Copper-catalyzed synthesis of oxime ethers from iminoxy radical (CN–O) and maleimides via radical addition

•An efficient Cu(II)-catalyzed radical addition reaction of ketoximes with N-substituted maleimides.•Synthesis of O-(N-substituted-2,5-dicarbonyl pyrrolidine)-oxime ether products in moderate to good yields.•The evidence of oxime radical confirmed by EPR spectroscopy.•The radical addition reaction mechanism indicated by variable-temperature 1H NMR.