Green Synthesis of 3,4-Dihydropyrimidinone/Thione Derivatives Using Alumina–Silica-Supported MnO ₂ as a Recyclable Catalyst in Ethanol

facile, environmentally friendly one-pot multicomponent protocol for the synthesis of dihydropyrimidinone (DHPM) and dihydropyrimidin(thio)one (DHPMT) derivatives has been developed using alumina-silica-supported MnO2 as a catalyst in ethanol, demonstrating a green chemistry approach. The Biginelli-type reaction between aryl aldehyde, ethyl acetoacetate, and urea/thiourea afforded DHPM/DHPMT in 85-92% yield within 45 min. Essential features of this protocol include a short reaction time, the use of a heterogeneous catalyst, and convenient catalyst separation.