Sodium Carbonate → 2',4'-Dichloro-2-(3-pyridyl)acetophenone O-isobutyloxime

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A solution of 4.65 g of 2',4'-dichloro-2-(3-pyridyl)acetophenone in 25 ml of ethanol is treated with 2.70 g of anhydrous sodium carbonate and 2.63 g of O-isobutylhydroxylamine hydrochloride and the reaction mixture is then heated to reflux temperature with stirring. After 4 hours, it is poured onto ice and extracted with ethyl acetate. The organic phase is washed with water, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. 2',4'-Dichloro-2-(3-pyridyl)acetophenone O-isobutyloxime is obtained as an E/Z isomer mixture in the form of a brownish oil. In the chromatographic separation on silica gel using n-hexane/ethyl acetate (7:3), the E isomer [1H-NMR (CDCl3, 200 MHz): 2.055 ppm (heptet, HC(CH3)2)] is eluted first and then the Z isomer [1H-NMR (CDCl3, 200 MHz): 1.928 ppm (heptet, HC(CH3)2)].

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