Synthesis of α‑<i>C</i>‑Stereochemically Pure Secondary Sulfonamides

A convenient “green” stereoretentive approach to <i>sp</i>^<i>3</i>-enriched secondary sulfonamides bearing an asymmetric center at the α position to the sulfur atom is described. The method relies on the electrophilic amination of the corresponding stereochemically pure sulfinates with <i>N</i>-alkylhydroxylamine sulfonic acids (in turn easily prepared from <i>N</i>-alkylhydroxylamine and HSO₃Cl). It is shown that the efficiency of the approach is governed mainly by steric factors; its tolerance to several functional groups (e.g., ether, phthalimide, or <i>N</i>-Boc carbamate) is also demonstrated.