关键词: 金鸡纳生物碱, 奎宁, 辛可宁, 手性双胺配体, 手性催化剂, 不对称氢转移反应, 苯乙酮

Abstract: The asymmetric transfer hydrogenation using 2-propanol as the hydrogen source is a practical and versatile method for obtaining secondary alcohols because of the inexpensive reagents and operational simplicity. Six chiral diamine ligands were synthesized from natural Cinchona alkaloids, quinine and cinchonine, under mild conditions. These were first tested by asymmetric transfer hydrogenation of acetophenone in iridium and rhodium catalytic systems using 2-propanol as the hydrogen source. Both the iridium and rhodium complexes of these ligands showed high activity for this reaction, and the enantioselectivity was influenced deeply by the structure of the chiral ligands. The complexes of 9-amino(9-deoxy)epiquinine and 9-amino(9-deoxy)epicinchonine proved to be effective catalysts, whereas their benzamides and 4-chlorobenzamides provided only moderate ee. The Ir-complex of 9-amino(9-deoxy)epicinchonine was also applied in the hydrogenation of seven aromatic ketone substrates, resulting in a high catalytic activity (80%～90%) and high enantioselectivity (95%～97% ee, except 72% ee for 4-chloroacetophenone). This is the first case using Cinchona alkaloids skeleton in the iridium catalyzed asymmetric reactions.

Key words: Cinchona alkaloid, quinine, cinchonine, chiral diamine ligand, chiral catalyst, asymmetric transfer hydrogenation, acetophenone