形式的ヒドロキシル誘導C-H活性化によるイリジウム触媒化されたアレンオルトシリレーション
Eric M Simmons1, John F Hartwig
1Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
Journal of the American Chemical Society
|November 17, 2010
まとめ
新しい方法により,イリジウム触媒によるC-H活性化のための指向要素としてヒドロキシル基を用いた芳香化合物のオーソシリレーションが可能になった. この過程でベンゾキシアシロールが形成され,それらは価値あるフェノールまたはビアリル誘導体に変換できます.
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:
- 誘導C-H活性化は,有機合成における強力なツールである.
- ヒドロキシル群は,金属触媒反応における指向要素として作用する.
- オーソシライレーションの効率的な方法は,複雑な分子を作製する上で極めて重要です.
研究 の 目的:
- アリルケトン,ベンザルデヒド,およびベンジルアルコールのオーソシリレーションのための新しい戦略を開発する.
- イリジウム触媒によるC−H結合活性化のための指向要素としてヒドロキシル基を活用する.
- ベンゾキシシロール中間物質を合成し,その合成有用性を実証する.
主な方法:
- カルボニル化合物またはアルコールから (水素) シリルエーテルを単一生成する.
- ノルボレンネの存在下で[Ir(cod) OMe]2と1,10-フェナントロリンによって触媒化された脱水素化サイクリング.
- タマオ・フレミング酸化とヒヤマクロスカップリングによる製品変換.
主要な成果:
- 様々な芳香基質のオーソシライレーションに成功しました.
- ベンゾキシシロール誘導体の形成は,Ir-触媒によるC-H活性化とサイクル化による.
- ベンゾキシシロールの合成有用性を,フェノールとビアリルに変換することによって実証.
結論:
- オーソシライレーションのための新しい効率的な戦略が確立されています.
- ヒドロキシル誘導のC-H活性化により,ベンゾキシシロールへの多用途な経路が提供されます.
- 開発された方法は,機能化された芳香化合物を合成するための貴重な経路を提供します.
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.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
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.
02:36Regioselectivity and Stereochemistry of Hydroboration
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.
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
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...