Synthesis, characterization, crystal structure, Hirshfeld surface analysis, antioxidant properties and DFT calculations of a novel pyrazole derivative: Ethyl 1-(2,4-dimethylphenyl)-3-methyl-5-phenyl-1H-pyrazole-4-carboxylate

Abstract

An effective route for the direct synthesis of substituted pyrazole through 3+2 annulation method was described. (E)-ethyl 2-benzylidene-3-oxobutanoate was prepared from ethyl acetoacetate and benzaldehyde via Knoevenagel approach. The cyclocondensation reaction of (E)-ethyl 2-benzylidene-3-oxobutanoate with phenylhydrazine hydrochloride in acetic acid (30%) medium under reflux conditions produced directly ethyl 1-(2,4-dimethylphenyl)-3-methyl-5-phenyl-1H-pyrazole-4-carboxylate and was characterized using spectroscopic methods viz NMR, mass, UV-Vis, and CHN analysis. The compound obtained was crystallized using methyl alcohol solvent by slow evaporation method and the 3D molecular structure was confirmed using single crystal X-ray diffraction studies. The crystal structure is stabilized by intermolecular hydrogen bond of the type C-H•••O and π•••π stacking interactions. Further, the calculated 1H-NMR, TD-SCF, HOMO/LUMO, MEP, Hirshfeld surface and Mulliken population analysis were compared with the experimentally analyzed data. The optimized theoretical structure parameters are in good agreement with the experimental X-ray structures. The compound was evaluated in vitro for its antioxidant susceptibilities through DPPH and hydroxyl radical scavenging methods.