反应性和分子识别:由内向 Ester 进行氨基甲基化
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
概括
这项研究详细介绍了一种宿主分子与三级氨基发生反应,形成一个显著加速反应速度的复合物. 这种超分子效应使反应速度提高了2万倍以上.
科学领域:
- 超分子化学 超分子化学
- 有机反应机制 有机反应机制
- 主机和客人的化学反应
背景情况:
- 具有向内定向的功能组的宿主分子可以影响化学反应.
- 三级胺是有机合成中常见的核.
- 超分子化学为反应速度加速提供了机会.
研究的目的:
- 为了研究具有甲基和各种三级胺的宿主分子之间的反应.
- 为了描述由此产生的宿主-客人复合体.
- 确定动力参数并了解超分子辅助反应加速的机制.
主要方法:
- 主体分子的合成和表征.
- 使用一系列三级胺的反应监测.
- 宿主和2- ((dimethylamino) 乙醇之间的反应的动态分析.
- 激活参数的确定 (和).
主要成果:
- 主体-客体复合物形成在主体碳酸盐和客体四级氨盐之间.
- 反应速率高度依赖于氨基在宿主腔内的固体适合性.
- 动力学研究产生了激活参数:DeltaH = 25.1 ± 0.5 kcal mol−1,DeltaS = 12 ± 2 cal mol−1 K−1.1,DeltaS = 12 ± 2 cal mol−1 K−1.
- 由于超分子效应,观察到估计速度加速>2 x 104倍.
结论:
- 主体分子有效地结合了三级胺,形成了一个促进产品形成的复合物.
- 与未催化反应相比,超分子复合显著提高了反应速率.
- 观察到的速度加速归因于反应物的预组织在宿主腔内的过渡状态.
相关概念视频
01:12Acid 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:
01:13Esters 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...
01:08Esters 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...
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...
01:19α-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.’
01:08Esters 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...
01:13Carboxylic 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.