ルテニウム触媒による化学選択および地域選択によるポリイソブテンの酸化
Liye Chen1, Katerina G Malollari1, Adam Uliana1
1Department of Chemistry, University of California, Berkeley, California 94720, United States.
Journal of the American Chemical Society
|March 18, 2021
まとめ
研究者は,C−H結合を選択的に酸化することによって,枝分かれしたポリオレフィンであるポリイソブテンを機能化しました. このプロセスは,ルテニウム-ポルフィリン触媒を使用して,ポリマーを分解せずにケトン単位を追加し,その性質を高めます.
科学分野:
- ポリマー化学
- 材料科学
- カタリシス
背景:
- ポリオレフィンは多用途のプラスチックですが,その機能的グループが限られているため,応用が制限されています.
- ポリマーのC-H結合を機能化することで,新しい性質を導入できます.
- ポリイソブテンなどの分岐型ポリオルフェンの選択的機能化は,ステリック阻害と分解により困難である.
研究 の 目的:
- ポリイソブテンの化学選択的および地域選択的酸化を達成する.
- 枝分かれしたポリオレフィンの機能化における反応性や鎖分裂の問題を克服する.
- ポリイソブテンにケトン機能を導入し,ポリマーの整合性を損ないません.
主な方法:
- 新しいポリフッ化ルテニウムポルフィリン触媒を使用した.
- ポリイソブテンのメチレン位置にC−H結合を標的とした酸化反応を用いた.
- 熱安定性および化学反応性について機能化されたポリマーを特徴づけた.
主要な成果:
- 選択的C-H酸化により,ケトン単位をポリイソブテンに組み込みました.
- 機能化は,ポリマー鎖の分裂や分解を誘導することなく起こった.
- その結果,酸化されたポリイソブテンは,熱安定性と湿潤性性が向上した.
結論:
- 枝分かれしたポリオレフィンの化学選択性および地域選択性機能化の方法を開発した.
- ルテニウムポルフィリン触媒はポリイソブテンの制御された酸化を可能にし,以前の制限を克服しました.
- 機能化されたポリイソブテンは,特別の特性とプログラムされた反応性を要求する高度なアプリケーションの可能性を示しています.
関連する概念動画
03:08Hydroboration-Oxidation of Alkenes
9.8K
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
9.8K
02:36Regioselectivity and Stereochemistry of Hydroboration
8.8K
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
8.8K
01:13Olefin Metathesis Polymerization: Overview
2.3K
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
2.3K
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
9.4K
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
9.4K
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
11.5K
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
11.5K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
3.8K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
3.8K