Abstract
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).
Highlights
Organotellurium oxides have been recognized as useful oxidation reagents [1].In particular, diaryl telluroxides, tellurones, and aryltellurinic acid derivatives have been identified as versatile and effective oxidants for alcohols, phosphines, thiols, thiocarbonyl compounds, and so on [2,3,4,5,6,7,8,9,10,11]
We have developed organotelluride-catalyzed oxidation of phosphites to phosphates [12], silanes to silanols [13], and thiols to disulfides [14] while employing aerobic oxygen as a terminal oxidant under photosensitized conditions, where the in situ generation of tellurium oxide species by singlet oxygen oxidation is expected
The ionic liquid (IL)-supported diphenyl telluride was prepared in the following manner
Summary
Diaryl telluroxides, tellurones, and aryltellurinic acid derivatives have been identified as versatile and effective oxidants for alcohols, phosphines, thiols, thiocarbonyl compounds, and so on [2,3,4,5,6,7,8,9,10,11]. These oxidation reactions require stoichiometric amounts of organotellurium reagents. We envisioned to immobilize the organotelluride catalyst on an ionic liquid (IL) support
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