Intermolecular and Intramolecular α-Amidoalkylation Reactions Using Bismuth Triflate as the Catalyst

摘要

Bismuth(Ⅲ) triflate was found to promote the formation of stable cyclic N-acyliminium species in remarkable catalytic amounts (1 mol %). The α-amidoalkylation process seems to be effective in intermolecular and intramolecular manners leading to α-substituted lactams and heterocyclic systems containing azacycles, respectively. By comparing our results with those obtained with the classical Lewis acids as catalysts, it was evidenced clearly that the use of bismuth(Ⅲ) triflate had been efficient for nearly all α-acetoxy lactams we used, except for N-acyliminium precursors bearing a sulfur atom. Also, the process seems to be easy, general, and clean, having diastereoselectivity comparable to protocols using classical Lewis acids and resulting in the formation of polyheterocyclic systems in good to excellent yields (64-99% in acetonitrile as solvent).