Mechanism of the Enantioselective Intramolecular [2+2] Photocycloaddition Reaction of Coumarin Catalyzed by a Chiral Lewis Acid: Comparison with Enone Substrates
Mechanism of the Enantioselective Intramolecular [2+2] Photocycloaddition Reaction of Coumarin Catalyzed by a Chiral Lewis Acid: Comparison with Enone Substrates
复制标题
手性路易斯酸催化香豆素对映选择性分子内[2 2]光环加成反应机理：与烯酮底物的比较
DOI：
10.1021/acs.joc.6b00980
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发表时间：
2016
影响因子：
3.6
通讯作者：
Chen Xuebo
中科院分区：
文献类型：
--
作者：
Wang Hongjuan;Fang Wei-Hai;Chen Xuebo
分子内烯酮[2+2]光环加成反应的不对称催化依赖于复杂的调节机制来控制其反应活性、选择性和量子产率。能量相容相对论赝势的多组态微扰理论提供了具有代表性的香豆素和烯酮底物之间的机理比较。一对明亮的ππ*态通过单重态超表面上的直接环加成和三重态流形中由于反El Sayed型单重态-三重态的存在而消除反应通道来控制自由香豆素的非选择性背景反应.三重态反应通道的打开依赖于相对论效应的存在，即手性Lewis酸催化剂中重原子引起的自旋-轨道耦合。
The asymmetric catalysis of the intramolecular enone [2 + 2] photocycloaddition reaction relies on a complicated regulation mechanism to control its reactivity and selectivity as well as quantum yield. The multiconfiguration perturbation theory associated with energy-consistent relativistic pseudopotentials offers a mechanistic comparison between representative coumarin and enone substrates. A pair of bright ππ* states govern the unselective background reaction of the free coumarin through the direct cycloaddition in the singlet hypersurface and the elimination of the reaction channel in the triplet manifold due to the existence of anti El Sayed type singlet–triplet crossing. The opening of a reaction channel in the triplet state is repeatedly verified to depend on the presence of relativistic effects, i.e., spin–orbit coupling due to heavy atoms in the chiral Lewis acid catalyst.