形态异构化作为确定对反应途径选择性的过程:通过Cis Alkene中间体在链中行走的基旋转的影响
Kazuma Muto1, Miho Hatanaka1, Fumitoshi Kakiuchi1
1Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan.
旋,一种构造性异构化,决定了催化链路行走反应的选择性. 这一过程比典型的结合形成或结合裂变步骤具有更高的能量障碍,影响反应途径.
科学领域:
- 有机化学 有机化学
- 有机金属化学 有机金属化学
- 计算化学计算化学
背景情况:
- 键形成和键裂解反应通常是有机合成的关键.
- 形态异构化通常被忽视为选择性决定因素.
- 催化基异构化,或链路行走,是一个重要的合成工具.
研究的目的:
- 为了研究构造性异构化在确定催化链路行走反应的选择性中的作用.
- 为了确定基化异构化中的速度决定性步骤.
- 阐明链行走的机制,特别是关于基中间体.
主要方法:
- 理论计算 (例如,密度函数理论) 来建模反应路径和过渡状态.
- 实验性研究用于验证理论预测和观察反应结果.
- 分析各种步骤的能量障碍,包括基旋转,β-化物消除和迁移插入.
主要成果:
- 基旋转被确定为一些基合物异构化事件中最高的能量屏障过渡状态.
- 对于β-化物消除和迁移插入的过渡状态并没有通过计算观察到.
- 理论和实验证据都表明,由于旋转障碍,链行走有利于 cis 基中间体而不是 trans 基中间体.
结论:
- 形态异构化,特别是螺旋式的旋,可以是有机反应中选择性决定的步骤.
- 链行走的机制涉及 cis 基中间体由于基旋转的能量成本.
- 这一发现挑战了传统的看法,认为键形成/裂变过程在反应选择性上是唯一占主导地位的.
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