反应详情

237 g of 3-(2,4-dichlorophenyl)-5-hydroxy-1H-pyrazol from Example 3.1 were initially charged in 2160 ml of dioxane. A solution of 84 g of sodium hydroxide in 250 ml of water was added, and the mixture was heated at reflux. With stirring, 620 g (7.17 mol, 6.9 eq.) of gaseous chlorodifluoromethane were introduced, and, during the addition, the pH was monitored continuously and when it approached the neutral range (pH 9) increased to pH 12 by addition of additional NaOH solution. After 6 h, the mixture was allowed to cool, 1.7 l of water were added and the mixture was extracted three times with in each case 500 ml of MTBE. The combined organic phases were washed with in each case 1500 ml of water and saturated sodium chloride solution, dried over Na2SO4, filtered and concentrated. The residue was suspended in 500 ml of cyclohexane and heated to reflux, and undissolved particles were filtered off. The residue was once more extracted with 200 ml of boiling cyclohexane. The combined filtrates were concentrated to obtain the title compound. This gave 136.7 g of 3-(2,4-dichlorophenyl)-5-difluoromethoxy-1H-pyrazole as a solid. (Yield 47.3%).

1. temperaturethe mixture was heated
2. temperatureat reflux
3. additionduring the addition
4. temperatureto cool
5. extractionthe mixture was extracted three times with in each case 500 ml of MTBE
6. washThe combined organic phases were washed with in each case 1500 ml of water and saturated sodium chloride solution
7. dry with materialdried over Na2SO4
8. filtrationfiltered
9. concentrationconcentrated
10. temperatureheated
11. temperatureto reflux
12. filtrationundissolved particles were filtered off
13. extractionThe residue was once more extracted with 200 ml of boiling cyclohexane
14. concentrationThe combined filtrates were concentrated