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 (S_NAr mechanism). The observed mechanism is considered in the context of lignocellulosic biomass conversion