Stereoselective Synthesis of Fluoroalkenoates and Fluorinated Isoxazolidinones: N-Substituents Governing the Dual Reactivity of Nitrones
作者:G. K. Surya Prakash、Zhe Zhang、Fang Wang、Martin Rahm、Chuanfa Ni、Marc Iuliucci、Ralf Haiges、George A. Olah
DOI:10.1002/chem.201303509
日期:2014.1.13
α‐Fluoroalkenoates and 4‐fluoro‐5‐isoxazolidinones are of vast interest due to their potential biological applications. We now demonstrate the syntheses of (E)‐α‐fluoroalkenoates and 4‐fluoro‐5‐isoxazolidinones by the reactions between nitrones and α‐fluoro‐α‐bromoacetate. By altering N‐substituents in nitrones, (E)‐α‐fluoroalkenoates and 4‐fluoro‐5‐isoxazolidinones can be achieved, respectively, with
Highly Diastereo- and Enantioselective Additions of Homoenolates to Nitrones Catalyzed by <i>N</i>-Heterocyclic Carbenes
作者:Eric M. Phillips、Troy E. Reynolds、Karl A. Scheidt
DOI:10.1021/ja710521m
日期:2008.2.1
diastereo- and enantioselective addition of N-heterocyclic carbene-generated homoenolates to nitrones is reported. This formal [3 + 3] addition of α,β-unsaturatedaldehydes and nitrones generates unusual morpholinone heterocycles which are converted into γ-hydroxy amino esters by addition of methanol to the reaction. The use of a chiral N-heterocyclic carbene (NHC) as the catalyst provides the amino esters
Controlling Asymmetric Remote and Cascade 1,3-Dipolar Cycloaddition Reactions by Organocatalysis
作者:Pernille H. Poulsen、Stefania Vergura、Alicia Monleón、Danny Kaare Bech Jørgensen、Karl Anker Jørgensen
DOI:10.1021/jacs.6b03546
日期:2016.5.25
The regio- and stereoselective control of cycloaddition reactions to polyconjugated systems has been demonstrated by applying asymmetric organocatalysis. Reaction of 2,4-dienals with nitrones allows for a highly regio- and stereoselective 1,3-dipolarcycloaddition in the presence of an aminocatalyst. The first cycloaddition on the remote olefin can be followed either by a cascade reaction or by other
metal-free approach for the ʟ-proline mediated synthesis of nitrones from nitrosobenzene and benzaldehydes has been established. The reaction undergoes very efficiently at room temperature in methanol as a solvent. The reaction is assumed to involve that the initial formation of azomethine ylide and [2 + 3] cycloaddition of nitrosobenzene, followed by the subsequent retro [2 + 3] cycloaddition could offer
of a chiral C2-symmetric bis(oxazoline) ligand, its Lewis acid complexes-catalyzed asymmetric 1,3-dipolarcycloaddition reactions of nitrones with electron-deficient dipolarophiles, 3-(2-alkenoyl)-1,3-oxazolidin-2-ones, have been investigated and it was found that the cycloadditions using a Cu(II)-bis(oxazoline) complex under optimized reaction conditions induced extremely high enantioselectivity.