[CH2:1]([N:3]1[CH:7]=[C:6]([CH:8]=[O:9])[C:5]([CH3:10])=[N:4]1)[CH3:2].C(=O)([O-])[O-].[K+].[K+].[Cl:17][C:18]1[N:23]=C(Cl)C=[CH:20][N:19]=1>CN(C)C=O.C(OCC)(=O)C>[Cl:17][C:18]1[N:23]=[C:1]([N:3]2[CH:7]=[C:6]([CH:8]=[O:9])[C:5]([CH3:10])=[N:4]2)[CH:2]=[CH:20][N:19]=1To a solution of ethyl 3-methyl-1H-pyrazole-4-carbaldehyde (6.4 g, 58.0 mmol) in 60 mL of anhydrous N,N-dimethylformamide were added potassium carbonate (10.8 g, 77.8 mmol) and 2,4-dichloropyrimidine (8.64 g, 58.0 mmol) at room temperature. The resulting suspension was stirred for 14 hours at room temperature with monitoring a reaction with LC-MS or thin layer chromatography (TLC). The reaction mixture was diluted with ethyl acetate and washed with brine (×2). The collected organic layer was dried over anhydrous sodium sulfate and then concentrated in vacuo. The resulting residue was purified by silica gel chromatography using a mixture of heptanes and ethyl acetate to afford the desired intermediate 2 as a white solid (5.47 g, 42%); MS (ESI) m/z 223 [M+H]+, 1H NMR (300 MHz, CDCl3) δ 10.06 (s, 1H), 9.04 (s, 1H), 8.70 (d, 1H, J=5.4 Hz), 7.87 (1H, d, J=5.4 Hz), 2.59 (s, 3H).
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