Organic electro-synthesis has emerged as a transformative platform in modern synthetic chemistry, witnessing remarkable progress through its strategic replacement of stoichiometric chemical redox reagents with traceless electron. This paradigm shift not only enhances atom economy but also reduces chemical waste generation, aligning with green chemistry 12 principles. During the past years, considerable progress has been made in this area. However, the majority of these reactions require the use of stoichiometric supporting electrolytes to ensure adequate ionic conductivity, thus increasing the environmental and economic cost. As a result, the development of intrinsic supporting electrolyte-free electrochemical systems represents an essential frontier in sustainable synthesis, promising simplified reactor configurations and enhanced process sustainability while maintaining the inherent advantages of electro-synthetic activation. Quinoxalin-2(1H)-ones, especially 3-functionalized quinoxalin-2(1H)-ones, are important scaffolds featured in diverse natural products and pharmaceuticals, and possess a broad range of biological and pharmacological activities. The direct C3-H functionalization of quinoxalin-2(1H)-ones has been considered as an atom- and step-economic strategy for the construction of various 3-functionalized quinoxalin-2(1H)-ones. Notably, about 30% of top-selling 200 pharmaceuticals (2023) contain a benzyl group. Among various 3-functionalized quinoxalin-2(1H)-one derivatives, 3-benzylquinoxalin-2(1H)-ones as a valuable pharmacophore are found in numerous biologically active molecules. Consequently, the development of more green and efficient methods for synthesizing 3-benzylquinoxalin-2(1H)-ones is highly desirable in organic and pharmaceutical chemistry. Benzyl chlorides are low cost and abundant feedstock materials, which have been widely used as the benzylation reagents in organic synthesis. In the present work, we report the development of supporting electrolyte-free electrochemical benzylation of quinoxalin-2(1H)-ones with benzylic chlorides. With graphite plate as the anode, platinum plate as the cathode, dimethylsulfoxide as the solvent, a series of 3-benzylquinoxalin-2(1H)-ones were efficiently constructed via dechlorinative coupling reaction. The supporting electrolyte-, catalyst-free and mild conditions, readily available reactants, wide substrate scope and large-scale synthesis make the present strategy highly attractive in organic and pharmaceutical chemistry.

Key words: organic electrosynthesis, benzyl chlorides, quinoxalin-2(1H)-ones, benzylation, electrolyte-free