Mild Cu-Catalyzed Oxidation of Benzylic Boronic Esters to Ketones

The oxidation of benzylic boronic esters directly to the ketone is reported. This mild Cu-catalyzed method uses an ambient atmosphere of air as the terminal oxidant and is notably chemoselective. Oxidation of the C–B bond occurs selectively, even in the presence of unprotected alcohols. Initial investigation suggests the reaction proceeds through an alkylboron to Cu transmetalation, peroxide formation, and rearrangement to give the carbonyl