Reaction of several α,β‐unsaturated ketoximes with N‐bromosuccinimide (NBS) gave isoxazoles, but yields were lower and the reaction less general than a similar transformation using iodine under basic conditions. With β,β‐disubstituted oximes, 4‐halo‐5,5‐disubstituted‐2‐isoxazolines were obtained using NBS, iodine, or N‐chlorosuccinimide. Treatment of the 4‐bromoisoxazo‐lines with silver acetate or silver nitrate caused either elimination with rearrangement to give isoxazoles or substitution at C‐4, depending upon the nature of the substituents at C‐5.
Aus den ungesättigten Ketoximen (I) entstehen mit N‐Bromsuccinimid (NBS) oder besser mit Iod/Alkali die Isoxazole (II), aus den Ketoximen (III) werden mit N‐Halogensuccinimiden die Halogenisoxazoline (IV) gebildet.
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