C,C-COUPLING WITH SULFUR-STABILIZED CARBANIONS .7. DIASTEREOSELECTIVITY IN THE ADDITION OF ELECTROPHILES TO THE CARBANIONS OF 2-(ALKYLTHIO)THIOLANE 1-OXIDES

摘要

Pure diastereoisomers of the 2-(alkylthio)thiolane 1-oxides 2 were prepared in a three-step synthesis. The carbanions of 2 were generated with different bases and treated with iodomethane and carbonyl compounds to form the methyl derivatives 6 and the carbinols 7, respectively. The conformational stability (alpha-diastereoselectivity) of the carbanions as well as the asymmetric induction during the reaction with prochiral electrophiles (beta-diastereoselectivity) was studied. A mechanism for the reaction with carbonyl compounds is proposed, which involves a six-membered cyclic transition state formed from the sulfoxide moiety and the metal cation, - Steric effects of the substrate and the electrophile are discussed. (C) 1997, Elsevier Science Ltd. [References: 34]