S(Cl)(Cl)=O.O[N:6]=[CH:7][C:8]1[N:12]([C:13]([CH3:16])([CH3:15])[CH3:14])[N:11]=[CH:10][C:9]=1[C:17]([O:19][CH2:20][CH3:21])=[O:18].O>CCOCC>[C:7]([C:8]1[N:12]([C:13]([CH3:15])([CH3:16])[CH3:14])[N:11]=[CH:10][C:9]=1[C:17]([O:19][CH2:20][CH3:21])=[O:18])#[N:6]Thionyl chloride (6.6 ml, 0.092 mole) was added to a cold solution of 5-(hydroxyiminomethyl)-1-tert-butyl-1H-pyrazole-4-carboxylic acid, ethyl ester (11 grams, 0.046 mole) in 75 ml of ether. The solution was stirred in the cold for thirty minutes, then at room temperature for 16 hours. Water was added to the reaction mixture to neutralize the remaining thionyl chloride, then the reaction mixture was poured into a separatory funnel. The phases were separated and the organic phase was washed with water and dried using sodium sulfate and filter paper. The solvent was removed in vacuo, yielding 8.5 grams of 5-cyano-1-tert-butyl-1H-pyrazole-4-carboxylic acid, ethyl ester.
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