Aerobic oxidation of alcohols to carbonyl compounds mediated by poly(ethylene glycol)-supported TEMPO radicals

Two poly(ethylene glycol)-supported TEMPO (PEG-TEMPO) has been successfully applied as soluble, recyclable catalysts in the chemoselective oxidation of primary and benzylic alcohols with molecular oxygen in the presence of Co(NO3)2 and Mn(NO3)2 as co-catalysts (Minisci's conditions). Under those conditions, secondary alcohols are also oxidized to ketones, although usually in lower yields. The insertion of a spacer between the PEG moiety and TEMPO has beneficial effects on both the activity and ease of recovery of the supported catalyst.