PHOTO-OXYGENATION AND AUTOXIDATION OF DIPYRRYLMETHENES AND DIPYRRYLMETHANES

The dye‐sensitized photooxygenations of 4,4′‐diethyl‐3,5,3′5′‐tetramethyldipyrrylmethene and 4,4 ‐diethyl‐3,5,3′5‐tetramethyldipyrrylmethane have been investigated in neutral, basic and acidic methanol solution. Several photoproducts are common to the photooxygenation of both substrates. The dipyrrylmethene was detected as an intermediate in the photooxygenation of the dipyrrylmethane; however, it was determined not to be an important precursor to monopyrrole products. Autoxidations of the two dipyrrole compounds were also investigated and were found to be slower than the corresponding photooxygenation. Autoxidation and photooxygenation were both found to be faster in basic than in acidic methanol with the dipyrrylmethane faster than with the dipyrrylmethene in the same solvent. Copyright © 1979 Journal of Heterocyclic Chemistry