キラルアリルエステルの触媒的非対称合成
Stefan F Kirsch1, Larry E Overman
1Department of Chemistry, 516 Rowland Hall, University of California, Irvine, California 92697-2025, USA.
Journal of the American Chemical Society
|March 3, 2005
まとめ
チラル3-アシロキシ-1-アルケンは,新しいパラジウム触媒を使用して,プロキラルアルケノールから合成されます. この効率的なエナチオセレクティブ反応は,高いステレオコントロールで室温で発生します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- アシンメトリック・シンセシス
- 有機金属化学 有機金属化学
背景:
- プロキラル (Z) - 2 - アルケン - 1 - オールは,貴重な合成中間物質です.
- エナチオセレクティブ変換のための効率的な触媒方法の開発は,有機合成において極めて重要です.
研究 の 目的:
- キラル型3-アシロキシ-1-アルケンのエナンチオセレクティブ合成のための新しい触媒システムを開発する.
- この新しい変容の範囲とメカニズムを調査する.
主な方法:
- プロキラル (Z) - 2 - アルケン-1-オールのトリクロアセチミダート誘導体のカルボキシル酸との反応.
- キラルなパラジウム触媒を用いて,ディ-ミュ-アセタトビス ([(eta5-(S) - (((pR) - 2 - (((2'- (((4'-メチルエチル) オキサゾリニル) サイクロペンタディエニル,1-C,3'-N) (((eta4-テトラフェニルサイクロブタディエネ) コバルト]ディパラジウム (COP-OAc) またはそのエナティオメールを使用する.
主要な成果:
- キラル型3-アシロキシ-1-アルケンの高いエナンチオ純度が達成されました.
- この反応は,広範囲の基質範囲と予測可能な高いステレオインダクションを示した.
- このプロセスは効率的で,室温で,高い基板濃度と低い触媒負荷で動作します.
結論:
- キラル3-アシロキシ-1-アルケンのエナンチオセレクティブ合成のための新しい効率的な方法が確立されています.
- この反応は,新しい触媒メカニズムを通じて進行する可能性があるため,さらなる調査が必要である.
関連する概念動画
Acid Halides to Esters: Alcoholysis
Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis
Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Esters to β-Ketoesters: Claisen Condensation Overview
Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It is a nucleophilic acyl substitution reaction wherein one of the ester molecules, upon deprotonation by the base, forms a nucleophilic enolate ion, while the other molecule serves as an electrophile.
β-Dicarbonyl Compounds via Crossed Claisen Condensations
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction involving esters, with both containing α hydrogen, results in a mixture of four different products that are difficult to isolate. This reduces the synthetic utility of the reaction.
Esters to β-Ketoesters: Claisen Condensation Mechanism
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...
Carboxylic Acids to Esters: Acid-Catalyzed (Fischer) Esterification Mechanism
Carboxylic acids react with alcohols to yield esters via an acid-catalyzed condensation reaction called Fischer esterification. This is a nucleophilic acyl substitution reaction that proceeds via a tetrahedral intermediate, where a water molecule is eliminated as the leaving group.


