炭水化物ベースのセレノエーサーとチオエーサーの軽度のプマーラー様反応で,線形オゾニドアセテートが推定の中間物質として作用する
Natacha Veerapen1, Stephanie A Taylor, Charles J Walsby
1Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6.
Journal of the American Chemical Society
|January 5, 2006
まとめ
この研究では,セレニウムと硫黄を含む炭水化物ヘテロサイクルにおけるプメラー再配列を調査しています. 研究者らは,ラジカル中間物質を含むプメラー製品の新しい,より穏やかな合成経路を発見しました.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 炭水化物化学 炭水化物の化学
- ヘテロサイクル化学 ヘテロサイクル化学
背景:
- ポンメラー再配列は,有機合成における重要な反応である.
- セレニウムを含むヘテロサイクルのプメラー再配列を調査することは,新しいことです.
- 炭水化物支架は,化学的変換のためのユニークな構造的特徴を提供します.
研究 の 目的:
- セレニウムと硫黄を含む炭水化物ベースのヘテロサイクルのプマーラーのような再配置を調査する.
- セレノヘロサイクルのプメラー再配置に関する最初のレポートを作成する.
- これらの再編成のメカニズムの探求,包括的には,急進的対協調的経路.
主な方法:
- 硫黄とセレニウムを含む炭水化物ヘテロサイクルのオゾン分解.
- オゾニド中介物質を捕獲するために,低温でアセチアンヒドリドを加える.
- 中間セレノキシドとスルフォキシドの分離と反応.
- ルーブレンを使用した過激な罠の実験.
- DMPOラジカルトラップを使った電子パラマグネット共振 (EPR) 研究.
主要な成果:
- オゾノリシス中に不安定なオゾノイド中介物質が形成された.
- Pummerer再配列製品は,低温でオゾン化混合物に酸性アンヒドリドを加えることで得られた.
- 単離されたセレノキシドとスルフォキシドもプーメラー再配置を受けたが,スルフォキシドにはより高い温度が必要だった.
- 証拠によると,再編成は,単にヘテロリチス的にではなく,ラジカル・インターミディエイトを通じて進みます.
- Pummerer型製品を生産するための新しい,より穏やかな方法が特定されました.
結論:
- ポンメラー再編成は,炭水化物ベースのセレノヘテロサイクルで効果的に達成できます.
- 反応のメカニズムは,捕獲とEPR研究によって支持された,過激な中間物質を含む可能性が高い.
- この研究は,プメラー製品合成のための新しい,より穏やかな合成アプローチを提示しています.
関連する概念動画
Preparation of Diols and Pinacol Rearrangement
Compounds bearing two hydroxyl groups are known as diols. When the hydroxyl groups are located on adjacent carbon atoms, the diols are called vicinal diols or glycols. Under acidic conditions, vicinal diols undergo a specific reaction called pinacol rearrangement.
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.
The reaction begins with transferring a proton from the acid catalyst to one of the hydroxyl groups, producing an oxonium ion.
Acid Halides to Carboxylic Acids: Hydrolysis
Hydrolysis of acid halides is a nucleophilic acyl substitution reaction in which acid halides react with water to give carboxylic acids. The reaction occurs readily and does not require acid or a base catalyst.
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
Acid Halides to Esters: Alcoholysis
Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:
Cationic Chain-Growth Polymerization: Mechanism
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 generated carbocation,...
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
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...
Reactions of Carboxylic Acids: Introduction
Carboxylic acids possess an acidic –COOH functional group. The acidity can be attributed to the resonance stabilization of their conjugate base, wherein the negative charge is delocalized over both oxygen atoms.
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