A Möbius Aromatic [28]Hexaphyrin Bearing a Diethylamine Group: A Rigid but Smooth Conjugation Circuit

The reaction of [26]hexaphyrin with triethylamine in the presence of BF 3 ⋅OEt 2 and O 2 furnished a diastereomeric mixture of a diethylamine‐bearing [28]hexaphyrin as a rare example of a Möbius aromatic metal‐free expanded porphyrin. The Möbius aromaticity of these molecules is large, as indicated by their large diatropic ring currents, which are even preserved at 100 °C, owing to their internally multiply bridged robust structure with a smooth conjugation network. These molecules were reduced with NaBH 4 to give an antiaromatic [28]hexaphyrin, and were oxidized with MnO 2 to give aromatic [26]hexaphyrins, both through a Möbius‐to‐Hückel topology switch induced by a CN bond cleavage.