Selective Mono- and Bis-Sulfenylation and Mono-Selenylation of 1-Bromoalkynes with Thiols and Phenylselenol: Divergent Access to Alkynyl Sulfides/Selenides and Symmetrical or Unsymmetrical (Z)-1,2-Dithioalkenes.

A green, KOH-mediated, transition-metal-free strategy has been developed for the selective mono- and bisthiolation of 1-bromoalkyenes with thiols, as well as the monoselective selenylation with phenylselenol under mild conditions. This operationally simple and air-tolerant protocol provides rapid access to alkynyl sulfides and selenides in good to excellent yields within 1 h. By simply tuning the thiol/KOH stoichiometry and reaction time, the reaction selectively affords alkynyl sulfides or symmetrical and unsymmetrical (Z)-1,2-dithioalkenes with exclusive Z-selectivity. The methodology features a broad substrate scope (>70 examples) and excellent functional-group tolerance. Control experiments, including D2O-labeling studies, support an ionic addition-elimination pathway involving a vinyl anion intermediate. The present protocol offers an efficient, practical, and scalable approach for the synthesis of structurally diverse organosulfur and organoselenium compounds.