Green synthesis of novel 5-amino-bispyrazole-4-carbonitriles using a recyclable Fe(3)O(4)@SiO(2)@vanillin@thioglycolic acid nano-catalyst

Bis(thioglycolic acid)-vanillin (2,2'-(((4-hydroxy-3-methoxyphenyl)methylene)bis(sulfanediyl))diacetic acid)-functionalized silica-coated Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4)@SiO(2)@vanillin@thioglycolic acid MNPs) were synthesized and characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis/differential thermogravimetry (TGA-DTG), X-ray powder diffraction (XRD), X-ray spectroscopy (EDX), vibrating sample magnetometry (VSM), zeta potential measurements and Fourier transform infrared spectroscopy (FT-IR). The ensuing MNPs offer an environmentally friendly procedure for the synthesis of novel 5-amino-pyrazole-4-carbonitriles via a three-component mechanochemical reaction of synthesized azo-linked aldehydes or synthesized pyrazolecarbaldehydes, malononitrile, and phenylhydrazine or p-tolylhydrazine adhering to the green chemistry principles; products were generated expeditiously in high yields. The catalyst could be quickly recovered and reused for six cycles with almost consistent activity. The structures of the synthesized 5-amino-pyrazole-4-carbonitrile compounds were confirmed by (1)H NMR, (13)C NMR, and FTIR spectra and elemental analyses. This new procedure has notable advantages such as operational simplicity, excellent yields, short reaction time, easy work-up, eco-friendliness and nontoxic catalyst. Also the catalyst can be easily recovered by an external magnetic field and reused for six consecutive reaction cycles without significant loss of activity.