Newmonocyclicβ-lactams 4–6 were synthesized by a ketene-imine [2+2] cycloaddition reaction. The prepared monocyclicβ-lactams 4–6 were cleaved by ceric ammonium nitrate (CAN) to give NH-β-lactams 7–9. The NH-β-lactams were converted to N-sulfonyl β-lactams 10–21 by treatment with four different sulfonyl chlorides in the presence of Et3N and 4-N,N-dimethylaminopyridine (DMAP). Some of these monocyclic