Metal-Free sp(2)-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes

C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylbor...

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Veröffentlicht in:Journal of the American Chemical Society 2016-04, Vol.138 (14), p.4860-4868
Hauptverfasser: Chernichenko, Konstantin, Lindqvist, Markus, Kótai, Bianka, Nieger, Martin, Sorochkina, Kristina, Pápai, Imre, Repo, Timo
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Sprache:eng
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Zusammenfassung:C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp(2)-C-H bond and intramolecular protonation of the sp(2)-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes.
ISSN:1520-5126
DOI:10.1021/jacs.6b00819