L-脯氨酸修饰的铱催化苯乙酮及其衍生物不对称加氢反应

Asymmetic Hydrogenation of Acetophenone and Its Derivatives Catalyzed by L-Proline Modified Ir / γ-Al_2O_3

在温和条件下制备了L-脯氨酸稳定并修饰的负载型金属铱催化剂,用于苯乙酮及其衍生物不对称催化加氢反应.考察了L-脯氨酸的量、溶剂、碱以及碱的量和氢气压力对苯乙酮不对称催化加氢反应的影响.结果显示,该催化剂催化苯乙酮不对称加氢反应获得了92.1%的转化率和32.9%的对映选择性(e.e.),催化2'-(三氟甲基)苯乙醇的对映选择性为39.3%,这一结果高于目前报道的天然手性修饰剂修饰的负载型金属催化剂.该催化循环使用5次,对映选择性只有小幅度下降.

Under the mild conditions, supported iridium catalyst stabilized and modified by L-proline was pre- pared. The asymmetric hydrogenation of acetophenone and its derivatives catalyzed by the catalyst was studied. The effects of the concentration of L-proline, different solvents, different base additives and concentration of base, and hydrogen pressure were evaluated in detail. The results show that this catalytic system had higher activity and enan- tioselectivity than the supported metal catalysts which were modified by the nature chiral modifier in the reaction of asymmetric hydrogenation of acetophenone and its derivatives. The conversion and the enantioselectivity for the asymmetric hydrogenation of acetophenone were 92.1% and 32.9%, respectively. Especially, the enantioseleetivi- ty for asymmetric hydrogenation of 2＇-fluoroacetophenone was 39.3%. The catalyst can be reused five times with a little loss of the enantioselectivity.