TY - JOUR
T1 - Development of Cobalt Catalysts for the meta-Selective C(sp2)-H Borylation of Fluorinated Arenes
AU - Pabst, Tyler P.
AU - Chirik, Paul J.
N1 - Funding Information:
Financial support was provided by the NIH (R01 GM121441). T.P.P. thanks Amgen for financial support and Princeton University for an Arthur A. Patchett ’51 Graduate Fellowship in Chemistry. We also thank AllyChem for a generous gift of BPin. 2 2
Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/4/13
Y1 - 2022/4/13
N2 - 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.
AB - 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.
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U2 - 10.1021/jacs.2c01162
DO - 10.1021/jacs.2c01162
M3 - Article
C2 - 35369695
AN - SCOPUS:85128173213
VL - 144
SP - 6465
EP - 6474
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 14
ER -