Poly(4-vinylimidazolium)s/Diazabicyclo[5.4.0]undec-7-ene/Zinc(II) Bromide-Catalyzed Cycloaddition of Carbon Dioxide to Epoxides

Poly(4-vinylimidazolium)s, derived from the self-immobilization of 4-vinylimidazoliums, with diazabicyclo[5.4.0]undec-7-ene (DBU) and zinc bromide (ZnBr2) are used as a highly efficient catalyst for the chemical fixation of carbon dioxide. This catalytic system has been applied for the preparation of cyclic carbonates from terminal epoxides and carbon dioxide. Many functional groups, including chloro, vinyl, ether, and hydroxy groups are well tolerated in the reactions. Moreover, the catalytic system was found to catalyze the conversion of more sterically congested epoxides which are generally considered to be challenging substrates for fabricating the cyclic organic carbonates. In addition, the disubstituted epoxides are found to react with retention of configuration. The polymer precatalyst is easily recovered and reused. A plausible reaction mechanism is proposed.