Asymmetric aldol reaction of unmodified aldehydes with ketones catalyzed by 1(R),2(R)-bis((S)-prolinamido)cyclohexane (1) or (Rax)-2,2′-bis((S)-prolinamido)-1,1′-binaphtyl (2) proceeds with high yield (68–99%) and diastereoselectivity (dr ≥ 75/25) in the system (1-butyl-3-methylimida-zolium) tetrafluoroborate ([bmim][BF4])-water. The dependence of ee of the dominating anti-diastereomer of aldol on the percentage of water has a maximum at 50 vol.%. Catalyst 1 can be recycled 5 times without losses in the aldol yield, dr and ee.
在 1(R),2(R)-双((S)-脯
氨酰胺基)
环己烷 (1) 或 (Rax)-2,2′- 双((S)-脯
氨酰胺基)-1、1′-联
萘(2)在(1-丁基-3-甲基
咪唑)四
氟硼酸盐([bmim][BF4])-
水体系中以高产率(68-99%)和非对映选择性(dr ≥ 75/25)进行。醛醇的主要反非对映异构体的ee值与
水的百分比的关系在 50 vol.%时最大。催化剂 1 可以循环使用 5 次,而不会损失醛醇产率、dr 和 ee。