Oxidative Cleavage of Aromatic C−O Linkages by Oxoammonium Salts

Oxidative cleavage of aromatic C(sp²)−O bond is important to the conversion of biomass and plastic wastes into value-added chemicals. Here we put forward the oxidative cleavage of para-C−O bonds in phenolic compounds in use of oxoammonium salts as oxidant and water as the oxygen source. The mechanism is that oxoammonium cation activates water to form hydroxy-oxoammonium adduct and thus realizes the ipso-substitution of 4-alkoxyphenol, which is proved by substituent effect, isotope labelling experiments, and kinetic analysis. Furthermore, this protocol is successfully applied into the depolymerization of both lignin model compounds with α-O-5 and 4-O-5 linkages and polyphenylene oxide (PPO).