コバルト-ディニトロシル媒介のビニルC-H機能化反応を通じたアルケンの直接マイケルの添加
Chen Zhao1, F Dean Toste, Robert G Bergman
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|June 25, 2011
まとめ
この研究では,コバルト-ニトロシル複合体を用いてアルケンの直接的なC-H機能化を導入しています. ワンポット・メソッドは,循環性,不飽和化合物を効率的に合成し,触媒的潜在性を示しています.
科学分野:
- 有機金属化学 有機金属化学
- オーガニック・シンセシス オーガニック・シンセシス
- カタリシス カタリシス カタリシス
背景:
- 直接的なC-H機能化は,複雑な分子へのより原子経済的な経路を提供します.
- コバルト-ニトロシル複合体は,有機変異においてユニークな反応性を提供します.
- 循環性,不飽和化合物の効率的な合成は,有機化学における重要な課題です.
研究 の 目的:
- アルケンのワンポット,直接のC-H機能化反応を開発する.
- コバルト-ニトロシル複合体をこの変換の媒介として利用する.
- サイクルテトラアルキル置換,γ,δ不飽和化合物を合成する.
主な方法:
- ワンポット反応手順が採用されました.
- アルケンの直接的なC-H機能化は[CpCo ((NO)) ((2)) ] (サイクロペンタディエニルコバルトディニトロシル) によって媒介された.
- すべての反応中間物質の特性分析が行われました.
主要な成果:
- この反応は,周期的なテトラアルキル置換,γ,δ不飽和化合物を得ることに成功した.
- 様々なマイケルの受容体は,この手順と互換性がありました.
- 良質な産物産出が達成されました.
結論:
- 開発されたワンポット・メソッドは,貴重な循環不飽和化合物への効率的な経路を提供します.
- この反応は,直接のC-H機能化における[CpCo ((NO)) ((2)) ]の有用性を示しています.
- 予備的な結果は,触媒のターンオーバーの可能性を示し,持続可能な合成における将来の応用を示唆しています.
関連する概念動画
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The attack of a nucleophile at the β carbon of an α,β-unsaturated carbonyl compound is called conjugate addition. Conjugate addition reactions of active methylene compounds, such as β-diketones, β-keto esters, β-keto nitriles, and α-nitro ketones, are called Michael addition reactions.
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).
02:35Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
01:17Radical Anti-Markovnikov Addition to Alkenes: Mechanism
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.