碱性功能化离子液体催化Knoevenagel缩合反应

Knoevenagel Condensation Reaction Catalyzed by Functionalized Ionic Liquid

合成了碱性功能化离子液体氢氧化1-丁基-3-甲基咪唑([BMIM]OH),研究了将其作为催化剂催化芳香醛和丙二氰、氰基乙酸乙酯的Knoevenagel缩合反应。结果表明,在无溶剂条件下,采用摩尔分数为5%的该碱性功能化离子液体催化剂量,无需加入其它催化剂,能在较温和条件下催化Knoevenagel缩合反应,产率达81%～97%。在该反应体系中考察了一系列芳香醛和丙二氰、氰基乙酸乙酯的缩合反应,并推测了Knoeve-nagel缩合反应的机理,芳香醛与氰基乙酸乙酯缩合产物经1HNMR检测为E式烯烃。反应操作和后处理简单方便,离子液体通过简单的处理即实现回收利用。以苯甲醛和丙二氰为反应底物的模板反应,离子液体循环使用,其催化活性未明显降低,第3次使用时产率为86%。

The basic functionalized ionic liquid, 1-butyl-3-methylimidazolium hydroxide（ [ BMIM ] OH）, was prepared and used to catalyze the Knoevenagel condensation of aromatic ,aldehydes with malononitrile or ethyl cyanoacetate. The results show that the Knoevenagel condensation proceeds smoothly in the presence of 5% basic functionalized ionic liquid to afford the desired alkenes in good purity and 81% -97% yields under relatively mild conditions without solvent or any added catalyst. In this catalyst system, the Knoevenagel condensations of a series of aromatic aldehydes with malononitrile or ethyl cyanoacetate were programmed and a mechanism was postulated as well. When aromatic aldehydes reacted with ethyl cyanoacetate, the corresponding alkenes proved to be E-isomers by ^1H NMR. The procedure is simple and the ionic liquid could be recycled efficiently. With the condensation of benzaldehyde and malononitrile as an example, the ionic liquid was recycled three times with a slight decrease in catalytic activity and a yield of 86% was gained.