Asymmetric cyclopropanation of (5S,S S)-3-p-tolylsulfinyl-5- ethoxyfuran-2(5H)-one with sulfonium ylides: Influence of the sulfur ylide substituents on stereoselectivity

Abstract

The cyclopropanation of title compound 1 with various sulfur ylides has been examined. A very high π-facial selectivity was observed in the reaction with diphenylsulfonium ylides, Ph 2S=CRR′ (anti attack with respect to the alkoxy group in 1 is clearly preferred) whereas the endo-selectivity was found when R ≠ R′ is dependent on their relative size. Reactions with dimethylsulfonium ylides Me 2S=CRR′ occurred with a moderate π-facial selectivity and exo-selectivity, the former being dependent on the solvent polarity. The stereochemical course of the cyclopropanation reactions is rationalized in terms of steric and electrostatic interactions. © 2004 Elsevier Ltd. All rights reserved.