Hydrochloric Acid → 3-(1,2,3,6-Tetrahydropyridin-4-yl)-1H-indole

Participants

Reaction Conditions

Reaction Steps

50 ml of aqueous N phosphoric acid and 39.3 g of the hydrochloride of 4-piperidone monohydrate were added under nitrogen with stirring to a solution of 10 g of indole in 200 ml of acetic acid at 95°-100° C. and the mixture was heated at 100° C. for an hour and was then cooled. The mixture was poured into ice containing 350 ml of concentrated ammonium hydroxide and the mixture was extracted with ethyl acetate. The organic extracts were washed with water, aqueous sodium chloride, dried over magnesium sulfate and evaporated to dryness to obtain 14.7 g of raw product. The latter was empasted with 75 ml of methanol under nitrogen and was vacuum filtered. The recovered precipitate was rinsed with methanol and ether to obtain 1.42 g of 3-(1,2,3,6-tetrahydro-4-pyridyl)-1-H-indole melting at 185°-186° C. The mother liquor was evaporated to dryness and the raw product was chromatographed over silica gel. Elution with a 6-3-1 chloroform-methanol-triethylamine mixture yielded 4.55 g of product with an Rf=0.15. The latter was empasted with ether to obtain 4.295 g of 3-(1,2,3,6-tetrahydro-4-pyridyl)-1H-indole for a total yield of 5.715 g of product. The latter was crystallized from hot and cold isopropanol to obtain 3.56 g of 3-(1,2,3,6-tetrahydro-4-pyridyl)-1H-indole melting at 190°-191° C.

Provenance & Evidence