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

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Reaction Steps

An 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 two hours and then concentrated under reduced pressure. The resulting solid is taken up in 200 ml of water. The solution is washed with two times 100 ml of ethyl ether, acidified by successive additions of small amounts of concentrated hydrochloric acid and then extracted with 200 ml of ethyl acetate. The organic phase is finally washed with twice 100 ml of water, once with 50 ml of saturated sodium chloride solution, and dried over magnesium sulfate and concentrated under reduced pressure. This gives, after drying at 50° C. under reduced pressure, 6.4 g of the expected product, in the form of a solid which will be used as it is in the remainder of the synthesis.

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