Magnetic carbon nanotube as a highly stable support for the heterogenization of InCl3 and its application in the synthesis of isochromeno[4,3‐c]pyrazole‐5(1H)‐one derivatives

In the present study, a novel magnetically retrievable catalytic system involving indium nanoparticles on magnetic carbon nanotube (Fe3O4‐CNT‐In) was synthesized and characterized using various techniques, such as Fourier transform‐infrared, thermogravimetric analysis, energy‐dispersive X‐ray analysis, vibrating‐sample magnetometry1, X‐ray diffraction, field emission‐scanning electron microscopy and inductively coupled plasma‐optical emission spectrometry. The catalytic activity of the synthesized nanocatalyst was evaluated in green synthesis of isochromeno[4,3‐c]pyrazole‐5(1H)‐one derivatives from the reaction of ninhydrin and arylhydrazones under solvent‐free conditions. The catalyst was magnetically separated from the reaction mixture using an external magnet and recovered for five cycles without an appreciable decrease in its catalytic efficiency. Performing the reactions in environmentally friendly and affordable conditions, the low catalyst percentage, high yield of products, short reaction times, large substrate scope and easy work‐up are the merits of this protocol. Furthermore, four of the synthesized isochromeno[4,3‐c]pyrazole‐5(1H)‐one derivatives are also new. An indium heterogeneous catalyst on magnetic carbon nanotube (Fe3O4‐CNT‐In) was prepared and used for synthesis of isochromeno[4,3‐c]pyrazole‐5(1H)‐one derivatives from ninhydrin and arylhydrazones under solvent‐free conditions. Reusability and stability tests demonstrated that the as‐prepared catalyst can be recycled with a negligible loss of its activity.