Investigation of the reactions of fluorine containing 3-hydrazino-5H-1, 2, 4-triazino[5, 6-b]indoles with ethyl acetoacetate. Synthesis of some novel tetracyclic ring systems

Novel tetracyclic ring systems viz. 3-methyl-1-oxo-12H-1, 2, 4-triazepino3′,4′:3, 4]1, 2, 4]triazino5, 6-b]indole ( 4a ) and 3-methyl-5-oxo-12H-1, 2, 4-triazepino4′,3′:2, 3]1, 2, 4]triazino5, 6-b]indole ( 5a ), having angular and linear structures respectively, were synthesized by the cyclization of 3-oxobutanoic acid 5H-1, 2, 4-triazino-5, 6-b]indole-3-yl]hydrazone ( 3a ). However, cyclization of 3b (R = CH_a, R¹ = R² = H) afforded the angular product 4b exclusively. Moreover, cyclization of 3c (R = R³ = H, R¹ = F) yielded 7-fluoro-1-0xo-10H-1, 3-imidazo2′,3′:3, 4]1, 2, 4]triazino5, 6-b]indole ( 6c ) and 7-fluoro-3-oxo-10H-1, 3-imidazo3′,2′:2, 3]1, 2, 4]triazino-5, 6-b]indole ( 7c ) instead of the expected triazepinone derivatives. Compound 3d (R = R¹ = H, R² = CF₃) also gave an imidazole derivative but only one angular product was obtained. In all these reactions, formation of the angular product involving cyclization at N-4 is favoured. Characterization of these products have been done by elemental analyses, ir, pmr, ¹⁹F nmr and mass spectral studies.