Theoretical study on the reaction of CO2 and 2-aminobenzonitrile to form quinazoline-2,4(1H,3H)-dione in water without any catalyst.

Development of efficient and green routes to convert CO2 into value-added products is of great importance. Recently, we found that quinazoline-2,4(1H,3H)-diones and their derivatives could be synthesized from CO2 and 2-aminobenzonitriles in water efficiently without a catalyst and excellent yields were obtained, while the reactions did not occur in organic solvents. In this work, using density functional theory (DFT) we conduct the first theoretical work to study the mechanism of the reactions in water. It is revealed that CO2 reacts via carbonic acid (H2CO3) with 2-aminobenzonitrile to form the product. Formation of H2CO3 from CO2 and water is the key for the reactions to proceed smoothly in water without a catalyst because of two reasons. First, H2CO3 reacts with 2-aminobenzonitriles more easily than CO2 itself; second, H2CO3 can effectively promote the reaction by the synergistic action of its carbonyl O atom and one of the hydroxyl O atoms.