Expedient, metal-, extraction- and generally purification-free, temperature- and solvent-directed oxidation of diaryl sulfides using t-BuOCl

Abstract

An environmentally friendly, operationally simple and convenient, scalable, temperature- and solvent-directed oxidation of hydrophobic sulfides that yields sulfoxides and sulfones is presented. The conversion proceeds rapidly in a variety of green solvents, e.g., methanol, water, acetone, and acetic acid using tert-butyl hypochlorite (t-BuOCl), an easy-to-prepare and inexpensive oxidant with numerous applications in green chemistry and industry. Oxidation proceeds efficiently for challenging and purely soluble perfluoroalkyl, heterocyclic, or polyaryl systems with multiple strongly electron-withdrawing groups, e.g. nitro, acyl, and chloro, and selectively for electron-rich systems with benzylic and enolizable competing reaction sites or multiple sulfur atoms. Various industrially important products such as pesticides, anti-HIV agents, polymer monomers and additives can be generally isolated in pure form by simply removing the reaction solvent and benign volatiles. The mechanism was explored by NMR experiments and DFT calculations. Selective oxidation of polyphenylene sulfide allowed us to synthesize more durable polymer powders and to modify the surface of the film. The depth of the oxidized layer was tuned by duration of exposure to the oxidant. The developed clean, rapid, preparative, and scalable transformation of sulfides generally without required purification can likely be extended to other similar substrates and might be of interest for synthetic and sustainability-oriented chemical processes.