Example 68. General procedure for the synthesis of methyl 6-methoxy-2-pyrazinecarboxylate from 6-oxo-1,6-dihydropyrazine-2-carboxylic acid: 4 mL (0.030 mol) of trimethylsilyl chloride was added to 0.42 g (0.003 mol) of 6-hydroxypyrazine-2-carboxylic acid suspended in 10 mL of anhydrous methanol. The reaction mixture was stirred at room temperature for 48 h. A gradual transformation of the suspension into a clarified solution was observed. This method is suitable for the conversion of 6-hydroxypyrazine-2-carboxylic acid to the corresponding 6-alkoxypyrazine-2-carboxylic acid ester by selecting a suitable alcohol; if the alcohol used is non-liquid, an inert solvent, such as tetrahydrofuran (THF), can be used as the reaction medium. After completion of the reaction, the solvent and excess trimethylchlorosilane were removed by rotary evaporator under reduced pressure. The crude product was purified by silica gel column chromatography with gradient elution of hexane-ethyl acetate to give 0.11 g (22% yield) of the target product, methyl 6-methoxypyrazine-2-carboxylate.
