Synthesis and Properties of 5,15‐Dioxaporphyrin Bearing Various meso‐Aryl Substituents

Herein, a scope of meso‐substituents for the synthesis of 5,15‐dioxaporphyrins (DOPs), a novel antiaromatic porphyrinoid, was investigated. DOPs with various types of aryl substituents were synthesized by nucleophilic aromatic substitution reaction of nickel bis(α,α’‐dibromodipyrrin) complexes bearing corresponding meso‐aryl substituents and subsequent intramolecular annulation reaction of β‐hydroxy‐substituted intermediates. Using a copper dipyrrin complex instead of nickel complexes, a copper complex of DOP was synthesized for the first time. The meso‐substituents did not significantly alter the antiaromaticity of DOPs but affected crystal packing diagrams and oxidation behaviors; DOPs with less sterically hindering para‐substituted phenyl or 2‐thienyl substituents formed mutual stacking in the crystal structures, whereas the covalently β‐β linked dimer species was generated during the electrochemical oxidation of those kinds of DOPs.