Polychlorinated Amides and Lactones via Electrochemically Mediated Copper-Catalyzed Atom Transfer Radical Addition

Electrochemically mediated atom transfer radical addition (eATRA) catalyzed by copper(II) has recently emerged as a powerful and sustainable strategy for carbon–carbon (C–C) bond formation in organic synthesis. Utilizing robust organocopper(II) complexes, α-haloamides were explored herein, which revealed their efficient catalysis in eATRA with a range of functionalized alkenes that afford unique polychlorinated amides. Interestingly, the initial eATRA addition products undergo subsequent intramolecular cyclization to afford five-membered lactones, as controlled by the electron-withdrawing or electron-donating substitution pattern of the alkene. A key feature of this transformation is the electrochemical generation of an unusual and highly reactive O-bound copper(II) species, [CuII(Me6tren)(OR)]+, in the presence of polyhalogenated primary amides. This O-bound amidate Cu complex gradually releases the amidyl radical (and [CuI(Me6tren)]+) by CuII–O bond homolysis to promote efficient eATRA. Mechanistic insights supported by cyclic voltammetry and ultraviolet–visible (UV–vis) spectroelectrochemical studies further clarify the role of copper intermediates in this process. This work demonstrates the versatility and efficiency of copper-catalyzed eATRA under mild electrochemical conditions and from readily available starting materials.