2-Methylindole → Indole

HRID 530176Notes

Reaction equation

HRID 530176 reaction equation
C([Al](CC)CC)C.[Cl-].C([Al+]CC)C.[NH:14]1[CH:18]=[CH:17][CH:16]=[CH:15]1.CC1C=CC(O)=C(C)C=1.C[C:29]1[NH:30][C:31]2[C:36]([CH:37]=1)=[CH:35][CH:34]=[CH:33][CH:32]=2>>[NH:30]1[C:31]2[C:36](=[CH:35][CH:34]=[CH:33][CH:32]=2)[CH:37]=[CH:29]1.[NH:14]1[CH:18]=[CH:17][CH:16]=[CH:15]1

Participants

7

Reactant 5

HCID 72242-MethylindoleHCID 77712,4-DimethylphenolHCID 8027Pyrrole2×HCID 16682930Triethylaluminum2×HCID 16686102Diethyl aluminum chloride2×

Product 2

HCID 798IndoleHCID 8027Pyrrole

Procedure

A catalyst solution was prepared using the standard procedure described here, in which the molar ratios of TEA (triethylaluminum) to DEAC (diethylaluminum chloride) to pyrrole compound to Cr were standardized to TEA:DEAC:pyrrole:Cr=11:8:3:1. Anhydrous, degassed ethylbenzene was added to a dry vial in a drybox. To this vial was added neat triethylaluminum (TEA) and neat diethylaluminum chloride (DEAC). The contents were mixed and allowed to stand for 15 minutes. The selected pyrrole was then slowly added, as gas evolution was observed in most cases. Chromium(III) 2-ethylhexanoate (7.25 wt % Cr in ethylbenzene) was used as the transition metal compound and was added slowly to the alkylaluminum/pyrrole solution with stirring. The catalyst solution was diluted to a concentration of 5.6 mg Cr/mL by adding an appropriate amount of ethylbenzene to constitute the active catalyst what was used as prepared. Orange colored solutions were observed for 2,4-DMP, 2-methylindole, and 2,5-DEP based catalyst, which are typical. 2,5-DBP initially produced an orange solution, but gradually precipitated a noticeable amount of grey solid over the course of 24 h. Both indole and pyrrole produced an orange solution with a white, fluffy solid which was removed by filtration. 2,5-DIP produced copious amounts of black precipitate suggesting that the catalyst solution was fairly unstable

Workup

  1. customA catalyst solution was prepared
  2. customAnhydrous, degassed ethylbenzene
  3. additionwas added to a dry vial in a drybox
  4. additionTo this vial was added neat triethylaluminum (TEA) and neat diethylaluminum chloride (DEAC)
  5. additionThe contents were mixed
  6. additionThe selected pyrrole was then slowly added, as gas evolution
  7. additionwas added slowly to the alkylaluminum/pyrrole solution
  8. additionThe catalyst solution was diluted to a concentration of 5.6 mg Cr/mL
  9. additionby adding an appropriate amount of ethylbenzene
  10. customas prepared
  11. custom2,5-DBP initially produced an orange solution
  12. customgradually precipitated a noticeable amount of grey solid over the course of 24 h

Sources & evidence

ORD record
ord-3b5f99bf2aec4cbe9e60b2459ed81fbd
Source dataset
uspto-grants-2016_05
Patent number
US09352309B2

Reaction notes

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