An orbital phase theory for the torquoselectivity of the ring-opening reactions of 3-substituted cyclobutenes: geminal bond participation.
An orbital phase theory for the torquoselectivity of the ring-opening reactions of 3-substituted cyclobutenes: geminal bond participation.
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DOI：
10.1021/jo049081y
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
Mikihito Yasui;Y. Naruse;S. Inagaki
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文献类型：
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作者：
Mikihito Yasui;Y. Naruse;S. Inagaki
我们将轨道相理论应用于 3-取代 (X) 环丁烯电环反应的扭矩选择性。结果表明，扭矩选择性受反应 pi(CC) 和 sigma(CC) 键的轨道相位关系控制，其中 sigma(CX) 键与要裂解的 sigma(CC) 键成对。从轨道相理论推导了供电子西格玛(CX)键的向内旋转和吸电子西格玛(CX)键的向外旋转。扭矩选择性和 sigma(CX) 轨道能量之间的相关性证实了 sigma(CX) 键的给电子能力增强了向内旋转。孪生 sigma(CX) (sigma(CH)) 和 sigma(CC) 键之间的轨道重叠也很重要。具有低位未占据 pi 轨道的不饱和取代基也促进向内旋转。
We apply an orbital phase theory to the torquoselectivity of the electrocyclic reactions of 3-substituted (X) cyclobutenes. The torquoselectivity is shown to be controlled by the orbital-phase relation of the reacting pi(CC) and sigma(CC) bonds with the sigma(CX) bond geminal to the sigma(CC) bond to be cleaved. The inward rotation of electron-donating sigma(CX) bonds and outward rotation of electron-withdrawing sigma(CX) bonds have been deduced from the orbital-phase theory. Enhancement of the inward rotation by the electron-donating capability of the sigma(CX) bonds is confirmed by the correlation between the torquoselectivity and sigma(CX) orbital energy. The orbital overlaps between the geminal sigma(CX) (sigma(CH)) and sigma(CC) bonds are found to be important as well. Unsaturated substituents with low-lying unoccupied pi orbitals also promote the inward rotation.