To a 50 mL round bottom flask was added 6-hydroxypyridine-2-carboxylic acid (500 mg, 3.59 mmol) suspended in a solvent mixture of methanol (5 mL) and water (0.8 mL). Subsequently, potassium hydroxide (400 mg, 7.13 mmol) was added to the suspension and the resulting mixture was stirred at 100 °C for 15 min. After the reaction solution was cooled to room temperature, iodomethane (2.6 mL, 41.8 mmol) was added and the mixture was continued to be stirred at 100 °C for 1 hour. Upon completion of the reaction, the solution was concentrated to half of the original volume under reduced pressure. To the concentrated reaction solution was added 3N hydrochloric acid and the resulting solid product was collected by filtration. The solid was washed sequentially with water and acetonitrile and then dried under reduced pressure to afford 1,6-dihydro-1-methyl-6-oxo-2-pyridinecarboxylic acid (339 mg, 62% yield) as a white powder.1H NMR (DMSO-d6, 400 MHz): δ 7.45 (dd, 1H, J = 9.2, 6.9 Hz), 6.72 (dd, 1H, J = 6.9, 1.4 Hz), 6.59 (dd, 1H, J = 9.2, 1.4 Hz), 3.51 (s, 3H).
