Aerobic Oxidation of Alcohols Using 4-Hydroxy-TEMPO Adsorbed on Silica Gel

Aoyama et al. have developed a convenient method for adsorbing 4-hydroxy-TEMPO and NaCl onto silica gel, and reported the aerobic oxidation of alcohols using this SiO₂-supported reagent. According to their results, the oxidation of various alcohols proceeds under mild conditions by using this reagent and Fe(NO₃)₃•9H₂O as catalysts to afford the corresponding carbonyls in good to excellent yields. This reagent can be easily prepared by addition of silica gel to the aqueous solution of 4-hydroxy-TEMPO and NaCl, and separated from the reaction mixture by filtration and reused.