Aza[10]annulene: Next Higher Aromatic Analogue of Pyridine.

The aza[10]annulene isomers (CH)(9)N derived from "twist", "heart", "naphthalene-like", and "azulene-like" [10]annulenes by replacement of a CH group by nitrogen were investigated at the CCSD(T)/DZd//B3LYP/6-311+G level of theory. Except for the twist structure, all aza[10]annulenes studied were found to be aromatic. As the transannular repulsion is reduced in the aza[10]annulenes, the aromatic isomers become competitive energetically with the twist form.