To a mixture of {2-[3-(t-butoxycarbonylaminomethyl)-4-cyanophenylimino]-2-(5-ethyl-2-fluoro-3-hydroxyphenyl)-1-methylsulfanylethylidene}carbamic acid methyl ester (346 mg) and DMF (6 mL) there were added cesium carbonate (235 mg) and (2-iodoethoxy)triisopropylsilane [CAS No. 93550-77-7] (323 mg) in that order, under a nitrogen atmosphere The mixture was stirred for 40 hours at room temperature, and then ethyl acetate (200 mL) and water (50 mL) were added. The mixture was sufficiently shaken, and then the organic layer was separated oft washed twice with water (50 mL) and once with saturated aqueous sodium chloride (50 mL) in that order, and dried over anhydrous magnesium sulfate. The mixture was filtered to obtain a filtrate, and the solvent in the filtrate was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate-heptane mixture) to obtain the target compound (406 mg) as an off-white oil.
