Sustainable synthesis of thiosulfonates and disulfides by molybdenum-catalyzed selective oxidation of thiols

Abstract

Thiosulfonates and disulfides are important scaffolds in bioactive molecules and drugs, yet methods for the synthesis of these compounds that start from simple and commercially available feedstocks with sustainable routes are scarce. In this report, we present a green protocol for the synthesis of these valuable S–S motifs through selective oxidation of thiols using H₂O₂ or air as oxidant and anionic polyoxomolybdate (Mo₈O₂₆⁴⁻) as catalyst. Notable features of this method are scalability, operational simplicity, broad functional-group compatibility, and good chemoselectivity. Mechanistic studies, such as radical trapping experiments, kinetic experiments, cyclic voltammetry, ultraviolet-visible spectroscopy, infrared spectroscopy and Raman spectral monitoring of the reaction mixture support formation of a molybdenum(V)-hydroxo-species and a molybdenum(VI)-peroxo-species to drive the two different catalytic cycles, respectively.