摘要
以交联聚苯乙烯(CPS)微球为载体,通过高分子反应和配位反应,简捷高效地制得一种新型的聚合物固载的手性Salen金属配合物催化剂Mn(Ⅲ)Salen-CPS.以间氯过氧苯甲酸(m-CPBA)为氧化剂、以N-甲基吗啉-N-氧化物(NMO)为轴向配体,将该非均相手性Salen Mn(Ⅲ)催化剂用于苯乙烯的不对称环氧化反应,深入系统地研究了催化剂结构与反应条件对苯乙烯的不对称环氧化反应的影响.实验结果表明,在苯乙烯的不对称环氧化反应中,微球Mn(Ⅲ)Salen-CPS具有高的催化活性与良好的的对映体选择性,20℃下反应8 h,苯乙烯的转化率可达85%;0℃下反应2 h,产物的ee值可达58%.Salen配基中手性二胺的不对称环境与轴向配体NMO的加入均可明显地提高产物的对映体选择性;而反应温度、时间、溶剂的极性及催化剂用量等反应条件对苯乙烯的不对称环氧化反应也都有很大的影响.低温有利于产物的ee值的提高,苯乙烯的不对称环氧化反应适宜的反应温度为0℃;使用极性弱的溶剂,有利于催化剂的对映体选择性;当反应进行到一定程度,产物的ee值会出现最高值,其后ee值会随时间延长呈现下降趋势,在不同的反应条件下,ee值出现最大值的时间不同.
By using crosslinked polysltyrene （CPS） microshpheres as support, a new immobilized chiral Salen Mn （ m ） complex catalyst Mn（ m ） Salen-CPS was simply and efficiently prepared via two polymer reactions and a coordination-chelating reaction. This solid catalyst was used in the asymmetric epoxidation of styrene with m-chloroperoxybenzoic acid （m-CPBA） as oxidant and N-methyl morpholine-N-oxide （NMO） as axial base, and its catalytic properties were examined in depth. The effects of main factors on the asymmetric epoxidation reaction of styrene were researched detailedly, and the relevant rules were analysed and discussed from the view of micro-mechanism. The experimental results show that in the asymmetric epoxidation reaction of styrene, Mn （ HI ）Salen-CPS micro- spheres have high catalytic activity and excellent enantioselectivity of the epoxide. At the temperature of 20 22 in 8 h, the conversion of styrene is closed to 85 % , and at the temperature of 0 22 in 2 h, the ee value of the epoxide can reach 58%. Both the asymmetric environment of the diamine and the addition of the axial base are beneficial to the obvious enhancement of the enantioselectivity of the epoxide. The reaction time, temperature, the polarity of the solvent and the used amont effect the asymmetric epoxidation reaction of styrene greatly. The lower temperature is beneficial to the enhancement of enantioselectivity of the epoxide, and for this present system, the suitable temperature of the asymmetric epoxidation of styrene is zero centigrade. Using the solvent with weak polarity is advanta- geous to the enantioselectivity of the epoxide. The ee value of the epoxide will exhibit a maximum value as the reaction is carried out to a certain degree, and then the ee value will decrease with the increase of the reaction time. Furthermore, the time at which the ee value exhibits a maximum value is different under the different reaction conditions.
出处
《分子催化》
EI
CAS
CSCD
北大核心
2013年第2期115-123,共9页
Journal of Molecular Catalysis(China)
基金
山西省自然科学基金资助项目(2010021008-4)
