| Abstract: | Olefins undergo cyclopropanation with diphenylsulfonium (ethoxycarbonyl)methylide (=diphenylsulfonium 2-ethoxy-2-oxoethylide; 3a ) in the presence of chiral CuI or RhII catalysts. trans/cis Ratios and ee's of the cyclopropanes 6 obtained with this ylide in the presence of a chiral CuI catalyst 7 are identical with those obtained with ethyl diazoacetate ( 4 ). In the case of catalysis with RhII, the trans/cis ratios of the cyclopropanes as well as the enantioselectivity change slightly upon going from the ylide 3a to diazoacetate 4 . |
