ASYMMETRIC REACTIONS CATALYZED BY CHIRAL METAL-COMPLEXES .59. PREPARATIONS OF CHIRAL PYRROLIDINEBISPHOSPHINES BEARING 2 DIFFERENT TYPES OF PHOSPHINO GROUPS AND THEIR USE IN EFFICIENT CATALYTIC ASYMMETRIC HYDROGENATION

Chiral pyrrolidinebisphosphine ligands, (2S-cis)-BCPM and (2S-cis)-BCP P, bearing two different types of phosphino groups, a dicyclohexylphos phino group and a diphenylphosphino group, were designed and prepared on the basis of our design concept for developing highly efficient lig ands. 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/cata lyst > ca. 10(4), > 90% ee (R)).