反应详情

20.1 g of diethyl (3,4-dimethoxy-5-nitrobenzoyl)-malonate are dissolved in 200 ml of methylene chloride, whereupon the solution is cooled to -20° and at this temperature there is added dropwise while stirring within 15 minutes a solution of 68.1 g of boron tribromide in 120 ml of methylene chloride. The mixture is subsequently stirred at room temperature overnight. After cooling to -20°, the mixture, is treated with 300 ml of ethanol and stirred at room temperature for 30 minutes. The solvent is distilled in a water-jet vacuum at 40°. The residue is treated with 300 ml of ice-water and methylene chloride. The organic phase is washed with water, dried over sodium sulfate and evaporated. The crude product obtained is chromatographed on a 10-fold amount of silica gel with toluene. After crystallization from methylene chloride/hexane there is obtained ethyl (3,4-dihydroxy-5-nitrobenzoyl)acetate in the form of yellow crystals of m.p. 136°-137°.

1. temperatureis cooled to -20° and at this temperature there
2. additionis added dropwise
3. temperatureAfter cooling to -20°
4. stirringstirred at room temperature for 30 minutes
5. distillationThe solvent is distilled in a water-jet vacuum at 40°
6. additionThe residue is treated with 300 ml of ice-water and methylene chloride
7. washThe organic phase is washed with water
8. dry with materialdried over sodium sulfate
9. customevaporated
10. customThe crude product obtained
11. customis chromatographed on a 10-fold amount of silica gel with toluene
12. customAfter crystallization from methylene chloride/hexane there