Orbital Interactions in Copper-mediated Reactions

Two copper(ll)-mediated coupling reactions and one Fe(III)-catalyzed reaction are outlined in Scheme 12.22. An example of the stoichiometric use of CuCl in the oxidative coupling of phenol 98 and amine 99 is shown in Equation 12.22-1, Scheme 12.22 [81]. This reaction also demonstrates the potential of copper-mediated processes in the formation of unsymmetrical adducts (with the formation of only minor amounts of homodimers as side products). The authors supported their experimental findings with calculations of the frontier orbital interactions and showed that the HOMO and LUMO interaction with the SOMO of the initially formed radical is favored in differently substituted coupling partners. The success of the reaction also strongly depends on the additive and the yield dropped significantly when the reaction was carried out without the chelating primary amine. 

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