Unprecedented Halide Dependence on Catalytic Asymmetric Hydrogenation of 2-Aryl- and 2-Alkyl-Substituted Quinolinium Salts by Using Ir Complexes with Difluorphos and Halide Ligands
the key to achieving high catalytic activity and enantioselectivity on asymmetric hydrogenation of 2‐aryl‐ and 2‐alkyl‐substituted quinolinium salts. The reaction was catalyzed by a cationic dinuclear iridium(III) complex with difluorphos and chloride or bromide ligands and gave the corresponding 2‐substituted 1,2,3,4‐tetrahydroquinolines in high enantioselectivities (up to 95 % ee; see scheme, difluorphos=[(4