Nitrosonium Ion Catalyzed Oxidative Bromination of Arenes

Abstract A nitrosonium catalyzed bromination of electron‐rich arenes has been developed, using bromide salts as bromine sources, oxygen gas as a terminal oxidant and Brønsted acids (sulfuric acid, TFA or HBr). This arene bromination process is free of transition metals, proceeding in acetic acid and under mild temperatures (25–50 °C) to give brominated arenes with good to excellent yields. Our mechanistic studies indicated that this oxidative bromination of arenes reaction is catalyzed by nitrosnium ion (NO + ), without the involvement of Br 2 or Br + . The kinetic isotope effect of this reaction was measured using pentadeuteriophenyl phenyl ether ( k H / k D =1.1).