Efficient Catalytic, Oxidative Lactonization for the Synthesis of Benzodioxepinones Using Thiazolium-Derived Carbene Catalysts

An efficient, oxidative carbene-catalyzed lactonization reaction has been developed. Using thiazolium precatalysts, a variety of benzodioxepinone products are accessible in good to excellent yields under mild and operationally simple conditions The reaction does not require high dilution conditions and proceeds via mild and selective oxidation with azobenzene, which can easily be recovered and reused applying inexpensive FeCl3 as a formal terminal oxidant