Into a solution of 227 mg of triphosgene in 8 ml of ethyl acetate, a solution of 155 mg of triethylamine and 250 mg of 4-chloro-2-fluoro-5-{2-(methoxycarbonyl)methoxy-3-pyridyloxy}aniline in 8 ml of ethyl acetate was added at 0° C. The mixture was stirred for 30 minutes at the same temperature, then for 2 hours at reflux temperature. The reaction solution was filterated while it was hot, and the solvent was distilled off under reduced pressure to obtain 266 mg of 4-chloro-2-fluoro-5-{2-(methoxycarbonyl)methoxy-3-pyridyloxy}phenyl isocyanate.
