Synthesis of some new bis-3,4-dihydropyrimidin-2(1H)-ones by using silica-supported tin chloride and titanium tetrachloride

Silica-supported tin chloride and titanium tetrachloride were prepared by the reaction of tin chloride and titanium tetrachloride with activated silica gel in refluxing toluene. These solid acids have been employed as the catalysts for the synthesis of bis-dihydropyrimidin-2(1H)-ones from aromatic dialdehydes, 1,3-dicarbonyl compounds and urea at 90 °C under solvent-free conditions.