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

The cycloisomerization of beta-, gamma-, and delta-unsaturated N-acyl sulfonamides to N-sulfonyl lactams and imidates is reported. This transformation is effected in the presence of a CoIII(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.

Automated summary

The cycloisomerization of beta-, gamma-, and delta-unsaturated N-acyl sulfonamides to N-sulfonyl lactams and imidates using a CoIII(salen) catalyst with t-BuOOH or air as the oxidant is reported in this study. The method exhibits good functional group tolerance and provides a new class of cyclic building blocks. The strong solvent dependence of the transformation and the synthetic versatility of the N-sulfonyl imidate product class are highlighted.