Magnetized metformin-functionalized carrageenan as a solid acid-base bifunctional nanocatalyst for the one-pot synthesis of dihydropyrano[2,3- c]pyrazoles

Abstract

Abstract In the current work we introduced a magnetic nanocatalyst with acidic-basic properties by coating Fe3O4 magnetic nanoparticles with kappa-carrageenan (Carr) and metformin (Met) moieties. The successful synthesis of Carr-Met-MNPs nanoparticles was verified by FT-IR, XRD, VSM, FESEM, EDX-mapping and TGA. The acidic-basic properties of Carr-Met-MNPs were studied by titration. The Carr-Met-MNPs nanoparticles demonstrated very good to excellent yields (88-94%) for the four-component domino synthesis of dihydropyrano [2, 3-c] pyrazoles via condensation of hydrazine hydrate, ethyl acetoacetate, malononitrile, and aromatic aldehydes in the aqueous ethanol as a benign solvent system. The synergistic effect of sulfonic acid and amino groups can justify the catalytic activity of Carr-Met-MNPs. Also, the catalyst can be magnetically recovered. Simplicity of catalyst synthesis, use of a benign solvent system, improved activity, and easy recoverability (up to 5 runs) is some of prominent advantages of the present catalyst system. The heterogeneity of Carr-Met-MNPs nanocomposites was also confirmed by a hot filtration test under optimum reaction conditions.