Dess-Martin reagent (1.27 g, 3.00 mmol) was added to a stirred suspension of 1-[9-chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]propan-1-ol (1.12 g, 2.73 mmol) in acetonitrile (23 mL) at 0° C., and the mixture was stirred at room temperature for 1 hr. The mixture was diluted with saturated aqueous sodium hydrogen carbonate, concentrated in vacuo, and extracted with ethyl acetate/tetrahydrofuran. 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 15-50% 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 (980 mg, 2.40 mmol, 88%).
