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

ABSTRACT: 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.

SUBMITTER: Pabst TP 

PROVIDER: S-EPMC9010962 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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Development of Cobalt Catalysts for the <i>meta</i>-Selective C(sp<sup>2</sup>)-H Borylation of Fluorinated Arenes.

Pabst Tyler P TP   Chirik Paul J PJ  

Journal of the American Chemical Society 20220402 14

Cobalt precatalysts for the <i>meta</i>-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 (<b>5,5″-Me<sub>2</sub><sup><i>Ar</i></sup>Tpy</b> = 4'-(4-<i>N,N'</i>-dimethylaminophenyl)-5,5″-dimethyl-2,2':6',2″-terpyridine). Under the optimized conditions, borylation with this precatalyst afforded up to 16 turnovers and near-exc  ...[more]

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