The main objective of this study was to design a recyclable TEMPO (2,2,6,6-tetramethylpiperidinyl-N-oxyl) derivative that could be used as a catalyst in an ionic liquid solvent for the aerobic oxidation of alcohols by using NaNO2 and HCl as co-catalysts. To this end, a TEMPO derivative bearing a quaternary ammonium group, [4-Bu2MeN-TEMPO][PF6] (1), was prepared. It was subsequently shown that this ionic TEMPO derivative is an efficient catalyst for the aerobic oxidation of a variety of primary and secondary alcohols. It exhibits a synergistic effect with ionic liquid solvents and readily outperforms analogous oxidations in methylene chloride. Moreover, the ionic TEMPO could be recycled five times with no loss of activity.
- ionic liquids