Green approach for the synthesis of pyranopyrazoles and hexahydroquinoline-3-carboxamides using unripe grape juice (verjuice) as catalyst

Abstract

Unripe grape juice (verjuice) as a natural catalyst was successfully applied to perform the one-pot reaction of aryl aldehydes, malononitrile, hydrazine hydrate and ethyl acetoacetate to synthesize pyranopyrazole derivatives in aqueous ethanol at room temperature in excellent yields. Furthermore, unripe grape juice catalyzed one-pot synthesis of hexahydroquinoline-3-carboxamide derivatives by the four-component reaction of arylaldehydes, dimedone, acetoacetanilide and ammonium acetate in high to excellent yield in ethanol at 70 ℃. The synthesized compounds were identified by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques and elemental analysis. An environmentally benign procedure, short reaction time, high yields and biocompatible natural catalyst are some advantages of this research.