Tetra-n-butylammonium fluoride (1.0 M solution in tetrahydrofuran, 1.3 mL, 1.3 mmol) was added dropwise to a stirred solution of 1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carbaldehyde (1.50 g, 4.33 mmol) and trimethyl(trifluoromethyl)silane (1.83 g, 12.9 mmol) in tetrahydrofuran (11 mL) at 0° C., and the mixture was stirred at room temperature for 10 hr. The mixture was diluted with 1N hydrochloric acid 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 title compound as a colorless solid (1.19 g, 2.86 mmol, 66%).
