[OH:1][C:2]1[NH:6][N:5]=[C:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH:3]=1.C(=O)([O-])[O-].[K+].[K+].Br[CH2:19][CH2:20]Br>C(#N)C>[O:1]1[CH2:20][CH2:19][N:6]2[N:5]=[C:4]([C:7]([O:9][CH2:10][CH3:11])=[O:8])[CH:3]=[C:2]12To the stirred suspension of ethyl 5-hydroxy-1H-pyrazole-3-carboxylate (10.34 g, 0.66 mol) and 36.62 g of potassium carbonate in 500 ml of acetonitrile was added 13.68 g of 1,2-dibromoethane, and refluxed for 16 hours. The reaction mixture was allowed to cool to room temperature, then filtered, the solid was washed with acetonitrile. The filtrate was concentrated to an oil. The residue was dissolved in ethyl acetate and extracted with water. The organic phase was dried over MgSO4 and evaporated to dryness. 5.80 g of the desired product was obtained (48%).
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