Chiral Bifunctional Phosphine-Carboxylate Ligands for Palladium(0)-Catalyzed Enantioselective C-H Arylation

Previous enantioselective Pd-0-catalyzed C-H activation reactions proceeding via the concerted metalation-deprotonation mechanism employed either a chiral ancillary ligand, a chiral base, or a bimolecular mixture thereof. This study describes the development of new chiral bifunctional ligands based on a binaphthyl scaffold which incorporates both a phosphine and a carboxylic acid moiety. The optimal ligand provided high yields and enantioselectivities for a desymmetrizing C(sp(2))-H arylation leading to 5,6-dihydrophenanthridines, whereas the corresponding monofunctional ligands showed low enantioselectivities. The bifunctional system proved applicable to a range of substituted dihydrophenanthridines, and allowed the parallel kinetic resolution of racemic substrates.