Effective synthesis of cyclic carbonates from CO2 and epoxides catalyzed by KI/cucurbit[6]uril

The development of efficient, inexpensive, and nontoxic catalysts for cycloaddition of CO2 with epoxides to produce five-membered cyclic carbonates is a very interesting topic. In this work, cycloaddition of CO2 with propylene oxide (PO) to produce propylene carbonate (PC) catalyzed by potassium halides (KCl, KBr, and KI) in the presence of cucurbit[6]uril (CB[6]) was studied at various conditions. It was discovered that the potassium halides and CB[6] had excellent synergetic effect in promoting the reaction, and the KI/CB[6] catalytic system was the most efficient among them. The decrease of the activity and selectivity of KI/CB[6] was negligible after the catalytic system was reused five times. Further study indicated that the KI/CB[6] catalytic system was also very active and selective for the cyclo addition of CO2 with other epoxides, such as glycidyl phenyl ether, epichlorohydrin, and styrene oxide. The mechanism for the synergetic effect of KI and CB[6] was also discussed.