Abstract An ideal reaction system, which is aimed at sustainable chemistry, was developed. Under solvent-free conditions, quinazoline-2, 4 (1H, 3H)-diones were obtained in good to excellent yields from 2-aminobenzonitriles with only carbon dioxide (1 bar) and a catalytic amount of base (DBU or DBN). For example, 6, 7-dimethoxyquinazoline-2, 4 (1H, 3H)-dione, which is a key intermediate of several drugs (Prazosin, Bunazosin, and Doxazosin) was ...