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DOI: 10.1055/s-2007-968452
Cu-Catalyzed [4+1] Cycloadditions of Enones with Diazo Compounds
Contributor(s):Hisashi Yamamoto, Matthew B. BoxerMassachusetts Institute of Technology, Cambridge, USA
Copper-Catalyzed Asymmetric [4+1] Cycloadditions of Enones with Diazo Compounds to Form Dihydrofurans
J. Am. Chem. Soc. 2007, 129: 1046-1047
Publication History
Publication Date:
24 April 2007 (online)
Key words
copper - [4+1] cycloaddition - dihydrofurans
Significance
This paper describes the enantioselective synthesis of 2,3-dihydrofurans through a copper-catalyzed [4+1] cycloaddition of enones and diazo compounds. The use of bpy* (1) as chiral ligand gave the best results when compared to a variety of other ligands including bis(oxazolines), semicorrin and others. Enones containing unsaturated substituents (i.e., aryl and heteroaryl) provided high ee values (87-93% ee), while alkyl-substituted enones gave only modest selectivities (71-78% ee).
Comment
The Fu group has further extended the success of their planar chiral ferrocene ligands to include this [4+1] cycloaddition reaction to access biologically important 2,3-dihydrofurans. The success of this class of ligands has proven to be very extensive and is surely a promising area for the future. The authors nicely present the utility of this reaction by showing that the products are amenable to further transformations including diastereoselective hydrogenation of the resultant olefin, reduction of the ester as well as hydrolysis.