连续流微反应器中简单咪唑的制备

Preparation of simple imidazoles in continuous-flow microreactor

研究了微反应器中Radziszewski反应连续高效制备咪唑的工艺过程,考察了停留时间、反应温度、甲醛/乙二醛摩尔比、醋酸铵/乙二醛摩尔比、乙二醛浓度及不同氨源等工艺参数对咪唑收率的影响,优化了咪唑合成的工艺路线。以醋酸铵为氨源、压力为1.7 MPa、反应温度为140℃、乙二醛浓度为0.25 mol/L、甲醛/乙二醛摩尔比为1.4、醋酸铵/乙二醛摩尔比为2.0、停留时间为159.4 s的条件下,咪唑收率高达81.6%。此外,探索了所构建的微反应器系统对于2-甲基咪唑、2-乙基咪唑和2-异丙基咪唑的合成过程适用性,并对其合成过程中存在的问题进行了讨论。

Highly efficient process of imidazole synthesis by Radziszewski reaction was explored in a continuous-flow microreactor. Process variables of residence time, reaction temperature, molar ratio of formaldehyde to glyoxal, molar ratio of ammonium acetate to glyoxal, glyoxal concentration, and different ammonia sources on imidazole yield were studied to obtain optimized condition for imidazole synthesis in the continuous-flow microreactor. Under the optimal operating conditions of ammonium acetate as ammonia source, pressure 1.7 MPa, reaction temperature 140℃, glyoxal concentration 0.25 mol/L, molar ratio of formaldehyde to glyoxal 1.4, molar ratio of ammonium acetate to glyoxal 2.0, and residence time 159.4 s, yield of imidazole could be reached to 81.6%. Besides, the continuous-flow microreactor was tentatively investigated for preparation of 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole and challenges appeared in the process were discussed.