Iodine → 1-(Benzo[b]thiophen-4-yl)pent-4-en-1-one

HRID 2183681Notes

Reaction equation

HRID 2183681 reaction equation
Br[C:2]1[C:10]2[CH:9]=[CH:8][S:7][C:6]=2[CH:5]=[CH:4][CH:3]=1.[Mg].II.CON(C)[C:17](=[O:22])[CH2:18][CH2:19][CH:20]=[CH2:21]>O1CCCC1>[S:7]1[CH:8]=[CH:9][C:10]2[C:2]([C:17](=[O:22])[CH2:18][CH2:19][CH:20]=[CH2:21])=[CH:3][CH:4]=[CH:5][C:6]1=2

Participants

6

Reactant 4

HCID 807IodineHCID 5462224MagnesiumHCID 120942084-Bromobenzo[b]thiophene2×HCID 13350947N-Methoxy-N-methylpent-4-enamide

Product 1

HCID 224741961-(Benzo[b]thiophen-4-yl)pent-4-en-1-one

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent3×

Procedure

A few drops of a solution of 4-bromobenzo[b]thiophene (5 g; prepared in a manner similar to that described in Example 9 Method A) in tetrahydrofuran (10 ml) was added under nitrogen to magnesium turnings (0.6 g). Two crystals of iodine were added and heat was applied to initiate the reaction. The remainder of the 4-bromobenzo[b]thiophene solution was added at reflux temperature over 30 minutes, the mixture was heated under reflux for 2 hours, then further tetrahydrofuran (10 ml) was added. A solution of N-methoxy-N-methylpent-4-enamide (5 g) in tetrahydrofuran (5 ml) was added, the mixture was heated under reflux for 3 hours, then it was cooled to ambient temperature and quenched by the addition of water (100 ml) and 5M hydrochloric acid (5 ml). The product was extracted into ethyl acetate (3×60 ml), the combined extracts were washed with water (100 ml) and saturated aqueous sodium chloride solution (100 ml), then they were dried (MgSO4), and the solvents were removed in vacuo. The residue was purified by flash chromatography over silica using 99:1 followed by a 98:2 mixtures of petroleum ether (b.p. 40-60° C.) and ethyl acetate as eluants. Appropriate fractions were combined and the solvents removed in vacuo to give 1-(benzo[b]thiophen-4-yl)pent-4-en-1-one (1.6 g) as a colourless oil which was used without further purification.

Workup

  1. customprepared in a manner similar to
  2. temperatureheat
  3. customthe reaction
  4. temperatureat reflux temperature over 30 minutes
  5. temperaturethe mixture was heated
  6. temperatureunder reflux for 2 hours
  7. temperaturethe mixture was heated
  8. temperatureunder reflux for 3 hours
  9. customquenched by the addition of water (100 ml) and 5M hydrochloric acid (5 ml)
  10. extractionThe product was extracted into ethyl acetate (3×60 ml)
  11. washthe combined extracts were washed with water (100 ml) and saturated aqueous sodium chloride solution (100 ml)
  12. dry with materialthey were dried (MgSO4)
  13. customthe solvents were removed in vacuo
  14. customThe residue was purified by flash chromatography over silica using 99:1
  15. customthe solvents removed in vacuo

Sources & evidence

ORD record
ord-c52b28950b12480f872c21c3521c6cea
Source dataset
uspto-grants-2005_05
Patent number
US06900216B2

Reaction notes

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