Alcohol amine-catalyzed CO₂conversion for the synthesis of quinazoline-2,4-(1H,3H)-dione in water

The conversion of CO₂to high value-added chemicals in water using environment-friendly and cost-effective catalysts is a very significant topic. In this work, a green method for the conversion of CO₂catalyzed by alcohol amines has been developed. Alcohol amines showed considerable activating ability to CO₂in the cyclization with 2-aminobenzonitrile to quinazoline-2,4(1H,3H)-dione in water. Notably, when diethanolamine (DEA) was used as the catalyst, 94% yield of quinazoline-2,4-(1H,3H)-dione could be achieved. A plausible mechanism has been proposed based on the¹H NMR, FT-IR analysis and DFT calculation. The excellent catalytic performance is attributed to the combined effect of both the secondary amine and hydroxyl groups on alcohol amines with the assistance of water in the formation of carbamate. Water plays a bi-functional role of solvent and co-catalyst in this catalytic process. Catalysts can be easily recovered and reused five times without significant loss of activity.