Synthesis of fused heteropolycyclic systems containing an indole moiety

New fused heterocyclic systems containing the indole moiety with 1,3,4-thiadiazolo-, 1,3,4-thiadiazino-, 1,2,4-triazino-, pyridazino-, pyrimido-, imidazo-, 1,3-thiazolo- and pyrazolo-fusion have been synthesised starting from reactions of isatin-3-thiohydrazone, 1-(N-phenylbenzimidoyl)isatin and isatin-3-cyanoacetic acid hydrazone with a,p-bifunctional oxygen, halogen and nitrogen reagents.