Unprecedented Halide Dependence on Catalytic Asymmetric Hydrogenationof 2-Aryl- and 2-Alkyl-Substituted Quinolinium Salts by Using Ir Complexeswith Difluorphos and Halide Ligands

摘要

In conclusion, we have developed the first highly enantio-selective hydrogenation of 2-arylquinolinium salts by usingcationic dinuclear iridium(III) halide complexes with di-fluorphos and some atropisomeric chiral diphosphine li-gands as catalyst precursors. The resulting ee values of up to95 % are much better than those of the reduction of the cor-responding 2-arylquinolines.~([23,27])Moreover, this new catalystsystem also successfully converted 2-alkylquinolinium saltsto the corresponding tetrahydroquinolines with excellentenantioselectivities (up to 95 % ee). A notable feature ofthis catalysis is the unexpected superiority of chloro- andbromo-iridium catalysts over the corresponding iodo-iridi-um catalyst, which is opposite to the halide effect. As an ap-plication of our new catalyst system, we demonstrated an ef-ficient access to the optically active 6-hydroxy-2-(4-hydroxy-phenyl)-1-(4-(2-(pyrrolidin-1-yl)ethoxy)-benzyl)-1,2,3,4-tet-rahydroquinoline (1).