[I:1][C:2]1[CH:3]=[N:4][N:5]([CH3:10])[C:6]=1[C:7]([OH:9])=[O:8].[C:11](Cl)(=O)[C:12](Cl)=O.CCO>C(Cl)Cl.CN(C=O)C>[I:1][C:2]1[CH:3]=[N:4][N:5]([CH3:10])[C:6]=1[C:7]([O:9][CH2:11][CH3:12])=[O:8]4-Iodo-1-methyl-1H-pyrazole-5-carboxylic acid (301.68 g, 1.2 moles) was slurried in 1.2 L of DCM and DMF (2.3 g, 31 mmol) followed by addition of oxalyl chloride (115 mL, 1.3 moles) over 37 minutes and then stirred at room temperature for 3 h. To the resulting solution was added EtOH (750 mL, 12.9 mol) over 5 min followed by stirring at room temperature for 2 h. The crude product solution was concentrated to dryness in vacuo and then reconstituted in 1.2 L of warm heptane followed by filtration. The filtrate was concentrated by removing 500 mL of heptane, resulting in precipitation of solids. The solids were collected via filtration and dried to afford ethyl 4-iodo-1-methyl-1H-pyrazole-5-carboxylate as a white solid (297.6 g, 89% yield).
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