Cobalt-Catalyzed Cyclization of Unsaturated N -Acyl Sulfonamides: a Diverted Mukaiyama Hydration Reaction.

The cycloisomerization of β-, γ-, and δ-unsaturated N -acyl 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.