|
Arynes or benzynes are highly reactive species derived from an aromatic ring by removal of two ortho substituents.〔Gilchrist T.C.; Rees C.W.; (1969) ''Carbenes, Nitrenes and Arynes'' Nelson. London.〕〔''The Benzyne and Related Intermediates''. H. Heaney Chem. Rev., 1962, 62 (2), pp 81–97 〕 Arynes are usually best described as having a strained triple bond; however, they possess some biradical character as well. The term aryne is most closely associated with ''ortho''-aryne, however ''para''- and ''meta''-aryne intermediates have been described. Benzyne was first postulated by Georg Wittig in 1940〔Wittig, G., Pieper, G. and Fuhrmann, G. (1940), Über die Bildung von Diphenyl aus Fluorbenzol und Phenyl-lithium (IV. Mitteil. über Austauschreaktionen mit Phenyl-lithium). Berichte der deutschen chemischen Gesellschaft (A and B Series), 73: 1193–1197. 〕〔''Phenyl-lithium, der Schlüssel zu einer neuen Chemie metallorganischer Verbindungen'' Georg Wittig Naturwissenschaften, 1942, Volume 30, Numbers 46-47, Pages 696-703 〕〔Wittig, G. (1954), Fortschritte auf dem Gebiet der organischen Aniono-Chemie. Angewandte Chemie, 66: 10–17. 〕 and experimentally confirmed by John D. Roberts in 1953.〔''rearrangement in the reaction of chlorobenzene-1-C14 with potassium amid'' John D. Roberts, Howard E. Simmons Jr., L. A. Carlsmith, C. Wheaton Vaughan J. Am. Chem. Soc., 1953, 75 (13), pp 3290–3291 〕〔''The Mechanism of Aminations of Halobenzenes'' John D. Roberts, Dorothy A. Semenow, Howard E. Simmons Jr., L. A. Carlsmith J. Am. Chem. Soc., 1956, 78 (3), pp 601–611 〕〔''Orientation in Aminations of Substituted Halobenzenes'' John D. Roberts, C. Wheaton Vaughan, L. A. Carlsmith, Dorothy A. Semenow J. Am. Chem. Soc., 1956, 78 (3), pp 611–614 〕〔''Modern Arylation Methods''. Edited by Lutz Ackermann 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN 978-3-527-31937-4〕〔''The Benzyne and Related Intermediates''. H. Heaney Chem. Rev., 1962, 62 (2), pp 81–97 〕 The discovery of benzyne led to rapid developments in synthetic methodologies to make this highly reactive intermediate useful for organic synthesis. To date, a variety of natural products have been prepared using arynes as intermediates.〔Tadross, P. M.; Stoltz, B. M. A Comprehensive History of Arynes in Natural Product Total Synthesis''Chem. Rev.'' 2012, ''112'', 3550〕 Examples of such natural products are Cryptaustoline, (+)-Liphagal, Dehydroaltenuene B, Herbindole A, Taxodione, Melleine and many others. Perhaps one of the most famous reactions of arynes is Bergman cyclization, which lies in the core of mechanism of action of enediyne cytostatics. == Discovery of benzyne == The very first hint of the existence of aryne intermediate came from the work of Stoermer and Kahlert in 1902. They observed that upon treatment of 3-bromobenzofuran with base in ethanol 2-ethoxybenzofuran is formed. Based on this observation they postulated an aryne intermediate. 40 years later an experiment that strongly suggested the existence of benzyne was reported by Georg Wittig. Wittig and coworkers were studying the formation of biphenyl via reactions of fluorobenzene and phenyllithium. They proposed that the reaction proceeded via a zwitterionic intermediate.〔 In 1953 John D. Roberts performed the classic 14C labeling experiment, which provided strong support for benzyne.〔 Roberts and his students performed the reaction of chlorobenzene-1-14C with potassium amide, and analyzed the 14C-label incorporation into the resulting aniline: equal amounts of aniline with 14C incorporation at C-1 and C-2 were observed. This result necessitated a symmetrical intermediate – now known as benzyne. Soon after Roberts’ discovery, Wittig and Pohmer found that benzyne can participate in () cycloaddition reactions.〔Wittig, G.; Pohmer, L. ''Angew. Chem''. 1955, ''67(13)'', 348.〕 Additional evidence for the existence of benzyne came from spectroscopic studies: IR,〔Radziszewski, J. G.; Hess, Jr. B. A.; Zahradnik, R. ''J. Am. Chem. Soc.'' 1992, ''114'', 52.〕 UV/Vis,〔Wenthold, P. G.; Squires, R. R.; Lineberger, W. C. ''J. Am. Chem. Soc.'' 1998, ''120'', 5279〕 microwave,〔Kukolich, S. G.; Tanjaroon,C.; McCarthy, M. C.; Thaddeus, P. ''J. Chem. Phys.'' 2003, ''119'', 4353〕 and NMR spectroscopies.〔Orendt, A. M.; Facelli, J. C.; Radziszewski, J. G.; Horton, W. J.; Grant, D. M.; Michl, J. ''J. Am. Chem. Soc.'' 1996, ''118'', 846〕,.〔Warmuth,R. ''Angew. Chem., Int. Ed. Engl.'' 1997, ''36,'' 1347〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「aryne」の詳細全文を読む スポンサード リンク
|