Imidazolium ionic liquids cooperatively catalyzed the reaction of phenol and propylene carbonate

Ionic liquid 1-butyl-3-methyl-imidazolium acetate ([bmim]OAc) can effectively catalyze the reaction of phenol and propylene carbonate to form 1-phenoxy-propan-2-ol. The effects of reaction temperature, time, and catalyst amount were investigated in detail. Under the optimized reaction conditions, the yield of 1-phenoxy-propan-2-ol was 79%. The effect of cations and anions of ionic liquids on the reactivity was also studied. The cations play an important role in the reaction and the catalytic activity follows the order of 1-butyl-3-methyl-imidazolium ([bmim]) > 1, 2-dimethyl-3-butyl imidazolium ([bmmim]), which is consistent with the order of hydrogen bond donor ability. Meanwhile, the anions are also crucial to the reaction and the catalytic activity of imidazolium based ionic liquids follows the order of OAc > Cl > Br > BF₄, which is consistent with the order of the hydrogen bond acceptor ability. The dual roles of hydrogen bond donor and hydrogen bond acceptor of ionic liquids catalyze the reaction of phenol with propylene carbonate cooperatively. The ionic liquid can be reused at last 5 times without significant loss of catalytic activity.