A Green and Magnetically Recyclable Hexaferrite (MgBaFe) Nanocatalyst for Efficient Multicomponent Synthesis of Dihydropyrimidinethiones

A sustainable and magnetically recoverable catalytic protocol has been developed for the synthesis of pharmacologically important 3,4-dihydropyrimidin-2(1H)-thiones (DHPM-thiones) via the Biginelli Multi-component reaction. The reaction of thiourea, aldehydes, and ethyl acetoacetate was efficiently catalyzed by barium-doped magnesium hexaferrite (MgBaFe₁₂O₁₉) nanoparticles under reflux in ethanol. The catalyst was synthesized via a sol–gel auto-combustion method and characterized by XRD and FT-IR analysis, confirming the formation of crystalline hexaferrite phase. Under optimized conditions (0.10 g catalyst, reflux, 2–5 h), excellent yields (88–96%) were achieved. The catalyst was magnetically recovered and reused up to four cycles without significant loss of activity. This protocol offers operational simplicity, high efficiency, recyclability, and environmentally benign reaction conditions compared to conventional homogeneous acid catalysts.