1H-Pyrazole-5-carboxylic acid, 3-(1,1-dimethylethyl)-1-methyl-4-nitro- synthesis

Yield:1004455-73-5 72%

Reaction Conditions:

with sulfuric acid;sulfur trioxide;nitric acid at 0 - 60; for 4 h;

Steps:

2.E

Oleum (816 mmol) is slowly added to fuming nitric acid (890 mmol) at 0⁰C followed by the addition of 5-ter?-butyl-2-methyl-2H-pyrazole-3-carboxylic acid (148 mmol) in small portions. After addition, the reaction mixture is stirred at 60⁰C for 4h. On completion, the reaction mixture is cooled to room temperature and poured into crushed ice. The aqueous phase is then extracted with ethyl acetate (250 mL x 3). The combined organic phases are washed with water (200 mL x 2) and dried over anhydrous sodium sulfate. The solvent is removed under reduced pressure to afford 5-tert-butyl-2-methyl- 4-nitro-2H-pyrazole-3-carboxylic acid as light yellow solid (24.2g, 72%). [0213] ¹H NMR (400 MHz, DMSO-^₆) δ: 3.96 (s, 3H), 1.29 (s, 9H). Mass (m/z): 228 (M+H).

References:

WO2009/71706,2009,A1 Location in patent:Page/Page column 43-44