Hydroxylamine as a Source for Nitric Oxide in Metal-Free 2,2,6,6-Tetramethylpiperidine N-Oxyl Radical (TEMPO) Catalyzed Aerobic Oxidation of Alcohols

The communication reports on the metal-free 2,2,6,6-tetramethylpiperidine N-oxyl radical (TEMPO) catalyzed aerobic oxidation of various alcohols to aldehydes and ketones. A novel catalyst system that uses 1-4 mol% of TEMPO in combination with 4-6 mol% of aqueous hydroxylamine is introduced. No other additives are necessary and corrosive by-products are not formed during oxidation. Nitric oxide which is important for the catalytic cycle is generated in situ by reaction of the hydroxylamine with TEMPO. A catalytic cycle for the overall oxidation process is suggested.