Acetic Anhydride → 1-[9-Chloro-1-(6-methoxy-4-methylpyridin-3-yl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]propyl acetate

Acetic anhydride (103 μL, 1.09 mmol) was added to a stirred solution of 1-[9-chloro-1-(6-methoxy-4-methylpyridin-3-yl)-1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazol-6-yl]propan-1-ol (140 mg, 0.362 mmol) in pyridine (1.2 mL) at room temperature, and the mixture was stirred at room temperature for 19 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 10-50% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the title compound as a colorless amorphous (89.9 mg, 0.210 mmol, 58%). Amorphous.