Late-Stage Direct o-Alkenylation of Phenols by Pd^II -Catalyzed C-H Functionalization

o-Alkenylation of unprotected phenols has been developed by direct C-H functionalization catalyzed by Pd^II . This work features phenol group as a directing group and realizes highly site-selective C-H bond functionalization of phenols to achieve the corresponding products in moderate to excellent yields at 60 °C. The advantages of this reaction include unprecedented C-H functionalization using phenol as a directing group, high regioselectivity, good substrate scope, mild reaction conditions, and high efficiency. To the best of our knowledge, this is the first example of a regioselective C-H alkenylation of unprotected phenols utilizing phenolic hydroxyl group as a directing group. The alkenylation of unprotected tyrosine and intramolecular cyclization are also successfully carried out under this catalytic system in good yields. Furthermore, this novel method enables a late-stage modification of complex phenol-containing bioactive molecules toward a diversity-oriented drug discovery.