Réaction #77596

Équation de réaction

sulphuric acid

(3-carboxypropyl)triphenylphosphonium bromide

1-(5-bromo-2-thienyl)ethanone

potassium tert-butoxide

→

Ethyl (E)-5-(Bromo-2-thienyl)-4-hexenoate

Solvants

ethanol

THF

THF

THF

Conditions de réaction

Traitement

1. 1
   Températurecooled to room temperature
2. 2
   workup.STIRRINGthe reaction medium is stirred for 15 hours
3. 3
   ExtractionAfter treatment with saturated ammonium chloride solution, extraction with ethyl acetate
4. 4
   Autredrying
5. 5
   Autreevaporation of the solvents from the organic phase
6. 6
   Autrethe residue obtained
7. 7
   Autreis purified by chromatography on a column of silica
8. 8
   AutreAn ochre-coloured solid is obtained (m.p.: 62-64° C., m=5.8 g; Y=62%)
9. 9
   Températureto reflux
10. 10
    workup.STIRRINGstirred for 2 hours
11. 11
    ExtractionAfter treatment with water, the medium is extracted with ethyl acetate
12. 12
    Autredried
13. 13
    Concentrationconcentrated under reduced pressure
14. 14
    AutreThe residue obtained
15. 15
    Autreis purified by chromatography on a column of silica (eluent: 95 heptane/5 ethyl acetate)
16. 16
    Autreto give the pure trans isomer in the form of a yellow oil (m=3.4 g; Y=77%)

Mode opératoire

22.2 g (51.7 mmol) of (3-carboxypropyl)triphenylphosphonium bromide are dried under vacuum for 1 h with heating at 130° C., and then cooled to room temperature and dissolved in 200 mL of anhydrous THF. 11.5 g (102.5 mmol) of potassium tert-butoxide in 100 mL of THF are then added slowly, after which the orange-red mixture is stirred for 15 minutes. A solution of 7 g (34 mmol) of 1-(5-bromo-2-thienyl)ethanone in 100 mL of THF is then added dropwise and the reaction medium is stirred for 15 hours. After treatment with saturated ammonium chloride solution, extraction with ethyl acetate, drying and evaporation of the solvents from the organic phase, the residue obtained is purified by chromatography on a column of silica. An ochre-coloured solid is obtained (m.p.: 62-64° C., m=5.8 g; Y=62%). This product is then dissolved in 100 mL of ethanol and 2 mL of sulphuric acid are then added. The reaction medium is brought to reflux and stirred for 2 hours. After treatment with water, the medium is extracted with ethyl acetate and the organic phases are then combined, dried and concentrated under reduced pressure. The residue obtained is purified by chromatography on a column of silica (eluent: 95 heptane/5 ethyl acetate) to give the pure trans isomer in the form of a yellow oil (m=3.4 g; Y=77%).

Source