable to that of 3.4a•H+, despite the lack of pH change. This strongly indicates a quaternisation of the sp2 nitrogen upon the addition of PFA. In fact, it is likely that a reaction between nucleophile 3.4a and electrophilic PFA occurs to yield a carbinol pyridinium type of species. Such processes have been established. The resulting mixture display the same absorption spectrum than 3.4a•H+. These observations demonstrate that 3.4a provides a highly specific pH-sensitive dye of late endosomes not only in live cells imaging but also in fixed cells.

Figure 3.6 Absorption spectra of 3.4a in PBS buffer (red line) and 3.4a in PBS buffer containing 4% of paraformaldehyde after 10 min (blue line).

In conclusion, the first small molecule allowing the selective imaging and monitoring of late endosomes in the form of a diazaoxatriangulene fluorophore 3.4a (hexadecyl side chain) has been disclosed. The designed compound was prepared in 3 steps from a simple carbenium precursor. In water, depending upon the pH, this photochemically stable dye fluoresces in the red part of visible light (578 and 601 nm) with a quantum yield between 14 and 16 % and an excited state lifetime 7.7-7.8 ns. Importantly, the protonated form 3.4a•H+ provokes a specific staining of late endosome compartments (pH 6.5) after 5 h incubation with HeLa cells. Not surprisingly, this late endosome marking depends on the intraorganelle pH and changing the nature of the lipophilic chain provokes a loss of selectivity. Interestingly, fixation of the fluorophore is readily achieved with paraformaldehyde giving the possibility to image both live and fixed cells.

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Chapter 3: Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangules as Late Endosomes Probes

60

Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

This chapter will deal with the development of a simple and efficient, possibly one pot, two- step metal-free synthesis of unprotected aziridines and sulfoximines. These highly valuable compounds are important derivatives present in several biologically active compounds (antibiotics and antitumors) and used in chemistry as versatile building blocks. For this purpose, the previously synthesized N-aminoacridinium ion 2.5j was used as a nitrene precursor in oxidative aziridination of alkenes, and in the preparation of sulfoximines and sulfimides from sulfoxides and thioethers. After the addition, the acridine group can be cleaved under mild conditions using visible light irradiation. This photoreductive deprotection affords a variety of NH aziridines and sulfoximines in high yields. A mechanism for the N-N bond cleavage is proposed and two pathways were identified.

4.1 Preamble

Aziridines are important structural motifs present in many naturally active molecules like for instance Azinomycin A,151 Mitomycins,152 Miraziridine,153 FR-66979 and FR- 900482,154 which are well known for their antibiotic and antitumor properties (Figure 4.1). The intrinsic reactivity of these strained three membered rings makes them attractive synthetic targets and versatile building blocks for the preparation of other compounds of great interest.155 For instance aziridines undergo regio and stereoselective nucleophilic ring openings and also ring expansion reactions, and 1,3-dipolar cycloadditions.156

151 a) R. S. Coleman, R. J. Perez, C. H. Burk, A. Navarro, J. Am. Chem. Soc. 2002, 124, 13008; b) R. S. Coleman, J. Li, A. Navarro, Angew. Chem. Int. Ed. 2001, 40, 1736; c) R. S. Coleman, Synlett 1998, 1031. 152 a) R. S. Coleman, W.Chen, Org. Lett. 2001, 3, 1141; b) M. Kasai, M. Kono, Synlett 1992, 778. 153 Y. Nakao, M. Fujita, K. Warabi, S. Matsunaga, N. Fusetani, J. Am. Chem. Soc. 2000, 122, 10462. 154 a) R. Ducray, M. A. Ciufolini, Angew. Chem. Int. Ed. 2002, 41, 4688; b) M. Suzuki, M. Kambe, H. Tokuyama, T. Fukuyama, Angew. Chem. Int. Ed. 2002, 41, 4686; c) T. C. Judd, R. M. Williams, Angew. Chem. Int. Ed. 2002, 41, 4683. 155 a) M. Lautens, K. Fagnou, V. Zunic, Org. Lett. 2002, 4, 3465; M. T. Reetz, R. Jaeger, R. Drewlies, M. Hubel, Angew. Chem. Int. Ed. Engl. 1991, 30, 103 and references therein. 156 Aziridines and Epoxides in Organic Synthesis (Ed.: A. Yudin),Wiley-VCH, Weinheim, 2006

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

The aim of the following sections is to give an overview of the most effective approaches for the preparation of protected aziridine derivatives. Then, a rapid summary will be given on the preparation of free NH products.

Figure 4.1: Aziridines containing natural products.

4.2 Synthesis of Protected Aziridines

Traditionally, aziridines are prepared using two main strategies. The first method is the intramolecular cyclization of amino alcohols, or related derivatives; such moieties being often generated as intermediates by the addition of diazo-containing compounds or sulfur ylides to protected imines (Figure 4.2).157,158,159

157 a) D. V. Kashelikar, P. E. Fanta, J. Am. Chem. Soc. 1960, 82, 4927; b) P. A. Leighton, W. A. Perkins, M. L. Renquist, J. Am. Chem. Soc. 1947, 69, 1540; c) H. Wenker, J. Am. Chem. Soc. 1935, 57, 2328. 158 a) S. E. Larson, G. L. Li, G. B. Rowland, D. Junge, R. C. Huang, H. L. Woodcock, J. C. Antilla, Org. Lett. 2011, 13, 2188; b) A. L. Williams, J. N. Johnston, J. Am. Chem. Soc., 2004, 126, 1612; c) J. S. Yaday, B. V. S. Reddy, P. N. Reddy, M. Shesha Rao, Synthesis, 2003, 1387; d) J. C. Antilla, W. D. Wulff, Angew. Chem. Int. Ed. 2000, 39, 4518; e) J. C. Antilla, W. D. Wulff, J. Am. Chem. Soc. 1999, 121, 5099; f) L. asarrubios, J. A. Perez, M. Brookhart, J. L. Templeton, J. Org. Chem. 1996, 61, 8358; g) W. Xie, J. Fang, J. Li, P. G. Wang, Tetrahedron 1999, 55, 12929 159 a) E. J. Corey, M. Chaykovsky, J. Am. Chem. Soc., 1965, 87, 1353; b) A. W. Johnson , R. B. LaCount, J. Am. Chem. Soc., 1961, 83, 417

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Figure 4.2: Classical synthetic strategies of aziridines.

Catalytic asymmetric synthesis of a range of aziridines using these latter strategies has been reported.160,161 These processes are well established and some of them are considered as named reactions.

The second protocol corresponds to the transfer of substituted nitrenes (or nitrenoids) onto olefins alkenes (C2 +N1, Figure 4.3 part A). The nitrene derivatives can be generated either by thermal or photochemical decomposition of sulfonyl and aryl azides or from iminoiodinanes 4.1. These reagents 4.1 are generally preformed or generated in situ by oxidizing appropriate amines with iodosobenzene PhI=O or iodosobenzene diacetate 162,163 PhI(OAc)2, PIDA (Figure 4.3, part B). This approach was pioneered by Mansuy and co- workers using iminoiodinanes 4.1 as nitrogen-transfer reagents under manganese and iron catalysis (MnIII and FeIII porphyrins).164 This transformation has been considered as a great achievement from the start and affords the aziridine products from modest to very good yields depending on the catalyst.

Figure 4.3: A) Nitrene transfer on olefins and B) preparation of iminoiodinanes 4.1.

160 K. B. Hansen, N. S. Finney, E. N. Jacobsen, Angew. Chem. Int. Ed. Engl. 1995, 34, 676. 161 a) O. Illa, M. Namutebi, C. Saha, M. Ostovar, C. C. Chen, M. F. Haddow, S. Nocquet-Thibault, M. Lusi, E. M. McGarrigle, V. K. Aggarwal. J. Am. Chem. Soc., 2013, 135,1195; b) V. K. Aggarwal, E. Alonso, G. Fang, M. Ferrara, G. Hynd, M. Porcelloni, Angew. Chem. Int. Ed. 2001, 41, 1433; V. K. Aggarwal, Chem. Rev., 1997, 97, 2341 162 a) S. Cenini, E. Gallo, A. Caselli, F. Ragaini, S. Fantauzzi, C. Piangiolino, Coord. Chem. Rev. 2006, 250, 1234; b) S. Braese, C. Gil, K. Knepper, V. Zimmermann, Angew. Chem. Int. Ed. 2005, 44, 5188; c) T. Katsuki, Chem. Lett. 2005, 34, 1304; d) B. C. G. Soderberg, Curr. Org. Chem. 2000, 4, 727 163 V. V. Zhdankin, P. J. Stang, Chem. Rev. 2008, 108, 5299. 164 D. Mansuy, J. P. Mahy, A. Dureault, G. Bedi, P. Battioni, J. Chem. Soc. Chem. Commun. 1984, 1161.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

More recently and importantly, strong progresses have been achieved through the use of copper and rhodium catalysts by Evans, Jacobsen and Müller among others (Scheme 4.1). 165,166,167,168 With ligands 4.2 and 4.3, the level of enantioinduction can reach 96 and 98% respectively (Scheme 4.1). Besides iminoiodinanes derivatives, halogen amines such as Chloramine T have also been used as nitrogen sources in this reaction.169

Scheme 4.1: Transition metal catalyzed addition of nitrene to olefins.

However, a useful modification of the method involves the in situ generation of nitrene, by means of oxidation of hydrazine derivatives170. In fact, readily available N- aminophthalimide 4.4 has been used for the intermolecular aziridination of alkenes (Scheme 4.2). This transformation was first achieved electrochemically by Yudin and co-workers.171 In a typical reaction, N-aminophthalimide 4.4 is selectively oxidized and transferred to a large variety of alkenes affording aziridines of type 4.5 in good yields. The success of this reaction relies on the absence of overoxidation.

165 a) D. A. Evans, M. M. Faul, M. T. Bilodeau, B. A. Anderson, D. M. Barnes, J. Am. Chem. Soc. 1993, 115, 5328; b) D. A. Evans, M. M. Faul, M. T. Bilodeau, J. Org. Chem. 1991, 56, 6744; c) D. A. Evans, K. A. Woerpel, M. M. Hinman, M. M. Fad, J. Am. Chem. Soc. 1991, 113,726. 166 Z. Li, K. Conser, E. Jacobsen J. Am. Chem. Soc. 1993, 115, 5326. 167 P. Müller, C. Baud, Y. Jacquier, Tetrahedron 1996, 52, 1543. 168 Copper catalyzed asymmetric synthesis (Ed: A. Alexakis), John Wiley & Sons, Wiley-VCH, 2013 169 J. Jeong, B. Tao, I. Sagasser, H. Henniges, K. B. Sharpless, J. Am. Chem. Soc. 1998, 120, 6844. 170 R. S. Atkinson, Tetrahedron 1999, 55, 1519. 171 T. Siu, A. K. Yudin, J. Am. Chem. Soc. 2002, 124, 530.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Scheme 4.2: Electrochemical synthesis of aziridines 4.5.

Then, concomitantly with the group of Che, the group of Yudin pursued the reactivity study of 4.4 and reported the use of commercially available PIDA 4.7 163 as the oxidant necessary for the aziridination (Scheme 4.3). 172,173 This stereospecific reaction affords aziridines 4.5 from modest to excellent yields. With another hydrazine precursor 4.6, products 4.8 are afforded after the PIDA oxidation (Scheme 4.3).

Scheme 4.3: Aziridination of alkenes with N-substituted hydrazine mediated by PIDA 4.7.

In term of mechanism, an N-acetoxyphthalimide intermediate 4.9, similar to the intermediate postulated by Atkinson has been suggested.170,174 This species is generated after oxidation of N-aminophthalimide 4.4 along with a loss of acetic acid and iodobenzene (Scheme 4.4). The intermediate 4.9 is then transferred efficiently to alkenes in a concerted manner via the suggested transition state 4.10.

172 L. B. Krasnova, R. M. Hili, O. V. Chernoloz, A. K. Yudin, Arkivoc, 2005, 4, 26. 173 J. Li, J.-L. Liang, P. W. H. Chan, C.-M. Che, Tetrahedron Lett. 2004, 45, 2685. 174 a) R.S. Atkinson, D.W. Jones, B. J. Kelly, J. Chem. Soc., Perkin Trans. 1 1991, 1344; b) R.S. Atkinson, M.J. Grimshire, B. J. Kelly, Tetrahedron 1989, 45, 2875

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Scheme 4.4: Formation of reactive N-acetoxyphthalimide intermediate.

However, to our knowledge, a procedure for the cleavage of the N-N bond in the products 4.5 and 4.8 has never been reported. In fact, the removal of the phthalimido group and the isolation of the corresponding NH aziridines is a challenging reaction in this case due to the reactivity (instability) of the products. For other type of aziridine derivatives such as sulfonamides, several conditions have been reported in the literature,175 their cleavage being also sometimes problematic.176

4.3 Synthesis of Unprotected Aziridines

Conditions were developed for the preparation of unprotected aziridines. For instance transition-metal catalyzed nitrene transfers were developed, using nitrenes (or nitrenoids) bearing easily removable functional groups, allowing after the addition, a selective deprotection. Dauban, Dodd and co-workers employed iminoiodinane of type 4.11 namely [(N-(alkylsulfonyl)imino]phenyliodinane for the intermolecular aziridination of alkenes (Scheme 4.4).177 In a typical reaction, olefins derivatives are mixed with slight excess of preformed iminoiodinane 4.11 in CH3CN and molecular sieves 4 Å (Scheme 4.5). The

175 a) N. Shohji, T. Kawaji, S. Okamoto, Org. Lett., 2011, 13, 2626; b) Z. Moussa, D. Romo, Synlett, 2006, 3294; c) I. Fleming, J. Frackenpohl, H. Ila, J. Chem. Soc., Perkin Trans. 1 1998, 1229; d) E. Alonso, D. J. Ramón, M. Yus, Tetrahedron, 1997, 53, 14355; e) A. F. Parsons, R. M. Pettifer, Tetrahedron Lett. 1996, 37, 1667; f) T. Fukuyama, C.-K. Jow, M. Cheung, Tetrahedron Lett. 1995, 36, 6373; g) E. Vedejs, S. Lin, J. Org. Chem. 1994, 59, 1602; h) T. W. Greene, P. G. M. Wuts, Protective Groups in Organic Chemistry, 2nd ed.; Wiley- Interscience: New York, 1991. 176 a) P. G. M. Wuts, J. M. Northuis, Tetrahedron Lett. 1998, 39, 3889; b) T. Hudlicky, X. Tian, K. Königsberger, R. Maurya, J. Rouden, B. Fan, J. Am. Chem. Soc. 1996, 118, 10752 177 P. Dauban, R. H. Dodd, J. Org. Chem. 1999, 64, 5304

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines protected compounds 4.12 were obtained from modest to good yields. The alkylsulfonylated aziridines were then easily deprotected by treatment with an excess of tris(dimethylamino) sulfonium difluorotrimethylsilicate (TASF, 4.13) at room temperature to yield NH aziridines from modest to high yields (Scheme 4.5).

Scheme 4.5: NH aziridines synthesis using [(N-(alkylsulfonyl)imino]phenyliodinane 4.11.

Thereafter, the group of Lebel described the intramolecular aziridination of allylic N- tosylcarbamates 4.14 and the intermolecular reaction of styrenes with trichloroethyl N- tosylcarbamates 4.15, by means of copper catalysis (scheme 4.6).178 This straightforward method affords the desired cyclic carbamate 4.16 and Troc protected aziridines products 4.17 in moderate to good yields. The in situ generated nitrenoid species avoids the utilization of preformed sulfonyliminophenyl iodinane reagents. Moreover, products 4.17 were subsequently deprotected from good to excellent yields (74-93%) under basic conditions using

LiOH·H2O in a mixture of H2O/CH3CN. This provides the corresponding NH aziridines without ring opening. Enantioenriched NH aziridines (ee > 98%) could also be prepared using an enantiopure Troc 4.15.179

178 a) H. Lebel, S. Lectard, M. Parmentier, Org. Lett. 2007, 9, 4797; b) H. Lebel, K. Huard, S. Lectard, J. Am. Chem. Soc. 2005, 127, 14198 179 H. Lebel, C. Spitz, O. Leogane, C; Trudel, M. Parmentier Org. Lett. 2011, 13, 5460

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Scheme 4.6: Copper catalyzed alkenes aziridination with N-Tosylcarbamates.

Recently, Kürti and co-workers180 disclosed an elegant and efficient direct stereospecific synthesis of NH and NMe aziridines, using the well-known Rh2(Espino)2, Du Bois’ catalyst 181 4.18 and O-(2,4-dinitrophenyl)hydroxylamine (DPH)182 4.19 as nitrene precursor (Scheme 4.7).

Scheme 4.7: Direct synthesis of unprotected NH aziridines.

Based on quantum chemical calculations, the authors have proposed a mechanism involving the formation of a triplet nitrene intermediate after a loss of dinitrophenol. The addition of the nitrene biradical 4.20 to alkenes is followed by a fast spin interconversion of the biradical intermediate 4.21 leading to the formation of the aziridines and release of the catalyst (Scheme 4.8). This latter step explains the stereospecificity of the transformation.

Scheme 4.8: Postulated mechanism for stereospecific NH aziridine synthesis.

180 J. L. Jat, M. P. Paudyal, H. Gao, Q. Xu, M. Yousufuddin, D. Devarajan, D. H. Ess, L. Kürti, J. R. Falck, Science, 2014, 343, 6166. 181 D. N. Zalatan, J. Du Bois, Top. Curr. Chem. 2010, 292, 347; C. G. Espino, K. W. Fiori, M. Kim, J. Du Bois, J. Am. Chem. Soc. 2004, 126, 15378.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

A series of conditions based on “classical” strategies such as intramolecular cyclisation of pre-functionalized amino-halides substrates and addition of diazo compounds on protected imines have also been employed for the preparation of NH aziridines. Approaches relying on electrophilic aminating reagents have also been reported.

The first report by Hassner and co-workers detailed the reactivity of β-iodo-azides 4.22 (readily obtained by stereoselective and regioselective additions of iodine azide to substituted alkenes) which react with lithium aluminium hydride (LAH) to give non protected aziridines (Scheme 4.9).183,184 In the second step the azide is reduced to an amino which then undergoes intramolecular nucleophilic substitution to form the three membered rings. However, side- products such as olefins and compound 4.23 may arise from elimination of iodine azide and hydrogenolysis respectively (Scheme 4.9).

Scheme 4.9: Stereospecific synthesis of NH aziridines using β-iodo azide 4.22.

Bottaro employed a different strategy based on the use of an electrophilic aminating reagent, and reported the reaction of O-p-tolylsulphonylhydroxylamine 4.24 with olefins. The reaction proceeds in a stereospecific manner to give NH aziridines from low to high yield (Scheme 4.10).185 The scope and applicability of this procedure was however limited.

Scheme 4.10: Conversion of olefins into aziridines by p-Tolylsulphonylhydroxylamine 4.24.

Based on the same concept Shi published the catalytic aziridination of chalcones 4.25 using as electrophilic source of nitrogen, the highly reactive and hazardous mesityl sulfonyl

182 C. Legault, A. B. Charette, J. Org. Chem. 2003, 68, 7119. 183 A. Hassner, G. J. Matthews, F. W. Fowler, J. Am. Chem. Soc. 1969, 91, 5046. 184 F. W. Fowler, A. Hassner, L. A. Levy, J. Am. Chem. Soc. 1967, 89, 2077.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines hydroxylamine reagent (MSH, 4.26),186 and N-methylmorpholine (NMM, 4.27) as nucleophilic catalyst for the nitrogen transfer (Scheme 4.11).187

Scheme 4.11: Amine promotes aziridination of chalcones.

The reaction starts with the nucleophilic substitution of MSH 4.26 by N-methylmorpholine 4.27 leading to the formation of hydrazinium 4.29 (Scheme 4.12). The deprotonation of aminimine 4.29 by cesium hydroxide forms the aminimide 4.30 which subsequently undergoes conjugated addition to chalcone followed by cyclisation to form NH aziridines.

Scheme 4.12: plausible catalytic cycle for the aziridination of chalcone 4.25.

185 J. C. Bottaro, J. Chem. Soc. Chem. Commun. 1980, 560. 186 a) C. R. Johnson, R. A. Kirchhoff, H. G. Corkins, J. Org. Chem. 1974, 39, 2458; b) Y. Tamura, J. Minamikawa, K. Sumoto, S. Fujii, M. Ikeda, J. Org. Chem. 1973, 38,1239. 187 Y. Shen, M. Zhao, J. Xu, Y Shi, Angew. Chem. Int. Ed. 2006, 45, 8005.

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An enantioselective version of this reaction was also reported using enantiopure Tröger’s base 4.28, the NH aziridine was obtained in good yield (81%) and a promising ee value (55%).37 In the meantime, the group of Amstrong reported the same reaction using O-

(diphenylphosphinyl)hydroxylamine (Dp-pONH2) 4.31 as source of electrophilic nitrogen instead of MSH 4.26 and an enantioselective version of the reaction was also reported with quinine as a substitute to Tröger’s base (Scheme 4.13).188 However lower yields were generally obtained but a similar level of enantioselectivity (ee = 56%) was reached.

Scheme 4.13: Aziridination of chalcone reported by Amstrong and co-workers.

Later, Page and co-workers189 utilized enantiopure binaphthalene based tertiary amines as catalysts for the synthesis of enantioenriched NH aziridines. Aminimine intermediates were characterized. However, a low enantioselectivity (ee = 43%) was reached.

Several groups have also achieved the enantioselective aziridination of α-β unsaturated carbonyl derivatives by mean of organocatalysis. High levels of enantioinduction are reached using proline or cinchona alkaloids based catalysts. 190 Moreover, nitrogen sources bearing a leaving group along with easily deprotectable group such as BOC or Cbz are often used, allowing selective deprotection.

An efficient protocol using hypoiodide as catalyst for the aziridination of styrenes has also been described by the group of De Vos (Scheme 4.14).191 This straightforward method

188 A. Armstrong, C. A. Baxter, S. G. Lamont, A. R. Pape, R. Wincewicz Org. Lett. 2007, 9, 351. 189 P. C. B. Page, C. Bordogna, I. Strutt, Y. Chan, B. R. Buckley, Synlett 2013, 24, 2067. 190 a) Y. Zhu, Q. Wang, R. G. Cornwall, Y. Shi, Chem. Rev. 2014, 114, 8199; b) C. De Fusco, T. Fuoco, G. Croce, A. Lattanzi, Org. Lett. 2012, 14, 4078; c) L. Deiana, P. Dziedzic, G. Zhao, J. Vesely, I. Ibrahem, R. Rios, J. Sun, A. Córdova, Chem. Eur. J. 2011, 17, 7904; d) S. Minakata, Y. Murakami, R. Tsuruoka, S. Kitanaka, M. Komatsu, Chem. Comm. 2008, 6363; E. Murugan, A. Siva, Synthesis 2005, 12, 2022 191 C. Varszegi, M. Ernst, F. van Laar, B. F. Sels, E. Schwab, D. E. De Vos, Angew. Chem., Int. Ed. 2008, 47,1477.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines utilizes micellar iodine and ammonia. The key point of this reaction is the facile oxidation of iodine by NaOCl to generate an iodonium like reagent. This latter is the active species which catalyzes the aziridine formation after an addition-elimination on iodonium cyclopropane 4.32 giving 4.33.

Scheme 4.14: Unprotected aziridines synthesis from styrene and ammonia using micellar iodine.

Finally, Wulff and co-workers reported an enantioselective preparation of NH aziridines based on a two-step procedure (Scheme 4.15).192 First the entioenriched protected aziridines 4.36 (also by product 4.37) are obtained after the reaction between N- dianisylmethylimines (N-DAMimines) 4.34 and ethyl diazoacetate 4.35. This step corresponds to an aza-Darzens reaction between ethyl diazoacetate and imines protected with an easily removed protected group (N-DAMimines). The process is catalyzed by enantiopure VANOL and VAPOL borate catalysts of type 4.40 derived from their corresponding Vaulted Binaphthol 4.38 and Vaulted Biphenanthrol 4.39 ligands respectively (Scheme 4.16).158d,e

Scheme 4.15: Aziridination with borate catalysts derived from Vaulted Binaphthol and Vaulted Biphenanthrol ligands.

This reaction gives access to protected aziridines in good yields (up to 97%) and high ee values (up to 98%). Then the N-DAM aziridines 4.36 are deprotected under acidic conditions

192 Z. Lu, Y. Zhang, W. D. Wulff, J. Am. Chem. Soc. 2007, 129, 7185.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines using trifluoroacetic acid or sulfuric acid, without causing acid-promoted openings of the aza ring.

Scheme 4.16: Synthesis of borate catalysts Derived from Vaulted Binaphthol and Vaulted Biphenanthrol ligands.

Despite the efficiency of some of these procedures, it was conceived that new straightforward methods for the preparation of NH aziridines and sulfoximines were still needed. A mild protocol that would use visible light photoredox chemistry to release the aziridine adduct from N-protected analogous was seem as a particularly interesting alternative.

4.4 Synthesis of Protected Aziridines, Sulfoximines and Sulfimides, using N-Aminoacridinium Salt as Nitrogen Source

4.4.1 Preparation of Protected Aziridines

In fact, for the preparation of NH aziridines, it was decided to use of the previously synthesized acridinium 2.5j (chapter 2) as nitrogen source.193 Considering that after a concerted addition, the chromophore could act as an antenna for a photocleavage process. Also, 2.5j is prepared efficiently in gram scale and isolated by simple filtration in high yield (92%). Furthermore, the straightforward protocol disclosed by the group of Yudin and Che employing PIDA as oxidant was chosen for its practical aspect.172,173 The reaction between acridinium 2.5j and chalcone 4.25a was thus attempted. To our satisfaction, the reaction occurred as planed and the desired aziridine 4.41a was obtained in modest yield. The aziridination reaction was then optimized and generalized. The results are summarized in

Table 4.1. In CH2Cl2 a shorter reaction time is beneficial (entry 2) and, moreover, the reactions are found to be easier to purify. Decreasing both the amount of oxidant PIDA and of

193 For the development of this reaction N-aminophthalimide 4.4 was first considered as nitrogen source, however its photochemical deprotection was not successful.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines the nitrogen source (N-aminoacridinium ion) was also favorable (entries 3 to 7 respectively).

However, increasing the concentration of the reaction was detrimental (entry 6). CH2Cl2 was found to be the better than CH3CN and was kept for further studies.

Table 4.1: Aziridination reaction conditions. Entry Solvent Acridinium[a] PIDA[a] Concentration[b] Time Yield[c]

1 CH2Cl2 1.5 2 0.1 8 h 50%

2 CH2Cl2 1.5 2 0.1 2 h 71%

3 CH2Cl2 1.5 1.1 0.1 2 h 85%

4 CH2Cl2 1.1 1.1 0.1 2 h 90%

5 CH2Cl2 1.05 1.1 0.1 2 h 92%

6 CH2Cl2 1.05 1.1 0.25 2 h 75%

7 CH3CN 1.05 1.1 0.1 2 h 60% [a] number of equivalent, [b] in Mol.l-1, [c] yield of 4.41a is at least an average of 2 reactions

With the optimized conditions in hands (Table 4.1, entry 5) a series of protected aziridines 4.41 were prepared by reacting a variety of alkenes with the combination of 2.5j and PIDA. Pleasingly, in all cases the substrate conversion was quantitative and low to excellent yields for products (4.41a to 4.41n) were obtained. In general, electron poor alkenes such as chalcones reacted smoothly to give the corresponding protected aziridines. Depending on the substitution pattern, yields vary from low (16%) to very high (99%). On average they are superior to 68% (Scheme 4.17, 4.41a to 4.41g). The reason for the low yield of 4.41d is unclear. For 4.41e, a competitive oxidation of the electron ring aromatic might be the reason for the less efficient reaction. More globally, an enhanced reactivity is observed with electron poor substituent (e.g. chalcones 4.25c and 4.25g). This observation would tend to indicate a nucleophilic nature for the in situ generated nitrene.194

194 D. J. Anderson, T. L. Gilchrist, D. C. Horwell, C. W. Rees, J. Chem. Soc. Sect. C, Org. 1970, 4, 576.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Yet, in the presence of magnesium oxide (MgO, 2.4 equiv)195 and longer reaction times (Scheme 4.17, 4.41h to 4.41j), electron rich alkenes such as styrenes 4.42h to 4.42j give also the desired products in excellent yields. The necessity of using MgO for the formation 4.41h, I and j shows the probable instability of these products in acid media (AcOH is generated during the reaction). Interestingly, reactions of trans- and cis-β-methylstyrene gave exclusively trans-4.41i and cis-4.41j aziridines respectively, establishing the stereospecificity of the present protocol.172,173 The parallel in terms of stereochemistry between these results and that of Yudin and Che points towards a mechanism involving, in this case also, a singlet nitrene precursor intermediate. Moreover a concerted addition via a transition state similar to that of Scheme 4.3 (4.10) can be assumed.

Finally, cyclic and acyclic aliphatic alkenes were utilized and they afforded the desired products (Scheme 4.13, 4.41k to 4.41n). Once again MgO was necessary to get these products in high yields. As expected, cis-heptene and trans-hexene yielded stereospecifically cis and trans 4.41m and 4.41n respectively.

195 MgO is the most effective base, has reported by Du Bois for the in situ generation of iminoiodinane reagent for the intramolecular of C-H aminations mediated by Rhodium catalysts, see: C. G. Espino, J. Du Bois, Angew. Chem. Int. Ed. 2001, 40, 598.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Scheme 4.17: Aziridination reaction scope

With these results in hands a few control experiments were performed. The reaction was tried with hydrazines 4.41 and 4.44 and with chalcone 4.25a or styrene 4.42h as substrates. The results are reported in Scheme 4.18. The expected products 4.45 and 4.46 were not formed. In case of 4.41 an intermediate of oxidation could be detected by mass spectrometry. For 4.44 only decomposition was observed.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Scheme 4.18: Chalcone and styrene aziridination with 4.41 and 4.44.

Therefore, the aziridination of olefins with N-aminoacridinium 2.5j is explained by the proposed mechanism depicted in scheme 4.18. The selective oxidation of 2.5j by PIDA 4.7 affords the nitrene precursor N-acetoxyacridinium 4.47. Then, this species undergoes a concerted addition with olefins to yield aziridine of type 4.41.

Scheme 4.19: Proposed mechanism for aziridination reaction.

Compound 4.41a was found to be moderately soluble in a 4:1 mixture of hexane and dichloromethane. Single crystals were obtained that were analyzed by X-ray diffraction (Figure 4.4). As indicated by the 1H NMR (3J = 4.8 Hz) a trans-configuration is observed for the aziridine, indicating a retention of configuration for the reaction. Moreover, as aziridines substituted on the sp3 nitrogen by heteroatoms often display a configurational stability for this

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

N-atom, it is thus necessary to consider its stereochemistry.196 The pendant acridinium group is oriented in cis and trans relationships with the Ph and COPh groups respectively (Figure 4.4). The solid state conformation of 4.41a shows also that the oxygen atom of the keto group points towards the acridinium part of the molecule. This orientation might be the result of a weak interaction between one lone pair of the oxygen atom and the electron poor acridinium 2 part. Indeed, a distance of 2.99 Å was measured between the carbon alpha to the (sp ) N10 and the oxygen of the ketone functional group.

Figure 4.4: Olex 2 view of acridinium 4.41a, top view (left) lateral view (right). One molecule of BF4 ion is omitted for clarity.

Finally, during the screening of the reaction it was found that electron rich styrene derivatives such as the p-methoxy derivative 4.48 react differently and only amino acetoxyl products of addition of type 4.49 were isolated.

4.4.2 Aminoacetoxylation of Electron rich Olefins

This unusual behaviour was investigated. In fact, 1 equivalent p-methoxystyrene 4.48 was oxidized with 1.1 equivalent of PIDA in presence of 1.05 equivalents of N- aminoacridinium 2.5j. Compound 4.49a was isolated in 90% yield (Scheme 4.20). 3,4- Dimethoxystyrene and trans-anethole proceeded in a similar fashion to afford 4.49b and 4.49c in 70 and 85% yields respectively (Scheme 4.20).197

196 Heterocyclic chemistry, 3rd.Ed. T. L. Gilchrist, Pitman, 1997 197 For 4.49b and 4.49c, these are NMR yields using 1,3,5 trimethoxybenzene as internal standard.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Scheme 4.20: Aminoacetoxylation of electron rich styrene with 2.5j.

In the three cases the regioselectivity is excellent with the acetoxy and nitrogen fragments being added to α and β carbons of the styrenes respectively.198 The structure of 4.49a was confirmed by X-ray diffraction (Figure 4.5) and importantly for the mechanism discussion, the N-aminoacridinium ion is linked to the less hindered position while the acetoxy group is attached to the more hindered one. Furthermore, in this product, the acridinium part displays a perfect planar surface and none of the “out-of-plane” phenomenon noticed in some earlier studies was observed,199 showing that this compound is less sterically hindered compared to aziridine products.

Figure 4.5: Aminoacetoxyl product 4.49a, one molecule of BF4 counter ion omitted for clarity.

In term of mechanism, two pathways can be considered. First, an acid-promoted opening of the “expected” aziridine leading to stabilized secondary carbenium ion intermediate 4.50 and product 4.49 of trapping by the acetate counterion (Scheme 4.21, pathway 1). It should be emphasized, in the case of the reaction giving 4.49, the addition of MgO did not change the reactivity and the aminoacetoxyl 4.49 was the major product formed (conversion > 80% in 1H NMR analysis). Second, a preferred oxidation of electron rich 4.49 instead of N-

198 α and β carbons are defined in relation to the styrene nomenclature

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines aminoacridinium ion 2.5j generating hence iodo(III)cyclopropane 4.51 (Scheme 4.21, pathway 2). Then the nucleophilic attack of 2.5j at the more accessible terminal methylene position of 4.51 leads to a regioselective ring opening200 and produce 4.52 after deprotonation of this latter by acetate ion. At this stage two reactions can possibly occur, either an iodine (III) reductive elimination takes place leading to the formation of the product 4.49 and release of iodobenzene or a nucleophilic substitution of the tertiary carbon center by AcO–. Indeed, intermediate 4.52 presents a pronounced electrophilicity at the tertiary carbon center which is a benzylic carbon, α to electrophilic iodine (III) and α to N-aminoacridinium ion.

Scheme 4.21: Proposed mechanism of aminoacetoxyl reaction.

With these results in hand, it was decided to widen the scope of the reaction and determine if other olefins could be aminoacetoxylated. The reaction between acridinium 2.5j and styrene 4.42h was attempted again and the results in the presence of different acids are summarized in Table 4.2. In all cases, the acids were introduced prior to PIDA. Only in the case of trifluoroacetic acid was a positive result obtained (Table 4.2, entry 3). Thus the reaction was directly tested with commercially available Bis(trifluoroacetoxy)iodobenzene (PIFA), which is known to promote aminohydroxylation reactions,201 and as expected the desired product of type 4.49 was obtained in 82% yield.

199 B. Laleu, C. Herse, B. W. Laursen, G. Bernardinelli, J. Lacour, J. Org. Chem. 2003, 68, 6304 200 a) For a related proposal: H. M. Lovick, F. E. Michael, J. Am. Chem. Soc. 2010, 132, 1249; b) G. F. Koser, Top. Curr. Chem. 2000, 208, 137 c) N. S. Zefirov, V. V. Zhdankin, Y. V. Dan’kov, V. D. Sorokin, V. N. Semerikov, A. S. Koz’min, R. Caple, B. A. Berglund, Tetrahedron Lett. 1986, 27, 3971; d) G. F. Koser, L. Rebrovic, R. H. Wettach, J. Org. Chem. 1981, 46, 4324. 201 a) I. Tellitu, S. Serna, M. T. Herrero, I. Moreno, E. Dominguez, SanMartin, R. J. Org. Chem. 2007, 72, 1526; b) A. Correa, I. Tellitu, E. Dominguez, R. SanMartin, J. Org. Chem. 2006, 71, 8316; c) S. Serna, I. Tellitu, E. Dominguez, I. Moreno, R. SanMartin, Org. Lett. 2005, 7, 3073.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines

Table 4.2: Aminoacetoxylation reaction conditions. Entry Additives Equiv Time Yield[a] R 1 AcOH 2 4 h <5% Ac 2 TsOH 2 4 h <10% OTs

3 TFA 2 4 h 80% OCOCF3

4 TFA 0.2 12 h <5% OCOCF3 [b] 5 - 2 4 82% OCOCF3 [a] isolated yields; [b] PIFA used

With these results in hand, care was thus taken to expand the chemistry to other Lewis basic substrates, and sulfoxides and thioethers in particular

4.4.3 Preparation of Protected Sulfoximines and Sulfimides

4.4.3.1 Historical Background

Sulfimides and NH Sulfoximines in particular, are important synthetic targets and useful buildings block in organic synthesis, medicinal chemistry and crop protection, as the resulting products can disclose interesting bioactivities.202 Several procedures have been reported for their making.203 Concisely, an imidating agent is generally transferred directly or by mean of metal catalyst to the sulfur atom giving the corresponding sulfimide or sulfoximine (Figure 4.6). As a general rule, the imidating agents possess a leaving group on the nitrogen atom to be transferred.

202 a) U. Lücking, Angew. Chem. Int. Ed. 2013, 52, 9399; b) G. Siemeister, U. Lücking, A. M. Wengner, P. Lienau, W. Steinke, C. Schatz, D. Mumberg, K. Ziegelbauer, Mol. Cancer Ther. 2012, 11, 2265. 203 V. Bizet, C. M. M. Hendriks, C. Bolm, Chem. Soc. Rev., 2015, 44, 3378.

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Figure 4.6: Imidation of Thioethers and Sulfoxides and common imidating agents used.

Different pathways seem to be at play. They depend on the nature of the reagents that involve either more nucleophilic species (Chloramine T and N-haloamides, 4.53 and 4.54 respectively) or more electrophilic entities (MSH and HOSA, 4.26 and 4.55 respectively). One example of a nucleophilic approach is for instance the reaction of thioether 4.60 with chloramine T 4.53 in presence of AcOH to afford the protected sulfimide 4.61. First 4.60 is transformed into chlorosulfonium 4.62 by electrophilic chlorination. The released tosylamidate 4.63 then undergoes a nucleophilic substitution (SN) and affords protected 4.61 (Scheme 4.22).204

Scheme 4.22: Direct synthesis of protected sulfimides 4.61 using Chloramine T (4.53).

204 K. Tsujihara, N. Furukawa, K. Oae, S. Oae, Bull. Chem.Soc. Jpn. 1969, 42, 2631 and references therein

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As just said, MSH (4.26) and HOSA (4.55) are typical examples of “electrophilic” imidating agents in which the nitrogen atom can be transferred directly to the sulfur as depicted in Scheme 4.23. Some iminoiodinanes (4.56) are also part of this group.205

Scheme 4.23: Sulfimides and Sulfoximines synthesis using electrophilic nitrogen sources.

However, the most used approach counts on the metal-catalyzed addition of electrophilic nitren(oid) species such as organoazides 4.57, heterocyclic nitrene precursors (e.g. 4.58 and 4.59) and in situ generated iminoiodinanes.203 This strategy can also allow the synthesis of sulfoximines and sulfimides in an enantioselective manner. Interestingly, an electrochemical synthesis of sulfoximines was performed by Yudin and co-workers with sulfoxides 4.64 and N-aminophthalimide 4.4 as nitrene precursor (Scheme 4.24). The NH sulfoximines 4.65 were obtained in yields spanning from 48% to 71%, after the subsequent removal of the N-phtalimido group by N–N-cleavage by reductive electrochemistry.206 Yet the scope of the reaction was quite limited.

Scheme 4.24: Electrochemical imination of sulfoxides using N-aminophthalimide 4.4.

In view of the success of 2.5j in the aziridination of olefins, it was decided to test this reagent with thioethers and sulfoxides.207

205 W. Ou, Z.-C. Chen, Synth. Commun. 1999, 29, 4443 206 T. Siu, A. K. Yudin, Org. Lett. 2002, 4, 1839. 207 a) O. García Mancheño, C. Bolm, Org. Lett. 2007, 9, 2951; b) G. Y. Cho, C. Bolm, Tetrahedron Lett. 2005, 46, 8007; c) G. F. Koser, P. B. Kokil, M. Shah, Tetrahedron Lett. 1987, 28, 5431.

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4.4.4 Synthesis of Protected Sulfoximines and Sulfimides using N-aminoacridinium Ion

Slightly modified reaction conditions were developed for the imidation of sulfoxides and the results are gathered in Scheme 4.26. In fact, slightly excess of PIDA was favourable. Typically 1.05 equivalents of 2.5j and 1.2 equivalents of PIDA 4.7 were used for the imination of sulfoxides type 4.64 into their corresponding sulfoximines 4.65. Excellent yields were obtained for substrates bearing aliphatic and/or aryl substituents (91, 85, 97 and 90% for 4.65a, b, c and e respectively). The reaction was also found to be somewhat sensitive to steric hindrance. Product 4.65d bearing diphenyl group was obtained in 70%, while the less sterically hindered derivatives were obtained generally in excellent yields (Scheme 4.26).

Scheme 4.25: Scope of sulfoxides imidation

With 1.05 equivalents of 2.5j, 1.2 equivalents of PIDA 4.7 and MgO as additive four different thioethers 4.60 were converted efficiently into their corresponding sulfimides 4.67 (Scheme 4.26). Satisfactorily, the sulfimides 4.67a to 4.67d were isolated from good to excellent yields (84 to 99%) after 16 h, and the reaction with tetrahydrothiophene as substrate afforded the product 4.67d is nearly quantitative. Once again, MgO was necessary for the getting of the products in good yields.

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Scheme 4.26: Scope of thioethers imidation

It should be emphasized that the reaction of N-aminophthalimide 4.4 with thioether 4.68 to yield protected thioether 4.69 is not effective (10% conversion and 4% yield) as depicted in Scheme 4.27.172 This result highlights the difference in reactivity between N-aminoacridinium 2.5j and 4.60a-d and N-aminophthalimide 4.4 with 4.60e. One can hypothesize that the presence of the acridinium group α to the nitrogen could be responsible for the enhanced reactivity of 2.5j towards Lewis base such as thioethers.208

Scheme 4.27: Thioether 4.68 imidation using N-aminophthalimide 4.4 and PIDA 4.7.

Having established the scope of the reaction and identified sub-products such as aminoacetoxyl 4.49, we could turn our attention on the removal of acridinium group to generate NH aziridines, sulfoximines and sulfimides.

208 Nitrenes and Nitrenium Ions (Ed: D. E. Falvey and A. D. Gudmundsdottir) 2013 John Wiley & Sons, Inc.

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4.5 Stereospecific Synthesis of NH Aziridines and Sulfoximines, Mediated by Visible Light Photoirradiation

For the deprotection of the acridinium fragment from aziridines 4.41 and sulfoximines 4.66 and sulfimides 4.67, the use of a reductive process was identified as the most efficient mean to achieve a selective N-N bond cleavage without affecting others functional group.205 Furthermore, in view of the photophysical209 and photochemical210 properties of N- alkylacridinium ion, and in the context of photoredox chemistry (re)emergence,211 it was perceived that the reduction could be coupled to a photochemical process. As such, acridinium fragment would operate as a photoremovable protecting group.

Photoremovable protecting groups (also known as photolabile protecting groups, phototriggers, or caged molecules) are functional groups that are attached to chemicals in such a way that they render these elements inert to the chemical environment. Exposure to light releases the protecting group, restoring hence the functionality of the compounds. The use of photoremovable protecting groups (PRPGs) allows precise spatial and temporal control of chemical reactions. Such groups have found use in many diverse applications, ranging from time resolved studies of physiological processes, to fabrication of spatially resolved combinatorial libraries of DNA.212 The application of these types of protecting groups to the photochemical release of amines, alcohols, ketones, and carboxylic acids have been intensively reported. Three classes of derivatives are commonly used (Figure 4.7).

Figure 4.7: Some photoremovable protecting groups.

209 a) I.-S. H. Lee, K.-H. Chow, M. M. Kreevoy, J. Am. Chem.Soc. 2002, 124, 7755; b) S. Fukuzumi, K. Ohkubo, T. Suenobu, K. Kato, M. Fujitsuka, O. Ito, J. Am. Chem. Soc. 2001, 123, 8459 210 D. A. Nicewicz, T. M. Nguyen, ACS Catal. 2014, 4, 355; S. Fukuzumi, K. Ohkubo, Chem. Sci. 2013, 4, 561 211 D. M. Schultz, T. P. Yoon, Science 2014, 343, 985; C. K. Prier, D. A. Rankic, D. W. C. MacMillan, Chem. Rev. 2013, 113, 5322; J. M. R. Narayanam, C. R. J. Stephenson, Chem. Soc. Rev. 2011, 40, 102 212 P. Klán, T. Šolomek, C. G. Bochet, A. Blanc, R. Givens, M. Rubina, V. Popik, A. Kostikov, J. Wirz, Chem. Rev. 2013, 113, 119; A. Herrmann, Photochem. Photobiol. Sci. 2012, 11, 446; H. Yu, J. Li, D. Wu, Z. Qiu, Y. Zhang, Chem. Soc. Rev. 2010, 39, 464; J. F. Lovell, T. W. B. Liu, J. Chen, G. Zheng, Chem. Rev. 2010, 110, 2839. N. Hoffmann, Chem. Rev. 2008, 108, 1052;

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Nitrobenzyl and related derivatives of type 4.69, arylcarbomethyl group 4.70 and to a less extent coumarine derivatives 4.71. However, recent research efforts have focused on designing protecting groups that are removed through photoinduced electron transfer (PET), rather than by direct photolysis. The PET strategy allows the light absorption step to be decoupled from the bond breaking step, thus permitting more control over the wavelengths of light used in the release process.213 Nevertheless, to our knowledge high energy light sources (< 400 nm) are generally used for the photorelease step, irrespective to the type of PRPGs utilized. We saw therefore in compound 4.41, 4.66 and 4.67, an opportunity to change this situation. The direct photolysis of two solutions of aziridine 4.41a under argon was thus attempted. The first reaction was performed in CH2Cl2 with a 300 W bulb white light

(conditions a), and the second in a mixture of CH3CN/toluene (2/1), with sunlight (conditions b). While no reaction was seen in the first case, the reaction yielded in the second set of conditions a complex mixture of desired NH aziridine 4.72a, opened product 4.73a ,opened product 4.74a with still protected group and unreacted aziridine 4.41a (Scheme 4.28).

Scheme 4.28: Photolysis of aziridine 4.41a.

This second result prompted us to attempt the N-N bond photocleavage in the presence of electron donor groups such as trialkylamines. With aziridine 4.41a as substrate a variety of amines was thus screened, using a 1 Watt green LED (530 nm) as light source at 25 °C and 0.125 M as concentration (Table 4.3). To our surprise, full conversion was obtained with 1,8- diazabicyclo(5.4.0)undec-7-ene (DBU) after 30 min only, however NH aziridine 4.72a was isolated with a low yield (20%, entry 1). With triethylamine (TEA), the reaction did not

213 a) D. E. Falvey, C. Sundararajan, Photochem. Photobiol. Sci. 2004, 3, 831; b) V. N. R. Pillai, Organic

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines proceed and only the starting 4.41a was recovered (table 4.3, entry 2). With diisopropylethylamine (DIPEA) the desired product was obtained in modest yield after 24h (40%, entry 3); however, satisfactorily, when tetramethylethylene diamine (TMEDA) was employed as electron and proton source the unprotected aziridine 4.72a was obtained in excellent yield (88%, entry 4) after 5 h only. Finally, with 1,4-diazabicyclo(2.2.2)octane (DABCO), the reduced acridine product was isolated (Table 4.3, entry 5), this reactivity being detailed later in the section.

Table 4.3: N-N bond cleavage: reaction conditions. Entry Reducing agent Equiv Time (hours) Conversion Yield[a] 1 DBU 1.1 0.5 100 20 2 TEA 2.2 24 0 0 3 DIPEA 2.2 24 100 40 4 TMEDA 2.2 5 100 88 5 DABCO 2.2 5 100 90[b] [a] isolated yields, [b] reduced acridine isolated

With these optimal conditions in hand (Table 4.3, entry 4) the deprotection of all the derivatives 4.41 was performed. The reaction proceeded well with aziridines derived from regular chalcone 4.72a or those bearing EWG 4.73c and 4.73e. The NH aziridines were obtained in 88, 88 and 90% respectively (Scheme 4.39). Aziridines from chalcones substituted by EDG were isolated in good yields as well (82, 77 and 84% for 4.72b, 4.72d, and 4.72f respectively), however longer reaction times were necessary. This higher reactivity of aziridines bearing EWG is attributed to the greater electron acceptor ability (or greater reduction potential) of these compounds. Somewhat consequently, with the substrates obtained from styrenes derivatives (4.41h and 4.41i) or non-activated alkenes (4.41k, 4.41l, 4.41m and 4.41n) the deprotection did not occur and only reduced acridine derivatives were observed.

Photochemistry, Marcel Dekker, Inc., New-York, 1987, 9; V. N. R. Pillai, Synthesis, 1980, 1.

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Scheme 4.29: Scope of aziridines 4.41 deprotection

In fact, from the reaction of aziridine 4.41l the reduced acridine product 4.73 could be isolated and its structure confirmed by X-ray analysis (Figure 4.8). The compound displays a twisted conformation of the reduced acridine moiety as result of the change of the hybridization of the central carbon from sp2 to sp3. Despite this sterically hindered geometry the product is stable and no re-oxidation of the acridine to the acridinium ion was observed even when compound 4.41l was exposed to light.

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Figure 4.8: Reduced acridine product 4.73 carrying cis cyclooctene.

Clearly, if EWG are not present at proximity of the aziridine nitrogen atom (as in the case of chalcones) the photoactivated process induces only the reduction of the acridine rather than the N-N bond cleavage. Therefore, it was hypothesized that a Lewis acid would be beneficial. The formation of a dative bond would render the N-aziridine atom more electrofugal and should activate the N-N bond cleavage. Different Lewis acids were therefore tested as shown in Table 4.4.214 Only

B(C6F5)3 gave the expected product after 48 h (Table 4.4 entry 3). With other Lewis acids, only the starting material was recovered. Moreover, changing the light source (from 530 to 405 nm 1 W, LED) decreased considerably the reaction time from 48 to 10 h (Table 4.4, entry 4).

Table 4.4: Aziridines reductive deprotection using Lewis acid. Entry Reagents Equiv Conversion Time λ (nm)

1 Cu(OTf)2 0.2 0 48 h 520

2 Sc(OTf)3 0.2 0 48 h 520

3 B(C6F5)3 0.2 100 48 h 520

4 B(C6F5)3 0.2 100 10 h 405

214 I. D. G. Watson, A. K. Yudin, J. Org. Chem. 2003, 68, 5160

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With these optimal conditions (Table 4.4, entry 4), the photoreductive N-N bond cleavage of compounds 4.41h to 4.41n was attempted. It was highly successful but free aziridines were difficult to isolate due to their polar nature. As such, for practical reasons, a lipophilic protecting group was introduced, and Cbz was selected as it can be recleaved selectively and afford the NH aziridines quantitatively.215 These moieties 4.72i to 4.72l were isolated in good yields, from 82 to 95 % (Scheme 4.30). However, to our surprise aziridines 4.41h and 4.41i derived from styrene derivatives could not be isolated. A decomposition of the corresponding NH aziridines was observed, even upon Cbz protection. One explanation for this decomposition could be the acid promoted ring 214,216 opening of aziridine, which is catalysed by Lewis acids such as B(C6F5)3.

Scheme 4.30: Scope of aziridines 4.41 deprotection (continued)

In view of the success of aziridine 4.41 photoreductive cleavage, it was decided to test the N-N bond cleavage of sulfoximines and sulfimides derivatives 4.66 and 4.67 respectively,

215 Protecting groups, P. J. Kocienski, 3rd edition, 2005 216 a) J. A. Kalow, D. E. Schmitt, A. G. Doyle, J. Org. Chem. 2012, 77, 4177; b) E. B. Rowland, G. B. Rowland, E. Rivera-Otero, J. C. Antilla, J. Am. Chem. Soc. 2007, 129, 12084

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines with the optimal conditions depicted in Table 4.3, entry 4. The reaction proceeded well and NH sulfoximines 4.65a to 4.65d were obtained from 78 to 90%.

Scheme 4.31: Scope of sulfoximines and sulfimides deprotection

Then, the deprotection of the sulfimides compounds 4.67 was attempted with TMEDA (2.2 equiv) as reductant and a green LED (530 nm) as light source. In all the cases the reaction did not proceed and only the unreacted sulfimides were recovered. Consequently, it was decided to activate the N-N bond by using B(C6F5)3 as in the case of non-activated aziridines 4.41i to 4.41n (vide supra), and the conditions depicted in Table 4.4, entry 4 were employed. The N-N bond cleavage did successfully proceed and the products 4.74b to 4.74d could be detected in the crude 1H NMR analysis. However, due to the unstable nature of alkyl substituted NH sulfimides their isolation was impossible. The protection of NH sulfimides products with Bz or Cbz groups was attempted, but this strategy was also unsuccessful. Only in the case of 4.74c the product was stable enough to allow its isolation in 78% yield (Scheme 4.31).

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Scheme 4.32: Scope of sulfimides 4.67 deprotection

Having established the scope of this reaction, we turned our attention on the mechanism of the N-N bond cleavage. To get some insight for this facile photoreductive process, it was decided to examine the nature of the interaction between the acridinium fragment and trialkylamine reagents. Solutions of 1 equivalent of 4.41a with 1.1 equivalent of trialkylamine such as TMEDA, DABCO, TEA, DIPEA and DBU, in CH2Cl2 were prepared and the optical absorption recorded. While in the cases of TMEDA, DABCO, TEA and DIPEA no variations of the UV spectrum was observed, a strong bathochromic shift of the lower transition bands of 4.41a (from 575 and 525 nm to 650 and 595 nm respectively), along with a hyperchromism of the band at 400 nm were noticed when employing DBU (Figure 4.9). Such behaviour is typical of an EDA complex. This type of complex is characterized by the appearance of a weak absorption band, the charge-transfer band, associated with an electron transfer (ET) transition from donor to acceptor.217,218 Nevertheless, the absence of noticeable EDA complexes with the other trialkylamines could be due to the lower ionization potential of these alkylamines leading to weaker n-π* interactions.219 Another reason can be

217 S. V. Rosokha, J. K.Kochi, Acc. Chem. Res. 2008, 41,641. 218 For interaction of aliphatic amines with dinitrobenzenes see: Can. J. Chem. 1985, 63, 903 For recent development of EDA complex in organic chemistry see: a) M. Silvi, E. Arceo, I. D. Jurberg, C. Cassani, P. Melchiorre, J. Am. Chem. Soc. 2015, 137, 6120; b) Ł. Woźniak, J. J. Murphy, P. Melchiorre, J. Am. Chem. Soc. 2015, 137, 5678; c) S. R. Kandukuri, A. Bahamonde, I. Chatterjee, I. D. Jurberg, E. C. Escudero- Adán, P. Melchiorre, Angew. Chem. Int. Ed. 2015, 54, 1485; d) E. Arceo, A. Bahamonde, G. Bergonzini, P. Melchiorre, Chem. Sci. 2014, 5, 2438; e) E. Arceo, I.D. Jurberg, A. Álvarez-Fernández, P. Melchiorre, Nat. Chem. 2013, 5, 750 219 Lindsay Smith, J. R.; Masheder, D. Amine Oxidation. Part IX. The Electrochemical Oxidation of Some Tertiary Amines: The Effect of Structure on Reactivity. J. Chem. Soc., Perkin Trans. 2 1976, 47.

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Chapter 4: N-Aminoacridinium Ion as Nitrogen Source for the Synthesis of Unprotected Aziridines and Sulfoximines the fast reverse electron transfer (ET) characterizing this complex and which restores the ground state.213

ε

4.41a 4.41a+ DBU

Figure 4.9: Optical absorption spectra acquired in dichloromethane in 1 cm path quartz cuvettes: [4.41a] = 1.10-5 -5 ___ -5 M (pink °°°°°); [DBU] = 1.10 M (black ); [4.41a+DBU] = 1.10 M (green ˟˟˟˟); at 25 °C.

Having characterized the EDA complex, the photocleavage of aziridine 4.41a was attempted with 1.1 equivalent of DBU, using a 1 Watt green LED (530 nm) as light source at 25 °C and 0.3 M as concentration (Scheme 4.33). The corresponding NH aziridine 4.72a was obtained in a lower yield of 27%. Increasing the concentration of the reaction to 0.5 M, or the temperature to 40 °C did not improve the yield. This observation is suggestive of the existence of a photoresponsive EDA mechanism; however, this process might not be the major pathway. Such behaviour has been recently exemplified.220

Scheme 4.33: Photoreductive deprotection of 4.41a derivatives at 617 nm with DBU.

This result prompted us to examine the stereospecificity of N-N bond cleavage. Both imidation and subsequent photoreductive cleavage of the enantiopure (+)-(R)-tolylsulfoxide

220 Y. Zhu, L. Zhang, S. Luo, J. Am. Chem. Soc. 2014, 136, 14642.

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4.64b was performed (Scheme 4.34). The deprotection of 4.66b affording tolylsulfoximine (– )-4.65b in good yield (70%). The results of both reactions were followed by optical rotation measurement and by CSP-HPLC analyses for the imination process. The chromatographic traces being compared to that of the racemic derivatives. Satisfactorily, both processes occur with complete enantiospecificity (es > 98%). While the configuration of the acridinium intermediate is unknown, that of product (–)-4.65b has been established to be (R). This indicates a global retention of configuration.221,222

Scheme 4.34: Stereospecific synthesis of (R)-(–)-tolylsulfoximine 4.65b

Finally, the origin of the proton source was surveyed. In fact, recently, Wang and co- workers reported the α-photoalkylation of nitro derivatives of type 4.75 using TMEDA under 223 Ru(bpy)3Cl2 photocatalysis (Scheme 4.35). The reaction was successfully achieved by the trapping of electrophilic iminium ion 4.77 which is generated after the C-C bond cleavage of oxidized TMEDA 4.76.

Scheme 4.35: Visible light promotes C-C bond cleavage.

221 a) H. Okamura, C. Bolm, Org. Lett. 2004, 6, 1305; b) C. R. Johnson, R. A. Kirchhoff, H. G. Corkins, J. Org. Chem. 1974, 39, 2458. 222 25 The specific rotation value obtained for 4.65b in acetone is closed to that of the reported compound, [α] 589 = 25 –24.3 (with C = 0.144) vs [α] 589 = –31.9 ; (with C = 3, for reported compound see 221b). 223 S. Cai, X. Zhao, X. Wang, Q. Liu, Z. Li, D. Z. Wang, Angew. Chem. Int. Ed. 2012, 51, 8050.

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The photoreductive N-N bond cleavage of 4.41a and 4.66a were thus attempted with distilled

TMEDA and deuterated dichloromethane (CD2Cl2) as solvent, for 10 h. The protonated 4.72a and 4.65c products were isolated in 85 and 88% yields respectively (Scheme 4.36). This reaction unambiguously demonstrates that the proton does not come from the solvent. TMEDA is then the likely proton source of it.

Scheme 4.36: Deprotection of 4.41a and 4.66c in CD2Cl2.

With all this information in hand a mechanism for the reductive deprotection of aziridines and sulfoximines is proposed in Scheme 4.37. The reaction starts with the excitation of the acridinium group of compound 4.41 affording after intramolecular charge transfer a highly oxidizing species 4.79.224 This intermediate 4.79 can abstract one electron from TMEDA and then a proton to afford intermediate 4.80.225 At this stage a second molecule of TMEDA (or the radical generated from TMEDA) can readily be oxidized to form the intermediate 4.81 which undergoes N-N bond cleavage and aziridine NH release. However a second pathway involving the direct N-N bond cleavage of 4.80 can also be considered Scheme 4.38. This will afford the acridine 4.82 and NH aziridine aminyl radical 4.83.226 This reactive intermediate 4.83 can oxidize a second molecule of TMEDA (or the radical generated from TMEDA) affording hence unprotected aziridine of type 4.72.

224 S. Fukuzumi, H. Kotani, K. Ohkubo, S. Ogo, N. V. Tkachenko, H. Lemmetyinen, J. Am. Chem. Soc. 2004, 126, 1600; b) H. Kotani, K. Ohkubo, S. Fukuzumi, J. Am. Chem. Soc. 2004, 126, 15999 225 R. S. Andrews, J. J. Becker, M. R. Gagné, Angew. Chem. Int. Ed. 2010, 49, 7274 226 a) J. Hioe, D. Šakić, V. Vrček, H. Zipse, Org. Biomol. Chem. 2015, 13, 157; b) W. C. Danen, F. A. Neugebauer, Angew. Chem. Int. Ed. 1975, 14, 783

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Scheme 4.37: Proposed mechanism for aziridines and sulfoximines deprotection (1st pathway).

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Scheme 4.38: Proposed mechanism for aziridines and sulfoximines deprotection (2nd pathway).

Finally, the reaction of acridine 4.82 with electrophilic nitrogen such as MSH 4.26 186a and dinitrophenyl hydroxylamine 4.84 186b were attempted to regenerate 2.5j (Scheme 4.39). Acridinium 2.5j was formed in each case, however with MSH higher conversion (50%) along with a shorter reaction time were observed.

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Scheme 4.39: Recycling of acridine 4.82.

In conclusion a novel two-step protocol for the synthesis of NH aziridines and sulfoximines has been developed. This procedure is based on the use of N-aminoacridinium ion 2.5j as new nitrene precursor for the stereospecific aziridination of alkenes and imidation of sulfoxides and thioethers. After the addition, the acridine group is cleaved under mild conditions using visible light irradiation. This photoreductive deprotection affords a variety of NH aziridines and sulfoximines in high yields. A mechanism of the nitrogen-nitrogen bond cleavage is proposed as the oxidation of TMEDA by the photoexcited acridinium fragment has been identified as the main pathway of this reaction. Furthermore preliminary studies show the possibility of recycling the acridine product 4.82 and that the two steps can be combined in a one-pot process (Scheme 4.39).

Scheme 4.40: One pot, two-step synthesis of NH aziridine 4.72a.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Chapter 5: Synthesis and Properties of Chiral pH- Sensitive Quinacridines, BODIPY-like and Azobenzene Fluorophores.

In this chapter, the previously synthesized quinacridine of type 2.4e is used as scaffold for the development of new chiral fluorophores. For this moiety and more generally for a DMQA salt of type [1.43][BF4], it is shown that peripheral functionalization can be achieved through electrophilic aromatic substitutions reactions. These substituted derivatives were studied as such or further derivatized to afford helicenes with pH-switchable optical and chiroptical properties, and BODIPY-like and azobenzene dyes in particular. Preliminary results about the synthesis and (chir)optical properties of these fluorophores are presented. All the studies related to the fluorescence of these derivatives have been achieved in collaboration with Christophe Nançoz from Prof. Eric Vauthey’s group (University of Geneva)

5.1 Preamble

In chapter 2, the synthesis and photophysical properties of chiral, fluorescent and pH- sensitive diaza[4]helicenes of type 2.4 were presented, as a reminder compounds of type 2.4 are prepared in two steps only from a common precursor. The (M) and (P) enantiomers can be ‡ separated on CSP-HPLC and are highly configurationally stable (ΔGracem > 30.7 ± 4.0 kcal·mol-1 at 140 °C). These derivatives are effective dyes absorbing light in the visible region

(λabs = 560-620 nm) and their well-separated optical (absorption and emission) and chiroptical (specific optical rotation (OR) and ECD) properties can thus be modulated as a function of the -3 pH. However, these compounds are weak emitters (ΦF = 5·10 ) presenting low values of fluorescence lifetime (τf = 0.45 ns) due, most probably, to intermolecular hydrogen bonding interactions with solvent molecules that provoke a fluorescence quenching.227 In this context, to upset this situation, we wondered whether simple modifications or transformations could be made to these derivatives and generate dimethoxyquinacridines with high fluorescence (quantum yield and lifetime) and chiroptical properties.

227 O. Kel, P. Sherin, N. Mehanna, B. Laleu, J. Lacour, E. Vauthey, Photochem. Photobiol Sci 2012, 11, 623.

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However, in term of reactivity, DMQAs of type 1.43 are highly stable carbenium ions + 228 (pKR ~ 19). In fact, only few reports have discussed about the additions of nucleophiles to the central carbon of DMQA 1.43.229 Interestingly, the electrophilic nature of this site can be rendered nucleophilic by an umpolung strategy.230 However to our knowledge, there has been so far no report on the regio and chemoselective peripheral functionalization of DMQA+. The exact reason for this lack of precedents is unknown. One can hypothesized that the treatment of these cationic aromatic derivatives with electrophiles in the hope of realizing selective substitution reactions is counterintuitive. This should however not be the case as DMQA+, DAOTA+ and TATA+ are rather electron rich “aromatic” derivatives (see Figure 1.9).231

5.2 Electrophilic Functionalizations of Symmetrical DMQAs

(preliminary results)

Care was thus taken to investigate the reactions of DMQAs with electrophilic moieties under classical SEAr conditions. The first attempts were not completely promising. In fact when 1.43 was submitted to bromination or chlorination conditions using halogenating reagents like

NBS, Br2 or NCS respectively, reactivity was observed but complex mixtures of unreacted starting material and monohalogenated products (3 regioisomers) were obtained (Scheme 5.1). Under more forcing conditions, in the presence of Lewis acid for instance, the halogenations proceeded further and the occurrence of polysubstituted derivatives was monitored in mass spectrometry for example.232

Scheme 5.1: Bromination and chlorination of DMQAs 1.43 using NBS and NCS, respectively.

228 a) B. W. Laursen, F. C. Krebs, Chem. Eur. J., 2001, 7, 1773; b) B. W. Laursen, F. C. Krebs, Angew. Chem., Int. Ed. 2000, 39, 3432 229 J. Guin, C. Besnard, P. Pattison, J. Lacour, Chem. Sci. 2011, 2, 425. 230 D. Conreaux, N. Mehanna, C. Herse, J. Lacour, J. Org. Chem. 2011, 76, 2716 231 J. Bosson, J. Gouin, J. Lacour, Chem. Soc. Rev. 2014, 43, 2824 232 A. Wallabregue, J. Lacour, unpublished results.

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To avoid this unexpectedly high reactivity of the DMQAs, it was decided to introduce strong electron-withdrawing substituents such as NO2 or CHO groups instead of halogens; their presence after the first substitution reaction should normally deactivate the core structure and avoiding further reactions.

This was the case upon treatment of 1.43 with HNO3 (biphasic conditions, CH2Cl2) or

DMF/POCl3 which led to the products of mono nitration (5.1) and formylation (5.2) in high yields 99 and 85% respectively (Scheme 5.2). To our satisfaction, the regioselectivity is perfect with these two reactions as the NO2 and the CHO groups are introduced only at the position 5. Currently compounds 5.1 and 5.2 are being further derivatized and a large family of substituents directly attached to the core structure is available (Scheme 5.2). This is however the topic of another PhD thesis and it will not be further discussed.

Scheme 5.2: Functionalization of DMQA+ 1.43.

The peripheral introduction of the two functional groups break the C2 symmetry of DMQA+ 1.43 but more importantly, their presence seem to modify the solution conformation of the adjacent aliphatic side chain. In fact, the terminal CH2 and CH3 groups of the propyl residue next to the introduced substituents are strongly shifted toward lower frequencies (from

1.25 to 0.4 and 2.25 to 1.65 ppm for the CH3 and CH2 groups respectively, Figure 5.1). This shielding tends to indicate that the side chain is fold on the top of the aromatic core instead of assuming an all anti-conformation.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Figure 5.1: 1H NMR spectra of DMQA+ 1.43 (up) and 5.2 (bottom).

Also importantly, these groups strongly improve the photophysical properties of these substituted dyes. Significant changes are observed in their absorption spectra as illustrated in Figure 5.2. For both 5.1 and 5.2, the low-energy absorption bands display both hypsochromic and hyperchromic shifts compared to DMQA 1.43. Furthermore, a strong increase of their emission properties was also evidenced (ΦF = 40 and 42% and τf = 14.5 and 16.2 ns for 5.1 233 and 5.2 respectively, vs 7% and 5.5 ns for 1.43, in CH3CN).

233 A. Wallabregue, I. Hernandez, C. Nançoz, E. Vauthey, J. Lacour, manuscript in preparation.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

1

-

Cm

1

-

/ L M L / ε

___ -5 Figure 5.2: Absorption spectra of DMQA 1.43 ( ), 5.1 (˟˟˟˟) and 5.2 (°°°°°). Solutions in CH3CN, C = 5.10 M.

Consequently, it was decided to use this functionalization approach, and the nitration and formylation in particular, to enhance the optical properties of quinacridines 2.4. It was hypothesized that the electrophilic reactions would occur at the more activated and less sterically hindered position that is the position 5 applying for 2.4 the same numbering as for DMQA+ 1.43 (Figure 5.3).234 Also the proximity of the EWG to the unsubstituted nitrogen atom should generate more acidic pH-sensitive dyes (lower pKa values).

Figure 5.3: Activated positions of quinacridine of type 2.4•H+.

This idea was supported by the similarities observed between the regular DMQA+ 1.43 and quinacridinium 2.4•H+. It has been shown in chapter 2 that these two compounds display comparable absorption and ECD spectra. Moreover calculations performed in collaboration with Mr. Pau Moneva and Dr. Amalia Isabel Poblador-Bahamonde have revealed that these derivatives have similar HOMO and LUMO distributions (Figure 5.4).235 It is thus assumed

234 For 2.4 the substituent 1 is the methoxy group of the aromatic unit linked to the unsubstituted nitrogen 235 P. Moneva, C. Beuchat, A. I. Poblador-Bahamonde, Unpublished results

105

Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores that 1.43 and 2.4e•H+ exhibit the same electronic features and it can be postulated that quinacridinium 2.4e•H+ should have an analogous reactivity towards electrophiles than DMQA+ 1.43.

HOMO LUMO

HOMO LUMO

Figure 5.4: Representation of HOMO and LUMO of DMQA+ 1.43 (up) and quinacridinium 2.4e•H+ (bottom). Blue and green colours correspond to positive parts of the orbital, whereas red and orange colours correspond to negative parts.

5.3 Functionalization of Quinacridine 2.4e

Using compound 2.4e•H+ (R = Ph, chapter 2) as substrate, several electrophiles were tested and the results are gathered in Scheme 5.2. The biphasic nitration reaction was realized utilizing a 1:1 biphasic mixture of nitric acid (HNO3, 60%) and CH2Cl2. This reaction gave the corresponding nitrated quinacridine 5.3 in excellent yield (96%) after 9 minutes only (Scheme 5.3). It is noteworthy that the biphasic conditions are essential to the efficient and clean formation of product 5.3. In fact, when the reaction was performed by adding HNO3 (60%) only, a complex mixture of mono, bis-functionalized products plus (not isolated) overoxidized compounds was formed.236

236 For polynitration of [4]helicenes see: a) H. Okubo, D. Nakano, M. Yamaguchi, C. Kabuto, Chem. Lett. 2000, 1316; b) H. Okubo, D. Nakano, S. Anzai, M. Yamaguchi, J. Org. Chem. 2001, 66, 557.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Scheme 5.3: Electrophilic aromatic substitution of 2.4e•H+.

Satisfactorily, a formyl group could also be installed via a Vilsmeier-Haack reaction using the conditions depicted in Scheme 5.3. To be successful, the stoichiometry of the reaction had to be reversed compared to the original procedure (sub stoichiometric amount of 237 POCl3 or (COCl)2 and excess of DMF). These conditions afforded 85% of product. Recently, it was shown that performing the reaction at 50 °C instead of 90 °C produces less side-products. In fact, at 90 °C, the reaction always generates between 5 to 10% of diformylated derivatives (depending on the reaction scale) which can be difficult to separate from 5.4. Furthermore, this reaction is sensitive to steric and electronic factors. With quinacridines bearing either electron rich (p-NH2C6H5) or less bulky (propyl) substituents, such as 5.5 and 5.6 respectively, polyfunctionalized products are formed preferentially (Scheme 5.4). As such, the reaction is well-behaved only with 2.4e (R= Ph). Further studies will have to be performed to develop more robust and general conditions.

Scheme 5.4: Formylation of quinacridine 5.5 and 5.6.

237 a) S. Ushijima, H. Togo, Synlett, 2010, 1067; b) A. I. Mikhaleva, A. V. Ivanoc, E. V. Skital'tseva, I. A. Ushakov, A. M. Vasil'tsov, B. A. Trofimov, Synthesis, 2009, 587

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Finally, diazonium salts of type 5.7238 (eq. 5.1) obtained by the reaction of anilines with sodium nitrite (NaNO2) in presence of tetrafluoroboric acid (HBF4) were tested. The reaction afforded product 5.8 in 57% yields (Scheme 5.5). This moderate yield can be rationalized by a competitive and facile one electron reduction of the diazonium reagent. In 239 240 fact diazonium salts are known to be readily reduced (Ered = - 0.1 V vs SCE in CH3CN). + The presence of electron rich compounds such as quinacridines 2.4e•H (Eox = +1.32 V vs Fc) can thus favor this side reaction by electron transfer. Furthermore, this yield of 57% was obtained after running the reaction in the dark and adding the diazonium salt in three portions. Generating the diazonium moiety by reacting regular aniline with tert-butyl isonitrite and using it without isolation did not improve the yield.

Equation 5.1: Preparation of diazonium 5.7

Scheme 5.5: Diazonium salt synthesis and diazonium coupling.

All these products display interesting and unique optical features which will be presented separately in the next sections.

5.4 Synthesis of pH-Sensitive and (Chir)Optical Switch Quinacridine

Molecular switches in which optical and chiroptical properties (electronic absorption and emission, OR and ECD) can be tuned as function of the pH are interesting derivatives.

238 For the preparation of diazonium salt :D.P. Hari, P. Schroll, B. König, J. Am. Chem. Soc. 2012, 134, 2958 239 a) S. Milanesi, M. Fagnoni, A. Albini, J. Org. Chem. 2005, 70, 603; b) P. Allongue, M. Delamar, B. Desbat, O. Fagebaume, R. Hitmi, J. Pinson, J.-M. Saveant, J. Am. Chem. Soc.1997, 119, 201; c) C. Galli, Chem. Rev. 1988, 88, 765. 240 H. Cano-Yelo, A. Deronzier, J. Chem. Soc., Perkin Trans. 2 1984, 1093.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Recently, helicenes of type 5.10 displaying acid/base switchable ECD, luminescence and circularly polarized luminescence (CPL) have been reported (Figure 5.5).241 These compounds and their corresponding cycloplatined complexes 5.11 have demonstrated reversible modification of their ECD and OR values upon protonation.242 However, like the majority of azahelicenes, these compounds exhibit near UV absorption and emission properties. As a consequence, helicenes that would display pH-switchable (chir)optical properties in the far red or near infrared (NIR) parts of the light spectrum would be a new development and of great interest.

Figure 5.5: Acid/base triggers switching of ECD and CPL of azahelicene 5.10 and its cycloplatined complex 5.11.

Care was thus taken to study the properties of compound 5.3. It was found that the introduction of the nitro group induced strong changes in the absorption spectrum as remarked for DMQA+ 1.43. Figure 5.6 shows that the lowest energy transition bands (625 and 580 nm) are shifted to lower wavelengths (560 and 525 nm, hypsochromism) with stronger absorption coefficients (hyperchromism) ε = 18000 and 13000 M-1 cm-1 respectively. Moreover, the higher energetic band at 425 nm reveals the strongest absorption coefficient (ε = 32000 M- 1cm-1). Besides these changes, 5.3 displays also spectral changes as function of the pH and the steady-state absorption of neutral quinacridine 5.3 and protonated quinacridinium 5.3•H+ forms are shown in Figure 5.6, along with that of compound 2.4e•H+ for comparison. Clearly,

241 E. Anger, M. Srebo, N. Vanthuyne, C. Roussel, L. Toupet, J. Autschbach, R. Réau, J. Crassous, Chem. Commun. 2014, 50, 2854. 242 N. Saleh, B. Moore II, M. Srebo, N. Vanthuyne, L. Toupet, J. A. G. Williams, C. Roussel, K. K. Deol, G. Muller, J. Autschbach, J. Crassous, Chem. Eur. J. 2015, 21, 1673

109

Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores the protonation affects the electronic structure of 5.3 and it leads to significant changes in its absorption spectrum. From 5.3 to 5.3•H+ the lowest energy bands are shifted to longer

wavelengths and the band center at 425 nm displays hyperchromism.

1

-

Cm

1 -

/ L M L / 5.3e•H+ ε 5.3e 2.4e•H+

___ + Figure 5.6: Protonated (°°°°°), neutral (˟˟˟˟) forms of quinacridine 5.3 and ( ) of quinacridinium 2.4e•H . -5 Solutions in CH3CN, C = 5.10 M.

More importantly, quinacridine 5.3 fluoresces weakly above 600 nm with a quantum yield

(ΦF) of 2% in CH3CN (Table 5.1) while, upon protonation, the conjugate quinacridinium 5.3•H+ exhibits a strong fluorescence at 606 nm with a quantum yield of 22% (Table 5.1). The reasons of this enhancement will be later discussed in this section.

Table 5.1. Fluorescence properties of 5.3 and 5.3•H+. [a] Product pH ΦF τf 5.3•H+ 2.8 22 10.5 5.3 10 2 5.2 [a] fluorescence quantum yield using cresyl violet as reference (error: ±10)

A pH titration was performed. As the absorption spectra of the neutral and cationic forms of 5.3 partially overlap, the pH-dependence was monitored using the fluorescence emission at 606 nm (Figure 5.7). The titration curve was analyzed assuming one acid-base + equilibrium for 5.3/5.3•H (eq. 5.2). More especially, we used equation 5.2 in which Em is the emission intensity of protonated quinacridinium at 606 nm.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Equation 5.2: Equation used for the determination of the pKa of quinacridinium 5.3•H+.

A pKa value of 7.1 ± 0.1 was found for the equilibrium between quinacridinium 5.3•H+ and quinacridine 5.3. It is quite lower than for the unsubstituted 2.4•H+/2.4 (8.95). The nitration functionalization thus affects strongly the basic chemical properties of the helicene.

Figure 5.7: Electronic fluorescence spectra and titration curve recorded with buffered solution (2.5 mM boric acid, citric acid, NaH2PO4) solutions of 5.3 (left and right, respectively). The solid line (right) is the best fit of equation (5.2)

To study the chiroptical properties of the new pH-sensitive derivative 5.3•H+ and 5.3, it was however necessary to step back and perform first a resolution of the precursor 2.4e which had so far been utilized in racemic form only. Successful conditions were found using a Chiralpak IC® column and, as eluent, a mixture of n-hexane, isopropanol (20:80) with 0.1% of ethanolamine as additive to maintain 2.4e in its neutral form. Starting from 110 mg of rac- 2.4e and after several runs (see the experimental part), 50 mg (ee > 99%, 46% yield) and 47 mg (ee 99%, 43% yield) were afforded for the first and second eluted fractions corresponding to the dextrorotatory and levorotatory enantiomers of 2.4e respectively. The specific optical + + rotation of the conjugate quinacridinium (P)-(+)-[2.4e•H ][BF4] and (M)-(–)-[2.4e•H ][BF4] 20 -6 -1 were measured ([α] 365 = +11000 and –9400 respectively, in CH3CN, 4.92 10 g.ml ). The electronic circular dichroism (ECD) spectra of the two fractions (+)-2.4e and (–)-2.4e are

111

Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores virtually superposable to that of (P)-and (M)-2.4f respectively, allowing a facile determination of the absolute configuration for 2.4e.

The nitration was then performed on enantiopure quinacridinium (P)-(+)- + + [2.4e•H ][BF4] and (M)-(–)-[2.4e•H ][BF4] to afford the corresponding protonated (P)-(+) and + 20 -6 (M)-(–) quinacridinium [5.3•H ][BF4] ([α] 365 = +30300 and –30000, in CH3CN, 5.37 10 g.ml-1) in 50 and 40% yields respectively (Scheme 5.6).243 Upon basification, a small decrease in the intensity of the specific optical rotation of conjugate quinacridine (P)-(+)-5.3 and (M)-(– 20 )-5.3 was noticed [α] 365 +25300 and –24400 respectively (Scheme 5.6).

Scheme 5.6: Nitration of enantiopure quinacridine 2.4•H+.

The ECD spectra of cationic and neutral (+)-(P) and (–)-M quinacridine 5.3 were then recorded (Figure 5.8). As it can be noticed, the spectra of the two enantiomers display perfect mirror image and four Cotton effects are noticeable. The transitions are predominantly observed in high energy UV domain of the light spectrum or close to it, at 290, 305 345 and 425 nm. Not surprisingly, protonation and deprotonation processes induce strong modifications in the CD spectra. This process is perfectly reversible and repeatable. In fact, shifts of Cotton effects and increase of Δε are clearly observed upon protonation of 5.3 to cationic 5.3•H+ (Figure 5.8). Besides these changes at 290 mm, an inversion of Cotton effect -1 -1 is observed. For instance, for (+)-(P)-5.3 the Δε value changes from +5 to –30 M cm upon

243 In this and other peripheral functionalizations, a retention of configuration is assumed (M gives M and P gives P) when enantiopure helicenes are utilized.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores acidification. Similar behaviour has been reported recently by Teplý and co-workers.244 In general, all these changes are attributed to a modification of the electronic distribution in the helical scaffold (extension of π system) and to the stiffness of the molecule upon protonation. To complete this chiroptical study the circularly polarized luminescence (CPL) activity of 5.3 will be perform in collaboration with Prof Lorenzo Di Bari from the University of Pisa.

Δε

+ ____ + Figure 5.8: ECD spectra of (P)-(+)-[5.3•H ][BF4] ( ) and (M)-(–)-[5.3•H ][BF4] (- - -); and of (P)-(+)-5.3

-5 (°°°°°) and (M)-(–)-5.3 (˟˟˟˟˟). Solutions in CH3CN, 20 °C, C = 1·10 M.

Finally, it was decided to examine in more details the fluorescence enhancement resulting from the pH diminution. Clearly, upon protonation, a modification of the chemical behaviour of the excited state occurs. Due to the proximity of the unsubstituted nitrogen atom and the introduced NO2, an intramolecular hydrogen bond can be hypothesized between these two groups (Figure 5.9). Such an interaction would restrict the rotation of the NO2. As a consequence of this H-bonded conformation, non-radiative deactivation processes are reduced. Consequently, in the absence of it, facile rotation around the C-NO2 bond occurs and this is responsible of the non-fluorescence of quinacridine 5.3.245

244 P. E. Reyes-Gutiérrez, M. Jirásek, L. Severa, P. Novotná, D. Koval, P. Sázelová, J. Vávra, A. Meyer, I. Císařová, D. Šaman, R. Pohl, P. Štěpánek, P. Slavíček, B. J. Coe, M. Hájek, V. Kašička, M. Urbanová, F. Teplý, Chem. Commun. 2015, 51, 1583 245 At this stage of the study, a photoinduced electron transfer process mediated by the NO2 and inducing a fluorescence quenching of quinacridine 5.3 can also be considered, for recent example see: T. Ueno, Y. Urano, H. Kojima, T. Nagano, J. Am. Chem. Soc. 2006, 128, 10640.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Figure 5.9: 5.3•H+ and 5.3 and their corresponding photo after excitation at 365 nm.

This hypothesis is supported by a recent literature example,246 and by quantum chemical calculations performed in collaboration with Mr. Pau Moneva.247 The energy of the rotation around the C-N bond was conducted for 5.3•H+ and 5.3 at the DFT/BP86 level of theory using 6-311G** basis set in gas phase and compared. These calculations have revealed that the energy of rotation is higher for compound 5.3•H+ (13.6 kcal.mol-1) compared to 5.3 (2.6 kcal.mol-1). Moreover the nitro group is coplanar to the immediately attached neighbouring aromatic core, while a tilt of the dihedral angle of 25 ° is found for 5.3. Such a “coplanar” conformation is thus likely to occur in acid medium and this probably explains the remarkable fluorescence of this molecule.

Interestingly, a very similar behaviour is observed for 5.4, the formylated derivative. Due to the similarities with 5.3, the key pieces of information and data have been collected and summarized in Table 5.2 and Scheme 5.7, rather than detailed in length. In fact, 5.4 fluoresces strongly at 594 nm with a quantum yield of 34% in CH3CN, while upon protonation quinacridinium 5.4•H+ exhibits fluorescence at higher wavelength 628 nm, with a quantum yield of 39% (Table 5.2). The high quantum yield value of 5.4 and 5.4•H+, may indicate the presence of precise conformations for the CHO group and of hindered rotations in both basic and acidic forms. In fact, for 5.4•H+, an H-bond between the N-H group and the sp2 oxygen of the aldehyde can be proposed. For neutral 5.4, it is the double bond character of the C5-Cα bond arising from resonance interaction of type 5.4 and 5.4’ that is postulated (Figure 5.10).

246 a) K. Tateno, R. Ogawa, R. Sakamoto, M. Tsuchiya, T. Otani, T. Saito, Org. Lett. 2014, 16, 321; b) J. Han, K. Burgess, Chem. Rev. 2009, 110, 2709. 247 Pau Moneva computational chemistry project, University of Geneva, 2015

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Figure 5.10: Conformations adopted by 5.4•H+ and 5.4 in acidic and basic medium.

While these interactions and resulting conformations have been proposed in the literature,248 they do not seem to fit, at first glances the 1H NMR data. In fact, the chemical shift for the aldehyde proton is higher (11 ppm) for the 5.4 than for the quinacridinium derivative 5.4•H+ (10.1 ppm). The reason for this shielding of the hydrogen atom upon protonation is unclear.

Table 5.2. Fluorescence properties of 5.4 and 5.4•H+. [a] Product pH ΦF τf λEm (nm) 5.4•H+ 3 39 11.4 628 5.4 9 34 8.7 594 [a] fluorescence quantum yield using cresyl violet as reference (error: ±10)

For the preparation of 5.4 in non-racemic form, enantiopure quinacridinium (P)-(+)- + + [2.4e•H ][BF4] and (M)-(–)-[2.4e•H ][BF4] were converted into the corresponding protonated + 20 (P)-(+) and (M)-(–) quinacridinium [5.4•H ][BF4] ([α] 365 = +23200 and –21100, CH3CN, 5.2 10-6 g.ml-1) in 40 and 35% yields respectively (Scheme 5.5).243 These relatively low yields are due to low conversions of the starting material. In fact, 50% of unreacted starting materials were recovered each time. Upon basification a small increase in the intensity of the specific optical rotation of conjugate quinacridine (P)-(+)-5.4 and (M)-(–)-5.4 has also been noticed 20 [α] 365 +26900 and –24300 respectively (Scheme 5.7).

248 a) M. Rabinovitz,A. Ellencweig, Tetrahedron Lett. 1971, 46, 4439; b) F. A. L. Anet, M. Ahmad, J. Am. Chem. Soc., 1964, 86, 119.

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

Scheme 5.7: Formylation of enantiopure quinacridine 2.4•H+.

In term of ECD, the spectra of the two enantiomers display perfect mirror image and six Cotton effects are also noticeable (Figure 5.11). The transitions are predominantly observed in high energy UV domain of the light spectrum or close to it, at 280, 305, 335, 390, 410 and 450 nm as for 5.3 derivatives. Not surprisingly, protonation and deprotonation processes induce strong modifications in the CD spectra. However, no inversion of Cotton effect was observed upon protonation.

Δε

+ ____ + Figure 5.11: ECD spectra of (P)-(+)-[5.4•H ][BF4] ( ) and (M)-(–)-[5.4•H ][BF4] (- - -); and of (P)-(+)-5.4 -5 (°°°°°) and (M)-(–)-5.4 (˟˟˟˟˟). Solutions in CH3CN, 20 °C, C = 1·10 M.

In conclusion, two new pH-sensitive quinacridines were disclosed. These compounds display interesting molecular switch ability of fluorescence and chiroptical activity as function

116

Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores of the pH and this property is linked to the existence of intramolecular hydrogen bonding interactions.

5.5 Chiral BODIPY Based on Quinacridine Scaffold

As just demonstrated, simple substituents such as NO2 and CHO have a profound influence on the chemical and (chir)optical properties of unsymmetrical quinacridines. Importantly, they are also versatile chemical building blocks easily transformed in a variety of other functional groups or chemical systems. For instance, when positioned α to pyrroles or phenols, carbonyl groups are known to react with primary amines and anilines and the resulting α-imino derivatives may react with Lewis acid such as BF3•OEt2 and generates cyclic boron based ylide derivatives of type 5.12249 and 5.13.250 Those are related to the BODIPY family of dyes 5.14 (Figure 5.12).251 These chromophores have been strongly studied in the last two decades for their luminescence properties in particular.

Figure 5.12: structure of BODIPY and related π-locked conjugated chromophores.

Generally, BODIPYs (Boron dipyrromethene) are characterized by narrow absorption and emission bandwidths. Thanks to a variety of substitution schemes, many compounds that cover the entire visible spectral range of light have been prepared with high peak intensities, 252 small Stokes shifts, and high fluorescence quantum yields (ΦF). Their properties arise from the use of a central four-coordinated B(III) atom that configurationally locks the N,N ligands and thus rigidify the dipyrromethene core (Figure 5.12). The pivotal role of this B(III) atom is also to stabilize the ligand’s coordination and flatten the π-system, which induces the

249 D. Suresh, C. S. B. Gomes, P. T. Gomes, R. E. Di Paolo, A. L. Macanita, M. J. Calhorda, A. Charas, J. Morgado, M. T. Duarte, Dalton Trans. 2012, 41, 8502. 250 a) E. Hohaus, Fresenius Z. Anal. Chem. 1983, 315, 696; b) E. Hohaus, Monatsh. Chem. 1980, 111, 863. 251 Treibs, A.; Kreuzer, F.-H. Liebigs Ann. Chem. 1968, 718, 208 252 a) Boens, N.; Leen, V.; Dehaen, W. Chem. Soc. Rev. 2012, 41, 1130; b) A. Loudet, K. Burgess, Chem. Rev. 2007, 107, 4891

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores enhancement of the conjugation.253 Recently, chiral and configurationally π-locked BODIPY have been reported. The chiral information is however carried by a BINOL auxiliary attached to the boron rather by the N,N-π-conjugated framework.254 With derivatives 5.12, 5.13 and 5.14 detailed above, we saw an opportunity to develop the “opposite”, that is a BODIPY derivative with simple achiral fluorides on the boron together with chiral (helical) diamino ligand backbone.

Practically, compound 5.15 was synthesized in two steps. The aldehyde group was transformed into a phenyl imine using a slight excess (1.1 equivalent) of aniline in presence of molecular sieves 4 Å, at 60 °C for 1.5 h. Then treatment of the crude mixture for 12 h with

Hünig’s base and BF3•OEt2 afforded BODIPY-like 5.15 in 82% yield (Scheme 5.8).

Scheme 5.8: BODIPY-like 5.15 synthesis.

The optical properties of 5.15 were then studied and the steady-state absorption and emission spectra are shown in Figure 5.13. Interestingly, when going from 5.4•H+ to 5.15, shifts of all the transition absorption bands are observed. In fact, the lower energy bands ( = 570 and 530 nm) display slight hypsochromic shifts ( = 560 and 520 nm), while the high energy one ( = 380 nm) shows a strong bathochromic effect ( = 440 nm). Most probably, the boron (III) atom assumes a role similar to that of the hydrogen in 5.4•H+.

253 Frath, D.; Massue, J.; Ulrich, G.; Ziessel, R. Angew. Chem. Int. Ed. 2014, 53, 2290 254 a) E. M. Sanchez-Carnerero, F. Moreno, B. L. Maroto, A. R. Agarrabeitia, M. J. Ortiz, B. G. Vo, G. Muller, S. de la Moya, J. Am. Chem. Soc. 2014, 136, 3346; b) E. M. Sánchez-Carnerero, F. Moreno, B. L. Maroto, A. R. Agarrabeitia, J. Bañuelos, T. Arbeloa, I. López-Arbeloa, M. J. Ortiz, S. de la Moya, Chem. Commun. 2013,49, 11641.

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___ ….. Figure 5.13: Steady-state absorption ( ) and emission ( ) spectra of compound 5.15, in CH3CN, 20 °C, C = 10-5 M).

In terms of fluorescence, quinacridine 5.15 fluoresces around 596 nm (Figure 5.13) with a rather high ΦF of 26% in CH3CN (using cresyl violet as reference, Table 5.3) and a τf of 12.7 ns. The fluorescence time profile of 5.15 was recorded at the maximum emission wavelength by time-correlated single photon counting (TCSPC) upon 470 nm excitation.255

Table 5.3. Fluorescence properties of 5.12. [a] Product ΦF τf (ns) 5.12 26 12.7 [a] fluorescence quantum yield using cresyl violet as reference (error: ±10)

To study the chiroptical properties of 5.15 quinacridine P-(+)-5.4•H+ and (M)-(-)-5.4•H+ were converted to their corresponding BODIPY-like derivatives using the same protocol described above. The corresponding P-(+)-5.15 and (M)-(-)-5.15 were obtained with relatively good yields 80 and 88% respectively.

In their ECD spectra, the two enantiomers display perfect mirror image with three transitions bands in the UV domain and one in the visible part of light (Figure 5.14). However, less

255 a) A. Fürstenberg, E. Vauthey, Photochem. Photobiol. Sci. 2005, 4, 260-267; b)P.-A. Muller, C. Högemann, X. Allonas, P. Jacques, E. Vauthey, Chem. Phys. Lett. 2000, 326, 321-327.

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20 Cotton effect, lower Δε and also lower specific optical was noticed ([α] 365 = +11350 and - -5 11200 respectively, in CH3CN, 10 M) compared to 5.4.

Δε

____ Figure 5.14: ECD spectra of (P)-(+)-[5.15][BF4] ( ) and (M)-(–)-[5.15] [BF4] (- - -) derived from (+)- and (–)- [5.4•H+] respectively.

Somewhat to our surprise, the comparison of the properties of 5.4•H+ and 5.15 indicates that the simpler aldehyde derivative possess “better” absorption, fluorescence OR and ECD properties that the BODIPY-like derivative.

Finally, a single BODIPY-like compound has been studied so far. Clearly, structural variations need to be made as the nature of imino side chain may influence positively the optical properties.

5.6 Chiral and Fluorescent Azobenzene Based on Quinacridine

The discovery of azo compounds dates back to the 19th century256 and, for many years, they have been an important class of synthetic colouring agents in the dye industry.257 A large variety of azo compounds has been investigated primarily with the goal of obtaining dyes of desired colour/shade that could be prepared reliably and cheaply.258 There is a vast practical knowledge concerning the adjustment of their properties by varying the nature, position and number of substituents. However, there are only few examples of somewhat efficient

256 A. Noble, Justus Liebigs Ann. Chem. 1856, 98, 253 257 a) J. Griffiths, Chem. Soc. Rev. 1972, 1, 481; b) K. Venkataraman, The chemistry of synthetic dyes, Academic Press, New York, 1956. 258 F. Hamon, F. Djedaini-Pilard, F. Barbot, C. Len, Tetrahedron 2009, 65, 10105

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores fluorescent azobenzenes.259 The reason of the modest fluorescence is the ease and efficient photoisomerization of azo derivatives in the photoexcited state (Figure 5.15).

Figure 5.15: Concept of the molecular design to make fluorescent azobenzenes by dative N-B bond.

However recently, Kawashima and co-workers revisited this chemistry and designed fluorescent azobenzenes by incorporating a bis-pentafluorophenyl borane moiety 5.16 (Scheme 5.9). 260,261

Scheme 5.9: Synthesis of fluorescent azobenzene of type 5.16 and 5.17.

Structural modifications by introduction of electron donating/accepting groups at para positions led to a series of azobenzene derivatives emitting green, yellow, orange and red fluorescence. Structural analysis revealed that the boron atom coordinated the lone pair of an azo nitrogen atom. A consequence of this interaction is that the π-conjugated systems are fixed and the isomerization ‘‘locked’’ around the azo bond thereby making

259 a) Y. Wakatsuki, H. Yamazaki, P. A. Grutsch, M. Santhanam, C. Kutal, J. Am. Chem. Soc. 1985, 107, 8153; b) M. Shimomura, T. Kunitake, J. Am. Chem. Soc. 1987, 109, 5175; c) M. Ghedini, D. Pucci, G. Calogero, F. Barigelletti, Chem. Phys. Lett. 1997, 267, 341; d) M. Ghedini, D. Pucci, A. Crispini, I. Aiello, F. Barigelletti, A. Gessi, O. Francescangeli, Appl. Organomet. Chem. 1999, 13, 565; e) I. Aiello, M. Ghedini, M. La Deda, J. Lumin. 2002, 96, 249; f) M. Han, M. Hara, J. Am. Chem. Soc. 2005, 127, 10951; g) M. R. Han and M. Hara, New J. Chem. 2006, 30, 223 260 J. Yoshino, N. Kano, T. Kawashima, Dalton Trans. 2013, 42, 15826 261 J. Yoshino, N. Kano, T. Kawashima, Chem. Commun. 2007, 559

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores photoisomerization a less likely pathway in the excited state (Figure 5.15).262 Needless to say that to our knowledge there is no report dealing with chiral fluorescent azobenzenes.

We saw therefore in compound 5.8 an opportunity to change this situation. The azo derivative was treated with BF3•OEt2 in the presence of diisopropylethylamine (DIPEA) as depicted in Scheme 5.8. The NMR analysis of the crude mixture indicates the presence of several species out of which one major derivative can be isolated. Its exact chemical nature remains at this point debatable. In fact, there are two possible regioisomers with 6- and 5- membered ring size respectively (Scheme 5.10). So far, there has been no means to distinguish unambiguously one from the other. Literature precedents from the group of Aprahamian would tend to favour 5.18b which seems to be formed predominantly at low temperature.263 Yet, at the end of this section, a result indicates that 5.18a might be favoured without bringing still a full confidence. As such we are representing the main product as 5.18a but, with time and further experiments, it could turn out that it is 5.18b finally.

Scheme 5.10: Synthesis of fluorescent azobenzenes 5.18a and b.

Nevertheless, the optical properties of isolated compound (described as 5.18a) were studied. Satisfactorily, compound 5.18a exhibits absorption in the yellow part of visible light, with a strong and large transition band centered at 570 nm (Figure 5.16). Its fluorescence appears around 595 nm with a quantum yield of 7% and 17% and fluorescence lifetime of 1.7 and 2.8 ns in CH3CN and CH2Cl2 respectively (Table 5.4). These values are promising as azobenzenes of type 5.16 display high fluorescence only in very apolar solvents such as hexane (Scheme 5.9).260

262 J. Yoshino, A. Furuta, T. Kambe, H. Itoi, N. Kano, T. Kawashima, Y. Ito, M. Asashima, Chem. Eur. J. 2010, 16, 5026 263 a) X. Su, I. Aprahamian, Chem. Soc. Rev. 2014, 43, 1963; b) Y. Yang, R. P. Hughes, I. Aprahamian, J. Am. Chem. Soc. 2014, 136, 13190; c) Y. Yang, R. P. Hughes, I. Aprahamian, J. Am. Chem. Soc. 2012, 134, 15221

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores

___ ….. - Figure 5.16: Steady-state absorption ( ) and emission spectra ( ) of 5.18a. Solution in CH3CN, 20 °C, C = 10 5 M.

Table 5.4. Fluorescence properties of 5.14. [a] Product Solvent ΦF τf (ns)

5.14 CH3CN 7 1.7

5.14 CH2Cl2 17 2.8 [a] fluorescence quantum yield using cresyl violet as reference (error: ±10)

Furthermore, azobenzene derivatives of type 5.17, bearing Fluor atom instead of pentafluorophenyl substituents on the boron atom, showed almost no fluorescence (Scheme 5.7).260 It has been speculated by the authors that “this could be due to intramolecular charge transfer from the more electron rich aryl substituent into the excited-state of the complexed azobenzene system”.246b In fact, fluorescent dyes were obtained only with bis- pentafluorophenyl borates substituent on the boron. The fluorescence displayed by 5.18a is thus remarkable and this property could be attributed to the acceptor ability of the cationic helical core which supress the intramolecular charge transfer.

Compound 5.18a displays however lower fluorescence quantum yield and lifetime than all the substituted chiral quinacridines (so far). This is attributed to the azo functional group which

123

Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores induces this type of effect, and fluorescence quenching via photoinduced electron transfer (PET)264 or a charge transfer (CT)265 could also be the reason.

In order to better identify the molecule responsible of this fluorescence (5.18a with the 6-membered ring or 5.18b with the 5-membered ring) additional fluorescence decay and emission measurements were performed by exciting the solution containing this derivative at difference wavelengths (Figure 5.17).

Figure 5.17: Emission (up) and fluorescence time profile (bottom) spectra of 5.18 derivatives upon two different excitation wavelengths.

According to these measurements only one species is present in solution (no other contribution was detected) and it is responsible for the fluorescence. This tends to favor the 6-

264S. Doose, H. Neuweiler, M. Sauer, ChemPhysChem 2009, 10, 1389 265J. Wu, W. Liu, J. Ge, H. Zhang, P. Wang Chem. Soc. Rev. 2011, 40, 3483

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Chapter 5: Synthesis and Properties of Chiral pH-sensitive Quinacridine, BODIPY-like and Azobenzene Fluorophores membered ring form 5.19a, as for the 5-membered 5.19b two different species in equilibrium are expected upon photoirradiation (Scheme 5.11).263

Scheme 5.11: Isomerization of 5.19b induced by visible light.

In a near future, further experiments will be performed with more crystalline azo precursors and products. X-ray crystallographic studies will provide the surest proof of the geometry. Also, if the compound is prepared in enantiopure fashion, IR and VCD analysis might well shed some light on the chemical nature of the entity.

In conclusion, the functionalization of quinacridine of type 2.4 was disclosed, allowing the synthesis of new [4]helicenes based chromophores. New pH-switchable optical and chiroptical [4]helicenes were isolated and their properties reported as proof of concept. Moreover, chiral fluorescent BODIPY and azobenzene like helicenes scaffold were prepared. These two latter families of dyes constitute promising examples of chiral BODIPY and azobenzene derivatives.

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126

Experimental Part

Experimental Part

General Remarks

All reactions involving air sensitive compounds were carried out under dry N2 or argon by means of an inert gas/vacuum double manifold line and standard Schlenk techniques. Solvents were dried through a highly activated alumina column under a dry inert atmosphere or dried and distilled prior to use. CDCl3 (SDS) was filtered on basic alumina prior to use. Analytical thin-layer chromatography (TLC) was performed with Merck SIL G/UV254 plates or Fluka 0.25 mm basic alumina (pH = 9.9) plates. Visualization of the developed chromatogram was performed by UV/VIS detection. Organic solutions were concentrated under reduced pressure on a Buchi rotary evaporator. Flash column chromatography (silicagel 60, 40 µm or Fluka basic alumina type 5016A) was performed in air and under pressure (~0.1 bar). Unless otherwise noted, all chemicals obtained commercially were purified according to standard literature procedures.266

Nuclear Magnetic Resonance (NMR) spectra were recorded on Bruker AMX-400 (or 500) at 19 1 RT. F-NMR chemical shifts are given in ppm relative to CFCl3. H NMR chemical shifts are 13 given in ppm relative to Me4Si with the solvent resonance used as the internal standard. C

NMR chemical shifts were given in ppm relative to Me4Si, with the solvent resonance used as the internal standard. Unless otherwise noted, the spectra were recorded at RT (298 K). Assignments have been achieved using COSY, INVIET and/or NOESY experiments. Data were reported as follows: chemical shift (δ) in ppm on the δ scale, multiplicity (s = singlet, d = doublet, dd = doublet of doublet, td = triplet of doublet, t = triplet, q = quartet and m = multiplet), coupling constant J (Hz), and integration (br = broad signal). Unless otherwise noted, the coupling constants concern proton-proton coupling. IR spectra were recorded with a Perkin-Elmer 1650 FT-IR spectrometer using a diamond ATR Golden Gate sampling. Melting points (M.p.) were measured in open capillary tubes on a Stuart Scientific SMP3 melting point apparatus and were uncorrected. Electrospray mass spectra (ES-MS) were obtained on a

127

Experimental Part

Finnigan SSQ 7000 spectrometer by the Department of Mass Spectroscopy of the University of Geneva. UV spectra were recorded on a CARY-1E spectrometer in a 1.0 cm quartz cell; -1 3 -1 λmax are given in nm and molar absorption coefficient ε in cm ·dm ·mol . Circular dichroism spectra were recorded on a JASCO J-715 polarimeter in a 1.0 cm quartz cell; λ are given in nm and molar circular dichroic absorptions (ε in M-1.cm-1). Optical rotations were measured on a Perkin-Elmer 241 or a JASCO P-1030 polarimeter in a thermostated (20 °C) 10.0 cm long microcell with high pressure lamps of sodium or mercury and are reported as follows: 20  (c (g/100 ml), solvent). HPLC analyses were performed on an Agilent 1100 apparatus (binary pump, autosampler, column thermostat and diode array detector). X-ray diffraction structures were solved at the “Laboratoire de Cristallographie aux rayons X, Service de Resolution Structurale par Diffraction des Rayons X” by Dr. Céline Besnard.

266 D. D. Perrin, W. L. F. Armarego, Purification of Laboratory Chemicals, 4th ed., Pergamon Press: Oxford, 1997.

128

Experimental Part

Synthesis of pH-Sensitive and Fluorescent Quinacridines

General Procedures I for the Synthesis of Cationic Quinacridines 2.4a to 2.4k

1st Approach

To a solution of the corresponding acridinium salt 2.5 (6 mmol in anhydrous DMF (30 ml) in a red tainted glassware, was added 7.3 ml (150 mmol, 25 equiv) of hydrazine monohydrate (64-65% in water). The reaction mixture was degassed with argon and then heated at 90 °C without light for 10 hours. After complete consumption of starting acridinium salt 2.5 (monitored by ESI-MS analysis), the purple reaction mixture was allowed to cool to 20 °C.

The crude product precipitated upon addition of a solution of 50% HBF4 in water (~80 ml).

The solid was filtered, washed several times with water and then dissolved in CH2Cl2. Selective precipitation by addition of diethyl ether afforded the title green compounds.

2nd Approach

To a solution of acridinium salt 2.5j (300 mg, 627 µmol) in anhydrous DMF (3 ml) contained in a red-tainted glassware, was added 15.68 mmol (25 equiv) of the corresponding primary amine. The reaction mixture was degassed with argon and then heated at 90 °C without light for 14 hours. After complete consumption of starting acridinium salt 2.5j (monitored by ESI- MS analysis), the purple reaction mixture was allowed to cool to 20 °C. The crude product precipitated upon addition of a solution of 50% HBF4 in water (~10 ml). The solid was filtered, washed several times with water and then dissolved in CH2Cl2. Selective precipitation by addition of diethyl ether afforded the title green compounds

129

Experimental Part

1,13-Dimethoxy-5-propyl-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4a•H ][BF4]

Prepared following the 2nd approach of the general procedure I using n-propylamine as primary amine (1.3 ml, 15.7 mmol). The desired product was obtained as an amorphous green solid (264 mg, 577 µmol, 92% yield).

Rf = 0.35 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (500 MHz, CD2Cl2) δ 7.94 (t, J = 8.3 Hz, 1H, CH), 7.82 (dd, J = 8.9 Hz, 8.0, 1H, CH), 7.72 (dd, J = 8.5 Hz, 7.9, 1H, CH), 7.59 (dd, J = 8.3 Hz, 0.7, 1H, CH), 7.45 (dd, J = 8.6 Hz, 0.9, 1H, CH), 7.23 (dd, J = 9.0 Hz, 0.7, 1H, CH), 7.16 – 7.13 (m, 1H, CH), 6.79–6.76 (m, 1H, CH), 6.71 (dd, J = 8.0 Hz, 0.8, 1H, CH), 4.47 (m, 1H, CH), 4.23–4.16 (m, 1H, CH), 3.73 13 (2s, 6H, 2×OCH3), 2.09–1.99 (m, 2H, CH2), 1.20 (t, J = 7.4, 3H, CH3). C NMR (126 MHz,

CD2Cl2) δ 160.5 (C), 159.1 (C), 144.14 (C), 143.2 (C), 142.21 (C), 138.6 (C), 138.34 (C), 137.1 (C), 136.8 (C), 136.39 (C), 118.8 (CH), 113.1 (CH), 112.6 (CH), 110.1 (CH), 107.1

(CH), 106.8 (CH), 103.5 (CH), 102.8 (CH), 102.77 (CH), 55.7 (CH3), 55.7 (CH3), 50.9 (CH2), 19 19.7 (CH2), 11.1 (CH3). F NMR (282 MHz, CD2Cl2) δ –149.91 (20%), –149.96 (80%). IR -1 (in CH2Cl2, cm ) ν = 3299, 2941, 1637, 1583, 1480, 1343, 1254, 1162, 1055, 814, 764, 707, -5 655. UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 (4.65);

1,13-dimethoxy-5-propyl-5H-quinolino[2,3,4-kl]acridine 2.4a

-5 UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 573 (3.65), 533 (3.69), 349 (3.7), 300 (4.2). + HRMS (ESI) calculated for [C24, H23, N2, O2 (M+H) ]: 371.1754 Found: 371.1750.

130

Experimental Part

1,13-Dimethoxy-5-methyl-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4b•H ][BF4]

Prepared following the 1st approach of general procedure I, using 9-(2,6-dimethoxyphenyl)- 1,8-dimethoxy-10-methyl-9,10-dihydroacridin-9-ylium tetrafluoroborate 4b as acridinium salt (2.90 g, 6.07 mmol). The desired product was obtained as an amorphous green solid (2.53 g, 5.88 mmol, 97% yield).

Rf = 0.3 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.79–7.62 (m, 5H), 7.16 (d, J = 8.7 Hz, 1H, CH), 6.98 (d, J = 8.0 Hz, 1H, CH), 6.72 (d, J = 8.0 Hz, 1H, CH), 6.66 (dd, J = 6.9 Hz, 1.8, 1H), 3.83 (s, 3H, 13 CH3), 3.69 (s, 3H, OCH3), 3.65 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 160.2 (C), 159.2 (C), 144.1 (C), 143.5 (C), 142.4 (C), 139.5 (C), 138.4 (C), 137.2 (C), 136.6 (C), 136.0 (C), 118.9 (CH), 113.2 (CH), 112.8 (CH), 110.5 (CH), 107.4 (CH), 107.0 (CH), 103.7 (CH), 19 103.2 (CH), 102.9 (CH), 55.9 (CH3), 55.9 (CH3), 36.9 (CH3). F NMR (282 MHz, CD2Cl2) -1 δ –151.24 (20%), –151.29 (80%). IR (in CH2Cl2, cm ) ν = 2944, 2845, 1637, 1582, 1530,

1499, 1347, 1256, 1167, 1053, 1029, 891, 814, 761, 727, 653, 623. UV-Vis (CH3CN, C= -5 1×10 M): λmax (log ε): 625 (4.11), 579 (4.07), 425 (3.9), 309 (4.76).

1,13-dimethoxy-5-methyl-5H-quinolino[2,3,4-kl]acridine 2.4b

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 585 (4.8), 535 (4.8). HRMS (ESI) calculated + for [C22, H19, N2, O2 (M+H) ]: 343.1441. Found: 343.1441.

131

Experimental Part

5-Hexyl-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4c•H ][BF4]

Prepared following the 1st approach of general procedure I, using 9-(2, 6-dimethoxyphenyl)- 10-hexyl-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate 4c as acridinium salt (2.7 g, 4.93 mmol). The desired product was obtained as an amorphous green solid (2.02 g, 4.04 mmol, 82% yield).

Rf = 0.3 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.97 (d, J = 8.2 Hz, 1H), 7.91–7.85 (m, 2H), 7.78 (t, J = 8.4 Hz, 1H), 7.67 (t, J = 8.1 Hz, 1H), 7.18 (d, J = 8.8 Hz, 1H), 7.06 (d, J = 8.2 Hz, 1H), 6.75 (d, J = 8.0 Hz, 1H), 6.68 (d, J = 7.9 Hz, 1H), 4.46 (ddd, J = 15.1 Hz, 10.8, 6.2, 1H), 4.16 (ddd, J = 15.7 Hz, 10.7, 5.9, 1H), 3.71 (d, J = 8.3 Hz, 6H), 1.97 (ddd, J = 14.4 Hz, 11.8, 6.7, 2H), 1.58 (q, J = 7.3 Hz, 2H), 1.43 (tdd, J = 9.0 Hz, 6.7, 4.3, 4H), 0.95 (t, J = 7.0 Hz, 3H). 13C NMR

(101 MHz, CD2Cl2) δ 160.7 (C), 159.1 (C), 143.5 (C), 143.4 (C), 142.8 (C), 139.0 (C), 138.7 (C), 136.9 (C), 136.3 (C), 135.9 (CH), 119.2 (CH), 113.1 (CH), 112.9 (CH), 110.9 (CH),

107.4 (CH), 107.2 (CH), 103.0 (CH), 102.8 (CH), 102.6 (CH), 55.9 (CH3), 31.9 (CH2), 27.0 19 (CH2), 26.2 (CH2), 23.2 (CH2), 14.3(CH3). F NMR (282 MHz, CD2Cl2) δ –152.18 (20%), – -1 152.23 (80%). IR: (in CH2Cl2, cm ): ν = 2927, 2854, 2264, 1637, 1580, 1482, 1343, 1252, -5 1161, 1113, 1059, 886, 815, 760, 727, 651. . UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 625 (3.95), 582 (3.9), 429 (3.7), 310 (4.63).

5-Hexyl-1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridine 2.4c

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 577 (3.84), 533 (4), 346 (3.95), 300 (4.53). + HRMS (ESI) calculated for [C27, H29, N2, O2 (M+H) ]: 413.2223. Found: 413.2223.

132

Experimental Part

5-Hexadecyl-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4d•H ][BF4]

Prepared following the 1st approach of general procedure I, using 9-(2, 6-dimethoxyphenyl)- 10-hexadecyl-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate 4d as acridinium salt (3.5 g, 5.08 mmol). Then the compound is purified by column chromatography with basic alumina using CH2Cl2/MeOH. The desired product was obtained as an amorphous green solid (2.60 g, 4.06 mmol, 80% yield).

Rf = 0.37 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.89 (dt, J = 16.1 Hz, 8.1, 2H), 7.83–7.74 (m, 2H), 7.66 (t, J = 8.1 Hz, 1H), 7.18 (dd, J = 8.7 Hz, 2.4, 1H), 7.06 (d, J = 7.9 Hz, 1H), 6.75 (dd, J = 8.1 Hz, 2.4, 1H), 6.67 (dd, J = 7.8 Hz, 2.5, 1H), 4.51 – 4.39 (m, 1H), 4.21–4.08 (m, 1H), 3.70 (dd, J = 7.2 Hz, 2.4, 6H), 2.01–1.93 (m, 2H), 1.58 (t, J = 7.6 Hz, 2H), 1.50–1.42 (m, 2H), 1.27 (d, J = 13 8.1 Hz, 22H), 0.88–0.84 (m, 3H). C NMR (101 MHz, CD2Cl2) δ 160.7 (C), 159.2 (C), 143.5 (C), 143.4 (C), 142.9 (C), 139.1 (C), 138.8 (C), 136.9 (C), 136.4 (C), 136.00 (C), 119.2 (CH), 113.1 (CH), 112.9 (CH), 110.9 (CH), 107.5 (CH), 107.2 (CH), 103.1 (CH), 102.8 (CH),

102.7 (CH), 55.9 (CH3), 49.9 (CH3), 32.4 (CH2), 30.2 (CH2), 30.2 (CH2), 30.1 (CH2), 30.1 19 (CH2), 29.9 (CH2), 29.8 (CH2), 27.4 (CH2), 26.3 (CH2), 23.2 (CH2), 14.4 (CH3). F NMR -1 (282 MHz, CDCl3) δ –150.68 (20%), –150.73 (80%). IR (in CH2Cl2, cm ) ν =:2921, 2851,

1639, 1582, 1529, 1484, 1344, 1254, 1162, 1054, 862, 815, 760, 729, 651. . UV-Vis (CH3CN, -5 C= 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 (4.65).

5-hexadecyl-1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridine 2.4d

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 573 (3.65), 533 (3.69), 349 (3.7), 300 (4.2). + HRMS (ESI) calculated for [C37, H49, N2, O2 (M+H) ]: 553.3788. Found: 553.3792

133

Experimental Part

Rac-1,13-Dimethoxy-5-(o-tolyl)-5,9-dihydroquinolino[2,3,4-kl]acridin-13b- + yliumtetrafluoroborate salt [2.4e•H ][BF4]

Prepared following the 1st approach of general procedure I, using 9-(2, 6-dimethoxyphenyl)- 1,8-dimethoxy-10-phenyl-9,10-dihydroacridin-9-ylium tetrafluoroborate 4e as acridinium salt (2.7 g, 5.0 mmol). The desired product was obtained as an amorphous green solid (2.31 g, 4.7 mmol, 94% yield).

Rf = 0.41 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.81–7.72 (m, 4H), 7.63 (dd, J = 8.3 Hz, 0.9, 1H), 7.57 (dd, J = 8.8 Hz, 8.0, 1H), 7.51 (dd, J = 8.6 Hz, 0.9, 1H), 7.47–7.32 (m, 3H), 6.77–6.74 (m, 2H), 6.48 13 (ddd, J = 8.8 Hz, 7.7, 0.9, 2H), 3.78 (d, J = 3.5 Hz, 6H). C NMR (126 MHz, CD2Cl2) δ 160.4 (C), 159.4 (C), 145.2 (C), 144.9 (C), 142.8 (C), 140.3 (C), 138.2 (C), 138.2 (C), 137.2 (CH), 136.7 (CH), 136.0 (CH), 130.9 (CH), 118.4 (C), 112.9 (C), 112.7 (C), 110.30 (CH), 19 108.9 (CH), 107.0 (CH), 105.5 (CH), 103.1 (CH), 103.0 (CH), 55.9 (CH3), 55.8 (CH3). F -1 NMR (282 MHz, CD2Cl2) δ –149.70 (20%), –149.75(80%). IR (in CH2Cl2, cm ) ν = 3297, 3188, 2941, 2847, 1935, 1637, 1582, 1525, 1485, 1347, 1260, 1177, 1055, 858, 812, 766, 707, -5 651. . UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 630 (4.09), 587 (4), 430 (3.81), 310 (4.71);

1,13-dimethoxy-5-phenyl-5H-quinolino[2,3,4-kl]acridine 2.4e

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 576 (3.7), 533 (3.73), 351 (3.73), 300 (4.47). + HRMS (ESI) calculated for [C27, H21, N2, O2 (M+H) ]: 405.1597. Found: 405.1604.

Optical Resolution of Quinacridine 2.4e: In HPLC, using a Chiralcel IC column, both enantiomers of racemic azahelicene 1f differed significantly in their retention times. A separation was then possible under semi-preparative conditions using a 1 x 25 cm column.

134

Experimental Part

Racemic diazahelicene 2.4e (110 mg) was resolved by the repeated HPLC separation using an Agilent 1100 Series instrument (hexane:isopropanol 2:8 + 0.1% ethanolamine, 1.5 ml/min flow rate). Evaporation of the solvents and trituration with diethyl ether afforded (+)-2.4e (50 mg, >99 % ee) and ()-2.4e (43 mg, >99 % ee) as pink amorphous solids.

-6 -1 (+)-2.4e: [α]365+ 11000 (c 4.9 10 g.ml , CH3CN), retention time 29.2 min (Chiralcel IC column). -6 -1 ()-2.4e: [α]365- 9400 (c 4.9 10 g.ml , CH3CN), retention time 48.2 min (Chiralcel IC column).

(+)-(P)-1,13-dimethoxy-5-phenyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate (+)-(P)-[2.4e•H ][BF4]

Prepared as described above and then transformed into it conjugated acid by dissolving the pink amorphous solid in CH2Cl2 and washed with a solution of 50% HBF4 in water. The title green compound was obtained in quantitative after extraction with CH2Cl2 and concentration of organic phase. CD (Acetonitrile, 1.10-5 M, 20 °C)  (Δε) 279 (42), 300 (-19), 313.5 (-13.1), 350 (-13.9), 498 (-2.3), 450 (5.36), 600 (1.7) + -6 -1 (+)-[2.4e•H ][BF4]: [α]365 11000 (c 4.92 10 g.ml , CH3CN, Hg lamp)

()-(M)-1,13-dimethoxy-5-phenyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b- + ylium tetrafluoroborate ()-(M)-[2.4e•H ][BF4]

Prepared as described above and then transformed into it conjugated acid by dissolving the pink amorphous solid in CH2Cl2 and washed with a solution of 50% HBF4 in water. The title green compound was obtained in quantitative after extraction with CH2Cl2 and concentration of organic phase.

135

Experimental Part

CD (Acetonitrile, 1.10-5 M, 20 °C)  (Δε) 279 (-37), 300 (15.5), 313.5 (15.48), 350 (22.6), 498 (2.4), 450 (-5.95), 600 (-2) + -6 -1 (−)-[2.4e•H ][BF4]: [α]365 −9400 (c 4.92 10 g.ml , CH3CN, Hg lamp)

Rac-5-benzyl-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4f•H ][BF4]

Prepared following the 1st approach of the general procedure I, using 10-benzyl-9-(2,6- dimethoxyphenyl)-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate 4f as acridinium salt (2.70 g, 4.88 mmol). The desired product was obtained as an amorphous green solid with (1.93 g, 3.80 mmol, 78% yield).

Rf = 0.44 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.61–7.54 (m, 2H), 7.54–7.46 (m, 2H), 7.38–7.28 (m, 4H), 7.27–7.21 (m, 2H), 6.70 (dd, J = 8.6 Hz, 0.9, 1H), 6.61 (ddd, J = 12.3 Hz, 7.2, 1.6, 2H), 6.44 (dd, J = 6.3 Hz, 2.2, 1H), 5.54 (d, J = 18.0 Hz, 1H), 5.13 (d, J = 18.0 Hz, 1H), 3.74 (s, 3H), 13 3.68 (s, 3H). C NMR (101 MHz, CD2Cl2) δ 159.8 (C), 158.5 (C), 151.7 (C), 148.92 (C), 144.2 (C), 139.7 (C), 136.0 (C), 133.5 (C), 132.3 (CH), 130.9 (CH), 130.5 (CH), 129.4 (CH), 127.8 (CH), 126.8 (CH), 121.1 (CH), 121.0 (CH), 117.0 (C), 115.2 (C), 113.2 (C), 107.2 19 (CH), 102.6 (CH), 100.9 (CH), 100.8 (CH), 55.5 (CH3), 54.4 (CH2), 53.4 (CH3). F NMR -1 (282 MHz, CD2Cl2) δ –149.82 (20%), –149.87 (80%). IR (in CH2Cl2, cm ) ν = 3297, 3245, 2937, 2843, 2199, 1951, 1637, 1583, 1528, 1495, 1343, 1254, 1161, 1055, 854, 814, 764, 704. -5 UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 621 (4.08), 574 (4.13), 439 (3.9), 310 (4.76);

136

Experimental Part

5-benzyl-1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridine 2.4f

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 575 (4), 533 (4.17), 349 (4.17), 300 (4.76). + HRMS (ESI) calculated for [C28, H23, N2, O2 (M+H) ]: 419.1754. Found: 419.1758.

Optical Resolution of Quinacridine 2.4f: In HPLC, using a Chiralcel IB column, both enantiomers of racemic azahelicene 1f differed significantly in their retention times. A separation was then possible under semi-preparative conditions using a 1 x 25 cm column. Racemic diazahelicene 2.4f (25 mg) was resolved by the repeated HPLC separation using an Agilent 1100 Series instrument (hexane:isopropanol 6:4 + 0.1% ethanolamine, 0.6 ml/min flow rate). Evaporation of the solvents and trituration with diethyl ether afforded (+)-2.4f (10 mg, >99 % ee) and ()-2.4f (8 mg, >99 % ee) as pink amorphous solids.

20 -5 -1 (+)-2.4f: [α] 365 +16500 (c 4.2 10 g.ml , CH3CN, Hg lamp), retention time 14.9 min (Chiralcel IB column). 20 -5 -1 ()-2.4f: [α] 365 16000 (c 4.2 10 g.ml , CH3CN, Hg lamp), retention time 17.2 min (Chiralcel IB column).

(+)-(P)- 5-benzyl-1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridine (+)-(P)-2.4f

CD (Acetonitrile, 1.10-5 M, 20 °C)  (Δε) 279 (42), 300 (8.23), 340 (5.88), 400 (-5.88), 535 (- 2.35) -5 -1 (+)-2.4f: [α]365 16500 (c 4.2 10 g.ml , CH3CN, Hg lamp)

137

Experimental Part

()-(M)- 5-benzyl-1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridine ()-(M)- 2.4f

CD (Acetonitrile, 1.10-5 M, 20 °C)  (Δε) 279 (-42), 300 (-8.23), 340 (-5.88), 400 (5.88), 535 (2.35) 20 -5 -1 (−)-2.4f: [α] 365 16000 (c 4.2 10 g.ml , CH3CN, Hg lamp)

(+)-(P)-5-benzyl-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt (+)-(P)-[2.4f•H ][BF4]

Prepared as described above and then transformed into it conjugated acid by dissolving the pink amorphous solid in CH2Cl2 and washed with a solution of 50% HBF4 in water. The title green compound was obtained in quantitative after extraction with CH2Cl2 and concentration of organic phase. CD (Acetonitrile, 1.10-5 M, 20 °C)  (Δε) 279 (42), 300 (-19), 313.5 (-13.1), 350 (-13.9), 498 (-2.3), 450 (5.36), 600 (1.7) + 20 -5 -1 (+)-[2.4f•H ][BF4]: [α] 365 10500 (c 5 10 g.ml , CH3CN, Hg lamp)

()-(M)-5-benzyl-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt ()-(M)-[2.4f•H ][BF4]

Prepared as described above and then transformed into it conjugated acid by dissolving the pink amorphous solid in CH2Cl2 and washed with a solution of 50% HBF4 in water. The title green compound was obtained in quantitative after extraction with CH2Cl2 and concentration of organic phase.

138

Experimental Part

CD (Acetonitrile, 1.10-5 M, 20 °C)  (Δε) 279 (-37), 300 (15.5), 313.5 (15.48), 350 (22.6), 498 (2.4), 450 (-5.95), 600 (-2) + 20 -5 -1 (−)-[2.4f•H ][BF4]: [α] 365 10000 (c 5 10 g.ml , CH3CN, Hg lamp) 5-(2-(Dimethylamino)ethyl)-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b- + ylium tetrafluoroborate salt [2.4g•H ][BF4]

Prepared following the 2nd approach of the general procedure I, using N, N- dimethylethylenediamine as primary amine (1.7 ml, 15.7 mmol). Then the compound is purified by column chromatography with basic alumina using CH2Cl2/MeOH. The desired product was obtained as an amorphous green solid (272 mg, 558 µmol, 89% yield).

Rf = 0.09 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.73 (dd, J = 8.6 Hz, 7.8 Hz , 1H, CH), 7.68–7.58 (m, 3H, 3×CH), 7.55 (t, J = 8.3 Hz, 1H, CH), 7.06 (d, J = 7.3 Hz, 1H, CH), 6.85 (d, J = 7.7 Hz, 1H, CH), 6.65 (d, J = 7.3 Hz, 2H, 2×CH), 4.46 (ddd, J = 15.2 Hz, 10.0 Hz, 5.4 Hz, 1H, CH), 4.16

(ddd, J = 15.1 Hz, 10.0 Hz, 5.2 Hz, 1H, CH), 3.77 (s, 3H, OCH3), 3.71 (s, 3H, OCH3), 2.98 – 13 2.73 (m, 2H, CH2), 2.45 (s, 6H, 2×OCH3). C NMR (101 MHz, CD2Cl2) δ 159.4 (C), 157.9 (C), 143.2 (C), 138.8 (C), 132.3 (CH), 131.1 (CH), 130.6 (CH), 120.2 (CH), 114.9 (CH),

114.2 (CH), 112.4 (CH), 105.9 (CH), 101.6 (CH), 100.4 (CH), 99.8 (CH), 54.9 (OCH3), 54.3 19 (CH2), 47.2 (CH2), 45.7 (NCH3). F NMR (282 MHz, CD2Cl2) δ –152.47 (20%), –152.52 -1 (80%). IR (in CH2Cl2, cm ) ν = 3310, 2946, 2531, 1642, 1583, 1500, 1348, 1258, 1168, -5 1063, 816, 763, 730, 651. UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 (4.65).

2-(1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridin-5-yl)-N,N-dimethylethan-1-amine 2.4g

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 573 (3.65), 533 (3.69), 349 (3.7), 300 (4.2). + HRMS (ESI) calculated for [C25, H36, N3, O2, (M+H) ]: 400.2020. Found: 400.2015.

139

Experimental Part

5-(2-Hydroxyethyl)-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4h•H ][BF4]

Prepared following the 2nd approach of the general procedure I, using ethanolamine as primary amine (1.2 ml, 15.7 mmol). Then the compound is purified by column chromatography with basic alumina using CH2Cl2/MeOH. The desired product was obtained as an amorphous green solid (237 mg, 514 µmol, 82% yield).

Rf = 0.09 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2 ) δ 7.73 (dd, J = 8.9 Hz, 8.0 Hz, 1H), 7.62 (t, J = 8.2 Hz, 1H), 7.54 (t, J = 8.2 Hz, 1H), 7.33–7.20 (m, 4H), 6.65 (d, J = 8.0 Hz, 1H), 6.55 (d, J = 7.9 Hz, 1H), 4.62 (dt, J = 15.3 Hz, 6.1 Hz, 1H), 4.36 (dt, J = 14.9 Hz, 6.2 Hz, 1H), 4.15 (h, J = 5.7 Hz, 5.0 13 Hz, 2H), 3.61 (s, 3H), 3.58 (s, 3H). C NMR (101 MHz, CD2Cl2) δ= 160.4 (C), 159.1 (C), 144.1 (C), 143.7 (C), 142.0 (C), 139.2 (C), 137.9 (C), 137.4 (C), 136.9 (C), 136.3 (C), 118.7 (CH), 113.0 (CH), 112.4 (CH), 110.0 (CH), 107.8 (CH), 106.7 (CH), 104.5 (CH), 102.9 (CH), 19 102.9 (CH), 59.0 (CH2), 55.8 (CH3), 55.8 (CH3), 54.41(CH2). F NMR (282 MHz, CD2Cl2) -1 δ –149.36 (20%), –149.42 (80%). IR (in CH2Cl2, cm ) ν = 3537 3302, 2943, 1637, 1583, -5 1529, 1478, 1343, 1254, 1163, 1048, 814, 763, 730, 651. UV-Vis (CH3CN, C= 1×10 M):

λmax (log ε): 623 (3.9), 577 (3.8), 427 (3.69), 310 (4.60);

2-(1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridin-5-yl)ethan-1-ol 2.4h

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 573 (3.65), 533 (3.69), 349 (3.7), 300 (4.2). + HRMS (ESI) calculated for [C23, H21, N2, O3 (M+H) ]: 373.1546. Found: 373.1540.

140

Experimental Part

5-(2-(2-Hydroxyethoxy)ethyl)-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin- + 13b-ylium tetrafluoroborate salt [2.4i•H ][BF4]

Prepared following the 1st approach of the general procedure I, using 9-(2, 6- dimethoxyphenyl)-10-(2-(2-hydroxyethoxy)ethyl)-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate 4h as acridinium salt (2.7 g, 4.89 mmol). The desired product was obtained as an amorphous green solid (2.17 g, 4.31 mmol, 88% yield).

Rf = 0.1 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD3CN) δ 7.65 (t, J = 8.4 Hz, 1H), 7.52 (t, J = 8.0 Hz, 1H), 7.43 (t, J = 8.0 Hz, 1H), 7.29–7.18 (m, 3H), 7.04 (d, J = 8.3 Hz, 1H), 6.65 (d, J = 8.0 Hz, 1H), 6.57 (d, J = 7.9 Hz, 1H), 4.53 (dt, J = 15.6 Hz, 5.7, 1H), 4.13 (dt, J = 15.6 Hz, 6.0 Hz, 1H), 3.91 (dp, J = 19.0 Hz, 5.3 Hz, 2H), 3.64 (dd, J = 5.4 Hz, 3.8 Hz, 2H), 3.56 (td, J = 4.2 Hz, 2.9 Hz, 2H), 13 3.54 (s, 3H), 3.48 (s, 3H). C NMR (101 MHz, CD3CN) δ 160.7 (C), 159.6 (C), 144.0 (C), 143.9 (C), 142.4 (C), 139.6 (C), 138.4 (C), 137.5 (C), 137.1 (C), 136.2 (CH), 113.1 (CH), 112.5 (CH), 109.9 (CH), 108.4 (CH), 106.7 (CH), 104.8 (CH), 103.6 (CH), 103.4 (CH), 73.9 19 (CH2), 68.0 (CH2), 62.0 (CH2), 56.2 (CH3), 56.2 (CH3), 50.1 (CH2). F NMR (282 MHz, -1 CD3CN) δ –150.73 (20%), –150.78 (80%). IR (in CH2Cl2, cm ) ν = 3462, 2910, 2872, 1638,

1581, 1530, 1482, 1343, 1254, 1164, 1053, 887, 814, 761, 728, 651. UV-Vis (CH3CN, C= -5 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 (4.65).

2-(2-(1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridin-5-yl)ethoxy)ethan-1-ol 2.4i

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 560 (3.54), 529 (3.61), 346 (3.58), 300 (4.17). + HRMS (ESI) calculated for [C25, H25, N2, O4 (M+H) ]: 417.1808. Found: 417.1812.

141

Experimental Part

5-amino-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4j•H ][BF4]

Prepared following the 2nd approach of the general procedure I, using hydrazine monohydrate as primary amine (760 µl, 15.7 mmol). The compound is purified by column chromatography with basic alumina using CH2Cl2/MeOH. The desired product was obtained as an amorphous green solid (230 mg, 533 µmol, 85% yield).

Rf = 0.19 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 7.58–7.52 (m, 3H), 7.46–7.40 (m, 3H), 6.75 (d, J = 7.6 Hz,

1H), 6.57 (ddd, J = 15.6 Hz, 5.3 Hz, 3.4 Hz, 2H), 4.20 (s, 2H, NH2), 3.72 (s, 3H, OCH3), 3.66 13 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 159.5 (C), 158.5 (C), 151.7 (C), 149.1 (C), 145.9 (C), 141.3 (C), 133.5 (C), 132.3 (C), 130.9 (C), 130.5 (C), 120.8 (CH), 119.7 (CH), 116.7 (CH), 115.1 (CH), 111.8 (CH), 106.0 (CH), 102.3 (CH), 100.7 (CH), 98.2 (CH), 55.5 19 (CH3), 55.5 (CH3). F NMR (282 MHz, CD2Cl2) δ –148.86 (20%), –148.92 (80%). UV-Vis -5 (CH3CN, C= 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 (4.65).

1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridin-5-amine 2.4j

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 573 (3.65), 533 (3.69), 349 (3.7), 300 (4.2). + HRMS (ESI) calculated for [C21, H18, N3, O2 (M+H) ]: 344.1393 Found: 344.1397.

142

Experimental Part

5-Allyl-1,13-dimethoxy-5,9-dihydroquinolino[2,3,4-kl]acridin-13b-ylium + tetrafluoroborate salt [2.4k•H ][BF4]

Prepared according to the 2nd approach of the general procedure I; using allylamine as primary amine (1.2 ml, 15.7 mmol). The desired product was obtained as an amorphous green solid (172 mg, 376 µmol, 60% yield).

Rf = 0.35 (Neutral alumina, CH2Cl2/MeOH, 98:2).

1 H NMR (400 MHz, CD2Cl2) δ 7.64–7.50 (m, 4H, 4×CH), 7.42 (t, J = 8.3 Hz, 1H, CH), 6.84 (d, J = 8.5 Hz, 1H, CH), 6.66–6.57 (m, 3H, 3×CH), 6.11 (ddt, J = 17.8 Hz, 10.6 Hz, 3.9 Hz, 1H, CH), 5.40–5.34 (m, 1H, CH), 5.18 (dd, J = 17.2 Hz, 2.3 Hz, 1H, CH), 4.91 (ddt, J = 18.5 Hz, 4.1 Hz, 2.1 Hz, 1H, CH), 4.52 (ddt, J = 18.5 Hz, 3.9 Hz, 2.0 Hz, 1H, CH), 3.70 (2s, 6H, 13 2×OCH3). C NMR (101 MHz, CD2Cl2) δ 159.7 (C), 158.4 (C), 151.7 (C), 148.9 (C), 144.0 (C), 139.5 (C), 133.4 (C), 132.2 (C), 131.0 (C), 130.9 (C), 130.3 (CH), 121.1 (CH), 121.0

(CH), 117.8 (CH), 116.8 (CH2), 115.1 (CH), 113.1 (CH), 107.2 (CH), 102.4 (CH), 100.7 19 (CH), 100.7 (CH), 55.5 (CH3), 52.0 (CH3), 30.2 (CH2). F NMR (CD2Cl2) δ –149.97 (20%), -1 –150.02 (80%). IR (in CH2Cl2, cm ) ν = 2924, 2848, 2191, 1915, 1600, 1561, 1464, 1385, -5 1343, 1252, 1159, 1111, 1069, 973, 905, 724, 641. UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 (4.65).

5-allyl-1,13-dimethoxy-5H-quinolino[2,3,4-kl]acridine 2.4k

-5 UV-Vis (CH3CN, C= 1×10 M) : λmax (log ε): 573 (3.65), 533 (3.69), 349 (3.7), 300 (4.2). + HRMS (ESI) calculated for [C24, H21, N2, O2 (M+H) ]: 369.1517 Found: 369.1593

143

Experimental Part

5-Amino-1,13-dimethoxy-9-propyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b- ylium tetrafluoroborate salt [2.6a][BF4]

To a solution of acridinium salt 2.5j 0.50 g (1.04 mmol) in anhydrous DMF (3 ml) in a red tainted glassware, was added 429 µl (520 µmol, 5 equiv) of n-propylamine. The reaction mixture was degassed with argon and then heated at 90°C without light for 14 hours. After complete consumption of starting acridinium salt 2.5j (monitored by ESI-MS analysis), the green reaction mixture was allowed to cool to 20 °C. The crude product precipitated upon addition of a solution of 50% HBF4 in water (~10 ml). The precipitate was filtered and washed several times with water and collected. Selective precipitation by addition of diethyl ether to a solution of crude product in CH2Cl2 afforded the title green compound. The desired product was obtained after column chromatography with basic alumina using CH2Cl2/MeOH, as an amorphous green solid (442 mg, 832 µmol 80% yield).

Rf = 0.55 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 8.21 (td, J = 8.5, 3.0 Hz, 1H, CH), 8.03 – 7.71 (m, 4H, 4×CH), 7.42 (dd, J = 8.6 Hz, 1.8 Hz, 1H, CH), 7.35 (d, J = 8.9 Hz, 1H, CH), 6.85 (dd, J = 8.6

Hz, 3.5 Hz, 2H, 2×CH), 5.15 (s, 2H, NH2), 4.60 (ddd, J = 16.3 Hz, 11.2 Hz, 5.8 Hz, 1H, CH),

4.46 – 4.29 (m, 1H, CH), 3.76 (d, J = 1.9 Hz, 6H, 2×OCH3), 2.39 – 1.89 (m, 2H, CH2), 1.25 13 (t, J = 7.4 Hz, 3H). C NMR (101 MHz, CD2Cl2) δ 161.9 (C), 161.3 (C), 146.6 (C), 144.30 (C), 144.1 (C), 143.1 (C), 140.6 (C), 138.7 (CH), 138.5 (CH), 138.2 (CH), 120.6 (C), 114.9 (C), 114.4 (C), 109.3 (CH), 109.0 (CH), 106.4 (CH), 106.3 (CH), 104.6 (CH), 104.5 (CH), 19 56.8 (OCH3), 56.7 (OCH3), 21.3 (CH2), 11.7 (CH3). F NMR (282 MHz, CD2Cl2) δ –72.94 -1 (52%), –75.44 (48%). IR (in CH2Cl2, cm ) ν = 2940, 1604, 1593, 1497, 1346, 1260, 1057, -5 842, 764. UV-Vis (CH3CN, C= 1×10 M): λmax (log ε): 625 (4), 580 (3.9), 427 (3.74), 310 + (4.65); HRMS (ESI) calculated for [C24, H24, N3, O2 (M )]: 386.1863 Found: 386.1859.

144

Experimental Part

General Procedure II for The Synthesis of Acridinium Tetrafluoroborate Salts [2.5a- 267 g][BF4].

To a dark purple solution of tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-

45][BF4] 1 g (2 mmol) in acetonitrile (20 ml) was added the corresponding amine (4.9 mmol, 2.5 equiv) at room temperature (20 °C) in ambient condition. The reaction mixture was allowed to stir for 0.5 h. After consumption of starting carbenium ion (reaction monitored by ESI-MS analysis of crude sample) the crude product precipitated upon addition of a solution of 50% HBF4 in water (~10 ml). The precipitate was filtered and washed several times with water and collected. Selective precipitation by addition of diethyl ether to a solution of crude product in CH2Cl2 afforded the title red compound.

9-(2,6-Dimethoxyphenyl)-1,8-dimethoxy-10-propyl-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5a][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (3.0 g, 5.8 mmol, 1.0 equiv), in acetonitrile (60 ml) and propylamine (1.5 ml, 17.8 mmol, 2.5 equiv). Purification by selective precipitation using

CH2Cl2 and Et2O provided 2.5a as red solid (2.67 g, 5.29 mmol, 90%).

1 H NMR (400 MHz, CD2Cl2) δ 8.21 (dd, J = 9.1 Hz, 8.0 Hz, 2H, 2xCH), 7.80 (d, J = 9.1 Hz, 2H, 2xCH), 7.42 (t, J = 8.4 Hz, 1H, CH), 7.02 (d, J = 8.0 Hz, 2H, 2xCH), 6.71 (d, J = 8.4 Hz,

2H, 2×CH), 5.07 – 4.98 (m, 2H, CH2), 3.56 (s, 12H, 4×CH3), 2.35–2.22 (m, 2H, CH2), 1.34 (t, 13 J = 7.4 Hz, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 160.9 (C), 157.8 (C), 155.6 (C), 141.5 (C), 140.1 (C), 129.5 (CH), 119.9 (CH), 119.3 (CH), 108.5 (CH), 106.2 (CH), 103.4 (CH), -5 56.8 (CH3), 55.8 (CH3), 21.4 (CH2), 10.7 (CH3). UV-Vis (CH3CN, C= 1×10 M), λmax (log ε): 397 (3.9), 497 (3.8), 535 (3.7).

267 C. Nicolas, C. Herse, J. Lacour, Tetrahedron Lett. 2005, 46, 4605; B. W. Laursen, F. C. Krebs, Chem. Eur. J.,

145

Experimental Part

9-(2,6-Dimethoxyphenyl)-1,8-dimethoxy-10-methyl-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5b][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (2.0 g, 3.9 mmol, 1.0 equiv), in acetonitrile (40 ml) and methylamine (0.8 ml, 9.7 mmol, 2.5 equiv). Purification by selective precipitation using

CH2Cl2 and Et2O provided 2.5b as red solid (1.7 g, 3.7 mmol, 95%).

1 H NMR (500 MHz, CD2Cl2) δ 8.19 (dd, J(H,H) = 9.1 Hz, 8.0 Hz, 2H, 2×CH), 7.89 (dd, J(H,H) = 9.1 Hz, 0.6 Hz, 2H, 2×CH), 7.42 (t, J(H,H) = 8.4 Hz, 1H, CH), 7.01 (d, J(H,H) =

8.0 Hz, 2H, 2×CH), 6.71 (d, J(H,H) = 8.4 Hz, 2H, 2×CH), 4.69 (s, 3H, NCH3), 3.57 (s, 6H, 13 2×OCH3), 3.56 (s, 6H, 2×OCH3). C NMR (125 MHz, CD2Cl2) δ 161.2 (C), 158.3 (C), 156.0 (C), 142.8 (C), 140.3 (CH), 129.9 (CH), 120.3 (C), 119.6 (C), 109.3 (CH), 106.6 (CH), -5 103.8 (CH), 57.2 (OCH3), 56.2 (OCH3), 40.6 (CH3). UV-Vis (CH3CN, C= 1×10 M), λmax (log ε): 397 (3.9), 497 (3.8), 535 (3.7). M.P: 290°C.

9-(2,6-Dimethoxyphenyl)-10-hexyl-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5c][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (0.30 g, 0.58 mmol, 1.0 equiv), in acetonitrile (6 ml) and hexylamine (115 µl, 870 µmol, 1.5 equiv). Purification by selective precipitation using

CH2Cl2 and pentane provided 2.5c as red solid (0.30 g, 0.56 mmol, 97%).

Rf = 0.3 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (400 MHz, CDCl3) δ 8.32–8.26 (m, 2H, 2×CH), 7.90 (d, J=9.1, 2H, 2×CH), 7.41 (t, J = 8.4 Hz, 1H, CH), 7.08 (d, J = 8.0 Hz, 2H, 2×CH), 6.71 (d, J = 8.4 Hz, 2H, 2×CH), 5.20–

2001, 7, 1773.

146

Experimental Part

5.11 (m, 2H, CH2), 3.60 (s, 12H, 4×OCH3), 2.30–2.21 (m, 2H, CH2), 1.81 (dd, J = 10.3 Hz, 13 5.1 Hz, 2H, CH2), 1.54–1.42 (m, 4H, 2×CH2), 0.98 (t, J = 7.0 Hz, 3H, CH3). C NMR (101

MHz, CDCl3) δ 160.8 (C), 157.3 (C), 141.4 (C), 140.4 (C), 129.5 (C), 119.8 (CH), 119.4

(CH), 108.8 (CH), 106.4 (CH), 103.4 (CH), 99.9 (CH2), 56.9 (OCH3), 56.0 (OCH3), 52.4 19 (CH2), 31.4 (CH2), 28.2 (CH2), 26.2 (CH2), 22.5 (CH2), 14.0 (CH3). F NMR (282 MHz, -1 CDCl3) δ -153.57, -153.60 (20%), -153.62, -153.65 (80%). IR: (in CH2Cl2, cm ): ν = 2940, 2860, 2263, 1579, 1502, 1466, 1432, 1347, 1255, 1161, 1046, 913, 818, 762, 727, 642. UV- -5 Vis (CH3CN, C= 1×10 M), λmax (log ε): 400 (3.83), 499 (3.8), 534 (3.7). HRMS (ESI) + calculated for [C29, H34, N, O4 (M )]: 460.2482 Found: 460.2482. M.P: 238.9°C.

9-(2,6-Dimethoxyphenyl)-10-hexadecyl-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5d][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (0.30 g, 0.58 mmol, 1.0 equiv), and hexadecylamine (269 µl, 870 µmol, 1.5 equiv) in Acetonitrile (3 ml). Purification by selective precipitation using

CH2Cl2 and Et2O provided 2.5d as a non cristalline red solid (0.38 g, 0.56 mmol, 97%).

Rf = 0.4 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1H NMR (400 MHz, CDCl3) δ 8.23 (dd, J = 9.2 Hz, 8.0 Hz, 2H, 2×CH), 7.88 (d, J = 9.1 Hz, 2H, 2×CH), 7.41–7.34 (m, 1H, CH), 7.01 (d, J = 8.1 Hz, 2H, 2×CH), 6.67 (d, J = 8.4 Hz, 2H,

2×CH), 3.57 (s, 12H, 4×OCH3), 2.21 (p, J = 8.3 Hz, 2H, CH2), 1.76 (q, J = 7.6 Hz, 2H, CH2),

1.49 (q, J = 7.4 Hz, 2H, CH2), 1.39 (t, J = 8.2 Hz, 1H, CH), 1.26 (d, J = 2.9 Hz, 23H, 11×CH2 13 + CH), 0.88 (s, 3H, CH3). C NMR (101 MHz, CDCl3) δ 160.8 (C), 157.3(C), 155.5 (C), 141.3 (C), 140.5 (CH), 129.5, 119.8 (C), 119.3 (C), 108.6 (CH), 106.5 (CH), 103.4 (CH), 56.9

(OCH3), 55.9 (OCH3), 52.3 (CH2), 31.9 (CH2), 29.7 (CH2), 29.6 (CH2), 29.6 (CH2), 29.5 19 (CH2), 29.4 (CH2), 29.3 (CH2), 28.2 (CH2), 26.5 (CH2), 22.6 (CH2), 14.1 (CH3). F NMR - (282 MHz, CDCl3) δ –150.82, –150.88 (20%), –152.77, –152.82 (80%).IR: (in acetone, cm 1): ν = 2922, 2852, 1739, 1579, 1503, 1469, 1433, 1160, 1109, 1054, 819, 764. UV-Vis -5 (CH3CN, C= 1×10 M), λmax (log ε): 399 (3.96), 498 (3.92), 531 (3.68).HRMS (ESI) + calculated for [C39, H54, N, O4 (M )]: 600.4047 Found: 600.4044.

147

Experimental Part

9-(2,6-Dimethoxyphenyl)-1,8-dimethoxy-10-phenyl-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5e][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (2.0 g, 3.9 mmol, 1.0 equiv),in acetonitrile (40 ml) and aniline (0.89 ml, 9.80 mmol, 2.5 equiv); the reaction mixture is stirred in acetonitrile during

22 hours. Purification by selective precipitation using CH2Cl2 and Et2O provided 2.5e as red solid (2.17 g, 3.68 mmol, 94 %).

Rf = 0.28 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (500 MHz, CD2Cl2) δ 7.94 (dd, J = 9.0 Hz, 2H, 2×CH), 7.91 – 7.87 (m, 3H, 3×CH), 7.52–7.48 (m, 2H, 2×CH), 7.46 (t, J = 8.4 Hz, 1H, CH), 7.02–6.99 (m, 2H, 2×CH), 6.90 (dd, J

= 9.0 Hz, 2H, 2×CH), 6.76 (d, J = 8.4 Hz, 2H, 2×CH), 3.63 (s, 6H, 2×OCH3), 3.60 (s, 6H, 13 2×OCH3). C NMR (126 MHz, CD2Cl2) δ 160.9 (C), 160.0 (C), 156.0 (C), 143.0 (C), 139.8 (C), 138.7 (C), 132.0 (C), 131.9 (CH), 130.2 (CH), 127.9 (CH), 120.0 (CH), 119.3 (CH), - 111.0 (CH), 106.7 (CH), 103.9 (CH), 57.3 (OCH3), 56.2 (OCH3). UV-Vis (CH3CN, C= 1×10 5 M, λmax (logε)): 401 (3.77), 501 (3.74), 534 (3.72).

10-Benzyl-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5f][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (0.25 g, 0.50 mmol, 1.0 equiv), and benzylamine (0.16 ml,

1.50 mmol, 3 equiv) in acetonitrile (3 ml). Purification by selective precipitation using CH2Cl2 and Et2O provided 2.5f as red solid (0.22 g, 0.46 mmol, 91%).

Rf = 0.28 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (400 MHz, CDCl3) δ 8.08 (dd, J = 9.1 Hz, 8.0 Hz, 2H, 2×CH), 7.71 (d, J = 9.1 Hz, 2H, 2×CH), 7.43 – 7.35 (m, 4H, 4×CH), 7.25 – 7.21 (m, 2H, 2×CH), 6.99 (d, J = 8.0 Hz, 2H,

148

Experimental Part

2×CH), 6.69 (d, J = 8.4 Hz, 2H, 2×CH), 6.46 (s, 2H, CH2), 3.62 (s, 6H, 2×OCH3), 3.58 (s, 6H, 13 2×OCH3). C NMR (126 MHz, CDCl3) δ 160.87 (C), 158.85 (C), 155.64 (C), 142.30 (C), 140.63 (CH), 132.94 (CH), 129.67 (CH), 129.52 (CH), 128.57 (CH), 125.79 (CH), 120.04

(C), 119.24 (C), 109.42 (CH), 106.63 (CH), 103.41 (CH), 56.99 (OCH3), 56.39 (OCH3), 55.98 19 - (OCH3). F NMR (282 MHz, CDCl3) δ –153.25 (20%), –153.30 (80%). IR: (in CHCl3, cm 1): ν = 2942, 2835, 2264, 1578, 1501, 1465, 1433, 1344, 1257, 1161, 1050, 910, 821, 759, + 723, 643. HRMS (ESI) calculated for [C30, H28, N, O4 (M )]: 466.2016 Found: 466.2013. UV- -5 Vis (CH3CN, C = 1×10 M), λmax (log ε): 408 (3.77), 505 (3.74), 536 (3.62). M.P: 216.7 °C

9-(2,6-Dimethoxyphenyl)-10-(2-(dimethylamino)ethyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate salt [2.5g][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (0.50 g, 0.97 mmol, 1.0 equiv), in acetonitrile (6 ml) and

(0.26 ml, 2.44 mmol, 2.5 equiv). Purification by selective precipitation using CH2Cl2 and

Et2O provided 2.5g as red solid (0.42 g, 0.77 mmol, 80%.

Rf = 0.3 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (500 MHz, CD2Cl2) δ 8.21 (t, J = 9.1 Hz, 2H, 2×CH), 7.89 (d, J = 9.1 Hz, 2H, 2×CH), 7.41 (t, J = 8.4 Hz, 1H), 7.04 (d, J = 8.0 Hz, 2H, 2×CH), 6.71 (d, J = 8.4 Hz, 2H, 2×CH), 5.26–5.11 (m, 2H), 3.56 (s, 12H), 3.22–2.99 (m, 2H), 2.47 (s, 6H). 13C NMR (101

MHz, CD2Cl2) δ 160.9 (C), 158.1 (C), 155.6 (C), 141.8 (C), 140.3 (C), 129.6 (C), 119.9

(CH), 119.3 (CH), 108.8 (CH), 106.4 (CH), 103.4 (CH), 56.9 (CH2), 56.5 (OCH3), 55.8 19 (OCH3), 53.9 (CH2), 51.5 (CH3), 45.7 (CH3). F NMR (282 MHz, CDCl3) δ –153.50 (20%), + –153.40 (80%). HRMS (ESI) calculated for [C27, H31, N2, O4 (M )]: 447.2278 Found: -5 447.2286. UV-Vis (CH3CN, C= 1×10 M, λmax (logε)): 400 (3.77), 500 (3.69), 533 (3.6).

149

Experimental Part

9-(2,6-Dimethoxyphenyl)-10-(2-hydroxyethyl)-1,8-dimethoxy-9,10-dihydroacridin-9- ylium tetrafluoroborate salt [2.5h][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (2.0 g, 3.9 mol, 1.0 equiv), in acetonitrile (20 ml) and (0.6 ml, 4.4 mol, 2.5 equiv). Purification by selective precipitation using CH2Cl2 and Et2O provided 2.5h as red solid (1.28 g, 2.53 mmol, 65%).

Rf = 0.1 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 8.08 (t, J = 8.5 Hz, 2H), 7.98 (d, J = 9.1 Hz, 2H), 7.32 (t, J = 8.4 Hz, 1H), 6.89 (d, J = 7.9 Hz, 2H), 6.62 (d, J = 8.4 Hz, 2H), 5.23 (t, J = 6.2 Hz, 2H 4.32 (t, 13 J = 6.2 Hz, 2H), 3.79 (s, 1H), 3.47 (d, J = 7.2 Hz, 12H). C NMR (101 MHz, CD2Cl2) δ 160.7 (C), 157.8 (C), 155.6 (C), 142.2 (C), 139.9 (CH), 129.4 (CH), 119.9 (C), 119.4 (C), 19 109.4 (CH), 106.1 (CH), 103.4 (CH), 59.4 (CH2), 56.8 (OCH3), 55.8 (OCH3). F NMR (282 -1 MHz, CD2Cl2) δ –153.1 (20%), –153.15 (80%) IR: (in CHCl3, cm ): ν = 3262, 3015, 2940, 2840, 2259, 1579, 1501, 1465, 1431, 1345, 1255, 1162, 1103, 1054, 912, 817, 763, 728, 650. + HRMS (ESI) calculated for [C25, H26, N, O5 (M )]: 420.1806 Found: 420.1813. UV-Vis -5 (CH3CN, C= 1×10 M), λmax (log ε): 400 (3.75), 500 (3.69), 533 (3.65).

9-(2,6-Dimethoxyphenyl)-10-(2-(2-hydroxyethoxy)ethyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate salt [2.5i][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (0.30 g, 0.58 mmol, 1.0 equiv), in acetonitrile (6 ml) and

(0.017 ml, 1.47 mmol, 2.5 equiv). Purification by selective precipitation using CH2Cl2 and

Et2O provided 2.5i as red solid (0.25 g, 0.46 mmol, 80%).

1 Rf = 0.02 (Neutral alumina, CH2Cl2- MeOH, 98:2). H NMR (400 MHz, CDCl3) δ 8.22–8.12 (m, 4H, 4×CH), 7.34 (t, J = 8.4 Hz, 1H, CH), 6.96 (d, J = 7.6 Hz, 2H, 2×CH), 6.63 (d, J = 8.4

150

Experimental Part

Hz, 2H), 5.50 (t, J = 5.5 Hz, 2H, CH2), 4.39 (t, J = 5.4 Hz, 2H, CH2), 3.73 – 3.62 (m, 4H, 13 2×CH2), 3.52 (2s, 12H, 4×OCH3). C NMR (101 MHz, CDCl3) δ 160.5 (C), 157.5 (C), 155.6 (C), 142.3 (C), 140.2 (CH), 129.4 (CH), 119.8 (C), 119.4 (C), 110.0 (CH), 106.3 (CH), 19 103.4 (CH), 73.2 (CH2), 68.5 (CH2), 61.5 (CH2), 56.9 (OCH3), 55.9 (CH2), 52.5 (OCH3). F -1 NMR (282 MHz, CDCl3) δ –153.05 (20%), –153.10 (80%). IR: (in CHCl3, cm ): ν = 3262, 3015, 2940, 2840, 2259, 1579, 1501, 1465, 1431, 1345, 1255, 1162, 1103, 1054, 912, 817, -5 763, 728, 650. UV-Vis (CH3CN, C= 1×10 M), λmax (log ε): 400 (3.91), 500 (3.81), 533 + (3.76). HRMS (ESI) calculated for [C27, H30, N, O6 (M )]: 464.2068 Found: 464.2077.

10-Amino-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10-dihydroacridin-9-ylium

Tetrafluoroborate salt [2.5j][BF4]

Preparing according the general procedure II using 10.0 g (19.6 mmol, 1 mol. eq.) of tris(2,6- dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] in acetonitrile (200 ml). and 3.0 ml of hydrazine monohydrate 64-65% (49 mmol, 2.5 mol. eq.). Purification by selective precipitation using CH2Cl2 and Et2O provided 2.5j as red solid (8.90 g, 18.62 mmol, 95%).

Rf = 0.32 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (400 MHz, CDCl3) δ 8.48 (d, J =9.1 Hz, 2H, 2×CH), 8.17 (t, J = 8.6 Hz, 2H, 2×CH), 7.41 (t, J = 8.4 Hz, 1H, CH), 6.98 (d, J = 8.0 Hz, 2H, 2×CH), 6.70 (d, J = 8.4 Hz, 2H, 13 2×CH), 6.22 (s, 2H, NH2), 3.56 (d, J=3.0, 12H, 4×OCH3). C NMR (101 MHz, CDCl3) δ 160.3 (C), 156.8 (C), 155.7 (C), 143.6 (C), 139.6 (CH), 129.5 (CH), 119.6 (CH), 119.3 (CH), 19 109.1 (CH), 106.3 (CH), 103.3 (CH), 56.7 (OCH3), 55.8 (OCH3). F NMR (282 MHz, -1 CDCl3) δ –151.61 (20%), –151.66 (80%). IR: (in CH2Cl2, cm ): ν = 3372, 3295, 2944, 1591, 1466, 1357, 1250, 1187, 1081, 1013, 861, 815, 764, 702, 648. HRMS (ESI) calculated for + -5 [C23, H23, N2, O4 (M )]: 391.1652. Found: 391.1650. UV-Vis (CH3CN, C= 1×10 M), λmax (log ε): 397 (3.5), 500 (3.44), 533 (3.32). M.P: 281.6°C

151

Experimental Part

10-Allyl-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [2.5k][BF4]

Prepared according to general procedure II using tris(2,6-dimethoxyphenyl)carbenium tetrafluoroborate salt [I-45][BF4] (0.5 g, 0.98 mmol, 1.0 equiv), in acetonitrile (10 ml) and allylamine (0.3 ml, 3.43 mmol, 3.5 equiv). Purification by selective precipitation using

CH2Cl2 and Et2O provided 2.5k as red solid (0.4 g, 2.9 mmol, 94%).

Rf = 0.39 (Neutral alumina, CH2Cl2- MeOH, 98:2). 1 H NMR (400 MHz, CDCl3) δ 7.75 (dd, J = 9.1 Hz, 8.0, 2H, 2×CH), 7.33 (d, J = 9.1 Hz, 2H, 2×CH), 7.01 (t, J = 8.4 Hz, 1H, CH), 6.63 (d, J = 8.1 Hz, 2H, 2×CH), 6.31 (d, J = 8.4 Hz, 2H,

CH2), 6.00 (ddt, J = 17.0 Hz, 10.7, 4.0, 1H, CH), 5.07 (d, J = 10.8 Hz, 1H, CH), 4.67 (d, J = 13 17.4 Hz, 1H, CH), 3.16 (s, 12H, 4×OCH3). C NMR (101 MHz, CDCl3) δ 160.7 (C), 158.3

(C), 155.5 (C), 141.8 (C), 140.5 (CH), 129.6 (C), 129.2 (C), 119.8 (CH2), 119.2 (CH), 118.9 19 (CH), 109.2 (CH), 106.6 (CH), 103.4 (CH), 56.9 (OCH3), 55.9 (CH2), 55.0 (OCH3). F NMR -1 (282 MHz, CDCl3) δ –153.49 (20%), –153.54 (80%). IR (in CHCl3, cm ): ν = 2941, 2830, 2264, 1579, 1466, 1430, 1345, 1257, 1164, 1048, 909, 816, 759, 722, 641. HRMS (ESI) + -5 calculated for [C26, H26, N, O4 (M )]: 416.1856 Found: 416.1849. UV-Vis (CH3CN, C= 1×10

M, λmax (logε)): 400 (3.71), 500 (3.66), 533 (3.57). M.P: 224.8°C

152

Experimental Part

Synthesis, Properties and Application of pH-Sensitive and Fluorescent Diazaoxatriangulenes as Late Endosomes Probes

+ General Procedure III For The Synthesis of Compounds [3.3•H ][PF6]

Quinacridinium salt 2.4 (2.31 g, 5.2 mmol) was added to molten pyridinium hydrochloride (14.95 g, 130 mmol) in a sealed tube. The reaction mixture was heated at 150 °C for 4 hours. After complete consumption of quinacridinium 2.4 (monitored by ESI-MS analysis), the reaction mixture was allowed to cool to 20 °C. Then the crude solid was dissolved in 1M aqueous solution of KPF6 (~20 ml) and the aqueous phase extracted three times with CH2Cl2

(500 mL). The organic phases were combined dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with silica gel and

CH2Cl2/MeOH as eluent and then washed with 0.1 M solution of KPF6 affording the title dark purple compound.

General Procedure IV For The Synthesis of Compounds [3.4•H+][TFA]

+ [3.3•H ][PF6] was dissolved in a minimum amount of CH2Cl2 then the organic phase is washed with a saturated solution of NaHCO3 (~ 20 ml). The combined organic phases were then washed with 1 M solution of CF3CO2H (~20 ml). The slightly red aqueous phase were extracted (3 times) with CH2Cl2. The organic phase was dried over Na2SO4 and the solvent removed under reduced pressure affording compound [3.4•H+][TFA] as red salt

153

Experimental Part

8-hexadecyl-8,12-dihydro-3a2H-benzo[ij]xantheno[1,9,8-cdef][2,7]naphthyridin-3a2- + ylium hexafluorophosphate [3.3a•H ][PF6]

Prepared following general procedure III; using quinacridinium 2.4d (2.3 g, 5.2 mmol) and molten pyridinium hydrochloride (15 g, 130 mmol). The desired product was obtained as an amorphous dark orange-red solid (854.25 mg, 1.87 mmol, 36% yield).

Rf = 0.25 (Basic alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 10.38 (s, 1H, NH), 8.31 (t, J = 8.6 Hz, 1H, CH), 8.13 (t, J = 8.5 Hz, 2H, 2×CH ), 7.49 (d, J = 8.8 Hz, 2H, 2×CH), 7.41 (d, J = 8.7 Hz, 2H, 2×CH), 7.38 (d,

J = 8.2 Hz, 2H, 2×CH), 4.52 (dd, J = 9.5, 7.1 Hz, 2H, CH2), 2.01 (p, J = 8.0 Hz, 2H, CH2),

1.66 (p, J = 7.4 Hz, 2H), 1.51 (t, J = 7.7 Hz, 2H, CH2), 1.31 (s, 25H), 0.92 (t, J = 6.7 Hz, 3H, 13 CH3). C NMR (101 MHz, CD2Cl2) δ 152.8 (C), 141 (C), 139.9 (C), 139.8 (C), 139.7 (C), 139.68 (C), 138.7 (CH), 111.6 (CH), 108.9 (CH), 108.8 (CH), 107.7 (CH), 105.7 (CH), 48.4

(CH2), 31.9 (CH2), 29.7 (CH2), 29.6 (CH2), 29.6 (CH2), 29.6 (CH2), 29.5 (CH2), 29.5 (CH2),

29.35 (CH2), 29.3 (CH2), 29.3 (CH2), 29.1 (CH2), 26.7 (CH2), 25.63 (CH2), 22.7 (CH2), 13.9 19 -1 (CH3). F NMR (282 MHz, CD2Cl2) δ –69.89 (50%), –72.41 (50%). IR (in CH2Cl2, cm ) ν = 3236, 3121, 2921, 2851, 1649, 1617, 1523, 1456, 1339, 1256, 1156, 1046, 819, 772, 629. + HRMS (ESI) calculated for [C35, H43, N2, O (M )]: 507.3370 Found: 507.3364

8-hexadecyl-8,12-dihydro-3a2H-benzo[ij]xantheno[1,9,8-cdef][2,7]naphthyridin-3a2- ylium 2,2,2-trifluoroacetate [3.4a•H+][TFA]

Prepared following the general procedure IV using 200.8 mg (0.44 mmol) of triangulene + [3.3a•H ][PF6]. The product was obtained as orange-red solid (182.48 mg, 0.43 mmol, 98%).

19 F NMR (282 MHz, CD2Cl2) δ –75.79

154

Experimental Part

8-phenyl-8,12-dihydro-3a2H-benzo[ij]xantheno[1,9,8-cdef][2,7]naphthyridin-3a2-ylium + hexafluorophosphate [3.3b•H ][PF6]

Prepared following general procedure III; using quinacridinium 7b (152.60 mg, 0.31 mmol) and 895.58 mg (7.75 mmol) molten pyridinium hydrochloride. The desired product was obtained as an amorphous dark orange-red solid (146.97 mg, 0.29 mmol, 94% yield).

Rf = 0.32 (Basic alumina, CH2Cl2/MeOH, 98:2). 1H NMR (500 MHz, DMSO-d6) δ 13.53 (s, 1H, NH), 8.06–7.76 (m, 6H, 6×CH), 7.60 (d, J = 7.2 Hz, 2H, 2×CH), 7.36 (d, J = 8.4 Hz, 1H, CH), 7.31 (d, J = 8.2 Hz, 1H, CH), 7.27 (dd, J = 8.2, 5.3 Hz, 2H, 2×CH), 6.47 (d, J = 8.7 Hz, 1H, CH), 6.30 (d, J = 8.3 Hz, 1H, CH). 13C NMR (126 MHz, DMSO-d6) δ 152.1 (C), 151.5 (C), 141.4 (C), 141.15 (C), 140.3 (C), 140.2 (C), 139.4 (C), 138.8 (CH), 138.2 (CH), 138.2 (CH), 137 (C), 132.1 (CH), 130.7 (CH), 128.4 (CH), 110.8 (CH), 110.3 (CH), 110.1 (CH), 108.5 (CH), 107.4 (CH), 107.3 (CH), 106.9 (CH), 106.7 (CH), 105.4 (CH).19F NMR (282 MHz, DMSO-d6) δ –68.19 (50%), –70.71 (50%). IR -1 (in CH2Cl2, cm ) ν = 3327, 1652, 1620, 1452, 1341, 1302, 1264, 1175, 1106, 839, 770, 738, + 694, 627, 555. HRMS (ESI) calculated for [C25, H15, N2, O (M )]: 359.1179 Found: 359.1176

8-phenyl-8,12-dihydro-3a2H-benzo[ij]xantheno[1,9,8-cdef][2,7]naphthyridin-3a2-ylium 2,2,2-trifluoroacetate [3.4b•H+][TFA]

Prepared following the general procedure IV using 100.5 mg (0.2 mmol) of triangulene + [3.3b•H ][PF6]. The product was obtained as orange-red solid (91.65 mg, 0.19 mmol, 97% yield).

19F NMR (282 MHz, DMSO-d6) δ –74.50

155

Experimental Part

8-propyl-8,12-dihydro-3a2H-benzo[ij]xantheno[1,9,8-cdef][2,7]naphthyridin-3a2-ylium + hexafluorophosphate [3.3c•H ][PF6]

Prepared following general procedure III; using diaza[4]quinacridinium 7c (500.60 mg, 1.09 mmol) and 3.20 g (27.30 mmol) pyridinium hydrochloride. The desired product was obtained as an amorphous dark orange-red solid (410.15 mg, 0.87 mmol, 80% yield).

Rf = 0.18 (Basic alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (500 MHz, CD2Cl2) δ 7.53 (q, J = 8.1 Hz, 2H, 2 CH), 7.38 – 7.30 (m, 2H, 2 CH), 7.20 (d, J = 8.5 Hz, 1H, CH), 6.68 (dd, J = 8.0, 5.3 Hz, 2H, 2 CH), 6.63 (d, J = 8.2 Hz, 1H,

CH), 6.38 (d, J = 7.8 Hz, 1H, CH), 3.88 – 3.59 (m, 2H, CH2), 2.94 (s, 1H, NH), 1.78 (h, J = 13 7.5 Hz, 2H, CH2), 1.09 (t, J = 7.4 Hz, 3H, CH3). C NMR (126 MHz, CD2Cl2) δ 153.2 (C), 151.8 (C), 150.52 (C), 148.9 (C), 140.4 (C), 140.2 (C), 134.2 (CH), 133.9 (CH), 132.7 (C), 132.7 (CH), 119.3 (CH), 116.2 (CH), 112.7 (C), 109.1 (C), 107.4 (C), 107.3 (CH), 107.1 19 (CH), 103.8 (CH), 99.7 (CH), 48.0 (CH2), 18.6 (CH2), 11.2 (CH3). F NMR (282 MHz, -1 CD2Cl2) δ –70.23 (50%), –72.75 (50%). IR (in CH2Cl2, cm ) ν 2925, 1610, 1525, 1457,

1384, 1351, 1250, 1154, 1042, 852, 755, 611. HRMS (ESI) calculated for [C22, H17, N2, O (M+)]: 325.1335 Found: 325.1336

8-propyl-8,12-dihydro-3a2H-benzo[ij]xantheno[1,9,8-cdef][2,7]naphthyridin-3a2-ylium 2,2,2-trifluoroacetate [3.4c•H+][TFA]

Prepared following the general procedure IV using 150.50 mg (0.32 mmol) of triangulene + [1c•H ][PF6]. The product was obtained as orange-red solid (127.14 mg, 0.29 mmol, 90%).

19 F NMR (282 MHz, CD2Cl2) δ -75.55.

156

Experimental Part

N-aminoacridinium Ion as Nitrogen Source For The Synthesis of Unprotected Aziridines and Sulfoximines

General Procedure IV For Aziridination of Alkenes [4.41][BF4].

To a solution of olefin (0.84 mmol) and N-aminoacridinium [2.5j][BF4] (0.88 mmol, 1.05 equiv) in 3 ml of CH2Cl2, was added dropwise a solution of PIDA (0.92 mmol, 1.1 equiv) in 3 ml of CH2Cl2. The reaction mixture was allowed to stir at 23 °C for 2-4 hours. Upon completion (monitored by ESI-MS analysis of crude sample) 10 ml of water was added, and the product extracted with CH2Cl2 (3×20ml). The combined organic phases are dried over

Na2SO4, and concentrated. The product was purified by column chromatography using basic alumina. 100% AcOEt, then a mixture of CH2Cl2/MeOH were used as eluents. The product was dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound

10-(2-benzoyl-3-phenylaziridin-1-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate [4.41a][BF4]

Prepared according the general procedure IV, using 150.0 mg (0.7 mmol) (E)-chalcone,

353.90 mg (0.74 mmol) N-aminoacridinium 2.5j in 3 ml CH2Cl2 and 248.01 mg (0.77 mmol) of PIDA in 3 ml CH2Cl2. The desired product was isolated as a red solid (438.07 mg, 0.64 mmol, 92%).

Rf = 0.75 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2) δ 8.13 (d, J = 8.8 Hz, 1H, CH), 8.01–7.91 (m, 1H, CH), 7.87 (dd, J = 8.5, 1.3 Hz, 2H, 2×CH), 7.83–7.77 (m, 1H), 7.75–7.71 (m, 2H, 2×CH), 7.68 (d, J =

157

Experimental Part

8.9 Hz, 1H, CH), 7.65–7.56 (m, 4H, 4×CH), 7.48 (t, J = 7.9 Hz, 2H, 2×CH), 7.43 (t, J = 8.4 Hz, 1H, CH), 6.99 (d, J = 8.0 Hz, 1H, CH), 6.76 (d, J = 8.1 Hz, 1H, CH), 6.72 (dd, J = 8.3, 2.5 Hz, 2H, 2×CH), 5.31 (d, J = 5.0 Hz, 1H, NCH), 4.57 (d, J = 4.8 Hz, 1H, NCH), 3.65 (s, 13 3H, OCH3), 3.62 (s, 6H, 2×OCH3), 3.51 (s, 3H, OCH3). C NMR (126 MHz, CD2Cl2) δ 188.7 (C), 161.3 (C), 161.2 (C), 156.8 (C), 156.0 (C), 155.8 (C), 140.5 (C), 139.5 (CH), 139.4 (CH), 139.0 (CH), 136.0 (CH), 134.9 (CH), 133.0 (CH), 130.5 (CH), 130.1 (CH), 129.9 (C), 129.3 (C), 129.3 (C), 128.7 (C), 127.6 (C), 120.7 (C), 119.9 (C), 119.2 (C), 109.3 (CH), 107.9

(CH), 106.8 (CH), 106.6 (CH), 104.4 (CH), 103.4 (CH), 60.3 (CH), 57.2 (CH), 57.1 (OCH3), 19 56.6 (OCH3), 56.1 (OCH3), 55.7 (OCH3). F NMR (282 MHz, CD2Cl2) δ –156.14 (20%), – -1 156.19 (80%). IR (in CH2Cl2, cm ) ν = 3628, 2939, 2839, 1669, 1597, 1577, 1502, 1470, 1433, 1358, 1285, 1252, 1177, 1084, 1057, 977, 883, 773, 733, 704. HRMS (ESI) calculated + for [C38, H33, N2, O5 (M )]: 597.2384. Found: 597.2384.

10-2-benzoyl-3-(m-tolyl)aziridin-1-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate [4.41b][BF4]

Preparing according the general procedure IV using 200.0 mg (0.9 mmol) (E)-m-tolyl- chalcone and 449.55 mg (0.94 mmol) of N-aminoacridinium 2.5j in 4 ml CH2Cl2 and 331.76 mg (1.03 mmol) of PIDA in 4 ml CH2Cl2. The desired product was isolated as a red solid (468.00 mg, 0.67 mmol, 75%).

Rf = 0.63 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.18 (d, J = 9.0 Hz, 1H, CH), 7.97 (dd, J = 9.0, 8.0 Hz, 1H, CH), 7.92–7.86 (m, 2H, 2×CH), 7.84–7.76 (m, 1H, CH), 7.68 (d, J = 8.9 Hz, 1H, CH), 7.62 (t, J = 7.2, Hz, 1H, CH), 7.56 (s, 1H, CH), 7.53–7.35 (m, 6H, 6×CH), 7.02 (d, J = 8.0 Hz, 1H, CH), 6.76 (d, J = 8.1 Hz, 1H, CH), 6.73 (d, J = 8.5 Hz, 2H, 2×CH), 5.34 (d, J = 5.0 Hz, 1H,

NCH), 4.52 (d, J = 4.9 Hz, 1H, NCH), 3.66 (s, 3H, OCH3), 3.63 (s, 6H, 2×OCH3), 3.51 (s, 3H, 13 OCH3), 2.50 (s, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 188.5 (C), 160.9 (C), 160.7 (C),

158

Experimental Part

156.4 (C), 155.5 (C), 155.4 (C), 140.2 (C), 139.6 (CH), 139.1 (C), 139.0 (C), 138.6 (CH), 135.7 (C), 134.5 (CH), 132.6 (C), 130.8 (CH), 129.7 (CH), 129.3 (CH), 128.9 (CH), 128.4 (CH), 127.7 (CH), 124.5 (CH), 120.3 (C), 119.5 (C), 118.9 (C), 108.9 (CH), 107.6 (CH),

106.5 (CH), 106.3 (CH), 104.1 (CH), 103.1 (CH), 60.0 (NCH), 56.8 (NCH), 56.7 (OCH3), 19 56.2 (OCH3), 55.8 (OCH3), 55.3 (OCH3), 21.1 (CH3). F NMR (282 MHz, CD2Cl2) δ – -1 152.34 (20%), –152.39 (80%). IR: (in CH2Cl2, cm ): ν = 2940, 2839, 1669, 1597, 1575, 1502, 1468, 1432, 1357, 1303, 1250, 1230, 1107, 1031, 977, 814, 775, 730, 703, 655.

10-2-benzoyl-3-(3-chlorophenyl)aziridin-1-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-

9,10-dihydroacridin-9-ylium tetrafluoroborate[4.41c][BF4]

Prepared according the general procedure IV, using 110.00 mg (0.45 mmol) (E)-m-Cl-phenyl- chalcone and 224.77 mg (0.47 mmol) of N-aminoacridinium 2.5j in 1.6 ml CH2Cl2 and 157.83 mg (0.49 mmol) of PIDA in 1.6 ml CH2Cl2. The desired product was isolated as a red solid (316.33 mg, 0.44 mmol, 99%).

Rf = 0.68 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.15 (dd, J = 8.9, 0.9 Hz, 1H, CH), 7.99 (dd, J = 9.0, 8.0 Hz, 1H, CH), 7.89 (dd, J = 8.5, 1.3 Hz, 2H, 2×CH), 7.80 (dd, J = 8.9, 8.1 Hz, 1H, CH), 7.74 (d, J = 1.2 Hz, 1H, CH), 7.71 – 7.52 (m, 5H, 5×CH), 7.48 (dd, J = 8.3, 7.4 Hz, 2H, 2×CH), 7.43 (t, J = 8.4 Hz, 1H, CH), 7.01 (dd, J = 8.3, 0.9 Hz, 1H, CH), 6.76 (dd, J = 8.3, 0.9 Hz, 1H, CH), 6.73 (d, J = 2.7 Hz, 1H, CH), 6.71 (d, J = 2.7 Hz, 1H, CH), 5.34 (d, J = 2.3 Hz, 1H, NCH),

4.55 (d, J = 4.8 Hz, 1H, NCH), 3.65 (s, 3H, OCH3), 3.63 (s, 6H, 2×OCH3), 3.51 (s, 3H, 13 OCH3). C NMR (101 MHz, CD2Cl2) δ 188.0 (C) , 161.0 (C), 160.8 (C), 156.4 (C), 155.8 (C), 155.4 (C), 140.40 (CH), 139.1 (CH), 138.9 (C), 138.8 (C), 135.5 (CH), 135.3 (CH), 134.9 (CH), 134.6 (CH), 131.0 (CH), 130.2 (CH), 129.8 (CH), 129.0 (CH), 128.4 (CH), 127.16 (CH), 125.7 (CH), 120.3 (C), 119.5 (C), 118.8 (C), 108.5 (CH), 107.5 (CH), 106.5 (CH),

106.3 (CH), 104.1 (CH), 103.0 (CH), 58.9 (CH), 56.8 (CH), 56.7 (OCH3), 56.2 (OCH3), 55.7

159

Experimental Part

19 (OCH3), 55.3 (OCH3). F NMR (282 MHz, CD2Cl2) δ –156.14 (20%), –156.19 (80%). IR: -1 (in CH2Cl2, cm ): ν = 2940, 2843, 1670, 1593, 1502, 1472, 1433, 1358, 1286, 1255, 1146,

1109, 1087, 1060, 978, 814, 775, 732, 699, 601. HRMS (ESI) calculated for [C38, H32, Cl, N2, + O5 (M )]: 631.1994. Found: 631.1998.

10-2-benzoyl-3-(4-nitrophenyl)aziridin-1-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-

9,10-dihydroacridin-9-ylium tetrafluoroborate[4.41d][BF4]

Preparing according the general procedure IV using 200.00 mg (0.79 mmol) (E)-p- nitrophenyl-chalcone and 396.95 mg (0.83 mmol) N-aminoacridinium 2.5j in 3.5 ml CH2Cl2 and 293.11 mg (0.91 mmol) of PIDA in 3.5 ml CH2Cl2. The desired product was isolated as a red solid (87. mg, 0.12 mmol, 16%).

Rf = 0.75 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.42 (d, J = 8.8 Hz, 2H, 2×CH), 8.03–7.99 (m, 4H, 4×CH), 7.96 (dd, J = 8.9, 8.0 Hz, 1H, CH), 7.82 (dd, J = 8.9, 8.1 Hz, 1H, CH), 7.52–7.38 (m, 5H, 5×CH), 7.02 (d, J = 8.2 Hz, 1H), 6.77–6.68 (m, 4H, 4×CH), 5.69 (d, J = 4.9 Hz, 1H, NCH),

4.65 (d, J = 4.8 Hz, 1H, NCH), 3.66 (s, 3H, OCH3), 3.63 (d, J = 1.6 Hz, 6H, 2×OCH3), 3.51 13 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 188.1 (C), 161.0 (C), 160.7 (C), 160.4 (C), 156.4 (C), 155.9 (C), 155.8 (C), 155.4 (C), 148.9 (C), 140.6 (CH), 140.0 (CH), 139.6 (CH), 139.1 (CH), 138.8 (CH), 138.8 (CH), 135.4 (CH), 134.6 (CH), 131.5 (CH), 129.8 (CH), 129.7 (CH), 128.9 (CH), 128.8 (CH), 128.8 (CH), 124.5 (CH), 120.2 (C), 119.5 (C), 118.8 (C), 108.3 (CH), 108.0 (CH), 106.6 (CH), 106.3 (CH), 104.1 (CH), 103.4 (CH), 103.0 (CH), 58.58 19 (CH), 56.9 (CH), 56.7 (OCH3), 56.2 (OCH3), 55.8 (OCH3), 55.4 (OCH3). F NMR (282 -1 MHz, CD2Cl2) δ –151.57 (20%), –151.63 (80%). IR: (in CH2Cl2, cm ): ν = 2940, 2839, 1669, 1597, 1575, 1502, 1468, 1432, 1357, 1303, 1250, 1230, 1107, 1031, 977, 814, 775, 730, + 703, 655. HRMS (ESI) calculated for [C38, H32, N3, O7 (M )]: 642.2235. Found: 642.2240.

160

Experimental Part

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((2S,3R)-2-(4-methoxybenzoyl)-3- phenylaziridin-1-yl)-9,10-dihydroacridin-9-ylium tetrafluoroborate [4.41e][BF4]

Prepared according the general procedure IV using 250.20 mg (1.05 mmol) (E)-p-methoxy- chalcone and 526.07 mg (1.10 mmol) N-aminoacridinium 2.5j in 4.5 ml CH2Cl2 and 370.41 mg (1.15 mmol) of PIDA in 4.5 ml CH2Cl2. The desired product was isolated as a red solid (300.09 mg, 0.42 mmol, 40%).

Rf = 0.45 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.30 (d, J = 9.0 Hz, 1H), 7.98 (d, J = 9.0 Hz, 2H), 7.93 (dd, J = 9.0, 8.0 Hz, 1H, CH), 7.84 (dd, J = 8.9, 8.1 Hz, 1H, CH), 7.78–7.67 (m, 1H, CH), 7.66 – 7.48 (m, 4H, 4CH), 7.44 (t, J = 8.4 Hz, 1H, CH), 7.02 (d, J = 8.2 Hz, 1H, CH), 6.96 (d, J = 9.0 Hz, 2H, 2CH), 6.78 – 6.74 (m, 2H, 2CH), 6.74–6.72 (m, 1H, CH), 5.44 (d, J = 5.0 Hz, 1H,

NCH), 4.53 (d, J = 4.9 Hz, 1H, NCH), 3.85 (s, 3H, OCH3), 3.67 (s, 3H, OCH3), 3.63 (s, 3H, 13 OCH3), 3.51 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 186.5 (C), 164.8 (C), 160.8 (C), 160.5 (C), 156.4 (C), 155.5 (C), 155.0 (C), 140.0 (CH), 139.1 (CH), 138.9 (C), 138.5 (C), 133.0, 131.2 (CH), 129.9 (CH), 129.7 (CH), 129.4 (CH), 128.8 (CH), 127.5 (CH), 120.2 (C), 119.4 (C), 119.0 (C), 114.2 (CH), 108.9 (CH), 108.2 (CH), 106.5 (CH), 106.3 (CH), 104.1

(CH), 103.1 (CH), 59.5 (OCH3), 56.9 (CH), 56.7 (CH), 56.3 (OCH3), 55.8 (OCH3), 55.7 19 (OCH3), 55.1 (OCH3). F NMR (282 MHz, CD2Cl2) δ –152.41 (20%), –152.46 (80%). + HRMS (ESI) calculated for [C39, H35, N2, O6 (M )]: 627.2490. Found: 627.2491.

161

Experimental Part

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((2S,3R)-2-(3-methoxybenzoyl)-3- phenylaziridin-1-yl)-9,10-dihydroacridin-9-ylium tetrafluoroborate[4.41f][BF4]

Prepared according the general procedure IV using 200.16 mg (0.84 mmol) (E)-m-methoxy- chalcone and 420.86 mg (0.88 mmol) of N-aminoacridinium 2.5j in 3.5 ml CH2Cl2 and 296.33 mg (0.92 mmol) of PIDA in 3.5 ml CH2Cl2. The desired product was isolated as a red solid (357.26 mg, 0.50 mmol, 60%).

Rf = 0.65 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) = δ 8.15 (dd, J = 8.9, 0.9 Hz, 1H, CH), 7.96 (dd, J = 9.0, 8.1 Hz, 1H, CH), 7.81 (dd, J = 8.9, 8.0 Hz, 1H, CH), 7.73 (d, J = 7.9 Hz, 2H, 2×CH), 7.67 (d, J = 8.9 Hz, 1H, CH), 7.64–7.53 (m, 4H, 4×CH), 7.44 (d, J = 4.8 Hz, 1H, CH), 7.42 (d, J = 4.5 Hz, 1H, CH), 7.40 (d, J = 3.9 Hz, 1H, CH), 7.23–7.12 (m, 2H, 2×CH), 7.02 – 6.98 (m, 1H, CH), 6.79–6.75 (m, 1H, CH), 6.73 (d, J = 3.1 Hz, 1H, CH), 6.71 (d, J = 3.1 Hz, 1H, CH), 5.30 (d, J

= 4.9 Hz, 1H, NCH), 4.56 (d, J = 4.9 Hz, 1H, NCH), 3.79 (s, 3H, OCH3), 3.65 (s, 3H, OCH3), 13 3.62 (s, 6H, 2OCH3), 3.52 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 188.2 (C), 160.9 (C), 159.9 (C), 156.4 (C), 155.4 (C), 140.1 (CH), 138.6 (C), 137.0 (C), 132.6 (C), 130.1 (CH), 130.0 (CH), 129.7 (CH), 129.4 (CH), 127.3 (CH), 121.1 (C), 120.5 (CH), 120.3 (CH), 112.7 (CH), 108.9 (CH), 107.6 (CH), 106.5 (CH), 106.2 (CH), 104.0 (CH), 103.1 (CH), 99.9 (CH),

60.0 (CH), 56.8 (CH), 56.7 (OCH3), 56.2 (OCH3), 55.7 (OCH3), 55.5 (OCH3), 55.4 (OCH3). 19 -1 F NMR (282 MHz, CD2Cl2) δ –152.41 (20%), –152.46 (80%). IR: (in CH2Cl2, cm ): ν = 3004, 2936, 2840, 1669, 1597, 1576, 1502, 1468, 1432, 1357, 1303, 1285, 1253, 1204, 1107,

1050, 1031, 981, 884, 811, 770, 700, 680, 609. HRMS (ESI) calculated for [C39, H35, N2, O6 (M+)]: 627.2490. Found: 627.2491.

162

Experimental Part

10-(2-(4-chlorobenzoyl)-3-phenylaziridin-1-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-

9,10-dihydroacridin-9-ylium tetrafluoroborate[4.41g][BF4]

Prepared according the general procedure IV, using 110.00 mg (0.45 mmol) (E)-p-Chloro- chalcone, 224.77 mg (0.47 mmol) N-aminoacridinium 2.5j in 1.5 ml CH2Cl2 and 157.83 mg

(0.49 mmol) of PIDA in 1.5 ml CH2Cl2. The desired product was isolated as a red solid (301.95 mg, 0.43 mmol, 95%).

Rf = 0.55 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.20 (d, J = 8.9 Hz, 1H, CH), 7.96 (dd, J = 9.0, 8.0 Hz, 1H, CH), 7.89 (d, J = 8.7 Hz, 2H, 2×CH), 7.84 (dd, J = 8.9, 8.1 Hz, 1H, CH), 7.74 (dd, J = 7.9 Hz, 2H, 2×CH), 7.67 (t, J = 9.0 Hz, 1H, CH), 7.64–7.56 (m, 3H, 3CH), 7.46 (d, J = 8.7 Hz, 2H, 2CH), 7.42 (t, J = 8.4 Hz, 1H, CH), 6.99 (d, J = 8.2 Hz, 1H, CH), 6.76 (d, J = 8.2 Hz, 1H, CH), 6.71 (d, J = 8.4 Hz, 2H, 2CH), 5.37 (d, J = 4.9 Hz, 1H, NCH), 4.55 (d, J = 4.9 Hz, 1H,

13 NCH), 3.64 (s, 3H, OCH3), 3.62 (s, 6H, 2×OCH3), 3.51 (s, 3H, O×CH3). C NMR (101

MHz, CD2Cl2) δ 187.5 (C), 160.9 (C), 160.7 (C), 156.4 (C), 155.5 (C), 155.4 (C), 141.0, 140.4 (CH), 139.1 (CH), 138.9 (CH), 138.6 (CH), 134.0 (CH), 132.6 (CH), 130.1 (CH), 130.0 (CH), 129.7 (CH), 129.4 (CH), 129.2 (CH), 127.4 (CH), 120.3 (C), 119.4 (C), 118.93 (CH), 108.9 (CH), 107.7 (CH), 106.5 (CH), 106.2 (CH), 104.0 (CH), 103.1 (CH), 60.2 (CH), 56.8 19 (CH), 56.7 (OCH3), 56.2 (OCH3), 55.7 (OCH3), 55.1 (OCH3). F NMR (282 MHz, CD2Cl2) -1 δ –156.14 (20%), –156.19 (80%). IR: (in CH2Cl2, cm ): ν = 2940, 2843, 1670, 1593, 1502, 1472, 1433, 1358, 1286, 1255, 1146, 1109, 1087, 1060, 978, 814, 775, 732, 699, 601. HRMS + (ESI) calculated for [C38, H32, Cl, N2, O5 (M )]: 631.1994. Found: 631.1998.

163

Experimental Part

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-(2-phenylaziridin-1-yl)-9,10-dihydroacridin-

9-ylium tetrafluoroborate[4.41h][BF4]

Prepared according the general procedure IV, using 30.20 mg (0.29 mmol) styrene and 143.47 mg (0.30 mmol) of N-aminoacridinium 2.5j, 27.80 mg (0.69 mmol, 2.4 equiv) MgO in 1 ml

CH2Cl2 and 103.07 mg (0.32 mmol) of PIDA in 1 ml CH2Cl2. The desired product was obtained as a red solid (150.90 mg, 0.26 mmol, 89%).

Rf = 0.7 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2 at 243 K) δ 8.28 (dd, J = 9.0, 7.9 Hz, 1H, CH), 8.20 (d, J = 8.9 Hz, 1H, CH), 7.97 (dd, J = 9.0, 8.0 Hz, 1H, CH), 7.65 (d, J = 8.9 Hz, 1H, CH), 7.61–7.53 (m, 5H, 5×CH), 7.45 (t, J = 8.4 Hz, 1H, CH), 7.07 (d, J = 7.9 Hz, 1H, CH), 6.99 (d, J = 8.0 Hz, 1H, CH), 6.73 (dd, J = 8.5 Hz, 2H, 2×CH), 3.84 (dd, J = 8.5, 6.0 Hz, 1H,. NCH), 3.68 (dd, J =

6.2, 3.2 Hz, 1H, NCH), 3.61 (s, 3H, OCH3), 3.60 (s, 3H, OCH3), 3.59 (s, 6H, OCH3), 3.25 13 (dd, J = 8.5, 3.1 Hz, 1H, NCH). C NMR (126 MHz, CD2Cl2) δ 161.2 (C), 161.1 (C), 156.0 (C), 155.7 (C), 155.6 (C), 140.1 (CH), 139.8 (C), 139.8 (C), 138.9 (CH), 134.3 (CH), 130.1 (CH), 129.9 (CH), 129.7 (CH), 127.3 (CH), 120.1 (C), 119.8 (C), 118.6 (CH), 109.4 (CH),

108.5 (CH), 106.7 (CH), 106.5 (CH), 103.7 (CH), 103.4 (CH), 57.4 (CH), 56.2 (OCH3), 56.2 19 (OCH3), 54.7 (OCH3), 53.9 (OCH3), 49.5 (CH). F NMR (282 MHz, CD2Cl2) δ –152.26 -1 (20%), –152.31 (80%). IR: (in CH2Cl2, cm ): ν = 3005, 2940, 2839, 1595, 1575, 1499, 1467, 1432, 1356, 1301, 1281, 1250, 1174, 1106, 1083, 1050, 1031, 977, 954, 886, 812, 767, 707, + 676, 591. HRMS (ESI) calculated for [C31, H29, N2, O4 (M )]: 494.2200 Found: 494.2188.

164

Experimental Part

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-(2-methyl-3-phenylaziridin-1-yl)-9,10- dihydroacridin-9-ylium tetrafluoroborate[4.41i][BF4]

Prepared according the general procedure IV, using 74.45 mg (0.63 mmol) (E)-methylstyrene, 315.64 mg (0.66 mmol) of acridinium 2.5j, 60.85 mg (1.51 mmol, 2.4 equiv) MgO in 2.5 ml

CH2Cl2 and 222.25 mg (0.69 mmol) PIDA in 2.5 ml CH2Cl2. The desired compound was isolated as a red solid (325.79 mg, 0.55 mmol, 87%).

Rf = 0.65 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.45 (d, J = 9.0 Hz, 1H, CH), 8.23–8.07 (m, 3H, 3×CH), 7.49–7.39 (m, 3H, 3×CH), 7.38–7.27 (m, 3H, 3×CH), 7.02–6.97 (m, 2H, 2×CH), 6.71 (dd, J = 8.5, 4.7 Hz, 2H, 2×CH), 5.41 (d, J = 4.0 Hz, 1H, NCH), 4.19 (tq, J = 6.3, 3.2 Hz, 1H, NCH), 13 3.57 (3s, 12H, 4×OCH3), 0.92 (d, J = 6.4 Hz, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 160.9 (C), 160.4 (C), 158.3 (C), 155.9 (C), 155.4 (C), 144.5 (C), 143.1 (C), 140.3, 139.9, 137.5 (C), 129.7 (CH), 129.2 (CH), 129.1 (CH), 128.6 (CH), 128.5 (CH), 128.5 (CH), 127.8 (CH), 120.0 (C), 119.9 (C), 119.0 (C), 109.9 (CH), 108.7 (CH), 106.7 (CH), 106.5 (CH),

106.4 (CH), 103.4 (CH), 103.4 (CH), 103.3 (CH), 64.9 (CH), 60.8 (CH), 56.9 (OCH3), 56.8 19 (OCH3), 55.8 (OCH3), 53.9 (OCH3), 12.0 (CH3). F NMR (282 MHz, CD2Cl2) δ –150.65 . -1 (20%), –150.71 (80%). IR: (in CH2Cl2, cm ): ν = 3007, 2940, 2839, 1595, 1575, 1500, 1468, 1432, 1356, 1301, 1281, 1250, 1150, 1106, 1083, 1050, 1031, 977, 955, 879, 813, 765, 748, + 707, 680, 592. HRMS (ESI) calculated for [C32, H31, N2, O4 (M )]: 507.2278 Found: 507.2281.

165

Experimental Part

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-(2-methyl-3-phenylaziridin-1-yl)-9,10- dihydroacridin-9-ylium tetrafluoroborate[4.41j][BF4]

Prepared according the general procedure IV, using 119.36 mg (1.01 mmol) β-(Z)- methylstyrene, 506.94 mg (1.06 mmol) acridinium 2.5j, 97.52 mg (2.42 mmol, 2.4 equiv)

MgO in 4.5 ml of CH2Cl2 and 357.85 mg (1.11 mmol) of PIDA in 4.5 ml CH2Cl2. The desired compound was isolated as a red solid (523.08 mg, 0.88 mmol, 87%).

Rf = 0.6 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2 at 273 K) δ 8.25 (t, J = 8.5 Hz, 1H, CH), 7.97 (d, J = 9.0 Hz, 1H, CH), 7.86 (t, J = 8.5 Hz, 1H, CH), 7.73 (d, J = 9.0 Hz, 1H, CH), 7.62–7.58 (m, 2H, 2×CH), 7.58–7.53 (m, 2H, 2×CH), 7.53–7.49 (m, 1H, CH), 7.42 (t, J = 8.4 Hz, 1H, CH), 7.05 (d, J = 8.1 Hz, 1H, CH), 6.93 (d, J = 8.0 Hz, 1H, CH), 6.70 (dd, J = 8.5, 3.4 Hz, 2H, 2×CH),

4.00 (d, J = 8.7 Hz, 1H, NCH), 3.59 (s, 3H, OCH3), 3.57 (s, 6H, 2×OCH3), 3.54 (s, 3H, 13 OCH3), 3.26 (dq, J = 8.7, 5.8 Hz, 1H, NCH), 1.60 (d, J = 5.8 Hz, 3H, CH3). C NMR (126

MHz, CD2Cl2) δ 161.4 (C), 161.3 (C), 156.2 (C), 155.8 (C), 155.3 (C), 139.9 (CH), 139.88 (CH), 139.6 (CH), 139.5 (CH), 132.0 (C), 130.1 (C), 129.5 (CH), 129.2 (CH), 127.8 (CH), 127.8 (CH), 120.2 (CH), 120.1 (C), 118.9 (C), 109.2 (CH), 108.8 (CH), 106.7 (CH), 106.6

(CH), 103.8 (CH), 103.5 (CH), 57.3 (CH), 56.2 (CH), 55.4 (OCH3), 54.4 (OCH3), 53.8 19 (OCH3), 53.6 (OCH3), 11.7 (CH3). F NMR (282 MHz, CD2Cl2) δ –152.36 (20%), –152.41 -1 (80%). IR: (in CH2Cl2, cm ): ν = 3007, 2940, 2839, 1595, 1575, 1500, 1468, 1432, 1356, 1301, 1281, 1250, 1150, 1106, 1083, 1050, 1031, 977, 955, 879, 813, 765, 748, 707, 680, 592. + HRMS (ESI) calculated for [C32, H31, N2, O4 (M )]: 507.2278 Found: 507.2281.

166

Experimental Part

10-(7-azabicyclo[4.1.0]heptan-7-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate[4.41k][BF4]

Prepared according the general procedure IV, using 97.2 mg (1.18 mmol) cyclohexene, 592.55 mg (1.24 mmol) acridinium 2.5j, 114.04 mg (2.83 mmol, 2.4 equiv) MgO in 4.5 ml

CH2Cl2 and 415.51 mg (1.29 mmol) PIDA in 4.5 ml CH2Cl2. The desired product was isolated as a red solid (579.82 mg, 1.04 mmol, 88%).

Rf = 0.85 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.18 (t, J = 9.0, 8.0 Hz, 2H, 2×CH), 7.92–7.81 (d, J = 8.0 Hz, 2H, 2×CH), 7.41 (t, J = 8.4 Hz, 1H, CH), 7.02 (d, J = 8.0 Hz, 2H, 2×CH), 6.70 (d, J = 8.4 Hz,

2H, 2×CH), 3.57 (s, 12H, OCH3), 3.07–2.86 (m, 2H, NCH), 2.60 (ddd, J = 15.2, 7.5, 5.2 Hz,

2H, CH2), 2.34 – 2.14 (m, 2H, CH2), 1.77–1.62 (m, 2H, CH2), 1.55 (dtt, J = 14.8, 11.3, 4.3 13 Hz, 2H, CH2). C NMR (101 MHz, CD2Cl2) δ 160.8 (C), 154.3 (C), 139.6 (C), 139.1 (CH),

129.6 (CH), 119.9 (C), 118.8 (C), 108.8 (CH), 106.3 (CH), 103.4 (CH), 56.9 (OCH3), 55.8

19 (OCH3), 51.8 (CH), 22.9 (CH2), 19.8 (CH2). F NMR (282 MHz, CD2Cl2) δ –152.71 (20%), -1 –152.76 (80%). IR: (in CH2Cl2, cm ): ν = 2941, 2841, 1595, 1574, 1500, 1466, 1432, 1355, 1299, 1281, 1248, 1148, 1103, 1084, 1050, 1031, 973, 955, 888, 813, 770, 731, 706, 679, 592. + HRMS (ESI) calculated for [C29, H33, N2, O4 (M )]: 471.2278 Found: 471.2274.

167

Experimental Part

10-(9-azabicyclo[6.1.0]nonan-9-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate[4.41l][BF4]

Prepared according the general procedure IV, using 126 mg (1.14 mmol) (Z)-cyclooctene, 572.46 mg (1.2 mmol) acridinium 2.5j and 402.62 mg (1.25 mmol) PIDA. The desired compound was isolated as a red solid (627.48 mg, 1.07mmol, 94%).

Rf = 0.75 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.17 (t, J = 9.0, 8.0 Hz, 2H, 2×CH), 7.94 (d, J = 8.9, 0.9 Hz, 2H, 2×CH), 7.41 (t, J = 8.4 Hz, 1H, CH), 7.01 (d, J = 8.1, 0.9 Hz, 2H, 2×CH), 6.70 (d, J = 8.4

Hz, 2H, 2×CH), 3.57 (s, 12H, 4×OCH3), 2.90 (dt, J = 13.8, 3.3 Hz, 2H, NCH), 2.81 – 2.71 (m, 13 2H, CH), 2.08–1.67 (m, 5H, CH2), 1.80 – 0.86 (m, 7H, CH2). C NMR (101 MHz, CD2Cl2) δ 160.8 (C), 154.2 (C), 139.6 (CH), 139.0 (CH), 129.6 (CH), 119.9 (C), 118.7 (C), 108.5

(CH), 106.2 (CH), 103.4 (CH), 56.9 (OCH3), 55.8 (OCH3), 55.5 (OCH3), 26.1 (CH2), 24.8 19 - (CH2). F NMR (282 MHz, CD2Cl2) δ –151.85 (20%), –151.91 (80%). IR: (in CH2Cl2, cm 1): ν = 2929, 2851, 1596, 1575, 1500, 1467, 1432, 1356, 1300, 1282, 1248, 1148, 1100, 1082, 1040, 1031, 977, 954, 908, 875, 813, 770, 733, 705, 676, 577. HRMS (ESI) calculated for + [C31, H35, N2, O4 (M )]: 499.2591 Found: 499.2582.

168

Experimental Part

10-2-butyl-3-methylaziridin-1-yl)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate[4.41m][BF4]

Prepared according the general procedure IV, using 85.86 mg (0.62 mmol) (Z)-hept-2-ene, 310.86 mg (0.65 mmol) acridinium 2.5j, 59.64 mg (1.48 mmol, 2.4 equiv) MgO in 2.5 ml

CH2Cl2 and 219.03 mg (0.68 mmol) PIDA in 2.5 ml CH2Cl2. The desired compound was isolated as a red solid (284.91 mg, 0.45 mmol, 80%).

Rf = 0.85 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, 400 MHz, CD2Cl2) δ 8.21 (dd, J = 9.0, 8.0 Hz, 2H, 2×CH), 7.98–7.88 (m, 2H, 2×CH), 7.45 (t, J = 8.4 Hz, 1H, CH), 7.07–7.02 (m, 2H, 2×CH), 6.74 (d, J = 8.4 Hz,

2H, 2×CH), 3.61 (s, 12H, OCH3), 2.91 (dq, J = 8.7, 5.8 Hz, 1H, NCH), 2.80 (ddd, J = 10.0, 8.7, 3.5 Hz, 1H, NCH), 2.61 (dddd, J = 13.2, 9.3, 5.9, 3.5 Hz, 1H), 1.83 (d, J = 5.9 Hz, 3H), 13 1.60 – 1.43 (m, 5H), 1.15–0.90 (m, 3H). C NMR (101 MHz, CD2Cl2) δ= 160.8 (C), 155.7 (C), 154.4 (C), 139.5 (CH), 139.0 (CH), 129.6 (CH), 119.9 (C), 118.7 (C), 108.6 (CH), 106.34

(CH), 106.2 (C), 103.4 (CH), 56.9 (OCH3), 55.8 (OCH3), 55.6 (OCH3), 28.5 (CH2), 26.1 19 (CH2), 22.5 (CH2), 13.6 (CH3), 11.6 (CH3). F NMR (282 MHz, CD2Cl2) δ –152.51 (20%), -1 –152.56 (80%). IR: (in CH2Cl2, cm ): ν = 2939, 2872, 1595, 1575, 1500, 1467, 1432, 1356, 1300, 1279, 1250, 1150, 1105, 1084, 1040, 1031, 976, 954, 905, 885, 812, 750, 705, 676, 578. + HRMS (ESI) calculated for [C30, H35, N2, O4 (M )]: 487.2591 Found: 487.2589.

169

Experimental Part

2-1-(9-(2,6-dimethoxyphenyl)-1,8-dimethoxyacridin-9-ylium-10(9H)-yl)-3-ethylaziridin-

2-yl)ethan-1-ide, tetrafluoroborate salt[4.41n][BF4]

Prepared according the general procedure IV, using 100.07 mg (1.19 mmol) (E)-trans-hex-3- ene, 597.81 mg (1.25 mmol) acridinium tetrafluoroborate salts and 114.85 mg (2.85 mmol,

2.4 equiv) MgO in 5 ml CH2Cl2 and 418.73 mg (1.30 mmol) PIDA in 5 ml CH2Cl2. The desired product was isolated as a red solid (566.00 mg, 1.01 mmol, 86%).

Rf = 0.61 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.39 (dd, J = 8.9, 1.0 Hz, 1H, CH), 8.24 (ddd, J = 12.8, 9.0, 8.0 Hz, 2H, 2×CH), 7.94 – 7.76 (m, 1H, CH), 7.53 (t, J = 8.4 Hz, 1H, CH), 7.20–7.04 (m, 2H, 2×CH), 6.84 (dd, J = 8.4, 0.7 Hz, 1H, CH), 6.78 (dd, J = 8.4, 0.7 Hz, 1H, CH), 3.76 (s, 3H,

OCH3), 3.71 (s, 3H, OCH3), 3.69 (s, 3H, OCH3), 3.58 (s, 3H, OCH3), 3.29 (ddd, J = 10.3, 5.4, 3.8 Hz, 1H, NCH), 2.88 (ddd, J = 8.9, 5.4, 3.6 Hz, 1H, NCH), 2.77 (dtd, J = 14.8, 7.4, 3.6 Hz, 1H), 1.90 (ddt, J = 13.9, 8.8, 7.6 Hz, 1H, CH), 1.62 – 1.45 (m, 1H, CH), 1.29 (t, J = 7.5 Hz, 13 3H, CH3), 0.92 (t, J = 7.4 Hz, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 160.8 (C), 160.0 (C), 156.5 (C), 155.1 (C), 153.8 (C), 140.1 (C), 139.2 (CH), 138.6 (CH), 138.5 (CH), 129.6 (CH), 120.4 (C), 119.7 (C), 118.6 (C), 109.1 (CH), 108.3 (CH), 106.5 (CH), 106.1 (CH),

103.6 (CH), 103.0 (CH), 56.8 (OCH3), 56.7 (OCH3), 56.6 (OCH3), 56.4, (OCH3) 55.8 (CH), -1 55.8 (CH), 53.8 (CH), 23.8 (CH2), 22.2 (CH2), 10.7 (CH3), 9.6 (CH3). IR: (in CH2Cl2, cm ): ν = 2968, 2938, 2840, 1694, 1598, 1575, 1499, 1467, 1432, 1356, 1300, 1277, 1253, 1171, 1148, 1082, 1040, 1031, 975, 955, 908, 889, 815, 749, 705, 678, 588. HRMS (ESI) + calculated for [C29, H33, N2, O4 (M )]: 473.2435 Found: 473.2435.

170

Experimental Part

10-((2-acetoxy-2-(4-methoxyphenyl)ethyl)amino)-9-(2,6-dimethoxyphenyl)-1,8- dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate salt[4.49a][BF4]

Prepared according the general procedure IV, using 100.64 mg (0.75 mmol) p-Methoxy- styrene, 373.03 mg (0.78 mmol) acridinium 2.5j in 2.5 ml CH2Cl2 and 264.12 mg (0.82 mmol) of PIDA in 2.5 ml CH2Cl2. The desired compound was isolated as a red solid (391.05 mg, 0.67 mmol, 90%)

1 H NMR (400 MHz, CD2Cl2) δ 8.28 (dd, J = 9.2, 0.9 Hz, 1H, CH), 8.20–8.09 (m, 3H, 3CH), 7.42 (t, J = 8.4 Hz, 1H, CH), 7.33 (d, J = 8.7 Hz, 1H, CH), 7.10–7.03 (m, 1H, CH), 7.01–6.95 (m, 2H, 2CH), 6.93–6.84 (m, 2H, 2CH), 6.70 (dd, J = 8.4, 1.1 Hz, 2H, 2CH), 6.10 (dd, J =

8.7, 3.6 Hz, 1H, CH), 3.78 (s, 3H, OCH3), 3.57 (s, 3H, OCH3) 3.56 (s, 6H), 3.55 (s, 3H, 13 OCH3) 1.93 (s, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 169.8 (C), 160.9 (C), 160.7 (C), 159.9 (C), 157.6 (C), 155.7 (C), 155.6 (C), 142.9 (C), 142.4 (C), 140.3 (CH), 140.1 (CH), 129.6 (CH), 129.6 (CH), 127.8 (CH), 120.0 (C), 119.9 (C), 118.9 (C), 114.0 (CH), 108.7

(CH), 108.6 (CH), 106.5 (CH), 106.4 (CH), 103.4 (CH), 103.3 (CH), 74.0 (OCH3), 56.8 19 (OCH3), 55.7 (OCH3), 55.7 (OCH3), 55.0 (OCH3), 20.6 (CH3). F NMR (282 MHz, CD2Cl2) -1 δ –151.65 (20%), –151.71 (80%) IR: (in CH2Cl2, cm ): ν = 3325, 2942, 2210, 1742, 1611, 1580, 1514, 1472, 1433, 1364, 1250, 1177, 1110, 1082, 1058, 818, 626, 579. HRMS (ESI) + calculated for [C34, H35, N2, O7 (M )]: 583.2439 Found: 583.2425.

171

Experimental Part

General Procedure V For Imidation of Sulfoxides [4.66][BF4].

To a solution of sulfoxide (0.84 mmol) and N-aminoacridinium [2.5j][BF4] (422 mg, 0.882 mmol, 1.05 equiv) in 3 ml CH2Cl2, was added dropwise a solution of PIDA (303 mg, 0.924 mmol, 1.2 equiv) in 3 ml CH2Cl2. The reaction mixture was allowed to stir at 23 °C for 2-4 hours. Upon completion (monitored by ESI-MS analysis of crude sample) 10 ml of water was added, and the product extracted with CH2Cl2 (3×20ml). The combined organic phases are dried over Na2SO4, and concentrated. The product was purified by column chromatography using basic alumina. 100% AcOEt, then a mixture of CH2Cl2/MeOH were used as eluents.

The product was dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound.

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((methyl(oxo)(phenyl)-l6- sulfanylidene)amino)-9,10-dihydroacridin-9-ylium tetrafluoroborate salt [4.66a][BF4]

Prepared according the general procedure V, using 63.09 mg (0.45 mmol) phenylmethylsulfoxide, 224.77 mg (0.47 mmol) N-aminoacridinium 2.5j in 1.2 ml CH2Cl2 and 173.93 mg (0.54 mmol) PIDA in 1.2 ml CH2Cl2. The desired product was isolated as a red solid (252.73 mg, 0.41 mmol, 91%)

Rf = 0.72 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2 at 243 K) δ 8.33 (d, J = 9.0 Hz, 1H, CH), 8.15 (d, J = 9.0 Hz, 1H, CH), 8.07 (t, J = 8.5 Hz, 1H, CH), 8.03–7.93 (m, 2H, 2×CH), 7.83 (t, J = 8.4 Hz, 1H, CH), 7.74–7.62 (m, 1H, CH), 7.56 (t, J = 7.9 Hz, 2H, 2×CH), 7.40 (t, J = 8.4 Hz, 1H, CH), 6.94 (d, J = 8.0 Hz, 1H, CH), 6.78 (d, J = 7.9 Hz, 1H, CH), 6.73–6.62 (m, 2H, 2×CH), 3.59 (s, 13 3H, OCH3), 3.54 (s, 3H, OCH3), 3.51 (s, 3H, OCH3), 3.47 (s, 3H, OCH3). C NMR (126

MHz, CD2Cl2 at 243 K) δ 160.0 (C), 159.4 (C), 155.8 (C), 155.3 (C), 154.4 (C), 143.50 (CH), 143.2 (CH), 138.9 (CH), 138.3 (CH), 135.1 (CH), 134.2 (CH), 129.9 (CH), 129.5 (CH), 127.4 (C), 119.7 (CH), 119.7 (CH), 118.6 (CH), 111.1 (CH), 110.4 (CH), 106.2 (CH), 106.05 (CH), 19 103.1 (CH), 102.9 (CH), 56.9 (OCH3), 56.8 (OCH3), 55.8 (OCH3), 40.5 (CH3). F NMR

172

Experimental Part

-1 (282 MHz, CD2Cl2) δ –151.61 (20%), –151.67 (80%). IR: (in CH2Cl2, cm ): ν = 2936, 2841, 1596, 1575, 1468, 1433, 1356, 1277, 1253, 1223, 1158, 1035, 976, 898, 815, 771, 732, 703. + HRMS (ESI) calculated for [C30, H29, N2, O5, S (M )]: 529.1792 Found: 529.1792

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((methyl(oxo)(p-tolyl)-l6- sulfanylidene)amino)-9,10-dihydroacridin-9-ylium tetrafluoroborate [4.66b][BF4]

Prepared according the general procedure V, using 69.40 mg (0.45 mmol) p- tolylmethylsulfoxide, 224.77 mg (0.47 mmol) N-aminoacridinium 2.5j in 1.2 ml CH2Cl2 and

173.93 mg (0.54 mmol) PIDA in 1.2 ml CH2Cl2. The desired product was isolated as a red solid (239.57 mg, 0.38 mmol, 85%)

Rf = 0.71 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.35 (d, J = 8.6 Hz, 2H, 2×CH), 8.03 (s, 2H, 2×CH), 7.90 (d, J = 8.5 Hz, 2H, 2×CH), 7.49–7.30 (m, 3H, 3×CH), 6.92 (d, J = 8.0 Hz, 2H, 2×CH), 6.70 (d, J 13 = 8.4 Hz, 2H, 2×CH), 3.57 (s, 6H, 2×OCH3), 3.54 (s, 6H, 2×OCH3), 2.42 (s, 3H). C NMR

(101 MHz, CD2Cl2) δ 159.8 (C), 155.8 (C), 154.5 (C), 146.5 (C), 143.6 (CH), 138.5 (CH), 131.3 (C), 130.4 (CH), 129.4 (CH), 127.4 (CH), 120.0 (C), 119.1 (C), 111.0 (CH), 106.3 19 (CH), 103.3 (CH), 56.7 (OCH3), 55.8 (OCH3), 53.8 (OCH3), 41.1 (OCH3), 21.4 (CH3). F -1 NMR (282 MHz, CD2Cl2) δ –151.61 (20%), –151.67 (80%). IR: (in CH2Cl2, cm ): ν = 2937, 2839, 1595, 1575, 1469, 1433, 1357, 1277, 1254, 1222, 1155, 1041, 977, 898, 813, 771, 733, + 702. HRMS (ESI) calculated for [C31, H31, N2, O5, S (M )]: 543.1948 Found: 543.1948.

173

Experimental Part

10-(((4-chlorophenyl)(methyl)(oxo)-l6-sulfanylidene)amino)-9-(2,6-dimethoxyphenyl)-

1,8-dimethoxy-9,10-dihydroacridin-9-ylium tetrafluoroborate [4.66c][BF4]

Prepared according the general procedure V, using 79 mg (0.45 mmol) p-Cl- phenylmethylsulfoxide, 224.77 mg (0.47 mmol) N-aminoacridinium 2.5j in 1.5 ml CH2Cl2 and 173.93 mg (0.54 mmol) PIDA in 1.5 ml CH2Cl2. The desired product was isolated as a red solid (279.87 mg, 0.43 mmol, 97%)

Rf = 0.62 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2 at 243 K) δ 8.37 (d, J = 9.0 Hz, 1H, CH), 8.21 (d, J = 9.0 Hz, 1H, CH), 8.13 (t, J = 8.5 Hz, 1H, CH), 8.00 (d, J = 8.7 Hz, 2H, 2×CH), 7.91 (t, J = 8.5 Hz, 1H, CH), 7.55 (d, J = 8.7 Hz, 2H, 2×CH), 7.38 (t, J = 8.4 Hz, 1H, CH), 6.94 (d, J = 8.0 Hz,

1H, CH), 6.81 (d, J = 8.0 Hz, 1H, CH), 6.72–6.59 (m, 2H, 2×CH), 3.55 (s, 3H, OCH3), 3.53 13 (s, 6H, 2×OCH3), 3.48 (s, 3H, OCH3). C NMR (126 MHz, CD2Cl2 at 243 K) δ 160.0 (C) (C), 159.5 (C), 155.7 (C), 155.2 (C), 154.7 (C), 143.4 (CH), 143.2 (CH), 141.6 (CH), 139.12 (CH), 138.5 (CH), 132.7 (CH), 130.1 (C), 129.5 (CH), 129.3 (CH), 119.7 (C), 119.7 (C), 118.5 (CH), 111.1 (CH), 110.4 (CH), 106.2 (CH), 106.0 (CH), 103.1 (CH), 102.9 (CH), 56.9 19 (OCH3), 56.8 (OCH3), 55.8 (OCH3), 40.8 (CH3). F NMR (282 MHz, CD2Cl2) δ –151.57 -1 (20%), –151.62 (80%). IR: (in CH2Cl2, cm ): ν = 2968, 1577, 1472, 1433, 1359, 1264, 1111,

1085, 1049, 980, 891, 815, 730, 702. HRMS (ESI) calculated for [C30, H28, Cl, N2, O5, S (M+)]: 563.1402 Found: 563.1396.

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((oxodiphenyl-l6-sulfanylidene)amino)-9,10- dihydroacridin-9-ylium tetrafluoroborate [4.66d][BF4]

Prepared according the general procedure V, using 75 mg (0.37 mmol) diphenylsulfoxide,

185.80 mg (0.39 mmol) N-aminoacridinium 2.5j in 1.2 ml CH2Cl2 and 122.39 mg (0.38

174

Experimental Part

mmol) PIDA in 1.2 ml CH2Cl2. The desired product was isolated as a red solid (176.41 mg, 0.26 mmol, 70%)

Rf = 0.61 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.25 (dd, J = 9.1, 1.0 Hz, 2H, 2×CH), 7.94–7.77 (m, 6H, 6CH), 7.73–7.65 (m, 2H, 2×CH), 7.56 (dd, J = 8.4, 7.4 Hz, 4H, 4×CH), 7.41 (t, J = 8.4 Hz, 1H, CH), 6.85 (d, J = 8.1 Hz, 2H, 2×CH), 6.70 (d, J = 8.4 Hz, 2H, 2×CH), 3.59 (s, 6H, 13 2×OCH3), 3.52 (s, 6H, 2×OCH3). C NMR (101 MHz, CD2Cl2) δ 159.7 (C), 155.7 (C), 154.7 (C), 143.5 (C), 138.0 (CH), 135.0 (CH), 134.5 (CH), 129.9 (CH), 129.8 (CH), 129.53 (CH), 128.1 (CH), 128.0 (CH), 120.0 (C), 119.0 (C), 110.9 (CH), 106.2 (CH), 103.4 (CH), 19 56.7 (OCH3), 55.9 (OCH3). F NMR (282 MHz, CD2Cl2) δ –152.45 (20%), –152.50 (80%). -1 IR: (in CH2Cl2, cm ): ν = 2941, 2839, 1597, 1575, 1469, 1433, 1357, 1278, 1254, 1155, + 1046, 973, 899, 842, 737, 684. HRMS (ESI) calculated for [C35, H31, N2, O5, S (M )]: 591.1948 Found: 591.1933.

General Procedure VI For imidation of Thioethers [4.66][BF4].

To a solution of thioether (0.40 mmol), N-aminoacridinium [2.5j][BF4] (0.42 mmol, 1.05 equiv) and MgO (0.96 mmol) in 3 ml CH2Cl2, was added dropwise a solution of PIDA (0.48 mmol, 1.1 equiv) in 3 ml of CH2Cl2. The reaction mixture was allowed to stir at 23 °C for 16 hours. Upon completion (monitored by ESI-MS analysis of crude sample) 10 ml of water was added, and the product extracted with CH2Cl2 (3×20ml). The combined organic phases are dried over Na2SO4, and concentrated. The product was purified by column chromatography using basic alumina. 100% AcOEt, then a mixture of CH2Cl2/MeOH were used as eluents.

The product was dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound.

175

Experimental Part

9-(2,6-dimethoxyphenyl)-10-((diphenyl-l4-sulfanylidene)amino)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate salt [4.67a][BF4]

Prepared according the general procedure VI, using 74.51 mg (0.40 mmol) of diphenylsulfide,

200.86 mg (0.42 mmol) N-aminoacridinium 2.5j, 38.68 mg (0.96 mmol) MgO in CH2Cl2 (2.5 ml) and 154.61 mg (0.48 mmol) PIDA in (2.5 ml). The desired product was isolated as a red solid (218.63 mg, 0.33 mmol, 84%)

Rf = 0.625 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2 ) δ 7.96–7.91 (m, 4H, 4×CH), 7.88 (d, J = 9.1 Hz, 2H, 2×CH), 7.79–7.64 (m, 7H, 7×CH), 7.42 (t, J = 8.4 Hz, 1H, CH), 6.90 (d, J = 7.9 Hz, 2H, 2×CH), 6.72 13 (d, J = 8.4 Hz, 2H, 2×CH), 3.62–3.56 (s, 6H, 2×OCH3), 3.54 (s, 6H, 2×OCH3). C NMR

(126 MHz, CD2Cl2) δ 160.8 (C), 156.3 (C), 153.1 (C), 145.5 (C), 138.6 (CH), 137.3 (CH), 133.4 (CH), 131.0 (CH), 131.0 (CH), 129.7 (CH), 127.9 (CH), 120.7 (C), 119.8 (C), 111.1 19 (CH), 106.5 (CH), 103.8 (CH), 57.1 (OCH3), 56.2 (OCH3). F NMR (282 MHz, CD2Cl2) δ – -1 152.49 (20%), –152.50 (80%). IR: (in CH2Cl2, cm ): ν = 2941, 2840, 1596, 1574, 1497, 1469, 1433, 1355, 1295, 1277, 1253, 1174, 1141, 1107, 1031, 972, 956, 877, 817, 767, 748, 693, 584.

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((methyl(phenyl)-l4-sulfanylidene)amino)-

9,10-dihydroacridin-9-ylium tetrafluoroborate salt [4.67b][BF4]

Prepared according the general procedure VI, using 59.62 mg (0.48 mmol) thioanisole, 239.12 mg (0.50 mmol) N-aminoacridinium 2.5j, 46.34 mg (1.15 mmol) MgO in CH2Cl2 (2.5 ml) and 183.59 mg (0.57 mmol) PIDA in (2.5 ml). The desired product was isolated as a red solid (252.18 mg, 0.42 mmol, 88%)

Rf = 0.55 (Neutral alumina, CH2Cl2- MeOH, 98:2)

176

Experimental Part

1 H NMR (400 MHz, CD2Cl2) δ 8.08–7.95 (m, 2H, 2×CH), 7.89–7.79 (m, 1H, CH), 7.76– 7.66 (m, 1H), 7.71–7.63 (m, 1H), 7.62 – 7.52 (m, 2H, 2×CH), 7.41 (t, J = 8.4 Hz, 1H, CH),

6.88 (d, J = 7.9 Hz, 2H, 2×CH), 6.71 (d, J = 8.4 Hz, 2H, 2×CH), 3.59 (s, 6H, 2×OCH3), 3.53 13 (s, 6H, 2×OCH3), 3.25 (s, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 160.2 (C), 155.9 (C), 152.4 (C), 145.0 (C), 137.9, 136.7 (C), 133.5 (CH), 130.4 (CH), 129.8 (CH), 129.3 (CH), 127.3 (CH), 127.1 (CH), 120.2 (C), 119.3 (C), 110.7 (CH), 106.1 (CH), 103.4 (CH), 56.7 19 (OCH3), 55.8 (OCH3), 53.8 (OCH3), 53.7 (OCH3), 35.2 (CH3). F NMR (282 MHz, CD2Cl2) δ –152.10 (20%), –152.15 (80%).

10-((dibutyl-l4-sulfanylidene)amino)-9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-9,10- dihydroacridin-9-ylium tetrafluoroborate salt [4.67c][BF4]

Prepared according the general procedure VI, using 30 mg (0.20 mmol) dibutylsulfide, 100.43 mg (0.21 mmol) N-aminoacridinium 2.5j, 19.34 mg (0.48 mmol) MgO in CH2Cl2 (1 ml) and 77.30 mg (0.24 mmol) PIDA in (1 ml). The desired product was isolated as a red solid (112.05 mg, 0.18 mmol, 90%)

Rf = 0.65 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.33 (dd, J = 9.1, 1.0 Hz, 2H, 2×CH), 8.06 (dd, J = 9.1, 7.9 Hz, 2H, 2×CH), 7.40 (t, J = 8.4 Hz, 1H, CH), 6.95 (d, J = 8.0 Hz, 2H, 2CH), 6.70 (d, J = 8.4

Hz, 2H, 2×CH), 3.57 (s, 6H, 2×OCH3), 3.55 (s, 6H, 2O×CH3), 3.28 (t, J = 7.9 Hz, 3H, 2CH2,

CH), 1.95 (ddd, J = 13.0, 8.0, 6.5 Hz, 2H, CH2), 1.88 – 1.71 (m, 3H, CH2, CH), 1.52 (h, J = 13 7.4 Hz, 4H, 2CH2), 0.99 (t, J = 7.4 Hz, 6H, 2CH3). C NMR (101 MHz, CD2Cl2) δ 160.4 (C), 155.9 (C), 151.7 (C), 145.3 (C), 137.9 (CH), 129.2 (CH), 120.3 (C), 119.4 (C), 110.3

(CH), 106.4 (CH), 106.1 (CH), 106.1 (CH), 103.4 (CH), 56.7 (OCH3), 55.8 (OCH3), 47.0 19 (CH2), 25.2 (CH2), 22.0 (CH2), 13.3 (CH3). F NMR (282 MHz, CD2Cl2) δ –152.34 (20%), –152.39 (80%).

177

Experimental Part

9-(2,6-dimethoxyphenyl)-1,8-dimethoxy-10-((tetrahydro-1l4-thiophen-1-ylidene)amino)-

9,10-dihydroacridin-9-ylium tetrafluoroborate salt [4.67d][BF4]

Prepared according the general procedure VI, using 19.39 mg (0.22 mmol) diphenylsulfide,

109.99 mg (0.23 mmol) N-aminoacridinium 2.5j, 21.36 mg (0.53 mmol) MgO in CH2Cl2 (1.1 ml) and 83.75 mg (0.26 mmol) PIDA in (1.1 ml). The desired product was isolated as a red solid (122.92 mg, 0.21 mmol, 99%)

Rf = 0.62 (Neutral alumina, CH2Cl2- MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.22 (dd, J = 9.1, 1.1 Hz, 2H, 2×CH), 8.08 (dd, J = 9.1, 7.9 Hz, 2H, 2×CH), 7.40 (t, J = 8.4 Hz, 1H, CH), 6.97–6.93 (m, 2H, 2×CH), 6.70 (d, J = 8.4 Hz,

2H, 2×CH), 3.53–3.37 (m, 2H, CH2), 2.52 (dddd, J = 12.7, 9.9, 6.0, 4.0 Hz, 2H, CH2), 2.26 – 13 1.97 (m, 2H, CH2). C NMR (101 MHz, CD2Cl2) δ 160.4 (C), 155.9 (C), 151.9 (C), 145.1 (C), 138.2 (CH), 129.2 (CH), 120.3 (C), 119.4 (C), 110.5 (CH), 106.1 (CH), 103.3 (CH), 56.7 19 (OCH3), 55.8 (OCH3), 50.6 (CH2), 26.2 (CH2). F NMR (282 MHz, CD2Cl2) δ –152.30 + (20%), –152.35 (80%). HRMS (ESI) calculated for [C27, H29, N2, O4, S (M )]: 477.1843 Found: 477.1846.

178

Experimental Part

General Procedure VII For Aziridines [4.41a-g][BF4] and Sulfoximines [4.66][BF4] Photoreductive Deprotection.

In a flame dried flask the aziridine or sulfoximine (0.44 mmol) is dissolved in 1.5 ml dried

CH2Cl2. The solution is degassed for 10 min with nitrogen then, TMEDA (0.97 mmol) is added. The reaction mixture is allowed to stir at 23 °C, under nitrogen and green LED 530 nm of 1 Watt, for 4-16 hours. Upon completion (monitored by ESI-MS analysis of crude sample) 10 ml of water was added. The pH was adjusted at 9 with the addition of a saturated aqueous solution of K2CO3 and the product extracted with CH2Cl2 (3×20ml). The combined organic phases are dried over Na2SO4, and concentrated. The product was purified by column chromatography using silica gel and AcOEt/Hexane + 0.1% Et3N, 9/1 (v/v) as eluent.

General Procedure VIII For Aziridines [4.41h-n][BF4] and Sulfimines [4.67][BF4] Photoreductive Deprotection .

In a flame dried flask aziridine or sulfimide derivative (0.34 mmol) is dissolved in 2 ml dried

CH2Cl2. The solution is degassed for 10 min with nitrogen, then B(C6F5)3 (0.07 mmol) and TMEDA (0.75 mmol) were added. The reaction mixture is allowed to stir at 23 °C, under nitrogen and blue LED 405 nm of 1 Watt, for 16 hours. Upon completion (monitored by ESI- MS analysis of crude sample) 1.02 mmol of benzyl chlorofomarte was added and the reaction was allowed to for 3 hours. Upon completion (monitored by ESI-MS analysis of crude sample) 10 ml of water was added, and the product extracted with CH2Cl2 (3×20ml). The combined organic phases are dried over Na2SO4, and concentrated. The product was purified by column chromatography using silica gel and AcOEt/Hexane, 9/1 (v/v) as eluent. phenyl-3-phenylaziridin-2-yl)methanone 4.72a 268

Prepared according the general procedure VII, using 300.73 mg (0.44 mmol) 4.41a and

112.72 mg (0.97 mmol) TMEDA in 2 ml CH2Cl2. The desired product was isolated as pale yellow oil (84.83 mg, 0.38 mmol, 88%)

268 Y. Shen, M. Zhao, J. Xu, Y. Shi, Angew. Chem. Int. Ed. 2006, 45, 8005.

179

Experimental Part

1 H NMR (400 MHz, CDCl3) δ 8.00 (dd, J = 8.4, 1.3 Hz, 2H, 2×CH), 7.65–7.57 (m, 1H, CH), 7.49 (dd, J = 8.4, 7.2 Hz, 2H, 2×CH), 7.43–7.28 (m, 5H, 5×CH), 3.52 (d, J = 2.3 Hz, 1H, 13 NCH), 3.18 (d, J = 2.4 Hz, 1H, NCH), 2.69 (s, 1H, NH). C NMR (101 MHz, CDCl3) δ 195.7 (CH), 138.3 (CH), 135.9 (CH), 133.8 (CH), 128.8 (CH), 128.5 (CH), 128.3 (CH), 127.9 (CH), 126.2 (CH), 44.1 (NCH), 43.5 (NCH). phenyl-3-(m-tolyl)aziridin-2-yl)methanone 4.72b

Prepared according the general procedure VII, using 398.32 mg (0.57 mmol) 4.41b and

145.26 mg (1.25 mmol) TMEDA in 2.5 ml CH2Cl2. The desired product was isolated as pale yellow oil (109.15 mg, 0.46 mmol, 82%)

1 H NMR (400 MHz, CDCl3) δ 8.06–7.97 (m, 2H, 2×CH), 7.68–7.60 (m, 1H, CH), 7.57–7.46 (m, 2H, 2×CH), 7.31–7.24 (m, 1H, CH), 7.23–7.12 (m, 3H, 3×CH), 3.54 (d, J = 2.4 Hz, 1H, NCH), 3.18 (d, J = 2.4 Hz, 1H, NCH), 2.75–2.57 (m, 1H), 2.39 (s, 3H). 13C NMR (101 MHz,

CDCl3) δ 195.7 (CH), 138.3 (CH), 138.2 (CH), 135.9 (CH), 133.8 (CH), 128.8 (CH), 128.7 (CH), 128.4 (CH), 128.3 (CH), 126.6 (CH), 123.4 (CH), 44.1 (NCH), 43.6 (NCH), 21.3

(CH3).

3-(3-chlorophenyl)aziridin-2-yl)(phenyl)methanone4.72c

Prepared according the general procedure VII, using 201.30 mg (0.28 mmol) 4.41b and 70.88 mg (0.61 mmol) TMEDA in 1.2 ml CH2Cl2. The desired product was isolated as pale yellow oil (61.85 mg, 0.24 mmol, 88%)

1 H NMR (400 MHz, CD2Cl2) δ 7.99 (dd, J = 8.4, 1.3 Hz, 2H, 2CH), 7.67–7.58 (m, 1H, CH), 7.55–7.46 (m, 2H, 2CH), 7.38 (dt, J = 2.4, 1.0 Hz, 1H, CH), 7.33–7.24 (m, 3H, 3CH), 3.48 (dd, J = 7.5, 2.4 Hz, 1H, NCH), 3.14 (dd, J = 8.8, 2.3 Hz, 1H, NCH), 2.64 (s, 1H, NH). 13C

NMR (101 MHz, CD2Cl2) δ 194.5 (CH), 140.4 (CH), 138.1 (CH), 134.2 (CH), 129.7 (CH), 129.2 (CH), 128.6 (CH), 128.0 (CH), 126.1 (CH), 44.0 (NCH), 43.7 (NCH)

180

Experimental Part

(3-methoxyphenyl)-3-phenylaziridin-2-yl)methanone 4.72d

Prepared according the general procedure VII, using 335.82 mg (0.47 mmol) 4.41d and

119.69 mg (159 µl, 1.03 mmol) TMEDA in 2.2 ml CH2Cl2. The desired product was isolated as pale yellow oil (91.18 mg, 0.36 mmol, 77%)

1 H NMR (400 MHz, CDCl3) δ 7.60–7.48 (m, 2H, 2×CH), 7.43–7.28 (m, 6H, 6×CH), 7.16

(ddd, J = 8.3, 2.7, 1.0 Hz, 1H, CH), 3.86 (d, J = 1.3 Hz, 3H, OCH3), 3.50 (d, J = 2.3 Hz, 1H, 13 NCH), 3.18 (d, J = 2.4 Hz, 1H, NCH). C NMR (101 MHz, CDCl3) δ 195.6 (CH), 159.9 (CH), 138.2 (CH), 137.2 (CH), 129.8 (CH), 128.5 (CH), 127.9 (CH), 126.2 (CH), 121.0 (CH),

120.3 (CH), 112.4 (CH), 55.5 (OCH3), 44.1 (NCH), 43.6 (NCH).

(4-chlorophenyl)-3-phenylaziridin-2-yl)methanone 4.72e268

Prepared according the general procedure VII, using 230.06 mg (0.32 mmol) 4.41e and 81.35 mg (106 µl, 0.70 mmol) TMEDA in 1.3 ml CH2Cl2. The desired product was isolated as pale yellow oil (74.2 mg, 0.29 mmol, 90%)

1 H NMR (400 MHz, CDCl3) δ 8.01–7.88 (m, 2H, 2×CH), 7.50–7.41 (m, 2H, 2×CH), 7.39– 7.28 (m, 5H, 5×CH), 3.45 (d, J = 2.4 Hz, 1H, NCH), 3.19 (d, J = 2.4 Hz, 1H, NCH), 2.78 – 13 2.55 (m, 1H, NH). C NMR (101 MHz, CDCl3) δ 194.5 (CH), 140.4 (CH), 138.1 (CH), 134.2 (CH), 129.7 (CH), 129.2 (CH), 128.6 (CH), 128.0 (CH), 126.1 (CH), 44.0 (NCH), 43.7 (NCH).

(4-methoxyphenyl)-3-phenylaziridin-2-yl)methanone 4.72f 268

Prepared according the general procedure VII, using 150.05 mg (0.21 mmol) 4.41f and 53.45 mg (0.46 mmol) TMEDA in 1 ml CH2Cl2. The desired product was isolated as pale yellow oil (43.05 mg, 0.17 mmol, 84%)

181

Experimental Part

1 H NMR (400 MHz, CD2Cl2) δ 7.99 (d, J = 8.9 Hz, 2H), 7.40–7.33 (m, 5H), 6.96 (d, J = 8.9 Hz, 2H), 3.88 (s, 3H), 3.47 (d, J = 2.4 Hz, 1H), 3.15 (d, J = 2.3 Hz, 1H), 2.64 (s, 1H).13C

NMR (101 MHz, CD2Cl2) δ 193.9 (C), 164.29 (C), 139.0 (C), 130.68, 129.1 (CH), 128.6 (CH), 128.5 (CH), 127.7 (CH), 126.3 (CH), 114.0 (CH), 55.7 (NCH), 43.8 (NCH), 43.1

(OCH3).

Benzyl-7-azabicyclo[4.1.0]heptane-7-carboxylate 4.72k269

Prepared according the general procedure VIII, using 223.35 mg (0.40 mmol) 4.41k, 102.26 mg (0.88 mmol) TMEDA in 1 ml CH2Cl2 and 41 mg (0.08 mmol) B(C6F5)3. The protection was achieved with 171 µl (1.2 mmol) of CbzCl. The desired product was isolated as colourless oil (76.33 mg, 0.33 mmol, 82%).

1 H NMR (400 MHz, CDCl3) δ 7.31–7.39 (m, 5H, 5CH), 5.11 (s, 2H, CH2), 2.65 (dd, J = 3.2,

1.6 Hz, 2H, CH2), 1.90–1.97 (m, 2H, CH2), 1.78–1.81 (m, 2H, CH2), 1.37–1.41(m, 2H, CH2), 13 1.21–1.25 (m, 2H, CH2). C NMR (101 MHz, CDCl3) δ 163.2 (CH), 128.5 (CH), 128.3

(CH), 128.1 (CH), 128.0 (CH), 67.7 (CH2), 37.0 (CH2), 23.6 (CH2), 19.7 (CH2). benzyl-9-azabicyclo[6.1.0]nonane-9-carboxylate 4.72l

Prepared according the general procedure VIII, using 193.52 mg (0.33 mmol) 4.41l, 83.67 mg

(0.72 mmol) TMEDA in 1.1 ml CH2Cl2 and 34 mg (0.07 mmol) B(C6F5)3. The protection was achieved with 47 µl of CbzCl. The desired product was isolated as colourless oil (80.39 mg, 0.31 mmol, 95%).

1 H NMR (400 MHz, CDCl3) δ 7.42–7.29 (m, 5H, 5CH), 5.13 (s, 2H, CH2), 4.04 (t, J = 8.3 Hz, 1H), 3.92 (dtd, J = 9.9, 7.6, 2.0 Hz, 1H), 2.22 (ddt, J = 15.4, 9.8, 2.7 Hz, 1H), 2.05 (dtd, J = 15.8, 6.8, 2.9 Hz, 2H), 2.00–1.84 (m, 2H), 1.82–1.35 (m, 9H). 13C NMR (101 MHz,

CDCl3) δ 155.8 (CH), 155.1 (CH), 136.5 (CH), 135.1 (CH), 69.7 (CH2), 66.0 (CH2), 32.3

(CH2), 26.0 (CH2), 25.8 (CH2), 25.4 (CH2), 23.7 (CH2).

182

Experimental Part

benzyl-2-butyl-3-methylaziridine-1-carboxylate 4.72m

Prepared according the general procedure VIII, using 137.86 mg (0.24 mmol) 4.41m, 61.59 mg (0.53 mmol) TMEDA in 1.05 ml CH2Cl2 and 26 mg (0.05 mmol) of B(C6F5)3. The protection is achieved with 104 µl (0.72 mmol) of CbzCl. The desired product was isolated as colourless oil (51.94 mg, 0.21 mmol, 88%)

1 H NMR (400 MHz, CDCl3) δ 7.60–7.03 (m, 5H), 5.19 (s, 2H), 2.47–2.25 (m, 1H), 2.06 (dd, J = 12.8, 6.6 Hz, 1H), 1.87–1.70 (m, 1H), 1.69 (s, 2H), 1.52 (d, J = 6.7 Hz, 1H), 1.03–0.75 13 (m, 8H). C NMR (101 MHz, CDCl3) δ 157.8 (CH), 156.0 (CH), 154.0 (CH), 143.4 (CH),

135.5 (CH), 67.8 (CH2), 28.7 (CH2), 26.9 (CH2), 24.8 (CH2), 12.6 (CH3), 10.4 (CH3). benzyl-2,3-diethylaziridine-1-carboxylate 4.72n

Prepared according the general procedure VIII, using 196.14 mg (0.35 mmol) 4.41n, 89.48 mg (0.77 mmol) TMEDA in 1.1 ml CH2Cl2 and 37 mg (0.07 mmol) B(C6F5)3. The protection is achieved with 47 µl (1.05 mmol) of CbzCl. The desired product was isolated as colourless oil (67.66 mg, 0.29 mmol, 84%)

1 H NMR (400 MHz, CDCl3) δ 7.40–7.31 (m, 5H, 5CH), 5.18 (s, 2H, CH2), 5.14–5.08 (m, 2H), 4.05–3.93 (m, 1H), 3.87–3.73 (m, 1H), 1.72 (ddtd, J = 29.0, 14.4, 7.2, 2.8 Hz, 2H), 1.06 13 (t, J = 7.3 Hz, 3H, CH3), 0.97 (t, J = 7.5 Hz, 3H, CH3). C NMR (101 MHz, CDCl3) δ 157.9

(CH), 156.1 (CH), 155.0 (CH), 144.4 (CH), 136.0 (CH), 67.8 (CH2), 26.9 (CH2), 24.4 (CH2),

11.6 (CH3), 10.4 (CH3).

269 J. K. Ekegren, P. Roth, K. Källström, T. Tarnai, P. G. Andersson, Org. Biomol. Chem. 2003, 1, 358.

183

Experimental Part

imino(methyl)(phenyl)-l6-sulfanone 4.65a270

Prepared according the general procedure VII, using 178.76 mg (0.29 mmol) 4.66a and 74.37 mg (0.64 mmol) TMEDA in 1.1 ml CH2Cl2. The product was purified by column chromatography using silica gel and CH2Cl2/MeOH + 0.1% Et3N, 9/1 (v/v) as eluent.The desired product was isolated as colourless oil (37.25 mg, 0.24 mmol, 82%)

1 H NMR (400 MHz, CDCl3) δ 8.10–7.93 (m, 2H, 2CH), 7.68–7.59 (m, 1H, CH), 7.56 (dd, J 13 = 8.2, 6.6 Hz, 2H, 2CH), 3.36–3.29 (m, 1H, NH), 3.17 (s, 3H, CH3). C NMR (101 MHz,

CDCl3) δ 142.6 (CH), 133.4 (CH), 129.4 (CH), 127.7 (CH), 45.9 (CH3). imino(methyl)(p-tolyl)-l6-sulfanone 4.65b263

Prepared according the general procedure VII, using 214.49 mg (0.34 mmol) 4.66b and 87.15 mg (0.75 mmol) TMEDA in 1.5 ml CH2Cl2. The product was purified by column chromatography using silica gel and CH2Cl2/MeOH + 0.1% Et3N, 9/1 (v/v) as eluent. The desired product was isolated as colourless oil (47.38 mg, 0.28 mmol, 82%).

1 H NMR (400 MHz, CD2Cl2) δ 7.91–7.74 (m, 2H, 2CH), 7.39–7.20 (m, 2H, 2CH), 3.02 (s, 13 3H, CH3), 2.42 (s, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 143.8 (CH), 140.8 (CH), 129.7

(CH), 127.6 (CH), 46.3 (CH3), 21.2 (CH3).

(R)-(–)-imino(methyl)(p-tolyl)-l6-sulfanone 4.65b221b

Prepared according the general procedure V, using 35.00 mg (0.23 mmol) (R)-(+)-p- tolylmethylsulfoxide, 114.00 mg (0.24 mmol) N-aminoacridinium 2.5j in 1 ml CH2Cl2 and 88

270 C. M. M. Hendriks, P. Lamers, J. Engel, C. Bolm, Adv. Synth. Catal. 2013, 355, 3363

184

Experimental Part

mg (0.27 mmol) PIDA in 1 ml CH2Cl2. The desired product was isolated as a red solid (126.08 mg, 0.20 mmol, 88%). Then the unprotected sulfoximine is obtained according the general procedure VII, using 60 mg (95 µmol) of previously obtained protected sulfoximine and 24.3 mg (209.0 µmol) TMEDA in 1 ml CH2Cl2. The product was purified by column chromatography using silica gel and CH2Cl2/MeOH + 0.1% Et3N, 9/1 (v/v) as eluent. The desired product was isolated as colourless oil (11.25 mg, 66.50 µmol, 70%).

25 -1 [α] 589 = –24.3 (with C = 0.144 g.ml )

(4-chlorophenyl)(imino)(methyl)-l6-sulfanone 4.65c263

Prepared according the general procedure VII, using 221.29 mg (0.34 mmol) 4.66b and 87.15 mg (0.75 mmol) TMEDA in 1.1 ml CH2Cl2. The product was purified by column chromatography using silica gel and CH2Cl2/MeOH + 0.1% Et3N, 9/1 (v/v) as eluent. The desired product was isolated as colourless oil (56.89 mg, 0.30 mmol, 90%)

1 H NMR (400 MHz, CDCl3) δ 8.12–7.71 (m, 2H, 2CH), 7.52 (d, J = 8.4 Hz, 2H, 2CH), 3.13 13 (s, 3H), 2.73 (s, 1H, CH3). C NMR (101 MHz, CDCl3) δ 141.6 (CH), 139.9 (CH), 129.6

(CH), 129.2 (CH), 46.1 (CH3). iminodiphenyl-l6-sulfanone 4.65d271

Prepared according the general procedure VII, using 264.62 mg (0.39 mmol) 4.66d and 98.77 mg (0.85 mmol) TMEDA in 1.4 ml CH2Cl2. The product was purified by column chromatography using silica gel and CH2Cl2/MeOH + 0.1% Et3N, 9/1 (v/v) as eluent. The desired product was isolated as colourless oil (65.48 mg, 0.30 mmol, 78%)

1 H NMR (400 MHz, CDCl3) δ 8.07 (m, 2H, 2CH), 7.71–7.62 (m, 2H, 2CH), 7.58–7.36 (m, 13 6H, 6CH). C NMR (101 MHz, CDCl3) = δ 143.3 (CH), 132.6 (CH), 129.2 (CH), 127.9, (CH)

271 H. Okamura, C. Bolm, Org. Lett. 2004, 6, 1305.

185

Experimental Part

diphenyl-l4-sulfanimine 4.74a272

Prepared according the general procedure VIII, using 106.01 mg (0.16 mmol) 4.66d and

40.67 mg (0.35 mmol) TMEDA in 1 ml CH2Cl2 and 17 mg (0.03 mmol) of B(C6F5)3. The product was purified by column chromatography using silica gel and CH2Cl2/MeOH + 0.1%

Et3N, 9/1 (v/v) as eluent. The desired product was isolated as colourless oil (24.03 mg, 0.12 mmol, 78%)

1 13 H NMR (400 MHz, CDCl3) δ 7.47–7.54 (m, 10 H, 10CH). C NMR (101 MHz, CDCl3) δ 137.2 (CH), 130.7 (CH), 129.1 (CH), 129.0 (CH).

272 N. Furukawa, S. Oae, T. Yoshimura, Synthesis 1976, 30.

186

Experimental Part

Synthesis and Properties of Chiral pH-Sensitive Quinacridines, BODIPY-like and Azobenze Fluorophores

1,13-dimethoxy-6-nitro-5,9-dipropyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b- + ylium tetrafluoroborate [5.1•H ][BF4]

+ DMQA 1.43 (100.0 mg, 0.2 mmol) was dissolved in CH2Cl2 (8 ml) at 25 °C, then 8 ml of nitric acid (60%) are slowly added to the dark pink solution and the reaction mixture is vigorously agitated during 9 min (the solution became bloody red). After complete consumption of the starting quinacridine DMQA+ 1.43 (monitored by TLC and ESI-MS analysis), 30 ml of aqueous solution (1M) of NaOH were carefully and slowly added to neutralize the excess of acid and basified the solution. The product was extracted from the aqueous phase with CH2Cl2 (60 ml). The organic phase was dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with silica using CH2Cl2/MeOH and then washed with 10 ml solution of 1M solution HBF4 in water. The compound is dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound (107.97 mg, 0.19 mmol, 99%).

Rf = 0.75 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 8.82 (d, J = 9.6 Hz, 1H, CH), 8.13 (d, J = 8.9 Hz, 1H, CH), 7.99 (t, J = 8.4 Hz, 1H, CH), 7.63 (d, J = 9.3 Hz, 2H, 2CH), 7.49 (d, J = 8.8 Hz, 1H, CH), 7.10 (d, J = 8.1 Hz, 1H, CH), 7.04–6.96 (m, 1H, CH), 4.96–4.77 (m, 2H, CHH), 4.65 (dt, J =

15.8, 7.6 Hz, 1H, CHH), 3.84 (s, 3H, OCH3), 3.79 (s, 3H, OCH3), 3.50 (dt, J = 14.3, 8.2 Hz,

1H, CH), 2.22 (ddd, J = 15.8, 11.0, 7.0 Hz, 2H, CH2), 1.86 – 1.65 (m, 2H, CH2), 1.29 (t, J = 13 7.4 Hz, 3H, CH3), 0.46 (t, J = 7.3 Hz, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 159.6 (C), 159.0 (C), 141.2 (C), 141.1 (C), 140.8 (C), 140.7 (C), 139.0 (C), 137.4 (CH), 135.9 (CH), 134.0 (CH), 131.5 (CH), 119.9 (C), 116.3 (CH), 113.9 (CH), 109.8 (CH), 107.7 (CH), 106.1

(CH), 105.1 (CH), 104.8 (CH), 58.1 (OCH3), 56.1 (OCH3), 55.9 (CH2), 22.0 (CH2), 20.6 19 (CH2), 10.7 (CH3), 10.2 (CH3). F NMR (282 MHz, CD2Cl2) δ –152.33 (20%), –152.37

187

Experimental Part

-1 (80%). IR: (in CH2Cl2, cm ): ν = 1652, 1597, 1504, 1468, 1405, 1346, 1263, 1228, 1179, 1061, 1038, 816, 785, 753, 703, 547

6-formyl-1,13-dimethoxy-5,9-dipropyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b- + ylium tetrafluoroborate [5.2•H ][BF4]

DMQA+ 1.43 (617.0 mg, 1.2 mmol) was dissolved in DMF (1.11 ml, 12 equiv, 14.40 mmol) and the solution was heated to 90 °C. Phosphorous oxychloride (3.2 ml, 24 equiv, 34.5 mmol) was then added slowly and the reaction mixture was allowed to stir for 1 h at 90 °C. After complete consumption of the starting quinacridine 1.43e (monitored by TLC and ESI-MS analysis), the flask was allowed to cool to 20 °C and ice water (30 mL) was carefully and slowly added. The product was extracted from the aqueous phase with CH2Cl2 (100 ml) and the combined organic phase was then washed with a solution of 5% LiCl in water. The organic phase was dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with basic alumina using CH2Cl2/MeOH and then washed with 30 ml solution of 1M solution HBF4 in water. The compound is dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound (538.3 mg, 1.0 mmol, 85%).

Rf = 0.625 (Neutral alumina, CH2Cl2/MeOH, 98:2). 1 H NMR (400 MHz, CD2Cl2) δ 10.17 (s, 1H, CHO), 8.60 (d, J = 9.0 Hz, 1H, CH), 8.07 (t, J = 8.2 Hz, 1H, CH), 7.96 (t, J = 8.4 Hz, 1H, CH), 7.68 (d, J = 9.0 Hz, 1H, CH), 7.56 (d, J = 8.8 Hz, 2H, 2×CH), 7.05 (d, J = 8.1 Hz, 1H, CH), 6.97 (d, J = 8.0 Hz, 1H, CH), 5.20–5.13 (m, 1H, CH), 4.82–4.74 (m, 1H, CH), 4.64 – 4.55 (m, 1H, CH), 4.09–4.01 (m, 1H, CH), 3.82 (s,

3H, OCH3), 3.78 (s, 3H, OCH3), 2.30–2.17 (m, 2H, CH2), 1.81–1.67 (m, 2H, CH2), 1.30 (t, J 13 = 7.4 Hz, 3H, CH3), 0.41 (t, J = 7.3 Hz, 3H, CH3). C NMR (101 MHz, CD2Cl2) δ 186.9 (C), 160.2 (C), 159.5 (C), 142.4 (CH), 142.0 (C), 141.8 (C), 141.6 (C), 141.5 (C), 140.9 (C), 138.9 (CH), 137.4 (CH), 120.1 (C), 117.7 (C), 116.8 (C), 114.1 (C), 110.6 (CH), 108.1 (CH),

106.9 (CH), 105.2 (CH), 104.8 (CH), 60.8 (CH2), 56.5 (OCH3), 56.4 (OCH3), 23.0 (CH2), 19 21.0 (CH2), 11.3 (CH3), 10.8 (CH3). F NMR (282 MHz, CD2Cl2) δ –152.33 (20%), –152.37

188

Experimental Part

-1 (80%). IR: (in CH2Cl2, cm ): ν = 1652, 1597, 1504, 1468, 1405, 1346, 1263, 1228, 1179, 1061, 1038, 816, 785, 753, 703, 547.

1,13-dimethoxy-8-nitro-5-phenyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b- + ylium tetrafluoroborate [5.3•H ][BF4]

Quinacridine 2.4e (100 mg, 250 µmol) was dissolved in CH2Cl2 (4 ml) at 25 °C, then 4 ml of nitric acid (60%) are slowly added to the dark pink solution and the reaction mixture is vigorously agitated during 9 min (the solution became bloody red). After complete consumption of the starting quinacridine 2.4e (monitored by TLC and ESI-MS analysis), 10 ml of aqueous solution (1M) of NaOH were carefully and slowly added to neutralize the excess of acid and basified the solution. The product was extracted from the aqueous phase with CH2Cl2 (60 ml). The organic phase was dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with silica using

CH2Cl2/MeOH and then washed with 10 ml solution of 1M solution HBF4 in water. The compound is dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound (127 mg, 237 µmol, 96%).

Rf = 0.5 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 13.11 (s, 1H, NH), 8.60 (d, J = 9.6 Hz, 1H, CH), 7.93 (t, J = 8.3 Hz, 1H, CH), 7.80 – 7.69 (m, 4H, 4×CH), 7.45 (d, J = 8.4 Hz, 1H, CH), 7.41 – 7.34 (m, 1H, CH), 7.00 (d, J = 3.2 Hz, 1H, CH), 6.98 (d, J = 3.2 Hz, 1H), 6.62 (d, J = 8.8 Hz, 1H, CH), 13 6.56 (d, J = 9.7 Hz, 1H, CH), 3.78 (s, 3H, OCH3), 3.78 (s, 3H, OCH3). C NMR (101 MHz,

CD2Cl2) δ 160.0 (C), 159.4 (C), 144.4 (C), 143.9 (C), 142.9 (C), 140.4 (C), 138.4 (CH), 138.0 (CH), 136.9 (C), 134.6 (C), 132.8 (CH), 132.3 (CH), 131.4 (CH), 128.7 (CH), 127.6 (CH), 125.1 (CH), 116.5 (C), 113.1 (C), 113.0 (C), 110.6 (CH), 109.3 (CH), 106.2 (CH), 105.5 19 (CH), 105.4 (CH), 56.0 (OCH3), 56.0 (OCH3). F NMR (282 MHz, CD2Cl2) δ –152.05 -1 (20%), –152.10 (80%). IR: (in CH2Cl2, cm ): ν = 1652, 1597, 1504, 1468, 1405, 1346, 1263,

1228, 1179, 1061, 1038, 816, 785, 753, 703, 547. HRMS (ESI) calculated for [C28, H21, N2, + O3, (M )]: 450.14548. Found: 450.1450.

189

Experimental Part

8-formyl-1,13-dimethoxy-5-phenyl-5,9-dihydro-13bH-quinolino[2,3,4-kl]acridin-13b- + ylium tetrafluoroborate [5.4•H ][BF4]

Quinacridine 2.4e (100 mg, 250 µmol) was dissolved in DMF (0.231 ml, 12 equiv, 2.97 mmol) and the solution was heated to 90 °C. Phosphorous oxychloride (0.65 ml, 24 equiv, 6.92 mmol) was then added slowly and the reaction mixture was allowed to stir for 1 h at 90 °C. After complete consumption of the starting quinacridine 2.4e (monitored by TLC and ESI- MS analysis), the flask was allowed to cool to 20 °C and ice water (10 ml) was carefully and slowly added. The product was extracted from the aqueous phase with CH2Cl2 (60 ml) and the combined organic phase was then washed with a solution of 5% LiCl in water. The organic phase was dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with basic alumina using CH2Cl2/MeOH and then washed with 10 ml solution of 1M solution HBF4 in water. The compound is dissolved in

CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title red compound (88 mg, 185 µmol, 75%).

Rf = 0.55 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 14.04 (s, 1H, NH), 10.14 (s, 1H, CHO), 8.26 (d, J = 8.9 Hz, 1H, CH), 8.02 (t, J = 8.3 Hz, 1H, CH), 7.86 (tdd, J = 8.0, 6.7, 5.2, 2.2 Hz, 3H, 3×CH), 7.80 (dd, J = 8.8, 8.1 Hz, 1H, CH), 7.56 – 7.51 (m, 1H, CH), 7.49 (d, J = 8.5 Hz, 1H, CH), 7.44 (d, J = 8.6 Hz, 1H, CH), 7.04 (dd, J = 10.9, 8.2 Hz, 2H, 2×CH), 6.73 (d, J = 8.9 Hz, 1H), 6.69 (d, 13 J = 8.8 Hz, 1H, CH), 3.88 (s, 3H, OCH3), 3.86 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 192.7 (CHO), 160.0 (C), 159.5 (C), 144.2 (C), 143.9 (C), 143.3 (C), 141.6 (CH), 140.1 (CH), 138.7 (CH), 138.2 (CH), 137.8 (CH), 137.0 (CH), 132.3 (CH), 131.5 (CH), 131.3 (CH), 128.8 (CH), 127.6 (CH), 116.3 (C), 113.2 (C), 113.0 (C), 110.6 (C), 109.8 (CH), 109.27 (CH), 19 106.3 (CH), 105.0 (CH), 104.9 (CH), 55.9 (OCH3), 55.9 (OCH3). F NMR (282 MHz, -1 CD2Cl2) δ= –152.54 (20%), –152.59 (80%). IR: (in CH2Cl2, cm ): ν = 1652, 1597, 1504,

1468, 1405, 1346, 1263, 1228, 1179, 1061, 1038, 816, 785, 753, 703, 547. HRMS (ESI) + calculated for [C28, H21, N2, O3 (M )]: 433.1547. Found: 433.1547.

190

Experimental Part

6-fluoro-1,15-dimethoxy-7,11-diphenyl-6,11-dihydro-15bH-[1,3,2]diazaborinino[5,6,1- de]quinolino[4,3,2-mn]acridin-7-ium-15b-ylium fluoride tetrafluoroborate + [5.15•H ][BF4]

+ Imine formation: To a solution of quinacridine [5.4•H ][BF4] (40 mg, 77 µmol) in CH3CN (2 ml) containing molecular sieves (5 mg) was added aniline (85 µmol, 1.1 equiv). The reaction mixture was allowed to stir for 1.5 h at 65 °C. After complete consumption of the starting quinacridine 5.4 (monitored by TLC and ESI-MS analysis), the purple reaction mixture was cooled to 25 °C. The molecular sieves were removed by filtration and the cake washed with CH3CN (20 ml). After concentration under reduced pressure the purple compound was used for the next step without further purification.

BODIPY-like synthesis: To a solution of previously prepared imine (45 mg, 76 µmol) in 4 ml of dry CH2Cl2 at 25 °C, was added N,N-Diisopropylethylamine (5.5 equiv, 529 µmol). The reaction is allowed to stir 10 minutes then BF3•Et2O (48% solution, 7 equiv, 832 µmol) was added slowly and the reaction mixture was stirred for 12 hours. After complete consumption of the starting imine (monitored by TLC and ESI-MS analysis) 10 ml of distilled water were added and the desired product was extracted from the aqueous phase with CH2Cl2 (3 times).

The organic phase was dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with silica gel using CH2Cl2/MeOH and the product washed with a solution with 10 ml of 1M aqueous solution of HBF4. The compound was dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title orange compound 5.15 (39.3mg) in 82% yield.

Rf = 0.5 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (500 MHz, CD2Cl2) δ 8.86 (dt, J = 7.3, 3.0 Hz, 1H, CH), 8.40 (dt, J = 9.1, 3.1 Hz, 1H, CH), 8.30 (d, J = 9.1 Hz, 1H, CH), 8.01 (dd, J = 9.1, 7.9 Hz, 1H, CH), 7.92–7.82 (m, 3H), 7.82–7.76 (m, 1H, CH), 7.72 (d, J = 7.6 Hz, 2H, 2×CH), 7.65 – 7.52 (m, 5H, 5×CH), 7.50– 7.43 (m, 1H, CH), 7.06 (d, J = 8.0 Hz, 1H, CH), 7.02 (d, J = 7.8 Hz, 1H, CH), 6.79 (d, J = 8.9

Hz, 1H, CH), 6.73 (d, J = 8.5 Hz, 1H, CH), 3.84 (s, 3H, OCH3), 3.83 (s, 3H, OCH3).

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13 C NMR (126 MHz, CD2Cl2) δ 160.5 (CH), 159.0 (C), 158.6 (C), 145.5 (C), 142.5 (CH), 142.2 (CH), 141.5 (CH), 141.4 (CH), 141.2 (C), 139.1 (C), 136.4 (C), 136.3 (C), 131.5 (C), 130.7 (CH), 130.7 (CH), 129.1 (CH), 128.8 (CH), 128.0 (CH), 126.8 (CH), 123.6 (C), 115.15 (C), 114.1 (CH), 112.8 (CH), 112.7 (CH), 112.7 (CH), 112.4 (CH), 108.7 (CH), 106.8 (CH), 19 105.7 (CH), 104.4 (CH), 104.0 (CH). F NMR (282 MHz, CD2Cl2) δ –116.99 (ddd, J = 95.5, 67.5, 33.8 Hz), –120.94 (ddd, J = 95.3, 61.6, 30.8 Hz), –152.54 (20%), –152.59 (80%). 11B

NMR (128 MHz, CD2Cl2) δ 2.67 (t, J = 32.0 Hz), –1.05.

6-fluoro-1,15-dimethoxy-7,11-diphenyl-6,11-dihydro-15bH-quinolino[4,3,2- mn][1,2,4,3]triazaborinino[6,5,4-de]acridin-7-ium-15b-ylium fluoride tetrafluoroborate + [V-14•H ][BF4]

To a solution of quinacridine 5.8 (42 mg, 70 µmol) in 2.5 ml of dry CH2Cl2 at 25 °C, was added N,N-Diisopropylethylamine (5.5 equiv, 387 µmol). The reaction is allowed to stir 10 minutes then BF3•Et2O (48% solution, 7 equiv, 1 mmol) was added slowly and the reaction mixture was stirred for 12 hours. After complete consumption of the starting quinacridine 5.8 (monitored by TLC and ESI-MS analysis) 10 ml of distilled water were added and the desired product was extracted from the aqueous phase with CH2Cl2 (3 times). The organic phase was dried over Na2SO4 and concentrated under reduced pressure. The compound was purified by column chromatography with silica gel using CH2Cl2/MeOH and the product washed with a solution with 10 ml of 1M aqueous solution of HBF4. The compound was dissolved in CH2Cl2 and selective precipitation by addition of diethyl ether afforded the title pink compound in 25% (11.3 mg).

Rf = 0.45 (basic alumina, CH2Cl2/MeOH, 98:2) 1 H NMR (400 MHz, CD2Cl2) δ 10.44 (dd, J = 7.3, 4.5 Hz, 1H, CH), 10.39 (d, J = 9.5 Hz, 1H, CH), 10.14 (d, J = 7.7 Hz, 2H, 2×CH), 10.10 (dd, J = 9.0, 8.1 Hz, 1H, CH), 9.98–9.79 (m, 4H, 4×CH), 9.64–9.51 (m, 4H, 4×CH), 9.50 – 9.45 (m, 1H, CH), 9.18 (d, J = 8.1 Hz, 1H, CH), 9.15 (d, J = 8.2 Hz, 1H, CH), 8.91 (d, J = 9.5 Hz, 1H, CH), 8.82 (d, J = 8.7 Hz, 1H, CH), 13 5.84 (s, 3H, OCH3), 5.84 (s, 3H, OCH3). C NMR (101 MHz, CD2Cl2) δ 148.7 (C), 144.5 (C), 143.7 (C), 139.92 (C), 138.5 (CH), 134.2 (CH), 133.8 (CH), 133.5 (CH), 132.7 (CH),

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131.5 (CH), 130.3 (CH), 129.3 (CH), 124.6 (C), 112.7 (CH), 112.0 (CH), 108.7 (CH), 108.7 + (CH), 58.1 (OCH3), 57.8 (OCH3). HRMS (ESI) calculated for [C33, H24, B, F2, N4, O7 (M )]: 19 557.1955. Found: 557.1952. F NMR (282 MHz, CD2Cl2) δ –113.56 to –114.75 (m, 1F), – 11 115.25 to –116.11 (m, 1F) –152.63 (20%), –152.68 (80%). B NMR (128 MHz, CD2Cl2) δ 1.75 (t, J = 34.3 Hz), –1.22.

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Appendix

Spectral and Photophysical Properties of Triangulenes 3.3 and 3.4 in Organic Solvents

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G H

I J

Figure E1. (A,C) Electronic absorption spectra and (B,D) titration curve recorded with aqueous solutions + of [3.3c•H ][PF6] in absence (A,B) and presence (C,D) of 4 mM of CTAB. (E) Electronic absorption spectra and (F) titration curve recorded with aqueous solutions of [3.4c•H+][TFA]. (G,I) Electronic absorption spectra and (H,J) titration curve recorded with aqueous solutions of [3.4c•H+][TFA] in absence (G,H) and presence (I,J) of 4 mM of CTAB. The solid lines in (B,D,F,H,J) are the best fit according to the equation (3.1).

Table E1. The pKa values of triangulenes under study. Compounds pKa (with CTAB, 4 mM) pKa + [3.3a•H ][PF6] 4.8 - [3.4a•H+][TFA] 4.8 2.1,[a][b] 5.0[b] + [c] [3.3b•H [PF6] 5.3 - + [3.3c•H [PF6] 6.6 7.7 [3.4c•H+[TFA] 6.5[b] 7.85

[a] The value of pKa 1 according to the approximation by equation (Eq. 3.2) [b] The presented values should be considered as estimations due to aggregation of neutral form [c] Could not be measured due to precipitation of 3.3b

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Figure E2 Absorption and emission spectra of (A) 3.3a•H+, (B) 3.3a, (C) 3.3b•H+ and (D) 3.3b in various solvents.

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+ + Figure E3. Fluorescence time profiles recorded with (A) [3.3a•H ][PF6], (B) 3.3a, (C) [3.3b•H ][PF6] (D) 3.3b in various solvents. Smooth lines are the best fits.

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Table E2. Fluorescence quantum yield (ΦF), fluorescence lifetime (τF) and rate constants of radiative (kR) and nonradiative (kNR) decay for protonated and neutral forms of 3.3a and 3.3b in various solvents

7 -1 7 -1 Compounds Solvents ΦF τF kR / 10 s kNR / 10 s

CHCl3 0.42 15.1 2.8 3.9 3.3aH+ CH3CN 0.26 11.6 2.3 6.4 DMSO 0.24 9.3 2.6 8.2 EtOH 0.27 12.1 2.3 6.0

D2O* 0.21* 11.8 1.7 6.8

H2O* 0.14* 7.7 1.7 11.4

CHCl3 0.34 11.7 2.9 5.6 3.3a CH3CN 0.22 9.1 2.4 8.6 DMSO 0.27 9.3 2.9 7.8 EtOH 0.20 11.8 1.7 6.8

D2O* 0.22* 10.9 2.0 7.1

H2O* 0.16* 7.8 2.0 10.8

CHCl3 0.39 14.0 2.8 4.3 3.3bH+ CH3CN 0.26 11.2 2.3 6.6 DMSO 0.25 9.3 2.7 8.1 EtOH 0.28 11.7 2.4 6.1

D2O 0.26 15.9 1.6 4.7

H2O 0.13 7.7 1.8 11.3

CHCl3 0.32 10.7 3.0 6.4 3.3b CH3CN 0.21 8.8 2.4 9.0 DMSO 0.27 8.9 3.0 8.2 EtOH 0.20 7.6 2.6 10.6

D2O 0.18 9.1 1.9 9.0

H2O 0.14 6.5 2.1 13.3

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Thermal Stability of [3.4a•H+][TFA].

The thermal stability of [3.4a•H+][TFA] was studied in PBS, binary mixture PBS :DMSO

1 :1 v/v and basic CH3CN (adjusted by triethylamine). The freshly prepared stock solution of dye in DMSO was added in a solution to reach the final dye concentration of 0.3 mM. The total sample volume was 0.5 ml and the presence of DMSO did not exceed 2% of the volume (with the exception of binary mixture). The concentration of 3.4a in the stock solution was determined by the absorption of 2 μl of stock solution in 2 ml of acidic CH3CN at 556 nm (extinction coefficient = 14800 M-1cm-1). Experiments were carried out in a quartz cell (optical path 2 mm) placed in the thermostated holder at 37 C. The absorption spectra recorded at different time intervals are presented in Figure E4.

Significant precipitation of the dye could be seen after one hour staining in PBS solution. The aggregation of 3.4a neutral form slows down in the presence of DMSO and it is negligible in the case of pure organic solvent like CH3CN. In the presence of water, 3.4a finally forms snowflake-like structures. A switch to acidic conditions after staining in aqueous environment does not restore the concentration of protonated form; a part of dye forms stable scattering particles. Thus, in aqueous environment 3.4a is thermally unstable molecule slowly reacting with surrounding molecules.

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Figure E4. Absorption spectra of 0.3 mM [3.4a•H+][TFA] in (A) PBS, (B) PBS:DMSO 1:1 v/v and (C) basic CH3CN recorded at different time after the sample placing in the thermostated holder at 37°C. (D) + Time profile of the absorption of 0.3 mM [3.4a•H ][TFA] in PBS (λmax = 562 nm, red points), in

PBS:DMSO 1:1 v/v (λmax = 556 nm, green points) and in basic CH3CN (λmax = 509 nm, violet points).

Tests of Photostability

The samples of 3.4a in CH3CN were irradiated by a Quanta-Ray LAB-130-10 Nd:YAG laser operating at 355 nm in a 10×8 mm2 quartz cell. The laser pulse energy was attenuated down to approximately 1 mJ, the repetition rate was 10 Hz, and the size of the laser beam on the surface of the quartz cell was approximately 0.5 cm2. The optical density of the samples was approximately 0.8 at 355 nm for 8 mm optical path. All solutions were bubbled with argon or oxygen for 15 minutes prior to and during irradiation.

The total photon flux for the used conditions is 2×1018 photons/(min×cm2). The values of the photodegradation yield Φdeg were estimated in the assumption that the only channel of dye degradation is the formation of aggregates. The amount of the dye in the sample was calculated using the sample volume V =1.65 ml, the absorption values at the maxima of bands

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(Figure E5) and the extinction coefficients 14800 M-1cm-1 at 556 nm for 3.4a•H+ 273 and 12000 M-1cm-1 at 515 nm for 3.4a.274 The degree of 3.4a•H+ degradation was estimated by an increase of absorption at 525 nm, assuming the equal absorption of starting compound and formed H-aggregates as it was observed for [4]helical quinacridines. Similar proposition was made for 3.4; the degradation was estimated by change of absorption at 546 nm. The -3 estimations give the following values: Φdeg < 1×10 for 3.4a under anaerobic conditions and -4 as Φdeg < 5×10 for other cases.

+ Figure E5. Absorption spectra of (A,C) 3.4a•H and (B,D) 3.4a in CH3CN recorded at different time intervals of 355 nm photolysis under (A,B) anaerobic and (C,D) aerobic conditions.

273 W. Laursen, B.; C. Krebs, F. Chem. Eur. J. 2001, 7, 1773. 274 This value was calculated from the absorption spectrum of 1a in acetonitrile, which concentration was determined under acidic conditions using the extinction coefficient value reported in 273. The shift of acidic to basic conditions was carried out by addition of 1 μl of trifluoroacetic acid in 1.65 ml of acetonitrile.

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X-Ray Datas For Quinacridine 2.4e Data were collected using the Cu radiation of an Agilent supernova X-ray diffractometer equipped with an Atlas CCD detector. Structure was solved using direct methods with the shelxs program and a full matrix least square refinement on F2 was performed using the shelxl software. Details of the refinement can be found in the table below.

Empirical formula C28H22Cl2N2O2 Formula weight 486.73 Temperature/K 197(14) Crystal system triclinic Space group P-1 a/Å 10.6488(8) b/Å 10.7004(10) c/Å 11.5108(5) α/° 74.077(6) β/° 86.961(5) γ/° 68.266(8) Volume/Å3 1169.89(16) Z 2

3 ρcalcmg/mm 1.382 m/mm-1 2.663 F(000) 505.0 Crystal size/mm3 0.4475 × 0.2818 × 0.2042 2Θ range for data collection 8 to 146.504° Index ranges -13 ≤ h ≤ 13, -13 ≤ k ≤ 13, -14 ≤ l ≤ 14 Reflections collected 16244 Independent reflections 4549[R(int) = 0.0575] Data/restraints/parameters 4549/67/366 Goodness-of-fit on F2 1.060

Final R indexes [I>=2σ (I)] R1 = 0.0671, wR2 = 0.1882

Final R indexes [all data] R1 = 0.0848, wR2 = 0.2122 Largest diff. peak/hole / e Å-3 0.31/-0.31

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Experimental Part

For Aziridine 4.41a

Table 1. Crystal data and structure refinement for wa_256c_squeeze. Identification code shelxl Empirical formula C38.62 H34.25 B Cl1.25 F4 N2 O5 Formula weight 737.55 Temperature 180(2) K Wavelength 1.54184 Å Crystal system Monoclinic Space group C 1 2/c 1 Unit cell dimensions a = 27.2422(8) Å = 90°. b = 12.3783(2) Å = 119.455(4)°. c = 24.0704(7) Å = 90°. Volume 7067.6(3) Å3 Z 8 Density (calculated) 1.386 Mg/m3 Absorption coefficient 1.720 mm-1 F(000) 3058 Crystal size 0.4108 x 0.3242 x 0.1653 mm3 Theta range for data collection 3.73 to 73.50°. Index ranges -33<=h<=30, -14<=k<=15, -26<=l<=29 Reflections collected 13809 Independent reflections 6904 [R(int) = 0.0162] Completeness to theta = 67.50° 99.9 % Absorption correction Analytical Max. and min. transmission 0.833 and 0.633 Refinement method Full-matrix least-squares on F2 Data / restraints / parameters 6904 / 0 / 456 Goodness-of-fit on F2 1.070 Final R indices [I>2sigma(I)] R1 = 0.0406, wR2 = 0.1132 R indices (all data) R1 = 0.0453, wR2 = 0.1173 Largest diff. peak and hole 0.213 and -0.240 e.Å-3

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Experimental Part

For Reduced Aziridine 4.74

A small disorder is present on the C8 cycle and was modelled using two parts.

Table 1 Crystal data and structure refinement for wa682h. Identification code wa682h

Empirical formula C31H36N2O4 Formula weight 500.62 Temperature/K 180.05(10) Crystal system monoclinic

Space group P21/n a/Å 13.5824(3) b/Å 8.1110(2) c/Å 24.3866(5) α/° 90 β/° 90.045(2) γ/° 90 Volume/Å3 2686.61(10) Z 4 3 ρcalcg/cm 1.238 μ/mm-1 0.651 F(000) 1072.0 Crystal size/mm3 0.6827 × 0.2492 × 0.0907 Radiation CuKα (λ = 1.54184) 2Θ range for data collection/° 7.448 to 147.102 -16 ≤ h ≤ 12, -9 ≤ k ≤ 9, -29 ≤ l ≤ Index ranges 29 Reflections collected 11261 5281 [R = 0.0199, R = Independent reflections int sigma 0.0239] Data/restraints/parameters 5281/45/357 Goodness-of-fit on F2 1.024

Final R indexes [I>=2σ (I)] R1 = 0.0424, wR2 = 0.1107

Final R indexes [all data] R1 = 0.0494, wR2 = 0.1182 Largest diff. peak/hole / e Å-3 0.18/-0.27

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Racemisation barrier determination

General procedure for the racemization of (+)-[(P)-1f][BF4] to [1f][BF4]: kinetic barrier. -6 Circular dichroism “Time course measurement” of (+)-[(P)-1f][BF4] (357 nm, c ~ 5.10 M, dibutyl sulfoxide) was recorded at 130 °C, 140 °C, 150°C during 1000 s. The kinetic barrier of racemization was determined by mathematical treatment.

Activation parameters for the racemization of (+)-[(P)-1f][BF4]: ln(k)=f(1000/T) plot

T [°C] T [K] 1000/T k ln(k)

130 403.15 2.4805 1.148E-04 -9.073 140 413.15 2.4204 5.723E-04 -7.466 150 423.15 2.3632 1.941E-03 -6.245

slope= -24.14 ± 1.56 - Ea/R intercept= 50.87 ± 3.78 Ln(A)

T 140 °C

Ea 200.7 ± 13.0 kJ/mol A 1.2E+22 ± 9.2E+20

H# = Ea - RT 197.3 ± - 12.8 kJ/mol S# = R [ln(h*A/k*T)- 1] 167.0 ± 12.4 J.K-1.mol-1 G# 128.3 ± -17.9 kJ/mol

205