After adding 0.489 g of cesium carbonate and 0.348 ml of (3-bromopropoxy)-t-butyldimethylsilane to a solution of 0.401 g of [2-(4-cyanophenylimino)-2-(2-fluoro-3-hydroxy-5-methoxyphenyl)-1-methylsulfanylethylidene]carbamic acid methyl ester in 10 ml of DMF, the mixture was stirred at room temperature for 24 hours. Next, 50 ml of water was added to the reaction mixture and extraction was performed with 100 ml of ethyl acetate. The organic layer was washed with 50 ml of water and 50 ml of saturated brine in that order and then dried over anhydrous magnesium sulfate. The desiccating agent was filtered off and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate-heptane) to give 0.517 g of the title compound.
