结构证据表明,基替代剂在六个环的二氧化碳离子中采用电子偏好的伪轴方向
Stephen Chamberland1, Joseph W Ziller, K A Woerpel
1Department of Chemistry, University of California, Irvine, California 92697-2025, USA.
Journal of the American Chemical Society
|April 14, 2005
概括
在四二烯酸乙上,远程替代剂会影响核替代选择性. 基团有利于氧碳离子中间体中的伪轴形状,影响反应结果.
科学领域:
- 有机化学 有机化学
- 碳水化合物化学 碳水化合物化学
- 计算化学计算化学
背景情况:
- 核替代反应是有机合成的基础.
- 甲基烯酸乙是糖化反应中的关键中间体.
- 介质的符合性偏好显著影响反应选择性.
研究的目的:
- 调查远程C-4替代剂对四烯酸乙烯的核友替代反应选择性的影响.
- 为了阐明氧化碳离子中间体在糖化中的构造偏好.
- 为观察到的形状偏好提供理论和实验证据.
主要方法:
- 核性替代反应与单替代的四烯酸乙.
- 对反应中间体的计算研究.
- 光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).光谱分析 (NMR,IR).
- 类似的二氧化碳离子的X射线晶体学.
主要成果:
- 在基于远程C-4基或基替代剂的核替代反应中观察到相反的选择性.
- 基替代的四烯酸乙有利于氧碳离子中间体的伪轴形状.
- 理论,光谱和晶体学数据支持对基替代剂的形状偏好.
结论:
- 远程醇基替代剂直接使氧碳离子中间体采用伪轴形状.
- 这种形状偏好解释了核友置换反应中观察到的相反的选择性.
- 在缺乏电子的六个环中,电子负替代物的电子偏好的伪轴定向驱动了这种对比偏好.
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