Dry methanol (240 ml) was transferred into a round bottomed Schlenk using a cannula and was cooled to 0°C using an ice/water bath. Thionyl chloride (13 ml, 21.41 g, 0.18 mol, 1.1 eq.) was added via syringe over 10 min under argon. After stirring at 0°C for 15 min, 2-pyrazinecarboxylic acid (20.00 g, 0.16 mol, 1eq.) was added slowly as a solid. The round bottomed Schlenk was then fitted with a condenser and N₂ bubbler and heated to 60°C for 2 h (solution turns light green in colour). After cooling to ambient temperature, a solution of sodium hydrogen carbonate (29 g, 0.35 mol) in water (280 ml) was added slowly (solution turns yellow-orange in colour). The solution was transferred to a round bottomed flask and the methanol (but not the water) was removed using a rotary evaporator with a water bath held at 45°C. The water layer was then extracted using DCM (3 × 100 ml). The combined DCM layers were dried over sodium sulfate, filtered, and the solvent removed to leave a white solid. Mass = 19.06 g, 0.138 mol, 86 %.

Chem. Commun., 2007, 3957-3959 (SI)