Reaktion #607441

Reaktionsgleichung

3′,5′-difluoroacetophenone

acetaldehyde

→

title compound

Ausbeute 40.0%

(−)-(S)-1-(3,5-difluorophenyl)ethanol

Ausbeute 40.0%

Lösungsmittel

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturcooled to −27° C. to −25° C.
2. 2
   TemperaturThe reaction was maintained at this temperature for 17 h
3. 3
   Sonstigeto reach room temperature
4. 4
   SonstigeThe solvent was then removed in vacuo
5. 5
   Sonstigethe resulting residue was partitioned between water (10 mL) and TBME (tert-butyl-methyl ether) (20 mL)
6. 6
   ExtraktionThe aqueous phase was extracted again with TBME (20 mL)
7. 7
   WaschenThe organic layer was washed with an aqueous 2 N NaOH solution (20 mL), brine (20 mL)
8. 8
   Trocknendried over anhydrous Na2SO4
9. 9
   Filtrationfiltered
10. 10
    SonstigeThe solvent was removed in vacuo
11. 11
    Sonstigeto give a residue, which
12. 12
    Sonstigewas purified by two subsequent column chromatographic steps

Vorschrift

To a stirred solution of (−)-DIP-Cl ((−)-diisopinocampheylboron chloride) (2.67 g, 8.33 mmol, 1.3 eq) in THF (20 mL) kept under inert atmosphere (Ar) and cooled to −27° C. to −25° C., 3′,5′-difluoroacetophenone (1.00 g, 6.40 mmol) was added drop wise over 2 min. The reaction was maintained at this temperature for 17 h. The reaction mixture was then treated with acetaldehyde (0.44 mL, 7.69 mmol, 1.2 eq). Thereafter, the temperature was allowed to reach room temperature and the reaction mixture was stirred at for 7 h. The solvent was then removed in vacuo and the resulting residue was partitioned between water (10 mL) and TBME (tert-butyl-methyl ether) (20 mL). The aqueous phase was extracted again with TBME (20 mL). The organic layer was washed with an aqueous 2 N NaOH solution (20 mL), brine (20 mL), dried over anhydrous Na2SO4 and filtered. The solvent was removed in vacuo to give a residue, which was purified by two subsequent column chromatographic steps: First by normal phase chromatography (silica gel, heptane/ethyl acetate, v/v=1/0-9/1) followed by a reversed phase chromatography (90 C18-silica gel, acetonitrile for the second one). This gave the title compound (0.40 g, 40%) as a colorless oil with a specific rotation of [α]25D=−26.66 (c=1.054 g/100 mL, CH2Cl2, 589 nm).

Quelle