Electrochemical ring-opening oxidation of aryl thianthrenium salts†

Transformations of aryl thianthrenium salts have emerged as versatile approaches to access fine chemicals. However, these methods have mainly focused on the synthesis of substituted arenes via a dethianthrenation process, which inevitably leads to thianthrene waste. In this work, an interesting electrochemical ring-opening oxidation of aryl thianthrenium salts is accomplished without the need for chemical oxidizing reagents. This electrochemical protocol not only provides a robust route for obtaining arylthio-substituted diarylsulfoxides, but also offers new prospects for further exploring the synthetic utility of aryl thianthrenium salts. More importantly, the resulting sulfoxide products could be applied to produce asymmetric bis-sulfides, bis-sulfoxides, and bis-sulfones with excellent yields. Mechanistic studies and DFT calculations suggest that the oxygen atom in the sulfoxide group comes from H₂O and the oxygen radical might be a key intermediate in the ring-opening process of aryl thianthrenium salts.