触媒的非対称な水酸化ビニル化による全炭素四次中心. エキソサイクルサイドチェーン立体化学の問題への新しいアプローチ
1Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
Journal of the American Chemical Society
|April 28, 2006
まとめ
この研究では,エチレンを使用した1-アルキルステリンの効率的なニッケル触媒化水酸化ビニル化を導入しています. この反応により,四次中心の有価な製品が生み出され,さらなる合成用途のための優れた産出率とエナチオ選択性を示します.
科学分野:
- 有機金属化学 有機金属化学
- アシンメトリック・カタリシス
- オーガニック・シンセシス オーガニック・シンセシス
背景:
- 水酸化ビニル化は,C-C結合形成の重要な反応である.
- 効率的でエナチオセレクティブな触媒システムの開発は依然として課題です.
研究 の 目的:
- 1-アルキルステリンの高効率でエナチオセレクティブなニッケル触媒化ヒドロビニル化を開発する.
- 結果となる製品の合成的有用性を探求する.
主な方法:
- [(アルリル) NiBr]2とNa+BAr4-.から調製されたニッケル触媒を使用しました.
- エナンチオプアビナフトールと1-メチルベンジラミンから派生したフォスフォラミドイトリガンドが使用されています.
- エチレンと反応した1-アルキルスタイレン.
主要な成果:
- 1-アルキルスタイレンをエチレンで効率的に水素ビニル化.
- 得られた製品は,優れた収穫量と高いエナチオ選択性を持つ.
- 製品には,アレンとビニールグループを持つ四次中心が特徴です.
結論:
- 開発された触媒システムは,エナチオセレクティブ・ヒドロビニレーションに非常に有効です.
- これらの製品は,さらなる合成変換のための汎用的な構成要素として機能します.
さらに関連する動画
関連する概念動画
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
01:04Anionic Chain-Growth Polymerization: Mechanism
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael acceptor.
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:17Pericyclic Reactions: Introduction
Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...