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

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.