Reaction #302896

Reaction equation

water

n-butyllithium

1-fluoro-2-methylthio-3-(trifluoromethyl)benzene

carbon dioxide

→

crude product

2-fluoro-3-methylthio-4-(trifluoromethyl)benzoic acid

Solvents

Diethyl ether

THF

Conditions

Workup

1. 1
   Otherexceed −65° C
2. 2
   Otherdid not exceed −45° C
3. 3
   TemperatureThe mixture was then warmed to RT
4. 4
   Temperatureonce more cooled to 0° C
5. 5
   Otherformed
6. 6
   workup.DISSOLUTIONhad dissolved
7. 7
   Extractionthe organic phase was extracted three times with water
8. 8
   ExtractionThe aqueous phase was extracted repeatedly with dichloromethane
9. 9
   Washthe combined organic phases were washed with saturated aqueous NaCl solution
10. 10
    Dryingdried over sodium sulfate

Procedure

Under an atmosphere of inert gas, 27.5 ml (1.6 M in hexane, 44 mmol) of n-butyllithium were added dropwise to a solution, cooled to −78° C., of 7.98 g (38 mmol) of 1-fluoro-2-methylthio-3-(trifluoromethyl)benzene in 60 ml of anhydrous THF, where the temperature of the reaction mixture should not exceed −65° C. The mixture was stirred at −78° C. for 3 h, and at this temperature a carbon dioxide stream was then introduced such that the temperature of the reaction mixture did not exceed −45° C. The mixture was then warmed to RT and then once more cooled to 0° C. For work-up, water was added dropwise at this temperature until the precipitate formed had dissolved. Diethyl ether was added, and the organic phase was extracted three times with water. The combined aqueous phases were acidified with 10 percent strength hydrochloric acid. The aqueous phase was extracted repeatedly with dichloromethane, the combined organic phases were washed with saturated aqueous NaCl solution and dried over sodium sulfate and the filtrate was then freed from the solvent. The crude product obtained in this manner was then recrystallized from gasoline (80-110° C.)/ethyl acetate. This gave 6.8 g of 2-fluoro-3-methylthio-4-(trifluoromethyl)benzoic acid.

Source