Web Release Date: March 3,
Enantioselective, Cyclopentene-Forming Annulations via NHC-Catalyzed Benzoin-Oxy-Cope Reactions
Department of Chemistry and Biochemistry, University of California at Santa Barbara, Santa Barbara, California 93106-9510
Received January 24, 2007
Abstract:
Chiral N-heterocyclic carbene catalysts generated from triazolium salts promote the cyclopentene-forming annulation of 
,
-unsaturated aldehydes and 4-oxoenoates with excellent levels of enantioinduction and preference for the cis-1,3,4-trisubstituted cyclopentene diastereomer. Although the observed products could arise by conjugate additions of catalytically generated homoenolates, our mechanistic and stereochemical investigations strongly support a novel reaction manifold featuring an intermolecular crossed-benzoin reaction and an NHC-catalyzed oxy-Cope rearrangement.
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