ORGN 88 |
| Δ2-Isoxazolines have found use as ring systems in many pharmaceutical agents and serve as “protecting groups” for â-hydroxy ketones and â-amino alcohols. This class of heterocycle is typically prepared via the 1,3-dipolar cycloaddition of a nitrile oxide with a substituted alkene. The regiochemistry of this reaction is dictated by the electronic and steric requirements of the cycloaddition; stereochemical concerns also result in the production of racemic mixtures. We wish to report the synthesis of 3,5-disubstituted-Δ2-isoxazolines via the palladium-mediated nucleometalation/methoxycarbonylation of β,γ-unsaturated oximes. This reaction provides a convenient and regiospecific route to substituted isoxazolines. Moreover, the use of chiral bidentate ligands results in the stereoselective formation of enantiomeric isoxazolines. The steric requirements for ligands with good enantiomeric excess, the mechanism of the cyclization, and the implications for the formation of optically pure isoxazolines will be discussed.
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Physical Organic Chemistry, Combinatorial and Process Chemistry, New Reactions and Methodology, Peptides, Proteins and Amino Acids
8:00 PM-10:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Hall A, Poster
Division of Organic Chemistry |
