Synthesis of functionalized pyrazolopyran derivatives: comparison of two-step vs. one-step vs. microwave-assisted protocol and X-ray crystallographic analysis of 6-amino-1,4-dihydro-3-methyl-4-phenylpyrano[2,3-c]pyrazole-5-carbonitrile

Abstract

A library of pyrazolopyran heterocycles was synthesized first by the traditional heating techniques using two-step and one-step procedures and then by microwave-assisted (MWA) multicomponent condensation of ethyl acetoacetate, hydrazine, malonodinitrile and a variety of substituted aldehydes. A comparison of the foregoing methods was first done based on the yields and then based on the time taken for the completion of the reactions. It was found that although the traditional methods gave slightly better yields, the MWA syntheses lead to substantial reduction in reaction timings. The title compound crystallizes in the triclinic crystal system with space group P–1. The crystal structure as elucidated by X-ray diffraction methods shows the presence of different intermolecular interactions, and the nature and energetics associated with these interactions have been characterized using PIXEL software.