Recent advances in the dichalcogenation reactions of unsaturated compounds via double functionalization

The past decade has witnessed significant advancements in the highly selective dichalcogenation (chalcogen = S, Se, Te) reactions of unsaturated substrates for the synthesis of dichalcogen compounds. The present review summarizes the recent advances in the disulfenylation, diselenation, mixed dichalcogenation, thiosulfonylation, selenosulfonylation, disulfonylation and sulfinylsulfonylation reactions of unsaturated compounds via double functionalization, with special emphasis on elucidating detailed mechanisms. Moreover, this review also includes the ring-closing dichalcogenation and thio(seleno)sulfonylation of S/Se-bearing unsaturated compounds for the synthesis of a variety of chalcogenated S- or Se-heterocycles. The scopes, limitations and existing problems of some reactions are also dicussed. The review aims to give researchers a good understanding of the dichalcogenation reactions and inspire future innovations in this rapidly expanding field.