1,2-Dichloroethane → N-(2,4-dichlorobenzoyl)-4-(tert-butyldimethylsilyloxy)-phenylsulfonamide

To a stirring solution of 2,4-dichlorobenzoic acid (1.25 eq) in dry dichloromethane (10 mL/mmol), 4-(tert-butyl-dimethylsiloxy)phenylsulfonamide (1.0 eq) is added in one portion followed by EDC (1.25–1.5 eq) and finally, NN-dimethyl-4-aminopyridine (1.2 equiv). The mixture is vigorously stirred under nitrogen for 16 hr, concentrated under reduced pressure, and the residue partitioned between ethyl acetate and water. The organic layer is washed with 1N hydrochloric acid (4 times, 20 mL/mmol), then the combined aqueous phases extracted with ethyl acetate (twice, 20 mL/mmol). The combined organic layers are finally washed with water and saturated aqueous sodium chloride, dried over sodium sulfate and concentrated under reduced pressure. The residue is purified by silica gel chromatography or crystallization if necessary or desired. ESI-MS m/e 458.0 (M+−H; 460.0 (M++H).