Transition-metal-catalyzed carbenoid reactions of sulfonium ylides

Olefins undergo cyclopropanation with diphenylsulfonium (ethoxycarbonyl)met hylide (= diphenylsulfonium 2-ethoxy-2-oxoethylide; 3a) in the presence of chiral Cu-I or Rh-II catalysts, trans/cis Ratios and ee's of the cyclopropa nes 6 obtained with this ylide in the presence of a chiral Cu-I catalyst 7 are identical with those obtained with ethyl diazoacetate (4). In the case of catalysis with Rh-II, the trans/cis ratios of the cyclopropanes as well as the enantioselectivity change slightly upon going from the ylide 3a to d iazoacetate 4.