[OH:1][C:2]1[CH:12]=[CH:11][C:10]([C:13]#[C:14][C:15]2[CH:20]=[CH:19][C:18]([S:21]([Cl:24])(=[O:23])=[O:22])=[CH:17][CH:16]=2)=[CH:9][C:3]=1[C:4]([O:6][CH2:7][CH3:8])=[O:5].S(=O)(=O)(O)O.[Cl-].[Na+].[C:32](OC(=O)C)(=[O:34])[CH3:33]>C1(C)C=CC=CC=1>[C:32]([O:1][C:2]1[CH:12]=[CH:11][C:10]([C:13]#[C:14][C:15]2[CH:20]=[CH:19][C:18]([S:21]([Cl:24])(=[O:23])=[O:22])=[CH:17][CH:16]=2)=[CH:9][C:3]=1[C:4]([O:6][CH2:7][CH3:8])=[O:5])(=[O:34])[CH3:33]Ethyl 2-hydroxy-5-[(4-chlorosulfonylphenyl]ethynyl]benzoate (16 g, 44 mmol) was dissolved in acetic anhydride (40 ml) at 120° C. Sulfuric acid (about 0.4 ml) was added dropwise. After 5 min the solution was diluted with toluene (about 100 ml) and added to saturated sodium chloride solution with vigorous stirring. The phases were separated, the toluene solution dried and evaporated. More toluene was added and the evaporation repeated. The oily product crystallized. The product was sufficiently pure for the next step. Yield 17.0 g (95%).
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