Brønsted Acid-Catalyzed Intramolecular Hydroamination of Protected Alkenylamines. Synthesis of Pyrrolidines and Piperidines

reaction: see text. The cyclization of aminoalkenes bearing an electron-withdrawing group on the nitrogen atom was catalyzed by triflic or sulfuric acid in toluene. Pyrrolidines and piperidines were formed in excellent yields. N-phenylanilides also underwent cyclization to form gamma-lactams.