acetic acid containg a trace amount of coned sulfuric acid at 120 °C under nitrogen, 2-bromo-7-(2-hydroxyanilino)tropone (1a) gave 6-bromocyclohepta[b][1,4]benzoxazine (2a) as the main product and cyclohepta[b][1,4]benzoxazine, its 6,8-dibromo derivative and trace amounts of other mono-, di-, and tribromo compounds. This reaction became much more complex in the presence of oxygen. A similar bromine transfer
The benzoxazine moiety of 7-, 8-, and 9-isopropyl-as well as 6-bromocyclohepta[b][1,4]benzoxazines was easily exchanged with o-aminophenol and its methylderivatives in methanol or acetic acid. A possible pathway of this novel intermolecular heterocycle exchangereaction is discussed.