レドックス・リレー戦略を用いたアサイクリックアルケニルアルコールのエナンチオセレクティブヘックアリレーション
Erik W Werner1, Tian-Sheng Mei, Alexander J Burckle
1Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112, USA.
Science (New York, N.Y.)
|December 15, 2012
まとめ
この研究では,アリルカルボニル化合物を生成するためのエナンチオセレクティブのヘック結合反応を導入しています. この新しい触媒システムは,高い地域選択性とエナチオ選択性を達成し,複雑な分子のための新しい合成経路を提供します.
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:
- 非対称なヘック結合は,複雑な有機分子を合成するために不可欠です.
- 移動性挿入とβ-水素除去における選択性の理解が限られていることは,進歩を妨げています.
研究 の 目的:
- アリルカルボニル産物合成のためのエナンチオセレクティブのヘック結合変種を開発する.
- 反応における地域選択性とエナチオ選択性を支配する要因を解明する.
主な方法:
- 非対称なヘックカップリングのための新しい触媒システムを利用しました.
- アリルディアゾニウム塩をアレン源として使用した.
- アサイクリックアルケノール基板との反応を調査した.
主要な成果:
- ベータ,ガンマ,デルタ-アリルカルボニル産物のエナチオセレクティブ合成を達成した.
- 移住の挿入とアルケーン不飽和の移住において高い地域選択性を示した.
- サブストラットキラリティにかかわらず,対極アルケーン構成からの観察されたエナティオメリック産物.
結論:
- 開発された触媒システムは,アリルカルボニル化合物の効率的なエナンチオセレクティブ合成を可能にします.
- 地域選択性およびエナチオ選択性に関するメカニズム的な洞察が得られた.
- 容易に入手可能なリガンドとアリルジアゾニウム塩を用いた多用途な方法を提供する.
関連する概念動画
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
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.
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
02:27Preparation of Alkynes: Alkylation Reaction
Introduction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
01:11Electrophilic Aromatic Substitution: Friedel–Crafts Acylation of Benzene
The Friedel–Crafts acylation reactions involve the addition of an acyl group to an aromatic ring. These reactions proceed via electrophilic aromatic substitution by employing an acyl chloride and a Lewis acid catalyst such as aluminum chloride to form aryl ketone.
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.