An Oxidant- and Catalyst-Free Electrooxidative Cross-Coupling Approach to Synthesize meso-Substituted Porphyrin Derivatives

The synthesis of porphyrin and chlorin derivatives has attracted significant attention due to their numerous applications. Herein, we report an environment friendly oxidant- and catalyst-free electrooxidative cross-coupling approach for multiple coupling reactions to synthesize meso C–N, C–O, and C–S substituted porphyrin and chlorin derivatives. For C–N cross-coupling reactions, diaminated porphyrins were obtained as the main products, while using 4-bromo-2,6-dimethyl aniline resulted in monoaminated product. Similarly, electrochemical catalysis of porphyrins with phenol and thiophene produced meso-disubstituted porphyrins in moderate yields under a smaller current. Chlorins were also applicable, and 20-substituted products were efficiently produced regioselectively. To the best of our knowledge, this work represents the first example of electrooxidative C–X cross-coupling of porphyrins and chlorins.