Catalytic asymmetric epoxidation of alpha,beta-unsaturated phosphane oxides with a Y(O-iPr)3/biphenyldiol complex

A rare-earth-metal-catalyzed asymmetric epoxidation of alpha,beta-unsaturated phosphane oxides is described. The appropriate selection of a chiral ligand and an achiral additive is important for achieving good reactivity and enantioselectivity. A Y(O-iPr)(3)/biphenyldiol complex with an achiral phosphane oxide additive afforded beta-aryl alpha,beta-epoxy phosphane oxides in 77-99 % yield and with 96-98 % ee. With beta-alkyl substrates, the reaction proceeded smoothly in the absence of an achiral additive, and beta-alkyl alpha,beta-epoxy phosphane oxides were obtained in 94-99 % yield and with 87-95 % ee.