Azatrioxa[8]circulenes: Planar Anti-Aromatic Cyclooctatetraenes

We describe herein the first synthesis of a new class of anti‐aromatic planar cyclooctatetraenes: the azatrioxa[8]circulenes. This was achieved by treating a suitably functionalised 3,6‐dihydroxycarbazole with 1,4‐benzoquinones or a 1,4‐naphthoquinone. We fully characterised the azatrioxa[8]circulenes by using optical, electrochemical and computational techniques as well as by single‐crystal X‐ray crystallography. The results of a computational study (NICS) suggest that the central planar cyclooctatetraene is anti‐aromatic when the molecules are in neutral or oxidised states (2+), and that the corresponding dianions are aromatic. We discuss the aromatic/anti‐aromatic nature of the planar cyclooctatetraenes and compare them with the isoelectronic tetraoxa[8]circulenes. Planar cyclooctatetraenes: The first synthesis of a new class of anti‐aromatic planar cyclooctatetraenes is described: the azatrioxa[8]circulenes (see scheme). The azatrioxa[8]circulenes were fully characterised by using optical, electrochemical and computational techniques as well as by single‐crystal X‐ray crystallography. The aromatic/anti‐aromatic nature of the planar cyclooctatetraenes is discussed and compared with the isoelectronic tetraoxa[8]circulenes.