Boron trifluoride etherate → 2,3-dihydro-1H-indol-5-ol

HRID 454191Notes

Reaction equation

HRID 454191 reaction equation
[OH:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH:6]=[CH:5]2.C([BH3-])#N.[Na+].B(F)(F)F.CCOCC>CO>[OH:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH2:6][CH2:5]2

Participants

5

Reactant 3

HCID 8000Boron trifluoride etherateHCID 160545-HydroxyindoleHCID 5003444Sodium cyanoborohydride

Product 1

HCID 100346842,3-dihydro-1H-indol-5-olYield 73%

Reagents, catalysts & solvents 1

HCID 887MethanolSolvent

Procedure

5-Hydroxyindole (2 g, 15 mmol) was dissolved in methanol (60 ml) under argon. Sodium cyanoborohydride (1.89 g, 30 mmol) and trifluoroboron etherate (4.2 ml, 33 mmol) were added and the mixture was heated at reflux for 3 hours then left to cool to ambient temperature. The solvent was evaporated and the residue was partitioned between ethyl acetate and water. Ammonia was added to adjust the pH to 10 and the aqueous phase was extracted with more ethyl acetate. The combined organic phases were washed with water, brine, dried (MgSO4), filtered and the solvent evaporated. The residue was purified by flash chromatography using dichloromethane/methanol (95/5) as solvent. Evaporation of the solvent gave 5-hydroxy-2,3-dihydro-1H-indole (1.45 g, 73%) as an off white solid.

Workup

  1. temperaturethe mixture was heated
  2. temperatureat reflux for 3 hours
  3. waitthen left
  4. customThe solvent was evaporated
  5. customthe residue was partitioned between ethyl acetate and water
  6. additionAmmonia was added
  7. extractionthe aqueous phase was extracted with more ethyl acetate
  8. washThe combined organic phases were washed with water, brine
  9. dry with materialdried (MgSO4)
  10. filtrationfiltered
  11. customthe solvent evaporated
  12. customThe residue was purified by flash chromatography
  13. customEvaporation of the solvent

Sources & evidence

ORD record
ord-b372ae32ecc046f1857ba9e2446e568d
Source dataset
uspto-grants-2013_07
Patent number
US08492560B2

Reaction notes

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