Br(o)nsted酸性离子液体在醛醇缩合反应中的应用

合成了一系列Br(o)nsted酸性离子液体并将其应用在醛醇缩合反应中.醛醇缩合产物由于极好的溶剂性质等被广泛用作溶剂和试剂.离子液体BSmim]OTf]在甲醛和乙二醇缩合生成1,3-二氧五环的反应中表现出了极好的催化活性,甲醛转化率和主产物1,3-二氧五环选择性分别可以达到96.1％和92.4％.对影响离子液体催化性能的因素进行了探索,并对催化反应中的离子液体的用量、反应温度、反应时间以及反应物料比进行了考察.通过Hammett酸度函数法测定了所用到离子液体的酸性,结果表明离子液体酸性与其在缩合反应中的催化活性顺序完全一致,酸性越强催化性能越好.结合实验给出了离子液体BSmim]OTf]催化甲醛和乙二醇缩合反应的可能的反应机理.该催化剂体系具有良好的催化性能,反应可以在较温和的条件下进行,实现了高活性和高选择性的目标,产物易分离,催化剂重复使用7次,其催化活性基本不变.并将该Br(o)nsted酸性离子液体进一步应用到其他醛(酮)醇缩合反应中.

Br(o)nsted Acidic Ionic Liquids as Efficient and Recyclable Catalysts for the Acetalization of Aldehyde with Alcohol

A series of Br(o)nsted acidic ionic liquids (BAILs) were synthesized and used as efficient and environmentally benign catalysts for the acetalization of aldehyde with alcohol.Acetals were widely used as solvent and reagent for excellent solvent property.Ionic liquid BSmim] OTf] showed superior catalytic activity in the acetalization of formaldehyde with ethylene glycol.The effects of various parameters such as structure of ionic liquid,catalyst dosage,reaction temperature,reaction time,and molar ratio of the formaldehyde to ethylene glycol were investigated.Hammett method (H0) had been used to determine the acidity order of these ionic liquids.A proposed reaction mechanism for the acetalization of formaldehyde with ethylene glycol catalyzed by BSmim] OTf] was given.The results show that the order of acidity is consistent with the catalytic activities observed in acetalization reaction.Ionic liquid BSmim] OTf] could be recycled seven times without significant loss in catalytic activity.The protential application of BAILs in the acetalization of aldehyde with alcohol was also investigated.