Biphenylene-2,3-dione is a powerful reagent to build up cyclobutadiene-containing azapolyheterocycles. The target structures are formed in high yields through classical condensation of suitable aromatic diamines with the biphenylenedione. To achieve the title compound, the biphenylenedione is coupled with a diaminobenzothiadiazole derivative. Reductive cleavage of the thiadiazole ring and subsequent condensation with the biphenylenedione gives the title compound in which a central tetraazapentacene is flanked by two benzocyclobutadiene units. This compound is stable despite its extended π-system and its optical features are blueshifted in comparison to those of the symmetrical tetraazapentacene.
Keywords: aromaticity; azaheteropolycycle; condensation; cyclobutadiene; tetraazapentacene.
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