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C(sp3)-H Fluorination with a Copper(II)/(III) Redox Couple

preprint
submitted on 01.03.2020 and posted on 03.03.2020 by Jamey Bower, Andrew Cypcar, Brenda Henriquez, S. Chantal E. Stieber, Shiyu Zhang

Despite the growing interest in the synthesis of fluorinated organic compounds, few methods are able to incorporate fluoride ion directly into alkyl C-H bonds. Here, we report the C(sp3)-H fluorination reactivity of a formally copper(III) fluoride complex. The C-H fluorination intermediate, LCuF, along with its chloride and bromide analogs, LCuCl and LCuBr, were prepared directly from halide sources with a chemical oxidant and fully characterized. While all three copper(III) halide complexes capture carbon radicals efficiently to afford C(sp3)-halogen bonds, LCuF is two orders of magnitude more efficient at hydrogen atom abstraction (HAA) than LCuCl and LCuBr. Alongside reported kinetic data for other LCu(III) species, we established a positive correlation between ligand basicity and the rate of HAA. The capability of LCuF to perform both hydrogen atom abstraction and radical capture was leveraged to enable fluorination of allylic and benzylic C-H bonds and α-C-H bonds of ethers at room temperature.

Funding

CHE-1904560

CHE-1847926

DE-AC02-76SF00515

History

Email Address of Submitting Author

zhang.8941@osu.edu

Institution

The Ohio State University

Country

USA

ORCID For Submitting Author

0000-0002-2536-4324

Declaration of Conflict of Interest

None

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in Journal of the American Chemical Society

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