Asymmetric Reactions Catalyzed by Chiral Metal Complex. LIX. Preparations of Chiral Pyrrolidinebisphosphines Bearing Two Different Types of Phosphino Groups and Their Use in Efficient Catalytic Asymmetric Hydrogenation.

Abstract

Chiral pyrrolidinebisphosphine ligands, (2S-cis)-BCPM and (2S-cis)-BCPP, bearing two different types of phosphino groups, a dicyclohexylphosphino group and a diphenylphosphino groups, were designed and prepared on the basis of our design concept for developing highly efficient ligands. The validity of the concept was confirmed experimentally in the asymmetric hydrogenation of ketopantolactone using neutral rhodium(I) complexes of BCPM, BCPP, BPPM, and BCCP. The rhodium(I) complex of (2S-cis)-BCPM was found to be the most effective catalyst (substrate/catalyst >ca. 104, >90%ee (R)).