Paal-Knorr Pyrrole Synthesis Catalyzed by Silica Sulfuric Acid

Significance

A simple and efficient method for the preparation of pyrroles from primary amines and γ-diketones by using silica sulfuric acid (SSA) as a heterogeneous acid catalyst was described. The reaction of primary amines with 2,5-hexane­dione in the presence of the silica sulfuric acid under solvent-free conditions gave the corresponding substituted pyrroles (65-98% yield, 2-120 min). The reaction conditions were applicable to di- or triamino substrates to afford bipyrrole or tripyrrole compounds.