Functionalized Ionic Liquids For Carbon Dioxide Coupling Reaction To Synthesis Cyclic Carbonate

In the present day,the rising level of atmospheric CO₂ has become a major threat to the environment and human health,because carbon dioxide is normally considered to be one of the main causes of global warming.On the other hand,carbon dioxide is a very attractive C1 resource in organic synthesis because it is abundant,economical and non-toxic.Therefore,converting carbon dioxide into chemicals of industrial value is a good solution.The researchers reported the successful production of methanol,carbon monoxide,urea,salicylic acid and polycarbonates using CO₂ as substrate.One of the most effective methods is to convert carbon dioxide and epoxides into corresponding cyclic carbonates.Because the reaction not only achieves 100%atomic utilization,but also the resulting cyclic carbonates can be used as important chemical intermediates for the synthesis of special fine chemicals.In this paper,a series of novel one-component halogen-free hydroxyl functional ionic liquids（1-hydroxyethyl-1-methylpyrrolidinium lactic acid,1-hydroxyethyl-1-methylpyrrolidinium acetic acid,1-hydroxyethyl-1-methylpyrrolidinium butyric acid,1-hydroxyethyl-1-methylpyrrolidinium succinic acid,1-hydroxyethyl-1-methylpyrrolidinium glycolic acid,1-hydroxyethyl-1-methylpyrrolidinium aspartic acid,1-hydroxyethyl-1-methylpyrrolidinium glutamic acid）were synthesized via a simple method.In the absence of any organic solvent and co-catalyst,it was used as a highly efficient catalyst for CO₂ coupling reaction.Taking 1-hydroxyethyl-1-methylpyrrolidinium lactic acid（[EMPy OH][LAc]）as a sample,the reaction parameters（different dosage of catalyst,initial CO₂ pressure,time and temperature）were reconnoitered and optimized,and the possible mechanism of synergistic interaction between cations and anions in OH-functional group ionic liquids was proposed.The experimental results displayed that when the dosage of[EMPy OH][LAc]was 0.8 mol%,the initial CO₂pressure was 0.3 MPa,and the temperature was 90℃,the yield of chloropropene carbonate can reach 98.3%after catalysis in the reactor for12 h.Simultaneously,three types of OH-functional group imidazole ionic liquids were synthesized,namely 1-vinyl-3-hydroxyethyl imidazole glycolic acid,1-vinyl-3-hydroxyethyl imidazole lactic acid and 1-vinyl-3-hydroxyethyl imidazole butyric acid.Taking 1-vinyl-3-hydroxyethyl imidazole glycolic acid（[Evim OH][GA]）as a sample,the reaction parameters（different dosage of catalyst,initial CO₂pressure,time and temperature）were reconnoitered and optimized,and the possible mechanism of synergistic interaction between cations and anions in OH-functional group ionic liquids was proposed.The experimental results exhibited that when the dosage of[Evim OH][GA]was 1.0 mol%,the initial CO₂ pressure was 0.4 MPa,and the temperature was 80℃,the yield of chloropropene carbonate was 97.7%after catalysis in the reactor for 12 h.These novel functionalized ionic liquids can be used as green substitutes to efficiently catalyze the formation of cyclic carbonates from CO₂ without organic solvents and halogens.