Redirecting Nitroarene Electroreduction toward Nitrogen-Scaffold Synthesis

Nitroarene electroreduction typically terminates at anilines, limiting access to partially reduced N-O intermediates for nitrogen-scaffold synthesis. Here we redirect nitroarene electroreduction through a hydroxylamine-mediated pathway for nitrogen-scaffold synthesis. Mechanistic studies identify a phenylhydroxylamine-derived isoxazolium intermediate that undergoes N-O bond cleavage to form amides or indoles. Guided by the mechanistic insight, a molybdenum catalyst was developed to decouple nitroarene reduction from N-O-intermediate over-reduction, creating a productive window for intermediate accumulation and trapping. This strategy tolerates a wide range of nitroarenes and 1,3-dicarbonyl partners, providing modular access to diverse nitrogen-containing scaffolds. In a membrane-electrode assembly, the platform achieved 81% Faradaic efficiency at 100 mA cm-2 with an ultralow cell voltage of merely 0.83 V, operated stably for 144 h, and was scaled to 10 A in a 100 cm2 device with gram-per-hour output. This work establishes nitroarene electroreduction as a platform for controllable N-O-intermediate-based synthesis, expanding the use of nitroarenes beyond their conventional role as aniline precursors.