Development of Cobalt Catalysts for the meta-Selective C(sp2)-H Borylation of Fluorinated Arenes

Tyler P. Pabst, Paul J. Chirik

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Cobalt precatalysts for the meta-selective borylation of fluorinated arenes are described. Initial screening and stoichiometric reactivity studies culminated in the preparation of a cobalt alkyl precatalyst supported by the sterically protected terpyridine (5,5″-Me2ArTpy = 4′-(4-N,N′-dimethylaminophenyl)-5,5″-dimethyl-2,2′:6′,2″-Terpyridine). Under the optimized conditions, borylation with this precatalyst afforded up to 16 turnovers and near-exclusive meta regioselectivity with a range of substituted fluoroarenes in cyclopentyl methyl ether solvent at room temperature. Deuterium kinetic isotope effects of 2.9(2) at 23 °C support a turnover-limiting and selectivity-determining C(sp2)-H activation step, and stoichiometric C-H activation experiments provided insights into the identity of the C-H activating intermediate in catalysis. Analysis of the relevant Co-C and C-H bond thermodynamics support that the thermodynamics of C-H activation favor ortho-To-fluorine selectivity, providing additional, indirect support for kinetic control of C-H activation as the origin of meta selectivity.

Original languageEnglish (US)
Pages (from-to)6465-6474
Number of pages10
JournalJournal of the American Chemical Society
Issue number14
StatePublished - Apr 13 2022

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Biochemistry
  • Catalysis
  • Colloid and Surface Chemistry


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