1. 4-Bromo-2-hydroxypyridine (1.0 g, 5.75 mmol) was dissolved in tetrahydrofuran (20 mL).
2. The reaction mixture was cooled to 0 °C under nitrogen atmosphere.
3. sodium hydride (60% dispersed in mineral oil, 0.23 g, 5.75 mmol) was added slowly.
4. Gradually warm the mixture to room temperature and stir for 15 minutes.
5. Add iodomethane (1.10 mL, 17.24 mmol) dropwise.
6. Continue stirring the reaction mixture for 16 hours at room temperature.
7. Monitor the progress of the reaction by thin layer chromatography (TLC) to confirm the completion of the reaction. 8.
8. Upon completion of the reaction, water and ethyl acetate were added for extraction. 9.
9. The organic and aqueous phases were separated.
10. The organic phase is washed with saturated sodium chloride solution and dried over anhydrous sodium sulfate.
11. Concentrate the organic phase under pressure to obtain N-methyl-4-bromo-2-hydroxypyridine (1.02 g, 94.4% yield).
[1] Patent: US2017/112833, 2017, A1. Location in patent: Paragraph 0674-0675
[2] Synlett, 2015, vol. 26, # 11, p. 1557 - 1562
[3] Patent: CN105884695, 2016, A. Location in patent: Paragraph 0357; 0358; 0359
[4] Bioorganic and Medicinal Chemistry Letters, 2011, vol. 21, # 23, p. 7076 - 7080