Fe ((+)) によって触媒化されたノルボナディエンとノルボネンのレトロサイクルに関する密度関数学的研究
1Department of Chemistry, Auburn University, Auburn, Alabama 36849, USA.
Journal of the American Chemical Society
|September 20, 2001
まとめ
Fe(+) 触媒は,ノルボナディエン (NBD) とノルボネン (NBN) のディエルス・アルダー反射反応を促進し,活性化バリアを下げます. この研究は,これらの有機金属複合体の反応経路と中間物質を詳細に説明しています.
科学分野:
- 有機金属化学 有機金属化学
- コンピューティング・ケミストリー
- 反応メカニズム 反応メカニズム
背景:
- レトロディエルス・アルダー反応は,基本的な有機変異である.
- 鉄触媒は,反応経路と運動学に影響することが知られている.
- 反応メカニズムの理解は,触媒設計と合成アプリケーションにおいて極めて重要です.
研究 の 目的:
- ノルボナディエン (NBD) と ノルボネン (NBN) のディエルス・アルダー反射における Fe (((+) の触媒効果を調査する.
- 段階的な対協調された経路と中間形成を含む反応機構を明らかにする.
- 関連鉄炭素複合体の電子特性と反応性を比較する.
主な方法:
- 反応経路をモデル化するために,密度関数理論 (DFT) の計算を用いた.
- 触媒反応と非触媒反応の両方の活性化バリアと移行状態が決定されました.
- 潜在エネルギー表面を分析し,低エネルギー反応チャネルと中間物質を特定しました.
主要な成果:
- Fe(+) 触媒は,協調した経路と比較して,NBDの段階的なレトロダイエルス-アルダーの活性化バリアを3.1 kcal/mol低下させます.
- NBNの場合,Fe (((+)) 誘導の段階反応は,非誘導の段階反応よりも低いバリアを持つが,協調された経路よりも高い.
- 主要な中間物質であるC(5) H(6) FeC(2) H(2) +) とC(5) H(6) FeC(2) H(4) +) は,容易に水素を移動させ,安定したサイクロペンタディエン-鉄複合体を形成する.
- NBDとNBNの中間物質の最も低いエネルギーの経路には,単一の四重奏の多重性が含まれます.
結論:
- Fe (((+) は,NBDとNBNのディエルズ-アルダー反射機構を大幅に変化させ,特定の条件下で段階的な経路を好む.
- この研究は,特定の中間物質を通じてこれらの変換を媒介する鉄の役割についての洞察を提供します.
- C ((2) H ((2)) とC ((2) H ((4)) 複合体をCpFe (((+)) とC ((5) H ((6) Fe ((+)) と比較すると,電子構造と反応性の違いが明らかになる.
関連する概念動画
Structure of Conjugated Dienes
Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
Diels–Alder Reaction: Characteristics of Dienes
The Diels–Alder reaction brings together a diene and a dienophile to form a six-membered ring. Both components have unique characteristics that influence the rate of the reaction.
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable, the...
Stability of Conjugated Dienes
Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Diels–Alder Reaction: Characteristics of Dienophiles
In a Diels–Alder reaction, the diene is usually an electron-rich system and acts as a nucleophile, whereas the dienophile is electron-deficient and functions as an electrophile. Much like the diene, the nature of the dienophile significantly impacts the outcome of the reaction.
Characteristics of Dienophiles
Generally, the best dienophiles are alkenes containing electron-withdrawing substituents such as carbonyl, nitrile, and nitro groups. The feasibility of a Diels–Alder reaction depends on...
Characteristics of Dienophiles
Generally, the best dienophiles are alkenes containing electron-withdrawing substituents such as carbonyl, nitrile, and nitro groups. The feasibility of a Diels–Alder reaction depends on...


