Iron-Catalyzed Cross-Coupling of Functionalized Benzylmanganese Halides with Alkenyl Iodides, Bromides, and Triflates

Various substituted benzylic manganese chlorides were prepared by insertion of magnesium turnings in the presence of MnCl2·2LiCl in THF at −5 °C within 2 h. These benzylic manganese reagents underwent smooth cross-couplings with various functionalized alkenyl iodides, bromides, and triflates or iodoacrylates in the presence of 10 mol % FeCl2 at 25 °C for 1–12 h. Mechanistic studies showed that benzylic manganese halides produced, in the presence of FeCl2, a very reactive iron ate complex.