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DOI: 10.1055/s-2006-942428
General Method for the Synthesis of Isoxazoline N-Oxides from Aliphatic Nitro Compounds
Publikationsverlauf
Publikationsdatum:
24. Juni 2006 (online)
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Abstract
A method for the synthesis of isoxazolines N-oxides from primary aliphatic nitro compounds and olefins based on the 1,3-dipolar cycloaddition of intermediate 1-halo-substituted silyl nitronates, followed by halosilane elimination has been described. The nature of the halogen atom plays a key role in determining the stability and reactivity of all intermediates of this process. Bromonitro compounds can be conveniently used in reactions with terminal alkenes, while fluorinated derivatives must be employed for internal olefins.
Key words
aliphatic nitro compounds - silyl nitronates - 1-halo-substituted nitro compounds - 1,3-dipolar cycloaddition
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References
In a preliminary experiment we observed that the cycloaddition of a 1-chlorosilyl nitronate proceeded slightly faster than that of analogous bromo derivative.
7The rate of elimination of halosilane from 3-halo-N-silyloxyisoxazolidines depends on many factors such as nature of the halogen and structural features of the heterocyclic ring. For instance, reaction of tert-butyl-dimethylsilyl nitronate from 1-bromonitroethane with di(methoxycarbonyl)acetylene affords cycloadduct, which does not eliminate bromosilane at room temperature. The mechanism of halosilane elimination is currently under investigation.
8Upon chromatography adduct 5b decomposed completely, whereas for 5b′ one diasteromer could be isolated.