[CH3:1][C:2]1[CH:6]=[C:5]([CH3:7])[NH:4][N:3]=1.[H-].[Na+].[Cl:10][C:11]1[CH:16]=[C:15]([Cl:17])[N:14]=[C:13](S(C)(=O)=O)[N:12]=1>ClCCl>[Cl:10][C:11]1[CH:16]=[C:15]([Cl:17])[N:14]=[C:13]([N:3]2[C:2]([CH3:1])=[CH:6][C:5]([CH3:7])=[N:4]2)[N:12]=1A suspension of 3,5-dimethylpyrazole (3.9 g, 40.7 mmol) and sodium hydride (60% in mineral oil, 1.7 g) in dichloromethane (50 mL) was added dropwise to a cooled (−78° C.) solution of 4,6-dichloro-2-methanesulfonyl-pyrimidine (10 g, 38.7 mmol) in dichloromethane (200 mL). The mixture was stirred at −78° C. for one hour. The reaction was carefully quenched at the same temperature by addition of water (150 mL). The mixture was allowed to warm to room-temperature. Brine (150 mL) was added and the phases were separated. The aqueous phase was extracted with dichloromethane (4×200 mL). The combined organic layers were washed with brine, dried over sodium sulphate, filtrated and concentrated in vacuo. The crude product was purified by flash chromatography (ethyl acetate/heptane as eluent) to give 4,6-dichloro-2-(3,5-dimethyl-pyrazol-1-yl)-pyrimidine (5.5 g, 59%) as a white crystalline compound.
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