Dimethyl Sulfoxide → 9-Chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazole-6-carbaldehyde

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Reaction Steps

Sulfur trioxide-pyridine complex (24.1 g, 152 mmol) was added to a stirred solution of [9-chloro-1-(2,4-dichlorophenyl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]methanol (8.30 g, 21.7 mmol), triethylamine (24 mL), and dimethyl sulfoxide (150 mL) in dichloromethane (100 mL) at room temperature, and the mixture was stirred at room temperature for 3 hr. The mixture was concentrated in vacuo, 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 15-50% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the solid, which was washed with ethyl acetate/diisopropyl ether to give the title compound as a pale yellow powder (6.82 g, 17.9 mmol, 82%).

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