反应详情

25 mL of fuming H2SO4 under cold conditions (0° C.) is added dropwise to a stirred solution of 4-hydroxy-2-trifluoromethylpyridine [Chemistry of Heterocyclic Compounds 1997, 33, 995-996] (4 g, 24.5 mmol) in concentrated H2SO4 (10 mL). HNO3 (fuming, 90%, 25 mL) is added carefully to the above mixture with caution to keep the offset of any exotherm under control, and the reaction is allowed to warm to room temperature slowly. After heating at 120° C. for 6 h with stirring, the resulting mixture is cooled to room temperature, poured into ice-cold water maintaining the pH around 1 with the addition of 10N NaOH solution, and then extracted with CHCl3. The combined organic phase is washed successively with saturated aqueous NaHCO3, water, brine, dried over Na2SO4, and concentrated in vacuo to afford 5-nitro-2-trifluoromethyl-pyridin-4-ol as an yellow solid. 1H NMR (300 MHz, CDCl3): δ 9.33 (s, 1H), 7.50 (s, 1H).

1. temperatureAfter heating at 120° C. for 6 h
2. temperaturethe resulting mixture is cooled to room temperature
3. additionpoured into ice-cold water maintaining the pH around 1
4. extractionextracted with CHCl3
5. washThe combined organic phase is washed successively with saturated aqueous NaHCO3, water, brine
6. dry with materialdried over Na2SO4
7. concentrationconcentrated in vacuo