Nickel-Catalyzed Difunctionalization of Alkynyl Bromides with Thiosulfonates and N-Arylthio Succinimides: A Convenient Synthesis of 1,2-Thiosulfonylethenes and 1,1-Dithioethenes

Abstract

An efficient Ni-catalyzed vicinal thiosulfonylation of 1-bromoalkynes with thiosulfonates in the presence of cesium carbonate has been described. An operationally simple and highly regioselective atom transfer radical addition (ATRA) of alkynyl bromides provided a wide range of (E)-1,2-thiosulfonylethenes (alpha-aryl-beta-thioarylvinyl sulfones) in moderate to high yields. The immense substrate scope of both alkynyl bromides and thiosulfonates were explored with a broad range of functional groups. Also, the indole derived 1,1-bromoalkenes were also successfully sightseen in 1,2-thiosulfonylation process. Moreover, the Ni-catalyzed geminal-dithiolation of alkynyl bromides with N-arylthio succinimides, thus providing 1,1-dithioalkenes in high yields. The present protocol is reliable at gram-scale, and a sequential one-pot bromination and thiosulfonylation of phenylacetylene have also been achieved in scale-up synthesis. A plausible mechanism is proposed to rationalize the experimental outcome and control experiments for the vicinal thiosulfonylation.