Solvent-Driven Mono- and Bis-sulfenylation of ( E )-β-Iodovinyl Sulfones with Thiols for Flexible Synthesis of 1,2-Thiosulfonylalkenes and 1,2-Dithioalkenes.

The nature of solvent is a key factor for stereoselective mono- and bis-thiolation of ( E )-β-iodovinyl sulfones with thiols under basic conditions. A novel and unprecedented vicinal bisthiolation of ( E )-β-iodovinyl sulfones with thiols under the influence of K 2 CO 3 /DMSO at room temperature for quick assembly of ( E )-1,2-dithio-1-alkenes is presented. Solvent-induced stereoselective monosulfenylation of ( E )-β-iodovinyl sulfones with thiols has also been established for the synthesis of both ( E )- and ( Z )-1,2-thiosulfonylethenes in MeCN and MeOH, respectively. Moreover, K 2 CO 3 -mediated desulfonylative-sulfenylation of ( Z )-1,2-thiosulfonylethenes with thiols in DMSO furnished unsymmetrical ( Z )-1,2-dithio-1-alkenes for the first time. The solvent-dependent versatile reactivity of ( E )-β-iodovinyl sulfones has been successfully explored to provide a set of ( E )-/( Z )-1,2-dithio-1-alkenes and ( E )-/( Z )-1,2-thiosulfonyl-1-alkenes in good to high yields with excellent stereoselectivities. Notably, this operationally simple process utilizes a broad substrate scope with good functional group tolerance and compatibility. The efficacy of the process has been proven for gram-scale reactions, and plausible mechanistic models are outlined on the basis of experimental results and control experiments.