An efficient and simple approach for the synthesis of pyranopyrazoles using imidazole (catalytic) in aqueous medium, and the vibrational spectroscopic studies on 6-amino-4-(4′-methoxyphenyl)-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole using

We describe a one-pot four component synthesis of pyranopyroles from aryl aldehydes, ethyl acetoacetate, malononitrile and hydrazine hydrate in the presence of catalytic amounts of an organocatalyst imidazole in water as medium. A plausible mechanism for the formation of imidazole catalyzed pyranopyrazoles has been envisaged. This method is rapid, simple, provides products in good yield, and is eco-friendly. In addition, based on the optimized geometry, the frequency and intensity of the vibrational bands of 6-amino-4-(4′-methoxyphenyl)-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole were obtained by the density functional theory (DFT) calculations using 6-31G(d,p) basis set. The vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A simple and efficient synthesis of pyranopyrazoles is reported. ► Imidazole serves as an efficient oganocatalyst in water as reaction medium. ► Vibrational wave numbers and intensities were calculated at DFT level 6-31G(d,p) basis set. ► DFT calculations on 6-amino-4-(4′-methoxyphenyl)-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole. ► Fundamental bands observed in FT-IR and Raman spectra were assigned successfully.