DOCSLIB.ORG

Aromatic Compounds from Pyrylium Salts

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Aromatic Compounds from Pyrylium Salts Aromatic Compounds from Pyrylium Salts K. DlMROTH AND K. H. WOLF Chemisettes Institut der Universitat Marburg/Lahn Introduction The readily obtainable substituted pyrylium salts lend themselves to the preparation of numerous, often difficultly accessible, aromatic com­ pounds of both the heterocyclic and isocyclic series. The first known example of these reactions is the formation of pyridine and pyridinium derivatives described by Baeyer. Another reaction of this kind is the formation of thiopyrylium salts reported by Wizinger. Especially numer­ ous are the possibilities for the preparation of isocyclic aromatic com­ pounds, whereby known phenols and alkylated amines together with new nitrocompounds, ketones, carboxylic acids, nitriles, phenol carboxylic acids, aminonitriles, or hydrocarbons of the benzene, naphthalene, and phenanthrene series can be prepared in generally good yield. The use of pyrylium salts as the starting materials for the preparation of azulenes is also possible. In addition to a discussion of these reactions a survey of the methods available for the preparation of pyrylium salts will be given. Conversion of Pyrylium Salts into Heterocyclic Compounds Possessing Aromatic Character DERIVATIVES OF PYRIDINE As found by Baeyer [1], the original worker in this field, pyrylium salts can readily be converted into pyridine derivatives by warming with an aqueous ammonium carbonate solution. Following the preparation by Baeyer and Piccard [2] of collidine (2a) and 2,6-dimethyl-4-phenyl- pyridine (2b) from 2,4,6-trimethylpyrylium perchlorate (la) and 2,6- dimethyl-4-phenylpyrylium perchlorate (lb) respectively, this synthesis was extended to include other 2,4,6-tri-alkyl- and aryl-substituted pyryl­ ium salts by Dilthey [3], Gastaldi [4], and others [5], These reactions, however, served more to elucidate the constitution of the pyrylium salts, than in the preparation of specific pyridine derivatives. Nevertheless, a large number of difficultly accessible pyridine derivatives, e.g. 2,4,6- triphenylpyridine (2c) [3a], 2,3,4,6-tetraphenylpyridine (2d) [3c],penta- phenylpyridine [3c], or 1,4-bis-[3,5-diphenylpyridino(4)]benzene (2g) 357 358 K. DIMROTH AND K. H. WOLF [22], can be obtained readily in this manner. The disubstituted 2,6-di- phenylpyrylium perchlorate (lh) is also converted smoothly into 2,6- diphenylpyridine (2h) [6]; nucleophilic addition at C-2 (C-6) is pre­ ferred to that at C-4. A summary of the preparative methods for pyridine derivatives is to be found in [7]. (a) R2 = R4 = Re = CH3; R3 = H (b) R, = R6 = CH3; R4 = C6H5; Ra = H (c) R2 = R4 = Re = C6H5; R3 = H (d) R, = R4 = R6 = Rs = C6H5 (e) R2 = R6 = CH3; R4 = OCH3; R3 = H (£) R2 = R6 = CH3; R4 = NHCH3; R3 = H; NCHj'ClC^ instead of N in (2) C,H, (h) R2 = R6 = ; R4 = R3 = H The conversion of the pyrylium salts is almost always facile and quantitative; alcoholic ammonia is sometimes better suited than aqueous ammonium carbonate. As our own experiments [8] have shown, the re­ action proceeds particularly favorably when the pyrylium salt is sus­ pended in absolute ter t-butano\, and dry ammonia passed through; warming effects solution of the salt, and the ammonium salt of the in­ organic acid constituting the anion of the pyrylium salt (ammonium perchlorate or ammonium fluoborate) separates on cooling. The pyridine derivative which remains in solution often can be precipitated practically quantitatively by the addition of a little water. The conversion of pyrylium salts into pyridine derivatives fails when the heterocyclic oxygen atom of the pyrylium salt originates from a phenolic component. Hence neither chromylium nor xanthylium salts can be converted into quinoline or acridine derivatives. 2,4-Diphenyltetra- hydrobenzopyrylium perchlorate (3), however, gives a quantitative yield of 2,4-diphenyltetrahydroquinoline (4), by treatment with am­ monia in ter£-butanol [8]. The conversion of 1,3-disubstituted iso- AROMATIC COMPOUNDS FROM PYRYLIUM SALTS 359 chromylium salts (5b and c) into 1,3-disubstituted isoquinoline deriva­ tives (6b and c) can be accomplished similarly [8,9]. 6 5 H2 T 2 NH, i! © 1 + NH4C104 + H20 C«H5 C6H5 2 © cio4 (?) (4) Unsubstituted isochromylium chloroferrate (5a), readily accessible from homophthalaldehyde, yields, like the aldehyde itself, isoquinoline with ammonia [10], respectively, N-substituted isoquinolinium com­ pounds with primary aliphatic or aromatic amines [11]. + Nfl^X + H2Q (5) (6) (a) R, = R3 = H (b) Rl = R3 = ch3 (c) R, = R3 = CeH, Similarly, careful treatment of 2,6-dimethyl-4-methoxypyrylium perchlorate (le) with aqueous ammonia yields 2,6-dimethyl-4-methoxy- pyridine (2e) [1]. According to Anker and Cook [12] the 4-methoxy, and to some extent also the 4-methylmercapto [13] group in the pyrylium salt, are sufficiently reactive to allow their replacement by other nucleo­ philic groups, such as alkoxy, alkylmercapto, alkylamino, or dialkyl- amino. The most diverse pyridine derivatives can accordingly be prepared by subsequent treatment with ammonia. If the methoxypyrylium salt (le) is allowed to react with an excess of methylamine in methanol, both the heterocyclic oxygen atom and the methoxy group are replaced and 2,6-dimethyl-4-methylamino-N-methylpyridinium perchlorate (2f) is ob­ tained on precipitation with perchloric acid. DERIVATIVES OF PYRIDINIUM COMPOUNDS If 2,4,6-trisubstituted pyrylium salts (7) are allowed to react with primary aliphatic or aromatic amines instead of ammonia, the N-alkyl- ated or N-arylated pyridinium salts (8a) are obtained. In this reaction too, the first examples were discovered by Baeyer and Piccard [1,2]. 360 K. DIMROTH AND K. H. WOLF The method is exceptionally well suited to the synthesis of numerous pyridinium compounds, especially as it usually proceeds in excellent yield [14]- The only requirement is that the amine should not be too weakly basic. The simple aliphatic amines, such as methylamine, ethyl- amine, etc., can also be replaced by aromatic amines, such as aniline and its derivatives. Phenylhydrazine, «-methylphenylhydrazine [15], or semi­ carbazide [16] essentially react in similar fashion (to give 8b, c, d). Reaction with hydroxylamine yields pyridine oxides (8e), but only when the size of the a,a'-substituents is not excessive. Otherwise [e.g. with CH(CH;})2 and C(iH5 in the a,a'-position] reduction occurs and the pyri­ dine derivatives are obtained. (7) Rg, 1^, 1^ = aliphatic and aromatic groups (a) Rt = alkyl or aryl, hydroxyaryl etc. (b) R, = NHCQH (c) R1 = CH3NC6H5 (d) Rx = NHCONH2 (e) Ri = OH There exists thus far no other route for the preparation of the N—NH-arylpyridinium compounds (9) [17]. This class of compounds has been discovered as a result of the work of Schneider and co-workers [15], and is distinguished by a series of interesting reactions. With alkali they give strongly colored anhydro bases, which are to be regarded as + N—N betaines (10) [18], i.e. the heterocyclic pyridine nitrogen carries the positive, and the anilido nitrogen the negative charge. R = aryl or alkyl AROMATIC COMPOUNDS FROM PYRYLIUM SALTS 361 Of especial interest are the N-hydroxyphenylpyridinium salts which are readily formed from pyrylium salts by reaction with aminophenols, and which can be converted into pyridinium-N-phenol betaines by the action of strong bases [19]. The compounds may also be considered phenologs of pyridine-N-oxide. By suitable substitution of the pyridine as well as the aminophenol it is possible to obtain stable betaines which have unusually large solvatochromic and thermochromic effects. They are especially useful for the measurement of the polarity of solvents [20], The Z [21] or ET values which are found in this way determine the polarity of the solvent much better than the dielectric constant. The double conversion of a dipyrylocyanin dye (p. 371) into a di- pyridiniumcyanine dyestuff is also possible. In a similar way the bis- pyrylium salt (p. 382) from terephthalaldehyde and acetophenone [22] with p-aminophenol and its derivatives give the bis-pyridinium-N- phenolbetaines [23]. DERIVATIVES OF THIOPYRYLIUM COMPOUNDS While the unsubstituted pyrylium salt (11) is a rather unstable compound [24], the corresponding thiopyrylium salt (12) [27] is very stable and may be prepared readily by several different routes [25]. Its reactions, however, in contrast to those of benzothiopyrylium salts (13) [26] have hardly been investigated. (11) (12) (13) When treated with sodium sulfide in acetone, followed by precipita­ tion with acid, 2,4,6-trisubstituted pyrylium salts (14) usually undergo replacement of the heterocyclic oxygen atom by sulfur to give the thio­ pyrylium salts (16) [27] within a few minutes. The presence of inter­ mediates manifests itself by a blue coloration; Wizinger and Ulrich [28], Ar Ar Ar + 2HX - NaX 0N9© -NaX, -l^O Ar O Ar Ar O Ar S Ar X® X© (14) (15) (16) Ar = C6H5 or CH=CH— 362 K. DIMROTH AND K. H. WOLF the discoverers of this reaction, believe them to be the sodium salts of ketothioenols (15). The reaction published by Suld and Price [27] between phenyl lithium and 2,4,6-triphenylthiopyrylium perchlorate (17) in ethereal solution at a low temperature and in the absence of light, gave a stable amorphous product with a purple color which was described as 1,2,4,6-tetraphenyl- thiobenzene (18). On passing oxygen through an ethereal solution of the compound an oxypyrylium salt (19) was formed as well as diphenyl disulfide. This salt (19) was also prepared by an independent synthesis from benzalacetophenone and w-acetoxyacetophenone. The compound (18) was converted, in 25% yield, into the colorless 2,4,4,6-tetraphenyl- thiopyran (20) on being allowed to stand for a day. Aliphatic Grignard compounds give deep-colored intermediates with (17) which are quickly converted into 2- or 4-thiopyran derivatives. An interesting rearrangement of compound (19) to 3,5,6-triphenyl-2-pyrone has recently been found [28a]. DERIVATIVES OF PYRIDONE AND THIOPYRIDONE FROM PYRONE DERIVATIVES 4-Pyrones (21a) and, to an even greater extent, 2,6-alkyl-substituted 4-thiopyrones (21b) such as 2,6-dimethyl-4-thiopyrone, do not behave as true ketones or thioketones, but can be regarded as internal pyrylium salts (22a, b), i.e.
Load more

Recommended publications
  • Pyrylium Salt Chemistry Emerging As a Powerful Approach for the Cite This: Chem
    Chemical Science View Article Online PERSPECTIVE View Journal | View Issue Over one century after discovery: pyrylium salt chemistry emerging as a powerful approach for the Cite this: Chem. Sci., 2020, 11, 12249 All publication charges for this article construction of complex macrocycles and metallo- have been paid for by the Royal Society of Chemistry supramolecules Yiming Li, ab Heng Wanga and Xiaopeng Li *a Over one century after its discovery, pyrylium salt chemistry has been extensively applied in preparing light emitters, photocatalysts, and sensitizers. In most of these studies, pyrylium salts acted as versatile precursors for the preparation of small molecules (such as furan, pyridines, phosphines, pyridinium salts, thiopyryliums and betaine dyes) and poly(pyridinium salt)s. In recent decades, pyrylium salt chemistry has emerged as a powerful approach for constructing complex macrocycles and metallo-supramolecules. In this perspective, we attempt to summarize the representative efforts of synthesizing and self-assembling Received 20th August 2020 large, complex architectures using pyrylium salt chemistry. We believe that this perspective not only Creative Commons Attribution-NonCommercial 3.0 Unported Licence. Accepted 13th October 2020 highlights the recent achievements in pyrylium salt chemistry, but also inspires us to revisit this chemistry DOI: 10.1039/d0sc04585c to design and construct macrocycles and metallo-supramolecules with increasing complexity and rsc.li/chemical-science desired function. 1. Introduction pyrylium salt with perchlorate as the counterion was reported in 1911 by Baeyer;7 however, since the discovery of pyrylium salts, Pyrylium salts are a type of six-membered cationic heterocycles such salts have been underappreciated for about a half-century.
    [Show full text]
  • Direct, Catalytic, Intermolecular Anti
    DIRECT, CATALYTIC, INTERMOLECULAR ANTI-MARKOVNIKOV HYDROACETOXYLATIONS OF ALKENES ENABLED VIA PHOTOREDOX CATALYSIS, AND INVESTIGATIONS INTO THE MECHANISM OF THE POLYMERIZATION OF 4-METHOXYSTYRENE INITIATED BY PYRYLIUM SALTS Andrew Perkowski A dissertation submitted to the faculty of the University of North Carolina at Chapel Hill in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry. Chapel Hill 2014 Approved by: David A Nicewicz Erik Alexanian Marcey Waters Maurice Brookhart Joseph Templeton © 2014 Andrew Perkowski ALL RIGHTS RESERVED ii ABSTRACT Andrew Perkowski: Direct, Catalytic, Intermolecular Anti-Markovnikov Hydroacetoxylations of Alkenes Enabled via Photoredox Catalysis, and Investigations into the Mechanism of the Polymerization of 4-Methoxystyrene Initiated by Pyrylium Salts (Under the Direction of David A. Nicewicz) I. Intermolecular Anti-Markovnikov Addition of Oxygen Nucleophiles to Alkenes: Direct and Indirect Catalytic Methods to Address a Fundamental Challenge Markovnikov versus anti-Markovnikov functionalization of alkenes is discussed, as well as the inherent challenge in overcoming Markovnikov selectivity. Stoichiometric and catalytic methods for anti-Markovnikov functionalization are discussed and appraised. II. Anti-Markovnikov Addition of Oxygen Nucleophiles to Alkene Cation Radical Intermediates The formation of alkene cation radicals is disccused, as well as examples of anti- Markovnikov nucleophilic addition to alkene cation radicals. III. The Direct Anti-Markovnikov
    [Show full text]
  • ABSTRACT Synthesis of New Chiral Pyrylium Salts, the Corresponding
    ABSTRACT Synthesis of New Chiral Pyrylium Salts, the Corresponding Phosphinine and Pyridine Derivatives and the Kinetic Studies of the Epimerization of Pyrylium Salts Nelson A. van der Velde, Ph.D. Mentor: Charles M. Garner, Ph.D. Despite the versatility of pyrylium salts as precursors to many heteroaromatic systems, chiral pyrylium salts are almost unknown in the literature. One reason for this scarcity is that pyrylium salts are often involved as intermediates rather than as isolated and characterized materials. Another is that many pyrylium salts preparations tend to result in non-characterizable black solid due to polymerization reactions. We have developed the synthesis of several new chiral pyrylium salts and their conversion to the corresponding pyridines and phosphinines. This work almost triples the number of reported chiral pyrylium salts, and also represents the first racemizable/epimerizable pyrylium salts. The derived phosphinines and pyridines represent rare alpha-chiral ligands for transition metals. Interestingly, only a few examples of chiral phosphinines have been reported in the literature. Incorporation of chirality directly (i.e., alpha to aromatic ring) onto these planar ring systems has proven to be difficult. From our pyrylium salts we have synthesized new phosphinines with the chirality as close as possible to the phosphorus center. Two known pyridinium salts were also prepared with the thiosemicarbazone moiety. The cytotoxicity and inhibition of cruzain were evaluated and found to be non-actives. Our interest in chiral pyrylium salts led us to investigate the configurational stability of chiral centers alpha to the pyrylium ring. Although no epimerizable (or even racemizable) pyrylium salts have been reported, deuterium exchange at ortho and especially para benzylic positions is well-known, suggesting that epimerization is possible.
    [Show full text]
  • Catalytic Synthesis of 1,3,5-Triphenylbenzenes, Β
    J. Mex. Chem. Soc. 2006, 50(3), 114-118 Article © 2006, Sociedad Química de México ISSN 1870-249X Catalytic Synthesis of 1,3,5-Triphenylbenzenes, β-Methylchalcones and 2,4,6-Triphenyl Pyrylium Salts, Promoted by a Super Acid Triflouromethane Sulfonic Clay from Acetophenones Rosario Ruíz-Guerrero,1 Jorge Cárdenas,1 Lorena Bautista,1 Marina Vargas,1,3 Eloy Vázquez-Labastida2 and Manuel Salmón*1 1 Instituto de Química de la Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán 04510, México D. F. [email protected] 2 Escuela Superior de Ingeniería Química e Industrias Extractivas del Instituto Politécnico Nacional, Edificio 7, Unidad Profesional, Zacatenco, Col. La Escalera, México 07038, D. F. 3 Departamento de Química, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México, México 54740. Dedicated to Professor Pedro Joseph-Nathan on the occasion of his 65th birthday. Recibido el 9 de marzo del 2006; aceptado el 31 de mayo del 2006 Abstract. A montmorillonite clay from the State of Durango, Resumen. Una arcilla de montmorilonita del estado de Durango se Mexico, was used as catalyst. The clay was activated with trifluo- empleó como catalizador. La arcilla fue activada con ácido trifluoro- romethane sulfonic acid and used to study the condensation of differ- metansulfónico y usada para estudiar la condensación de diferentes ent acetophenones in refluxing benzene to produce triphenylben- acetofenonas en benceno a reflujo para producir trifenilbencenos, β- zenes, β-methylchalcones and pyrylium salts. This catalytic proce- metilchalconas y sales de pirilio. Este proceso catalítico produjo un dure afforded a new simple one-step method for the synthesis of com- nuevo método en una sola etapa para la síntesis de moléculas comple- plex organic molecules through the C-C bonds formation and the jas a través de la formación de enlaces C-C con el contraión del ácido counter ion for the pyrylium salt.
    [Show full text]
  • On the Impact of Excited State Antiaromaticity Relief in a Fundamental
    On the Impact of Excited State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes Tomáš Slanina,1,2 Rabia Ayub,1,‡ Josene Toldo,1,‡ Johan Sundell,3 Wangchuk Rabten,1 Marco Nicaso,1 Igor Alabugin,4 Ignacio Fdez. Galván,5 Arvind K. Gupta,1 Roland Lindh,5,6 Andreas Orthaber,1 Richard J. Lewis,7 Gunnar Grönberg,7 Joakim Bergman3,* and Henrik Ottosson1,* 1 Department of Chemistry – Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden. 2 Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo námĕstí 2, 16610 Prague 6, Czech Republic 3 Medicinal Chemistry, Research and Early Development Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden. 4 Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306-4390, USA, 5 Department of Chemistry – BMC, Uppsala University, 751 23, Uppsala, Sweden, 6 Uppsala Center for Computational 7 Chemistry – UC3, Uppsala University, 751 23, Uppsala Sweden, Medicinal Chemistry, Research and Early Development Respiratory, Inflammation and Autoimmune, BioPharmaceutical R&D, AstraZeneca Gothenburg, Sweden. ‡ These authors contributed equally. Table of contents 1. Materials and Methods ..................................................................................................................... 3 1.1 General information .....................................................................................................................
    [Show full text]
  • Versatile Synthetic Methods for Photoluminescent Pyrylium Tosylates Jung Jae Koh University of Nevada, Las Vegas, [email protected]
    UNLV Theses, Dissertations, Professional Papers, and Capstones 8-1-2015 Versatile Synthetic Methods for Photoluminescent Pyrylium Tosylates Jung Jae Koh University of Nevada, Las Vegas, [email protected] Follow this and additional works at: https://digitalscholarship.unlv.edu/thesesdissertations Part of the Chemistry Commons Repository Citation Koh, Jung Jae, "Versatile Synthetic Methods for Photoluminescent Pyrylium Tosylates" (2015). UNLV Theses, Dissertations, Professional Papers, and Capstones. 2487. https://digitalscholarship.unlv.edu/thesesdissertations/2487 This Thesis is brought to you for free and open access by Digital Scholarship@UNLV. It has been accepted for inclusion in UNLV Theses, Dissertations, Professional Papers, and Capstones by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. VERSATILE SYNTHETIC METHODS FOR PHOTOLUMINESCENT PYRYLIUM TOSYLATES by Jung Jae Koh Bachelor of Biochemistry University of Nevada, Las Vegas 2011 A thesis submitted in partial fulfillment of the requirements for the Master of Science - Chemistry Department of Chemistry and Biochemistry College of Science The Graduate College University of Nevada, Las Vegas August 2015 Copyright by Jung Jae Koh, 2015 All Rights Reserved Thesis Approval The Graduate College The University of Nevada, Las Vegas July 21, 2015 This thesis prepared by Jung Jae Koh entitled Versatile Synthetic Methods for Photoluminescent Pyrylium Tosylates is approved in partial fulfillment of the requirements for the degree of Master of Science – Chemistry Department of Chemistry and Biochemistry Pradip K. Bhowmik, Ph.D. Kathryn Hausbeck Korgan, Ph.D. Examination Committee Co-Chair Graduate College Interim Dean Vernon F. Hodge, Ph.D. Examination Committee Co-Chair Dong-Chan Lee, Ph.D.
    [Show full text]
  • Pyrylium Salts with Long Alkyl Substituents, II
    Pyrylium Salts with Long Alkyl Substituents, II [1] 2,4-Dimethyl-6-undecylpyrylium Perchlorate and Derived Pyridinium Salts Mariana Bogatian, Calin Deleanu, Gheorghe Mihai, and Teodor Silviu Balaban* Center of Organic Chemistry of the Roumanian Academy Splaiul Independentei 202 B, 71141 Bucharest, PO 15/258, Roumania Z. Naturforsch. 47b, 1011-1015 (1992); received September 25, 1991/January 10, 1992 Pyrylium Salts, Pyridinium Salts, Synthetic Amphiphiles, NMR Spectra The crystalline title pyrylium salt was obtained by SnCl4 catalysed acylation of mesityl oxide with lauroyl chloride followed by treatment with perchloric acid and column chromatography. This new pyrylium salt was converted in high yields into the corresponding pyridine and N-substituted pyridinium salts (N-methyl, N-phenyl, N-(4-«-butylphenyl), and N-dodecyl) whose proton (300 MHz) and carbon-13 (75 MHz) NMR spectra are presented. Introduction eleven carbon a-alkyl side-chain and pyridinium One long aliphatic (lipophilic) chain attached to salts derived therefrom. strongly polar (hydrophilic) groups leads to com­ pounds with tensioactive properties. These are due either to micelar aggregates or to membranes. Two Results and Discussion long lipophilic chains attached to one polar group The acylation of mesityl oxide (1) was effected lead to amphiphiles, which can form bilayer mem­ with lauroyl chloride of comercial source, by branes [2]. Some such synthetic analogs of bio­ known methods [ 8], When A1C1 3 was used as acy- membranes have been prepared and their catalytic lating catalyst, the yields were low (<5% ) due to activity has been investigated and compared with the poor isolation of the desired title salt 2, while that of phospholipids and lecithins [3].
    [Show full text]
  • Cyclometalation of Phosphinines Via C-H Activation : Towards Functional Coordination Compounds
    Cyclometalation of phosphinines via C-H activation : towards functional coordination compounds Citation for published version (APA): Broeckx, L. E. E. (2013). Cyclometalation of phosphinines via C-H activation : towards functional coordination compounds. Technische Universiteit Eindhoven. https://doi.org/10.6100/IR760622 DOI: 10.6100/IR760622 Document status and date: Published: 04/12/2013 Document Version: Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.
    [Show full text]
  • Synthetic Studies on a Series of Functionalized Pyrylium Salts, 4-Chloro- and 4-Bromophosphinines
    Tetrahedron 74 (2018) 1880e1887 Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet Synthetic studies on a series of functionalized pyrylium salts, 4-chloro- and 4-bromophosphinines * Noriyoshi Nagahora , Hiroshi Tokumaru, Shinpei Ikaga, Takuya Hanada, Kosei Shioji, Kentaro Okuma Department of Chemistry, Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka, 814-0180, Japan article info abstract Article history: A series of new pyrylium salts that bear sulfonate and phosphonate groups were obtained from the Received 23 January 2018 reactions between 2,6-diphenyl-4H-pyran-4-one, sulfonic anhydride, and chlorophosphates, and Received in revised form analyzed spectroscopically. Furthermore, treatment of 2,6-diphenyl-4H-pyran-4-one with phosphoryl 19 February 2018 chloride or bromide afforded the corresponding 4-chloro- and 4-bromopyrylium tetrafluoroborates in Accepted 21 February 2018 good yield. Subsequently, the synthesis of the corresponding 4-chloro- and 4-bromophosphinines was Available online 25 February 2018 accomplished by treating the respective chloro- and bromopyrylium tetrafluoroborates with tris(- trimethylsilyl)phosphine. Keywords: © Pyrylium salt 2018 Elsevier Ltd. All rights reserved. Phosphinine Chlorination Bromination Tris(trimethylsilyl)phosphine 1. Introduction dehydrobromination.5 Thereafter, the synthesis of other 2- bromophosphinines has also been achieved.6 Keglevich and co- Since the pioneering synthesis of 2,4,6-triphenylphosphinine as workers reported the synthesis
    [Show full text]
  • Redalyc.Catalytic Synthesis of 1,3,5-Triphenylbenzenes, B
    Journal of the Mexican Chemical Society ISSN: 1870-249X [email protected] Sociedad Química de México México Ruíz-Guerrero, Rosario; Cárdenas, Jorge; Bautista, Lorena; Vargas, Marina; Vázquez-Labastida, Eloy; Salmón, Manuel Catalytic Synthesis of 1,3,5-Triphenylbenzenes, B-Methylchalcones and 2,4,6-Triphenyl Pyrylium Salts, Promoted by a Super Acid Triflouromethane Sulfonic Clay from Acetophenones Journal of the Mexican Chemical Society, vol. 50, núm. 3, 2006, pp. 114-118 Sociedad Química de México Distrito Federal, México Available in: http://www.redalyc.org/articulo.oa?id=47550310 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative J. Mex. Chem. Soc. 2006, 50(3), 114-118 Article © 2006, Sociedad Química de México ISSN 1870-249X Catalytic Synthesis of 1,3,5-Triphenylbenzenes, β-Methylchalcones and 2,4,6-Triphenyl Pyrylium Salts, Promoted by a Super Acid Triflouromethane Sulfonic Clay from Acetophenones Rosario Ruíz-Guerrero,1 Jorge Cárdenas,1 Lorena Bautista,1 Marina Vargas,1,3 Eloy Vázquez-Labastida2 and Manuel Salmón*1 1 Instituto de Química de la Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán 04510, México D. F. [email protected] 2 Escuela Superior de Ingeniería Química e Industrias Extractivas del Instituto Politécnico Nacional, Edificio 7, Unidad Profesional, Zacatenco, Col. La Escalera, México 07038, D. F. 3 Departamento de Química, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Estado de México, México 54740.
    [Show full text]
  • Oxidación Catalítica De Fenol Empleando Un Subproducto De La Industria Metalmecánica Como Catalizador
    Oxidación Catalítica de Fenol Empleando un Subproducto de la Industria Metalmecánica Como Catalizador Ángela María Salazar Arias Universidad Nacional de Colombia Facultad de Ingeniería y Arquitectura, Departamento de Ingeniería Química Manizales, Colombia 2017 Catalytic Oxidation of Phenol Using a Byproduct of Metalworking Industry as Catalyst Ángela María Salazar Arias Trabajo final de maestría de profundización presentado como requisito parcial para optar al título de: Magister en Ingeniería – Ingeniería Ambiental Directora: Ph.D. Gloria Inés Giraldo Gómez Codirectora: Ph.D. Nancy Rocío Sanabria González Universidad Nacional de Colombia Facultad de Ingeniería y Arquitectura, Departamento de Ingeniería Química Manizales, Colombia 2017 ´´Nuestra recompensa se encuentra en el esfuerzo y no en el resultado. Un esfuerzo total es una victoria completa´´ Mahatma Gandhi Dedico este trabajo a quien ha guiado cada uno de mis pasos, a quien me ha ayudado a encontrarme con mi verdadero ser, a quien a pesar de todas las caídas nunca me ha dejado… al amigo que nunca falla, Dios! A mi MADRE, a mi padre, a mis hermanos, a mis sobrinos y a Lukas, quienes hacen que todo esfuerzo valga la pena y sin quienes nada de esto podría ser posible. A Guadalupe… VI Oxidación Catalítica de Fenol Empleando un Subproducto de la Industria Metalmecánica como Catalizador Agradecimientos Mis más sinceros agradecimientos a mi madre, por haber creído en mí y haberme dado la oportunidad de encontrar mi camino. A mi padre por haberme enseñado a ver el Universo en mis ojos!. A mis hermanos, quienes han inspirado cada uno de mis pasos y siempre me han apoyado y brindado el mejor ejemplo.
    [Show full text]
  • Catalytic Enantioselective Reactions with (Benzo)Pyrylium Salts
    InnovatIve tools In organIc / organometallIc chemIstry CHIMIA 2020, 74, No. 11 857 doi:10.2533/chimia.2020.857 Chimia 74 (2020) 857–865 © S. Joseph, G. Khassenova, O. García Mancheño Catalytic Enantioselective Reactions with (Benzo)Pyrylium Salts Sumi Josepha, Gaukhar Khassenovaa, and Olga García Mancheño* Abstract: The use of (benzo)pyrylium salts as versatile synthetic building blocks has become an attractive plat- form for the preparation of valuable heterocyclic compounds. Besides other numerous direct applications of (benzo)pyryliums, the intrinsic electrophilic nature of these species or the dipole character of the related oxi- dopyrylium derivatives have been exploited towards the development of enantioselective transformations such as nucleophilic dearomatization and cycloaddition reactions. This review aims at providing an overview on the relevant catalytic enantioselective methodologies developed in the past years, which are presented considering the involved metal- and/or organic catalytic system, as well as the type of reaction. Keywords: Enantioselective catalysis · Metal catalysis · O-heterocycles · Organocatalysis · Pyrylium salts Prof. K.A. Jørgensen (University of Aarhus). She next moved to RWTH-Aachen for her postdoctoral research in the group of Prof. C. Bolm (2005–2008), followed by the start of her inde- pendent career at the University of Münster in 2008. In 2013, she was appointed as joint Chemistry Professor at the University of Regensburg and TUM-Campus Straubing, and since 2017 she is Professor for Organic Chemistry at the University of Münster. 1. Introduction (Benzo)pyrylium salts are privileged six-membered aromat- ic heterocycles containing a positively charged oxygen atom.[1] Important naturally occurring examples include the flavylium plant pigments,[2] while synthetic derivatives present fluores- cence[3] and photocatalytic activity,[4] among other properties S.
    [Show full text]