Reversion of Paal-Knorr Synthesis: A New Strategy for Ring-Opening and N-Substituent Change in 1H-Pyrroles

1H-Pyrroles were converted into 1,4-dicarbonyl compounds, and then into 1H-pyrroles with a different N-substituent by heating at 110 °C under nitrogen in 0.3 M sodium citrate buffer, pH 3, and in the presence of alkyl or aryl amines. The new pyrroles were obtained in low to very high yields depending upon the pH, the reaction time, the initial pyrrole and amine involved, and the proportion between both reagents.