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Cu-Catalyzed Aerobic Oxidative N–N Coupling of Carbazoles and Diarylamines Including Selective Cross-Coupling
- Ryan, Michael C., Martinelli, Joseph R., Stahl, Shannon S.
- Journal of the American Chemical Society 2018 v.140 no.29 pp. 9074-9077
- carbazoles, catalysts, chemical bonding, cross-coupling reactions, dimerization, dimethyl sulfide, oxygen, thermodynamics
- A Cu-catalyzed method has been identified for aerobic oxidative dimerization of carbazoles and diarylamines to the corresponding N–N coupled bicarbazoles and tetraarylhydrazines. The reactions proceed under mild conditions (1 atm O₂, 60–80 °C) with a catalyst composed of CuBr·dimethylsulfide and N,N-dimethylaminopyridine. Reactions between carbazole and diarylamines show unusually selective cross-coupling, even with a 1:1 ratio of the two substrates. This behavior was found to arise from reversible formation of the tetraarylhydrazine. Formation of this species is kinetically favored, but cleavage of the N–N bond under the reaction conditions leads to selective formation of the thermodynamically favored cross-coupling product.