Nickel(II)-catalyzed intramolecular C(sp²)–H/C(sp³)–H and C(sp²)–H/C(sp²)–H oxidative couplings in indoles are achieved via chelation assistance. These reactions provide access to biologically relevant five- and six-membered substituted cyclopentaindolones, carbazolones, and indenoindolones in high yields and good chemoselectivity employing an air-stable and defined nickel catalyst, (bpy)Ni(OAc)₂. The oxidative cyclizations proceeded either through a six-membered or an unconventional seven-membered nickelacycle. An extensive mechanistic investigation by experiments and theoretical calculations revealed a facile indole’s C(2)–H nickelation and a rate-limiting reductive elimination process. This intramolecular oxidative cyclization operates via a probable Ni(II)/Ni(III) pathway involving single-electron oxidation of nickel without the participation of a carbon-based radical.

中文翻译：

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Ni(II)-催化的分子内 C-H/C-H 氧化偶联：功能化环吲哚酮和茚并吲哚酮的有效途径

吲哚中镍（II）催化的分子内 C(sp ² )–H/C(sp ³ )–H 和 C(sp ² )–H/C(sp ² )–H 氧化偶联是通过螯合辅助实现的。这些反应使用空气稳定和确定的镍催化剂 (bpy)Ni(OAc) ₂以高产率和良好的化学选择性获得生物学相关的五元和六元取代环戊烷酮、咔唑酮和茚并吲哚酮. 氧化环化通过六元或非常规的七元镍环进行。通过实验和理论计算进行的广泛机理研究揭示了吲哚的 C(2)-H 镍化和限速还原消除过程。这种分子内氧化环化通过可能的 Ni(II)/Ni(III) 途径进行，涉及镍的单电子氧化，而没有碳基自由基的参与。