反应详情

2'-Hydroxypropiophenone (15.02 g) and diethyl oxalate (17.54 g) were added to a solution of sodium ethoxide in ethanol (prepared from 6.90 g of sodium and 200 ml of ethanol), and the mixture was heated for 2.5 hours while refluxing. The mixture was cooled, poured over 2N HCl (320 ml) and extracted with ethyl acetate. The ethyl acetate layer was washed with water and dried (MgSO4), after which the solvent was distilled off. The residue was subjected to silica gel column chromatography and eluted with ethyl acetate-hexane (1:3, v/v) to yield an oily substance (4.26 g). This oily substance was dissolved in acetic acid-concentrated hydrochloric acid (1:1, 30 ml) and heated for 1 hour while refluxing. After cooling, the reaction mixture was poured over water (150 ml) and stirred at room temperature for 10 minutes. The separated crystals were collected by filtration to yield 3-methyl-4-oxo-4H-1-benzopyran-2-carboxylic acid (2.62 g, 13%), which was then recrystallized from ethanol to yield colorless prisms having a melting point of 192° to 193° C.

1. temperaturethe mixture was heated for 2.5 hours
2. temperaturewhile refluxing
3. temperatureThe mixture was cooled
4. extractionextracted with ethyl acetate
5. washThe ethyl acetate layer was washed with water
6. dry with materialdried (MgSO4)
7. distillationafter which the solvent was distilled off
8. washeluted with ethyl acetate-hexane (1:3
9. customv/v) to yield an oily substance (4.26 g)
10. temperatureheated for 1 hour
11. temperaturewhile refluxing
12. temperatureAfter cooling
13. filtrationThe separated crystals were collected by filtration