Lithium iodide → N-(3,4-dichlorophenylsulphonyl)-5-hydroxyindole-2-carboxylic acid

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Reaction Steps

A solution of anhydrous lithium iodide (870 mg) and methyl_N-(3,4-dichlorophenylsulphonyl)-5-hydroxyindole-2-carboxylate (260 mg) in pyridine (15 ml) was stirred at reflux for 4 hours. The reaction was cooled and concentrated in vacuo. The residue was dissolved in water (20 ml) and acidified with acetic acid. The product was extracted with ethyl acetate and the combined extracts were dried, concentrated in vacuo and the residue purified by column chromatography using dichloromethane-50% ethyl acetate containing 1% acetic acid as eluent to give the desired product as a glass (72 mg, 29%). NMR: δ 6.9 (m, 2H), 7.25 (s, 1H), 7.85 (d, 1H), 7.9 (m, 2H), 8.15 (s, 1H), 9.5 (s, 1H); m/z 385.8 (M−H−). The starting material was prepared by

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