SmI<sub>2</sub>-Promoted Radical Addition of Nitrones to α,β-Unsaturated Amides and Esters: Synthesis of γ-Amino Acids via a Nitrogen Equivalent to the Ketyl Radical
作者:Ditte Riber、Troels Skrydstrup
DOI:10.1021/ol027386y
日期:2003.1.1
[reaction: see text] Alkyl nitrones undergo radical addition reactions to a series of alpha,beta-unsaturated amides and esters when subjected to samarium diiodide via a nitrogen equivalent to a ketyl radical anion. This reaction conveniently provides access to a variety of functionalized gamma-amino acids. The methodology was extended to the asymmetric synthesis of 4-substituted gamma-amino acids,
The scope and potential of the reaction have been investigated and developed. The reaction can also be catalyzed by secondaryamines. The use of chiral cyclic amines, such as L-proline leads to optically active beta-hydroxynitrones in moderate yield and with moderate to high enantiomeric excess. The reaction mechanism was studied by kinetic measurements, intermediate and product analysis, and determination
Trimethylsilyl trifluoromethanesulfonate-promoted cycloaddition of nitrones with silyl enol ethers: synthesis and reactivity of 5-siloxyisoxazohdines
作者:Chiara Camiletti、Dilip D. Dhavale、Luca Gentiluccia、Claudio Trombini
DOI:10.1039/p19930003157
日期:——
In the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf), the reaction of nitrones with silyl enolethers affords 5-siloxyisoxazolidines under mild conditions, in good to excellent yields. 5-Siloxyisoxazolidines can undergo chemoselective reductions to Manoich bases or N-hydroxy-1,3-amino alcohols, and, in the presence of TMSOTf, react with silylated carbon nucleophiles at the acetalic
Trimethylsilyl trifluoromethanesulfonate promoted [3 + 2] dipolar cycloaddition of nitrones and silyl enol ethers: an efficient route to 5-siloxyisoxazolidines
作者:Dilip D. Dhavale、Claudio Trombini
DOI:10.1039/c39920001268
日期:——
The reaction of silyl enolethers and nitrones, in the presence of trimethylsilyl trifluoromethanesulfonate, gives 5-siloxyisoxazolidines in excellent yield under fairly mild conditions.
photocatalytic aerobic oxidative dehydrogenation reactions of N,N-disubstituted hydroxylamines to nitrones were developed with an in situ generated photocatalyst based on commercially available 3,6-dichlorotetrazine. This process affords a wide range of nitrones in high yields under mild conditions. In addition, an oxidative (3+3) cycloaddition between an oxyallyl cation precursor and a hydroxylamine was also developed