Rhodium-Catalyzed Asymmetric Conjugate Additions of Boronic Acids to Enones Using DIPHONANE: A Novel Chiral Bisphosphine Ligand

The synthesis of a novel enantiopure C2-symmetric bisphosphine, DIPHONANE, was accomplished starting from 2,5-norbornadione, utilizing
(R,R)- and/or (S,S)-(2,3-O-di[(phenylamino)carbonyl]tartaric acid for the resolution of an intermediate phosphineoxide. The application of this
ligand in the rhodium-catalyzed asymmetric conjugate addition of boronic acids to cyclic enones provides the 1,4-addition products in good
yields (69−98%) and high ee's (78−95% ee). A byproduct arising from a consecutive 1,4-addition and 1,2-addition was also observed.