A Chloroacetophenone oxime

I mol. chloroacetophenone reacts with 3 mols. hydroxylamine hydrochloride in dilute methanol solution at ordinary temperatures, with formation of a-chloroacetophenone oxime, of the formula ... 

The enol ether is dissolved in 25 mL of rm-butyl methyl ether/mmol of alkene, and treated with 0.5-1.0 equiv of a-chloroacetophenone oxime. Then 6-10 equiv of freshly ground anhyd Na,C03 are added and the mixture is stirred for 6-10d at 20°C. The progress of the reaction is monitored by TLC. Filtration through a short pad of Celite followed by evaporation provides the crude 1,2-oxazines which are purified by column chromatography (aluminum oxide III, neutral, pentane/fert-butyl methyl ether 9 1) to furnish the pure cycloadducts. 

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