Ethylamine → 1-(2,4-Dichlorophenyl)-N,N-diethyl-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carboxamide

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A mixture of 1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carboxylic acid (350 mg, 0.966 mmol), 1-hydroxy-1H-benzotriazole (193 mg, 1.26 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (203 mg, 1.06 mmol), and ethylamine (141 mg, 1.93 mmol), and N,N-dimethylformamide (7.0 mL) was stirred at room temperature for 3 hr. The mixture was diluted with saturated aqueous sodium hydrogen carbonate, and extracted with ethyl acetate. The combined organic layer was washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluting with a 20-60% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the solid, which was recrystallized from ethanol/ethyl acetate to give the title compound as a colorless crystal (276 mg, 0.661 mmol, 68%).

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