固-液相转移催化法合成1-(2,4-二氯苯基)-2-(1-咪唑基)-乙醇

Synthesis of 1-(2,4-Dichlorophenyl)-2-(1-Imidazol)-Ethanol by Solid-Liquid Phase Transfer Catalysis

用固-液相转移催化法由1-(2,4-二氯苯基)-2-氯-乙醇与咪唑在NaOH存在下进行N-烷基化反应合成了1-(2,4-二氯苯基)-2-(1-咪唑基)-乙醇。由实验得到的反应动力学方程符合拟一级反应,提出了合理的反应机理。详细研究了催化剂、溶剂、卤代烃的卤素原子、碱的种类和用量、反应温度和搅拌速度对反应的影响。对溴化十六烷基三甲基铵(CTMAB)、苄基三乙基氯化铵(TMBAC)、四丁基溴化铵(TBAB)、聚乙二醇400(PEG400)和聚乙二醇600(PEG600)五种催化剂的活性进行了考察,结果表明,具有对称结构的TBAB和PEG400的催化活性最强。反应产率与溶剂极性密切相关,中等极性的四氢呋喃(THF)、丙酮是合适的溶剂。低活性季铵盐CTMAB、TMBAC作催化剂时,在反应体系中加入溴化钠,能提高反应活性。快速搅拌和加热对反应有促进作用。在优化反应条件下,产率达88.5%。

The N-alkylation reaction between 1-（2,4-dichlorophenyl）-2-chloro-ethanol and imidazole was carried out through a solid-liquid phase transfer catalysis （PTC） in a two phase medium of organic solvent and solid NaOH. The rational reaction mechanism of alkylation with PTC was proposed and the experiments show that the alkylation reaction is a pseudo first-order reaction. The effects of the variety of catalyst, organic solvent used and the halogen ion released from the alkyl halide added, the amount and kind of base used, the reaction temperature and the agitation used on the alkylation reaction were investigated. Five kinds of catclysts, such as cetyltrimethyl ammonium bromide （CTMAB）, benzylttriethyl ammonium chloride （TMBAC）, tetrabutyl ammonium bromide （TBAB）, polyethylene glycol 400 （PEG400） and polyethylene glycol 600 （PEG600）, were employed to examine their catalytic activities. The experimental results show that the TBAB with symmetrical structure and the PEG400 have the highest catalytic activity for the alkylation reaction. The yield of the product is closely related to the polarity of the solvent, and the organic solvents with moderate polarity, such as THF and acetone, are suitable to be used as the solvent for the above alkylation reaction. When the catalysts with lower catalytic activity for alkylation reaction are used, such as CTMAB and TMBAC, the addition of NaBr into the reaction system can increase the reaction activity. Vigorous agitation and heating can promote the reaction rate too, and under the optimized conditions, the yield of the product can reach about 88.5%.