溴化锌-卤化正四丁基铵高效催化合成苯乙烯环状碳酸酯

溴化锌-卤化正四丁基铵二元催化剂高效催化合成苯乙烯环状碳酸酯, 当n-Bu4NI/ZnBr2摩尔比为2时, 在短时间内(30 min)可将苯乙烯环氧化物几乎完全转化为环状碳酸酯, 无其它副产物的生成. 在ZnBr2/n-Bu4NX的催化体系中加入Au/SiO2 氧化催化剂时, 能将苯乙烯直接氧化, 然后碳酰化实现“一锅法”制备环状碳酸酯. 在此合成路线中担载的纳米金催化第一步苯乙烯环氧化反应; ZnBr2/n-Bu4NBr催化第二步CO2环加成反应. 在温和的反应条件下(80 ℃, 1 MPa, 4 h)将环状碳酸酯的产率提高到42%.

Synthesis of Styrene Carbonate Catalyzed Efficiently by Zinc Bromide and Tetra-n-butylammonium Halides

In this paper chemical fixation of CO2 was introduced for the synthesis of cyclic carbonate. Styrene carbonate can be synthesized via two routes, one is the cycloaddition of CO2 to epoxides and the other is oxidative carboxylation of styrene. The latter route couples the two processes, epoxidation of styrene and subsequent cycloaddition of CO2 to the epoxide formed. In the present work, it is shown that a catalyst system of ZnBr2 and n-Bu4NX(X=Br,I) has an excellent activity and selectivity for the cycloaddtion of CO2 to styrene oxide. At the n-Bu4NI/ZnBr2 molar ratio of 2, styrene oxide is quantitatively transformed to styrene carbonate with in a very short time(30 min). This catalyst system can be also applied for the oxidative carboxylation of styrene by combining with an epoxidation catalyst of Au/SiO2. Under the mild reaction conditions(80 ℃, 4 h, CO2 pressure 1 MPa), styrene carbonate was obtained in a yield of 42% without any organic solvent. In separate runs, it was found that Au/SiO2 is active for the epoxidation of styrene, and ZnBr2 and n-Bu4NBr cooperatively catalyze the subsequent CO2 cycloaddition to epoxide. The styrene carbonate yield obtained in the present study is the highest among those reported, but it is not still satisfactory for practical application.