The first highly enantioselective hydrogenation of 2-arylquinolinium salts by using cationic dinuclear iridium (III) halide complexes with difluorphos and some atropisomeric chiral diphosphine ligands as catalyst precursors has been reported. Asymmetric hydrogenation by using chiral transitionmetal complexes represents one of the cleanest and most environmentally benign processes available for producing optically pure organic compounds. The conversions were determined by H NMR spectroscopic analysis of the crude product. The new catalyst system also successfully converted 2-alkylquinolinium salts to the corresponding tetrahydroquinolines with excellent enantioselectivities. This catalysis is the unexpected superiority of chloro- and bromo-iridium catalysts over the corresponding iodo-iridium catalyst, which is opposite to the halide effect.
All Science Journal Classification (ASJC) codes
- Organic Chemistry