The title compounds (7a-f), (8a-f) and (9a-f) have been prepared from chalcones (6a-f) having striazine nucleus. These chalcones on cyclisation with hydroxyl amine hydrochloride in the presence of alkali give isoxazoles (7a-f). Chalcones (6a-f) on condensation with thiourea and urea in the presence of alkali give pyrimidinthiones (8a-f) and pyrimidinones (9a-f) respectively. Structures of newly synthesised compounds were established on the basis of their elemental analysis, IR and 1H NMR spectral data. All the synthesised compounds have been screened for their antibacterial activity.