Synfacts 2009(12): 1405-1405  
DOI: 10.1055/s-0029-1218213
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart ˙ New York

NHC-Catalyzed Conjugate Addition Involving α,β-Unsaturated Acyl Azoliums

Contributor(s): Benjamin List, Kristina Zumbansen
S. J. Ryan, L. Candish, D. W. Lupton*
Monash University, Clayton, Australia
Further Information

Publication History

Publication Date:
20 November 2009 (online)


Lupton and co-workers report a conjugate addition involving α,β-unsaturated acyl azoliums catalyzed by N-heterocyclic carbenes (NHCs). A variety of conjugate acceptors including those having β-disubstitution reacted easily with a range of enolates affording the corresponding ­dihydropyranones in good yields. The proposed mechanistic pathway suggests a fragmentation of the α,β-unsaturated enol ester to enolate I and α,β-unsaturated carboxylate II. An intermolecular version of this transformation is also possible.