Chlorothiophene-Substituted N-Phenylpyrazolines: Synthesis, Anticancer Evaluation, and Computational Insight into COX-2 Inhibition.

Cancer remains a leading cause of mortality worldwide, highlighting the need for novel anticancer agents. Pyrazoline derivatives have attracted considerable interest due to their structural flexibility, enabling modifications, including bioisosteric replacement, to enhance anticancer potential. In this study, eight N-phenylpyrazoline analogs bearing chlorothiophene moieties were synthesized via cyclocondensation of chalcone intermediates with phenylhydrazine, yielding 59%-94%. Structural characterization was confirmed using ATR-IR, GC-MS, 1H-, and 13C-NMR analyses. The synthesized derivatives (2a-2h) were assessed for cytotoxicity against the T47D, MCF7, and WiDr cancer cell lines, along with normal Vero cells, using the MTT assay. Selectivity was determined by comparing cytotoxic effects on cancer versus normal cells. Among the compounds, 5-(benzo[d][1,3]dioxol-5-yl)-3-(5-chlorothiophen-2-yl)-1-phenyl-4,5-dihydro-1H-pyrazole (2g) exhibited the most potent cytotoxicity against WiDr cells (IC50 = 19.63 µg/mL) and the highest selectivity index (SI = 665.88). Molecular docking revealed strong binding affinities of compound 2g to COX-2 (-10.5 kcal/mol), supported by favorable pharmacokinetic properties.