易于获取和易于修改的Ru基催化剂,用于高效和Z选择性的环开元化聚合和环开/交叉元化
R Kashif M Khan1, Sebastian Torker, Amir H Hoveyda
1Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States.
Journal of the American Chemical Society
|July 5, 2013
概括
带有dithiolate连接体的新型鲁催化剂使得高度Z选择性的烯转化成为可能. 这些高效的催化剂在温和条件下运行,负载较低,为复杂的化学转化提供了更简单的路线.
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.
- 聚合物科学 聚合物科学
背景情况:
- 奥莱芬转化是一种强大的碳-碳键形成反应.
- 在转化过程中实现高Z选择性仍然是一个重大挑战.
- 基于的催化剂被广泛使用,但往往缺乏精确的立体化学控制.
研究的目的:
- 开发基于的新型催化剂,用于高效的Z选择性氨酸转化.
- 研究这些催化剂在环开放转化聚合 (ROMP) 和环开放/交叉转化 (ROCM) 中的性能.
- 阐明有助于催化剂性能的结构和机械特征.
主要方法:
- 从商业前体合成新的Ru-dithiolate复合物.
- 在ROMP和ROCM反应中评估催化剂效率和Z选择性.
- 使用X射线衍射和密度函数理论 (DFT) 计算进行表征.
主要成果:
- 在68-82%的收益率的Ru-dithiolate催化剂的单步合成.
- 在温和的条件下 (22°C) 实现了异常的Z选择性 (93:7到>98:2 Z:E).
- 具有较高的催化活性,具有较低的催化剂负载 (0.002 mol %) 和高的周转率 (高达43,000).
结论:
- 合理设计的Ru-dithiolate催化剂提供了高效和高度选择性的Z-olefin转基因.
- 这些催化剂提供操作简单性和高活性,无需严格的基板净化.
- DFT和X射线数据提供了关于催化剂设计和机制的见解.
相关概念视频
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
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...
Base-Catalyzed Ring-Opening of Epoxides
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Ziegler–Natta Chain-Growth Polymerization: Overview
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...
Acid-Catalyzed Ring-Opening of Epoxides
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...


