Reaktion #2319653

Reaktionsgleichung

3,3',5'-tribromo-6,4'-dihydroxy-3-methylflavanone

bromine

3',5'-dibromo-6,4'-dihydroxy-3-methylflavanone

piperidine

potassium hydroxide

2,5-dihydroxypropiophenone

3,5-dibromo-4-hydroxybenzaldehyde

→

3',5'-Dibrom-6,4'-dihydroxy-3-methylflavone

Lösungsmittel

ethanol

ethanol

chloroform

dioxane

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigeirradiating (500 watt Agaphot lamp)
2. 2
   workup.STIRRINGThe mixture is stirred for a further 30 minutes
3. 3
   Temperaturwhile cooling
4. 4
   Sonstigeirradiating
5. 5
   Temperaturcooled
6. 6
   workup.ADDITIONpoured on to ice

Vorschrift

1.6 g of bromine in 6 ml of chloroform are added dropwise to a solution of 4.12 g of 3',5'-dibromo-6,4'-dihydroxy-3-methylflavanone (m.p. 200°-202°; obtainable by reaction of 2,5-dihydroxypropiophenone with 3,5-dibromo-4-hydroxybenzaldehyde in boiling ethanol in the presence of piperidine) in 55 ml of dioxane while stirring and irradiating (500 watt Agaphot lamp). The mixture is stirred for a further 30 minutes while cooling and irradiating, the usual working-up is carried out, and the resulting crude 3,3',5'-tribromo-6,4'-dihydroxy-3-methylflavanone is dissolved in 100 ml of ethanol. 15 ml of 10% aqueous potassium hydroxide solution are added, and the mixture is boiled for 5 minutes, cooled, poured on to ice and the usual working-up is carried out. 3',5'-Dibrom-6,4'-dihydroxy-3-methylflavone ("D") is obtained, m.p. 264°-265°.

Quelle