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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Oxonium Ion Mediated Synthesis of 4-Substituted Spiro-Isoxazolines
Eric McClendon1, Ann O Omollo, Edward J Valente
1Department of Chemistry, College of Science, Engineering and Technology, Jackson State University, Jackson, MS 39217 USA.
Abstract:
The stereoselective synthesis of 4-bromo-spiro-isoxazolines was achieved in one step through the bromination of various isoxazoles that contain a pendant alcohol or carboxylic acid functional group. Isoxazole bromination leads to a bromonium ion intermediate which opens either by neighboring oxygen lone pair electrons or by intramolecular nucleophilic attack. Single X-ray crystal data provides evidence that the two contiguous stereocenters of the spiro-isoxazoline are formed by the anti intramolecular attack of the nucleophile relative to bromine since there is an anti stereochemical relationship between the spirocyclic ring oxygen and the bromine atom.
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