Electrochemical Sulfonylation in Deep Eutectic Solvents Enables the Sustainable Synthesis of 2-Quinoline Sulfones.

Abstract

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 nonrecyclable electrolytes, which compromise the environmental and economic viability of the approach. Taking the electrosynthesis of 2-arylsulfonylquinolines as representative case, the aforementioned issues by incorporating a deep eutectic solvent that functions simultaneously as the reaction medium and supporting electrolyte are addressed. The method delivers excellent yields, and products are isolated at gram scale via simple water washing and filtration. Interestingly, the eutectic solvent is recovered and reused for up to five cycles without significant loss in reaction yields. In a more general vein, this strategy not only eliminates volatile organic solvents throughout both the reaction and purification stages, but also integrates a recyclable solvent-electrolyte system, there for enabling a fully sustainable electrosynthetic process.