Reacción #1552051

Ecuación de reacción

bromide

18-Bromo-octadeca-6,9-diene

ether

ether

cyanide

18-Cyano-octadeca-6,9-diene

ether

→

ketone

Rendimiento 74.0%

Heptatriaconta-6,9,28,31-tetraen-19-one

Rendimiento 74.0%

Condiciones de reacción

Tratamiento posterior

1. 1
   OtroTo a flame dried 500 mL 2NRB flask
2. 2
   Otrothe flask was equipped with a magnetic stir bar and a reflux condenser
3. 3
   OtroThis set-up was degassed
4. 4
   Otroflushed with argon and 10 mL of anhydrous ether
5. 5
   workup.ADDITIONwas added to the flask via syringe
6. 6
   workup.ADDITIONadded dropwise via syringe to the flask
7. 7
   OtroAn exothermic reaction
8. 8
   workup.ADDITIONwas added
9. 9
   Temperaturastarted refluxing
10. 10
    workup.ADDITIONAfter the completion of the addition the reaction mixture
11. 11
    Temperaturacooled in ice bath
12. 12
    workup.ADDITIONadded dropwise to the reaction mixture
13. 13
    OtroAn exothermic reaction
14. 14
    workup.STIRRINGthe reaction mixture was stirred overnight at ambient temperature
15. 15
    OtroThe reaction was quenched
16. 16
    workup.ADDITIONby adding 10 mL of acetone
17. 17
    workup.ADDITIONThe reaction mixture was treated with aq. H2SO4 (10% by volume, 200 mL) until the solution
18. 18
    Otrothe layers were separated
19. 19
    ExtracciónThe aq. phase was extracted with ether (2×100 mL)
20. 20
    SecadoThe combined ether layers were dried (Na2SO4)
21. 21
    Concentraciónconcentrated
22. 22
    Otroto get the crude product which
23. 23
    Otrowas purified by column (silica gel, 0-10% ether in hexanes) chromatography
24. 24
    OtroThe pure product fractions were evaporated

Procedimiento

To a flame dried 500 mL 2NRB flask, freshly activated Mg turnings (0.144 g, 6 mmol) were added and the flask was equipped with a magnetic stir bar and a reflux condenser. This set-up was degassed, flushed with argon and 10 mL of anhydrous ether was added to the flask via syringe. The bromide 3 (1.65 g, 5 mmol) was dissolved in anhydrous ether (10 mL) and added dropwise via syringe to the flask. An exothermic reaction was noticed (to confirm/accelerate the Grignard reagent formation, 2 mg of iodine was added and immediate decolorization was observed confirming the formation of the Grignard reagent) and the ether started refluxing. After the completion of the addition the reaction mixture was kept at 35° C. for 1 h and then cooled in ice bath. The cyanide 4 (1.38 g, 5 mmol) was dissolved in anhydrous ether (20 mL) and added dropwise to the reaction mixture with stirring. An exothermic reaction was observed and the reaction mixture was stirred overnight at ambient temperature. The reaction was quenched by adding 10 mL of acetone dropwise followed by ice cold water (60 mL). The reaction mixture was treated with aq. H2SO4 (10% by volume, 200 mL) until the solution became homogeneous and the layers were separated. The aq. phase was extracted with ether (2×100 mL). The combined ether layers were dried (Na2SO4) and concentrated to get the crude product which was purified by column (silica gel, 0-10% ether in hexanes) chromatography. The pure product fractions were evaporated to provide the pure ketone 7 as a colorless oil (2 g, 74%). 1H NMR (CDCl3, 400 MHz) δ=5.33-5.21 (m, 8H), 2.69 (t, 4H), 2.30 (t, 4H), 2.05-1.95 (m, 8H), 1.55-1.45 (m, 2H), 1.35-1.15 (m, 18H), 0.82 (t, 3H). 13C NMR (CDCl3) δ=211.90, 130.63, 130.54, 128.47, 128.41, 43.27, 33.04, 32.01, 30.93, 29.89, 29.86, 29.75, 29.74, 27.69, 26.11, 24.35, 23.06, 14.05. MS. Molecular weight calculated for C37H66O, Cal. 526.92. Found 528.02 (M+H+).

Fuente