Chiral phosphine-phosphoramidite ligands for highly enantioselective hydrogenation of N-arylimines

The asymmetric hydrogenation of N-arylimines with the chiral phosphine-phosphoramidite ligand, (S-c, S-a)-PEAPhos 2b, has been developed. The results revealed that the presence of the substituents on the 3,3'-positions of the binaphthyl backbone significantly improved the enantioselectivity. The utility of this methodology was demonstrated in the synthesis of the chiral fungicide (R)-metalaxyl.