スカンジウム触媒による機能化されたα,ω-ダイエンの地域およびステレオ選択性サイクロポリメリゼーションおよびエチレンとの共ポリメリゼーション
Haobing Wang1, Yanan Zhao2, Masayoshi Nishiura1,3
1Advanced Catalysis Research Group , RIKEN Center for Sustainable Resource Science , 2-1 Hirosawa , Wako , Saitama 351-0198 , Japan.
Journal of the American Chemical Society
|July 26, 2019
まとめ
この研究では,スクンジウム触媒を用いた機能化されたダイエンの制御されたサイクロポリメリゼーションが示され,高い地域性およびステレオ選択性を達成した. この発見は,精密に構造化されたサイクルポリマーを作るための新しい経路を提供します.
科学分野:
- ポリマー化学
- 有機金属化学
- カタリシス
背景:
- ヘテロ原子機能化されたα,ω-ダイエンのサイクロポリメリゼーションにおける地域とステレオ化学の正確な制御は重要な課題である.
- 既存の方法はよく定義されたサイクルポリマーアーキテクチャを生成するために必要な選択性が欠けている.
研究 の 目的:
- エーテルとチオエーテル機能化された1,6-ヘプタディエンの地域,二重選択,およびステレオレギュラーサイクロポリメリゼーションを達成する.
- ポリメリゼーション結果の制御における触媒-モノマー相互作用の役割を調査する.
- 機能化されたダイエンのエチレンとのコポリメリゼーションを調査する.
主な方法:
- 1,6-ヘプタディエン誘導体のサイクルポリメリゼーションに半サンドイッチスカンジウム触媒を使用した.
- 反応メカニズムを理解するために,密度関数理論 (DFT) の計算を使用した.
- 4-ベンジロキシ-1,6-ヘプタディエンと4-フェニルチオ-1,6-ヘプタディエンのポリメリゼーション実験を行った.
主要な成果:
- 4-ベンジロキシ-1,6-ヘプタディエンの同型サイクロポリメリゼーションが達成され,1,2,4-シス置換エチレンサイクロペンタン (ECP) マイクロ構造 (95% mmm) が得られた.
- 4-フェニルチオ-1,6-ヘプタディエンのポリメリゼーションで高いイソタクシー性 (95% rrr) を得,1,2-トランス-1,4-シス-ECP単位のみを形成する.
- DFT計算は,レジオとステレオ化学の制御におけるスカンジウム-ヘテロ原子相互作用の重要な役割を確認した.
- 機能化された1,6-ヘプタディエンのエチレンとの制御された共ポリメリゼーションが実証された.
結論:
- 半サンドイッチスカンジウム触媒は,1,6-ヘプタディエンのサイクロポリメリゼーションの地域およびステレオ化学を正確に制御できます.
- スカンジウム触媒とダイエン単体内のヘテロ原子の相互作用は,ステレオ規則性を達成する鍵です.
- この研究は,定義されたマイクロ構造を持つ機能化されたサイクルポリマーとコポリマーを合成するための新しい方法を提供します.
さらに関連する動画
06:34Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides CHIPS
Published on: June 20, 2014
14.3K
07:56Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyltroponeiron
Published on: August 12, 2019
8.3K
関連する概念動画
01:21Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
4.8K
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
4.8K
01:29Diels–Alder Reaction: Characteristics of Dienes
5.1K
The Diels–Alder reaction brings together a diene and a dienophile to form a six-membered ring. Both components have unique characteristics that influence the rate of the reaction.
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable,...
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is more stable,...
5.1K
01:16Structure of Conjugated Dienes
6.9K
Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
6.9K
01:28Stability of Conjugated Dienes
4.2K
Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
4.2K
02:24Acid-Catalyzed Ring-Opening of Epoxides
8.8K
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
8.8K
02:26Base-Catalyzed Ring-Opening of Epoxides
10.1K
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
10.1K