Preparation of pyrrolin-2-ones and 4,5-dihydrodipyrrin-1-ones by oxidation of α-formylpyrroles and α-formyldipyrromethanes with hydrogen peroxide

Various substituted α-formylpyrroles and -dipyrromethanes have been oxidized by hydrogen peroxide under mild conditions to give pyrrolin-2-ones (2) and 4,5-dihydrodipyrrin-1-ones (4) with concomitant loss of the formyl substituent, thus extending the scope of this oxidation to dipyrromethanes. This makes the reaction especially useful for the preparation of bile pigments, for which the pyrrolinones and 4,5-dihydrodipyrrinones constitute important synthons.