Process for preparation of substituted pyrazole derivatives
A technology of pyrazole and mixture, applied in the field of preparing substituted pyrazole derivatives, can solve problems such as high reaction temperature, influence on industrial-scale synthesis of compound of formula I, low yield and the like
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[0146] The present invention will be more fully understood by reference to the following examples. However, the claims should not be construed as limiting the scope of the examples.
[0147] If not stated otherwise, all reactions were performed under a protective atmosphere such as argon or nitrogen.
example 1
[0149] 5-Ethyl-4-methyl-1H-pyrazole-3-carboxylic acid (1)
[0150] 3-Pentanone (93.0 g, 1.08 mol, 1.20 eq) was added to diethyl oxalate (132 g, 903 mmol, 1.00 eq) in 20% sodium ethoxide ethanol solution (338 g, 994 mmol, 1.10 eq) and kept precooled ( -5°C-0°C) solution. The line was flushed with ethanol (50 mL). After stirring at this temperature for 2 h, the reaction mixture was cooled to about -15 °C and a cold solution of 40% aqueous hydrazine (118 g, 948 mmol, 1.05 eq) in acetic acid (59.7 g, 994 mmol, 1.10 eq) was added dropwise over 2 h ( About 0 ℃) solution, ensure that the reaction temperature does not exceed 0 ℃. Stirring was continued for 1 h. Keeping the internal temperature between 0 and 15°C, a 50% aqueous solution of sodium hydroxide (205 g, 2.57 mol, 2.85 equiv) was added. The solution was stirred at 20°C±5°C for 2h, then at 40°C±5°C for 16h, forming a clear solution. Concentrated (37%) aqueous hydrochloric acid (350 mL, 3.68 mol, 4.07 equiv) was added at 4...
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