一个结构-活性研究的Ni-催化基-基Kumada合. 改进的催化剂用于合二次基化物
Peng Ren1, Oleg Vechorkin, Kim von Allmen
1Laboratory of Inorganic Synthesis and Catalysis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), ISIC-LSCI, BCH 3305, Lausanne, CH 1015, Switzerland.
Journal of the American Chemical Society
|April 20, 2011
概括
新的催化剂显著改善了-Kumada型交叉合反应,特别是对于二次化. 连接物解离增强了这种重要的有机合成方法中的催化剂活性和效率.
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:
- 库马达型交叉合反应对于C-C键的形成至关重要.
- 催化为提供了一种成本效益高的替代品.
- 开发高效的催化剂,用于具有挑战性的基质,如二次基化物仍然是一个关键目标.
研究的目的:
- 进行 (II) 复合物的结构-活性研究,用于-Kumada型交叉合.
- 合成和表征新的 (II) 复合物,具有多样化的联体环境.
- 为了确定高活性和高效的预催化剂,用于合非活性基化物.
主要方法:
- 新 (II) 复合物的合成和结构特征与三酸盐 ((R) N ((2) N) 和双酸盐 ((R) NN) 连接体.
- 合成复合物的评价作为前催化剂在Kumada型交叉合反应中,涉及二次酸和酸格里纳德试剂.
- 机理性调查,包括对转移的要求和连接体解离效应的评估.
主要成果:
- 合成了几种具有不同协调几何形状的新 (II) 复合物.
- 该研究确定了特定的催化剂,即[HNN]Ni[PPh3)Cl和[HNN]Ni[2,4-lutidine]Cl,与已知的复合物相比,它们具有更高的活性和效率.
- 从中心的连接物解离 (氨酸和氨酸) 被确定为增强催化性能的关键.
- 确定基化物的激活是通过激进机制进行的.
结论:
- 在前催化剂上的转移部位对于催化是必不可少的.
- 协调几何和旋转状态对催化活性的影响最小.
- 从中心分离的氨酸或氨酸连接物显著提高了基-基交叉合中的催化剂性能.
- 开发的催化剂代表了对二次基化物有效合的重大进步.
相关概念视频
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
01:27Aldol Condensation with β-Diesters: Knoevenagel Condensation
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as β-diesters to produce substituted olefins.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
02:26SN2 Reaction: Transition State
An SN2 reaction of an alkyl halide is a single-step process in which bond formation between the nucleophile and the substrate and bond breaking between the substrate and the halide occurs simultaneously through a transition state without forming an intermediate.
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
When the nucleophile approaches the electrophilic carbon with its lone pairs, the halide acts as a leaving group and moves away with the electron-pair bonded to the carbon. Dotted partial bonds represent the bonds being formed or broken...
02:14SN2 Reaction: Kinetics
Kinetic Studies and Significance
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.
In a chemical reaction, a relationship exists between the concentration of reactants and the rate at which the reaction proceeds. The study to measure this relationship is known as the kinetics of a chemical reaction. Kinetic studies are used to deduce the rate law of a chemical reaction, which provides information about the species involved during the transition state of the rate-determining step. Thus, kinetic studies help to derive the mechanism of a reaction.