Photoinduced Vitamin‑B<sub>12</sub>-Catalyzed <i>meta</i>-C–H Bromination/Chlorination of Phenol Derivatives\nAssisted by a U‑Shaped Nitrile Template

A photoinduced\nvitamin-B<sub>12</sub>-catalyzed <i>meta</i>-C–H\nbromination/chlorination of phenol derivatives was established\nusing a nitrile directing template and <i>N</i>-bromosuccinimide\n(NBS)/<i>N</i>-chlorosuccinimide (NCS) as halogenated reagents,\nand a series of <i>meta</i>-bromination/chlorination products\nwere obtained in yields of 51 to 80%. This strategy overcame the selectivity\nproblem of phenols, which have difficulty obtaining <i>meta</i>-products through conventional electrophilic reactions. Furthermore,\nnatural product resveratrol and an intermediate of the γ-secretase\ninhibitor were successfully synthesized, which demonstrates the practicability\nof this method.