Dess-Martin reagent (925 mg, 2.18 mmol) was added to a stirred solution of cyclopropyl[1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]methanol (770 mg, 1.98 mmol) in dichloromethane (8.0 mL) at 0° C., and the mixture was stirred at 0° C. for 90 min. 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 5-50% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the solid, which was recrystallized from ethyl acetate/diisopropyl ether to give the title compound as a colorless crystal (226 mg, 0.585 mmol, 30%).
