[Br:1]N1C(=O)CCC1=O.[CH2:9]([C:11]1[NH:15][C:14]([C:16]([O:18][CH2:19][CH3:20])=[O:17])=[CH:13][CH:12]=1)[CH3:10].[OH-].[Na+]>C(Cl)Cl>[Br:1][C:12]1[CH:13]=[C:14]([C:16]([O:18][CH2:19][CH3:20])=[O:17])[NH:15][C:11]=1[CH2:9][CH3:10]N-Bromosuccinimide (5.86 g, 0.033 mol) was added to a solution of ethyl 5-ethyl-1H-pyrrole-2-carboxylate (Intermediate 12, 5.0 g, 0.03 mol) in DCM (85 ml) at 0° C., and the reaction was stirred for 30 minutes then poured to a chilled beaker containing 2 N NaOH (50 ml). The layers were separated and the aqueous layer was extracted with DCM (×3). The combined organic extracts were washed with water and brine, dried over magnesium sulfate and concentrated. The resultant dark brown solid was purified by flash chromatography (hexanes/EtOAc, 10:1) to give the title product as a white solid (5.0 g, 68%).
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