Synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones via Biginelli reaction promoted by bismuth(III)nitrate or PPh3 without solvent

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.