Nucleophilic Substitution Reaction of Optically Pure Chloroselenurane with Active Methylene Compounds. Formation of Optically Pure Selenonium Ylides

Nucleophilic substitution reaction of (RSe)-chloroselenurane 1 with active methylene compounds proceeded in highly stereoselective manner with retention of configuration to give (SSe)-selenonium ylides 2. (SSe)- and (RSe)-Ylides, 2 and 3, were stereospecifically formed from the reaction of (RSe)- and (SSe)-selenoxides, 4 and 5, with active methylene compounds.