[CH3:1][O:2][C:3]([C:5]1[NH:6][CH:7]=[C:8]([I:10])[CH:9]=1)=[O:4].C(N(CC)CC)C.[C:18]1([CH3:28])[CH:23]=[CH:22][C:21]([S:24](O)(=[O:26])=[O:25])=[CH:20][CH:19]=1>ClCCl.CN(C)C1C=CN=CC=1>[CH3:1][O:2][C:3]([C:5]1[N:6]([S:24]([C:21]2[CH:22]=[CH:23][C:18]([CH3:28])=[CH:19][CH:20]=2)(=[O:26])=[O:25])[CH:7]=[C:8]([I:10])[CH:9]=1)=[O:4]4-Iodo-1H-pyrrole-2-carboxylic acid methyl ester 57d (25.1 g, 100 mmol) was dissolved in 150 mL of dichloromethane followed by addition of triethylamine (30.6 mL, 220 mmol), 4-dimethylaminopyridine (1.22 g, 10 mmol) and p-toluenesulfonic acid (21 g, 110 mmol). The reaction mixture was reacted at 20° C. overnight. The reaction was monitored by TLC until the disappearance of the starting materials and quenched by addition of 30 mL of hydrochloric acid (1 N). The mixture was extracted with dichloromethane (50 mL×3). The combined organic extracts were washed with saturated aqueous sodium carbonate and saturated brine successively, dried over anhydrous sodium sulfate, filtered to remove the drying agent and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to obtain the title compound 4-iodo-1-(toluene-4-sulfonyl)-1H-pyrrole-2-carboxylic acid methyl ester 57e (32.5 g, yield 80.2%) as a white solid.
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