ルテニウム (((II) 触媒による選択的分子内 [2 + 2 + 2]アルキンサイクロトリメリゼーション
Yoshihiko Yamamoto1, Takayasu Arakawa, Ryuji Ogawa
1Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan. yamamoto@apchem.nagoya-u.ac.jp
Journal of the American Chemical Society
|October 2, 2003
まとめ
ルテニウム触媒は,1,6-ダイネとモノアルキンの化学選択反応を可能にし,バイサイクルベンゼン誘導体を形成します. この方法は非対称なダイヌの優れた地域選択性を提供し,分子内サイクロトリメリゼーションも達成できます.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 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
背景:
- ルテニウム複合体は,有機合成における汎用的な触媒である.
- サイクル添加反応は,循環的有機分子を構築する上で根本的なものです.
- 代替ベンゼン誘導体の効率的な合成は,依然として重要な課題です.
研究 の 目的:
- バイサイクルベンゼン誘導体を合成するための新しいルテニウム触媒法を開発する.
- 非対称な1,6-ダイヌとモノアルキヌを含むサイクロアディション反応の地域選択性を調査する.
- この触媒システムの応用を,分子内アルキンサイクロトリメリゼーションで探求する.
主な方法:
- Cp*RuCl ((コッド)) を用いて1,6-ダイネとモノアルキンの触媒反応.
- X線解析によるルテナバイサイクル複合体の合成と構造的特徴化.
- 密度関数理論 (DFT) は,反応メカニズムを解明するための研究である.
主要な成果:
- 1,6-ダイヌとモノアルキンからバイサイクルベンゼン誘導体の化学選択的形成は,良好な収量で.
- 非対称なダイヌのサイクル添加で高い地域選択性が観察され,メタ置換された製品が得られる.
- トライインの分子内サイクロトリメリゼーションが成功し,トリサイクル芳香化合物が形成されます.
- 重要なルテナサイクルの中間物質の分離と特徴付け.
結論:
- Cp*RuCl ((cod) は,ダイヌアルキンサイクロアディションとトリインサイクロトリメリゼーションの効果的な触媒である.
- 開発されたプロトコルは,幅広い機能群を許容しています.
- 反応メカニズムは,ルテナサイクルの中間体への酸化サイクルを伴うアルキンの挿入に続く.
関連する概念動画
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[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.
01:12Cycloaddition 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.