An approach to the Paal-Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions

A facile synthesis of N-substituted pyrroles by the Paal-Knorr condensation has been accomplished using a simple procedure. Among different metal triflates screened, 1 mol % Sc(OTf)3 efficiently promoted the reaction in excellent yield (89-98%) under mild reaction conditions. Additionally, Sc(OTf)3 could be recovered easily after the reactions were completed and reused without evident loss of activity.