Tellurium Oxides as Mild Oxidizing Agents

Diaryl Tellurium Oxides as Mild Oxidizing Agents 

Bis[4-methoxyphenyl] tellurium oxide was found to be a mild and highly selective oxidizing agent for the conversion of thiocarbonyl groups to carbonyl groups, thiols to disulfides, arylhydrazines to arenes, and 1,2- or 1,4-dihydroxyarenes to quinones. No reaction was observed with simple phenols, alcohols, enamines, amines (including pyrrole, indole, tryptophan, tyrosine, aniline, and dimethylaniline), oximes, dithiolanes, isonitriles, and 2,4-dinitrophenylhydrazones.  

Irgolic Organo Tellurium Compounds with 2 Te —C Bonds or 1 Te = C Bond 

In all of these reactions, the diaryl tellurium oxide is reduced to the diaryl tellurium. To make the conversion of thiocarbonyl to carbonyl groups catalytic with respect to the diaryl tellurium oxide, the diaryl tellurium must be converted back to the diaryl tellurium oxide. A catalytic cycle was developed with 1,2-dibromotetrachloroethane as the agent oxidizing the diaryl tellurium to the diaryl tellurium dibromide and 20% aqueous potassium carbonate as the base hydrolyzing the tellurium dibromide to the tellurium oxide  

Bis[4-dimethylaminophenyl] tellurium oxide was observed to react more rapidly than bis[4-methoxyphenyl] tellurium oxide. The water-soluble bis[4-carboxymethoxyphenyl] tellurium oxide was considerably less reactive  

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