To the solution of 1 (naproxen, 595 mg, 2.58 mmol) in 20 mL of dimethylformamide, hydroxybenzotriazole (388 mg, 2.87 mmol) and DCC (593 mg, 2.87 mmol) were added with stirring at 0° C. for 1 h. To the reaction mixture 5-p-hydroxyphenyl-1,2-dithiole-3-thione (2; 650 mg, 2.87 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; the organic layer was washed with brine, with NaHCO3 5%, with citric acid 10% and than dried on anhydrous MgSO4, filtered and the solvent evaporated. The crude product was loaded on a silica gel open column and eluted with dichloromethane, from which 4-(5-thioxo-5H-1,2-dithiol-3-yl)phenyl 2-(2-methoxynaphthalen-6-yl)propanoate (3) was obtained (406 mg, 36% yield).
