Enantioselective Tandem Michael Addition/H₂-Hydrogenation Catalyzed by Ruthenium Hydride Borohydride Complexes Containing β-aminophosphine Ligands

A variety of ruthenium(II) catalyst precursors containing β-aminophosphine ligands and a borohydride ligand were found to be active for a one-pot, tandem asymmetric Michael addition/H₂-hydrogenation reaction to give the chiral alcohol in excellent diastereomeric excess. The most effective catalyst is 4b, containing the (S)-binap ligand and (R,R)-Pnor ligand, derived from (1S,2R)-norephedrine.