ボロンの活性化効果により,コバルト触媒による非対称なアルケンの水素化が可能
Peter Viereck1, Simon Krautwald1, Tyler P Pabst1
1Department of Chemistry , Princeton University , Princeton , New Jersey 08544 , United States.
Journal of the American Chemical Society
|February 4, 2020
まとめ
非対称な1,1-二ボリルアルケンの高度なエナチオ選択的水素化はコバルト触媒を用いて達成された. これは,さらなる合成のための価値あるエナチオ濃縮されたディボリラクランの構成要素を生成します.
科学分野:
- 有機金属化学
- カタリシス
- 有機合成
背景:
- 1,1-ジボリルアルケンは,多用途の合成中間物質である.
- 変換のためのエナチオ選択的方法の開発は,キラル分子にアクセスするために不可欠です.
研究 の 目的:
- 非対称な1,1-ジボリルアルケンのエナチオ選択的水素化のための触媒システムを開発する.
- 触媒活性と選択性に対するボロン置換物の影響を調査する.
主な方法:
- C1対称ピリジン ((ダイミン)) コバルト複合体を用いて非対称の1,1-ジボリルアルケンの水素化.
- 基質置換剤効果の体系的な研究
- 反応メカニズムの解明のためのデウテリウムラベル研究.
主要な成果:
- 1,1-二ボリルアルケンの範囲で高い収量とエナチオ選択性が得られた.
- ステリカルに負荷を負わないボロ酸塩 (-BDan, -BCat, -Beg) は,不可逆的なα-ボロン方向の挿入経路を通じて水素化を促進することが判明した.
- 2つの異なるボロン置換剤を持つキラル中間物質は,デウテリウムラベリング研究によって特定されました.
結論:
- C1対称のPDIコバルト複合体は,非対称の1,1-ジボリルアルケンのエナチオ選択的水素化のための効果的な触媒である.
- ボロンの置換剤の性質は,触媒の効率とメカニズムに大きな影響を及ぼします.
- この研究により,非対称合成に有用な,エナチオ濃縮のディボリルカンの構成要素が得られます.
さらに関連する動画
関連する概念動画
02:36Regioselectivity and Stereochemistry of Hydroboration
9.3K
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.
9.3K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
20.5K
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.
20.5K
03:08Hydroboration-Oxidation of Alkenes
10.8K
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.
10.8K
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
3.8K
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...
3.8K
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
8.9K
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.
8.9K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
3.9K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
3.9K