Synthesis and biological evaluation of some heterocyclic scaffolds based on the multifunctional N-(4-acetylphenyl)-2-chloroacetamide

The chloroacetamide derivative, 1, was used as a versatile precursor for the synthesis of various types of N-aryl-2-(benzothiazol-2-ylthio)acetamide derivatives. The reaction of 1 with 2-mercaptobenzothiazole followed by condensation reaction of the produced sulfide with phenylhydrazine, 2-cyanoacetohydrazide, and/or thiosemicarbazide furnished the conforming condensation products, 4, 7, and 10, respectively. Treatment of the phenylhydrazone product, 4, with Vilsmeier formylation reagent (POCl₃/DMF) yielded the corresponding 4-formylpyrazole derivative, 5. The thiosemicarbazone product, 10, was reacted with ethyl bromoacetate to furnish the thiazolin-4-one derivative, 11. The substitution reactions of chloroacetamide derivative, 1, with 2-mercapto-4,6-dimethylnicotinonitrile and 6-amino-2-mercaptopyrimidin-4-ol, were explored to identify the sulfide products, 14 and 17. Cyclization of 14 into its corresponding thieno[2,3-b]pyridine compound, 15, was performed using sodium ethoxide. The thiosemicarbazone, 10, and sulfide derivative, 14, were found to be the most potent antibacterial compounds against Escherichia coli and Staphylococcus aureus, exhibiting growth inhibitory activities of 80.8% and 91.7%, respectively. Moreover, the thiosemicarbazone, 10, displayed the most significant antioxidant activity with inhibitory activity of 82.6%, which comes close to the antioxidant activity of L-ascorbic acid.