用化Ru催化剂进行olefin转化中的Z-选择性:对机制和选择性的计算研究
Peng Liu1, Xiufang Xu, Xiaofei Dong
1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA.
Journal of the American Chemical Society
|January 11, 2012
概括
化催化剂通过将烯向侧面导向而促进Z选择性烯转化,与未化催化剂不同. 与N-异环碳联体的固体相互作用有利于Z-异构体的形成.
科学领域:
- 有机金属化学 有机金属化学
- 催化剂是一种催化剂.
- 有机合成 有机合成
背景情况:
- 奥莱芬转化是有机合成中的重要反应.
- 实现高立体选择性,特别是Z选择性,仍然是一个挑战.
- (Ru) 催化剂被广泛使用,但它们的选择性机制需要进一步阐明.
研究的目的:
- 为了研究Z-选择性在由化复合体催化的olefin转化反应的起源.
- 阐明控制立体化学结果的机械路径.
- 了解N-异环碳素 (NHC) 配体在指导选择性中的作用.
主要方法:
- 密度函数理论 (DFT) 的计算被用来建模催化循环.
- 计算分析侧重于olefin的接近轨迹和过渡状态.
- 分析了基质和催化剂之间的固体相互作用.
主要成果:
- 化Ru催化剂有利于从"侧面"位置的olefin方法,与未化催化剂的"底部"路径不同.
- 在氨酸替代剂和NHC连接体的N替代剂之间发现了显著的固体排斥.
- 发现这些固态因素是观察到的高Z选择性的主要驱动因素.
结论:
- 化Ru催化剂中独特的"侧面"接近途径负责Z选择性.
- N-异环碳联体的设计,特别是N-替代剂,对于控制立体化学是至关重要的.
- 这项研究为设计更有选择性的氨酸转化催化剂提供了机制的理解.
相关概念视频
Olefin Metathesis Polymerization: Overview
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
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A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.


