Electrochemical Sulfonylation in Deep Eutectic Solvents to Access 2-Quinoline Sulfones

Organic electrosynthesis is gaining momentum, driven by the inherent advantages of using electricity in place of stoichiometric chemical oxidants, such as the improved atom efficacy, the minimization of waste and the lower cost. However, electrosynthesis methods rely on volatile organic solvents such as acetonitrile to solubilize the reagents, combined with expensive and non-recyclable electrolytes which compromise the environmental and economic viability of the approach. Taking the electrosynthesis of 2-arylsulfinylquinolines as representative case, we addressed the aforementioned issues by incorporating a deep eutectic solvent that functions simultaneously as the reaction medium and supporting electrolyte. The method delivered excellent yields, and products were isolated at gram scale via simple water washing and filtration. Interestingly, the eutectic solvent was recovered and reused for up to five cycles without significant loss in reaction yields. In a more general vein, this strategy affords not only to eliminate volatile organic solvents throughout both the reaction and purification stages, but also to integrate a recyclable solvent-electrolyte system, therefore enabling a fully sustainable electrosynthetic process.