An efficient, rapid and green synthesis of glycoluril, imidazolidine-2-one, imidazole-2-one and imidazole-2-thiol derivatives have been accomplished by the reaction of urea/thiourea derivatives andα-diketone at 100°C in the presence of trimethylsilyl chloride (TMSCl) as Lewis acid catalyst under solvent-free conditions. This approach offers many advantages such as good product yields, various products, short reaction time, easy isolation of products, facile purification and environmentally benign reaction conditions.