Reaktion #3155

Reaktionsgleichung

hydrochloric acid

bromine

sodium hydroxide

5-acetyl-2-methyl coumaran

hypobromous acid

→

5-carboxy-2-methylcoumaran

Ausbeute 57.4%

Lösungsmittel

water

dioxane

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturcooling
2. 2
   Temperaturunder cooling on an ice bath
3. 3
   SonstigeThe ice bath was removed
4. 4
   workup.ADDITIONafter the addition
5. 5
   workup.STIRRINGThe resultant mixture was stirred for 3.5 hours at room temperature
6. 6
   SonstigeAfter the reaction
7. 7
   Sonstigeto precipitate a crystal
8. 8
   FiltrationThe crystal was recovered by filtration
9. 9
   Waschenwashed with water
10. 10
    SonstigeThe resultant crystal was dried under reduced pressure
11. 11
    Waschenby washing with hexane and isopropyl ether successively

Vorschrift

On an ice-common salt bath, 6.25 ml of bromine was added dropwise to a solution of 15.1 g of sodium hydroxide in 100 ml of water under stirring and cooling. To a solution of 6.50 g of 5-acetyl-2-methyl coumaran (Ml) in 100 ml of dioxane, the above mixture (i.e., hypobromous acid solution) was added dropwise at 3°-8° C. under cooling on an ice bath. The ice bath was removed after the addition. The resultant mixture was stirred for 3.5 hours at room temperature. After the reaction, the reaction mixture was poured into 500 ml of ice water, followed by addition of 30 ml of hydrochloric acid to precipitate a crystal. The crystal was recovered by filtration and washed with water. The resultant crystal was dried under reduced pressure, followed by washing with hexane and isopropyl ether successively to obtain 3.77 g of 5-carboxy-2-methylcoumaran (M2) (Yield: 57.4%).

Quelle