Unified Mechanistic Concept of the Copper-Catalyzed and Amide-Oxazoline-Directed C(sp2)-H Bond Functionalization

Li Ping Xu, Brandon E. Haines, Manjaly J. Ajitha, Jin Quan Yu, Djamaladdin G. Musaev*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Density functional theory calculations have been performed to provide the unified mechanism of Cu(II)-catalyzed and amide-oxazoline (Oxa)-directed C(sp2)-H functionalization reactions. The common steps of the studied seven reactions (such as C-H bond vinylation, phenylation, trifluoromethylation, amination, alkynylation, and hydroxylation) are complexation, N-H and C-H bond deprotonation, and Cu(II)/Cu(II) → Cu(I)/Cu(III) disproportionation, leading to the Cu(III) intermediate. The mechanism of the studied C-H functionalization reactions, initiated from the Cu(III) intermediate, depends on the nature of coupling partners. With vinyl- or phenyl-Bpin, which bear no acidic proton (called as a Type-I reaction), the coupling partners are thein situgenerated (by addition of anions) anionic borates, which coordinate to the Cu(III) intermediate and undergo concerted transmetalation and reductive elimination to form a new C-C bond. In contrast, with imidazole, aromatic amines, terminal alkyne, and water (called as a Type-II reaction), which bear an acidic proton, the real coupling partners are theirin situgenerated deprotonated derivatives, which coordinate to copper and lead to a final product with the C-Y bond (Y = C, N, and O) via the reductive elimination pathway. The C(sp2)-H bond trifluoromethylation with TMSCF3is identified as a special case, positioned between the Type-I and Type-II reaction types. The real coupling partner of this reaction is thein situgenerated (via the CF3--to-OH-ligand exchange) CF3-anion that binds to the Cu(III) intermediate and undergoes the C-CF3reductive elimination. Our calculations, consistent with the experimental KIE study, have established C-H bond activation as a rate-limiting step for all reactions.

Original languageEnglish (US)
Pages (from-to)12620-12631
Number of pages12
JournalACS Catalysis
Volume11
Issue number20
DOIs
StatePublished - Oct 15 2021

Keywords

  • CH functionalization
  • Cu-catalyst
  • DFT calculations
  • directing group assisted
  • reaction mechanism

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry

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