OICC Press Iranian Journal of Catalysis 2345-4865 6 2 2024 02 03 Oxalic acid dihydrate catalyzed synthesis of 3,4-dihydropyrimidin-2-(1H)-one derivatives under thermal and solvent-free conditions EN Farzaneh Mohamad Pour Department of Chemistry, Faculty of Science, University of Sistan and Baluchestan, P. O. Box 98135-674 Zahedan, Iran. Malek Taher Maghsoodlou Chemistry Department, Faculty of Science, University of Sistan and Baluchestan, Zahedan, Iran Reza Heydari Department of Chemistry, the University of Sistan and Baluchestan, P.O. Box 98135-674, Zahedan, Iran. Mojtaba Lashkari Faculty of Science, Velayat University, Iranshahr, Iran. Journal Article 2024 02 03 Oxalic acid dihydrate as a green, mild and efficient catalyst for the one-pot three-component Biginelli synthesis of 3,4-dihydropyrimidin-2-(1H)-one derivatives from the reaction between β-keto esters (methyl or ethyl acetoacetate), aromatic aldehyde (benzaldehye derivatives) and urea or thiourea under thermal and solvent-free conditions with excellent yields and short reaction time is studied. The most remarkable benefits of this synthetic method include the green methodology, an eco-friendly, inexpensive and non-toxic catalyst, solvent-free conditions, the availability of materials, and a simple operational procedure with no column chromatographic separation. The products were characterized by melting points, IR and 1H NMR spectroscopy.