Synthesis of 3-amino-5H-1,2,3-triazino[5,4-b]indol-4-one. New compounds with blood platelet antiaggregation activity

Starting with 3-aminoindole-2-carbohydrazide 1 a series of arylidene hydrazones 2 was obtained with good yields (79–85%). Upon treating 2 with nitrous acid a series of 3-arylidineamino-5H-1,2,3-triazino5,4-b]indol-4-ones 3 was obtained (80–86%). The reaction of 4-methoxybenzylidene derivative 3e with hydrazine hydrate, in ethanol, gave 3-amino-5H-1,2,3-triazino5,4-b]indol-4-one 4 (64%). However, by treating 3e in boiling hydrate, 3-aminoindole-2-carbaldehyde azine 5 was obtained (44%). By boiling 1 in N,N-dimethylformamide, 3-amino-5H-pyrimido5,4-b]indol-4-one, 6 was obtained (52%).