Functionalized eight-membered lactams via [3,3] sigmatropic rearrangement of 2-azetidinone-tethered 1,5-dienes

The thermally induced [3,3] sigmatropic (Cope) rearrangement of cis-β-lactams 1 having alkenyl groups at both the C3 and C4 positions to yield new functionalized eight-membered lactams (tetrahydroazocinones) 2, in racemic as well as optically pure forms, is reported. This process involves a novel, concerted C3C4 bond breakage of the β-lactam nucleus helped by ring strain.