Design and synthesis of pyridinamide functionalized ionic liquids for efficient conversion of carbon dioxide into cyclic carbonates

Abstract

Novel and facilely prepared 2-pyridinamide-functionalized ionic liquids 1–4 (PAIL1–4) were explored for the cycloaddition reaction of carbon dioxide with various epoxides to generate cyclic carbonates. The optimum temperature, CO2 pressure, and catalyst dosage of the cycloaddition reaction, are 60 °C, 0.5 MPa, and 5 mol% respectively. The synthesized N, N-dimethyl-N-(2-oxo-2-(pyridin-2-ylamino)ethyl)butan-1-aminium iodide (PAIL-3) exhibited brilliant catalytic activities under mild conditions with nearly quantitative selectivity and conversion in the absence of any solvents, or metal co-catalysts. The catalyst PAIL-3 could be recycled 4 times without obvious loss of its catalytic activity. Moreover, a plausible mechanism is proposed based on the NMR experiments. The designed pyridinamide functionalized ionic liquids integrated pyridine unit, halogen anion and the N-H moiety in amide and they have an excellent synergistic catalytic effect in promoting the coupling reactions of carbon dioxide and epoxides.