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

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To a suspension of 1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carboxylic acid (430 mg, 1.18 mmol) in N,N-dimethylformamide (8.0 mL) were added 1-hydroxy-1H-benzotriazole (235 mg, 1.53 mmol), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (249 mg, 1.30 mmol), and methylamine (2.0 M solution in tetrahydrofuran, 1.20 mL, 2.40 mmol). The mixture was stirred at room temperature for 15 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 40-85% 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 (305 mg, 0.783 mmol, 66%).

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