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. 2023 Dec 13;145(49):26810-26816.
doi: 10.1021/jacs.3c09260. Epub 2023 Dec 5.

C-N Bond Formation at Discrete CuIII-Aryl Complexes

Maxwell S Reese  1 , Mitchell G Bonanno  1 , Jamey K Bower  1 , Curtis E Moore  1 , Shiyu Zhang  1
Affiliations

C-N Bond Formation at Discrete CuIII-Aryl Complexes

Maxwell S Reese et al. J Am Chem Soc. .

Abstract

Copper(III) aryl species are widely proposed as intermediates in Cu-catalyzed C-C and C-heteroatom bond formation reactions. Despite their wide utility, mechanistic aspects of C-heteroatom formation at CuIII centers as well as factors that lead to byproducts, e.g., Ar-H, Ar-Ar, remain elusive due to the rarity of discrete CuIII-Ar complexes. Herein, we report the synthesis and reactivity of a series of CuII and CuIII aryl complexes that closely mimic the intermediates in Cu-catalyzed C-N coupling reactions. Copper(II) aryl complexes [TBA][LCuII-ArR] were synthesized via the treatment of CuII with a range of aryl donors, such as ZnAr2R, TMS-ArR, and ArR-Bpin. Oxidation of [TBA][LCuII-ArR] produces formal copper(III) aryl complexes LCuIII-ArR. Treatment of copper(III) aryl complexes with neutral nitrogen nucleophiles produces the C-N coupling product in up to 64% yield, along with commonly observed byproducts, such as Ar-H and Ar-Ar. Hammett analysis of the C-N bond formation performed with various N-nucleophiles shows a ρ value of -1.66, consistent with the electrophilic character of LCuIII-ArR. We propose mechanisms for common side reactions in Cu-catalyzed coupling reactions that lead to the formation of Ar-Ar and Ar-H.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1.
Figure 1.
Single crystal X-ray diffraction structure of (A) [TBA]-[LCuArF5], (B) LCuIII–ArF5, (C) LCuIII–Ph, and (D) LCuIII–ArCF3 complexes. Cocrystallized solvents and hydrogen atoms have been omitted for clarity.
Figure 2.
Figure 2.
Oxidation of [TBA][LCuII–ArF5] to LCuIII–ArF5 with oxidants relevant to the CEL reaction.
Figure 3.
Figure 3.
Cyclic voltammograms of LCuIII–Ar complexes.
Figure 4.
Figure 4.
Hammett plot of the reaction of LCuIII–ArF5 with para-substituted anilines.
Figure 5.
Figure 5.
Eyring plot of the reaction of LCuIII–ArF5 with 4-anisidine.
Scheme 1.
Scheme 1.
Catalytic Cycles of Cu-Catalyzed C–N Coupling Reactions
Scheme 2.
Scheme 2.
C-Nucleophile Bond Formation at CuIII–Ar
Scheme 3.
Scheme 3.
Synthetic of (A) [TBA][LCu–ArF5] and (B) LCu–ArF5
Scheme 4.
Scheme 4.
Possible Mechanisms of C–N Bond Formation at Cu(III) and Pd(II)
Scheme 5.
Scheme 5.
Investigation of Ar–H and Ar–Ar Formation
See this image and copyright information in PMC

References

    1. Ullmann F; Bielecki J Ueber Synthesen in Der Biphenylreihe. Ber. Dtsch. Chem. Ges 1901, 34, 2174–2185.
    1. Chan DMT; Monaco KL; Wang RP; Winters MP New N- and O-Arylations with Phenylboronic Acids and Cupric Acetate. Tetrahedron Lett. 1998, 39, 2933–2936.
    1. Lam PYS; Bonne D; Vincent G; Clark CG; Combs AP N-Arylation of a-Aminoesters with p-Tolylboronic Acid Promoted by Copper(II) Acetate. Tetrahedron Lett. 2003, 44, 1691–1694.
    1. Lam PYS; Clark CG; Saubern S; Adams J; Winters MP; Chan DMT; Combs A New Aryl/Heteroaryl C-N Bond Cross-Coupling Reactions via Arylboronic Acid/Cupric Acetate Arylation. Tetrahedron Lett. 1998, 39, 2941–2944.
    1. Evans DA; Katz JL; West TR Synthesis of Diaryl Ethers through the Copper-Promoted Arylation of Phenols with Arylboronic Acids. An Expedient Synthesis of Thyroxine. Tetrahedron Lett. 1998, 39, 2937–2940.