Metal‐Free [4‐OH‐TEMPO] ⁺ [NO ₃ ] ⁻ ‐Catalyzed Aerobic Oxidation of Benzylic C(sp ³ )–H Bonds in Ethers

A cheap organocatalyst, [4‐OH‐TEMPO] + [NO 3 ] − , is presented for the aerobic oxidation of benzylic C(sp 3 )H bonds in ethers. The catalytic efficiency is attributed to the cooperative action of both the cation and anion moieties. The oxoammonium cation facilitates hydride abstraction from the C(sp 3 )H bond, generating a stabilized carbocation intermediate, which is subsequently attacked by water to form the CO bond. Meanwhile, the nitrate anion participates in a NO x /O 2 cycle, regenerating the oxoammonium cation from its reduced hydroxylamine form. Under mild reaction conditions, this salt catalyzes the oxidation of ethers to produce lactones or ketones in excellent yields, even on a 10 mmol scale. Control experiments confirm that the carbocation intermediate is essential to the reaction and that the oxygen atom in the product is derived from water.