反応性と分子認識:内向的なエステルによるアミンメチル化

Byron W Purse¹, Pablo Ballester, Julius Rebek

¹The Skaggs Institute for Chemical Biology and Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.

Journal of the American Chemical Society

|December 4, 2003

まとめ

この研究では,宿主分子が三次アミンと反応し,反応速度を大幅に加速する複合体を形成することを詳細に説明しています. この超分子効果は,反応速度を2万倍以上高めます.

科学分野:

超分子化学超分子化学
有機反応のメカニズム
ホスト・ゲスト・ケミストリー

背景:

内向きの機能群を持つ宿主分子は,化学反応に影響を与えることができます.
三次アミンは,有機合成における一般的な核愛素である.
超分子化学は,反応速度を加速させる機会を提供します.

研究の目的:

メチルエステルを持つ宿主分子と様々な三次アミンの間の反応を調査する.
その結果生じるホスト・ゲスト複合体を特徴づけるために.
運動パラメータを決定し,超分子補助反応加速の仕組みを理解する.

主な方法:

ホスト分子の合成と特徴付け.
一連の三次アミンの反応モニタリング.
宿主と2− (−) ディメチラミノエタノール.エタノールとの反応の運動分析.
活性化パラメータの決定 (エンタルピーとエントロピー).

主要な成果:

ホスト・ゲスト・コンプレックスは,ホスト・カルボキシラートとゲスト・四分位アンモニアム塩の間に形成される.
反応速度は,宿主腔内のアミンの固体適合性に大きく依存しています.
運動研究により,活性化パラメータが得られた:DeltaH = 25.1 ± 0.5 kcal mol−1,DeltaS = 12 ± 2 cal mol−1 K−1.1.
超分子効果による2x104倍以上の推定速度加速が観察されました.

結論:

宿主分子は三次アミンを効果的に結合し,製品形成を促進する複合体を形成します.
超分子複合は,触媒化されていない反応と比較して,反応速度を大幅に高めます.
観測された速度の加速は,宿主腔内の移行状態の反応物の事前組織化に起因する.

さらに関連する動画

06:52

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

Published on: October 30, 2018

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy

07:36

Versatile CO₂ Transformations into Complex Products: A One-pot Two-step Strategy

Published on: November 9, 2019

関連する概念動画

01:12

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:

01:13

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...

01:08

Esters to Alcohols: Grignard Reaction

The reaction of an ester with a Grignard reagent, followed by hydrolysis of the magnesium alkoxide salt in aqueous acid, yields a tertiary alcohol. In the case of formate esters, secondary alcohols are formed.
The reaction requires two equivalents of the Grignard reagent and introduces two identical alkyl groups, derived from the Grignard reagent, bonded to the hydroxyl-bearing carbon of the alcohol.
The reaction follows the typical nucleophilic acyl substitution mechanism. The Grignard...

01:19

α-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview

The pinacol and McMurry reactions involve the reductive coupling of ketones or aldehydes. Similarly, the bimolecular reductive coupling of two ester molecules in the presence of sodium metal in an aprotic solvent yields an α-hydroxy ketone product. The α-hydroxy ketone is also called acyloin, so the reaction is referred to as ‘acyloin condensation.’

01:08

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...

01:13

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.

関連する実験動画