Sulfuric Acid → 1,2,3,4-Tetrahydro-cyclopenta(b)indole

HRID 1836099Notes

Reaction equation

HRID 1836099 reaction equation
S(=O)(=O)(O)O.[C:6]1([NH:12]N)[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1.[C:14]1(=O)[CH2:18][CH2:17][CH2:16][CH2:15]1>O>[CH2:16]1[C:15]2[C:7]3[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=3[NH:12][C:14]=2[CH2:18][CH2:17]1

Participants

5

Reactant 3

HCID 1118Sulfuric AcidHCID 7516PhenylhydrazineHCID 8452Cyclopentanone

Product 1

HCID 2703051,2,3,4-Tetrahydro-cyclopenta(b)indoleYield 80.4%

Reagents, catalysts & solvents 1

HCID 962WaterSolvent

Procedure

Concentrated sulfuric acid (˜18 M, 35 mL) was added dropwise to a mixture of phenyl hydrazine (510 mmol, 50 mL) and cyclopentanone (45 mL, 510 mmol) in water (250 mL). The resulting mixture was heated to reflux for 30 min and then allowed to cool to room temperature. The liquid was decanted from the reaction mixture leaving a red, gummy solid. Hexanes (500-600 mL) was added to the flask and the mixture was heated to reflux. The yellow hexane solution was decanted hot from the mixture and placed in the freezer (crystallization begins immediately). More hexanes is added to the flask and the procedure repeated two more times using a total volume of 1500 mL of hexanes. After 1 h in the freezer, the solid was collected from the flasks and dried providing the known indole (410 mmol, 65 g, 80%).

Workup

  1. temperatureThe resulting mixture was heated
  2. temperatureto reflux for 30 min
  3. customThe liquid was decanted from the reaction mixture
  4. customleaving a red, gummy solid
  5. temperaturethe mixture was heated to reflux
  6. customThe yellow hexane solution was decanted hot from the mixture
  7. customcrystallization
  8. additionMore hexanes is added to the flask
  9. customthe solid was collected from the flasks
  10. customdried

Sources & evidence

ORD record
ord-410d82c130a9419d858306c0b6d1abf7
Source dataset
uspto-grants-2004_08
Patent number
US06777407B2

Reaction notes

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