Dibutylamine → 7-Ethylindole

HRID 1494160Notes

Reaction equation

HRID 1494160 reaction equation
[CH3:1][C:2]1[CH:7]=[CH:6][CH:5]=[C:4]([CH2:8][CH3:9])[C:3]=1[N:10]=[CH:11]OCC.C(NCCCC)CCC.C([N-]CCCC)CCC.[K+].[NH2-].[K+]>C(O)C>[CH2:8]([C:4]1[CH:5]=[CH:6][CH:7]=[C:2]2[C:3]=1[NH:10][CH:11]=[CH:1]2)[CH3:9]

Participants

6

Reactant 4

HCID 8148DibutylamineHCID 87015Potassium amideHCID 12552076Potassium di-n-butylamideHCID 19829582Ethyl N-(2-methyl-6-ethylphenyl)formimidate2×

Product 1

HCID 27247117-EthylindoleYield 80%

Reagents, catalysts & solvents 1

HCID 702EthanolSolvent

Conditions

Temperature
159 °C

Procedure

Ethyl N-(2-methyl-6-ethylphenyl)formimidate (65.9 g.) in 50 ml. of di-n-butylamine was slowly added, over about 5 minutes, to the potassium di-n-butylamide reaction mixture at 20° C. The metallation and cyclization reactions were substantially instantaneous under these reaction conditions. The transient appearance of a deep red color characteristic of benzyl anion was developed and discharged immediately upon contact of ethyl N-(2-methyl-6-ethylphenyl)formimidate with the potassium amide reaction mixture near the neck of the reactor. All solids dissolved resulting in a light brownish solution. Stirring was continued for another half hour. Then 150 ml. of ethyl alcohol were added to destroy the excess amide and unreacted metal and also to convert potassium indole salt to indole. After the removal of the excess alcohol at reflux temperature (159° C.) through a distillating column packed with Fenske packing materials, a brown oily material separated and settled at the bottom of the flask. The top amine layer was decanted off. The brown oily layer was dissolved in 300 ml. of hexane, then washed with 500 ml. water which was extracted with two 300 ml. portions of hexane. The combined hexane extracts were dried over Na2SO4 and filtered. Evaporation of volatile components furnished 39.8 g. of 7-ethylindole (80.0 percent yield) of over 98.5 percent purity.

Workup

  1. customThe metallation and cyclization reactions were substantially instantaneous under these reaction conditions
  2. dissolutionAll solids dissolved
  3. customresulting in a light brownish solution
  4. customto destroy the excess amide and unreacted metal
  5. customAfter the removal of the excess alcohol
  6. customa brown oily material separated
  7. customThe top amine layer was decanted off
  8. dissolutionThe brown oily layer was dissolved in 300 ml
  9. washof hexane, then washed with 500 ml
  10. extractionwater which was extracted with two 300 ml
  11. dry with materialThe combined hexane extracts were dried over Na2SO4
  12. filtrationfiltered
  13. customEvaporation of volatile components
  14. customfurnished 39.8 g

Sources & evidence

ORD record
ord-2cd40b5929c94bb8a4d9fade5eff568f
Source dataset
uspto-grants-1991_06
Patent number
US05025096

Reaction notes

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