反应详情

A stirred solution of 25.0 grams (0.15 mole) of 2,5-dimethoxybenzaldehyde, 22.0 grams (0.17 mole) of ethyl acetoacetate, 2 mL of pipeddine, and 3 mL of glacial acetic acid in about 250 mL of toluene is placed in a reaction vessel equipped with a Dean-Stark trap, and heated at reflux for about 12 hours. After this time, the reaction mixture is cooled and washed in turn with water, a cold solution of aqueous 10% hydrochloric acid, aqueous 5% sodium bicarbonate, and aqueous 1% acetic acid. The organic layer is dried with magnesium sulfate and filtered. The filtrate is concentrated under reduced pressure to a residue. The residue is subjected to column chromatography on silica gel. Elution is accomplished using methylene chloride The column chromatography does not provide product purification as expected. The fractions are recombined and concentrated under reduced pressure to a residual oil. The oil is distilled under vacuum, yielding 32 grams of impure ethyl 3-oxo-2-(2,5-dimethoxyphenylmethylidene)butanoate. The NMR spectrum is consistent with the proposed structure.

1. customequipped with a Dean-Stark trap
2. temperatureheated
3. temperatureat reflux for about 12 hours
4. temperatureAfter this time, the reaction mixture is cooled
5. washwashed in turn with water
6. dry with materialThe organic layer is dried with magnesium sulfate
7. filtrationfiltered
8. concentrationThe filtrate is concentrated under reduced pressure to a residue
9. washElution
10. customdoes not provide
11. customproduct purification
12. concentrationconcentrated under reduced pressure to a residual oil
13. distillationThe oil is distilled under vacuum