Cathode-Induced C-H Bond Heterolysis for Olefin Isomerization and Applications in Electrocarboxylation.

Olefin isomerization can not only convert terminal olefins into higher-value internal olefins but also serve as a bridge to connect with the functionalization reaction. However, traditional isomerization methods, such as base-mediated and transition-metal-mediated approaches, still face challenges like harsh conditions, low trans/cis (E/Z) ratios, unrecyclable metals, and industrial scalability. Herein, we report that the C-H bond could be activated at the cathode to form hydride ions (H-) and carbon radicals, which could initiate olefin isomerization via a radical mechanism without base or metal catalyst assistance. Through this new mechanism, various substrates, including chemicals with significant industrial demand, could be effectively converted into internal olefins with high yields, excellent E/Z ratios, and scalability, all while requiring only a catalytic amount of electrons. Furthermore, this electrochemical isomerization system was successfully applied to overcome the challenge of electrocarboxylation of nonconjugated olefins and carbon dioxide (CO2) by isomerizing nonconjugated olefins to conjugated olefins. This work makes a significant contribution to chemical science for C-H bond activation, and opens a new way for olefin isomerization with promising applications in electrochemical isomerization-functionalization reaction.