Palladium-Catalyzed Hydrolytic Cleavage of Aromatic C-O Bonds.

Metallic palladium surfaces are highly selective in promoting the reductive hydrolysis of aromatic ethers in aqueous phase at relatively mild temperatures and pressures of H . At quantitative conversions, the selectivity to hydrolysis products of PhOR ethers was observed to range from 50 % (R=Ph) to greater than 90 % (R=n-C H , cyclohexyl, and PhCH CH ). By analysis of the evolution of products with and without incorporation of H O, the pathway was concluded to be initiated by palladium metal catalyzed partial hydrogenation of the phenyl group to an enol ether. Water then rapidly adds to the enol ether to form a hemiacetal, which then undergoes elimination to cyclohexanone and phenol/alkanol products. A remarkable feature of the reaction is that the stronger Ph-O bond is cleaved rather than the weaker aliphatic O-R bond.