Synthesis and Biological Activity of Fused Heteropolycyclic Systems Containing an Indole Moiety

The synthesis of 4-amino-4H-[1,2,4]triazino[5,6-b]indole-3-thiol 1 via the reaction of isatin with thiocarbohydrazide in glacial acetic acid is described in this study. New fused heterotetracyclic nitrogen systems, such as [1,2,4,5]tetrazino[6',1':3,4][1,2,4]-triazino[5,6-b]indoles 4 and 6; [1,2,4]triazino[3',2':3,4][1,2,4]triazino[5,6- b]indole 8; [1,3,4]thiadiazolo[2',3':3,4][1,2,4]triazino[5,6-b]indoles 9, 11 and 12; pyrazolo[5',1':3,4]-[1,2,4] triazino[5,6-b]indole 16; and [1,3,4]thiadiazino[2',3':3,4][1,2,4]triazino[5,6-b]indoles 18, 20 and 23, were achieved by treating 1 with guanidine, thiosemicarbazide, thioformic acid hydrazide, glycine and CS2, in ethanolic ethoxide, triethyl orthoformate, ethyl cyanoacetate, ethyl chloroformate and dichloroacetic acid, respectively. The structures of the products were deduced from their elemental analyses and spectral data (IR, 1H-NMR and13C-NMR). The antimicrobial activity of some of the synthesized compounds was also determined.