Triazino-1,2,4-[4,5-a] indoles. V. Etude du dioxo-1,4 tetrahydro-1,2,3,4 triazino-1,2,4-[4,5-a] indole

1,4-Dioxo - 1,2,3,4- tetrahydro- 1,2,4- triazino4,5-a] indole (1) was synthesized either by cyclising the N-carbethoxyhydraxizide of indole-2 carboxylic acid (4) or by alkaline rearrangement of 2-(2-indolyl)-5-oxadiazolone (6). The methylation reactions of the dilactam 1 were achieved with dimethyl sulfate or diazo-methane and afforded mixtures of O-methylated and N-methylated derivatives which were isolated and the structure of which were asigned. The tautomerism of dilactam 1 was studied using O-and N-methylated derivatives. The lactim-lactam structure 1a pre-ponderated in solution.