Reaction #5695

Reaction equation

indole

allyl bromide

18-crown-6

potassium tert-butoxide

→

1-allylindole

Yield 74.0%

Solvents

Water

ether

ether

Conditions

Workup

1. 1
   workup.ADDITIONwas added
2. 2
   workup.DISSOLUTIONAll of the solid did not dissolve
3. 3
   workup.WAITThe stirring was continued for 67.5 hours
4. 4
   OtherThe layers were separated
5. 5
   ExtractionThe aqueous layer was extracted with ether (2×75 ml)
6. 6
   WashThe combined ether phases were washed with 50 ml of brine
7. 7
   Dryingdried over MgSO4
8. 8
   OtherEvaporation of the solvent
9. 9
   workup.WAITleft 16.02 g of brown oil
10. 10
    OtherThe oil was chromatographed on a 1100 g column of silica gel
11. 11
    WashThe column was eluted with 10% acetone-Skellysolve B and 2200 ml fractions
12. 12
    Otherwere collected

Procedure

To a solution of 2.39 g (9.04 mmoles) of 18-crown-6 in 250 ml of dry ether was added 13.1 g (116.7 mmoles) of potassium tert-butoxide. The mixture was stirred while 11.72 g (100 mmoles) indole was added. The stirring was continued for 3 hours. All of the solid did not dissolve. Then 14.1 g (116.5 mmoles) of allyl bromide in 100 ml of ether was added during 0.5 hour. The stirring was continued for 67.5 hours. Water (200 ml) was added. The layers were separated. The aqueous layer was extracted with ether (2×75 ml). The combined ether phases were washed with 50 ml of brine and dried over MgSO4. Evaporation of the solvent left 16.02 g of brown oil. The oil was chromatographed on a 1100 g column of silica gel. The column was eluted with 10% acetone-Skellysolve B and 2200 ml fractions were collected. The fractions were assayed by silica gel tlc (1×4") (10% acetone-Skellysolve B). Fractions 17-23 were combined giving 11.60 g (74%) of 1-allylindole as a yellow brown oil.

Source