1. add methanol (70 mL) to 5-hydroxypyridine-2-carboxylic acid (5.01 g, 36.0 mmol).
2. sulfuric acid (5.8 mL, 110 mmol) was added slowly and dropwise to the above mixture.
3. The reaction mixture was stirred overnight at 75 °C. 4.
4. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure. 5.
5. The residue was dissolved in ethyl acetate (EtOAc). 6.
6. Saturated aqueous sodium bicarbonate (NaHCO) is added to the solution and the pH is adjusted to 3. 7.
7. The precipitate was collected by filtration and dried under vacuum. 8.
8. The remaining aqueous phase was extracted with ethyl acetate.
9. The organic phases were combined, washed with saturated brine and dried over anhydrous sodium sulfate (NaSO).
10. The organic phases were concentrated under pressure to give the solid product methyl 5-hydroxy-2-pyridinecarboxylate (5.3 g, 96% yield), which could be used for subsequent reactions without further purification.
11. LCMS analysis: calculated value CHNO([M+H]) m/z = 154.1; measured value: 154.1.
