Nitrile Ylides: Diastereoselective Cycloadditions using Chiral Oxzolidinones Without Lewis Acid
摘要:
Lewis acid complexation is generally required for chiral-auxiliary-controlled stereoselectivity, and chiral Lewis acid catalysis is frequently optimal for introducing asymmetry. In this work, we show that nitrile ylide cycloadditions to electron-poor acceptors attached to chiral auxiliaries proceed in high yield and stereoselectivity In the absence of Lewis acids. In contrast, chiral Lewis acids are inferior in these cycloadditions.
The samarium(II)-mediated intermolecular couplings of ketones and β-alkoxyacrylates: a short asymmetric synthesis of an antifungal γ-butyrolactone
摘要:
The samarium(II) iodide-mediated coupling of ketones with beta-alkoxyacrylatcs gives beta-hydroxy-gamma-butyrolactones in moderate yield. The process has been applied to the asymmetric synthesis of an antifungal, gamma-butyrolactone natural product. (C) 2004 Elsevier Ltd. All rights reserved.