The metal-catalyzed C–H borylation of alkanes and arenes has received significant attention in recent years based on the many synthetic applications of the carbon–boron bond in synthesis and the increased effectiveness of this methodology in selectively activating C–H bonds. To complement the original sterically-controlled C–H borylation reactions, there have been many recent innovations that result in ortho- or meta-directed functionalization using a variety of directing group approaches. One such approach is to replace the rigid, electron-rich bipyridine and phenanthroline ligands with flexible, hemi-labile ligands. Partial dissociation of these hemi-labile ligands is believed to be responsible for the ability to afford ortho-directed C–H borylation reactions. A comprehensive mechanistic study of directed C–H borylation reactions has not been reported to support these assertions and provide additional insights into how to improve the regioselectivity and catalytic efficiency. Herein we describe mechanistic studies into the iridium-catalyzed ortho borylation of benzylic amines mediated by flexible aminopyridine ligands. In this work, the results of reaction kinetics, a kinetic isotope effect study, and a Hammett correlation analysis will be used to propose a reasonable catalytic cycle.

Mechanistic studies of the iridium-catalyzed ortho C-H borylation of benzylic amines

254th National Meeting (2017)

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