反应详情

MS: 230 (M+) ##STR41## A mixture of 13.0 g of 4-cyano-2,2-dimethyl-6-nitro-2H-1-benzopyran, 400 ml of acetic acid, 200 ml of water, and 100 ml of concentrated sulfuric acid was heated at reflux for 1.5 hours. After adding 100 ml of concentrated sulfuric acid, the refluxing was further continued for an additional period of 1 hour. The reaction mixture was poured into ice-water. The thus precipitated crystal was washed with water, dried, and recrystallized from a mixed solvent of acetonitrile and water to obtain 11.9 g of 2,2-dimethyl-6-nitro-2H-1-benzopyran-4-carboxylic acid represented by formula shown below.

1. temperaturewas heated
2. temperatureat reflux for 1.5 hours
3. washThe thus precipitated crystal was washed with water
4. customdried
5. customrecrystallized from a mixed solvent of acetonitrile and water