Azobisisobutyronitrile → Ethyl [4-chloro-7-(1-ethylpropyl)-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl]acetate

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Reaction Conditions

Reaction Steps

To a solution of ethyl [7-(1-ethylpropyl)-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl]acetate (3.91 g, 13.5 mmol) and 2,2′-azobisisobutyronitrile (222 mg, 1.35 mmol) in chlorobenzene (40 mL) was added portionwise N-chlorosuccinimide (1.80 g, 13.5 mmol) at 65° C., and the mixture was stirred at 70° C. for 2 days. After cooling, the reaction mixture was washed with saturated aqueous sodium hydrogen carbonate. The aqueous layer was separated and extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous sodium sulfate and concentrated in vacuo. The residue was purified by silica gel column chromatography eluting with a 15-50% ethyl acetate/n-hexane gradient mixture, and the fractions containing the title compound were concentrated in vacuo. The mixture was suspended in diisopropyl ether, and the suspension was stirred at 60° C. for 2 hr. After cooling, the resulting solid was collected by filtration and washed with n-hexane to give the title compound (2.77 g, 8.53 mmol, 63%) as a colorless solid.

Provenance & Evidence