ORGN 555 |
| Olefin isomerization-Claisen rearrangement (ICR) reactions render easily obtained di(allyl) ethers as direct progenitors of enantioselective aliphatic Claisen sigmatropic rearrangements. ICR reactions achieve the catalyzed isomerization of di(allyl) ethers to the corresponding allyl vinyl ethers which undergo highly stereoselective, in situ sigmatropic rearrangement. Exploiting the ICR reaction design to develop operationally simple, enantioselective aliphatic Claisen rearrangements will be described. Specifically, the ICR methodology provides the opportunity for generating enantioenriched di(allyl) ether ICR substrates in a single step from readily obtained conjugated enals. Merging asymmetric di(allyl) ether construction with ensuing olefin isomerization-Claisen rearrangement constitutes an especially concise entry to enantioselective aliphatic Claisen rearrangements. These transformations also provide a convenient strategy for enantioselective quaternary carbon construction. The development of transition metal-catalyzed aliphatic Claisen rearrangements affording access to the stereochemically complementary anti-Claisen adducts will also be described. The complementary relationship existing between the thermal and transition metal-catalyzed asymmetric ICR variants will be highlighted in selected applications to complex molecule synthesis.
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Asymmetric Reactions and Syntheses
1:00 PM-5:00 PM, Wednesday, 31 August 2005 Washington DC Convention Center -- 201, Oral
Division of Organic Chemistry |
