Keggin and Dawson-type polyoxometalates as efficient catalysts for the synthesis of 3,4-dihydropyrimidinones: experimental and theoretical studies

3,4-Dihydropyrimidinones were synthesized by a multicomponent condensation of an aldehyde, a B-keto ester, and urea, in acetonitrile and ethanol using Keggin and Dawson type polyoxometalates as catalysts. Keggin heteropolyacid, H4SiMO12O40, is more efficient compared to Keggin and Dawson salts and to the Biginelli classical reaction conditions. It leads to good yields and short reaction times. Theoretical calculations let us to confirm the reaction mechanism. (C) 2016 Elsevier Ltd. All rights reserved.