Organocatalytic Aerobic Oxidation of Benzylic sp3 C-H Bonds of Ethers and Alkylarenes Promoted by a Recyclable TEMPO Catalyst

An entirely metal-free catalyst system consisting of an easily prepared recyclable new TEMPO derived sulfonic salt catalyst, and mineral acids (NaNO2 and HCl) has been developed for selective aerobic oxidation of structurally diverse benzylic sp(3) C-H bonds of ethers and alkylarenes. The mild reaction conditions allow for the generation of synthetically and biologically valued isochromanones and xanthones from readily accessible alkyl aromatic precursors in good yields.