氯铝酸盐双阳离子液体催化合成乙氧基亚甲基丙二酸二乙酯

Synthesis of ethoxymethylenemalonate diethyl ester catalyzed by chloroaluminate dication ionic liquids

摘要:

摘要：以N-烷基咪唑和二氯烷烃为原料，经过取代反应合成氯化咪唑鎓盐，添加AlCl3络合制备了7种氯铝酸盐双阳离子液体。以制备的离子液体为催化剂，通过原甲酸三乙酯和丙二酸二乙酯之间的缩合反应合成乙氧基亚甲基丙二酸二乙酯。采用IR对离子液体的酸度进行测定，通过27Al NMR检测离子液体中铝的形态来分析提出的反应机理。考察了催化剂种类、催化剂用量、反应物投料比、反应温度、反应时间及催化剂循环次数对反应的影响。得到的最佳工艺条件为∶以1,6-双（N-甲基咪唑基）己烷氯铝酸盐离子液体〔[C6(Mim)2]Cl2-4AlCl3〕作为催化剂，用量为0.8%（以丙二酸二乙酯摩尔量计），原甲酸三乙酯、丙二酸二乙酯和乙酸酐的摩尔比为1.75∶1.00∶2.50，反应温度为100 ℃反应2 h后140 ℃反应6 h。该条件下，丙二酸二乙酯的转化率高达98%，目标产物的选择性和收率分别为98%和97%。

Abstract:

Abstract: Imidazolium chloride were synthesized via substitution reaction between N-alkylimidazole and dichloroalkane, then AlCl3 was added to complex to prepare seven chloroaluminate dication ionic liquids. The prepared ionic liquids were used to catalyze the condensation reaction between triethyl orthoformate and diethyl malonate to synthesize ethoxymethylenemalonate diethyl ester. The acidity of ionic liquids were measured by IR. The proposed reaction mechanism was analyzed by detecting the morphology of aluminum in catalysts by 27Al NMR. The effects of catalyst type, catalyst dosage, ratio of materials to solvent, reaction temperature, reaction time and catalyst recyclability on the reaction were investigated. The optimal process conditions were using 1,6-bis(N-methylimidazolyl)hexane chloroaluminate ionic liquid 〔[C6(Mim)2]Cl2-4AlCl3〕 as catalyst with its dosage of 0.8% (calculated based on molar amount of diethyl malonate), the molar ratios of triethyl orthoformate to diethyl malonate and to acetic anhydride at 1.75∶1.00∶2.50, with program temperature at 100 ℃ for 2 h and 140 ℃ for 6 h.Under these conditions, the conversion of diethyl malonate reached up to 98%, selectivity and yield of target product were 98% and 97%.