Oxygen Vacancy Boosts Nitrogen-Centered Radical Coupling Initiated by Primary Amine Electrooxidation.

Synthesis of nitrogen-centered radicals (NCRs) for radical coupling reactions is a powerful and versatile tool in the arsenal of organic synthetic chemistry. However, there are few reports on the direct synthesis of NCRs based on aqueous electrocatalysis. Herein, we present a new electrochemical primary amine oxidation reaction (ePAOR) system with RR-CH-NH as the substrate for synthesizing NCRs and N-N coupling products. However, ePAOR on the model catalyst (NiO) suffers from low N-N coupling selectivity due to the weak adsorption energy of imine (RR-C═NH) intermediates. Guided by theoretical calculations, the oxygen vacancy gives NiO a strong adsorption capacity of RR-C═NH so that it boosts nitrogen-centered radical coupling initiated by the ePAOR on oxygen vacancy-rich NiO (V-NiO), and the effective utilization rate of NCRs was increased from 36 to 75%. This approach is compatible with a wide range of primary amines and can be applied to N-N cross-coupling systems as well.