Studies on Condensed Triazines as Chemotherapeutic Agents,II. Synthesis of 1,2,4-Triazino[5,6-b]indoles and Related Compounds

1,2,4-Triazino[5,6-b]indoles and their derivatives are prepared by the cyclisation of isatin 3-thiosemicarbazone (1) followed by condensation and displacement reactions. Condensations of 3-hydrazino-1,2,4-triazino[5,6-b]indole (4) with ethoxymethylenemalononitrile, ethyl ethoxymethylenecyanoacetate, acetylacetone and methyl bis(methylmercapto)methylenecyanoacetate yield the corresponding 3-pyrazolo-1,2,4-triazino[5,6-b]indoles 6–9. The hydrazine 4 is further transformed into the higher heterocycles 10–12 on reaction with formic, acetic or nitrous acids.