The thiosemicarbazones (3 and 6) and N-arylidene cyanoacetohydrazide (12) were prepared and used as key intermediates for the synthesis of 4-thiazolidinones (4, 5, 7-9), thiazoles (10a,b and 11a-d) and thiazoline (13) derivatives. Treatment of 13 with a mixture of triethylorthoformate and acetic anhydride afforded thiazolo[5,4-d]pyrimidinone derivative (14). The newly synthesized compounds were characterized by IR, (1)H NMR and mass spectral studies. Representative compounds of the synthesized products were tested and evaluated as antimicrobial agents.