One-pot multicomponent synthesis in aqueous medium of 1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile and derivatives using a green and reusable nano-SiO2 catalyst from agricultural waste

Abstract

Nanosilica from wheat straw—an agricultural waste—was utilized as a novel and efficient heterogeneous catalyst for synthesis of bioactive pyrano[2,3-c]pyrazole derivatives via one-pot four-component reaction of various aryl aldehydes, hydrazine hydrate, ethyl acetoacetate, and malononitrile in aqueous medium at 80 °C. The nano-SiO2 extracted from wheat straw was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, particle size analysis, energy-dispersive X-ray (EDX) analysis, and scanning electron microscopy (SEM). All the synthesized pyrano[2,3-c]pyrazoles were characterized by FT-IR spectroscopy, electrospray ionization (ESI) mass spectroscopy (MS), 1H and 13C nuclear magnetic resonance (NMR), and elemental analysis. Additional features of this method include an efficient, rapid, and ecofriendly reaction process, easy workup, high yield, short reaction time, and recyclable green catalyst.