Pentafluorohalobenzene (C₆F₅X) as Iodine or Bromine Transfer Reagents for Synthesis of Disubstituted Pyridines

We report pentafluorohalobenzene (C6F5I and C6F5Br) as an iodine or bromine transfer reagent for the generation of both electron-rich and electron-poor (hetero)aryl iodides and bromides with excellent chemo/regio selectivity in up to 95% yields. Continuous flow synthesis proved to be advantageous for this transformation. The iodine or bromine transfer occurs through treatment with in situ-generated (hetero)aryl Grignard reagents derived from aryl halides with C6F5I or C6F5Br. The resulting iodo- and chloro/bromo-pyridines were further transformed into bis-substituted pyridines through subsequent chemoselective coupling reactions.