Ampere-Level Electrosynthesis of ¹⁵N-Labeled Oximes by Alloy Synergy Activation and Hydroxylamine Overhydrogenation...

¹⁵N-labeled molecules are essential for industrial drug development and medical imageology. However, the synthesis of ¹⁵N-labeled molecules suffers from the complex procedure of de novo synthesis and harsh conditions. Here, we propose an electrochemical strategy to synthesize ¹⁵N-labeled oximes (¹⁵N-oximes) from ¹⁵N-labeled nitrites (¹⁵NO₂ ^-) and aldehydes/ketones. Matching the adsorption and activation of H₂O and ¹⁵NO₂ ^- and inhibiting ¹⁵NH₂OH overhydrogenation are the keys to realizing efficient ampere-level electrosynthesis of ¹⁵N-labeled oximes. A bismuth-molybdenum (BiMo) alloy catalyst is subsequently designed, in which Bi acts as the ¹⁵NO₂ ^- activation site, whereas Mo serves as the H₂O activation site. The precisely controlled atomic ratio of Mo and Bi ensures that there is sufficient but not excessive active hydrogen provided for ¹⁵NO₂ ^- hydrogenation and therefore accelerates the reaction rate. Moreover, Mo incorporation increases the energy barrier of ¹⁵NH₂OH overhydrogenation and thus improves the Faradaic efficiency (FE) of ¹⁵N-oxime. This strategy enables scale-up electrosynthesis with a 76% FE and 88% yield at a current of 3.0 A to obtain 3.5 g of ¹⁵N-cyclohexanone oxime within 1.5 h. The application potential is highlighted by the methodological universality of diverse ¹⁵N-oximes, the extended synthesis of ¹⁵N-labeled drug molecules and their application in 2D magnetic resonance imaging visualization.