Highly Efficient Synthesis of Quinazoline-2,4(1H,3H)-diones from CO2 by Hydroxyl Functionalized Aprotic Ionic Liquids

Ionic liquids can be designed by varying a great deal of anions and cations offering efficient CO2 capture or CO2 utilization. Generally, the anion played a key role, but the cation did not have a significant impact. Here, a strategy for rational design of functionalized ionic liquids for efficient synthesis of quinazoline-2,4(1H,3H)-diones from CO2 has been developed through tuning the cations of aprotic ionic liquids. The basicity of cation affects its catalytic activity dramatically and the hydrogen bond from cation can promote this reaction. Then, hydroxyl functionalized ionic liquid [Ch][Im] was designed, which exhibited the best catalytic activity in this reaction. Through the combination of quantum-chemical calculations, NMR spectroscopic investigations, and controlled experiments, the results indicate that in situ generated [Ch][Im]-CO2 complex is the real catalyst. Furthermore, aprotic IL [Ch][Im] exhibits good generality and reuseability. Remarkably, quinazoline-2,4(1H,3H)-dione can also be obtained under simulated flue gas system on a gram scale with excellent yield using [Ch][Im] as catalyst. As we know, this is the first time that obtains quinazoline-2,4(1H,3H)-dione in excellent yield under flue gas condition