Carbon Dioxide → 3-(4,5,6,7-tetrahydro-1H-indol-3-yl)-propionic acid

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Reaction Steps

Crude 2-ethoxycarbonyl-3-(2-ethoxycarbonylethyl)-4,5,6,7-tetrahydroindole (30 g) and 80 mL of 5 N sodium hydroxide were refluxed for 80 min in a round bottom flask heated in an oil bath and equipped with magnetic stirring. The heater was turned off, but the flask was left in the hot bath, and about 44 mL of 10 N hydrochloric acid was cautiously added via a dropping funnel through the reflux condenser with vigorous stirring. When approximately 80% of the acid had been added, a large amount of carbon dioxide was evolved. The addition was continued until the pH was 2-3. The mixture was cooled in a water bath, and 200 mL of ethyl acetate was added to dissolve the oil that was present. The ethyl acetate layer was isolated and was washed 3 times with 50 mL of water each time, twice with 30 mL of brine each time, and was dried over 5 g of anhydrous sodium sulfate and was evaporated to give 15.5 g (80%) yield of crude 3-(2-carboxyethyl)-4,5,6,7-tetrahydroindole as a very dark sticky syrup.

Provenance & Evidence