Thioamidation via Sulfur-Promoted Coupling of N-Methyliminodiacetyl Acylborons and Amines

Thioamides were efficiently synthesized via a one-pot, chemoselective coupling of MIDA acylboronates, amines, and inorganic sulfur sources. The key step in this transformation involved the condensation of MIDA acylboronates with amines to generate an imine intermediate, which subsequently underwent nucleophilic addition with sulfur species. The nucleophilicity of linear polysulfides promoted S-S bond cleavage, followed by a concerted elimination to furnish the thioamides. A variety of sensitive functional groups, including unprotected hydroxyl, carboxyl, and alkynyl substitution moieties, are well tolerated under the reaction conditions. The formation of dipeptides and the late-stage incorporation of thioamide motifs further highlight the utility of this method.