Manganese-Catalyzed Asymmetric Hydrogenation of N-Sulfonyl Imines Using Chiral Ferrocenyl P,N,N-Ligands

An enantioselective hydrogenation of N-sulfonyl imines using a combination of Mn(CO)₅Br and chiral ferrocene-based P,N,N-ligand as the catalyst has been disclosed. The comparative studies demonstrated that the steric hindrance of the pyridinyl moiety in the ligands plays a crucial role in the enantioselectivity, in which the ligand bearing a phenyl group at the 6-position of the pyridinyl ring exhibited the best performance. The gram-scale synthesis of N-sulfonyl amine and subsequent derivatization have also been successfully performed.