In 10 ml of dry tetrahydrofuran was dissolved 423 mg (1.00 mmol) of 5-(3,5-dichlorophenylthio)-4-isopropyl-2-(p-methoxybenzyloxymethyl)-1H-imidazole (16b), followed by addition of 205 mg (1.20 mmol) of benzyl bromide, 48 mg (1.2 mmol) of sodium hydroxide and 5 mg (0.015 mg) of tetrabutylammonium bromide at room temperature wit stirring, and the mixture was stirred at the same temperature for 3 hours. This reaction mixture was concentrated under reduced pressure and the residue was diluted with water and extracted with methylene chloride. The organic layer was washed with water and dried over sodium sulfate. The solvent was distilled off under reduced pressure and the residual oil was fractionated by silica gel chromatography (ethyl acetate: methylene chloride=1:9). From the first fraction, 33 mg (yield 6.5%) of the objective position isomer (17f) was obtained. From the subsequent fraction, 450 mg (yield 88%) of 1-benzyl-5-(3,5-dichlorophenylthio)-4-isopropyl-2-(p-methoxybenzyloxymethyl)-1H-imidazole (17f) was obtained.
