Regioselective C-H Amination of Free Base Porphyrins Via Electrogenerated Pyridinium-Porphyrins and Stabilization of Easily Oxidized Amino-Porphyrins by Protonation.

Four free base aminoporphyrins were synthesized in two steps via regioselective anodic nucleophilic substitution with pyridine followed by ring opening of the electrogenerated pyridinium with piperidine. The X-ray crystallographic structure of the unstable 2-aminotetraphenylporphyrin was solved. Protonation of this latter compound leads to the stable diiminium porphyrin salt.