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Divalent organocopper complexes: masked radicals for effective electrochemically driven atom transfer radical addition Masnun Naher, Craig M. Williams and Paul V. Bernhardt * School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane 4072, Australia. Email: m.naher@uq.edu.au Copper-catalysed electrochemical atom transfer radical addition (eATRA) has emerged as a novel method for C−C bond formation, expanding the scope of electrocatalysis in organic synthesis. 1, 2 In this process, a CuI complex activates alkyl halides (RX) through coupled electron and atom transfer, generating organic radicals that are recaptured by CuI complexes to form unusual organocopper(II) intermediates, [CuIILR]+, stabilised by tetradentate N-donor ligands (Figure 1, middle). This [CuIILR]+ intermediate serves as the controlled-release source of radicals, facilitating efficient and selective atom transfer radical addition (ATRA) reactions and minimises unwanted radical homocoupling. 1−3 The methodology was applied to various organic halide initiators containing nitrile, keto, and ester functional groups, targeting C=C bonds in aromatic alkenes such as styrene and 2-vinyl naphthalene (Figure 1, right). X-ray crystallography, cyclic voltammetry, and UV/Vis spectroelectrochemical studies provided insights into the active organocopper(II) species, offering a detailed understanding of how functional groups influence reactivity. Optimised, mild reaction conditions were employed, presenting a novel approach beyond conventional copper-catalysed C−C bond formation. This presentation will address the potential of electrochemical methods in developing C−C bond formation in organic chemistry.
Figure 1: [CuIILX]+ complexes with (L1 = Me6tren) and L2 = bispidine ligand (left). The electrochemically triggered formation of the organocopper(II) complex [CuIILR]+ (middle) and Cu-catalysed electrochemical atom transfer radical addition (eATRA) (right).
Key words: eATRA, Copper-catalysed, C−C bond formation. References 1. Naher, M., Su, C., Harmer, J.R., Williams, C.M. and Bernhardt, P.V., Inorg. Chem . 2023 , 62, 15575-15583. 2. Gonzálvez, M. A., Su, C., Williams, C. M., Bernhardt, P. V. Chem. Sci . 2022 , 13,10506-11. 3. Naher, M., Su, C., Harmer, J. R., Williams, C. M., Bernhardt, P. V. Inorg. Chem . 2024 , 63, 6453-6464.
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