Substituted Schiff bases (hydrazones) 5a-j have been prepared from the starting material 2-chloro pyridine-3-carboxylic acid 1 by a sequence of reactions like reaction with 2-amino-6-nitro benzothiazole (Ullamann condensation), thionyl chloride, hydrazine hydrate and different aromatic aldehydes. On cyclocondensation of 5a-j with thioglycolic acid in dry 1,4-dioxane furnished desired compounds 4-thiazolidinones 6a-j. The structures of all the synthesized compounds have been assigned on the basis of IR, 1H NMR, 13C NMR spectral data and elemental analyses. All the newly synthesized compounds were tested for their in vitro antimicrobial activity against several microbes. Some of the compounds showed significant antibacterial as well as antifungal activity.