Highly efficient conversion of aromatic acylals to 3, 4-dihydropyrimidinones: a new protocol for the Biginelli reaction

A novel version of the Biginelli reaction using an acylal as a masked carbonyl functionality together with ethyl acetoacetate and urea or thiourea to give dihydropyrimidinones is reported. The reaction is catalyzed by 12-tungstophosphoric acid (PW), 12-molybdophosphoric acid (PMo) or zinc chloride and performed in one-pot under solvent-free conditions.