8-acetyl-6-(benzyloxy)-2H-benzo[b][1,4]oxazin-3(4H)-one

861841-90-9

79-04-9

869478-09-1

The general procedure for the synthesis of 8-acetyl-6-(benzyloxy)-2H-benzo[b][1,4]oxazin-3(4H)-ones from 1-(3-amino-5-(benzyloxy)-2-hydroxyphenyl)ethanone and chloroacetyl chloride is as follows: 21.0 mL (258 mmol) of chloroacetyl chloride was slowly added dropwise under ice-bath cooling to a mixture containing 60.0 g (233 mmol) 1-(3-amino-5-benzyloxy-2-hydroxyphenyl)ethanone and 70.0 g (506 mmol) potassium carbonate. After dropwise addition, the reaction mixture was stirred at room temperature overnight, followed by heating to reflux temperature and continued stirring for 6 hours. Upon completion of the reaction, the reaction mixture was filtered while hot and the filtrate was concentrated to about 400 mL. ice water was added to the concentrate and a precipitate was precipitated. The precipitate was collected by filtration, dried and purified by chromatography using a short silica gel column (eluent ratio of dichloromethane:methanol = 99:1). The fractions containing the target product were combined, the solvent was evaporated and the residue was suspended in a mixed solvent of isopropanol/diisopropyl ether, diafiltered and washed with diisopropyl ether to give the pure product. Yield: 34.6 g (50% yield); MS data: [M + H]+ = 298.