Preparation of magnetized carrageenan-metformin as a new bio-inspired heterogeneous nanocatalyst for the synthesis of dihydropyrano[2,3- c]pyrazoles

Due to environmental concerns, there is a growing interest in the eco-friendly and reusable nanocatalysts. However, preparing a benign and reusable nanomaterial with high catalytic activity is an issue of challenge. A good strategy is the modification of polysaccharides with catalytically active species followed by magnetization. Therefore, we introduced a kappa-carrageenan (Carr) based nanocatalyst modified by metformin (Met) coated on Fe 3 O 4 nanoparticles (MNPs). After thorough physicochemical characterization, the as-synthesized Carr-Met-MNPs nanocomposites demonstrated a high activity as a multifunctional nanomaterial for the four-component domino synthesis of dihydropyrano [2, 3-c] pyrazole derivatives via condensation of hydrazine hydrate, ethyl acetoacetate, malononitrile, and aromatic aldehydes. The synergistic effect of sulfonic acid and amino groups can justify the high performance of Carr-Met-MNPs nanocomposites. These nanocomposites with properties including benign solvent system, improved activity, and easy recoverability (up to 5 runs) can be quite comparable to other heterogeneous and homogeneous catalyst systems. The heterogeneity of Carr-Met-MNPs nanocomposites was also appraised by a hot filtration test under optimum reaction conditions.