One-pot synthesis of correlates by cobalt catalyzed cyclization of formylpyrroles

Article abstract of DOI:10.1016/0020-1693(95)04747-6

2-Formylpyrroles react in the presence of cobalt ions to afford a mixture of porphyrin and corroie cobalt complexes. This is the first example of a single step synthesis of meso-unsubstituted corroie from a monopyrrole. When 3-ethyl-4-methyl-2-formylpyrrole-5-carboxylic acid was used as starting material, Co(Etioporphyrin-I) and a mixture of cobalt correlates were obtained. Chromatographic separation and detailed analysis of the ¹H NMR of these compounds allowed their identification as two different etio-like corroles. A possible reaction pathway, explaining their formation is reported. Metals different from cobalt gave only the corresponding porphyrin complex (Ni, Cu). No cyclization at all was observed in the presence of Mn or Rh.