ニッケル触媒 [4 + 2] サイクル添加でアルキネスによるエノンのサイクル添加
Ichiro Koyama1, Takuya Kurahashi, Seijiro Matsubara
1Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
Journal of the American Chemical Society
|January 29, 2009
まとめ
新しいニッケル触媒反応により,エノンやアルキンからポリ置換ピランの合成が可能になる. このメカニズムは,ニッケル媒介の酸化サイクリングとアルキンの挿入を含み,重要なオキサニッケルサイクル中間体を形成します.
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:
- ピランは,多くの天然製品や医薬品に含まれる重要なヘテロサイクリック化合物です.
- ポリ置換ピランを製造するための効率的な合成方法は,有機化学において非常に求められています.
- ニッケル触媒は,新しい炭素-炭素および炭素-ヘテロ原子結合形成反応を開発するための多用途のプラットフォームを提供します.
研究 の 目的:
- 新しいニッケル触媒化 [4 + 2] サイクル添加反応の開発.
- 簡単に入手可能なエノンとアルキンの出荷材料を用いて,ポリ置換ピランを合成する.
- 提案された触媒サイクルのメカニズム的経路を解明する.
主な方法:
- ニッケル触媒を用いて,エノンとアルキンの間の [4 + 2] サイクル添加反応を行う.
- 標準的なスペクトロスコーピテクニック (NMR,質量スペクトロメトリー) を用いて反応製品の特徴づけ.
- 機械論的提案を支えるための計算研究と中間捕獲実験.
主要な成果:
- エノンとアルキンの間のニッケル触媒化 [4 + 2] サイクル添加反応の成功開発.
- 様々なポリ置換ピランの高収量が得られた.
- 酸化サイクリング,アルキン挿入,および還元性除去を含む妥当な反応機構が提案され,オキサニケラサイクルの中間物質が特徴付けられました.
結論:
- 開発されたニッケル触媒反応は,ポリ置換ピランへの効率的な経路を提供します.
- 機械学的研究は,ニッケル媒介サイクロアディションプロセスに関する貴重な洞察を提供します.
- この方法論は,価値あるヘテロサイクリック化合物を合成するためのツールキットを拡張します.
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.
02:47Alkynes 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.
01:16Cycloaddition Reactions: Overview
Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.
01:26Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines are useful synthetic intermediates where the lone pair on nitrogen is in conjugation with the C=C bond. They resemble enolate ions, as the resonance forms of both species have a nucleophilic α carbon.
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.
02:38Electrophilic Addition to Alkynes: Halogenation
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.