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アミドとアルデヒドの高度に反選択的な触媒アルドール反応
1Graduate School of Pharmaceutical Sciences, The University of Tokyo, The HFRE Division, ERATO, Japan Science Technology Agency (JST), Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Journal of the American Chemical Society
|July 6, 2006
まとめ
バリウムフェノキシドは,アミドとアルデヒドの間の直接アルドール反応を触媒化し,高い反選択性を達成します. この方法は,様々なアルデヒドを温和な条件下で作動させ,効率的に望ましい製品を得ることができます.
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:
- アルドール反応は,有機合成における炭素-炭素結合形成反応の基本です.
- アミドの直接アルドール反応は,従来の方法と比較して簡素化されたアプローチを提供します.
- 非常に選択的で効率的な触媒システムの開発は,依然として重要な課題です.
研究 の 目的:
- アミドとアルデヒドのバリウムフェノキシード触媒による直接アルドール反応の新型を開発する.
- 軽度の反応条件下での高反選択性および収量を達成するために.
- 開発された触媒システムの範囲と限界を探求する.
主な方法:
- 直接アルドール反応の触媒としてフェノキシドバリウムを使用した.
- 反応の円滑な進行を促進するために,わずかに余分なアミドを使用した.
- 多種多様な芳香性,異環性,α,β-不飽和アルデヒドの反応を研究した.
主要な成果:
- アミドとアルデヒドの高度に反選択的な直接アルドール反応を成功裏に開発した.
- 望ましいアルドール添加物に対する高収量と優れた反選択性を達成しました.
- アルデヒド基板の幅広いスペクトルに適用可能なことが実証されています.
- キラルリガンドを用いた触媒的エナンチオセレクティブの変種が報告されました.
結論:
- 酸化バリウムは,アミドの直接アルドール反応の効果的な触媒である.
- 開発された方法は,抗選択性アルドール製品への簡単で効率的な経路を提供します.
- 触媒的エナチオセレクティブアプローチは,この反応の合成的有用性を拡大します.
関連する概念動画
Relative Reactivity of Carboxylic Acid Derivatives
Carboxylic acid derivatives such as acid halides, anhydrides, esters, and amides undergo nucleophilic acyl substitution reactions with varying degrees of reactivity.
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
A key factor in assessing the reactivity of the acid derivatives is the basicity of the substituent or the leaving group. The lower the basicity of the leaving group, the higher the reactivity of the derivative. The basicity of the leaving group follows this order:
Halide ions < Acyloxy ions < Alkoxy ions < Amine ions
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:
Reactions of Acid Anhydrides
The reactions of acid anhydrides are analogous to the reactions of acid chlorides and proceed via a nucleophilic acyl substitution. They only differ in the identity of the leaving group. During an acid chloride reaction, the leaving group is a chloride ion, and the by-product is hydrochloric acid. However, in an acid anhydride reaction, the leaving group is a carboxylate ion, and the by-product is a carboxylic acid.
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
Acid Halides to Alcohols: Grignard Reaction
Organomagnesium halides, commonly known as Grignard reagents, convert acid halides to tertiary alcohols. The reaction requires two equivalents of the Grignard reagent and proceeds via a ketone intermediate.
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs,...
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs,...
Acid-Catalyzed Aldol Addition Reaction
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The acid-catalyzed aldol reaction is depicted in Figure 1.

