Chart 1. (a) Synthesis of tetraoxa[8]circulene from α-naphthoquinone. (b) Synthesis of azatrioxa[8]circulene and diazadioxa[8]circulene from a dihydroxycarbazole precursor. (c) Synthesis of tetraaza[8]circulene from o-phenylene-bridged tetrapyrrole. (d) Synthesis of tetrathia- and tetraselena[8]circulenes from an octabromotetraphenylene precursor. (e) Synthesis of tetrathia[8]circulenes from a tetraboryltetrathienylene precursor (DDQ = 2,3-dichloro-5,6-dicyano-p-benzoquinone, chloranil = 2,3,5,6-tetrachloro-p-benzoquinone).
