((t) Bu2bpy) Pd(Me) 2:パラジウム(IV) の中介物質から酸化誘導による還元性除去は,一電子酸化反応における中介物質である
Michael P Lanci1, Matthew S Remy, Werner Kaminsky
1Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
Journal of the American Chemical Society
|October 15, 2009
まとめ
この研究では,パラジウム複合体が酸化によって炭素-炭素結合を形成する方法を調査しています. 異なる酸化物質は,パラジウム中間物質を含む異なる反応経路を示し,C−C結合形成機構に影響を与えます.
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
- 反応メカニズム 反応メカニズム
背景:
- パラジウム複合体は,触媒作用において極めて重要です.
- 酸化C-C結合形成を理解することは,合成効率の鍵です.
- Pd (II) 前駆体からの還元性除去のメカニズムは,さらなる解明を必要としています.
研究 の 目的:
- 特定のパラジウム複合体から酸化誘発C-C結合形成の還元性除去のメカニズムを調査する.
- 反応経路を異なる外界の酸化物質と比較する.
- 関連するパラジウム中間物の酸化状態を特定するために.
主な方法:
- 様々な酸化物質を用いて, ((t) Bu (((2) bpy) Pd ((II) (((Me) ((2) から還元性除去を研究した.
- 分析された反応製品と中間物質.
- 運動学的およびスペクトル学的研究を通じて,機械的経路を調査した.
主要な成果:
- フェロセニウム酸化剤は,Pd (III) とPd (IV) の中間物質を含むメカニズムを示唆し,Pd (IV) からC−C結合が形成される.
- Ag (((+) 酸化物質は,Pd-Ag (((+) アドクト経由で発生し,内部球の電子がPd (((III)) に移転する.
- ベンゾキノン酸化剤は,メチルスクランブリングなしに明確な経路を通ってエタンを生成し,Pd(0) 製品を生成します.
結論:
- C-C結合形成の反応経路は酸化物質に依存しています.
- 複数のパラジウム酸化状態 (Pd(0),Pd(II),Pd(III),Pd(IV)) が関与することがあります.
- 異なるメカニズムは,パラジウム複合体からの還元的な除去の結果を決定する.
関連する概念動画
Radical Formation: Elimination
Another method of radical formation is the elimination process. It is the opposite of the addition route and is driven by the instability of the radical. For example, as depicted in Figure 1, dibenzoyl peroxide yields a pair of unstable radicals upon homolysis. Given its instability, this radical spontaneously undergoes elimination via a C–C bond cleavage to form a relatively more stable phenyl radical. The mechanism involves cleavage of the bond between the α and β positions with respect to...
Benzene to 1,4-Cyclohexadiene: Birch Reduction Mechanism
Birch reduction uses solvated electrons as reducing agents. The reaction converts benzene to 1,4-cyclohexadiene. The reaction proceeds by the transfer of a single electron to the ring to form a benzene radical anion. This anion is highly basic—it abstracts a proton from the alcohol to form a cyclohexadienyl radical. Another single electron transfer gives the cyclohexadienyl anion. A proton transfer from the alcohol forms 1,4-cyclohexadiene. Since this reduction occurs via radical anion...
Regioselectivity of Electrophilic Additions-Peroxide Effect
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
Radical Substitution: Hydrogenolysis of Alkyl Halides with Tributyltin Hydride
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,...
Reactions at the Benzylic Position: Oxidation and Reduction
The benzylic position describes the position of a carbon atom attached directly to a benzene ring. Benzene by itself does not undergo oxidation. In contrast, the benzylic carbon is quite reactive in the presence of strong oxidizing agents such as KMnO4 or H2CrO4. Therefore, alkylbenzenes are readily oxidized to benzoic acid, irrespective of the type of alkyl groups.
Elimination Reactions
A nucleophile can react with an alkyl halide to give the substitution product by displacing the halogen. Or it can function as a base to give the elimination product by deprotonation of the neighboring carbon to form an alkene. In an elimination reaction, the substrate loses two groups from adjacent carbons forming at least one π bond. The carbon attached to the halogen is called the α carbon, while the adjacent carbon is called the β carbon; hence, these reactions are called β elimination or...
![Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F51444.jpg&w=3840&q=50)
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=50)
