Approaches to the synthesis of quinazolino[1,2,3]benzotriazinones

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Abstract
The synthesis of 1-(o-carboxamidophenyl)-3-aryl triazenes 12 and 15 (X = CONH2 and H) is described. Reaction of 3-(o-carboxamidophenyl)-1-(o-methoxycarbonylphenyl)-triazene (12) with piperidine in ethanol affords 2-[2-(piperidin-1-ylazo)phenyl]quinazolin-4(3H)-one (18); the formation of 18 in this reaction can only arise via the unstable quinazolino[1,2-c][1,2,3]-benzotriazinone 8 by triazine ring cleavage under the influence of piperidine. Attempted synthesis of the 4-iminotriazine 17, an isomer of the quinazolone 18, from the o-cyanophenyltriazene 20, resulted only in the formation of quinazolino[3,2-c][1,2,3]benzotriazin-8-one (6), an isomer of 8. The o-cyanophenyltriazene 20 undergoes spontaneous cyclisation, rearrangement, and further cyclisation.

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