Potassium Carbonate → Methyl [1-(2,4-dichlorophenyl)-5-(diethylamino)-2,3-dihydro-1H-imidazo[1,2-a]benzimidazol-2-yl]acetate

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Reaction Steps

To a solution of methyl 4-[2-[(2,4-dichlorophenyl)amino]-7-(diethylamino)-1H-benzimidazol-1-yl]-3-hydroxybutanoate (Reference Example 83; 200 mg, 0.430 mmol) in pyridine (4 mL) was added methanesulfonyl chloride (0.166 mL, 2.14 mmol) at 0° C. After the resultant mixture was stirred at room temperature for 16 hr, the mixture was diluted with aqueous 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 resulting mesylate was diluted with N,N-dimethylformamide (9 mL) and to the solution was added potassium carbonate (119 mg, 0.862 mmol) at room temperature. After the resultant mixture was stirred at 80° C. for 2 hr, the mixture was diluted with ethyl acetate, washed with water and 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 10-50% ethyl acetate/n-hexane gradient mixture to give the title compound as a solid (162 mg, 0.362 mmol, 84%). Analytically pure material was obtained by recrystallization from ethyl acetate/n-hexane.

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