サイクロメタル化ルテニウム複合体によるエナチオセレクティブオレフィンメタテシス
John Hartung1, Peter K Dornan, Robert H Grubbs
1Arnold and Mabel Beckman Laboratories of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology , Pasadena, California 91125, United States.
Journal of the American Chemical Society
|August 20, 2014
まとめ
NHCリガンドサイクロメタレーションによるエナチオ濃縮型触媒の設計により,高度に選択的なオレフィン転移反応が可能になる. このアプローチは,リングの開閉と,挑戦的な基板の交差メタテシスにおいて,Z-およびエナチオセレクティブの結果を達成します.
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
- ステレオ化学 ステレオ化学
背景:
- エナチオセレクティブオレフィンメタテシスには,ステレオ化学情報を転送する触媒が必要です.
- N-ヘテロサイクルカルベン (NHC) リガンドのサイクロメタレーションは,キラル触媒を作るための戦略です.
研究 の 目的:
- 非対称オレフィンメタテシスのためのエナチオ濃縮アルキリデン複合体の開発と評価.
- 様々なメタテシス反応におけるこれらの触媒のステレオ選択性と効率を調査する.
主な方法:
- サイクロメタレーションによる,エナチオ濃縮されたNHC結合ルテニウムアルキリデン複合体の合成.
- これらの触媒の適用は,非対称環開閉/交差メタテシス (AROCM),非対称環閉メタテシス (ARCM),および非対称交差メタテシス (ACM) で用いられる.
- 反応の可逆性とセットアップ効果の探求.
主要な成果:
- 触媒は,ノルボルネンとサイクロブテンのAROCMで高いZ-およびエナチオセレクティブ性を達成し,異なる増殖種が観察されました.
- プロキラルトリエンのARCMの成功が実証されました.
- 有望なエナチオセレクティビティは,プロキラル1,4-ディエネの新しいZ選択ACMで達成されました.
結論:
- NHCリガンドサイクロメタレーションは,高度にエナチオセレクティブなオレフィンメタテシスのためのキラル触媒の設計のための効果的な戦略です.
- 開発された触媒は,挑戦的な基板を含む様々な非対称的な転化反応において広範な適用性を示しています.
- 反応パラメータに関するさらなる研究は,触媒性能を最適化することができます.
さらに関連する動画
関連する概念動画
01:13Olefin Metathesis Polymerization: Overview
1.8K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
1.8K
00:53Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
1.4K
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...
1.4K
01:16Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
2.3K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
2.3K
01:17Thermal Electrocyclic Reactions: Stereochemistry
1.6K
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.
1.6K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
2.1K
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.
2.1K
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
8.6K
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
8.6K