Expanded N-Confused Phlorin: A Platform for a Multiply Fused Polycyclic Ring System via Oxidation within the Macrocycle.

Novel interrupted π-conjugated macrocycles derived from expanded porphyrinoids were synthesized, and their unique reactivity was investigated in this work. The specific porphyrin analogs, so-called phlorins and isoporphyrins, possess a -sp methylene moiety, showing inner 3NH and 1NH pyrrolic cores, respectively, and extended near-infrared (NIR) absorption. Expanded N-confused pentapyrrolic phlorin analog bears an interrupted cyclic π-conjugated system that is featured by a distinct higher HOMO and a lower LUMO. Oxidation of allowed structural transformations through the expanded isoporphyrin-like species . One of the representative products is a spiro-carbon-bridged multiply N-fused product comprising a fused [5.6.5.7.6.5]-hexacyclic ring obtained by oxidation with 2,3-dichloro-5,6-dicyano--benzoquinone. When magic blue was used as the oxidant, an aromatic N-confused pentaphyrin was obtained via migration of one of the -phenyl groups to the β-position of the neighboring pyrrolic ring. By employing the flexible cavity of for metal coordination, Pd(II) complexation occurred with a specific oxygenation to give a bimetallic complex . In contrast to the rich oxidation reactions, reduction of with NaBH resulted in the regioselective nucleophilic hydrogen substitution reaction at the para position of one of the -CF groups. These results provide a practical approach for synthesizing novel interrupted or aromatic π-conjugated frameworks showing NIR absorptions.