Spirooxindole-fused pyrazolo pyridine derivatives: NiO–SiO₂ catalyzed one-pot synthesis and antimicrobial activities

We describe here a one-pot synthesis of 13 spirooxindole-fused pyrazolo pyridine derivatives using NiO–SiO₂ catalyst via three-component reaction of isatin, 5-amino-3-methylpyrazole, and malononitrile. This multicomponent one-pot protocol also features shorter reaction time, good yield, and simple work-up using a recoverable and reusable solid acid heterogeneous catalyst. The NiO–SiO₂ catalyst was characterized using different instrumental techniques such as X-ray diffraction study, surface area analysis, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-DRS (diffuse reflectance spectroscopy), and energy dispersive X-ray analysis (EDX). The new compounds were tested for in-vitro anti-microbial activity.