SiO2-SO3H catalyzed one-pot synthesis of 4,5,8a-triarylhexahydropyrimido[4,5-d]pyrimidine-2,7(1H,3 H)-diones (4a-k) is reported under liquid phase catalysis. The catalyst is easily prepared, highly stable, very simple to handle and recycled for five times without loss of significant activity.
pyrimido[4,5-d]pyrimidine; silica functionalized sulfonic acid; liquid phase catalysis; recyclability; solid acid catalysis
