C-H ボンドのアクティベーションの完全な反応プロフィールをキャプチャします

David Gygi¹, Miguel I Gonzalez¹, Seung Jun Hwang¹

¹Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.

Journal of the American Chemical Society

|April 16, 2021

まとめ

研究者らは,光を使って塩素ラジカルを生成する鉄複合体を開発し,固体状態でのC−H結合活性化とその中間物質の研究を可能にしました.

科学分野:

有機金属化学
写真化学
反応メカニズムの研究

背景:

C-H結合の活性化は化学において極めて重要であるが,高度に反応性の高い中間物質のためには困難である.
これらの中間物質の研究には短命な種を捕まえるための特殊な技術が必要です

研究の目的:

光を用いたC−H結合の活性化のための新しい方法を開発する.
光生成塩素基によるC−H結合活性化のメカニズムを調査する.
固体状態の鍵となる中間物質を特徴づけるため

主な方法:

鉄 (III) クロリド-ピリジニミン複合体の合成
反応中間物質を観察するために,光照射とトランジントスペクトロスコーピーを用いる.
放射性構造を決定する光結晶学
第一原理分子動力学と密度関数理論 (DFT) の計算.

主要な成果:

鉄の複合体は光照射で塩素基を成功裏に生成した.
暫定的なクロイダセレンの複合中間物質が観察された.
ピリジネジミンのリガンドのC-H結合が活性化され,HClと炭素中心のラジカルが形成された.
計算による研究により,クロイダガレンの中間生成の反応経路が解明されました.

結論:

この研究は,固体状態でのC−H結合活性化のための完全な反応プロファイルを示している.
このフォト・イニシアチブ・メソッドは,C−H活性化における反応性中間物質の研究を可能にします.
発見は,C-H結合機能化反応の制御に関する洞察を提供します.

さらに関連する動画

06:34

Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides CHIPS

Published on: June 20, 2014

14.1K

07:36

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

Published on: November 9, 2019

8.2K

関連する概念動画

01:26

Photochemical Electrocyclic Reactions: Stereochemistry

2.0K

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

2.0K

01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

2.3K

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.

2.3K

02:13

Bond Dissociation Energy and Activation Energy

10.2K

Bond energy is the energy required to break a bond homolytically. These values are usually expressed in units of kcal/mol or kJ/mol and are referred to as bond dissociation energies when given for specific bonds or average bond energies when indicated for a given type of bond over many compounds. Firstly, the bond dissociation energy for a single bond is weaker than that of a double bond, which in turn is weaker than that of a triple bond. Secondly, hydrogen forms relatively strong bonds with...

10.2K

01:13

¹H NMR: Complex Splitting

1.5K

A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...

1.5K

01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.2K

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.

2.2K

02:36

Regioselectivity and Stereochemistry of Hydroboration

8.8K

A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.