- Fluorinated organocatalysts for the enantioselective epoxidation of enals: Molecular preorganisation by the fluorine-iminium ion Gauche effect
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The fluorine-iminium ion gauche effect is triggered upon union of a secondary β-fluoroamine and an α,β-unsaturated aldehyde, providing a useful strategy for controlling the molecular topology of intermediates that are central to organocatalytic processes. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes. A process of structural editing has revealed that the efficiency of this catalyst is due to the (fluorodiphenyl)methyl group when it is embedded in a β-fluoroiminium motif. Epoxidations of challenging cyclic α,β-disubstituted, β,β-disubstituted and α,β,β-trisubstituted enals catalysed by 1 proceed with excellent levels of enantiocontrol (up to 98 % ee). Fluorine finesse. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes (see scheme). Application of this catalyst to challenging cyclic α,β-disubstituted enals, β,β-disubstituted enals, and an α,β,β-trisubstituted enal proceeds in a highly enantioselective fashion (up to 98 % ee). Copyright
- Tanzer, Eva-Maria,Zimmer, Lucie E.,Schweizer, W. Bernd,Gilmour, Ryan
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supporting information
p. 11334 - 11342,9
(2020/08/31)
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- A Practical Enantioselective Synthesis of α,α-Diaryl-2-pyrrolidinemethanol. Preparation and Chemistry of the Corresponding Oxazaborolidines
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A practical two-step enantioselective synthesis of α,α-diaryl-2-pyrrolidinemethanols (1) from proline, based on the addition of aryl Grignard reagents to proline-N-carboxanhydride (3), is reported.An investigation into the chemistry of the corresponding B-alkyl- and B-aryloxazaborolidines (2) led to the development of a reliable procedure for their preparation.
- Mathre, David J.,Jones, Todd K.,Xavier, Lyndon C.,Blacklock, Thomas J.,Reamer, Robert A.,et al.
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p. 751 - 762
(2007/10/02)
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