Ruthenium Complex-Catalyzed N-Heterocyclization. Syntheses ofN-Substituted Pyrroles and Pyrrolidines from 1,4-Diols and Primary Amines

Abstract 2-Butyne-1,4-diol reacts with aliphatic amines in the presence of a catalytic amount of [RuCl2(PPh3)3] at 150 °C to give N-alkylpyrroles in good yields. 1,4-Butanediol reacts with aromatic or aliphatic amines to give N-substituted pyrrolidines in excellent yields; [RuCl2(PPh3)3] and [RuCl3·nH2O–3PBu3] are the best catalysts for aromatic and aliphatic amines, respectively. The reaction of 2-butene-1,4-diol with alkyl amines gives a 1:1 mixture of N-substituted pyrroles and pyrrolidines in high yield.