Brφnsted酸性离子液体中苯甲酸酯、苄酯的无溶剂微波合成

Synthesis of a Series of Benzoic Esters and Benzyl Esters in Novel Brφnsted Acidic Ionic Liquids under Solvent-free Microwave Irradiation Conditions

该文以1-甲基咪唑、吡啶、苄基氯、硫酸、磷酸为原料,合成了4种Brφnsted酸性离子液体：1-甲基-3-苄基咪唑硫酸氢根盐（a）,1-甲基-3-苄基咪唑磷酸二氢根盐（b）,N-苄基吡啶硫酸氢根盐（c）,N-苄基吡啶磷酸二氢根盐（d）,以它们作为催化剂和反应介质,考察了苯甲酸与系列脂肪醇、苄醇与系列脂肪酸、苯甲酸在无溶剂和微波辐射反应条件下的Fischer酯化反应,结果表明,当苯甲酸或苄醇与离子液体的摩尔比为1∶0.5时,无需外加催化剂,反应即可在化学计量条件下进行,12～20 min完成反应,苯甲酸酯与苄酯的收率分别为77%～98%和78%～98.5%,气相色谱纯度≥95%。离子液体循环使用3次,催化活性仅下降1.8%～3.4%。

Four easily accessible Brφnsted acidic ionic liquids, 1-methyl-3-benzylimidazolium hydrogen sulfate,1-methy-3-benzylimidazolium hydrogen phosphate,N-benzylpyridinium hydrogen sulfate,and N- benzylpyridinium hydrogen phosphate, were synthesized from the commercially available starting material N-methylimidazole, pyridine, benzyl chloride, sulphuric acid and phosphoric acid. They act as reaction media and catalyst for the synthesis of benzoic esters and benzyl esters under solvent-free and microwave irradiation conditions. When the mole ratio of benzoic acid or benzyl alcohol to ionic liquid was 1：0.5 ,the reactions proceeded smoothly with equal mole of substrates in 12 -20 min and gave the products in good or excellent yields （77% -98% and 78% -98.5% respectively）. The recycled ionic liquids can be used three times without significant loss of catalytic activity.