DOCSLIB.ORG

Azulene Moiety As Electron Reservoir in Positively Charged Systems; A

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Azulene Moiety As Electron Reservoir in Positively Charged Systems; A S S symmetry Review Review AzuleneAzulene MoietyMoiety asas ElectronElectron ReservoirReservoir inin PositivelyPositively ChargedCharged Systems; A Short SurveySurvey Alexandru C.C. RazusRazus Romanian“C.D. Nenitzescu” Academy, Institute “C.D. Nenitzescu” of Organic Chemistry, Institute of Romanian Organic Chemistry, Academy, 202202 BB Spl.Spl. Independentei,Independentei, P.O. Box 35-108, 060023 Bucharest, Romania;Romania; [email protected]@yahoo.com Abstract: The non-alternant aromatic azulene, an isomer of alternant naphthalene, differs from the latter in peculiar properties. The The large large polarization polarization of the π-electron system over the seven and fivefive rings gives to azuleneazulene electrophileelectrophile property property a a pronounced pronounced tendency tendency to to donate donate electrons electrons to to an an acceptor, accep- tor,substituted substituted at azulene at azulene 1 position. 1 position. This This paper paper presents presents cases cases in whichin which azulene azulene transfers transfers electrons electrons to toa suitablea suitable acceptor acceptor as as methylium methylium ions, ions, positive positive charged charged heteroaromatics heteroaromaticsand and examplesexamples ofof neutral molecules that can accept electrons. The proposed product synthesis was outlined and the expected R+ electron transfer was highlightedhighlighted by analyzing the NMR, UV-Vis spectraspectra andand thethe pKpKR values.values. Keywords: azulene; methylium ion; heteroaromatics; π-electron-electron transfertransfer 1. Introduction The stability stability of of organic organic compounds compounds can can be beincreased increased or lowered or lowered by the by presence the presence of π electronsof π electrons and the and conjugation the conjugation of this of type this of type electron of electron can help can the help stabilization the stabilization of an elec- of antronic electronic system. system. Very briefly Very and briefly as a and general as a generalrule, the rule, stable the aromatic stable aromatic π electronπ electronsystems Citation: Razus,Razus, A.C. A.C. Azulene Azulene systemsneed to needbe coplanar to be coplanar with an with alternating an alternating conjugation conjugation and must and mustfollow follow Huckel’s Huckel’s rule, Moiety as Electron Reservoir in rule,namely namely to contain to contain 4n+2 4n+2π electrons.π electrons. For the For polycyclic the polycyclic aromatic aromatic hydrocarbons, hydrocarbons, the exist- the Positively Charged Systems; A Short Positive Charged Systems; Short existenceence of benzenoid of benzenoid sextets sextets is accepted is accepted as a key as element a key element in the theory in the theoryof aromaticity of aromaticity (Clar’s Survey. SymmetrySymmetry 20212021,, 1313,, x. 526. (Clar’srule) [1]. rule) Thus [1 heptalene]. Thus heptalene (Scheme (Scheme1), the polycyclic1), the polycyclic hydrocarbon hydrocarbon composed composed of two fused of https://doi.org/10.3390/ https://doi.org/10.3390/xxxxx two fused cycloheptatriene rings, despite the alternant conjugation, is an unstable, with a sym13040526 cycloheptatriene rings, despite the alternant conjugation, is an unstable, with a non-planar non-planarhelicity skeleton helicity which skeleton also does which not also satisfy does Huck not satisfyel’s or Huckel’sClar’s rule. or From Clar’s the rule. last From point the of Academic Editor: Anthony Harriman last point of view, pentalene can also be excluded because it has only 4n π electrons. Both Academic Editor: Anthony Harriman view, pentalene can also be excluded because it has only 4n π electrons. Both compounds compounds are rapidly destroyed even at very low temperatures (−78 ◦C to −100 ◦C) [2,3]. Received: 12 March 2021 are rapidly destroyed even at very low temperatures (−78 °C to −100 °C) [2,3]. At the other At the other extreme is found the well-known aromatic planar naphthalene, with alternant Received:Accepted: 1220 MarchMarch 20212021 extreme is found the well-known aromatic planar naphthalene, with alternant conjuga- Accepted:Published: 2024 MarchMarch 20212021 conjugationtion and following and following Clar’s rule. Clar’s rule. Published: 24 March 2021 Publisher’s Note: MDPI stays neu- Publisher’stral with regard Note: MDPIto jurisdictional stays neutral y withclaims regard in published to jurisdictional maps and claims institu- in Pentalene x x publishedtional affiliations. maps and institutional affil- iations. Naphthalene Copyright: © 2021 by the authors. Azulene Heptalene Submitted for possible open access Copyright: © 2021 by the author. publication under the terms and Licensee MDPI, Basel, Switzerland. Scheme 1. Several bicyclic systems with conjugated π electrons. conditions of the Creative Commons Scheme 1. Several bicyclic systems with conjugated π electrons. This article is an open access article Attribution (CC BY) license distributed under the terms and Azulene is naphthalene’s isomer, built from a fusion of cyclopentadiene and cyclo- (http://creativecommons.org/licenses Azulene is naphthalene’s isomer, built from a fusion of cyclopentadiene and cyclo- conditions of the Creative Commons heptatriene rings. Although this planar compound obeys Huckel’s rule, it possesses a /by/4.0/). heptatriene rings. Although this planar compound obeys Huckel’s rule, it possesses a Attribution (CC BY) license (https:// non-alternant aromatic structure and at first glance it lacks aromatic sextet [4,5]. However non-alternant aromatic structure and at first glance it lacks aromatic sextet [4,5]. However creativecommons.org/licenses/by/ when one electron is transferred from the 7-atom ring to the 5-atom ring, the azulene when one electron is transferred from the 7-atom ring to the 5-atom ring, the azulene can 4.0/). can be regarded as the fusion of a 6 π-electron cyclopentadienyl anion and a 6 π-electron Symmetry 2021, 13, x. https://doi.org/10.3390/xxxxx www.mdpi.com/journal/symmetry Symmetry 2021, 13, 526. https://doi.org/10.3390/sym13040526 https://www.mdpi.com/journal/symmetry Symmetry 2021, 13, x FOR PEER REVIEW 2 of 23 Symmetry 2021, 13, x FOR PEER REVIEW 2 of 23 Symmetry 2021 13 , , 526 be regarded as the fusion of a 6 π-electron cyclopentadienyl anion and a 6 π-electron2 of 21 tropylium cation (Scheme 2). The compound polarity is reflected in the presence of the dipolebe regarded moment as (1.08 the fusionD). of a 6 π-electron cyclopentadienyl anion and a 6 π-electron tropyliumtropylium cationcation (Scheme(Scheme2 ).2). The The compound compound polarity polarity is is reflected reflected in in the the presence presence of of the the dipoledipole momentmoment (1.08(1.08 D).D). Scheme 2. Azulene: resonance structures and orbital molecular. Scheme 2. Azulene: resonance structures and orbital molecular. SchemeReactivity 2. Azulene: studies resonance confirm structures also that and the orbital seven-membered molecular. ring is electrophilic and the Reactivity studies confirm also that the seven-membered ring is electrophilic and five-membered ring is nucleophilic. The electron transfer can be made to a positively the five-membered ring is nucleophilic. The electron transfer can be made to a positively chargedReactivity substituent studies (Scheme confirm 3). alsoIn this that case, the seven-memberedthe tropylium ion ring generation is electrophilic provides and good the charged substituent (Scheme3). In this case, the tropylium ion generation provides good stabilityfive-membered to the formed ring is cation nucleophilic. and, implicitly, The electr anon activation transfer ofcan the be electrophilic made to a positivelyreactions stabilitycharged tosubstituent the formed (Scheme cation 3). and, In implicitly,this case, the an tropylium activation ion of the generation electrophilic provides reactions good (Scheme 33).). WhileWhile thethe azuleneazulene moleculemolecule isis symmetricalsymmetrical onlyonly withwith respectrespect toto thethe x-axis, naphthalenestability to the is supplementary formed cation and,symmetrical implicitly, with an respect activation to the of ythe-axis electrophilic (Scheme 1). reactions For this naphthalene(Scheme 3). isWhile supplementary the azulene symmetrical molecule iswith symmetrical respect to only the ywith-axis respect (Scheme to1 ).the For x-axis, this reason, azuleneazulene hashas three three pairs pairs of of identical identical positions positions (1,3; (1,3; 4,8; 4,8; 3,7) 3,7) and and two two distinct distinct positions posi- tionsnaphthalene (2 and 6) is while supplementary naphthalene sy mmetricaltwice has four with identical respect topositions the y-axis (α (Schemeand β). These 1). For posi- this (2reason, and 6) azulene while naphthalene has three pairs twice of hasidentical four identical positions positions (1,3; 4,8; (α3,7)and andβ). two These distinct positions posi- tionshave differenthave different charges, charges, therefore therefore different differe reactivity.nt reactivity. In comparison In comparison with other with benzenoidother ben- zenoidtions (2 hydrocarbons, and 6) while naphthalene the difference tw icebetween has four the identical small highest positions occupied (α and βmolecular). These posi- or- hydrocarbons,tions have different the difference charges, between therefore the differe smallnt highest reactivity. occupied In comparison molecular with orbital–lowest other ben- bital–lowestunoccupied molecularunoccupied orbital molecular (HOMO–LUMO) orbital (HOMO–LUMO) ensures its remarkable ensures its chemical, remarkable electronic chem- ical,zenoid
Load more

Recommended publications
  • The Role of Norrish Type-I Chemistry in Photoactive Drugs: an Ab Initio Study of a Cyclopropenone-Enediyne Drug Precursor
    Leger, S. J., Marchetti, B., Ashfold, M. N. R., & Karsili, T. N. V. (2020). The Role of Norrish Type-I Chemistry in Photoactive Drugs: An ab initio Study of a Cyclopropenone-Enediyne Drug Precursor. Frontiers in Chemistry, 8, [596590]. https://doi.org/10.3389/fchem.2020.596590 Publisher's PDF, also known as Version of record License (if available): CC BY Link to published version (if available): 10.3389/fchem.2020.596590 Link to publication record in Explore Bristol Research PDF-document This is the final published version of the article (version of record). It first appeared online via Fromtiers Media at https://doi.org/10.3389/fchem.2020.596590. Please refer to any applicable terms of use of the publisher. University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/red/research-policy/pure/user-guides/ebr-terms/ ORIGINAL RESEARCH published: 22 December 2020 doi: 10.3389/fchem.2020.596590 The Role of Norrish Type-I Chemistry in Photoactive Drugs: An ab initio Study of a Cyclopropenone-Enediyne Drug Precursor Spencer J. Léger 1,2, Barbara Marchetti 1, Michael N. R. Ashfold 3 and Tolga N. V. Karsili 1* 1 Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA, United States, 2 Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA, United States, 3 School of Chemistry, University of Bristol, Bristol, United Kingdom We present a contemporary mechanistic description of the light-driven conversion of cyclopropenone containing enediyne (CPE) precusors to ring-opened species amenable to further Bergman cyclization and formation of stable biradical species that have been proposed for use in light-induced cancer treatment.
    [Show full text]
  • Chapter 1 Tropone and Tropolone
    School of Molecular and Life Sciences New Routes to Troponoid Natural Products Jason Matthew Wells This thesis is presented for the Degree of Doctor of Philosophy of Curtin University November 2018 Declaration To the best of my knowledge and belief this thesis contains no material previously pub- lished by any other person except where due acknowledgement has been made. This thesis contains no material which has been accepted for the award of any other degree or diploma in any other university. Signature: Date: i Abstract Malaria is an infectious disease found in humans and other animals, it is caused by a single-cell parasite of the Plasmodium genus with many different substrains. Of these, P. falciparum is the most deadly to humans causing the majority of deaths. Although research into the area of antimalarial compounds is wide spread, few have been devel- oped with new structural features. Cordytropolone 37 is a natural product isolated in 2001 from the insect pathogenic fungus Cordyceps sp. BCC 1681 and has been shown to have antimalarial activity against P. falciparum. It has a structure unrelated to antimalarial com- pounds currently used in therapy. It does not contain a peroxide bridge as with artemisinin 25 or quinoline rings as with chloroquine 22. This unique structure indicates that it could possibly interact with the malaria parasite in a fashion unlike current treatments. In order for cordytropolone to be further developed as a potential treatment, it must first be synthe- sised in a laboratory environment. This study attempts to develop the first total synthesis of cordytropolone. H HO O N O O N O N H H H O O Cl HO O 22 25 37 Figure 0.0.1: Cordytropolone 37 has a unique structure compared to the current common malaria treatments The first method investigated towards the total synthesis of cordytropolone involved an intramolecular Buchner ring expansion.
    [Show full text]
  • Possible Gas-Phase Syntheses for Seven Neutral Molecules Studied Recently with the Green Bank Telescope
    A&A 474, 521–527 (2007) Astronomy DOI: 10.1051/0004-6361:20078246 & c ESO 2007 Astrophysics Possible gas-phase syntheses for seven neutral molecules studied recently with the Green Bank Telescope D. Quan1 and E. Herbst2 1 Chemical Physics Program, The Ohio State University, Columbus, Ohio 43210, USA e-mail: [email protected] 2 Departments of Physics, Chemistry and Astronomy, The Ohio State University, Columbus, OH 43210, USA Received 9 July 2007 / Accepted 17 August 2007 ABSTRACT Aims. With the Green Bank telescope (GBT), seven neutral molecules have been newly detected or confirmed towards either the cold interstellar core TMC-1 or the hot core source Sgr B2(N) within the last 1–2 years. Towards TMC-1, the new molecules seen are cyanoallene (CH2CCHCN) and methyl triacetylene (CH3C6H) while methyl cyanoacetylene (CH3CCCN) and methyl cyanodiacety- lene (CH3C5N) were confirmed. Towards Sgr B2(N), the three newly detected molecules are cyclopropenone (c-C3H2O), ketenimine (CH2CNH), and acetamide (CH3CONH2); these are mainly seen in absorption and are primarily located in an envelope around the hot core. In this work, we report a detailed study of the gas-phase chemistry of all seven molecules. Methods. Starting with our updated gas-phase chemical reaction network osu.01.2007, we added formation and depletion reactions to treat the chemistry of each of the seven molecules. Some of these were already in our network but with incomplete chemistry, while most were not in the network at all prior to this work. We assumed the standard physical conditions for TMC-1 and assumed that these also hold for the envelope around Sgr B2(N).
    [Show full text]
  • Mass Spectrometry : Apparatus
    Mass – Spectrometry Mass spectrometry : Apparatus Mass spectrometry :Aparatus MASS Spectrum of acetophenone Fragment Ions Molecular ion (mass ion) MASS Spectrum of Benzamide Mass spectrometry: Processing steps of the sample 1. Ionization of molecules 2. Fragmentation of ionized molecules 3. Acceleration of ions 4. Analysys of the ions Resolution of mass spectrometer 푀 푀푛 10001 푅 = = = = 10000 Δ푀 푀푛−푀푚 10001−10000 M m Mn H ℎ ∗ 100 ≤ 10 % 퐻 Ion sources • 1. Electron ionization (EI) (Electron Impact) • 2. Chemical Ionization (CI) • 3. Fast Atom Bombardment (FAB) • 4. Laser Desorption (LD) • 5. Matrix-Assisted Laser Desorption Ionization (MALDI) • 6. ElectroSpray ionization (ESI) Electron Ionization (EI) – Ionization Chamber Electron Ionization (EI) What is going on physically? Electron Ionization - Energy of electrons Each electron is associated to a wave whose wavelength λ is given by ℎ λ = 푚 υ where m is its mass, v its velocity and h Planck’s constant. Wavelength is 2.7Å for a kinetic energy of 20 eV and 1.4 Å for 70 eV. Number of ions produced as a function of the electron energy. Advantages of EI 1. Reproducible method 2. High Ionization Efficiency 3. All vaporized molecules can be ionized (non polar and insoluble) 4. Molecular structural information (fragmentation) Disadvantages of EI 1. Only +ve ions are formed 2. Sample has to be volatile 3. Limits to 600Da or less MW 4. Extensive fragmentation Chemical Ionization (CI) 1. Sample is injected in atmosfere of gas (methane, izobutane, ammonia). 2. Gas is ionised by EI method. 3. During the collisions of methane ions with molecules of sample, energy is ransfered, as well as protons is transfered.
    [Show full text]
  • Formation Mechanism of C60 Under Nonequilibrium and Irreversible
    This article was downloaded by: [Eiji Osawa] On: 14 May 2012, At: 15:10 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Fullerenes, Nanotubes and Carbon Nanostructures Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lfnn20 Formation Mechanism of C60 under Nonequilibrium and Irreversible Conditions — An Annotation a Eiji Ōsawa a NanoCarbon Research Institute, AREC, Shinshu University, Nagano, Japan Available online: 14 May 2012 To cite this article: Eiji Ōsawa (2012): Formation Mechanism of C60 under Nonequilibrium and Irreversible Conditions — An Annotation, Fullerenes, Nanotubes and Carbon Nanostructures, 20:4-7, 299-309 To link to this article: http://dx.doi.org/10.1080/1536383X.2012.655104 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
    [Show full text]
  • Investigation of Au Sams Photoclick Derivatization by PM-IRRAS Wilson Luoa, Sydney M
    Investigation of Au SAMs Photoclick Derivatization by PM-IRRAS Wilson Luoa, Sydney M. Leggea, Johnny Luob,c, François Lagugné-Labarthet*a, and Mark S. Wor- kentin*a aDepartment of Chemistry and the Centre for Materials and Biomaterials Research, Western University, 1151 Rich- mond Street, London, ON, N6A 5B7, Canada. bDepartment of Biochemistry, Western University, London, Ontario N6A 5C1, Canada. cLawson Health Research Institute, London, Ontario N6C 2R5, Canada. ABSTRACT: In this work we present a clean one-step process for modifying headgroups of self-assembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenone-caged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initi- ated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strain-promoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-mod- ulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Fur- thermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irra- diated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the “photoclick” methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.
    [Show full text]
  • Design, Synthesis and Reactivity of Cyclopropenone
    DESIGN, SYNTHESIS AND REACTIVITY OF CYCLOPROPENONE- CONTAINING NINE MEMBERED CYCLIC ENEDIYNE AND ENYNE-ALLENE PRECURSORS AS PROTOTYPE PHOTOSWITCHABLE ANTITUMOR AGENTS by DINESH R. PANDITHAVIDANA (Under the Direction of Vladimir V. Popik) ABSTRACT The extreme cytotoxicity of natural enediyne antibiotics is attributed to the ability of the ( Z)-3-hexene-1,5-diyne (enediyne) and ( Z)-1,2,4-heptatrien-6-yne (enyne–allene) fragments incorporated into a 10- or 9-membered ring cyclic system to undergo cycloaromatization producing dDNA-damaging 1,4-diradicals. The rate of cyclization of enediynes to p-benzynes strongly depends on the distance between acetylenic termini, which in turn can be controlled by the ring size. Thus, 11-membered ring enediynes are stable, 10-membered ring analogs undergo slow cycloaromatization under ambient conditions or mild heating, 9- membered ring enediynes are virtually unknown and believed to undergo very fast spontaneous cyclization. Cyclic enyne-allenes have not been synthesized so far due to very facile Myers-Saito cyclization. We have developed thermally stable photo-precursors of 9-membered enediynes ( 2.22 , 2.26 ) and enyne-allene ( 2.44 ), in which one of the triple bonds is replaced by the cyclopropenone group. UV irradiation of 2.14 results in the efficient decarbonylation (Φ 254 = 0.34) and the formation of reactive enediyne 2.22. The latter undergoes clean cycloaromatization to 2,3-dihydro-1H- cyclopenta[b]naphthalen-1-ol ( 2.24 ) with a life-time of ca. 2 h in 2-propanol at 25 °C. The rate of this reaction depends linearly on the concentration of hydrogen donor and shows a primary kinetic isotope effect in 2-propanol-d8.
    [Show full text]
  • Sc-Homoaromaticity
    This is a repository copy of Modern Valence-Bond Description of Homoaromaticity. White Rose Research Online URL for this paper: https://eprints.whiterose.ac.uk/106288/ Version: Accepted Version Article: Karadakov, Peter Borislavov orcid.org/0000-0002-2673-6804 and Cooper, David L. (2016) Modern Valence-Bond Description of Homoaromaticity. Journal of Physical Chemistry A. pp. 8769-8779. ISSN 1089-5639 https://doi.org/10.1021/acs.jpca.6b09426 Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ Modern Valence-Bond Description of Homoaromaticity Peter B. Karadakov; and David L. Cooper; Department of Chemistry, University of York, Heslington, York, YO10 5DD, U.K. Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, U.K. Abstract Spin-coupled (SC) theory is used to obtain modern valence-bond (VB) descriptions of the electronic structures of local minimum and transition state geometries of three species that have been con- C sidered to exhibit homoconjugation and homoaromaticity: the homotropenylium ion, C8H9 , the C cycloheptatriene neutral ring, C7H8, and the 1,3-bishomotropenylium ion, C9H11.
    [Show full text]
  • Non-Empirical Calculations on the Electronic Structure of Olefins and Aromatics
    NON-EMPIRICAL CALCULATIONS ON THE ELECTRONIC STRUCTURE OF OLEFINS AND AROMATICS by Robert H. Findlay, B.Sc. Thesis presented for the Degree of Doctor of philosophy University of Edinburgh December 1973 U N /),, cb CIV 3 ACKNOWLEDGEMENTS I Wish to express my gratitude to Dr. M.H. Palmer for his advice and encouragement during this period of study. I should also like to thank Professor J.I.G. Cadogan and Professor N. Campbell for the provision of facilities, and the Carnegie Institute for the Universities of Scotland for a Research Scholarship. SUMMARY Non-empirical, self-consistent field, molecular orbital calculations, with the atomic orbitals represented by linear combinations of Gaussian-type functions have been carried out on the ground state electronic structures of some nitrogen-, oxygen-, sulphur- and phosphorus-containing heterocycles. Some olefins and olefin derivatives have also been studied. Calculated values of properties have been compared with the appropriate experimental quantities, and in most cases the agreement is good, with linear relationships being established; these are found to have very small standard deviations. Extensions to molecules for which there is no experimental data have been made. In many cases it has been iôtrnd possible to relate the molecular orbitals to the simplest member of a series, or to the hydrocarbon analogue. Predictions of the preferred geometry of selected molecules have been made; these have been used to predict inversion barriers and reaction mechanisms. / / The extent of d-orbital participation in molecules containing second row atoms has been investigated and found to be of trivial importance except in molecules containing high valence states of the second row atoms.
    [Show full text]
  • CH Functionalization Via Iron-Catalyzed Carbene
    molecules Review C-H Functionalization via Iron-Catalyzed Carbene-Transfer Reactions Claire Empel, Sripati Jana and Rene M. Koenigs * Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52074 Aachen, Germany; [email protected] (C.E.); [email protected] (S.J.) * Correspondence: [email protected] Academic Editor: Hans-Joachim Knölker Received: 4 January 2020; Accepted: 5 February 2020; Published: 17 February 2020 Abstract: The direct C-H functionalization reaction is one of the most efficient strategies by which to introduce new functional groups into small organic molecules. Over time, iron complexes have emerged as versatile catalysts for carbine-transfer reactions with diazoalkanes under mild and sustainable reaction conditions. In this review, we discuss the advances that have been made using iron catalysts to perform C-H functionalization reactions with diazoalkanes. We give an overview of early examples employing stoichiometric iron carbene complexes and continue with recent advances in the C-H functionalization of C(sp2)-H and C(sp3)-H bonds, concluding with the latest developments in enzymatic C-H functionalization reactions using iron-heme-containing enzymes. Keywords: iron; carbene; diazoalkane; C-H functionalization 1. Introduction C-H bonds belong to the most common motifs in organic molecules and their direct functionalization is one of the main challenges in synthesis methodology, which impacts on the step economy and sustainability of chemical processes. In recent decades, this research area has flourished and different approaches have been realized to enable C-H functionalization reactions via different strategies: (a) by the directing group-assisted C-H activation, (b) via the innate reactivity of organic molecules, or (c) via direct C-H functionalization (Scheme1)[ 1–4].
    [Show full text]
  • From Acetic Acid Mp 16142 "C; IR 2630 Cm-' (Brd, OH); 'H NMR 11.22 (Brd S
    4440 J. Org. Chem., Vol. 44, No. 24, 1979 Notes from acetic acid mp 16142 "C; IR 2630 cm-' (brd, OH); 'H NMR Chart I 11.22 (brd s, 1 H, OH),7.72 (m, 2 H) and 7.47 (m, 3 H) (C6H5), 2.10 (5, 3 H, CH3). Anal. Calcd for Cloll,N20Cl: C, 57.57; H, 4.35; N, 13.42; C1, 16.99. Found: C, 57.84; H, 4.43; N, 13.26; C1, 17.02. Vilsmeier Reaction of la. Reaction of la under the conditions above gave, from the ether extract, 27% of 4a, mp 210-11 "C," which was identical with a sample prepared by chlorination of 1 2 3 3,5-diphenylpyrazole with S02C12.5 A = 5.80 A = 3.90 A = 5.34 Neutralization of the basic aqueous solution gave 48% of 3a: mp 191-93 "C (from acetic acid); IR 2650 cm-' (brd, OH), 'H NMR 8.50 (brd, 1 H, OH), 7.15-7.60 (m, 10 H, C6H5). Anal. Calcd for Cl!jH11N20C1: C, 66.55; H, 4.10; N, 10.35. Found: C, 66.67; H, 3.84; N, 10.28. Vilsmeier Reaction of 2b. A solution of 1.7 g (11 mmol) of POCl, in 10 mL of DMF was cooled below 10 "C and treated with 1.74 g (10 mmol) of 2bl. The solution was stirred at room tem- 4 5 perature for 150 min, poured into 100 mL of ice-water, and A = 4.67 A = 3.20 neutralized with NaHC03. The solid was collected, washed with water, and dried to give 1.49 g (77%) of 4b.
    [Show full text]
  • Aspects of Reductive Methods in Organophosphorus Chemistry
    Aspects of Reductive Methods in Organophosphorus Chemistry A Thesis presented to the Faculty of Science of the University of New South Wales in fulfilment for the Degree of Doctor of Philosophy by Neil Donoghue B.Sc. (Hons.), University of Adelaide Department of Organic Chemistry School of Chemistry University of New South Wales May 1998 ii Abstract. This study is concerned with the reductive cleavage of tetracoordinated organophos- + – phorus compounds (either quaternary phosphonium salts R4P X or tertiary phosphine oxides R3P O) with either the naphthalene radical (naphthalenide) anion or lithium aluminium hy- dride in THF solution at room temperature (RT). Part 1 examines the reaction of lithium naphthalenide with both phosphonium salts and phosphine oxides. The reaction was dem- onstrated to cleave phenyl groups from both bis-salts and bis-oxides in the presence of 1,2- ethylene bridges; based upon this, parallel syntheses of either 1,4-diphosphabicyclo[2.2.2]oc- tane or its P,P'-dioxide were attempted by using the commercially available ethane-1,2-bis- (diphenylphosphine) as the starting material in each case. Examination of the products of + – reductive cleavage of the series of benzylphenylphosphonium bromide [PhnP(CH2Ph)4-n] Br (where n = 0 to 3) with lithium naphthalenide leads to the proposal of a mechanism. Part 2 describes hydridic reductions of both quaternary phosphonium salts and ter- tiary phosphine oxides. Examination of the lithium aluminium hydride reduction of qua- 31 ternary phosphonium salts using P-NMR has confirmed tetraorganophosphoranes (R4PH; R = Ph, alkyl) as intermediates in the reaction; in addition, two previously unknown classes – of compounds, the triorganophosphoranes R3PH2 and the tetraorganophosphoranates R4PH2 , were also found to be intermediates.
    [Show full text]