Reaktion #50452

Reaktionsgleichung

3-methoxy-phthalic acid anhydride

malonic acid

triethylamine

CO2

→

3-hydroxy-7-methoxy-3-methyl-phthalide

Lösungsmittel

water

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigebecomes stirrable at 55° C. and, from 68° C.
2. 2
   Temperaturthe reaction mixture is then heated
3. 3
   Temperaturat reflux temperature (internal temperature 85° C.) for a further 4 hours
4. 4
   TemperaturWhen it has cooled
5. 5
   Extraktionextracted with ethyl acetate
6. 6
   Extraktionextracted three times with fresh ethyl acetate
7. 7
   Trocknendried over anhydrous sodium sulfate
8. 8
   Einengenconcentrated by evaporation under reduced pressure
9. 9
   SonstigeFractional crystallisation (ethyl acetate/n-hexane)

Vorschrift

5.4 g of 3-methoxy-phthalic acid anhydride [see A. V. R. Rao et al., Indian J. Chem. 20B, 248 ff. (1981)], 4.7 g of malonic acid and 9 ml of triethylamine are heated slowly. The suspension becomes stirrable at 55° C. and, from 68° C., moderately vigorous CO2 evolution occurs. The internal temperature is maintained at 73° C. until gas evolution ceases (about 1 hour) and the reaction mixture is then heated at reflux temperature (internal temperature 85° C.) for a further 4 hours. When it has cooled, the reaction mixture is treated with water and extracted with ethyl acetate. The aqueous phase is then adjusted to pH 1.7 and extracted three times with fresh ethyl acetate, dried over anhydrous sodium sulfate and concentrated by evaporation under reduced pressure. Fractional crystallisation (ethyl acetate/n-hexane) yields 3-hydroxy-7-methoxy-3-methyl-phthalide, m.p. 156°-158° C.; IR spectrum (CHCl3): C=O 1772 cm-1.

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