Treatment of trimethylsilylethanes bearing alpha a-phenyl groups and beta-phenylthio, phenylsulfonyl or cyano groups with LDA causes elimination-rearrangement mediated by the beta-carbanionic species. Mechanistic conclusions are based on isotopic labelling experiments, the effects of substituents and approximate kinetics. These suggest that trimethylsilyl is the migrating group, that cleavage of the bond to the leaving group is little advanced in the transition structure and that placing of a substituent to encourage Si-C bond cleavage is mandatory.
The Thermal Decomposition of Mercaptans
作者:A. H. Sehon、B. deB. Darwent
DOI:10.1021/ja01648a011
日期:1954.10
Studies on the Mechanism of Action of Prekinamycin, a Member of the Diazoparaquinone Family of Natural Products: Evidence for Both sp<sup>2</sup> Radical and Orthoquinonemethide Intermediates
作者:Ken S. Feldman、Kyle J. Eastman
DOI:10.1021/ja0642616
日期:2006.9.1
The putative reductive activation chemistry of the diazoparaquinone antibiotics was modeled with Bu3Sn-H and prekinamycin dimethyl ether along with prekinamycin itself. Reaction in various combinations of aromatic solvents, with and without the nucleophile benzylmercaptan present, led to isolation of both radical-trapping arene adducts and nucleophilic capture benzyl thioether products. On the basis of these product distribution studies, the intermediacies of, first, a cyclopentenyl radical and, next, an orthoquinonemethide electrophile are postulated.