Copper(II) alkynyl species are proposed as key intermediates in numerous Cu-catalyzed C-C coupling reactions. Supported by a β-diketiminate ligand, the three coordinate copper(II) alkynyl [CuII]-C≡CAr (Ar = 2,6-Cl2C6H3) forms upon reaction of the alkyne H-C≡CAr with the copper(II) tert-butoxide complex [CuII]-OtBu. In solution, this [CuII]-C≡CAr species cleanly transforms to the Glaser coupling product ArC≡C-C≡CAr and [CuI](solvent). Addition of nucleophiles R'C≡C-Li (R' = aryl, silyl) and Ph-Li to [CuII]-C≡CAr affords the corresponding Csp-Csp and Csp-Csp2 coupled products RC≡C-C≡CAr and Ph-C≡CAr with concomitant generation of [CuI](solvent) and {[CuI]-C≡CAr}-. Supported by DFT calculations, redox disproportionation forms [CuIII](C≡CAr)(R) species that reductively eliminate R-C≡CAr products. [CuII]-C≡CAr also captures the trityl radical Ph3C• to give Ph3C-C≡CAr. Radical capture represents the key Csp-Csp3 bond forming step in the copper catalyzed C-H functionalization of benzylic substrates R-H with alkynes H-C≡CR' (R' = (hetero)aryl, silyl) that provide Csp-Csp3 coupled products R-C≡CR via radical relay with tBuOOtBu as oxidant.

中文翻译：

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C-C 键形成中的三配位铜 (II) 炔基配合物：格拉泽偶联的百年纪念

铜 (II) 炔基物质被提议作为众多 Cu 催化的 CC 偶联反应的关键中间体。在 β-二酮亚胺配体的支持下，炔烃 HC≡CAr 与叔丁醇铜 (II) 反应形成三配位铜 (II) 炔基 [CuII]-C≡CAr (Ar = 2,6-Cl2C6H3)络合物[CuII]-OtBu。在溶液中，这种 [CuII]-C≡CAr 物种干净地转化为 Glaser 偶联产物 ArC≡CC≡CAr 和 [CuI]（溶剂）。将亲核试剂 R'C≡C-Li（R' = 芳基，甲硅烷基）和 Ph-Li 添加到 [CuII]-C≡CAr 中，得到相应的 Csp-Csp 和 Csp-Csp2 偶联产物 RC≡CC≡CAr 和 Ph- C≡CAr 伴随生成 [CuI]（溶剂）和 {[CuI]-C≡CAr}-。在 DFT 计算的支持下，氧化还原歧化形成 [CuIII](C≡CAr)(R) 物种，可还原消除 RC≡CAr 产物。[CuII]-C≡CAr 还捕获了三苯甲基自由基 Ph3C•，得到 Ph3C-C≡CAr。自由基捕获代表了铜催化的苄基底物 RH 与炔烃 HC≡CR'（R' =（杂）芳基，甲硅烷基）的 CH 官能化中的关键 Csp-Csp3 键形成步骤，通过自由基提供 Csp-Csp3 偶联产物 RC≡CR以 tBuOOtBu 作为氧化剂继电。