4.78 g of (5-amino-2-butyl-benzofuran-3-yl)-[4-(3-dibutylamino-propoxy)-phenyl]-methanone (III) (0.01 mol, 1 eq) and 35 mL of pyridine were placed into a flask. The mixture was cooled down to 0° C. and 0.99 g of methanesulfenyl chloride (II) (0.012 mol, 1.2 eq; freshly prepared as described in the above mentioned literature) was added in 10 min. The mixture was stirred at 0° C. for 3 hours and then heated to room temperature and stirred for 6 hours. The mixture was poured into 100 mL of water. The product was extracted with 50 mL of dichloromethane. The organic phase was washed with 30 mL of water. The solvent was evaporated and the product was purified by column chromatography (column: spheric silica (60 Å); eluent: toluene:ethyl acetate=70:30) to obtain 2.2 g of compound (IV) (42%) as a light yellow oil.
