Synthesis of 2-Substituted 4<i>H</i>-3,1-Benzoxazin-4-ones by Thermally Induced Cyclization of<i>N</i>-(2-Benzyloxycarbonyl)phenyl Ketenimines; Oxygen-to-Carbon Migration of a Benzyl Group
N-(2-Benzyloxycarbonyl)phenyl ketenimines undergo a thermally induced cyclization to give -substituted 4H-3,1-benzox-azin-4-ones. These processes involve the formation of a new carbon-oxygen bond and the migration of the benzyl group from the oxygen atom of the benzyloxy unit at the ester function to the terminal carbon atom of the ketenimine fragment.