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This work reports the synthesis of aza-superbenzene and aza-supernaphthalene, indicating variable aromaticity in different oxidation states.
All-benzenoid polycyclic aromatic hydrocarbons or macrocycles usually display localized aromaticity. On the other hand, incorporation of quinoidal units into the skeleton could lead to effective electron delocalization and global (anti)aromaticity. In this work, fully π-conjugated macrocycle 1 and bismacrocycle 2 containing both para-quinodimethane and triphenylamine units are efficiently synthesized mainly through intermolecular Friedel-Crafts alkylation reaction. They can be considered as a tetraazasuperbenzene and a hexaazasupernaphthalene, respectively, due to their similar geometry and electronic structures to the benzene and naphthalene. X-ray crystallographic analyses reveal a largely planar geometry for both 1 and 2 and variable-temperature NMR measurements disclose slow dynamic processes owing to restricted ring flipping of the phenyl rings. 1 and 2 can be easily oxidized into higher-oxidation-state species. NMR and theoretical calculations indicate that 1
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Ma et al. (2024) studied this question.
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