The general procedure for the synthesis of 2-hydroxy-4-methylpyridine from 2-amino-4-methylpyridine was as follows: the synthesis of intermediate V-a (4-methylpyridin-2-ol) was carried out with reference to the method reported by Adger et al. in J. Chem. Soc. Perkin Trans. 1, 1988, p2791-2796. Concentrated HCl was added to a 1 L flask containing water (240 mL) and subsequently cooled to 0°C. 2-Amino-4-methylpyridine (30 g, 277 mmol) was added all at once, followed by a dropwise addition of a solution of NaNO2 (20.6 g, 299 mmol) in water (40 mL) over a period of 1 h, ensuring that the internal temperature did not exceed 5 °C. The reaction was carried out at 0 °C by stirring the reaction mixture. The reaction mixture was stirred at 0 °C for 1 h and then heated to 95 °C, held for 15 min and subsequently cooled to room temperature. The pH was adjusted to 6-7 with 50% NaOH aqueous solution (note exothermic) and extracted with EtOAc (4 x 120 mL) while hot. The organic phases were combined, dried with MgSO4, filtered and the solvent evaporated to give a beige crystalline solid intermediate V-a (24.5 g, 81% yield).1H NMR (300 MHz, DMSO-d6) δ 11.31 (s, 1H), 7.23 (d, J = 6.7 Hz, 1H), 6.10 (s, 1H), 6.00 (dd, J = 6.7, 1.2 Hz, 1H). 1.2 Hz, 1H), 2.10 (s, 3H).
