Ammonia → 3-[9-Chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]pentanamide

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Reaction Steps

A solution of ethyl 3-[9-chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]pentanoate (173 mg, 0.360 mmol) and aqueous sodium hydroxide (8 M, 0.09 mL) in tetrahydrofuran (1.8 mL) was stirred for 24 h at reflux. The reaction mixture was concentrated in vacuo. To the residue was added tetrahydrofuran (3.0 mL) and ethyl chloroformate (74.3 μL, 0.780 mmol) at 0° C. After being stirred for 1.5 h at room temperature, the reaction mixture was cooled down to 0° C. And then aqueous ammonia solution (28%, 150 μL) was added. After 2 h, the reaction mixture was diluted with ethyl acetate, washed with brine, dried over sodium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash column chromatography on NH silica gel eluting with ethyl acetate to give the title compound as a colorless solid (60.1 mg, 0.133 mmol, 37%).

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