3,4-Dihydropyrimidinones/thiones and their derivatives are synthesized via Biginelli
routes involving an aldehyde, 1,3-dicarbonyl compound and urea or thiourea. Use of catalysts such
as bismuth nitrate in acetonitrile or PPh3 without solvent lead to higher yields compared to the classic
method using HCl in ethanol. In such way, 3,4-dihydropyrimidinones which are hardly prepared
under classic conditions can be synthesized with fair yields.