­Field-induced concentration and low coordination-enhanced adsorption boost electroreductive deuteration of nitriles over copper nanotips

Abstract Electrochemical deuteration utilizing D2O is a promising room-temperature strategy for synthesizing deuterated molecules. At present, high Faradic efficiencies (FEs) at high reaction rates are extraordinarily significant but highly challenged. Here, high-curvature low-coordinated copper nanotips (LC-Cu NTs) are designed to enable electroreductive deuteration of α-deuterio aryl acetonitriles, in situ generated from fast α-H/D exchange of acetonitriles in D2O, to α,β-deuterio arylethyl primary amines with 90% FE and 0.11 mmol h-1 cm-2, greatly outperforming the reported data and other Cu counterparts. The increased electric fields of the nanotips concentrate nitriles and K+(D2O)n, and low-coordination sites promote nitriles and D2O adsorption, thus facilitating nitrile deuteration with an excellent reaction rate. The higher coupling energy barrier of active hydrogen atoms at low-coordination sites restricts the D2 evolution, accounting for the outstanding FE. The wide substrate scope, easy gram-scale synthesis, and facile preparation of d4-melatonin with enhanced antitumor and antioxidation effects highlight its great promise. Furthermore, the application of LC-Cu NTs in other deuteration reactions with improved reaction rates and FEs rationalizes the design concept.