[CH3:1][C:2]1[NH:6][N:5]=[C:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH:3]=1.C1C(=O)N([I:19])C(=O)C1>CN(C)C=O.O>[I:19][C:3]1[C:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])=[N:5][NH:6][C:2]=1[CH3:1]To a solution of ethyl 5-methyl-1H-pyrazole-3-carboxylate (2 g, 12.97 mmol, 1.00 equiv) in N,N-dimethylformamide (50 mL) was added NIS (3.5 g, 15.56 mmol, 1.20 equiv) in portions. The reaction mixture was stirred at 25° C. for 4 h and then diluted with 30 mL of H2O. The resulting mixture was extracted with 2×30 mL of ethyl acetate. The combined organic layers were washed with 2×50 mL of brine, dried over anhydrous sodium sulfate and concentrated under vacuum. The residue was purified on a silica gel column eluted with 0-50% of ethyl acetate in petroleum ether to give 3.6 g (99%) of ethyl 4-iodo-5-methyl-1H-pyrazole-3-carboxylate as a white solid. LCMS (method D, ESI): RT=1.27 min, m/z=281.0 [M+H]+.
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