Synthesis of N21,N22-etheno-bridged porphyrins by the reactions of cobalt porphyrins with alkynes in the presence of iron(III) salts

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 N 21 , N 22 (etheno-bridged porphyrins through the oxidative cobalt-to-nitrogen shift of the vinylic carbon when treated with excess FeCl 3 . Cobalt(III) prophyrin π cation radicals with a weakly coordinating axial ligand reacted smoothly with diphenylacetylene directly to afford the N 21 , N 22 -etheno-bridged porphyrin in good yields