Selective meso-monobromination of 5,15-diarylporphyrins via organopalladium porphyrins

The selective meso-monobromination of 5,15-diarylporphyrins is difficult to achieve and extensive chromatography is required to obtain pure products. A sequence of (i) dibromination, (ii) selective monoinsertion of [Pd(dppe)] [dppe = 1,2-bis(diphenylphosphino)ethane] and (iii) hydrodepalladation using methanolic base affords pure monobromoporphyrins in typically ≥60% overall yield without isolation of the organopalladium porphyrin. Monobromo derivatives of even highly lipophilic 5,15-diarylporphyrins are thus readily available without tedious, expensive and environmentally undesirable chromatography.