在α-aryl替代的乙烯酸中,西格玛移位与pi共振对比
Thomas Müller1, Dominik Margraf, Yvonne Syha
1Institut für Anorganische und Analytische Chemie der Johann Wolfgang Goethe Universität Frankfurt, Marie Curie-Strasse 11, D 60439 Frankfurt/Main, Federal Republic of Germany. dr.thomas.mueller@chemie.uni-frankfurt.de
Journal of the American Chemical Society
|August 4, 2005
概括
研究人员用基和基组合成和稳定了新的乙烯酸. 这些化合物通过pi-共振和西格玛移位表现出显著的稳定性,NMR和计算研究证实了这一点.
科学领域:
- 有机金属化学 有机金属化学
- 碳化物化学 碳化物化学
- 频谱学是一种光谱学.
背景情况:
- 乙烯酸是有机合成中至关重要的反应性中间体.
- 乙烯酸的稳定是控制其反应性的关键,并使其能够被隔离.
- 基组和基替代剂在乙烯酸阴离子稳定中的作用需要进一步阐明.
研究的目的:
- 为了合成和表征新的α-aryl,β,β'-disilyl替代的乙烯酸.
- 研究稳定机制,包括皮共振和西格玛移位.
- 探索替代物的电子效应与阴离子稳定性之间的关系.
主要方法:
- 合成和分离使用四基{pentafluorophenyl) 酸对抗离子的乙烯酸.
- 通过核磁共振 (NMR) 光谱学 (13C, 29Si) 进行表征.
- 密度函数理论 (DFT) 计算 (B3LYP/6-311G(2d,p)//B3LYP/6-31G(d)) 用于结构和电子分析.
- 取决于温度的29Si NMR光谱法来确定稳定性.
- 合常数和化学转移的哈梅特式分析.
主要成果:
- 成功合成和分离了12个在室温下稳定的乙烯酸 (1b-l,7和8).
- 核磁共振化学转移和J合数据证实了通过pi共振 (基) 和西格玛移位 (β-基) 的显著稳定.
- 量化了 Ferrocenyl 替代乙烯基的稳定自由 (DeltaG++ = 48.9 +/- 4.2 kJ mol(-1)).
- 哈梅特分析揭示了Si-C超结合和基组的pi捐赠之间的反向关系.
- DFT计算提供了对超和共振的结构后果的见解,尽管键的长度并不完全反映替代效应.
结论:
- 具有结合和替代物的新型乙烯酸是可访问和稳定的.
- 皮共振和西格玛移位都对乙烯基离子稳定有显著的贡献.
- 这些稳定模式之间的相互作用是复杂的,并受到替代电子特性的影响.
- 这项研究为稳定碳酸的基本化学提供了宝贵的见解.
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