[CH3:1][N:2]1[CH:6]=[C:5]([N+:7]([O-])=O)[CH:4]=[C:3]1[C:10]([OH:12])=[O:11].C(=O)([O-])[O-].[Na+].[Na+].[C:19]1([S:25](Cl)(=[O:27])=[O:26])[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=1>[Pd].C1COCC1>[CH3:1][N:2]1[CH:6]=[C:5]([NH:7][S:25]([C:19]2[CH:24]=[CH:23][CH:22]=[CH:21][CH:20]=2)(=[O:27])=[O:26])[CH:4]=[C:3]1[C:10]([OH:12])=[O:11]1-Methyl-4-nitro-1H-pyrrole-2-carboxylic acid (Int. 15) (350 mg, 2.057 mmol) was dissolved in aqueous 1M sodium carbonate (15 ml, 15.00 mmol); 10% Pd/C (219 mg) was added, and the mixture was hydrogenated in a Parr apparatus at 40 psi for 2 hours. The catalyst was filtered off maintaining the mixture under nitrogen flow and the filtrate was collected in a cooled flask (ice bath). THF (20 ml) and benzenesulfonyl chloride (0.318 ml, 2.469 mmol) were added to the cooled solution and the resulting mixture was stirred at 0° C. for 0.5 hours and then at RT for 1 hour. The reaction mixture was extracted with Et2O and the organic layer was discarded. The aqueous layer was cautiously acidified by addition of solid KHSO4 to pH=3 and extracted twice with DCM. The combined organic layers were dried over Na2SO4 and the solvent was removed under vacuum to afford 1-methyl-4-(phenylsulfonamido)-1H-pyrrole-2-carboxylic acid (Int. 16) (540 mg, 1.927 mmol, MS/ESI+280.9 [MH]+), which was used without purification.
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