Ni触媒によるアルキル-アルキルクマダ結合の構造活動研究. 二次アルキルハリドの結合のための改良された触媒
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
まとめ
新しいニッケル触媒は,アルキル-アルキルクマダ型クロスカップリング反応を,特に二次アルキルハリドの反応を大幅に改善します. リガンド解離は,この重要な有機合成方法における触媒の活性と効率を高めます.
科学分野:
- 有機金属化学 有機金属化学
- カタリシス カタリシス カタリシス
- オーガニック・シンセシス オーガニック・シンセシス
背景:
- クマダ型クロスカップリング反応は,C−C結合形成に不可欠である.
- ニッケル触媒は,パラジウムに費用対効果の高い代替品を提供します.
- 二次アルキルハリドなどの挑戦的な基板のための効率的な触媒の開発は,依然として重要な目標です.
研究 の 目的:
- アルキル-アルキルクマダ型クロスカップリングのためのニッケル (II) 複合体の構造-活性研究を行う.
- 異なるリガンド環境を持つ新しいニッケル (II) 複合体を合成し,特徴づけること.
- 非活性化アルキルハリドの結合のための高度に活性的で効率的な前触媒を特定する.
主な方法:
- トリデント酸 ((R) N (((2) N) とバイデント酸 ((R) NN) リガンドを含む新しいニッケル (((II) 複合体の合成と構造的特徴付け.
- 二次アルキルヨウ酸化物とアルキルグリナード反応剤を含むクマダ型クロスカップリング反応における前触媒としての合成複合体の評価.
- 伝達要求およびリガンド解離効果の評価を含むメカニズム調査.
主要な成果:
- 異なる協調幾何学を持ついくつかの新しいニッケル (ニッケルII) コンプレックスが合成されました.
- この研究では,特定のニッケル触媒,すなわち[H]NN[Ni]PPh3Cl]と[H]NN[Ni]2,4-ルチジン[Cl]を特定し,既知のピンサー複合体と比較して優れた活性と効率を示した.
- ニッケル中心からのリガンド解離 (フォスフィンとルチジン) は,触媒性能の強化に不可欠であると特定されました.
- アルキルハリドの活性化は,過激なメカニズムを通過することを決定しました.
結論:
- 前触媒の伝達部位は,触媒作用に不可欠である.
- 座標幾何学とスピン状態は,触媒活動に最小限の影響を及ぼします.
- ニッケル中心からのフォスフィンまたはルチジンのリガンドの解離は,アルキル-アルキルクロスカップリングにおける触媒の性能を大幅に高めます.
- 開発されたニッケル触媒は,二次アルキルハリドの効率的な結合のための重要な進歩を表しています.
関連する概念動画
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.