Reversible Redox Reaction Between Antiaromatic and Aromatic States of 32π‐Expanded Isophlorins

Abstract

32π‐antiaromatic expanded isophlorins with a varying number of thiophene and furan rings adopt either planar, ring‐inverted, or twisted conformations depending on the number of furan rings in the macrocycle. However, they exhibit identical reactivity with respect to their oxidation to aromatic 30π‐dicationic species under acidic conditions. These 32π‐antiaromatic macrocycles can also be oxidized with [Et3O+SbCl6−]and NOBF4 to generate dications, thus confirming ring oxidation of macrocycles. Furthermore, they can be reduced back to their parent 32π‐antiaromatic state by triethylamine, Zn, or FeCl2. Single‐crystal X‐ray diffraction analysis confirmed a figure‐eight conformation for a hexafuran system, which opens to a planar structure upon oxidation.