Synthesis of Novel Diastereomeric Diphosphine Ligands and Their Applications in Asymmetric Hydrogenation Reactions

Diastereomeric biaryl diphosphine ligands 10 and 11 with added chiral centers on the backbone were synthesized. Substrate-directed asymmetric synthesis occurred in the coupling step of the preparation of the diastereomeric diphosphine oxides. The diastereomeric diphosphine oxides were easily separated by column chromatography with silica gel. Ruthenium catalysts containing these ligands were highly effective in the hydrogenation of 2-(6‘-methoxy-2‘-naphthyl)propenoic acid and β-ketoesters. The additional chiral centers had a significant influence on the enantioselectivity and activity of the catalysts.