After adding 2.97 ml of collidine and 1.74 ml of methyl chloroformate to a solution of 2.01 g of 2-(4-cyanophenylimino)-2-(2-fluoro-3,5-dimethoxyphenyl)thioacetimidic acid methyl ester in 80 ml of toluene, the mixture was stirred at 85° C. for 20 hours under a nitrogen atmosphere. After cooling the reaction mixture, 400 ml of ethyl acetate and 200 ml of a 2% aqueous sulfuric acid solution were added and the organic layer was washed with 300 ml of water and 300 ml of saturated brine. The organic layer was 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 (heptane-ethyl acetate (3:2)) to give the title compound (1.89 g) as a light yellow solid.
