The cycloisomerization of β-, γ-, and δ-unsaturated Nacyl sulfonamides to N-sulfonyl lactams and imidates is reported. This transformation is effected in the presence of a Co III (salen) catalyst using t-BuOOH or air as the oxidant. The method shows good functional group tolerance (alkyl, aryl, heteroaryl, ether, N-Boc) and furnishes an underexplored class of cyclic building blocks. The strong solvent dependence of the transformation is investigated, and the synthetic versatility of the N-sulfonyl imidate product class is highlighted.