Efficient Regiospecific Conjugated Ring Fusion in N‐Confused Porphyrin

Acid‐catalyzed exocyclic ring formation in meso‐tetrakis(3′,5′‐dimethoxyphenyl)‐2‐aza‐21‐carbaporphyrin takes place regioselectively between the external carbon atom of the confused pyrrole and the ortho‐carbon atom of the adjacent meso‐aryl group. The ring fusion strongly alters the spectroscopic properties of the macrocycle, but its aromaticity is preserved, as shown by NMR spectroscopy as well as DFT calculations. A tendency to self‐associate is observed for partially protonated and nickel(II)‐metalated systems. A novel silver(I)‐bridged dimer is formed in the reaction of the fused carbaporphyrin with AgBF4. Cyclic voltammetry studies of this system indicate an interaction between the subunits. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)