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首页> 外文期刊>Chemistry: A European journal >Quaternary chiral β~(2,2)-amino acids with pyridinium and imidazolium substituents
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Quaternary chiral β~(2,2)-amino acids with pyridinium and imidazolium substituents

机译：具有吡啶鎓和咪唑鎓取代基的季手性β〜（2,2）-氨基酸

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摘要

The reactions of cyclic sulfamidates as electrophiles with a variety of nitrogen-containing aromatic heterocycle nucleophiles, such as pyridines, N-alkylimidazoles and N-methylbenzimidazol, was explored. In all cases, although the nucleophilic substitution reactions occurred on quaternary centres, elimination products were not detected. The inversion of configuration at this quaternary centre was determined by X-ray diffraction analysis and the enantiomeric excess of the reactions was checked by chiral HPLC. This synthetic approach allowed us to obtain a new family of chiral charged β2,2-amino acids, including a new bisamino acid that incorporates an imidazolium salt as a cross-linker. In this context, the treatment of these chiral imidazolium salts with Ag_2O opens the way to new chiral N-heterocyclic carbenes, which are important substrates in the fields of organometallic and organocatalytic chemistry. Additionally, we have done a thorough conformational analysis of these β-amino acid derivatives, both in the solid state and in solution. The most important conformational feature of these acyclic systems is the rigidity of the N-CH_2-C- N~+ dihedral angle, which is essentially due to the gauche effect. Chiral β~(2,2)-amino acids: Nitrogen-containing aromatic heterocycles were used as nucleophiles in the opening reaction of cyclic sulfamidates to obtain a new family of chiral β~(2,2)-amino acids with pyridinium and imidazolium substituents, which show a rigid N-CH _2-C-N~+ dihedral angle due to the gauche effect. These chiral imidazolium derivatives open the way to the synthesis of new chiral N-heterocyclic carbenes.
机译：探索了环状氨基磺酸盐作为亲电试剂与各种含氮芳族杂环亲核试剂，如吡啶，N-烷基咪唑和N-甲基苯并咪唑的反应。在所有情况下，尽管亲核取代反应发生在四级中心，但未检测到消除产物。通过X射线衍射分析确定在该四元中心的构型转化，并通过手性HPLC检查反应的对映体过量。这种合成方法使我们能够获得一个新的手性带电β2,2-氨基酸家族，包括一个新的双氨基酸，该氨基酸结合了咪唑鎓盐作为交联剂。在这种情况下，用Ag_2O处理这些手性咪唑鎓盐为新的手性N-杂环卡宾开辟了道路，它们是有机金属和有机催化化学领域的重要底物。此外，我们已经对这些β-氨基酸衍生物在固态和溶液中进行了彻底的构象分析。这些无环体系最重要的构象特征是N-CH_2-C-N〜+二面角的刚度，这主要是由于网状效应造成的。手性β〜（2,2）-氨基酸：在环氨基磺酸盐的开放反应中，使用含氮芳族杂环作为亲核试剂，以获得具有吡啶鎓和咪唑鎓取代基的新的手性β〜（2,2）-氨基酸家族，由于薄纱效应，显示出刚性的N-CH _2-CN〜+二面角。这些手性咪唑鎓衍生物为合成新的手性N-杂环卡宾开辟了道路。

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