[Br:1][C:2]1[C:10]2[NH:9][C:8](=[O:11])[NH:7][C:6]=2[CH:5]=[C:4]([Br:12])[C:3]=1[C:13]([O:15][CH3:16])=[O:14].[H-].[Na+].[CH2:19](Br)[CH2:20][CH:21]([CH3:23])[CH3:22].Cl>CN(C)C=O.O.C(OCC)(=O)C>[Br:1][C:2]1[C:10]2[N:9]([CH2:19][CH2:20][CH:21]([CH3:23])[CH3:22])[C:8](=[O:11])[N:7]([CH2:10][CH2:2][CH:3]([CH3:13])[CH3:4])[C:6]=2[CH:5]=[C:4]([Br:12])[C:3]=1[C:13]([O:15][CH3:16])=[O:14]In 10 ml of N,N-dimethylformamide are suspended 0.95 g of methyl 4,6-dibromo-2-oxo-2,3-dihydro-1H-benzimidazole-5-carboxylate, 0.24 g of 60% sodium hydride and 0.7 ml of isopentyl bromide. The suspension is stirred at 50-60° C. for 3 hours. The reaction mixture is added to a mixture of ethyl acetate and water, pH is adjusted to 2 with 2 mol/L hydrochloric acid, and the organic layer is separated. The organic layer thus obtained is washed with water and saturated aqueous solution of sodium chloride successively and dried over anhydrous magnesium sulfate, and then the solvent is distilled off under reduced pressure. Thus, 0.71 g of methyl 4,6-dibromo-1,3-diisopentyl-2-oxo-2,3-dihydro-1H-benzimidazole-5-carboxylate is obtained as a light brown-colored solid product.
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