Solvent-Free Synthesis of Quinazoline-2,4(1H,3H)-diones Using Carbon Dioxide and a Catalytic Amount of DBU

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 synthesized successfully in 97% yield [DBU (0.2 equiv), CO₂ (1 bar), 120 °C].