Novel organocobalt(III) porphyrins with an alkyne inserted into an N-Co bond of diaquo(porphyrinato)cobalt(III) perchlorates could be isolated by using dimethyl acetylenedicarboxylate and methyl propiolate. These complexes were converted into N21,N22-etheno-bridged porphyrins through the oxidative cobalt-to-nitrogen shift of the vinylic carbon when treated with excess FeCl3. Cobalt(III) porphyrin pi-cation radicals with a weakly coordinating axial ligand reacted smoothly with diphenylaceylene directly to afford the N21,N22-etheno-bridged porphyrin in good yields. Vacancy in the axial coordination site of the Co(III) porphyrin pi-cation radical is crucial for the N-alkylation to take place. Thus, N21,N22-etheno-bridged octaethylporphyrins (OEP) and meso-tetraphenylporphins (TPP) have been synthesized conveniently in yields of 44-90% by the treatment of the Co(II) porphyrins with various alkynes (acetylene, 1-hexyne, propargyl alcohol, 2-butyne-1,4-diol, phenylacetylene, diphenylacetylene, di-o-tolylacetylene, methyl propiolate, and dimethyl acetylenedicarboxylate) in the presence of ca. 5 equiv of ferric salts at room temperature.