Synthesis of Azo-Substituted Benzoxazin-4-ones by Base-Mediated Addition of Diazenyl Anions to Isatoic Anhydrides

High Resolution Image Download MS PowerPoint Slide A two-step synthesis of 4 H -benzo[ d ][1,3]oxazin-4-ones bearing an azo unit at C2 from isatoic anhydrides and silylated diazenes is reported. The key step is the diazenylation of an isocyanate formed in situ by base-mediated ring opening of the isatoic anhydride. The addition of the elusive diazenyl anion proceeds without the loss of dinitrogen in the basic reaction medium. The benzoxazinone motif is subsequently established by cyclization with the Mukaiyama reagent.