Oxidation of Thiol Using Ionic Liquid-Supported Organotelluride as a Recyclable Catalyst

Organotellurium compounds are known to be useful oxidation reagents. For developing a recoverable and reusable reagent, this paper describes the use of an ionic liquid (IL) support for the organotellurium reagent and its application as a recyclable catalyst for thiol oxidation. We have successfully prepared a novel diphenyl telluride derivative 5 bearing an imidazolium hexafluorophosphate group in its structure. It is found that the IL-supported diphenyl telluride 5 efficiently catalyzed the aerobic oxidation of various thiols in [bmim]PF6 solution under photosensitized conditions to provide the corresponding disulfides in excellent yields. The product can be isolated by simple ether extraction. The IL-supported catalyst 5 remaining in the ionic liquid phase can be reused for five successive runs while retaining high catalytic activity (97% yield even in the fifth run).