Ni-catalyzed reductive cross-couplings of diaryl disulfides with aryl bromides for biaryl synthesis through C-S bond cleavage

In previous reports, the cross-couplings of diaryl disulfides with aryl halides in the presence of transition metal catalysts (e.g., Ni and Cu) and metal mediators (e.g., Mg and Zn) usually led to the corresponding aryl sulfides via old S-S bond cleavage and new C-S bond formation. In the present study, we found that the reductive cross-couplings of diaryl disulfides with aryl bromides proceeded via unusual C-S bond cleavage in the presence of a nickel catalyst, magnesium, and lithium chloride in THF at room temperature, leading to a variety of biaryls in modest to good yields. In addition, the reaction could be scaled up with ease. Mechanistic studies showed that the reaction possibly proceeds via the in situ production of an arylmagnesium compound as a reaction intermediate via LiCl-facilitated Mg insertion into aryl bromide. Most importantly, the combinatory use of the Ni(ii) catalyst and Mg mediator is key to the unusual cleavage of the C-S bond in diaryl disulfide to form the corresponding arylnickel(ii) species, which serves as another important intermediate in the present desulfurative cross-coupling reaction.