Reaktion #49683

Reaktionsgleichung

phosphorus tribromide

4-cyanophenethyl alcohol

→

4-cyanophenethyl bromide

Lösungsmittel

carbon tetrachloride

carbon tetrachloride

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe mixture was heated
2. 2
   Temperaturunder reflux for 4 hours
3. 3
   workup.ADDITIONthe mixture was poured onto ice (200 g)
4. 4
   SonstigeThe layers were separated
5. 5
   Waschenthe organic layer was washed with 10% aqueous sodium carbonate (50 ml) and brine (50 ml)
6. 6
   Trocknendried (MgSO4)
7. 7
   Einengenconcentrated in vacuo
8. 8
   Sonstigeto give a colourless oil which
9. 9
   SonstigeThe solid was chromatographed on silica eluting with ethyl acetate
10. 10
    workup.ADDITIONcontaining hexane (20%)
11. 11
    workup.ADDITIONThe fractions containing the less polar (higher Rf) product
12. 12
    Einengenconcentrated in vacuo

Vorschrift

A solution of phosphorus tribromide (5 g) in carbon tetrachloride (10 ml) was added, dropwise, to a solution of 4-cyanophenethyl alcohol (8.06 g) in carbon tetrachloride (60 ml). The mixture was heated under reflux for 4 hours. On cooling to room temperature, the mixture was poured onto ice (200 g). The layers were separated and the organic layer was washed with 10% aqueous sodium carbonate (50 ml) and brine (50 ml), dried (MgSO4) and concentrated in vacuo to give a colourless oil which solidified on standing. The solid was chromatographed on silica eluting with ethyl acetate containing hexane (20%). The fractions containing the less polar (higher Rf) product were combined and concentrated in vacuo to give 4-cyanophenethyl bromide as a yellow oil which solidified on standing, yield 8.9 g. The fractions containing the more polar (lower Rf) product were combined and concentrated in vacuo to give the title compound as a colourless solid, yield 0.47 g, m.p. 152°-153° .

Quelle