Sulfuric Acid → 5-(Methoxycarbonyl)-1-Methyl-1H-Pyrazole-3-Carboxylic Acid

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Reaction Steps

1-Methyl-1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (640, 3.7 g, 19.0 mmol) was combined with 1,4-dioxane (20 mL) and water (60 mL). Concentrated sulfuric acid (1.0 mL) in 2 mL of water was added to the solution. After the reaction was stirred at reflux overnight, it was cooled to room temperature and concentrated until precipitation began. The obtained mixture was left standing overnight. The resulting solid was filtered and dried under reduced pressure. The collected aqueous fractions were extracted with ethyl acetate. The organic portion was dried over anhydrous sodium sulfate and concentrated. Additional solid was crystallized from ethyl acetate to give the desired compound (641, 2.33 g, 68%). MS (ESI) [M+H+]+=185.0, melting point 175° C.

Provenance & Evidence