Electrochemical\nSulfonylation of Indoles with Inorganic\nSulfites and Alcohols: Direct Synthesis of Indole Sulfonic Esters

A direct electrochemical sulfonylation between indoles,\ninorganic\nsulfites, and alcohols was developed, in which various indoyl sulfonate\nesters were prepared efficiently. In this transformation, the easy-handle\nand cost-effective inorganic sulfite was disclosed to engage in a\nCsp<sup>2</sup>–H sulfonylation as the SO<sub>2</sub> source\nin an undivided electrolysis cell under mild conditions. In addition,\nthe unexpected paired electrosynthesis has been achieved, owing to\nthe dual role of inorganic sulfites, and led to a sulfonylation/reduction\nsequence to rapidly deliver hydroxyl substituted indole sulfonate\nesters.