Sodium Hydroxide → 5-fluoro-1-(3-fluorobenzyl)-1H-indole-2-carboxylic acid

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Reaction Steps

Aqueous sodium hydroxide solution, prepared from 1.15 g (28.92 mmol) of sodium hydroxide pellets in 50 mL of water, is added to a solution of 7.6 g (24.10 mmol) of ethyl 5-fluoro-1-(3-fluorobenzyl)-1H-indole-2-carboxylate (WO2006/024776) in 241 mL of ethanol. The mixture is heated for 2 hours and then concentrated under reduced pressure. The resulting solid is taken up in 200 mL of water. The solution is washed with twice 100 mL of ethyl ether, acidified by successive addition of small amounts of concentrated hydrochloric acid and then extracted with 200 mL of ethyl acetate. The organic phase is finally washed twice with 100 mL of water and once with 50 mL of saturated sodium chloride solution, dried over magnesium sulfate and concentrated under reduced pressure. After drying at 50° C. under reduced pressure, 6.4 g of the expected product are obtained in the form of a solid, which is used without further purification in the rest of the synthesis.

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