General procedure for the synthesis of methyl 3-chloro-2-pyrazinecarboxylate from methanol and 2-chloropyrazine-3-carboxylic acid: 3-chloropyrazine-2-carboxylic acid (100 mg, 0.63 mmol) was dissolved in a solvent mixture (2 mL : 2 mL) of dichloromethane (DCM) and methanol (MeOH) at room temperature. To this solution was added trimethylsilyl diazomethane (TMSCHN2, 0.47 mL, 0.95 mmol). The reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of acetic acid (0.2 mL) and the reaction mixture was diluted with distilled water (2 mL). Subsequently, the aqueous phase was extracted with dichloromethane (4 mL × 3). The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford methyl 3-chloro-2-pyrazinecarboxylate (100 mg) as a colorless oil. Analyzed by liquid chromatography-mass spectrometry (LRMS), the molecular ion peak m/z (M + H) was measured to be 173.0, which was consistent with the theoretical value of 173.0.
