Asymmetric Nitrocyclopropanation of α-Substituted α,β-Enals Catalyzed by Diphenylprolinol Silyl Ether for the Construction of All-Carbon Quaternary Stereogenic Centers
The diphenylprolinolsilylether mediated asymmetricnitrocyclopropanation of α-substitutedα,β-unsaturated aldehydes with bromonitromethane, followed by base-promoted isomerization was found to afford trans-nitrocyclopropanecarbaldehydes with all-carbonquaternarystereogeniccenters with excellent diastereo- and enantioselectivities. DFT calculations indicated that the s-trans conformer of the iminium
Mono- and Bis-Acrolein Derivatives by Reliable and Efficient One-Step Methylenation of Aldehyde Precursors
作者:Leo Paquette、Kallol Basu、Jonathan Richards
DOI:10.1055/s-2004-834866
日期:——
A series of aldehydes carrying different functional groups was transformed directly into the α-methylene derivatives. Dialdehydes behaved comparably at both active sites. When keto aldehydes are involved, excellent levels of chemoselectivity are observed, with the ketone substructures exhibiting no sign of reactivity.
Asymmetric Epoxidation of α-Substituted Acroleins Catalyzed by Diphenylprolinol Silyl Ether
作者:Bojan P. Bondzic、Tatsuya Urushima、Hayato Ishikawa、Yujiro Hayashi
DOI:10.1021/ol102269s
日期:2010.12.3
Asymmetric epoxidation of α-substituted acroleins with hydrogen peroxide has been catalyzed by diphenylprolinol diphenylmethylsilyl ether to afford α-substituted-β,β-unsubstituted-α,β-epoxy aldehyde with excellent enantioselectivity and the generation of a chiral quaternary carbon center. The method was applied to a short synthesis of (R)-methyl palmoxirate.