[Br:1]N1C(=O)CCC1=O.[Cl:9][C:10]1[CH:15]=[CH:14][C:13]([C:16]2[N:20]([CH2:21][CH3:22])[C:19]([C:23](=[O:26])[CH2:24][CH3:25])=[CH:18][C:17]=2[CH3:27])=[CH:12][CH:11]=1.C(OCC)(=O)C>C1COCC1>[Br:1][C:18]1[C:17]([CH3:27])=[C:16]([C:13]2[CH:14]=[CH:15][C:10]([Cl:9])=[CH:11][CH:12]=2)[N:20]([CH2:21][CH3:22])[C:19]=1[C:23](=[O:26])[CH2:24][CH3:25]A solution of N-bromosuccinimide (0.35 g, 1.99 mmol) in THF (10 ml) was added dropwise to a stirred solution of 1-(5-(4-chlorophenyl)-1-ethyl-4-methyl-1H-pyrrol-2-yl)propan-1-one (compound 51b, 0.5 g, 1.81 mmol) in THF (25 ml) at about −78° C. The resulting reaction mixture was stirred at about −78° C. for 5 hr. The reaction mixture was then allowed to warm to 25° C. slowly during further 3 to 4 hr. The progress of the reaction was monitored by TLC. The solvent was evaporated from the reaction mixture under reduced pressure and to the residue so obtained was added ethyl acetate (50 ml). The mixture so obtained was washed with saturated sodium bicarbonate solution (1×30 ml) followed by washing with water (1×30 ml). The combined organic layer was then dried over anhydrous Na2SO4. The solvent was evaporated from the dried organic layer under reduced pressure to obtain a crude product, which was then purified by flash column chromatography 10% ethyl acetate in hexanes as an eluent to obtain the title compound (0.5 g, 78.0%).
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