An efficient three-component one-pot synthesis of 3, 4-dihydropyrimidin-2-(1H)-thione derivatives with a mesoporous iron ion exchanged Indian clay catalyst

This research work focuses on the potential usefulness of iron ion-exchanged Indian bentonite for one-pot synthesis of 3,4-dihydropyrimidine-2(1H)-thiones. Our goal was to produce mesoporous Fe³⁺-exchanged Indian clay (Fe³⁺-ExIC) and its supported forms through a wet impregnation technique. The physicochemical properties of the catalysts, such as XRD, FTIR, TGA, physisorption studies, SEM, and acidity, were investigated. It was found that Fe³⁺-ExIC catalysts are efficient and reusable acidic heterogeneous catalysts for the synthesis of 3,4-dihydropyrimidine-2(1H)-thiones by refluxing aldehyde, methyl acetoacetate and thiourea with acetonitrile in cyclocondensation. An optimized reaction condition was found for preparing 5-methoxycarbonyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-thione. A possible mechanism for the synthesis of 3,4-dihydropyrimidine-2(1H)-thiones has been proposed. Melting point, FTIR, and proton NMR were used to identify the products. Adequate catalyst activity was maintained over a period of six cycles, and a reduction in activity was attributed to a decrease in the acidity of the recycled catalyst.