ScholarWorks@중앙대학교

초록

Modulating the redox potential of organic substrates is a powerful strategy for steering electrochemical reaction pathways, particularly for systems capable of undergoing both oxidation and reduction. Herein, we report the first electrochemical cyclization of areneazo-2-(2-nitro)propanes to benzo[c]cinnolines enabled by solvent-mediated redox pathway control. Careful selection of the reaction medium, especially mixed solvent systems containing hexafluoroisopropanol (HFIP) and alcohol additives, not only widens the redox potential gap between oxidation and reduction events but also stabilizes key intermediates through hydrogen-bonding interactions, thereby favoring oxidative intramolecular cyclization over competing denitrogenative reduction pathways. Cyclic voltammetry reveals a clear correlation between solvent-dependent redox windows and reaction outcomes, underscoring the decisive role of solvent effects in governing electrochemical selectivity. Under optimized constant current conditions using graphite electrodes, a broad range of areneazo-2-(2-nitro)propanes undergo efficient cyclization to afford benzo[c]cinnolines in good yields. Mechanistic studies support a pathway involving MeOH-stabilized diazonium intermediates and controlled redox fragmentation, demonstrating how strategic solvent engineering can unlock new electrochemical transformations of redox-active organic substrates.

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