三置換アルケンのアミド誘導的触媒非対称水酸化
1Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0304, USA.
Journal of the American Chemical Society
|January 23, 2010
まとめ
三置換アルケンのロジウム触媒化水酸化は,β,ガンマ不飽和アミドを使用して改善されます. この方法はステレオスペシフィックでエナチオセレクティブで,キラルなオルガノボラン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
背景:
- 三置換アルケンのロジウム触媒化ヒドロボレーションは,しばしば遅いものであり,イソメリ化の傾向があります.
- ベータ,ガンマ不飽和アミドは,触媒変換のためのユニークな基板クラスです.
研究 の 目的:
- ベータ,ガンマ不飽和アミドのフレームワーク内の三置換アルケンのロジウム触媒化水酸化を調査する.
- この新しい触媒システムのステレオスペシフィシティとエナチオセレクティビティを探求する.
主な方法:
- TADDOL由来のフェニルモノフォスフィートリガンドを含むロジウム触媒を用いて.
- ロジウムの前駆体としてRh ((nbd) ((2) BF ((4) を使用しています.
- 反応する (E) -と (Z) -3のステレオアイソメリック基板.
主要な成果:
- ベータ,ガンマ不飽和アミドにおける三置換アルケンの容易な水酸化は,おそらくカルボニル誘導効果とバイデント酸基板結合によるものである.
- (E) - と (Z) - 3同位体からダイアステロエーマー産物のステレオ特異的形成.
- 特定のリガンドの組み合わせで達成される高エナチオセレクティブ性 (91-98% ee).
結論:
- アミド中の三置換アルケンの高効率でステレオ特異的なロジウム触媒による水酸化を開発した.
- 高いエナチオセレクティビティを達成するためにTADDOL由来リガンドの有用性を実証しました.
- アルドール産物合成のための有価なキラルオルガンボランへの新しい合成経路を提供した.
さらに関連する動画
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.
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.
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
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.
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.