[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([CH:23]=[O:24])=[C:6]2[C:10]=1[N:9]=[C:8]1[N:11]([C:15]3[CH:20]=[CH:19][C:18]([Cl:21])=[CH:17][C:16]=3[Cl:22])[CH2:12][CH2:13][CH2:14][N:7]21.[C:25]([Mg]Cl)#[CH:26]>O1CCCC1.[Cl-].[NH4+]>[Cl:1][C:2]1[C:10]2[N:9]=[C:8]3[N:11]([C:15]4[CH:20]=[CH:19][C:18]([Cl:21])=[CH:17][C:16]=4[Cl:22])[CH2:12][CH2:13][CH2:14][N:7]3[C:6]=2[C:5]([CH:23]([OH:24])[C:25]#[CH:26])=[CH:4][CH:3]=1To a solution of 9-chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carbaldehyde (100 mg, 0.263 mmol) in tetrahydrofuran (1.5 mL) was added dropwise ethynylmagnesium chloride (0.5 M solution in tetrahydrofuran, 1.05 mL, 0.525 mmol) at 0° C., and the mixture was stirred at 0° C. for 10 min. The reaction mixture was diluted with aqueous saturated ammonium chloride, and extracted with ethyl acetate. The combined organic layer was washed with brine, dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluting with a 20-50% ethyl acetate/n-hexane gradient mixture to give the title compound as a colorless solid (99.3 mg, 0.244 mmol, 93%).
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