2-Thioxo-4-thiazolidinones (3a,b) were achieved by cyclocondensation of isothiocyanatosulfonamides (1a,b) with sulfanylacetic acid at reflux temperature in dioxane in the presence of triethylamine. Compound (3a) was exploited to synthesize the versatile hitherto unknown 2-thioxo-4-thiazolidinones (5-10) via its reaction with some electrophiles. Cyclization of 4,4'-diisothiocyanate diphenylsulfone (11) with sulfanylacetic acid furnished 4,4'-bis(2-thioxo-4-thiazolidinone-3-yl)diphenylsulfone (12) which on treatment with excess 4-methoxybenzaldehyde in refluxing dioxane in the presence of piperidine yielded the bisbenzylidene derivative (13). The novel synthesized compounds were characterized by IR, (1)H NMR and mass spectral studies. All the synthesized compounds were screened in vitro for their antibacterial and antifungal activities.