反应详情

Sodium hydroxide (4 g. 0.1 mol) was dissolved in water (4 ml) and methanol (50 ml). The 6-acetoxy-2-methyl (4H)3,1-benzoxazin-4-one (8.2 g, 0.04 mol), prepared above, in methanol (30 ml) was added, and the mixture refluxed for 3 hours. The solvent was removed by evaporation and the resulting sodium salt dissolved in water and acidified with hydrochloric acid. 5-Hydroxy N-acetyl anthranilic acid was collected as a beige solid and dried under vacuum. The dry solid (7.8 g, 0.04 mol) was then dissolved in dry THF (100 ml) and added to dicyclohexylcarbodiimide (8.24 g, 0.04 mol) in dry THF (50 ml). The mixture was stirred at room temperature for 18 hours and the insoluble urea removed by filtration. The filtrate was evaporated to dryness to give 6-hydroxy-2-methyl (4H)3,1-benzoxazin-4-one (2.7 g, 38%).

1. additionwas added
2. temperaturethe mixture refluxed for 3 hours
3. customThe solvent was removed by evaporation
4. dissolutionthe resulting sodium salt dissolved in water
5. custom5-Hydroxy N-acetyl anthranilic acid was collected as a beige solid
6. customdried under vacuum
7. customthe insoluble urea removed by filtration
8. customThe filtrate was evaporated to dryness