Generation and intramolecular cyclization of α-sulfinyl and α-sulfonyl radicals
摘要:
alpha-Phenylsulfinyl and alpha-Phenylsulfonyl radicals are generated by the reactions of alpha-chlorosulfoxides and alpha-chlorosulfones with tributyltin hydride, respectively. High reaction concentration (0.2 M) is required to ensure efficient generations of these radicals. The 5-exo-type intramolecular cyclizations of these radicals are studied. The cyclization is most successful when the olefin is terminally substituted with an ester group. The sulfinyl group only induces mild diastereoselectivity on the cyclization. (C) 1997 Elsevier Science Ltd.
Various α-sulfonylcarbanions have been shown to react at low temperature with di- or tri-halogenolithiocarbenoïds, to give 1-mono- or 1,1-di-halogenoalkenes. Bromocarbenoïds gave better results than their chloro-analogues. Reaction of di-bromolithiomethane with α-lithiated sulfones gives a high yield of vinylic bromides, the stereochemistry of which is cleanly E. Evidence is presented that the carbenoïd
The study of intramolecular free radical cyclizations of α-sulfonyl and α-sulfinyl radicals
作者:Tsai Yeun-Min、Ke Bor-Wen、Lin Chao-Hsiung
DOI:10.1016/s0040-4039(00)98025-0
日期:1990.1
α-Sulfonyl and α-sulfinyl radicals can be generated from the corresponding α-halosulfones and αhalosulfoxides. Our results indicate that these radicalscyclize very efficiently.