Asymmetric Hydrogenation of Ketones Catalyzed by Ruthenium Hydride Complexes of a Beta-aminophosphine Ligand Derived from Norephedrine

A series ruthenium complexes with the chiral P−N ligand (1 R, 2 R )-PPh 2 CHPhCHMeNH 2 derived from (1 S, 2 R )-norephedrine are synthesized starting from the complexes RuHCl(PPh 3 ) 3 or RuHCl(P−P)(PPh 3 ) (P−P= ( R )-binap or ( S )-binap). These are precatalysts for the efficient asymmetric hydrogenation of simple ketones. For the hydrogenation of acetophenone to 1-phenylethanol, the enantioselectivity observed can be related to the structure of the precatalysts determined by X-ray diffraction. This relationship breaks down for the hydrogenation of pinacolone.