KAl(SO4)2·12H2O supported on silica gel as a novel heterogeneous system catalyzed biginelli reaction: One-pot synthesis of di-hydropyrimidinones under solvent-free conditions

3,4-Dihydropyrimidin-2(1H)-ones derivatives were synthesized in moderate to high yields in one-pot three component reaction from the corresponding aldehydes, ketones or 1,3-dicarbonyl compounds and urea, in the presence of catalytic amount of KAl(SO4)2·12H2O (Alum) supported on silica gel (Alum-SiO2) as a non-toxic, reusable, inexpensive and easily available reagent, under solvent-free conditions at 80 °C. Compared to the classical Biginelli reaction, this new method consistently has the advantage of good yields.