Arene Activation at Iridium Facilitates C–O Bond Cleavage of Aryl Ethers

An arene activation strategy for the selective disassembly of aryl ethers is reported. A variety of aryl ethers readily bind an electrophilic pentamethylcyclopentadienyl iridium center by η6-arene coordination, generating complexes that are activated toward hydrolysis and cleavage of the Ar–OR bond (R = Me, Et, Ph). Hydrolysis occurs rapidly at room temperature in aqueous pH 7 phosphate buffer (or upon modest heating under acidic conditions), releasing alcohol while forming cyclohexadienyl-one products. Under strongly acidic conditions, protonation of the dienyl-one followed by substitution with starting aryl ether completes a hydrolysis cycle. Mechanistic studies suggest that the key hydrolysis step proceeds via nucleophilic attack at the ipso position of the arene (SNAr mechanism). The observed mechanism is considered in the context of lignocellulosic biomass conversion.