4-Acetyl-5-hydroxy-2-methyl-3,4-dihydro-2H-benzo[1,4]oxazine-2-carboxylic acid methyl ester 在
potassium dihydrogenphosphate 、 potassium nitrososulfonate 作用下,
反应 2.0h,
以84%的产率得到4-Acetyl-2-methyl-5,8-dioxo-3,4,5,8-tetrahydro-2H-benzo[1,4]oxazine-2-carboxylic acid methyl ester