Peri-Heterocycles with Six-Membered Heteroring and Three Heteroatoms

Peri-Heterocycles with Six-Membered Heteroring and Three Heteroatoms 

As shown in Section II,C,l,b, photolysis or thermolysis of l-azido-8-arylazonaphthalenes gives rise to heterocyclization of these compounds, resulting in a mixture of mesoionic derivatives of naphtho[rf ]triazine 233 

The reaction of 9-amino- 1-phenaleneimine 453 with thiony(aniline results in the corresponding thiadiazine 5-oxide 454, which is protonated in sulfuric acid and then dehydrated to give phenaleno[c /]-2,l,3-thiadiazi-nium salt 455 (81JOC675). Salt 455 was not isolated in a crystalline state, 

The most interesting compounds described in this paragraph are meso-ionic naphtho[ te]triazines 457 (X = NR) and naphtho[rf ]-2,1,3-thia-diazines 457 (X = S), since these derivatives are disposed to undergo [12 + 2], cycloaddition in reactions with olefinic compounds. For instance, the reaction with acetylenedicarboxylates gives rise to adducts 458, which are dehydrogenated spontaneously to the new heteroaromatic systems 459 with the aromatic 147r-electron contour [75JCS(PI)556]. 

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