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Current Organic Chemistry

Editor-in-Chief

ISSN (Print): 1385-2728
ISSN (Online): 1875-5348

Cumulene Rearrangements: Ketene-Ketene, Isocyanate-Isocyanate, Thioketene-Ketene, Imidoylketene-Ketenimine, and Ketene-Allene Rearrangements

Author(s): Curt Wentrup, Justin J. Finnerty and Rainer Koch

Volume 14, Issue 15, 2010

Page: [1586 - 1599] Pages: 14

DOI: 10.2174/138527210793563279

Price: $65

Abstract

Interconversions between α-oxoketenes, imidoylketenes and α-oxoketenimines, thioacylketenes and acylthioketenes, vinylketenes and acylallenes, isocyanates, and thioacylisocyanates and acylisothiocyanates take place by means of 1,3-shifts of substituents, which are facilitated by electron-rich migrating groups, especially those containing lone pairs on the migrating atoms. A bonding interaction between the lone pair orbital and the LUMO of the cumulene moiety stabilizes the transition state and can even make it become an intermediate. The 1,3-shifts can also be said to be pseudopericyclic reactions. The 1,3-migration of aryl groups is accelerated by electron- donating substituents in the phenyl ring. In general, for like substituents, migratory aptitudes decrease in the series α-oxoketene > imidoylketenes > acylallene > vinylketene.

Keywords: Allene, isocyanate, ketene, ketenimine, thioketene, Imidoylketene-Ketenimine, Ketene-Allene Rearrangements, FVT, IR spectroscopy, Meldrum's acid, 13C NMR spectroscopy, LUMO


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