离子液体中Mn(salen)催化环己烯环氧化反应

Epoxidation of Cyclohexene Catalyzed by Mn(salen) Complex in Ionic Liquids

研究了离子液体中Mn(salen)络合物催化环己烯的环氧化反应,考察了反应介质、Mn(salen)络合物催化剂结构和反应条件等对环氧化反应的影响.在离子液体-CH2Cl2混合溶剂中,以相对廉价的H2O2为氧化剂,得到了高的环己烯转化率和环氧环己烷选择性.当以邻苯二胺和水杨醛制备的Mn(salen)络合物为催化剂,反应温度为273K时,在[bmi m]BF4-CH2Cl2的混合溶剂中,环己烯的转化率和环氧环己烷选择性分别可达100%和94·0%.此外,反应结束后,产物可以由正己烷萃取出来,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.

Epoxides are industrially important compounds used as pharmaceutical intermediates and fine chemicals. The traditional synthesis is by the way of epoxidation reaction of alkene with oxidant over Mn（salen） catalysts in organic solvent. However, the use of toxic solvents and oxidants is not friendly to the environment. The epoxidation of cyclohexene in ionic liquids catalyzed by Mn（salen） complex with hydrogen peroxide as oxidant was studied. The effects of the reaction medium, structure of Mn（salen） complexes, and reaction conditions on the epoxidation were investigated. It was found that handy hydrogen peroxide could be an alternative to expensive oxidant, and that ionic liquid medium gave higher conversion and selectivity to cyclohexene epoxide in comparison with the reaction performed in conventional organic solvent. The cyclohexene conversion of 100% and selectivity to cyclohexene epoxide of 94 % were obtained when the reaction was performed in the solvent of neutral [bmim]BF4-CH2Cl2 （3： 2, V/V） at 273 K using Mn（salen） complex prepared by salicylaldehyde and ophenyldiamine as a catalyst. Moreover, the final products could be easily separated from the reaction system by simple extraction with hexane.