協同触媒戦略によるエナチオセレクティブβプロトネーション
Michael H Wang1, Daniel T Cohen1, C Benjamin Schwamb1
1Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, Silverman Hall, Evanston, Illinois 60208, United States.
Journal of the American Chemical Society
|May 2, 2015
まとめ
N-ヘテロサイクリックカルベン (NHCs) を含む新しい協力型触媒システムは,高度に選択的なエナチオセレクティブβ-プロトネーションを可能にします. この有機触媒アプローチは,アリル-オクソブテノ酸からエナンチオ濃縮されたサクシネート誘導体を効率的に生成します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
- アシンメトリック・シンセシス
背景:
- N-ヘテロサイクリックカルベン (NHCs) は,多用途の有機触媒である.
- 非対称 β-プロトネーションは,キラル分子合成に不可欠です.
- 協同触媒は反応効率と選択性を高めることができます.
研究 の 目的:
- エナチオセレクティブのN-ヘテロサイクリックカルベン (NHC) 催化β-プロトネーション方法を開発する.
- 3つの異なる有機触媒の協力効果を調査する.
- 高度にエナチオ濃縮されたサクシネート誘導体を効率的に合成するために.
主な方法:
- 3つの臓器触媒システムの開発.
- β-プロトネーションのためのNHC触媒を用いて.
- アリル-オクソブテノアートが触媒システムと反応する.
主要な成果:
- β-プロトネーションで高収量とエナチオ選択性を達成した.
- アリル-オクソブテノアートのサクシネート誘導体への効率的な変換が実証されています.
- NHCのみの触媒と比較して性能が向上した.
結論:
- 協力的な触媒システムは,収穫量と選択性を大幅に改善します.
- この方法は,エナンチオ濃縮サクシネート誘導体への効率的な経路を提供します.
- オーガノカタリシスにおける異なる活性化モードの組み合わせは有益である.
関連する概念動画
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
10.1K
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
10.1K
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
18.8K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
18.8K
01:10α-Alkylation of Ketones via Enolate Ions
4.2K
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...
4.2K
01:33Regioselective Formation of Enolates
3.7K
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.
3.7K
02:36Regioselectivity and Stereochemistry of Hydroboration
9.8K
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.
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.
9.8K
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
11.9K
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
11.9K