非機能化された内部アルケンの非対称的水素形成のための閉じ込められたロジウム触媒の自己組み立て
Tendai Gadzikwa1, Rosalba Bellini, Henk L Dekker
1van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
Journal of the American Chemical Society
|January 28, 2012
まとめ
新種のキラル上分子リガンドは,内部アルケンの非対称的水酸化を可能にします. この触媒は,キラルポケット内の金属センターを制御することによって,高いエナチオセレクティビティを達成します.
科学分野:
- 有機金属化学 有機金属化学
- アシンメトリック・カタリシス
- 超分子化学 超分子化学
背景:
- 非対称な水酸化は,キラル化合物の合成に不可欠である.
- 非機能化された内部アルケンの触媒の開発は依然として困難です.
- 超分子リガンドは,触媒環境に対するユニークな制御を提供します.
研究 の 目的:
- 非対称な触媒のためのキラル上分子リガンドを組み立てる.
- 内部アルケンのロジウム触媒による水酸化合成におけるその応用を調査する.
- 高いエナチオセレクティビティを達成し,地域セレクティビティを制御する.
主な方法:
- 新型キラル上分子リガンドの合成と特徴付け.
- リガンドを用いたロジウム触媒による非対称な水酸化反応.
- 製品の地域選択性とエナチオ選択性の分析.
主要な成果:
- 組み立てられたキラル上分子リガンドが成功して合成されました.
- リガンドは,無機能化された内部アルケンのロジウム触媒による非対称的水酸化を容易にした.
- キラルポケット内の空間的閉じ込めは,逆の地域選択性をもたらしました.
- 顕著な反選択性が達成されました.
結論:
- チラルの上分子リガンドは,非対称な触媒を効果的に制御することができます.
- このアプローチは,価値ある化学的中間物質のエナチオセレクティブ合成のための新しい戦略を提供します.
- 開発された触媒は,微細化学合成における産業用途の有望性を示しています.
関連する概念動画
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.
02:13Reduction of Alkenes: Catalytic Hydrogenation
Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the surface of...
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.
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Introduction
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.