在原子转移中的现场催化剂修改与鲁基复合物的激进反应
Juneyoung Lee1, Jessica M Grandner2, Keary M Engle1
1Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Journal of the American Chemical Society
|May 18, 2016
概括
甲基复合物转化为原子转移激素 (ATR) 反应的新活性物种. 这种在位生成的种,而不是原来的复合物,催化了ATR反应,如ATRP和ATRA.
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.
- 聚合物化学 聚合物化学
背景情况:
- 鲁基烯复合物是已建立的氨酸转化催化剂.
- 这些复合物还在原子转移基 (ATR) 反应中表现出活性,包括原子转移基加法 (ATRA) 和原子转移基聚合 (ATRP).
- 在ATR反应中,甲复合物的催化机制尚不清楚,不像它们研究得很好的氨酸转化机制.
研究的目的:
- 研究基化复合物催化ATR反应的机制.
- 为了确定负责ATR反应的活跃催化物种.
- 为了比较各种甲复合物的ATR活性.
主要方法:
- 使用1HNMR光谱的动态研究来监测反应进展和物种转变.
- 分析了七种不同的基化复合物.
- 机械和计算研究,包括1H,13C和31PNMR光谱学和X射线晶体学.
主要成果:
- 在ATRA条件下,基烯复合物迅速转化为新的,转化无活性的物种.
- 甲复合物的预激活增强了ATRA中的动力反应能力,即使在低温下也是如此.
- 只有易于转化为ATRA活性物种的复合物有效催化ATRP;其他人更喜欢氧化还原启动的聚合.
- 在ATR反应中,活性催化剂是局部形成的转化无活性物种.
结论:
- 催化ATR反应的活性催化剂是局部生成的,转化无活性的物种.
- 这种物种与原来的鲁基烯复合物不同.
- 结构分析表明,活性物种可能是RuxCly(PCy3) z复合体.
相关概念视频
Olefin Metathesis Polymerization: Overview
2.7K
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...
2.7K
Radical Reactivity: Concentration Effects
1.9K
In a radical reaction, the concentration of starting materials governs the selectivity of a radical. For example, the reaction between an alkyl halide and an alkene, in the presence of tin hydride and AIBN, begins with the generation of a tin radical. The generated radical then abstracts halogen from the alkyl halide, producing an alkyl radical. This alkyl radical can either react with tin hydride, yielding an alkane, or add to an alkene, generating a nitrile-stabilized radical, eventually...
1.9K
Radical Substitution: Allylic Bromination
6.9K
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
6.9K
Radical Substitution: Hydrogenolysis of Alkyl Halides with Tributyltin Hydride
2.3K
Radical substitution reactions can be used to remove functional groups from molecules. The hydrogenolysis of alkyl halides is one such reaction, where the weak Sn–H bond in tributyltin hydride reacts with alkyl halides to form alkanes. Here, the reagent Bu3SnH yields tributyltin halide as a byproduct.
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...
2.3K
Radical Chain-Growth Polymerization: Overview
3.7K
Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
3.7K
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
4.0K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
4.0K


