Synthesis and antibacterial activity of 4-aryl-2-(1-substituted ethylidene)thiazoles

Abstract

(E)-4-Aryl-2-[2-(1-substituted ethylidene)hydrazinyl]thiazoles and (Z)-3-substituted-4-aryl-2-[(E)-(1-phenylethylidene)hydrazono]-2,3-dihydrothiazoles were synthesized by the reaction of (substituted ethylidene)hydrazinecarbothioamides with ω-bromoacetophenones. The characterization of this new class of compounds was performed using different spectroscopic tools. The structure of (Z)-3-benzyl-4-(4-bromophenyl)-2-[(E)-(1-phenylethylidene)hydrazono]-2,3-dihydrothiazole 6e was unambiguously confirmed by single-crystal X-ray crystallography. Compounds 5a-e, 5i, 6e, 6g, and 6i were screened for their in vitro antibacterial activity against different strains of microorganisms; most of the tested compounds exhibited promising antibacterial activity against some organisms compared to ciprofloxacin and sulbactam penicillin. Compounds 5e, 5i, 6e, 6g, and 6i exhibited several-fold significant antibacterial activity against the Gram-positive bacteria Staphylococcus aureus, better than ciprofloxacin, with minimum inhibitory concentration values ranging from 0.05 to 0.4 µg/mL. The rest of the tested compounds gave significant antibacterial activities against different Gram-negative bacterial strains.

Keywords: (Substituted ethylidene)hydrazinecarbothioamides; Antibacterial activity; Heterocyclizations; Thiazole derivatives; ω-Bromoacetophenones.