Novel atropisomeric aminophosphine ligands with a bridge across the 5,5′-position of biphenyl for Rh(I)-catalyzed asymmetric hydrogenation

A new type of atropisomeric bisaminophosphine ligands 2 with a bridge across the 5,5′-position of biphenyl has been developed. The axial chirality of this type of ligands can be retained by macro-ring strain produced from 5,5′-linkage of biphenyl even without 6,6′-substituents on biphenyls. The ligand (R)-2a showed high catalytic activities and enantioselectivities (up to 95.3% ee and quantitative yields) for Rh(I)-catalyzed asymmetric hydrogenation of a variety of methyl (Z)-2-acetamido-3-arylacrylates.