To further probe the radical generation process, electron paramagnetic resonance (EPR) studies were then carried out with 5,5dimethyl-pyrroline N-oxide (DMPO) as a radical trap (Figure ). In a solution of 1a, 2a, and DMPO in the presence of Cu(CH3CN)4PF6/L10 in the dark without 3a, no EPR signal was observed (Figure Moreover, the cyclic voltammetry experiments showed that the oxidation potential of copper catalysts can be significantly influenced by coordinating with different Box-type ligands (Supporting Information, Figure ). Recently, the Gong group disclosed that chiral Cu(II)-Box catalyst can coordinate with imine substrates to facilitate their SET-reduction. Based on these literature reports and our mechanistic studies, we proposed that the Cu(I)/Box can work as Lewis acid to coordinate with oxime carbonate to facilitate its SET-reduction towards generation of iminyl radical and Cu(II) complex.