1,4-アザボリンベースのフォスフィン-Pd複合体によって触媒化された1,3-エニネスのサイト選択的およびステレオ選択的トランス水酸化
Senmiao Xu1, Yuanzhe Zhang1, Bo Li1
1Department of Chemistry, Boston College , Chestnut Hill, Massachusetts 02467-3860, United States.
Journal of the American Chemical Society
|November 2, 2016
まとめ
新しいセンフォスリンガンドは,エニンの効率的なパラジアム触媒トランスヒドロボレーションを可能にします. この反応は,高ステレオ選択性を持つデニルボロナートを生成し,BN/CCイソステリズムが触媒作用において有用であることを示した.
科学分野:
- 有機金属化学
- カタリシス
- 合成有機化学
背景:
- パラジウム触媒反応は有機合成において極めて重要です.
- 新しいリガンドの開発は,触媒の効率と選択性を向上させるための鍵です.
- ハイドロボレーション反応は,機能化された有機分子への多用途な経路を提供します.
研究 の 目的:
- 新しいモノベンゾを合成するために1,4-アザボリン・フォスフィン・リガンド (Senphos) を混ぜた.
- パラジウム触媒変換における Senphos リガンドの有用性を調査する.
- エニンからデニルボロナートのステレオ選択的合成を調査する.
主な方法:
- センフォス結合体の合成
- ターミナルおよび内部1,3-エニンのパラジウム触媒によるトランスセレクティブ水酸化.
- センフォス-Pd0複合体のX線構造分析
- 分離された複合体の触媒試験
主要な成果:
- センフォスのリガンドは簡潔に合成された.
- エニンのトランスヒドロボレーションでは高効率と二重選択性が達成された.
- Senphos-Pd(0) 複合体では独特の κ2-P-η2-BC 調整モードが観察されました.
- 隔離された複合体は,トランス・ヒドロボレーションのための触媒活性を示した.
結論:
- Senphos リガンドは,Pd触媒によるトランス選択的水酸化において有効である.
- BN/CCイソステリズムアプローチは,ステレオ選択的触媒の化学空間を拡大する.
- この研究は,価値あるデニルボロナートを合成するための新しい触媒システムを提供します.
関連する概念動画
02:36Regioselectivity and Stereochemistry of Hydroboration
9.6K
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.
9.6K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
4.3K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
4.3K
03:08Hydroboration-Oxidation of Alkenes
12.0K
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.
12.0K
02:35Regioselectivity of Electrophilic Additions-Peroxide Effect
11.4K
In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.
11.4K
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
21.7K
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.
21.7K
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
18.1K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
18.1K