Synthesis of New Atropisomeric Bisphosphine Ligands Bearing Chiral Phospholane and Their Use in Asymmetric Hydrogenation

Novel chiral bisphosphine ligands bearing (2S, 5S)-dimethylphospholano group on a chiral biphenyl back-bone were designed and prepared. Asymmetric hydrogenations of a ketone and an olefin with the rhodium(I) complex catalysts prepared in situ from [Rh(COD)Cl]2 and (R)-2, 2'-bis[(2"S, 5"S)-2", 5"-dimethylphospholano]-5, 5'-dimethoxy-4, 4', 6, 6'-tetramethyl-1, 1'-biphenyl and (S)-2, 2'-bis[(2"S, 5S")-2", 5"-dimethylphospholano]-5, 5'-dimethoxy-4, 4', 6, 6'-tetramethyl-1, 1'-biphenyl gave the corresponding alcohol and alkane in high yields. The asymmetric hydrogenations with these ligands showed a different enantioselectivity.