エアロビックコバルト触媒反応におけるアルケノールサイクル化の還元性およびブロミナティブ終結
Dominik Schuch1, Patrick Fries, Maike Dönges
1Fachbereich Chemie, Organische Chemie, Technische Universität Kaiserslautern, D-67663 Kaiserslautern, Germany.
Journal of the American Chemical Society
|August 22, 2009
まとめ
この研究では,ペント-4-エン-1-オルスのエアロビックコバルト ((II) -触媒酸化によるテトラヒドロフーラ-2-イルメチルラジカルの立体選択的生成が実証されています. これらのラジカルは,高度な合成有用性を持つ機能化されたテトラヒドロフーランを生成するために閉じ込められました.
科学分野:
- 有機化学 オーガニック・ケミストリー
- カタリシス カタリシス カタリシス
- ラジカル・ケミストリー (Radical Chemistry) とは
背景:
- テトラヒドロフラン派生体は,天然製品や医薬品に多く含まれています.
- 機能化されたテトラヒドロフーランの効率的な合成は,有機化学における重要な課題であり続けている.
研究 の 目的:
- テトラヒドロフル-2-イルメチルラジカルを生成するためのステレオ選択的方法を開発する.
- これらのラジカルを,多様な機能化されたテトラヒドロフーランの合成に活用する.
主な方法:
- エアロビックコバルト (((II) 誘導による代替ペント-4-エン-1-オールスの酸化.
- テトラヒドロフル-2-イルメチル基のステレオ選択的生成.
- 様々なディエノフィールやエレクトロフィール (例えば,サイクロヘキサ-1,4-ディエネ,アクリロニトリル) を用いてラジカルを捕まえる.
主要な成果:
- テトラヒドロフル-2-イルメチルラジカルのステレオ選択的生成が成功しました.
- 一連の機能化されたテトラヒドロフーランを合成して,合成的に有用な作物となった.
- この方法は,様々な捕獲剤に対して有効であることが証明され,その多用途性を示した.
結論:
- 開発されたコバルト (II) 触媒による有酸素酸化は,機能化されたテトラヒドロフーランへの新しい経路を提供します.
- この方法論は,価値あるヘテロサイクルの化合物を合成するためのステレオ選択的で効率的なアプローチを提供します.
関連する概念動画
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
03:08Hydroboration-Oxidation of Alkenes
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.
01:17Radical Anti-Markovnikov Addition to Alkenes: Mechanism
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
01:22Alkenes via Reductive Coupling of Aldehydes or Ketones: McMurry Reaction
The radical dimerization of ketones or aldehydes gives vicinal diols through a pinacol coupling reaction. However, the behavior of titanium metals used for the reaction as a source of electrons is unusual. When the reaction is carried out in the presence of titanium, diols can be isolated at low temperatures. Else titanium further reacts with diols, forming alkenes through the McMurry reaction.
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
02:46Halogenation of Alkenes
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.