对紫外线辅助 [4 + 2] 循环添加的机制研究在合成努力中对vibsanin E进行了辅助
Joachim Nikolai1, Øystein Loe, Paulina M Dominiak
1Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA.
Journal of the American Chemical Society
|August 19, 2007
概括
这项研究揭示了光化学循环添加中不寻常的立体选择性. 计算显示 cis-trans 异体化,其次是 Diels-Alder 反应,解释了观察到的产物分布.
科学领域:
- 摄影化学的使用.
- 有机化学 有机化学
- 量子化学 是一个量子化学.
背景情况:
- 光化学循环添加是重要的合成反应.
- 了解反应机制,包括立体选择性,至关重要.
- 边界分子轨道 (FMO) 理论经常预测立体化学结果.
研究的目的:
- 为了研究因子9与二烯的光化学循环添加的立体化学过程.
- 为了合理化观察到的,意想不到的立体选择性.
- 为了阐明底层反应机制.
主要方法:
- 量子化学密度功能理论 (DFT) 的计算.
- 使用了B3LYP/6-31G的理论水平.
- 分析了反应途径和中间体.
主要成果:
- 观察到的立体选择性与标准的FMO预测相矛盾.
- 计算支持了一种涉及光化学 cis-trans 异构化的机制,该机制是将 9 enone 转化为 9a 转化异构体.
- 随后的热Diels-Alder反应的diene与transenone解释了产品的分布.
- 在光化学步骤中,选择性地形成了一个扭曲的三重中间体.
结论:
- 不寻常的立体选择性是通过两步的光化学和热过程合理化.
- 扭曲的三联中间体的形成是观察到的选择性的关键.
- DFT计算为复杂的光化学反应提供了宝贵的见解.
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