Sodium hydride (60% in oil, 230 mg, 5.76 mmol) was added to a stirred solution of ethyl (diethoxyphosphoryl)acetate (1.94 g, 8.67 mmol) in tetrahydrofuran (14 mL) at 0° C. After stirring 10 min, 1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carbaldehyde (1.00 g, 2.88 mmol) in tetrahydrofuran (1.0 mL) was added to the mixture, and the mixture was stirred at room temperature for 12 hr. The mixture was diluted with water, 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 10-50% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the solid, which was washed with diisopropyl ether to give the title compound as a colorless powder (908 mg, 2.18 mmol, 76%).
