Transformation of CO2 into α-alkylidene cyclic carbonates at room temperature and atmospheric pressure by phthalimide based ionic liquids with inert cation and moderate basicity

Abstract

The carboxylative coupling of carbon dioxide (CO2) with propargyl alcohols is an important pathway to accomplish the reusability of CO2. Moreover, the α-methylene cyclic carbonates are the critical intermediate to generate the fine chemicals and pharmaceuticals. However, the robust catalyst is still limited to perform this reaction under the mild conditions, especially to obtain the equilibrium among several reaction conditions including reaction time, reaction temperature, and catalyst amount. The novel ionic liquid, [Pth][BTMA], is synthesized in this work to be catalyst for the title reaction along with AgOAc as the co-catalyst. To explore the influence of cation, anion, and Ag salt, other four ionic liquids are utilized to catalyze the reaction along with five different Ag salts. Under the atmospheric pressure and 30 °C, the 98.7 % product yield is achieved by [Pth][BTMA]/AgOAc within 9 h, which are better than most of catalysts in literature. More important, the role of cation and anion in the catalysis is elucidated by the 1H NMR, 13C NMR, and density functional theory (DFT) calculations. Both the moderate basicity and inert cation of [Pth][BTMA] contribute the excellent catalytic activity.