The Chemistry of Pyrrolic Compounds. LXIV. Intramolecular Cyclization of Butyric Acid Substituted Porphyrins: Petroporphyrins With Fused Seven-Membered Ring Systems

Abstract

The preparation of a series of porphyrins substituted with butyric acid side chains is described and efforts to achieve the intramolecular cyclization of this substituent are discussed. Attempts to prepare a stable spiro ketone by cyclization onto a β- pyrrolic carbon have not met with success but the synthesis of a seven- membered ring ketone by cyclization onto a meso -carbon has been completed. Reduction of this ketone has led to the synthesis of the petroporphyrin (1d). Some comments are offered concerning the origin of the isomeric petroporphyrin (19a) which bears a methylated six- membered ring sytem fused to the porphyrin macrocycle.