Ethanol → 4-Hydroxy-benzo[b]thiophene-7-carboxaldehyde

HRID 854415Notes

Reaction equation

HRID 854415 reaction equation
[OH:1][CH:2]([C:6]1[C:11]2[S:12][CH:13]=[CH:14][C:10]=2[C:9]([OH:15])=[CH:8][CH:7]=1)C([O-])=O.C([NH+](CCCC)CCCC)CCC.C(O)C.S(=O)(=O)(O)O.C(OC(C)C)(=O)C>S([O-])([O-])(=O)=O.[Fe+3].S([O-])([O-])(=O)=O.S([O-])([O-])(=O)=O.[Fe+3].O>[OH:15][C:9]1[C:10]2[CH:14]=[CH:13][S:12][C:11]=2[C:6]([CH:2]=[O:1])=[CH:7][CH:8]=1

Participants

7

Reactant 4

HCID 702EthanolHCID 1118Sulfuric AcidHCID 7915Isopropyl AcetateHCID 69292936Tributylammonium hydroxy-(4-hydroxy-benzo[b]thiophen-7-yl)-acetate

Product 1

HCID 111829574-Hydroxy-benzo[b]thiophene-7-carboxaldehydeYield 96.7%

Reagents, catalysts & solvents 2

HCID 24826Ferric SulfateCatalystHCID 962WaterSolvent

Conditions

Temperature
57.5 °C

Procedure

A 750 ml, 4-necked glass flask equipped with a mechanical stirrer, a thermometer, a dropping funnel and an argon inlet was charged under argon with 41.0 g (100 mmol) of tributylammonium hydroxy-(4-hydroxy-benzo[b]thiophen-7-yl)-acetate, 60.5 g (115 mmol) of iron(III) sulfate and a mixture prepared from 60 ml of dry ethanol and 300 ml of 0.4 N sulfuric acid aqueous solution. Then stirring was started and the reaction mixture was heated to 55-60° C. for 5 h. After cooling to room temperature, 300 ml of isopropyl acetate and 100 ml of water were added under stirring, then the organic phase was separated and transferred into a 500 ml glass flask equipped with a pH meter. After addition of 150 ml of water (pH was 3.0), ca. 58 ml of a 2 N sodium hydroxide aqueous solution were added dropwise at 20° C. until a pH of 12-12.5 was reached. The organic phase was removed and to the aqueous phase were added at 10-15° C. dropwise ca. 54 ml of a 2 N aqueous solution of sulfuric acid until a pH of 4-4.5 was reached. The product precipitated during the addition. The suspension was stirred over night at room temperature, 1.2 h in an ice bath and then filtered. The filter cake was washed with water and dried at 60° C./15 mbar to afford 17.23 g (94%) of 4-hydroxy-benzo[b]thiophene-7-carboxaldehyde as white crystals with m.p. of 204° C.

Workup

  1. customA 750 ml, 4-necked glass flask equipped with a mechanical stirrer
  2. temperatureAfter cooling to room temperature
  3. stirringunder stirring
  4. customthe organic phase was separated
  5. customtransferred into a 500 ml glass flask
  6. customequipped with a pH meter
  7. additionAfter addition of 150 ml of water (pH was 3.0), ca. 58 ml of a 2 N sodium hydroxide aqueous solution
  8. additionwere added dropwise at 20° C. until a pH of 12-12.5
  9. customThe organic phase was removed and to the aqueous phase
  10. additionwere added at 10-15° C. dropwise ca. 54 ml of a 2 N aqueous solution of sulfuric acid until a pH of 4-4.5
  11. customThe product precipitated during the addition
  12. stirringThe suspension was stirred over night at room temperature, 1.2 h in an ice bath
  13. filtrationfiltered
  14. washThe filter cake was washed with water
  15. customdried at 60° C./15 mbar

Sources & evidence

ORD record
ord-8257eea2694443ee9556d325cbe990f3
Source dataset
uspto-grants-2007_08
Patent number
US07259176B2

Reaction notes

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