【摘要】 二烷基咪唑或烷基吡啶卤化物与ZnCl2 构成一类新型的具有Lewis酸性的离子液体 ,以其为催化剂和反应介质 ,通过月桂烯与丙烯醛的Diels Alder反应高区域选择性地合成了对位柑菁醛 .结果表明 ,与常规有机溶剂 ZnCl2 催化体系相比 ,该体系不仅显著地加快了反应速率 ,而且明显提高了对位柑菁醛的区域选择性 .当ZnCl2 与二烷基咪唑或烷基吡啶卤化物的摩尔比为 2∶1,温度为 15℃时月桂烯几乎可完全转化为柑菁醛 ,且对位柑菁醛的区域选择性 p/m >18.与氯铝酸盐离子液体相比 ,该离子液体对水和空气不敏感 .反应结束后 ,产物与离子液体自动分层 ,解决了传统均相催化体系中催化剂与产物不易分离的问题 .分离后的离子液体用正己烷清洗提纯后 ,重复使用 4次 ,其催化活性和区域选择性基本保持不变 .更多还原

【Abstract】 Para-myrac aldehyde (4-(4′-methyl-3′-pentyl)-Δ 3-cyclohexenecarboxaldehyde) has been found to be very useful in perfume industry. The traditional synthesis is by the way of Diels-Alder reaction of myrcene with acrolein over Lewis acid catalysts in organic solvent. Usually the regioselectivity for para-myrac aldehyde is low, and the use of toxic solvents is not friendly to the environment. In this paper, novel Lewis acidic ionic liquids were synthesized by combining ZnCl 2 with dialkylimidazolium halide or alkylpyridinium halide (where halide is chloride or bromide) and were used in the Diels-Alder reaction of myrcene with acrolein functioning as both Lewis acid catalyst and green solvent. Compared with the reaction performed over ZnCl 2 catalyst in the conventional organic solvent, excellent yield, rate-enhancement and higher regioselectivity for para-cycloadduct were obtained in the ZnCl 2 ionic liquids. When the reaction was performed at 15 ℃ for 2 h in the ionic liquids with the molar ratio of ZnCl 2 to dialkylimidazolium halide or alkylpyridinium halide being 2∶1, myrcene was almost completely converted into myrac aldehyde with regioselectivity of p/m>18. Compared with chloroaluminate ionic liquids, the ZnCl 2 ionic liquids are not moisture-sensitive and can be easily separated from reaction products. The ionic liquids are easily recycled after washing with hexane, allowing their reuse at least four times with no loss in activity and regioselectivity.更多还原