Reaktion #471161

Reaktionsgleichung

magnesium

iodine

tetrahydrofuran

hydrochloric acid

5-Bromo-2-fluoro-1-benzofuran

tetrahydrofuran

→

2-Fluoro-5-formyl-1-benzofuran

Lösungsmittel

dimethylformamide

brine

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONA 1 ml portion of the solution was added to the slurry at 50° C.
2. 2
   workup.ADDITIONAfter 30 minutes the rest of the solution was added slowly
3. 3
   Temperaturthe reaction was heated
4. 4
   Temperaturat reflux for 3 hours
5. 5
   TemperaturThe reaction was cooled in an ice/water bath
6. 6
   Temperaturmaintaining the temperature below 10° C
7. 7
   workup.ADDITIONwas added
8. 8
   ExtraktionThe reaction mixture was extracted
9. 9
   WaschenThe combined organics were washed with brine
10. 10
    Trocknendried over anhydrous magnesium sulphate
11. 11
    SonstigeThe solvent was removed in vacuo
12. 12
    WaschenThis was eluted with cyclohexane, cyclohexane/ethyl acetate (6:1, 5:1 v/v)

Vorschrift

A slurry of magnesium powder (219 mg) and iodine (cat) in dry tetrahydrofuran (3 ml) was heated at 50° C. under nitrogen for 20 minutes. 5-Bromo-2-fluoro-1-benzofuran (1.4 g) was dissolved in dry tetrahydrofuran (6 ml). A 1 ml portion of the solution was added to the slurry at 50° C. without stirring. After 30 minutes the rest of the solution was added slowly and the reaction was heated at reflux for 3 hours. The reaction was cooled in an ice/water bath and dimethylformamide (1 ml) was added dropwise maintaining the temperature below 10° C. After 1 hour a mixture of 2N hydrochloric acid (12.5 ml) and brine (12.5 ml) was added. The reaction mixture was extracted using ethyl acetate (3×25 ml). The combined organics were washed with brine and dried over anhydrous magnesium sulphate. The solvent was removed in vacuo and the residue applied to a silica cartridge (50 g). This was eluted with cyclohexane, cyclohexane/ethyl acetate (6:1, 5:1 v/v). This gave 2-fluoro-5-formyl-1-benzofuran (376 mg).

Quelle