In conclusion, we have reported the synthesis of dihydropyrimidinones by simple one-pot, three
component, Biginelli condensation of an aldehyde, -ketoester and urea catalyzed by ammonium
chloride or montmorillonite KSF under solvent-free conditions. The obtained results show that
montmorillonite KSF can be reused after recovery with similar reactivity. The use of ultrasonic
irradiation at room temperature improved the Biginelli reaction yielding the products in good to
excellent yields within 40 minutes. Ultrasonic irradiation offers several significant advantages over
conventional method including higher yields, milder conditions, higher purity and shorter reaction
times.