Development of New 6-Membered Chelating Chiral Bisphosphine Ligands for Rhodium-Catalyzed Asymmetric Hydrogenation

A new chiral 1, 3-bisphosphine, (1R, 2R)-1-diphenylphosphino-2-(diphenylphosphinomethyl)cyclopentane, which was designed to form the favorable skew conformation of the six-membered chelate with rhodium, was developed. Its rhodium complex was found to be one of the most efficient catalysts known for asymmetric hydrogenation of amino acid precursors. Further improvement of this ligand was also attempted for catalytic asymmetric hydrogenation of prochiral ketones to clarify the enantioselective mechanism.