Highly Enantioselective Synthesis of Chiral γ-Lactams by Rh-Catalyzed Asymmetric Hydrogenation

A Rh/bisphosphine-thiourea (ZhaoPhos) catalytic system has been identified for the straightforward asymmetric synthesis of chiral γ-lactams. A variety of NH free α,β-unsaturated lactams bearing a β-aryl or β-alkyl substituent were smoothly hydrogenated to provide the desired γ-lactams in up to 99% yield and 99% enantiomeric excess (ee). This methodology provides a highly practical pathway to synthesize chiral γ-lactams or γ-amino acids.