[Cl:1][C:2]1[NH:3][C:4]2[CH:10]=[CH:9][CH:8]=[CH:7][C:5]=2[N:6]=1.[H-].[Na+].Cl[CH2:14][C:15]1[O:16][C:17]([C:20]([O:22][CH2:23][CH3:24])=[O:21])=[CH:18][CH:19]=1>CN(C)C=O.O>[Cl:1][C:2]1[N:6]([CH2:14][C:15]2[O:16][C:17]([C:20]([O:22][CH2:23][CH3:24])=[O:21])=[CH:18][CH:19]=2)[C:5]2[CH:7]=[CH:8][CH:9]=[CH:10][C:4]=2[N:3]=1Combine 2-chlorobenzimidazole (10.0 g, 66 mmol), and dimethylformamide (100 mL). Add portionwise sodium hydride (1.63 g, 68 mmol). After the evolution of gas ceases, add a solution of ethyl 2-chloromethyl-5-furoate (12.45 g, 0.66 mmol) in dimethylformamide (20 mL). After 18 hours, dilute the reaction mixture with water and extract four times with diethyl ether. Combine the organic layers and extract with water and then brine. Dry the organic layer over Na2SO4, filter, and evaporate in vacuo to give a residue. Chromatograph the residue eluting with 5% methanol/0.2% concentrated aqueous ammonia solution/dichloromethane to give 2-chloro-1-(5-ethyoxycarbonylfur-2-ylmethyl)-1H-benzimidazole.
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