Nickel‐Catalyzed Sulfonylation of Aryl Bromides Enabled by Potassium Metabisulfite as a Uniquely Effective SO2 Surrogate

The development and mechanistic investigation of a nickel-catalyzed sulfonylation of aryl bromides is disclosed. The reaction proceeds in good yields for a variety of substrates and utilizes an inexpensive, stench-free, inorganic sulfur salt (K₂ S₂ O₅ ) as a uniquely effective SO₂ surrogate. The active oxidative addition complex was synthesized, isolated, and fully characterized by a combination of NMR spectroscopy and X-ray crystallography analysis. The use of the isolated oxidative addition complex in both stoichiometric and catalytic reactions revealed that SO₂ insertion occurs via dissolved SO₂ , likely released upon thermal decomposition of K₂ S₂ O₅ . Key to the success of the reaction is the role of K₂ S₂ O₅ as a reservoir of SO₂ that is slowly released, thus preventing catalyst poisoning.