反应详情

温度

50 °C

6-Trifluoromethyl-pyridine-2,4-diol (56 gm, 310 mmol) was added in 3-5 gm portions to conc. sulphuric acid (140 mL) with stirring to give a pale brown solution. The temperature increased to ˜50° C. during the addition. Nitric acid (21.1 mL 328 mmol, 70% HNO3 d=1.4 gm/ml) was added drop wise at such a rate as to maintain a reaction temperature of between 45° and 50° C. which took approximately 90 minutes. Once all the nitric acid had been added the reaction was allowed to cool to ambient temperature over 3 hours. The reaction mixture was then poured into ice/water (˜1.3 kg) with stirring, and after a few minutes a pale yellow precipitate formed which was filtered off, dissolved in ethyl acetate and dried over sodium sulphate, filtered and evaporated. A second crop of material was obtained by extraction of the aqueous filtrate with ethyl acetate. Combined batches and purified by crystallization from ethyl acetate/ n-heptane gave the title compound as a white ‘fluffy’ solid (49.5 gm 71% yield).

1. customto give a pale brown solution
2. temperatureto maintain a reaction temperature of between 45° and 50° C. which
3. temperatureto cool to ambient temperature over 3 hours
4. stirringwith stirring
5. customafter a few minutes a pale yellow precipitate formed which
6. filtrationwas filtered off
7. dissolutiondissolved in ethyl acetate
8. dry with materialdried over sodium sulphate
9. filtrationfiltered
10. customevaporated
11. customA second crop of material was obtained by extraction of the aqueous filtrate with ethyl acetate
12. customCombined batches and purified by crystallization from ethyl acetate/ n-heptane