反应详情

A solution of 10 ml of boron tribromide in 50 ml of methylene chloride are added dropwise within 30 minutes at -10° to a solution of 1.0 g of 2-(3,4-dimethoxy-5-nitrophenyl)-4H-1-benzopyran-4-one in 100 ml of methylene chloride under an argon atmosphere, whereupon the mixture is stirred at room temperature overnight. After cooling to -20°, 20 ml of ethanol are added dropwise thereto. The mixture is then evaporated in a water-jet vacuum. The yellow residue obtained is extracted with water/ethyl acetate. The organic phase is washed with water, dried over sodium sulfate and evaporated. After recrystallization from ethanol/ethyl acetate, there is obtained 2-(3,4-dihydroxy-5-nitrophenyl)-4H-1-benzopyran-4-one in the form of yellow crystals of m.p. >240° (dec.).

1. temperatureAfter cooling to -20°
2. customThe mixture is then evaporated in a water-jet vacuum
3. customThe yellow residue obtained
4. extractionis extracted with water/ethyl acetate
5. washThe organic phase is washed with water
6. dry with materialdried over sodium sulfate
7. customevaporated
8. customAfter recrystallization from ethanol/ethyl acetate