Dihydrophenanthridine: A New and Easily Regenerable NAD(P)H Model for Biomimetic Asymmetric Hydrogenation

A new and easily regenerable NAD(P)H model 9,10-dihydrophenanthridine (DHPD) has been designed for biomimetic asymmetric hydrogenation of imines and aromatic compounds. This reaction features the use of hydrogen gas as terminal reductant for the regeneration of the DHPD under the mild condition. Therefore, the substrate scope is not limited in benzoxazinones; the biomimetic asymmetric hydrogenation of benzoxazines, quinoxalines, and quinolines also gives excellent activities and enantioselectivities. Meanwhile, an unexpected reversal of enantioselectivity was observed between the reactions promoted by the different NAD(P)H models, which is ascribed to the different hydride transfer pathway.