An Atropos Chiral Biphenyl Bisphosphine Ligand Bearing Only 2,2′-Substituents and Its Application in Rh-Catalyzed Asymmetric Hydrogenation

An atropos chiral biphenyl bisphosphine ligand bearing only 2,2′-substituents was rationally designed and easily synthesized utilizing a bulky chiral t-butylmethylphosphino block. Computational results showed a large difference in the free energies between the two diastereomers (7.8 kcal/mol) and attainable rotational energy barriers from one diastereomer to another (27.7 kcal/mol and reverse 19.9 kcal/mol). This ligand avoids the time-consuming optical resolution generally needed for the preparation of axially chiral ligands and shows high reactivity and enantioselectivity in Rh-catalyzed asymmetric hydrogenations. (Figure presented.).