Polyethylene glycol radical-initiated oxidation of benzylic alcohols in compressed carbon dioxide

The PEG radical from oxidative degradation of polyethylene glycol was first used to initiate the oxidation of benzylic alcohols to carbonyl compounds without the need of a catalyst and/or additive in a viable synthetic, cost-effective and environmentally benign way, in which PEG/O-2/CO2 acts as initiator, oxidant and solvent. Compressed CO2 in this study not only provides a safe environment to conduct the oxidation employing molecular oxygen as an oxidant, but also could improve the reaction and adjust the selectivity of the target product by altering CO2 pressure. Moreover, this methodology could be used to oxidize a set of benzyl alcohols. The findings introduced here provide useful examples for developing free-radical chemistry from PEG thermal oxidative degradation.