ニトロ置換されたホヴェイダ・グラブスルテニウムカルベン:電子活性化による触媒活性強化
Anna Michrowska1, Robert Bujok, Syuzanna Harutyunyan
1Institutes of Organic Chemistry and Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland.
Journal of the American Chemical Society
|July 30, 2004
まとめ
窒素置換されたホヴェイダ・グラブス触媒は,軽度な条件下で様々な転移反応において高い活性と安定性を示しています. しかし,ステリック活性化と電子活性化を組み合わせると安定性が低下し,すべての用途に最適な単一の触媒はないことを示しています.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
背景:
- Hoveyda-Grubbsの触媒は,オレフィンメタテシスで広く使用されています.
- より活発で安定した触媒の開発は,合成化学にとって極めて重要です.
研究 の 目的:
- 設計,合成,および,窒素置換されたホヴェイダ-グラブス転化触媒の評価を行う.
- 電子およびステリック活性化が触媒性能に与える影響を調査する.
主な方法:
- 新種の窒素置換されたホヴェイダ-グラブス複合体の合成.
- 様々なメタテシス反応 (RCM,CM,enyneメタテシス) での触媒の安定性と活性度の評価.
- 既存のGrubbsとHoveydaの触媒との比較.
主要な成果:
- メタおよびパラ置換のニトロ・ホヴェイダ・グラブス触媒は,軽度な条件下で高い活性と安定性を示す.
- これらの触媒は,第2世代のグラブスおよびホヴェイダのフォスフィンフリー触媒よりも活性です.
- 電子 (ニトログループ) とステリック活性化の組み合わせにより,触媒の安定性が著しく低下します.
- フォスフィンフリーカルベンは,電子欠乏基板の交叉メタテシスに優れているが,テトラ置換された二重結合には効果が低い.
結論:
- 窒素置換されたホヴェイダ-グラブス触媒は,特定のメタテシスアプリケーションに実用的な利点を提供します.
- 触媒の最適化はアプリケーションに依存しており,単一の触媒が普遍的に優れているわけではありません.
- ルテニウム触媒の選択は,特定の合成変換に合わせて調整する必要があります.
関連する概念動画
Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Acid Halides to Alcohols: Grignard Reaction
Organomagnesium halides, commonly known as Grignard reagents, convert acid halides to tertiary alcohols. The reaction requires two equivalents of the Grignard reagent and proceeds via a ketone intermediate.
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs,...
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs,...
Preparation of Carboxylic Acids: Carboxylation of Grignard Reagents
Carboxylic acids can be prepared by the carboxylation of Grignard reagents (RMgX). This method is convenient for converting alkyl (primary, secondary or tertiary), vinyl, benzyl, and aryl halides to carboxylic acids with one additional carbon than the starting RMgX.
Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...

![Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F55858.jpg&w=3840&q=50)
