Oxidative Cyclization of Chalcones in the Presence of Sulfamic Acid as Catalyst. Synthesis, Biological Activity, and Thermal Properties of 1,3,5-Trisubstituted Pyrazoles

Abstract

1-Aroyl-3,5-diaryl-1H-pyrazoles were synthesized by oxidative cyclization of chalcones with benzohydrazide and 4-nitrobenzohydrazide using sulfamic acid as a catalyst. The corresponding chalcones were prepared by condensation of aromatic aldehydes with acetophenones in PEG-400 in the presence of potassium hydroxide. Some representative features of the proposed procedure include exceptional regioselectivity, comparatively short reaction time, operational simplicity, and no need of external oxidant. The synthesized pyrazole derivatives were screened as antibacterial agents against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella typhi by the agar well diffusion method. Attempts were made to compute specific heat capacity of the synthesized pyrazole derivatives as a function of temperature using TGA–DSC in order to avail thermodynamic database for these biologically relevant heterocycles.