Reaction #55201

Reaction equation

potassium hydroxide

triphenylphosphoranylideneacetic acid ethyl ester

4-(1-bromoethyl)-2',4'-difluorobiphenyl

ethyl acetate

→

3-(2',4'-difluoro-4-biphenylyl)butyric acid

Solvents

methanol

Conditions

Workup

1. 1
   Temperatureunder reflux for 54 hours
2. 2
   FiltrationThe precipitate is filtered off
3. 3
   Otherthe filtrate is evaporated
4. 4
   OtherCrude [1-(2',4'-difluoro-4-biphenylyl)ethyl]-triphenylphosphoranylideneacetic acid ethyl ester thus obtained
5. 5
   workup.DISSOLUTIONis dissolved in 500 ml
6. 6
   Temperaturethe mixture is heated
7. 7
   Temperatureunder reflux for one hour
8. 8
   workup.DISTILLATIONThe methanol is distilled off
9. 9
   workup.ADDITIONwater is added
10. 10
    Washthe reaction mixture is washed with ether

Procedure

69.7 g. of triphenylphosphoranylideneacetic acid ethyl ester and 29.7 g. of 4-(1-bromoethyl)-2',4'-difluorobiphenyl in 300 ml. of absolute ethyl acetate are heated under reflux for 54 hours. The precipitate is filtered off and the filtrate is evaporated. Crude [1-(2',4'-difluoro-4-biphenylyl)ethyl]-triphenylphosphoranylideneacetic acid ethyl ester thus obtained is dissolved in 500 ml. of methanol to which 150 ml. of 20% potassium hydroxide solution are added and the mixture is heated under reflux for one hour. The methanol is distilled off, water is added and the reaction mixture is washed with ether and acidified with hydrochloric acid to give 3-(2',4'-difluoro-4-biphenylyl)butyric acid, m.p. 109°-110°.

Source