VOSO₄-catalyzed Biginelli condensation: An efficient synthesis of dihydro-1<i style="">H</i>-pyrimidine-2-thione/one and octahydro-2,5-quinazolinedione

1178-1182 The three component condensation of an aldehyde 1, urea/thiourea 2 and β-ketoester 3 / dimidone 7 in the presence of a catalytic amount of VOSO4 is disclosed for the synthesis of 3,4-dihydro-1H-pyrimidine-2-thione/one (DHPMs) 4 and octahydro-2,5-quinazolinedione 8 under solvent-free microwave irradiation conditions. High yields are achieved even on 1 g scale, while reaction times are considerably shortened compared to conven­tional heating conditions.