[NH2:1][S:2]([C:5]1[CH:16]=[C:15]([Cl:17])[CH:14]=[CH:13][C:6]=1[C:7]([O:9][CH:10]([CH3:12])[CH3:11])=[O:8])(=[O:4])=[O:3].[CH2:18]([N:22]=[C:23]=[O:24])[CH2:19][CH2:20][CH3:21].C([O-])([O-])=O.[K+].[K+]>CC(=O)CC>[CH2:18]([NH:22][C:23]([NH:1][S:2]([C:5]1[CH:16]=[C:15]([Cl:17])[CH:14]=[CH:13][C:6]=1[C:7]([O:9][CH:10]([CH3:12])[CH3:11])=[O:8])(=[O:4])=[O:3])=[O:24])[CH2:19][CH2:20][CH3:21]A mixture of 1063.4 g of isopropyl 2-(aminosulfonyl)-4-chlorobenzoate, 590.4 g of n-butyl isocyanate and 590.4 g of K2CO3 in 10.8 liters of 2-butanone are heated under reflux overnight. After cooling to room temperature, the reaction mixture is in each case poured into 10 liters of ice-water. The aqueous phase is extracted with 9 liters of methylene chloride. The aqueous phase is acidified to pH 1.0 using concentrated HCl, and the resulting precipitate is filtered off. After drying, 714.6 g of isopropyl 2-[N-(N-butylaminocarbonyl)aminosulfonyl]-4-chlorobenzoate (44% of theory) of melting point 129-132° C. are obtained.
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