4-Chlorobenzenesulfonamide → 1,1-Dimethylethyl 4-[(4-chlorophenyl)sulfonylaminocarbonyl]benzoate

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A 5-liter 3-neck round bottom flask was equipped with a mechanical stirrer and nitrogen inlet. CH2Cl2 (2 liters) was placed in the reaction flask and terephthalic acid mono-t-butyl ester (127.5 g, 0.574 mol), DMAP (70.06 g, 0.574 mol), and 4-chlorobenzenesulfonamide (110.04 g, 0.574 mol) were added in that order using CH2Cl2 (400 ml) to wash down the solids. WSCDI (110.10 g, 0.574 mol) was added in portions over 10 min using CH2Cl2 (100 ml) to wash down the solid. After the reaction mixture was stirred overnight at room temperature, it was concentrated under vacuum to dryness. The residue was partioned between EtOAc and water. The EtOAc solution was washed (20% aq citric acid, satd aq NaHCO3, brine), dried (Na2SO4), and concentrated under vacuum to a white solid. After drying in a vacuum oven at 50°, the title product (227 g, 100%) was obtained in a sufficiently pure state to be used directly for the next step; TLC, Rf =0.43, MeOH:CHCl3 (15:85). (Further purification was possible by recrystallization from EtOH:water; m.p. above 300°).

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