Enantioselective Synthesis of α,α-Disubstituted Cyclopentenes by an N-Heterocyclic Carbene-Catalyzed Desymmetrization of 1,3-Diketones

The enantioselective synthesis of α,α-disubstituted cyclopentenes using N-heterocyclic carbene catalysis is reported. This desymmetrization reaction proceeds via a chiral enol generated in situ from the combination of an enantiopure azolium salt and α,β-unsaturated aldehyde. This reactive enol under...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2007-08, Vol.129 (33), p.10098-10099
Main Authors: Wadamoto, Manabu, Phillips, Eric M, Reynolds, Troy E, Scheidt, Karl A
Format: Article
Language:English
Subjects:
Catalysis
Cyclopentanes - chemical synthesis
Cyclopentanes - chemistry
Ketones - chemical synthesis
Ketones - chemistry
Stereoisomerism
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Summary:The enantioselective synthesis of α,α-disubstituted cyclopentenes using N-heterocyclic carbene catalysis is reported. This desymmetrization reaction proceeds via a chiral enol generated in situ from the combination of an enantiopure azolium salt and α,β-unsaturated aldehyde. This reactive enol undergoes addition to one of two enantiotopic ketones to afford an optically active β-lactone after the intermediate carbinol is involved in an internal acylation event to release the carbene catalyst. In the substrates where R = aryl, a decarboxylation occurs immediately after lactone formation to produce the quaternary center-containing cyclopentene products in up to 96% ee. When the R group is alkyl, the β-lactones are isolated in moderate yield and high diastereo- and enantioselectivity.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja073987e