Mechanistic insights into copper-catalyzed aerobic oxidative coupling of N–N bonds |
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Authors: | Michael C Ryan Yeon Jung Kim James B Gerken Fei Wang Michael M Aristov Joseph R Martinelli Shannon S Stahl |
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Institution: | Department of Chemistry, University of Wisconsin–Madison, 1101 University Avenue, Madison Wisconsin 53706 USA.; Small Molecule Design and Development, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis Indiana 46285 USA |
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Abstract: | Catalytic N–N coupling is a valuable transformation for chemical synthesis and energy conversion. Here, mechanistic studies are presented for two related copper-catalyzed oxidative aerobic N–N coupling reactions, one involving the synthesis of a pharmaceutically relevant triazole and the other relevant to the oxidative conversion of ammonia to hydrazine. Analysis of catalytic and stoichiometric N–N coupling reactions support an “oxidase”-type catalytic mechanism with two redox half-reactions: (1) aerobic oxidation of a CuI catalyst and (2) CuII-promoted N–N coupling. Both reactions feature turnover-limiting oxidation of CuI by O2, and this step is inhibited by the N–H substrate(s). The results highlight the unexpected facility of the N–N coupling step and establish a foundation for development of improved catalysts for these transformations.Mechanistic studies provide valuable insights into Cu-catalyzed N–N coupling reactions relevant to energy conversion and pharmaceutical synthesis. |
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