DABA MNPs: a new and efficient magnetic bifunctional nanocatalyst for the green synthesis of biologically active pyrano[2,3-c]pyrazole and benzylpyrazolyl coumarin derivatives

Abstract

In this work, a new core–shell magnetic silica nanocatalyst functionalized with 3,4-diaminobenzoic acid (Fe₃O₄@SiO₂@PTS-DABA) was successfully prepared and characterized using different spectroscopic methods or techniques including FT-IR, FE-SEM, VSM, XRD, EDS and TGA. The Fe₃O₄@SiO₂@PTS-DABA catalyst was applied, as a magnetically recoverable catalyst, for the synthesis of biologically active dihydropyranopyrazole and benzylpyrazolyl coumarin derivatives. These derivatives were prepared in the presence of Fe₃O₄@SiO₂@PTS-DABA via a four-component reaction with yields of more than 90% under mild conditions. The Fe₃O₄@SiO₂@PTS-DABA nanocatalyst is easily prepared from commercially available, lower toxicity and thermally stable precursors through a cost-effective, highly efficient and environmentally friendly procedure. It has a long life and can be reused for several catalytic cycles without significant loss of the catalytic activity. Finally, a possible mechanism is proposed for the preparation of dihydropyranopyrazole and benzylpyrazolyl coumarin derivatives in the presence of the Fe₃O₄@SiO₂@PTS-DABA multifunctional magnetic catalyst. The structure of the products was identified by melting point measurement as well as FT-IR and ¹H NMR spectroscopic methods.