エナチオセレクティブのコニアエネカルボサイクリングのための新しい鉄 (III) 塩素触媒
1Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States.
Journal of the American Chemical Society
|September 13, 2014
まとめ
新種のキラル鉄触媒は,非対称なサイクル反応を可能にし,ステレオ定義された四次中心を持つ複雑な分子を作成します. この方法では,シンプルな原材料から貴重なエクソメチレンサイクロアルカンを効率的に生成できます.
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:
- 四次炭素の中心は,多くの医薬品や天然製品の重要な構造モチーフです.
- ステレオ選択合成のための効率的な触媒方法の開発は,有機化学における重要な課題です.
研究 の 目的:
- 非対称なコニアエネ型サイクリングのための新しいキラル触媒を開発する.
- ステレオ定義された四次中心を持つエクソメチレンサイクロアルカンを合成する.
主な方法:
- シス-2,5-ダイアミノビサイクロ[2.2.2]オクタンの支架を備えたキラル鉄(III) -塩素複合体を使用した.
- α-機能化されたケトンの非対称なコニアン型サイクライゼーションを非活性化端末アルキンで採用した.
主要な成果:
- 触媒は,非対称なサイクリング反応を成功裏に媒介した.
- 四次中心の形成において高いステレオ選択性を達成した.
- 望ましいエクソメチレンサイクロアルカン製品を製造しました.
結論:
- 非対称なコニアエネ型サイクリングのための新しい触媒系が確立されました.
- この方法論は,立体的に定義された四次中心への効率的な経路を提供します.
- 開発された鉄触媒は,複雑な分子合成の有望性を示しています.
さらに関連する動画
関連する概念動画
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
2.6K
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
2.6K
01:10α-Alkylation of Ketones via Enolate Ions
2.2K
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...
2.2K
01:23Reactivity of Enolate Ions
2.4K
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, leading to a resonance-stabilized enolate ion where one of the contributing structures is an oxyanion, which imparts additional stability. Therefore, the proton on the α carbon is more acidic in nature than that of other sp3-hybridized C–H bonds but less acidic than those in O–H bonds where the negative charge in the conjugate...
2.4K
01:33Regioselective Formation of Enolates
2.6K
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.
2.6K
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
3.1K
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...
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...
3.1K
01:15Enolate Mechanism Conventions
2.2K
When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an enolate. Enolates are ambident nucleophiles because they possess two nucleophilic sites that can attack an electrophile owing to the delocalization of the negative charge between the α carbon and oxygen atoms. When the oxygen atom attacks an electrophile, it is called O-attack, whereas electrophilic attack via the α carbon is known as...
2.2K