Reaktion #435417

Reaktionsgleichung

NH4Cl

1,1-diisopropoxy-2,2-dimethyl-3-pentanone

lithium diisopropylamide

(2S)-2-methyl-4-pentenal

→

(4R,5S,6S)-1,1-diisopropoxy-5-hydroxy-2,2,4,6-tetramethyl-8-nonen-3-one

Lösungsmittel

THF

THF

CH2Cl2

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturwarmed to −40° C.
2. 2
   workup.STIRRINGstirred for 30 minutes
3. 3
   Sonstigerecooled to −78° C
4. 4
   workup.STIRRINGthe mixture is stirred for 1 hour at −78° C
5. 5
   Temperaturthe mixture is warmed to ambient temperature
6. 6
   Extraktionextracted with ethyl acetate
7. 7
   TrocknenThe extract is dried over Na2SO4
8. 8
   Filtrationfiltered
9. 9
   Sonstigeevaporated
10. 10
    SonstigeThe residue is purified by silica gel chromatography (2% ethyl acetate/hexanes)
11. 11
    Sonstigeto separate the two diastereomeric products

Vorschrift

A solution of 1,1-diisopropoxy-2,2-dimethyl-3-pentanone (3.29 g) in 15 mL of THF is added slowly to a solution of lithium diisopropylamide (15.7 mmol) in 20 mL of THF cooled to −78° C., the mixture is stirred for 30 minutes, warmed to −40° C. and stirred for 30 minutes, then recooled to −78° C. A solution of (2S)-2-methyl-4-pentenal (16.36 mmol) in 2 mL of CH2Cl2 is added and the mixture is stirred for 1 hour at −78° C. Saturated aq. NH4Cl is added and the mixture is warmed to ambient temperature and extracted with ethyl acetate. The extract is dried over Na2SO4, filtered, and evaporated. The residue is purified by silica gel chromatography (2% ethyl acetate/hexanes) to separate the two diastereomeric products.

Quelle