Rearrangement of 4-acetoxy-2H-1,4-benzoxazin-3(4H)-one.

4-Acetoxy-2H-1, 4-benzoxazin-3 (4H)-one (3) undergoes rearrangement or nucleophilic attack to give 2-, 5-, 6-, and 7-substituted derivatives of the benzoxazinone according to the reaction conditions. The formation of 5- and 7-substituted products was interpreted in terms of nucleophilic attack on the cation (14) formed by the heterolysis of the N-O bond of 3. For the formation of 6-substituted derivatives of the benzoxazinone, participation of the oxygen atom at position 1 of the benzoxazinone (that is, formation of an oxonium ion, 18) is important. A possible mechanism for the formation of 2-substituted products also involves an oxonium ion (19). These novel aspects of acetoxybenzoxazinone chemistry may contribute to an understanding of the mechanism of the actions of the prohibitins in cereal plants.