[C:1]([CH2:3]P(=O)(OCC)OCC)#[N:2].[H-].[Na+].[CH2:14]([N:16]1[CH:24]=[C:23]2[C:18]([CH:19]=[CH:20][CH:21]=[C:22]2[CH:25]=O)=[N:17]1)[CH3:15]>O1CCCC1.[Cl-].[NH4+]>[CH2:14]([N:16]1[CH:24]=[C:23]2[C:18]([CH:19]=[CH:20][CH:21]=[C:22]2/[CH:25]=[CH:3]/[C:1]#[N:2])=[N:17]1)[CH3:15]
To a solution of diethyl cyanomethylphosphonate (254 μL, 1.57 mmol) in tetrahydrofuran (6 mL) was added 60% sodium hydride (57.9 mg, 1.45 mmol) under ice-cooling, and the mixture was stirred at 0° C. for 15 min. To the mixture was added a solution of 2-ethyl-2H-indazole-4-carbaldehyde (210 mg, 1.20 mmol) in tetrahydrofuran (6 mL) under ice-cooling, and the mixture was stirred under ice-cooling for 15 min. The reaction solution was diluted with saturated aqueous ammonium chloride solution, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, and dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate/hexane=15/85→50/50) to give the title compound (222 mg, yield 93%).
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