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関連する概念動画

Cycloaddition Reactions: Overview01:16

Cycloaddition Reactions: Overview

3.5K
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
3.5K
Turnover Number and Catalytic Efficiency01:19

Turnover Number and Catalytic Efficiency

21.6K
The turnover number of an enzyme is the maximum number of substrate molecules it can transform per unit time. Turnover numbers for most enzymes range from 1 to 1000 molecules per second. Catalase has the known highest turnover number, capable of converting up to 2.8×106 molecules of hydrogen peroxide into water and oxygen per second. Lysozyme has the lowest known turnover number of half a molecule per second.
Chymotrypsin is a pancreatic enzyme that breaks down proteins during digestion....
21.6K
Catalytically Perfect Enzymes01:07

Catalytically Perfect Enzymes

5.1K
The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at high-speed. Their catalytic efficiency values range from 108-109 M-1s-1. These enzymes are also called 'diffusion-controlled' as the only rate-limiting step in the catalysis is that of the substrate diffusion into the active site. Examples include triose phosphate isomerase, fumarase, and superoxide dismutase.
 
Most enzymes...
5.1K
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

2.7K
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.
2.7K
Cycloaddition Reactions: MO Requirements for Thermal Activation01:16

Cycloaddition Reactions: MO Requirements for Thermal Activation

4.5K
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
4.5K
Reduction of Alkenes: Catalytic Hydrogenation02:13

Reduction of Alkenes: Catalytic Hydrogenation

14.1K
Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...
14.1K

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関連する実験動画

Updated: Feb 3, 2026

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
19:58

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Published on: July 30, 2017

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触媒パラジアム-オキシアリルサイクロアディション

Barry M Trost1, Zhongxing Huang2, Ganesh M Murhade2

  • 1Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA. bmtrost@stanford.edu.

Science (New York, N.Y.)
|November 3, 2018
PubMed
まとめ
この要約は機械生成です。

研究者は,Pd-オキシアリル中間体を使用して,新しいパラジウム触媒 (3+2) サイクロアディションを開発した. この方法は,伝統的なオキシアリルカチオン化学の限界を克服して,多様なテトラヒドロフーラン骨格を効率的に合成します.

さらに関連する動画

Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination
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Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

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Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles
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Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

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関連する実験動画

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Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
19:58

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

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Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination
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Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

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Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles
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Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

Published on: June 25, 2018

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科学分野:

  • 有機合成
  • カタリシス
  • 薬剤化学

背景:

  • 化学選択的なサイクル添加反応は,有機合成における複雑なリングシステムの構築に不可欠である.
  • オキシアリルカチオンは典型的には (4+3) サイクロアディションを経験し,五つ組のリングを形成する際の有用性を制限する.
  • 五肢骨格へのアクセスのための 新しい合成経路の開発は 重要な課題です

研究 の 目的:

  • 5つ組のリングシステムを合成するための新しいサイクロアディション反応を探求する.
  • オキシアリルカチオン化学におけるパラジウム触媒の使用を調査する.
  • テトラヒドロフーラン骨格に (3+2) サイクル添加経路でアクセスする方法を開発する.

主な方法:

  • Pd(0) 触媒を用いて,適した前駆体からパラジアム-オキシアリル中間物質を生成する.
  • Pd-オキシアリル中間体と結合ダイエンの反応 (3+2) サイクル添加.
  • その後,テトラヒドロフラン添加物をサイクロペンタノンにパラジウム触媒で変換する.

主要な成果:

  • 多様なテトラヒドロフラン骨格を生成する新しいPd触媒 (3+2) サイクル添加反応が達成された.
  • 反応は,Pd-アリル移転と環閉を伴う段階的な経路で進行し,従来の (4+3) 選択性を優先する.
  • 合成したヘテロサイクルは,容易にカルボサイクルのサイクロペンタノンに変換できます.

結論:

  • この研究は,パラジウム触媒を用いた5つの環へのアクセスのための新しい戦略を提示しています.
  • 開発された方法は,置換されたテトラヒドロフーランとサイクロペンタノンのための汎用的な経路を提供します.
  • このアプローチは,有機化学におけるオキシアリル中間物の合成的有用性を拡大する.