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
Generation and intramolecular cyclization of α-phenylsulfenyl and α-alkylsulfenyl radicals
作者:Yeun-Min Tsai、Fu-Chang Chang、Jimin Huang、Chi-Lung Shiu、Chai-Lin Kao、Jyh-Shiunn Liu
DOI:10.1016/s0040-4020(97)00156-7
日期:1997.3
alpha-Phenylsulfenyl radicals are generated by the reaction of diphenyl dithioacetals or phenyl alpha-chlorosulfides with tributyltin hydride. Alkyl phenyl dithioacetals react selectively with tributyltin hydride to give alpha-alkylsulfenyl radicals. 5-Exo-type of intramolecular cyclizations of these radicals are studied. The cyclization is most successful when the olefin is terminally substituted with an ester group. The cis/trans ratio of the cyclized product varies according to the reaction rates. With a faster cyclization, cis-isomer is the major product. A slower cyclization gives more trans-product. (C) 1997 Elsevier Science Ltd.
Generation and intramolecular cyclization of α-sulfinyl and α-sulfonyl radicals
作者:Bor-Wen Ke、Chao-Hsiung Lin、Yeun-Min Tsai
DOI:10.1016/s0040-4020(97)00472-9
日期:1997.6
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.
The Stereochemistry of the Nucleophilic Addition of p-Toluenethiol to 1-p-Tolylsulfonylcyclopentene<sup>1</sup>