Microwave-assisted solvent-free synthesis, Hirshfeld surface analysis and DFT studies of 1-(hydroxymethyl)-pyrazoles

A facile high-yield, solvent-free approach for the synthesis of a series of 1-(hydroxymethyl)-pyrazoles under microwave irradiation was developed for the first time. The structures of four pyrazoles compounds were characterised by a single-crystal X-ray diffraction, and showed interesting intermolecular O-H center dot center dot center dot N hydrogen bonding linking two pyrazoles molecules to form R22(10) dimer architectures. In additional, the intermolecular interactions in the crystal were investigated through the Hirshfeld surface analysis to understand the charac-teristics of the close contacts, and the 2D-fingerprint plot data exposed that a significant contributions to the crystal packing are from N center dot center dot center dot H/H center dot center dot center dot N contacts. The geometry optimization, electronic properties and energies level of HOMO, LUMO were performed by Density functional theory (DFT) calculations. Quantitative electro-static potential analysis (ESP) and independent gradient model based on Hirshfeld partition (IGMH) explained the active hydrogen bonding sites in four pyrazoles compounds and confirmed the hydrogen bonding modes in their crystal structure.

Automated summary

A facile high-yield, solvent-free approach for the synthesis of a series of 1-(hydroxymethyl)-pyrazoles under microwave irradiation was developed for the first time. The structures of four pyrazoles compounds were characterized and the interesting intermolecular O-H···N hydrogen bonding was found. Additionally, the crystal packing and hydrogen bonding modes were studied through analysis and calculations.