動力制御から熱力学的制御への変更は,近隣ダイオルの選択的ステレオ化学編集を可能にする
Yu-An Zhang1, Xin Gu1, Alison E Wendlandt1
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|December 20, 2021
まとめ
この研究は,軽度の光還元条件下でトリフェニルシラネチオールを用いて,シス-1,2-ダイオルをトランス-デイエクアトリアル-1,2-ダイオルにイソメーライズするための新しい触媒方法を導入しています. このアプローチは,有価なトランスダイオール製品への選択的で効率的な経路を提供します.
科学分野:
- 有機化学
- カタリシス
- ステレオ選択合成
背景:
- 1,2-ジオールは多用途の有機化合物です.
- トランス-1,2-ダイオルのステレオ選択的合成は難しい.
- トランスダイオール合成の既存の方法は限られている.
研究 の 目的:
- cis-1,2-diolsをtrans-diequatorial-1,2-diolsに選択的にイソメリゼーションするための新しい方法を開発する.
- トランスダイオール製品への より効率的でアクセシブルな経路を提供すること
- 反応メカニズムを調査する
主な方法:
- トリフェニルシラネチオール (Ph3SiSH) を用いた触媒性異体化.
- 青い光の照射下でのフォトレドックス触媒
- 軽度の反応条件
主要な成果:
- cis-1,2-diolsをtrans-diequatorial-1,2-diolsに選択的に変換する.
- 高い化学選択性と幅広い機能群の耐性.
- 価値あるトランスダイオール製品への簡潔なアクセス
結論:
- 開発された方法は,効率的で選択的な経路で,トランス-デイエクアトリアル-1,2-ダイオルを提供します.
- 反応は,シラネチオール触媒による可逆水素原子移転メカニズムによって進行する.
- この方法論は,難しいステレオアイソマーにアクセスするための合成の可能性を拡大します.
関連する概念動画
01:23Electrophilic Addition of HX to 1,3-Butadiene: Thermodynamic vs Kinetic Control
3.0K
The addition of a hydrogen halide to 1,3-butadiene gives a mixture of 1,2- and 1,4-adducts. Since more substituted alkenes are more stable, the 1,4-adduct is expected to be the major product. However, the product distribution is strongly influenced by temperature; low temperature favors the 1,2-adduct, whereas the 1,4-adduct is predominant at high temperature.
3.0K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.1K
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.
2.1K
01:33Regioselective Formation of Enolates
2.9K
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.
2.9K
01:29Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
4.9K
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
4.9K
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
11.0K
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
11.0K
01:31Diels–Alder vs Retro-Diels–Alder Reaction: Thermodynamic Factors
5.3K
The Diels–Alder reaction is thermally reversible, meaning that the reaction reverts to the starting diene and dienophile under suitable temperatures. The forward reaction gives a cyclohexene derivative and is favored at low to medium temperatures. The reverse process, also called retro-Diels–Alder reaction, is a ring-opening process favored at high temperatures.
5.3K