3,3,7-Tribromo-1,3-dihydro-2H-pyrrolo[3,2-c]pyridin-2-one → 1,3-Dihydro-2H-pyrrolo[3,2-c]pyridin-2-one

HRID 2394337Notes

Reaction equation

HRID 2394337 reaction equation
Br[C:2]1(Br)[C:10]2[C:5](=[C:6](Br)[CH:7]=[N:8][CH:9]=2)[NH:4][C:3]1=[O:12].[H][H]>C(O)C.[Pd]>[NH:4]1[C:5]2[C:10](=[CH:9][N:8]=[CH:7][CH:6]=2)[CH2:2][C:3]1=[O:12]

Participants

5

Reactant 2

HCID 156920293,3,7-Tribromo-1,3-dihydro-2H-pyrrolo[3,2-c]pyridin-2-oneHCID 178418361HCID 178418361, compound

Product 1

HCID 156920311,3-Dihydro-2H-pyrrolo[3,2-c]pyridin-2-oneYield 2.2%

Reagents, catalysts & solvents 2

HCID 23938PalladiumCatalystHCID 702EthanolSolvent

Procedure

To a solution of 3,3,7-tribromo-5-azaoxindole (6.4 g, 17.3 mmol) in ethanol (1200 ml) was added 10% Pd on charcoal (3.2 g). The mixture was hydrogenated under 3 atm. hydrogen gas for 3 hours using a Parr shaker. The catalyst was removed by filtration of the mixture through a pad of Celite®, washing well with ethanol. On removal of the solvent, a brown solid remained (predominantly the hydrobromide of the desired product), 3.5 g. This was dissolved in water, treated with activated charcoal and filtered through Celite®. The pH of the filtrate was adjusted to 7.5 by the addition of saturated aqueous NaHCO3 solution. The mixture was then extracted with n-butanol (3×). The combined n-butanol extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo to leave a solid. This was triturated with butanone and filtered to collect 5-azaoxindole as a tan solid (1.6 g, 69%). After removal of butanone, the mother liquor yielded a solid which was recrystallized from methanol to yield more of the title compound (50 mg), m.p.>250° C.

Workup

  1. customThe catalyst was removed by filtration of the mixture through a pad of Celite®
  2. washwashing well with ethanol
  3. customOn removal of the solvent
  4. dissolutionThis was dissolved in water
  5. additiontreated with activated charcoal
  6. filtrationfiltered through Celite®
  7. additionThe pH of the filtrate was adjusted to 7.5 by the addition of saturated aqueous NaHCO3 solution
  8. extractionThe mixture was then extracted with n-butanol (3×)
  9. washThe combined n-butanol extracts were washed with brine
  10. dry with materialdried over magnesium sulfate
  11. concentrationconcentrated in vacuo
  12. customto leave a solid
  13. customThis was triturated with butanone
  14. filtrationfiltered
  15. customto collect 5-azaoxindole as a tan solid (1.6 g, 69%)
  16. customAfter removal of butanone
  17. customthe mother liquor yielded a solid which
  18. customwas recrystallized from methanol

Sources & evidence

ORD record
ord-6c1d8e96271d409e9ead646ec2be1cf6
Source dataset
uspto-grants-1998_09
Patent number
US05811432

Reaction notes

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