反应详情

A solution of the oxazolone of Example 4 (1.80 g., 5.57 mM) and 3.06 g. of sodium hydroxide in 15.2 ml. of water is refluxed under nitrogen for two hours. The resulting solution is cooled, acidified with concentrated hydrochloric acid, and refluxed for 0.5 hour. The solution is cooled and filtered to separate the precipitated solids. The dried solid is triturated with 2 ml. of cold methanol (to remove benzoic acid) and filtered to separate the product, m.p. 251°-253°. Recrystallization from 12 ml. of methanol (charcoal) gives 8-methoxy-1-oxo-1H-2-benzopyran-3-carboxylic acid as a white solid, m.p. 255°-256°.

1. temperatureThe resulting solution is cooled
2. temperaturerefluxed for 0.5 hour
3. temperatureThe solution is cooled
4. filtrationfiltered
5. customto separate the precipitated solids
6. customThe dried solid is triturated with 2 ml
7. filtrationof cold methanol (to remove benzoic acid) and filtered
8. customto separate the product, m.p. 251°-253°
9. customRecrystallization from 12 ml