反应详情

A mixture of 2,5-dimethoxybenzaldehyde (100 g), ethyl acetoacetate (84.5 g), anhydrous benzene (200 ml), piperidine (6 ml) and acetic acid (12 ml) was heated at reflux for 3 hours in an apparatus fitted with a Dean-Stark trap to collect the azeotropically distilled water. The reaction mixture was cooled, benzene (300 ml) added, and the solution was washed successively with water (100 ml), cooled 0.1N hydrochloric acid (200 ml), 5% aqueous sodium bicarbonate (200 ml) and dilute acetic acid (100 ml) and dried over anhydrous magnesium sulfate. The solvent was then removed under reduced pressure and the residual oil distilled, b.p. 169°-170° C./0.3 mm Hg. The product, ethyl α-(2,5-dimethoxybenzylidene)acetoacetate, solidified on standing (104 g, m.p. 68°-69° C.) and was recrystallised from ethanol-pentane (m.p. 72°-73° C.). A portion (38 g) of the product was reduced catalytically in the presence of palladium on charcoal catalyst (Pd/C) in ethyl acetate (150 ml). The product, after removal of solvent, was purified by distillation under reduced pressure to give ethyl α-(2,5-dimethoxybenzyl)acetoacetate, b.p. 146°-148° C./0.3 mm Hg.

1. temperaturewas heated
2. temperatureat reflux for 3 hours in an apparatus
3. customfitted with a Dean-Stark trap
4. distillationto collect the azeotropically distilled water
5. temperatureThe reaction mixture was cooled
6. additionbenzene (300 ml) added
7. washthe solution was washed successively with water (100 ml)
8. temperaturecooled 0.1N hydrochloric acid (200 ml), 5% aqueous sodium bicarbonate (200 ml) and dilute acetic acid (100 ml)
9. dry with materialdried over anhydrous magnesium sulfate
10. customThe solvent was then removed under reduced pressure
11. distillationthe residual oil distilled
12. customwas recrystallised from ethanol-pentane (m.p. 72°-73° C.)
13. customThe product, after removal of solvent
14. distillationwas purified by distillation under reduced pressure