A series of bicyclopyrazolones were synthesized from the condensation reaction of methyl 4‐oxotetrahydro‐2H‐thiopyran‐3‐carboxylate with hydrazine derivatives in ethanol. All synthesized products were characterized by FT‐IR, 1H, and 13C NMR spectral data, elemental analyses, and mass spectrometry. The antibacterial and antifungal activities of these compounds were evaluated against Staphylococcus aureus and Bacillus subtilis as Gram‐positive bacteria, Escherichia coli and Pseudomonas aeruginosa as Gram‐negative bacteria, and the fungus Candida albicans. The results revealed that bicyclopyrazolones including an aryl or aryl sulfonyl group in the N‐2 position of the pyrazolone moiety are the most effective against all the microorganisms studied in this work.
