5-内触发激进循环:不利或有利的过程?
Chryssostomos Chatgilialoglu1, Carla Ferreri, Maurizio Guerra
1ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy. chrys@area.bo.cnr.it
Journal of the American Chemical Society
|September 5, 2002
概括
形成五个环的激进循环化在动力学上比四个环更受青,挑战了德温-贝克威特规则. 这项研究量化了5-endo-trig循环速率和激活能量.
科学领域:
- 有机化学 有机化学
- 反应机制 反应机制
- 计算化学计算化学
背景情况:
- 德温-贝克威特规则将某些激进循环,如5-endo-trig,归类为不受欢迎的.
- 对于合成有机化学来说,了解激素循环化机制至关重要.
研究的目的:
- 为了研究5-endo-trig激素循环的动力学和热力学.
- 通过计算探索影响5endo和4exo循环模式之间的选择性因素.
- 重新评估波德温-贝克威特规则对激进循环的概括.
主要方法:
- 确定激素循环化与抽象的相对动力学数据.
- 使用UB3LYP/6-31G理论水平的计算研究.
- 分析过渡状态结构和搬迁效应.
主要成果:
- 这种5-endo-trig循环的速率常数为2 x 10{\displaystyle 2x10{\displaystyle 2x10{\displaystyle 4}{\displaystyle 4}{\displaystyle 4}{\displaystyle 4}{\displaystyle 1}) 在298K,激活能量为9kcal/mol.
- 由于没有固体效应,5-endo循环化在动力学和热力学上比4-exo循环化更受青.
- 移除基电子的替代物可以使4-exo路径在动力学上具有竞争力.
结论:
- 5-内分触发基循环并不是普遍不受欢迎的,并且可以在动力学上被优先考虑.
- 这些发现需要修订关于这些特定循环的德温-贝克威特规则.
- 计算和实验数据为控制激进循环选择性提供了洞察力.
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