Green synthesis of tetrahydrobenzo[b]pyrans, pyrano[2,3-c]pyrazoles and spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles catalyzed by nano-structured diphosphate in water

Abstract

A green and recoverable nano-structured diphosphate (Na₂CaP₂O₇) was synthesized and fully characterized using FT-IR spectra, X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analysis. The nanostructured catalyst has been successfully used as reusable nanostructured catalyst for green, simple and efficient synthesis of tetrahydrobenzo[b]pyrans, pyrano[2,3-c]pyrazoles and spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles in aqueous media. The catalyst shows environmentally benign character, which can be easily prepared, stored, and recovered several times without obvious significant loss of catalytic activity.