Pyrone Isomerization Enabled Divergent Access to Multisubstituted Biaryl Phenol via Relay Claisen Rearrangement

Arene isomerization can simultaneously edit the arene backbone and its periphery, thereby bridging the independent chemistry of two distinct arenes. Herein, a facile pyrone isomerization approach for the divergent synthesis of five- and sixfold-substituted biaryl phenols is achieved by using a relay Claisen rearrangement as a crucial step. This catalyst-free isomerization reaction features high step, atom, and redox economy by transferring the innate oxidation state of pyrone into the biaryl phenols. Additionally, an intriguing self-activation phenomenon was observed, which enabled the selective dienone–phenol rearrangement of the aryl group.