プラチナで触媒化されたデヒドロアルコキシル化-サイクリングカスケードは,N-O結合割れによる
Itaru Nakamura1, Yusuke Sato, Masahiro Terada
1Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan. itaru-n@mail.tains.tohoku.ac.jp
Journal of the American Chemical Society
|March 10, 2009
まとめ
プラチナ触媒は,オルトアルキニルフェニル尿素前駆体から新しい四環化合物の効率的な合成を可能にします. このN-O結合分裂反応は,高収量で進行し,複雑な分子構造への新しい経路を提供します.
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
- 合成方法論 合成方法論
背景:
- オルトアルキニルフェニル尿素とアセタミドは,多用途の合成前駆体である.
- プラチナ触媒反応は,C-H活性化と循環化のためのユニークな経路を提供します.
- 複雑なポリサイクリック・スキャファードを構築するための効率的な方法の開発は,有機合成において極めて重要です.
研究 の 目的:
- オルトアルキニルフェニル尿素とアセタミドのプラチナ触媒サイクルを調査する.
- これらのサイクライゼーション反応におけるN-O結合割れメカニズムを探求する.
- 潜在的な応用を持つ新しい四環化合物を合成する.
主な方法:
- PtI ((4) を触媒として使用したプラチナ触媒サイクリング反応.
- N-アルコキシ-N'-アリル-オルト-アルキニルフェニル尿素とアセタミドの反応.
- 温度,溶媒,触媒の負荷を含む反応条件の最適化.
主要な成果:
- N-O結合割れによる前体1からテトラサイクリック化合物2の合成に成功した.
- サイクライゼーション製品の良質から優れた収穫量を達成しました.
- 反応機構として,イミニウム結合プラチナカルベノイド中間物質とそれに続く芳香C-H挿入を特定した.
結論:
- プラチナ触媒は,テトラサイクルインドロキナゾリノンの合成のための効果的な戦略を提供します.
- N-Oボンド分裂経路は,この新しい変容における重要なステップです.
- この方法論は,複雑なヘテロサイクルのシステムにアクセスするための合成化学者のツールキットに貴重な追加を提供します.
関連する概念動画
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
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.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
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.
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
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.
02:01Alkynes to Carboxylic Acids: Oxidative Cleavage
Alkynes undergo oxidative cleavage in the presence of oxidizing reagents like potassium permanganate and ozone. The triple bond — one σ bond and two π bonds — is completely cleaved, and the alkyne is oxidized to carboxylic acids. When warm and basic aqueous potassium permanganate is used as an oxidizing agent, alkynes are first converted to carboxylate salts via an unstable α-diketone intermediate. Further, a mild acid treatment protonates the carboxylate anions generating free carboxylic acid...