Microwave-Promoted Facile and Rapid Solvent-Free Synthesis Procedure for the Efficient Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones and -Thiones Using ZrO2/SO42- as a Reusable Heterogeneous Catalyst

Sulfated zirconia (ZrO2/SO4 2-) solid superacid has been proved to be an efficient reusable heterogeneous catalyst for three-component one-pot cyclocondensation reaction of β-dicarbonyl compounds and urea/thiourea with structurally diverse aromatic aldehydes in solvent-free conditions to furnish the corresponding 3,4-dihydropyrimidin-2(1H)-ones and -thiones in good to excellent yields both under microwave irradiation and thermal conditions.