The crude 2-(4-tert-butyl-benzenesulfonylamino)-5-chlorobenzoyl chloride was dissolved in dichloromethane (300 mL) and transferred to an addition funnel. Hydrazine hydrate (212 mL, 4.35 mol), dissolved in 1.2 L dichloromethane in a 4 L Erlenmeyer flask, was cooled to −10° C. in a dry ice-acetone bath and the acyl chloride solution was added in a slow stream to the stirring hydrazine solution over a 15 minute period. The cold bath was subsequently removed following the addition and LCMS analysis at 15 minutes indicated the reaction was complete. The resultant reaction mixture was quenched with water (500 mL), resulting in a voluminous white precipitate that was collected by vacuum filtration. The precipitate was slurried in 800 mL ethyl acetate and acetic acid was added while stirring until a homogeneous solution was formed. The solution was transferred to a separatory funnel and extracted with 3×100 mL of water. The aqueous phases were discarded and the organic phase was dried over sodium sulfate, filtered, and concentrated in vacuo to produce 4-tert-butyl-N-(4-chloro-2-hydrazinocarbonyl-phenyl)benzenesulfonamide (71 g) in an 85% yield: HPLC retention time=2.49 minutes; MS (ES) M+H expected 382.0, found 382.0.
