Tetrahydrodipyrazolopyridine covalently immobilized on silica-coated magnetic nanoparticles as a basic heterogeneous catalyst for multicomponent synthesis of dihydropyrano[2,3-c]pyrazole derivatives and Knoevenagel condensation.

In this study, a novel magnetic nanocomposite, Fe₃O₄@SiO₂@Tetrahydropyrazolopyridine (THPP), was synthesized through a multistep surface-functionalization process and thoroughly characterized using FT-IR, XRD, UV-vis, TGA, FE-SEM, EDS, and elemental mapping techniques. The catalyst comprises a magnetic Fe₃O₄ core, a silica shell for chemical stability, and an outer THPP layer providing active catalytic sites. This hybrid structure was evaluated for its catalytic performance in Knoevenagel condensation, Michael addition, and multicomponent reactions for the efficient synthesis of 2-benzylidene malononitriles and pyranopyrazole derivatives under mild conditions. The reactions proceeded with high yields (up to 96%), short reaction times (as low as 5 min), and excellent selectivity. Green chemistry metrics, including atom economy, E-factor, reaction mass efficiency, and turnover frequency, demonstrated the eco-friendly and efficient nature of the method. Furthermore, the catalyst was easily recoverable magnetically and retained high activity over five consecutive cycles, underscoring its reusability and practical potential for sustainable organic synthesis.