Synthesis and antibacterial activity of new hybrid derivatives of 5-sulfamoyl-1H-indole and 4-thiazolidinone groups

The synthesis of a series of new 3-phenyl-5-sulfamoyl-N-(7/8/9-(non)substituted-3-oxo-1-thia-4-azaspiro[4.4]non/[4.5]dec-4-yl)-1H-indole-2-carboxamide derivatives and their subsequent testing for antibacterial activity is described in this paper. 4-Sulfamoylbenzenediazonium chloride was synthesized from diazotization of sulfanilamide and sodium nitrite in the presence of HCl and was further allowed to condense with ethyl 2-benzylacetoacetate to produce ethyl 2-benzyl-2-(4-sulfamoylphenyl)hydrazonoacetate. This compound was cyclized to ethyl 5-sulfamoyl-3-phenyl-1H-indole-2-carboxylate employing the Fischer-indole procedure. The reaction of ethyl 5-sulfamoyl-3-phenyl-1H-indole-2-carboxylate with hydrazine hydrate yielded sulfamoyl-3-phenyl-1H-indole-2-carbohydrazide. Through a cyclization process, the spirothiazolidinone derivatives were obtained from the reaction of suitable cyclic ketones with 5-sulfamoyl-3-phenyl-1H-indole-2-carbohydrazide in the presence of thioglycolic acid/thiolactic acid. Structural elucidation of the novel compounds was achieved with the help of UV, IR, ¹H NMR, HSQC, ESI–MS, and as well as elemental analysis. Among all the synthesized compounds tested, four compounds displayed the most promising antibacterial activity. The influence of the substituents and their positions on the antibacterial activity was evaluated. Graphic abstract: