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 BF₃?OEt₂ and O₂ 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 NaBH₄ to give an antiaromatic 28]hexaphyrin, and were oxidized with MnO₂ to give aromatic 26]hexaphyrins, both through a Möbius‐to‐Hückel topology switch induced by a C? N bond cleavage.