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 (1R,2R)-PPh2CHPhCHMeNH2
derived from (1S,2R)-norephedrine are synthesized starting from the complexes RuHCl(PPh3)3 or RuHCl(P−P)(PPh3) (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.