General procedure for the synthesis of 6-chloropyrazine-2-carboxylic acid from methyl 6-chloropyrazine-2-carboxylate: 6-chloropyrazine-2-carboxylic acid methyl ester (1.78 g, 10.3 mmol) was dissolved in ethanol (25 mL). 1 M sodium hydroxide solution (25 mL) was added and the reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, the mixture was acidified to pH 3 with 1 M aqueous hydrochloric acid solution. subsequently, the reaction mixture was diluted with water (150 mL) and extracted with ethyl acetate (4 × 100 mL). The organic phases were combined, washed with saturated saline (100 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford the title compound 6-chloropyrazine-2-carboxylic acid as a white solid (1.54 g, 94% yield). Mass spectrum (DCI/NH3) m/z 176 (M + NH4)+.
