イリジウム触媒によるトリメチルシロキシフランの地域選択性およびエナチオ選択性アリレーション
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|September 8, 2012
まとめ
イリジウム触媒を用いたトリメチルシロキシフランの地域およびエナチオ選択的アリレーションのための新しい方法を開発しました. この反応により,高エナティオメール純度を持つ有価な3-置換ブテノリドが生成されます.
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:
- エステルエノラートは,汎用性の高い合成中間物質です.
- 合成的に重要なことは,エナチオ濃縮の3置換ブテノリドへのアクセスです.
- 選択的機能化のための触媒的方法の開発は,有機合成の重要な目標です.
研究 の 目的:
- トリメチルシロキシフランの新たな地域およびエナチオセレクティブアリレーションを報告する.
- 3置換ブテノリドの合成のための触媒システムを開発する.
- アリレーション反応のメカニズムを調査する.
主な方法:
- メタラサイクリックイリジウム触媒の使用.
- トリメチルシロキシフーランとアリル炭酸塩またはベンゾ酸塩の反応.
- 反応産物の地域およびエナチオ選択性の分析.
主要な成果:
- 反応は,トリメチルシロキシフランの3位で選択的に発生した.
- 枝分かれした置換製品は,高エナティオメール濃縮で形成された.
- 多種多様な芳香性アリルカルボネートとアリファ性アリルベンゾアートを成功裏に使用しました.
- ステイキオメトリック研究では,カルボキシラート離脱群によるトリメチルシロキシフランの活性化が示された.
結論:
- 開発されたイリジウム触媒反応は,エンアンチオ濃縮の3置換ブテノリドに効率的なアクセスを提供します.
- この方法論は,複雑な有機分子を合成するための貴重なツールを提供します.
- カーボキシラート離脱基はフラン基板の活性化に重要な役割を果たします.
関連する概念動画
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.
01:13Electrophilic Aromatic Substitution: Fluorination and Iodination of Benzene
Bromination and chlorination of aromatic rings by electrophilic aromatic substitution reactions are easily achieved, but fluorination and iodination are difficult to achieve. Fluorine is so reactive that its reaction with benzene is difficult to control, resulting in poor yields of monofluoroaromatic products. To address this, Selectfluor reagent is used as a fluorine source in which a fluorine atom is bonded to a positively charged nitrogen.
02:26Preparation and Reactions of Sulfides
Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
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.
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.
02:17Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
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...