(レトロ) サイクロプロパネーションの潜在エネルギー表面:カチオンの金複合体によるメタテシス
Alexey Fedorov1, Laurent Batiste, Andreas Bach
1Laboratorium für Organische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
Journal of the American Chemical Society
|June 24, 2011
まとめ
量子化学的な計算により,オレフィンと黄金イリデンの反応が説明される. 深い潜在的最小値は,ガス相速度および溶液相レトロサイクロプロパネーションを含むサイクロプロパネーションとメタテシスを明確にします.
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:
- リガンド系金アリルデンは,電子が豊富なオレフィンでサイクロプロパナーションとメタテシス反応性を示す.
- これらの反応経路を理解することは,触媒設計とメカニズムの解明に不可欠です.
研究 の 目的:
- 金アリデンのガス相サイクロプロパネーションとメタテシスメカニズムを量子化学的計算を用いて解明する.
- 理論的発見と実験的観測を相関させるため,電子効果と製品比率を含む.
主な方法:
- 密度関数理論 (DFT) の計算を用いて,潜在エネルギー表面をマッピングした.
- 率決定のステップを決定するために,移行状態と中間物質の分析.
主要な成果:
- 金属に結合したサイクロプロパン添加物の深層の潜在的最小値が特定され,実験エネルギーと一致しました.
- ガス相サイクロプロパネーションは,ルイス酸性金属断片解離によって制限されます.
- メタテシス経路は,製品解離に近い複数の速度を制限する移行状態を含む.
結論:
- 計算された潜在エネルギー表面は,観測されたガス相および溶液相反応を正確に説明します.
- アリリデンとリン酸イリドリガンドの電子効果は,製品分布に影響を与えます.
- この研究は,金触媒によるサイクロプロパネーションとメタテシスの包括的なメカニズム的理解を提供します.
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.
01:16Cycloaddition Reactions: Overview
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.
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
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.
01:13Olefin Metathesis Polymerization: Overview
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...
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