Ligand-Assisted Palladium(II)/(IV) Oxidation for sp³CH Fluorination

The direct functionalization of inert sp³CH bonds is limited to a few bond types. Although the activation of sp³CH bonds can be accomplished under mild conditions using palladium catalysts, the subsequent functionalization is not trivial due to the high energy required to convert palladium(II) to palladium(IV). We have systematically studied the palladium oxidation using computation-guided experiments for reactions involving strong chelation control. We find that a mild external ligand could significantly accelerate the oxidation of palladium(II) to palladium(IV) for strong bidentate directing groups. The acceleration is believed to be a result of ligand stabilization of both the palladium(II) and palladium(IV) intermediates. (Figure presented.) .