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

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Reaction Steps

0.8 g (2.46 mmol) of (E)-3-[3-(4-fluorophenyl)-1-isopropyl-1H-indol-2-yl]-acrylic acid in 4 ml of THF are introduced into a 50 ml three-necked round-bottomed flask equipped with a magnetic stirrer, thermometer, reflux condenser and nitrogen delivery line. 0.5 g (2.96 mmol) of 1,1-carbonyldiimidazole is then added in portions in the course of 5 min. and stirring is carried out at room temperature for 1 hour. 0.24 g (2.46 mmol) of magnesium chloride and 0.39 g (2.46 mmol) of monomethyl malonate potassium salt are then added and the suspension is stirred for 24 hours at 35° C. The reaction mixture is cooled and filtered and the residue is washed twice with 25 ml of THF. The filtrate is concentrated by evaporation, taken up in 30 ml of ethyl acetate, washed with 15 ml of 1N hydrochloric acid, three times with 20 ml of saturated sodium hydrogen carbonate solution and three times with saturated sodium chloride solution, dried over magnesium sulfate, filtered and concentrated by evaporation. The residue is purified by means of flash chromatography (hexane/ethyl acetate=8:1). An orange resin is obtained which, according to NMR, is the product in a keto-enol equilibrium of approximately 3:1.

Provenance & Evidence