Efficient Aryl Migration from an Aryl Ether to a Carboxylic Acid Group To Form an Ester by Visible‐Light Photoredox Catalysis

We have developed a highly efficient aryl migration from an aryl ether to a carboxylic acid group through retro‐Smiles rearrangement by visible‐light photoredox catalysis at ambient temperature. Transition metals and a stoichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C−O bond cleavage, we developed a novel approach to the C−O cleavage of a biaryl ether to form two phenolic compounds, as demonstrated by a one‐pot, two‐step gram‐scale reaction under mild conditions. The aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds, such as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by a reductive quenching pathway. A great migration: In a retro‐Smiles rearrangement under visible‐light photoredox catalysis at ambient temperature, one aryl group of a diaryl ether migrated to the carboxy group to form an ester (see scheme). The transformation requires no transition metals and no stoichiometric oxidant or base and could be followed by saponification in a one‐pot, two‐step process enabling overall C−O cleavage of the aryl ether.