Photochemical rearrangement of aromatic ethers

The irradiation of various types of aromatic ethers with ultraviolet light has been shown to yield o- and p-substituted phenols, resulting from C-O bond fission followed by recombination of the two fragments. Also formed in these photolyses was the parent phenol, produced presumably by abstraction of hydrogen from the solvent by the aryloxy fragment. The ethers investigated were aryloxyacetic acids,1 allyl aryl ethers,2 benzyl phenyl ether, and diphenyl ether. Mixture experiments have shown that for both the aryloxyacetic acids and allyl aryl ethers the rearrangement is intramolecular and most probably proceeds by formation of a radical-pair enclosed in a solvent cage.