Sodium Chloride → (E)-5-[3-(4-fluorophenyl)-1-isopropyl-1H-indol-2-yl]-3-oxopent-4-enoic acid methyl ester

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Reaction Steps

In a 2 liter round-bottomed flask equipped with a magnetic stirrer and nitrogen delivery line, 30.5 g of crude 5-[3-(4-fluorophenyl)-1-isopropyl-1H-indol-2-yl]-3-methylhex-2-enoic acid methyl ester are dissolved in 250 ml of THF, 13.49 g (133.3 mmol) of triethylamine are added and the yellow solution is heated under reflux for 2 hours. The reaction mixture is then cooled to room temperature, 53 ml (212 mmol) of 4N ammonium hydroxide solution are added and the mixture is stirred vigorously for 3 hours. The reaction mixture is then poured into 1 liter of saturated sodium chloride solution and extracted three times with 250 ml of ethyl acetate. The combined organic phases are washed once with 100 ml of 1N hydrochloric acid and three times with saturated sodium chloride solution, dried over magnesium sulfate, filtered and concentrated by evaporation. The crude product (22.78 g of an orange resin) is purified by means of flash chromatography (hexane/ethyl acetate=9:1). A resin is obtained which, according to NMR, is the product in a keto-enol equilibrium of approximately 3:1.

Provenance & Evidence