Reaktion #46937

Reaktionsgleichung

acetic anhydride

n-Butyl lithium

o-bromostyrene

bromide

dry ice isopropanol

2-bromobenzaldehyde

magnesium

o-bromostyrene

→

o-vinyl acetophenone

Lösungsmittel

THF

THF

THF

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeInto a 3 necked 500 mL round bottom flask, equipped with a cooling condenser
2. 2
   workup.ADDITIONaddition funnel
3. 3
   workup.ADDITIONwas added via a syringe
4. 4
   Sonstigewas dripped into the flask slowly (2 hours)
5. 5
   workup.STIRRINGAfter stirred for 48 hours
6. 6
   Sonstigethe reaction mixture was quenched with brine (250 mL)
7. 7
   ExtraktionThe aqueous layer was extracted with toluene (100 mL×2)
8. 8
   workup.ADDITIONThe toluene layer was diluted with hexane
9. 9
   Sonstigeto precipitate triphenylphosphine oxide
10. 10
    SonstigeAfter rotary evaporating off the solvent
11. 11
    Sonstigethe crude product was purified by column chromatography (silica gel 60-200 mesh), with 100% hexane
12. 12
    SonstigeInto a 3-necked round bottom flask fitted with condenser, self-equalizing funnel
13. 13
    workup.ADDITIONwas added
14. 14
    SonstigeAfter initiation of the reaction
15. 15
    Temperaturthe mixture was refluxed for 1.5 hours
16. 16
    Sonstige(circa 1 hour)
17. 17
    workup.STIRRINGthe mixture was stirred for 2.5 hours at −70° C
18. 18
    Sonstigethe mixture was then quenched with aqueous ammonium chloride
19. 19
    Extraktionextracted with ethyl acetate (100 mL×2)
20. 20
    WaschenAfter washing with water
21. 21
    Trocknendried over sodium sulfate and removal of the solvent
22. 22
    Sonstigeyellow oil was obtained
23. 23
    Sonstigeabove did not provide a clean product

Vorschrift

Into a 3 necked 500 mL round bottom flask, equipped with a cooling condenser, a self equalizing addition funnel and a rubber septum, methyl triphenyl phosphonium bromide (54.5 g, 0.153 moles, Aldrich) was suspended in THF (120 mL). After flashing with nitrogen for 30 minutes, the flask was cooled to 0° C. n-Butyl lithium (61 mL, 2.5 M in hexane, 153 mmole) was added via a syringe. After stirring for 1.5 hours, a solution of 2-bromobenzaldehyde (25.0 g, 135.1 mmole) in THF (100 mL) was dripped into the flask slowly (2 hours). After stirred for 48 hours, the reaction mixture was quenched with brine (250 mL). The aqueous layer was extracted with toluene (100 mL×2). The toluene layer was diluted with hexane to precipitate triphenylphosphine oxide. After rotary evaporating off the solvent, the crude product was purified by column chromatography (silica gel 60-200 mesh), with 100% hexane as eluding solvent. First fraction, yield 11.5 g (41%). 8.8 Grams (48 mmole) of o-bromostyrene was used for the next reaction. Into a 3-necked round bottom flask fitted with condenser, self-equalizing funnel, a stopper and charged with magnesium (10 g, pre-activated), o-bromostyrene in 30 mL THF was added to cover Mg. After initiation of the reaction, the rest of bromide solution was added slowly and the mixture was refluxed for 1.5 hours. Into another 3-necked flask, acetic anhydride (10 g, 98 mmole) was dissolved in THF (30 mL) and the flask was cooled with dry ice/isopropanol. The Grignard reagent was transferred slowly (circa 1 hour) via a cannula needle and the mixture was stirred for 2.5 hours at −70° C. After allowing to warm to room temperature, the mixture was then quenched with aqueous ammonium chloride and extracted with ethyl acetate (100 mL×2). After washing with water, dried over sodium sulfate and removal of the solvent, yellow oil was obtained. Yield: 6.5 gram (93%). 1H-NMR (CDCl3, δ): 5.3 (d, 1H), 5.6 (d, 1H); 7.2 (q, 1H), 7.3 (t, 1H), 7.4 (t, 1H); 7.55 (d, 1H); 7.6 (d, 1H). 13C-NMR: 30, 116, 127, 128, 130, 132, 136, 137.5, 138, 201. Epoxidation using a method similar to that described above did not provide a clean product.

Quelle