A green protocol for the synthesis of quinazoline-2,4(1H,3H)-diones from carbon dioxide and 2-aminobenzonitriles using a basic ionic liquid, 1-butyl-3-methyl imidazolium hydroxide ([Bmim]OH) as a catalyst have been reported. The effects of various reaction parameters like catalyst screening, catalyst loading, reaction time, solvent, temperature and pressure on the reaction system were investigated. A wide variety of aromatic aminobenzonitriles and five/six member N-heterocyclic carbonitriles were synthesized using this protocol. All these reaction were carried out under solvent-free condition. The ionic liquid was recovered and reused successfully for the title reaction. 6,7-Dimethoxyquinazoline-2,4(1H,3H)-diones, which is a key intermediates for several drugs (Prazosin, Bunazosin and Doxazosin) was synthesized successfully. (C) 2009 Elsevier B.V. All rights reserved.