塩素ラジカルを抑制する:塩素ラジカル媒介によるC-H活性化に対するステリック制御を強制する
Miguel I Gonzalez1, David Gygi1, Yangzhong Qin1
1Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
Journal of the American Chemical Society
|January 12, 2022
まとめ
研究者は 鉄複合体を用いて 反応性塩素基を制御し 特定の炭素-水素結合を 選択的に機能させました この突破により 精密な化学反応が可能になり ステリック制御を通して 基質の反応を誘導します
科学分野:
- 有機金属化学
- 写真化学
- 有機合成
背景:
- 塩素ラジカルは非常に反応性があり,選択的なC-H機能化での使用を制限する.
- C-H結合の活性化における地域選択性を達成することは,合成化学における重要な課題である.
研究 の 目的:
- 金属複合体の二次協調球が 放射性塩素を閉じ込めることを証明する
- 地域選択的なC-H機能化のための塩素基反応性に対するステリック制御を達成する.
主な方法:
- 鉄 (III) クロリドピリジミン複合体を用いた光化学C ((sp3) -H塩化およびブロミン反応.
- 放射性物質の収束を研究するために,一時的吸収スペクトロスコーピー.
- 選択性の構造的基礎を明らかにする光結晶学.
主要な成果:
- 鉄の複合体は選択的に塩素化され,初次および二次C-H結合をブロミン化します.
- 複合体の二次調整圏内に塩素ラジカルを閉じ込めることで選択性が達成された.
- トランジエント吸収スペクトロスコーピーは,Cl·ササレン複合体によるCl·閉じ込めを確認した.
結論:
- 金属複合体の二次調整球は,反応性急性中間物質を効果的に制御することができます.
- この戦略は,熱力学的好みを優先して,地域選択的なC-H機能化を可能にします.
- この発見は,有機合成の精密な制御のための新しい道を開きます.
関連する概念動画
01:33Radical Halogenation: Stereochemistry
3.9K
Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be understood from three different situations:
Halogenation to form a new chiral center:
Halogenation to form a new chiral center:
3.9K
01:10Radical Reactivity: Steric Effects
2.0K
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic...
Along with electronic...
2.0K
01:31Radical Substitution: Allylic Chlorination
2.6K
Typically, when alkenes react with halogens at low temperatures, an addition reaction occurs. However, upon increasing the temperature or under reaction conditions that form radicals, providing a low but steady concentration of halogen radicals, allylic substitution reaction is favored. This is because allylic hydrogens are very reactive as the formed intermediate is resonance stabilized. For example, when propene is treated with chlorine in the gas phase at 400 °C, it undergoes allylic...
2.6K
01:02Radical Reactivity: Electrophilic Radicals
2.0K
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a...
2.0K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
3.7K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
3.7K
01:27Radical Substitution: Halogenation of Alkanes and Alkyl Substituents
8.8K
In the presence of heat or light, alkanes react with molecular halogens to form alkyl halides by a substitution reaction called radical halogenation. This reaction has three steps: initiation, propagation, and termination, as seen in the radical chlorination of methane to produce methyl chloride.
In the initiation step of the reaction, the chlorine molecule undergoes homolytic cleavage in the presence of light or heat, forming two highly reactive chlorine radicals. Propagation occurs in two...
In the initiation step of the reaction, the chlorine molecule undergoes homolytic cleavage in the presence of light or heat, forming two highly reactive chlorine radicals. Propagation occurs in two...
8.8K