Facile and Rapid Synthesis of 3,4-Dihydropyrimidin-2(1H)-one Derivatives Using [Et3NH][HSO4] as Environmentally Benign and Green Catalyst

5-acetyl-6-methyl-4-aryl-3,4-dihydropyrimidin-2(1H)-ones were synthesized in good to excellent by one-pot three-component Biginelli condensation in the presence of ammonium salt [Et3NH][HSO4] as an inexpensive and green catalyst under solvent-free conditions. High yields, short reaction time, easy work-up, a green environment which requires no toxic organic solvents and reusability of the catalyst are the advantages of this procedure. A broad range of structurally diverse aldehydes (aromatic aldehydes bearing electron withdrawing and electron releasing groups) was applied successfully, and corresponding products were obtained in good to excellent yields without any by-product. In addition, this catalyst was stable during the reaction process and could also be reused several times with consistent activity.