Reaktion #3780

Reaktionsgleichung

magnesium methylbromide

2,5-difluorobenzaldehyde

→

2',5'-difluoroacetophenone

Ausbeute 84.0%

Lösungsmittel

tetrahydrofuran

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   Waschenthe organic phase was washed in a saturated sodium chloride solution
2. 2
   Trocknendried over anhydrous magnesium sulfate
3. 3
   workup.DISTILLATIONto subsequently distill off the solvents under reduced pressure
4. 4
   workup.ADDITIONTo the residue were added anhydrous dichloromethane (500 ml), sodium acetate (14.2 g) and pyridinium chlorochromate (55.94 g)
5. 5
   workup.STIRRINGto stirring at room temperature for 10 hours
6. 6
   workup.ADDITIONTo the resulting mixture was added an aqueous saturated sodium hydrogen carbonate solution
7. 7
   Extraktionto extraction in ethyl acetate three times
8. 8
   WaschenThe organic phase was washed in water and in a saturated sodium chloride solution
9. 9
   Trocknendried over anhydrous magnesium sulfate
10. 10
    workup.DISTILLATIONto distill off the solvents under reduced pressure
11. 11
    SonstigeThe residue was purified by silica gel column chromatography (developing solvent: hexane:ethyl acetate=85:15)

Vorschrift

A solution (100 ml) of 2,5-difluorobenzaldehyde (24.6 g) in tetrahydrofuran was dropwise added to an ice-cooled solution (207 ml) of 0.92N magnesium methylbromide in tetrahydrofuran. The resulting solution was stirred at room temperature for 1.5 hours, and the organic phase was washed in a saturated sodium chloride solution and dried over anhydrous magnesium sulfate, to subsequently distill off the solvents under reduced pressure. To the residue were added anhydrous dichloromethane (500 ml), sodium acetate (14.2 g) and pyridinium chlorochromate (55.94 g), prior to stirring at room temperature for 10 hours. To the resulting mixture was added an aqueous saturated sodium hydrogen carbonate solution, prior to extraction in ethyl acetate three times. The organic phase was washed in water and in a saturated sodium chloride solution and dried over anhydrous magnesium sulfate, to distill off the solvents under reduced pressure. The residue was purified by silica gel column chromatography (developing solvent: hexane:ethyl acetate=85:15), to recover 2',5'-difluoroacetophenone (22.73 g; yield of 84%). By 1H-NMR (90 MHz, CDCl3), the compound has the peaks shown below.

Quelle