Diisopropylamine → 4-[2-(3,5-Dichloro-4-pyridyl)-1-oxoethyl]-7-methoxybenzofuran-2-carboxylic acid

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Reaction Conditions

Reaction Steps

N,N-Diisopropylamine (8.5 ml) was dissolved in anhydrous THF (150 ml), n-butyl lithium (a 1.65 mol/l solution in hexane, 32 ml) was dropwise added thereto at −78° C. in an argon atmosphere, and the mixture was stirred for 5 minutes. The mixture was stirred at room temperature for 3 minutes and then cooled again to −78° C., 3,5-dichloropicoline (7.2 g) was added thereto, and the mixture was stirred for 30 minutes, which was dropwise added at −78° C. over 1 hour in an argon atmosphere to a solution in anhydrous THF (500 ml) of ethyl 4-formyl-7-methoxybenzofuran-2-carboxylate (10 g) obtained in step 1 of Reference Example 1. The mixture was stirred at −78° C. for 2.5 hours and returned to room temperature, and the reaction was quenched by adding water. The reaction mixture was diluted with ethyl acetate, which was washed with a saturated aqueous sodium chloride solution and dried over sodium sulfate. The solvent was distilled off under reduced pressure. The resulting residue was suspended in isopropanol and the precipitated crystals were collected by filtration to give the desired compound (14.3 g, 87%) as colorless crystals.

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