3,5-Dichloroaniline → Ethyl 4-[4-chloro-2-[(3,5-dichlorophenyl)amino]-7-(1-ethylpropyl)-1H-benzimidazol-1-yl]butanoate

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Reaction Steps

A mixture of ethyl 4-[2,4-dichloro-7-(1-ethylpropyl)-1H-benzimidazol-1-yl]butanoate (Reference Example 33; 500 mg, 1.35 mmol), 3,5-dichloroaniline (655 mg, 4.04 mmol) and p-toluenesulfonic acid monohydrate (257 mg, 1.35 mmol) in 1-methyl-2-pyrrolidinone (4 mL) was irradiated by microwave at 180° C. for 15 min. After cooling, aqueous sodium bicarbonate was added and the mixture was extracted with ethyl acetate. Organic layer was washed with water and brine, dried over anhydrous sodium sulfate and concentrated in vacuo. The residue was purified by flash chromatography on silica gel eluting with a 5-20% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give a residue, which was purified by preparative HPLC to give the title compound (270 mg, 0.542 mmol, 40%) as a colorless amorphous.

Provenance & Evidence