Oxonium Ion Mediated Synthesis of 4-Substituted Spiro-Isoxazolines.
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.
Department of Chemistry, College of Science, Engineering and Technology, Jackson State University, Jackson, MS 39217 USA.
Eric
E
McClendon
Ann O
AO
Omollo
Edward J
EJ
Valente
Ashton T
AT
Hamme