Solvent‐Free Approach to 3,4‐Dihydropyrimidin‐2(1H)‐(thio)ones: Biginelli Reaction Catalyzed by a Wells–Dawson Reusable Heteropolyacid

Abstract

The Biginelli reaction is performed in an efficient, simple, solvent‐free procedure, using a small amount of H₆P₂W₁₈O₆₂ · 24H₂O, a reusable heteropolyacid catalyst with Wells–Dawson structure. Both aromatic and aliphatic aldehydes, and different β‐dicarbonyl compounds and urea or thiourea, were used as starting materials. Seventeen examples of dihydropyrimidinones and dihydropyrimidinethiones were prepared by heating the reactants either in refluxing acetonitrile or in the absence of solvent. Operational simplicity, the use of a noncorrosive, reusable catalyst in solventless conditions, short reaction times, and very good to excellent yields in most of the selected examples are the main advantages of the method.

Keywords:

• Biginelli reaction
• clean processes
• dihydropyrimidinones
• solvent‐free
• Wells–Dawson catalyst

Acknowledgments

Financial support from CONICET (Argentina), Fundación Antorchas, and Universidad Nacional de La Plata (Projects 11‐X341 and 11‐A135) is gratefully acknowledged. A. G. S. also thanks CONICET for a grant. G. P. R., G. B., and H. J. T. are members of CONICET.