Dimethylformamide → 9-Chloro-6-(1-chloro-2,2,2-trifluoroethyl)-1-(2,4,6-trichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole

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A mixture of 1-[9-chloro-1-(2,4,6-trichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]-2,2,2-trifluoroethanol (325 mg, 0.670 mmol), thionyl chloride (0.0978 mL, 1.34 mmol) and catalytic amount of dimethylformamide in tetrahydrofuran (6.7 mL) was stirred at room temperature for 2 h. The mixture was quenched with aqueous saturated sodium hydrogen carbonate and extracted with ethyl acetate. The combined organic layer was washed with brine, dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluting with a 10-30% ethyl acetate/n-hexane gradient mixture to give the title compound as a colorless solid (297 mg, 0.590 mmol, 88%).

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