The ketals or enol ethers of 1, 5-azidoketones were converted into lactams using a two- stage process. Treatment of the ketals and enol ethers with acid (trifluoroacetic acid, triflic acid, or trimethylsilyl triflate) afforded an oxonium ion which reacted with the tethered azide to give a 1, 1-azido-alkoxy intermediate. Bond reorganization led to an iminium ether that was reacted with sodium iodide in acetone to expose the amide products. Seven ...