Synthesis of Aminocyclobutanes through Ring Expansion of N-Vinyl-β-Lactams

Both eight-membered enamide rings and fused [4.2.0]aminocyclobutane-containing delta-lactams can be accessed from N-vinyl-beta-lactams. The eight-membered rings are made through a [3,3] sigmatropic rearrangement. At elevated temperature, the eight-membered lactam undergoes electrocyclization to furnish fused cyclobutane delta-lactams in a diastereoselective manner.