Efficient One Pot Capture and Conversion of CO2 into Quinazoline-2,4(1H,3H)-diones Using Triazolium-Based Ionic Liquids

CO2 capture and utilization (CCU) have aroused much attention. In this paper, several novel triazolium-based ionic liquids (ILs) were developed for highly efficient transformation of CO2 into quinazoline-2,4(1H,3H)-diones. The catalytic behaviors such as the effects of IL structures and reaction parameters, catalyst recyclability, and scope of substrates were studied in detail. As compared to the reported homogeneous and heterogeneous catalysts, the [HTMG][Triz] with a tetramethylguanidine cation and a triazole anion exhibited an exceptional activity at 50 °C and 1 atm CO2 without any organic solvents. On the basis of the CCU strategy, we first studied the equimolar CO2 capture by the [HTMG][Triz] and one pot conversion of activated CO2 into various quinazoline-2,4(1H,3H)-diones, and good to excellent product yields were obtained. In addition, the catalytic performance for synthesis of quinazoline-2,4(1H,3H)-dione under low concentration of CO2 using a simulated flue gas was studied. The developed triazolium-based ILs could realize simultaneous activation of CO2 and the substrates under ambient conditions, which also have been demonstrated to support the reaction mechanism well. The integrative protocol here shows great significance in the practical synthesis of quinazoline-2,4(1H,3H)-dione and their derivatives from captured CO2 waste under mild conditions.