Cobalt(ii)-catalyzed benzylic oxidations with potassium persulfate in TFA/TFAA

A cobalt-catalyzed C(sp3)-H oxygenation reaction to furnish aldehyde was herein reported. This transformation demonstrated high chemo-selectivity, and tolerated various methylarenes bearing electron-withdrawing substituents. This reaction provided rapid access to diverse aldehydes form methylarenes. Notably, TFA/TFAA was used for the first time as a mixed solvent in cobalt-catalyzed oxygenation of benzylic methylenes.