Porphyrinogens and porphodimethenes, intermediates in the synthesis of meso‐tetraphenylporphins from pyrroles and benzaldehyde

The reaction between pyrroles and benzaldehyde in refluxing acetic acid gives meso‐tetraphenylporphins and chlorins. The initial condensations give a porphyrinogen which undergoes an acid catalyzed autoxidation to porphyrin via a porphodimethene. The chlorin is shown to be derived from the reduction of porphyrin.