Carbon Dioxide → 3,5-Dichloropyrazine-2-carboxylic acid

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Reaction Steps

To a solution of diisopropylamine (0.78 g) in tetrahydrofuran (40 ml) is dropped a 1.6M solution of n-butyl lithium in hexane (4.82 ml) over a period of 3 minutes under cooling on dry ice in acetone bath. The mixture is stirred on the same bath for 30 minutes and thereto is added 2,6-dichloropyrazine 0.50 g in tetrahydrofuran 5 ml at the same temperature over a period of 15 minutes. After stirring for 1 hour, the mixture is poured into dry ice and stirred at room temperature for 1 hour. The mixture is diluted with 10% hydrochloric acid to be adjusted pH about 2 and extracted with ethyl acetate. The combined organic layer is extracted with an aqueous saturated sodium hydrogen carbonate solution. The water extract is washed with ethyl acetate and made acid with a 10% aqueous hydrochloric acid solution and extracted with ethyl acetate. The combined organic layer is washed with water and an aqueous saturated sodium chloride solution, dried over sodium sulfate and concentrated in vacuo. The residue is titrated with chloroform-hexane (1:1) to give 2-carboxy-3,5-dichloropyrazine 234 mg as a slightly brownish crystalline powder. mp 139-141° C., MS(m/z): 191 (M−H)−

Provenance & Evidence