Porphyrins. II. The synthesis of porphyrins from 2-aminomethylpyrroles

Abstract

Benzyl 5-formyl-3,4-dimethylpyrrole-2-carboxylate oxime (VI; R = COOCH₂Ph) has been reduced and treated with cupric acetate to yield copper octamethylporphin in 20% yield. Copper octaethylporphin was obtained in similar yield from 2-formyl-3,4-diethylpyrrole oxime (VII). The porphyrins are also obtained, in much smaller yield, following acid-catalysed condensation; a by- product formed under these latter conditions is probably a biladiene. Attempts to prepare meso-substituted porphyrins by similar treatment of the oximes of 2-acetyl- and 2-benzoyl-pyrroles were unsuccessful.