Dichloroethane (5 ml), thionyl chloride (0.65 g, 5.5 mmol) and dimethylformamide (0.05 ml) were added to 2-(2,5-dimethylphenoxymethyl)-α-methoxyiminophenylacetic acid (1.57 g, 5 mmol), and the mixture was stirred under reflux for 2 hours. After completion of the reaction, the mixture was concentrated under reduced pressure, pyridine (3 ml) and 1-hydroxyimino-l-propylamine (0.88 g, 10 mmol) were added to the residue, and the mixture was stirred under reflux for 0.5 hours. After completion of the reaction, ether (150 ml) was added, and the mixture was washed with 1N hydrochloric acid (150 ml) twice. The ether layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure, and the residue was purified by silica gel chromatography (ethyl acetate/n-hexane) and recrystallized from ethyl acetate/n-hexane to give 2-(2,5-dimethylphenoxymethyl)phenyl 3-ethyl-1,2,4-oxadiazol-5-yl ketone O-methyloxime (0.63 g, 34.5%) as colorless crystals.
