Oxidant-Controlled Catalytic Transformations of Phenols with Unexpected Cleavage of Aromatic Rings

Oxidative transformations of phenols have attracted significant attention of chemists due to their importance in biological process and organic synthesis. In contrast to the relatively well-developed oxygenation and coupling reactions of phenols, the highly efficient and selective oxidative ring cleavage of phenols is under-represented. This work describes a novel CuCl-catalyzed tandem homocoupling/skeletal rearrangement of phenols that realizes the cleavage of the phenol ring by using air or Ag2CO3 as the oxidant. Interestingly, simply changing the oxidant to K2S2O8 results in the oxidative coupling/cyclization of phenols to give dibenzofurans. These results set an important precedent of oxidant-controlled catalytic transformations of phenols.