Metal‐ and Reagent‐Free Electrochemical Synthesis of Alkyl Arylsulfonates in a Multi‐Component Reaction

This work presents the first electrochemical preparation of alkyl arylsulfonates by direct anodic oxidation of electron‐rich arenes. The reaction mechanism features a multi‐component reaction consisting of electron‐rich arenes, an alcohol of choice and excess SO2 in an acetonitrile‐HFIP reaction mixture. In‐situ formed monoalkyl sulfites are considered as key intermediates with bifunctional purpose. Firstly, this species functions as nucleophile and secondly, excellent conductivity is provided. Several primary and secondary alcohols and electron‐rich arenes are implemented in this reaction to form the alkyl arylsulfonates in yields up to 73 % with exquisite selectivity. Boron‐doped diamond electrodes (BDD) are employed in divided cells, separated by a simple commercially available glass frit. Organic electrosynthesis enables the synthesis of alkyl arylsulfonates starting from arenes with exquisite selectivity at constant current conditions. No prefunctionalization of the arene is required. A stock solution in acetonitrile serves as SO2 source and the in situ formation of monoalkyl sulfites omits the necessity of supporting electrolytes.