反应详情

温度

0 °C

To a solution of 4-nitro-1H-pyrazole-3-carboxylic acid methyl ester (3.1 g, 18.1 mmol) in dry acetone (2 ml) was added K2CO3 (5 g, 36.2 mmol) at 25° C. The reaction mixture was cooled to 0° C., and methyl iodide (2.2 ml, 36.3 mmol) was added. The temperature was again raised to 25° C., and then heated to 70° C. for 2 hrs. The solvent was removed in vacuo The residue was diluted with EtOA and washed with water and with brine, dried (Na2SO4), filtered, and concentrated. The crude product was purified by column chromatography over silica gel. Elution with 20% EtOAc/hexane) gave the undesired isomer 2-methyl-4-nitro-2H-pyrazole-3-carboxylic acid methyl ester (1 g, 30%), subsequent elution with 40% EtOAc/hexane provided the desired isomer 1-methyl-4-nitro-1H-pyrazole-3-carboxylic acid methyl ester (1.8 g, 54%).

1. temperatureThe temperature was again raised to 25° C.
2. temperatureheated to 70° C. for 2 hrs
3. customThe solvent was removed in vacuo The residue
4. additionwas diluted with EtOA
5. washwashed with water and with brine
6. dry with materialdried (Na2SO4)
7. filtrationfiltered
8. concentrationconcentrated
9. customThe crude product was purified by column chromatography over silica gel
10. washElution with 20% EtOAc/hexane)
11. customgave
12. washthe undesired isomer 2-methyl-4-nitro-2H-pyrazole-3-carboxylic acid methyl ester (1 g, 30%), subsequent elution with 40% EtOAc/hexane