サイクリックエステルのアニオン環開きポリメリゼーションのためのカチオン依存の二重活性化モチーフ
Caleb N Jadrich1, Vince E Pane1, Binhong Lin1
1Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States.
Journal of the American Chemical Society
|May 3, 2022
まとめ
研究者らは,ラクトンの迅速かつ制御されたリング開きポリメリゼーションのための新しい有機触媒である2,2'-ビシンドルアニオンを発見した. この触媒は対離子経由でモノマーを活性化させ,調節可能なポリメリゼーション率と高い選択性を可能にします.
科学分野:
- ポリマー化学
- 有機触媒
背景:
- リングオープニングポリメリゼーション (ROP) は,ポリエステル合成に不可欠です.
- 既存の有機触媒は,モノメア活性化のためにしばしば水素結合に依存している.
- 正確なポリマー合成には,代替的な活性化メカニズムを持つ新しい触媒の開発が不可欠です.
研究 の 目的:
- ラクトンの ROP のための新種の有機触媒を特定し,特徴づけること.
- 新しい触媒によるモノマー活性化のメカニズムを調査する.
- 触媒改変によるポリメリゼーション運動の調節性を探求する.
主な方法:
- 2,2'-ビシンドール誘導体の合成と特徴付け
- 様々なラクトンを用いたリング開封ポリメリゼーション実験
- 運動学的研究と機械学的調査 (例えば,NMRスペクトロスコーピーを用いて)
- 分子量分布 (Đ) を含むポリマーの性質の分析
主要な成果:
- 2,2 -ビシンドルアニオンは,乳酸塩のROPを効率的に触媒化することが判明した.
- ポリメリゼーションは急速に進み (10 msまで) 生命特性を示した (Đ ≤1.1).
- 水素結合とは異なるカウンテリオンによる新しいモノマー活性化メカニズムが解明された.
- ポリメリゼーションの速度は,カウンターイオンを変えることで2つの量位で調節された.
結論:
- 2,2 -ビシンドールのアニオンは,RPのための新しい器官触媒のクラスを表します.
- カウンテリオン媒介活性化メカニズムは,ポリメリゼーションを制御するための新しい戦略を提供します.
- この発見は,よく定義されたポリエステルの合成のための多用途のプラットフォームを提供します.
関連する概念動画
Base-Catalyzed Ring-Opening of Epoxides
8.9K
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...
8.9K
Acid-Catalyzed Ring-Opening of Epoxides
7.7K
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...
7.7K
Cationic Chain-Growth Polymerization: Mechanism
2.4K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
2.4K
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
2.7K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
2.7K
Anionic Chain-Growth Polymerization: Overview
2.2K
The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
2.2K
Anionic Chain-Growth Polymerization: Mechanism
2.1K
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael...
2.1K


