To the solution of 1 (diclofenac, 1717 mg, 5.8 mmol) in 60 mL of dimethylformamide, hydroxybenzotriazole (862 mg, 6.38 mmol) and DCC (1316 mg, 6.38 mmol) were added with stirring at 0° C. for 1 h. To the reaction mixture 4-hydroxyphenylisothiocyanate (2; 965 mg, 6.38 mmol) was added and stirred for 1 h at 0° C. and 2 h at room temperature. After filtration, the filtrate was evaporated under reduced pressure to remove the solvent. The oily residue thus obtained was dissolved in ethyl acetate and the precipitate was removed. The solvent was evaporated and the crude product was loaded on a silica gel open column and eluted with chloroform/n-hexane 9:1, from which 4-isothiocyanatophenyl 2-(2-(2,6-dichlorophenylamino)phenyl)acetate (3) was obtained (580 mg, 23% yield).
