Thiophene-Linked 1,2,4-Triazoles: Synthesis, Structural Insights and Antimicrobial and Chemotherapeutic Profiles

Abstract

The reaction of thiophene-2-carbohydrazide 1 or 5-bromothiophene-2-carbohydrazide 2 with various haloaryl isothiocyanates and subsequent cyclization by heating in aqueous sodium hydroxide yielded the corresponding 4-haloaryl-5-(thiophen-2-yl or 5-bromothiophen-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione 5a-e. The triazole derivatives 5a and 5b were reacted with different secondary amines and formaldehyde solution to yield the corresponding 2-aminomethyl-4-haloaryl-2,4-dihydro-3H-1,2,4-triazole-3-thiones 6a–e, 7a–e, 8, 9, 10a and 10b in good yields. The in vitro antimicrobial activity of compounds 5a–e, 6a–e, 7a–d, 8, 9, 10a and 10b was evaluated against a panel of standard pathogenic bacterial and fungal strains. Compounds 5a, 5b, 5e, 5f, 6a–e, 7a–d, 8, 9, 10a and 10b showed marked activity, particularly against the tested Gram-positive bacteria and the Gram-negative bacteria Escherichia coli, and all the tested compounds were almost inactive against all the tested fungal strains. In addition, compounds 5e, 6a–e, 7a–d and 10a exhibited potent anti-proliferative activity, particularly against HepG-2 and MCF-7 cancer cell lines (IC50 5a, 5b, 6a, 6d and 10a is also reported. Molecular docking studies of the highly active antibacterial compounds 5e, 6b, 6d, 7a and 7d showed a high affinity for DNA gyrase. Meanwhile, the potent anti-proliferative activity of compounds 6d, 6e and 7d may be attributed to their high affinity for cyclin-dependent kinase 2 (CDK2).

Keywords

• 1,2,4-triazoles
• thiophene
• antimicrobial activity
• anti-proliferative activity
• molecular docking
• single-crystal XRD