Cl[C:2]1[N:6]([CH2:7][CH2:8][CH2:9][C:10]([O:12][CH2:13][CH3:14])=[O:11])[C:5]2[C:15]([CH:20]([CH2:23][CH3:24])[CH2:21][CH3:22])=[CH:16][CH:17]=[C:18]([Cl:19])[C:4]=2[N:3]=1.[N-:25]=[N+:26]=[N-:27].[Na+].O>CN1CCCC1=O>[N:25]([C:2]1[N:6]([CH2:7][CH2:8][CH2:9][C:10]([O:12][CH2:13][CH3:14])=[O:11])[C:5]2[C:15]([CH:20]([CH2:23][CH3:24])[CH2:21][CH3:22])=[CH:16][CH:17]=[C:18]([Cl:19])[C:4]=2[N:3]=1)=[N+:26]=[N-:27]A mixture of ethyl 4-[2,4-dichloro-7-(1-ethylpropyl)-1H-benzimidazol-1-yl]butanoate (Reference Example 33; 7.40 g, 20.0 mmol) and sodium azide (2.60 g, 40.0 mmol) in 1-methyl-2-pyrrolidinone (20 mL) was stirred at 110° C. for 12 hr. After cooling, water was added to the mixture, which 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 10-30% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the title compound (4.90 g, 12.9 mmol, 64%) as a pale yellow solid.
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