A Catalyst-Free Approach to Cyclic Sulfides via Tandem Nucleophilic Substitution and Intramolecular Thiosulfonylation

We report an efficient catalyst-free tandem reaction involving nucleophilic substitution and intramolecular thiosulfonylation between bromoalkane-tethered ynones and potassium thiosulfonate salts, yielding cyclic sulfides in moderate to good yields. In contrast to conventional thiosulfonylation methods, this tandem approach eliminates the need for laborious prepreparation of thiosulfonates by employing readily available potassium thiosulfonate salts to generate thiosulfonate precursors in situ. Notably, this mild reaction system has been successfully employed to construct various medium-sized and macrocyclic thioethers, including eight-, nine-, 10-, 13-, 15-, and even 26-membered rings.