反应详情

Fuming nitric acid 90% (8.5 mL, 0.19 mol) was added with gentle stirring to concentrated sulfuric acid 98% (125 mL) in a 1 L beaker. After stirring for 10 minutes at room temperature, 2,4-difluorobenzoic acid methyl ester (21.9 g, 0.127 mol) was added dropwise. After the addition, the reaction mixture was allowed to stir gently for 40 minutes at room temperature. The reaction mixture was then poured into ice-H2O (1 L) and stirred for 10 minutes. The mixture was extracted with EtOAc. The layers were separated, and the organic layer was washed sequentially with 1N NaCl, saturated NaHCO3, H2O and brine, dried (Na2SO4), filtered and concentrated in vacuo to afford a yellow residue. This residue was washed with 10% EtOAc/hexane, filtered, and dried to yield a pale yellow solid, 29.0 g (0.133 mol, 82%). mp 78-80° C. Analysis for C8H5F2NO4: Calcd: C, 44.25; H, 2.32; N, 6.45. Found: C, 44.18; H, 2.39; N, 6.14.

1. additionwas added
2. additionAfter the addition
3. stirringto stir gently for 40 minutes at room temperature
4. stirringstirred for 10 minutes
5. extractionThe mixture was extracted with EtOAc
6. customThe layers were separated
7. washthe organic layer was washed sequentially with 1N NaCl, saturated NaHCO3, H2O and brine
8. dry with materialdried (Na2SO4)
9. filtrationfiltered
10. concentrationconcentrated in vacuo
11. customto afford a yellow residue
12. washThis residue was washed with 10% EtOAc/hexane
13. filtrationfiltered
14. customdried
15. customto yield a pale yellow solid, 29.0 g (0.133 mol, 82%)