反应详情

A mixture of 10 g of 6-chloro-3,4-dihydro-2-methyl-3-oxo-2H-1,4-benzoxazine-8-carboxylic acid, 150 ml of methanol and 5 ml of concentrated sulfuric acid is refluxed under heating with stirring for 40 hours, and then cooled. The precipitated crystals are collected by filtration, washed with methanol and dried to give 9.5 g of methyl 6-chloro-3,4-dihydro-2-methyl-3-oxo-2H-1,4-benzoxazine-8-carboxylate, melting at 186°-189° C.

1. temperatureis refluxed
2. temperatureunder heating
3. temperaturecooled
4. filtrationThe precipitated crystals are collected by filtration
5. washwashed with methanol
6. customdried