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1,3-ダイエンのエナチオセレクティブ鉄催化クロス[4+4]-サイクロアディションはキラルサイクロオクタディエンを提供する

  • 0Laboratory of Asymmetric Catalysis and Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
Journal of the American Chemical Society +

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2020年11月11日

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2020年11月11日

PubMedで要約を見る

まとめ

この要約は機械生成です。

研究者は,キラルサイクロオクタディエンを生成するための新しい鉄触媒方法を開発しました. この効率的な非対称合成は,触媒と天然製品の合成のための貴重な化合物へのアクセスを提供します.

科学分野

  • 有機化学
  • 非対称な触媒

背景

  • チラルのサイクロオクタディエンは,天然製品と特殊化学物質の重要な支架です.
  • 非対称な触媒のリガンドとしてそれらの使用は重要である.
  • 代替サイクロオクタディエンの効率的な非対称合成は依然として課題です.

研究 の 目的

  • 代替サイクロオクタディエンの合成のための効率的な非対称的な方法を開発する.
  • エナチオセレクティブのクロス[4+4]-サイクロアディション反応のための鉄触媒を用いる.

主な方法

  • クイラル・α-ダイミン・アイアン・コンプレクスを使った
  • 1,3-ダイエンの鉄触媒によるエナチオセレクティブクロス[4+4]-サイクロアディションを用いる.
  • 選択性を理解するために鉄複合体のステリック因子を調査する.

主要な成果

  • 穏やかな条件下で代用サイクロオクタディエンの形成を達成した.
  • 優れた交叉選択性と非常に高い反選択性を示した.
  • 新しく機能化されたサイクロオクタディエンは,高収量とエナチオ選択性で得られた.

結論

  • 開発された鉄触媒方式は,キラルサイクロオクタディエンの迅速かつ原子経済的なアクセスを提供します.
  • 適合したキラルα-ダイミン鉄複合体は反応の成功に不可欠です.
  • この方法は,これらの貴重な化合物の非対称合成における以前の課題を克服します.

関連する概念動画

Cycloaddition Reactions: Overview 01:16

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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.

The feasibility of cycloaddition reactions under thermal and photochemical conditions can be predicted...

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction 01:16

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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.

From a molecular orbital perspective, the interacting lobes of the two π systems must be in phase to permit...

Diels–Alder Reaction Forming Cyclic Products: Stereochemistry 01:28

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The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.

For the electrons to flow seamlessly between the two π systems, specific stereochemical and conformational requirements must be met.
Stereochemical Orbital Symmetry
The frontier molecular orbitals that satisfy the symmetry requirements are the...

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry 01:29

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Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.

Dienophiles with one or more electron-withdrawing substituents form stereochemically different products in which the substituents are oriented in an endo (towards) or exo (away) configuration relative to the double bond.

The endo isomer is formed faster and is the kinetic product. The exo isomer is more stable and is the thermodynamic...

Cycloaddition Reactions: MO Requirements for Thermal Activation 01:16

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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.

The reaction occurs between the highest occupied molecular orbital (HOMO) of one π component and the lowest unoccupied molecular orbital (LUMO) of the other. These are known as...

Thermal Electrocyclic Reactions: Stereochemistry 01:17

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The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Conjugated...