Acyl vs sulfonyl transfer in N-acyl β-sultams and 3-oxo-β-sultams

N-Acylsulfonamides usually react with nucleophiles by acyl transfer and C-N bond fission. However, the hydrolysis of N-acyl -sultams is a sulfonyl transfer reaction that occurs with S-N fission and opening of the four-membered ring. Similar to other -sultams, the N-acyl derivatives are at least 106-fold more reactive than N-acyl sulfonamides. 3-Oxo--sultams are both -lactams and -sultams but also hydrolyze with preferential S-N bond fission.