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ChemicalBook CAS DataBase List ETHYL-3-ETHYLPYRAZOLE-4-CARBOXYLATE
73981-23-4

ETHYL-3-ETHYLPYRAZOLE-4-CARBOXYLATE synthesis

1synthesis methods
Pentanoic acid, 2-[(dimethylamino)methylene]-3-oxo-, ethyl ester

89193-23-7

ETHYL-3-ETHYLPYRAZOLE-4-CARBOXYLATE

73981-23-4

Ethyl 2-((dimethylamino)methylene)-3-oxovalerate (13.9 mmol, 2.76 g) was used as a raw material and reacted with hydrazine (13.9 mmol, 0.44 mL) in ethanol (50 mL) with stirring for 1 h at room temperature. After completion of the reaction, the solvent was removed by evaporation to obtain the crude product. The crude product was purified by rapid chromatography on silica gel using cyclohexane/ethyl acetate (80:20) as eluent. After purification, the eluent was evaporated to afford ethyl 3-ethyl-1H-pyrazole-4-carboxylate (6.00 mmol, 1.01 g, 43% yield) as a yellow oil. The product was analyzed by liquid chromatography (Zorbax SB-C18, 3.5 μm, 4.6 × 50 mm column): retention time (RT) = 1.53 min; mass spectrum (MS) m/z ES+ = 169.

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Yield:73981-23-4 43%

Reaction Conditions:

with hydrazine in ethanol at 20; for 1 h;

Steps:

12

Ethyl 3-ethyl-lH-pyrazole-4-carboxylateAccording to Scheme 9 Step 2: A solution of ()-ethyl 2-((dimethylamino)methylene)- 3-oxopentanoate (13.9 mmol, 2.76 g) and hydrazine (13.9 mmol, 0.44 mL) in EtOH (50 niL) was stirred for 1 hour at room temperature. After evaporation of the solvent, the resulting crude product was purified by flash chromatography over silica gel using cyclohexane/AcOEt (80:20) as eluent to yield after evaporation ethyl 3-ethyl-lH- pyrazole-4-carboxylate (6.00 mol, 1.01 g, 43%) as a yellow oil. LC (Zorbax SB-Ci8, 3.5μm, 4.6x50mm Column): RT = 1.53 min; MS m/z ES+= 169.

References:

WO2009/10455,2009,A2 Location in patent:Page/Page column 62-63

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