Stereoselective cyclopropyl phosphonate formation using (S)-dimethylsulfonium-(p-tolylsulfinyl)methylide. Unusual phosphoryl group migration

Methylation of t-butyl-1-dimethylphosphono-2-p-tolylsulfinyl cyclopropanecarboxylic ester occurs with full inversion of the configuration, but the stereochemistry of carbanion formation is structure-dependent. Reaction of cyclopropyl sulfoxide with i-PrMgCl leads to unprecedented 1,2 migration of the phosphoryl group.