To a solution of 9-chloro-1-(2-chloro-4-methoxyphenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carbaldehyde (200 mg, 0.53 mmol) and trimethyl(trifluoromethyl)silane (0.24 mL, 1.62 mmol) in tetrahydrofuran (10 mL) was added tetra(n-butyl)ammonium fluoride in tetrahydrofuran (1.0 M, 0.053 mL, 0.053 mmol) at 0° C. After the mixture was stirred at 0° C. for 0.5 hr, 1N hydrogen chloride (2.0 mL) was added to the reaction mixture. The reaction mixture was stirred at 0° C. for 1 hr. Aqueous sodium hydrogen carbonate was added to the reaction mixture at 0° C. and the mixture was extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous magnesium sulfate and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with a 30-70% ethyl acetate/n-hexane gradient mixture to give the title compound (212 mg, 0.475 mmol, 90%) as pale yellow crystals.
