Crystalline salicylic acid as an efficient catalyst for ultrafast Paal-Knorr pyrrole synthesis under microwave induction

In this study, the viability of a wide range of crystalline aromatic and aliphatic carboxylic acids as organocatalysts has been investigated for solvent-free Paal-Knorr pyrrole synthesis under microwave activation. Among these potential catalysts, crystalline salicylic acid proved to be a remarkable catalyst because its efficiency remained high even under low microwave power irradiation or a shorter reaction time for the model reaction. The outstanding catalytic activity of salicylic acid allowed the Paal-Knorr cyclocondensation with a turnover frequency up to 1472 h(-1) which is unique in the context of a metal-free homogeneous catalysis. The attractive feature of this organocatalyst is its assistance in ultrafast pyrrole synthesis with no risk of metal contamination.

Automated summary

This study demonstrated the exceptional catalytic activity of crystalline salicylic acid as an organocatalyst in solvent-free Paal-Knorr pyrrole synthesis under microwave activation. It showed high efficiency even under low microwave power irradiation or shorter reaction times, and enabled ultrafast pyrrole synthesis with no risk of metal contamination.