Porphyrin Sythesis through Tripyrrins: An Alternative Approach

Article abstract of DOI:10.1021/jo00171a029

A new route for synthesis of unsymmetrically substituted porphyrins is described.The route follows the earlier approach through pyrromethanes, tripyrrin hydrobromides, and a,c-biladiene dihydrobromides, except that the pyrromethane intermediate is elongated in an initially "clockwise" direction to give a benzyl tripyrrincarboxylate.Various advantages over the tert-butyl tripyrrincarboxylates used in the earlier method (Scheme I) are discussed.The new route is demonstrated in the syntheses of five pure porphyrins required for other current studies.