Co (III) 触媒によるC-H活性化/形式的なSN型反応:選択的で効率的なシアン化,ハロゲン化,およびアリレーション
Da-Gang Yu1, Tobias Gensch, Francisco de Azambuja
1Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster , Corrensstrasse 40, 48149 Münster, Germany.
Journal of the American Chemical Society
|December 5, 2014
まとめ
コバルト (III) 触媒は,シアン化,ハロゲン化,およびアリレーションのための新しいC-H活性化を可能にします. これらの反応は,前例のない室温アライレーションを含む,高い選択性を持つ貴重な有機化合物を生成します.
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
- 合成方法論 合成方法論
背景:
- C-H活性化は,有機合成のための強力なツールです.
- コバルト触媒は,ユニークな反応性プロファイルを提供します.
- 選択的で効率的なC-H機能化の方法を開発することは極めて重要です.
研究 の 目的:
- C-H活性化によるコバルト触媒による最初のシアン化,ハロゲン化,およびアリレーション反応の開発.
- これらの変換のために,ベンチ安定のCo ((III)) 触媒を使用する.
- アルケニル基板とアミドのCp*Co(III) -触媒化C-H活性化における使用を調査する.
主な方法:
- C-H活性化のためのベンチ安定のCo (III) 触媒を使用する.
- シアン化,ハロゲン化 (ヨウ素化およびブロミン化),およびアリレーション反応の調査.
- アミドを含む様々な (ヘテロ) アリルおよびアルケニル基板を使用する.
主要な成果:
- 初のコバルト触媒によるシアネーション,ハロゲネーション,C-H活性化によるアリレーションを達成した.
- 生成された有価な (ヘテロ) アリル/アルケニルニトリル,ヨジド,ブロミド,およびアリル化インドール.
- 高い地域および単一選択性を示した.
- 報告された前例のない室温アライレーションで,売上数は2200でした.
- アルケニル基板とアミドをCp*Co(III) 触媒によるC-H活性化に初めて成功裏に利用した.
結論:
- コバルト (III) 触媒は,様々なC−H機能化反応に有効である.
- これらの方法は,貴重な有機分子への効率的なアクセスを提供します.
- この研究は,Cp*Co(III) 触媒によるC-H活性化の範囲を,新しい基質クラスと反応条件に拡大しています.
さらに関連する動画
関連する概念動画
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
5.3K
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...
5.3K
01:10Aldehydes and Ketones with HCN: Cyanohydrin Formation Mechanism
4.8K
Cyanohydrins are formed when cyanide nucleophiles and carbonyl compounds like aldehydes and ketones react. A strong base, the cyanide ion, catalyzes cyanohydrin formation. The ions are generated from HCN under aqueous conditions. Once the cyanide ions are generated, the first step involves the nucleophilic attack of the cyanide ions on the electrophilic carbonyl carbon. This attack shifts the π electrons from the C=O to the oxygen atom forming the alkoxide ion intermediate. The alkoxide...
4.8K
01:32Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview
4.4K
Cyanohydrins are compounds that contain –CN and –OH groups on the same carbon atom. They are formed by the nucleophilic addition of the cyanide ions to the carbonyl group. Cyanide ions are highly basic and nucleophilic and can be generated from HCN under aqueous conditions. However, since HCN is a weak acid, the number of cyanide ions generated is very small. Hence, a small amount of base or KCN/NaCN is added to HCN to increase the concentration of the cyanide ions in the reaction...
4.4K
00:51Base-Promoted α-Halogenation of Aldehydes and Ketones
4.4K
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. The reaction begins with the abstraction of α hydrogen by the base to produce a nucleophilic enolate ion. This intermediate undergoes a subsequent nucleophilic substitution with the halogen to produce a monohalogenated carbonyl compound. If the starting substrate has more than one α hydrogen, it is difficult to stop the reaction...
4.4K
02:38Electrophilic Addition to Alkynes: Halogenation
10.7K
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
10.7K
02:46Halogenation of Alkenes
21.7K
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.
21.7K