Efficient Synthesis of 3,4-Dihydropyrimidin-2(1H)-one Using Metal Hydrogen Sulfates M(HSO4)n as Catalyst under Solvent-Free Conditions

Metal hydrogen sulfates M(HSO4)n (Ca(HSO4)2, Zn(HSO4)2, and oxone®) were used to catalyze one-pot three-component condensation reactions of aldehydes, 1,3-dicarbonyl compounds, and urea at 90°C under solvent-free conditions to give 3,4-dihydropyrimidin-2(1H)-one in high yields.