反应详情

89.5 g (0.43 mol) of 4-butoxyphenylacetic acid (prepared by the method of McElvain, Carney; J. Am. Chem. Soc. 1946 (68), 2592-2599) and 30.0 g (0.22 mol) of 2,4-dihydroxybenzaldehyde are heated at 120° C. for 5 h in 100 ml of acetic anhydride and 120 ml of triethylamine. The still-hot solution is subsequently added to 3 l of ice-water, and the precipitated product is filtered off with suction and suspended in 1 l of water and 1.4 l of ethanol. After dropwise addition of 190 ml of conc. sulfuric acid, the batch is heated under reflux for 4 h and added to 3 l of water, and the precipitated product is filtered off with suction. The crude product is filtered through silica gel with hot toluene/ethyl acetate (1:1), the solvent is evaporated in vacuo, and the residue is recrystallised from toluene, giving 3-(4-butoxyphenyl)-7-hydroxychromen-2-one as colourless crystals.

1. filtrationthe precipitated product is filtered off with suction
2. additionAfter dropwise addition of 190 ml of conc. sulfuric acid
3. temperaturethe batch is heated
4. temperatureunder reflux for 4 h
5. additionadded to 3 l of water
6. filtrationthe precipitated product is filtered off with suction
7. filtrationThe crude product is filtered through silica gel with hot toluene/ethyl acetate (1:1)
8. customthe solvent is evaporated in vacuo
9. customthe residue is recrystallised from toluene