C2対称サイクルセレニウム触媒によるエナチオセレクティブブロモアミノサイクリング
Feng Chen1, Chong Kiat Tan, Ying-Yeung Yeung
1Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
Journal of the American Chemical Society
|January 15, 2013
まとめ
この研究は,オレフィン系アミドからキラル型ピロリジンを生成するための新しい触媒的非対称ブロモサイクリングを導入しています. これらのピロリジンは,高度にエナチオ濃縮されたピペリジンに変換され,新しい合成経路を示します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- アシンメトリック・カタリシス
- 合成方法論 合成方法論
背景:
- 複雑な窒素を含むヘテロサイクルを合成するための効率的な方法の開発は,医薬品化学において極めて重要です.
- 非対称な触媒は,有機合成におけるステレオ化学を制御するための強力なアプローチを提供します.
研究 の 目的:
- 三置換オレフィン系アミドの新種の触媒的非対称ブロモサイクリングを報告する.
- エナンチオ濃縮ピロリジンおよびピペリジン誘導体のステレオ選択合成を開発する.
主な方法:
- C(2) -対称なマニトール由来サイクルセレニウム触媒を使用しました.
- ブロム化剤としてN-ブロモフタリミドを使用した.
- ピロリジン産物のピペリジンへの再配置を調査した.
主要な成果:
- 三置換されたオレフィン系アミドの触媒的非対称ブロモサイクリングが達成された.
- 2つのステレオジェニックセンターを持つ,エンチオイン濃縮型ピロリジン製品を生成した.
- 2,3-非置換ピペリジンへの再配列が示され,高いダイアステロ選択性とエナントオ特異性を持つ.
結論:
- 開発された方法は,価値あるキラルピロリジンとピペリジンの効率的なアクセスを提供します.
- 触媒システムは,窒素ヘテロサイクルのステレオ制御合成のための新しい戦略を提供します.
- 再配置の高いエナチオスペシフィシティは,この変換の重要な特徴です.
関連する概念動画
Halogenation of Alkenes
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Formation of Halohydrin from Alkenes
An alkene, such as propene, reacts with bromine in the presence of water to yield a halohydrin. Halohydrins contain a halogen and a hydroxyl group attached to adjacent carbons. When the halogen is bromine, it is called a bromohydrin, while a chlorohydrin has chlorine as the halogen.
Radical Substitution: Allylic Bromination
In organic synthesis, the formation of products can be altered by changing the reaction conditions. For example, a dibromo addition product is formed when propene is treated with bromine at room temperature. In contrast, propene undergoes allylic substitution in non-polar solvents at high temperatures to give 3-bromopropene. In order to avoid the addition reaction, the bromine concentration must be kept as low as possible throughout the reaction. This can be achieved using N-bromosuccinimide...
SN2 Reaction: Stereochemistry
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not observed.
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
Radical Anti-Markovnikov Addition to Alkenes: Overview
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.


![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)