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DOI: 10.1055/s-0028-1083425
1,4-Addition of Alkyl and Aryl-Aluminums to Cyclic Enones
Contributor(s):Mark Lautens, Jane PanteleevBoston College, Chestnut Hill, USA
Enantioselective Synthesis of All-Carbon Quaternary Stereogenic Centers by Catalytic Asymmetric Conjugate Additions to Alkyl and Aryl Aluminum Reagents to Five-, Six-, and Seven-Membered-Ring β-Substituted Cyclic Enones
Angew. Chem. Int. Ed. 2008, 47: 7358-7362
Publication History
Publication Date:
23 October 2008 (online)
Key words
organoaluminum reagents - asymmetric 1,4-addition - NHC ligands - copper catalysis
Significance
The authors report the 1,4-addition of organoaluminum reagents to unactivated β-substituted cyclopentenones, which previously comprised a difficult set of substrates for this reaction. A moderate range of compounds bearing quaternary centers in high enantiomeric purity is produced.
Review
A. Alexakis, J. E. Bäckvall, N. Krause, O. Pàmies, M. Diéguez Chem. Rev. 2008, 108, 2796-2823.
Comment
The use of a new NHC ligand and reactive organoaluminum reagents leads to an advance over the group’s previous work on this reaction (Angew. Chem. Int. Ed. 2007, 46, 1097). Addition of aryl nucleophiles is possible, where the aryl-aluminum reagents are prepared from aryllithiums and dimethylaluminum chloride prior to use. The reaction works well with electron-rich and -poor aromatics, and the selectivity is higher when ortho substituents are present. This work presents an improvement in the reaction with larger rings, since lower catalyst loading is required.