Nitrogen-embedded polycyclic compound with strong antiaromaticity and stability

The synthesis and isolation of a nitrogen-embedded polycyclic compound with strong antiaromaticity and stability was achieved for the first time by a research group at Ehime University. This result was published on October 2, 2019 in the

Journal of the American Chemical Society

.

Aromaticity is one of the most important concepts in chemistry, which has the influence on fundamental properties of cyclic conjugated compounds. In general, compounds with 4n+2 π electrons in the ring are stable due to their aromatic nature, and are widely used around us: from plastics to pharmaceuticals, and from dyes to organic electronics materials. On the other hand, antiaromatic compounds with 4n π electrons in the ring lack stability, and thus research on the synthesis and characterization of such compounds remains to be elucidated. In this report, an expedited approach toward a nitrogen-embedded antiaromatic compound with strong antiaromaticity and stability is presented. The new compounds were efficiently synthesized in just three steps from commercially available reagents via a substitution reaction and successive intramolecular Schooll and Vilsmeier-type reactions. Detailed investigation revealed its strong antiaromaticity and stability even in air.

Recently, polycyclic compounds have been studied as graphene-like molecules with a discrete structure. But compounds with aromaticity and antiaromaticity have been limited mainly to annulenes and porphyrins. This report presents the first nitrogen-embedded polycyclic compound with antiaromaticity. The easy access to such compounds enables not only the revealing of its fundamental properties but also its application to organic electronic materials.

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