反应详情

温度

50 °C

Water (30 mL) is added to a mixture of the above 5-ethyl-6-methoxy-2-methyl-nicotinic acid methyl ester and sodium hydroxide (3 g, 75 mmol) in methanol (150 mL). The reaction mixture is stirred at 50° C. for 36 hr. The reaction mixture is allowed to cool and is acidified to pH 3 with concentrated hydrochloric acid, then the mixture is treated with excess solid sodium hydrogen carbonate. The resulting suspension is concentrated under vacuum and washed with a portion of dichloromethane. The dichloromethane wash is back extracted with three portions of saturated aqueous sodium hydrogen carbonate, and the combined aqueous layers are acidified to pH 3. The resulting mixture is extracted with six portions of dichloromethane, the combined organic extract is dried over magnesium sulfate, filtered and evaporated to give 5-ethyl-6-methoxy-2-methyl-nicotinic acid (3.49 g, 82% yield over 2 steps) as a white solid. MS: m/e=196 (M+H); 1H NMR (CDCl3, δ, ppm): 8.01 (1H, s), 4.00 (3H, s), 3.77 (3H, s), 2.77 (3H, s), 2.58 (2H, q), 1.20 (3H, t).

1. temperatureto cool
2. concentrationThe resulting suspension is concentrated under vacuum
3. washwashed with a portion of dichloromethane
4. washThe dichloromethane wash
5. extractionis back extracted with three portions of saturated aqueous sodium hydrogen carbonate
6. extractionThe resulting mixture is extracted with six portions of dichloromethane
7. extractionthe combined organic extract
8. dry with materialis dried over magnesium sulfate
9. filtrationfiltered
10. customevaporated