S(OS([O-])=O)([O-])=O.[Na+].[Na+].[Cl:10][C:11]1[S:12][C:13]([CH:16]=O)=[CH:14][CH:15]=1.[NH2:18][C:19]1[CH:20]=[C:21]([CH2:26][C:27]([O:29][CH2:30][CH3:31])=[O:28])[CH:22]=[CH:23][C:24]=1[NH2:25].O>CN1CCCC1=O>[Cl:10][C:11]1[S:12][C:13]([C:16]2[NH:25][C:24]3[CH:23]=[CH:22][C:21]([CH2:26][C:27]([O:29][CH2:30][CH3:31])=[O:28])=[CH:20][C:19]=3[N:18]=2)=[CH:14][CH:15]=13.1 3.89 g (20.5 mmol) of sodium disulfite are added to a solution of 3.00 g (20.5 mmol) of 2-chlorothiophene-5-carbaldehyde and 3.98 g (20.5 mmol) of ethyl 3,4-diaminophenylacetate in 30 ml of 1-methyl-pyrrolidone, and the mixture is stirred at 110° C. for 18 hours. Water is added to the reaction mixture, which is extracted with dichloromethane. The organic phase is dried using sodium sulfate and evaporated, giving ethyl [2-(5-chlorothiophen-2-yl)-1H-benzimidazol-5-yl]acetate as a brown oil (ESI 321), which is employed without further purification for the next reaction.
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