Application of magnetic materials bearing Brønsted acid sites – based on the modification of amorphous carbon with ionic liquids as catalysts for synthesis of dihydropyrimidinone derivatives via the Biginelli reaction†

Biomass is a widely available and renewable natural resource derived from plant and animal materials. In addition to its role as an energy source, it is increasingly recognized as a valuable raw material for synthesizing solid catalysts. These catalysts play a crucial role in various organic synthesis reactions, offering a sustainable and eco-friendly alternative to conventional catalyst materials. In this study, by modifying amorphous carbon derived from rice husks with ionic liquid, followed by sulfonation and magnetization with magnetite, we successfully synthesized a solid catalyst Fe₃O₄@AmC/KSO₃H (KS71), which is a magnetic material bearing Brønsted acid sites, for synthesizing dihydropyrimidinone derivatives via the Biginelli reaction. The synthesized catalyst can be easily separated, recovered, and reused without generating or releasing by-products while still providing high efficiency. The dihydropyrimidinone derivatives synthesized via the Biginelli reaction showed remarkable yields with our synthesized catalyst. With a short synthesis time, good yield, and especially being environmentally friendly, the catalyst that we offer is a great substance for reactions taking place during chemical synthesis. The results from analytical instruments such as FT-IR, EDX, ICP-MS, TGA, SEM, VSM, and ¹H-NMR, ¹³C-NMR spectra have shown that we have successfully synthesized the solid catalyst and dihydropyrimidinone derivatives with good yields, along with ensuring safety according to green chemistry criteria.