シルバー触媒化 [2 + 2] シロキシアルキネスのサイクル添加物
Randy F Sweis1, Michael P Schramm, Sergey A Kozmin
1University of Chicago, Department of Chemistry, 5735 South Ellis Ave, Chicago, Illinois 60637, USA.
Journal of the American Chemical Society
|June 17, 2004
まとめ
この研究は,シロキシアルキンと不飽和カルボニル化合物を用いた最初の触媒 [2+2] サイクル添加を導入します. シルバートリフローロメタネスルフォニミドは,これらの反応を効率的に促進し,高い選択性と幅広い基板範囲を提供します.
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
- サイクル添加反応 サイクル添加反応
背景:
- サイクル添加反応は有機合成において根本的な役割を果たします.
- シロキシアルキンは,万能な構成要素である.
- サイクロアディションのための新しい触媒システムの開発は,依然として活発な研究分野です.
研究 の 目的:
- シロキシアルキンと不飽和カルボニル化合物の最初の触媒 [2+2] サイクル添加を記述する.
- この変換における銀のメカニズムと触媒の役割を調査する.
- 開発された反応の範囲と選択性を確立する.
主な方法:
- シルバートリフオロメタネスルフォニミドをシブストイキオメトリック量で触媒として使用.
- 様々なシロキシアルキンが様々な不飽和カルボニル化合物と反応する.
- 反応製品の特徴は,スペクトロスコーピテクニックを用いて判定する.
- 運動分析と中間捕獲を含むメカニズム研究.
主要な成果:
- シロキシアルキンの最初の [2+2] サイクル添加を不飽和カルボニル化合物で成功させた.
- サイクル添加製品において,高い地域およびダイアステレオ選択性を示した.
- 反応のための広い基板範囲を確立した.
- シロキシアルキネの銀基活性化を含む段階的な反応機構を明確に明らかにした.
結論:
- 開発された銀触媒 [2+2] サイクロアディションは,価値ある有機化合物への新しい効率的な経路を提供します.
- 銀は,複合化を通じてシロキシアルキンを活性化させ,1,4-添加を促進する上で重要な役割を果たします.
- 反応の高度な選択性と幅広い範囲は,合成化学者の強力なツールになります.
関連する概念動画
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.
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.
02:24Reduction 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.
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.
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.