Chapter 15
α-Carbon Chemistry: Enols, Enolates, and Enamines
烯醇的反应性
Enols are a class of compounds where a hydroxyl group is attached to a carbon–carbon double bond, which implies that it is a vinyl alcohol. A ...
烯醇化根离子的反应性
Enolate ions are formed by the acid–base reaction of a carbonyl compound with a base. This leads to deprotonation of the α hydrogen atom, ...
烯醇和烯醇酸盐的类型
Aldehydes and ketones form enols, although only about 1% of the enol is present at the equilibrium for simple monocarbonyl compounds. The enol form is ...
烯醇化机制约定
When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an ...
烯醇酸盐的区域选择性形成
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, ...
烯醇化的立体化学效应
The chiral α-carbon of the carbonyl compound is the stereocenter of the molecule. As shown in the figure below, when such a carbonyl compound ...
醛和酮的酸催化 α-卤化反应
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first ...
醛和酮的碱促进α卤化
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. ...
甲基酮的多次卤化:卤仿反应
A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with ...
羧酸衍生物的 α-卤化:概述
Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, ...
羧酸的 α-溴化反应:Hell-Volhard-Zelinski 反应
The method to achieve α-brominated carboxylic acids using a mixture of phosphorus tribromide and bromine is known as the ...
α-卤羰基化合物的反应:亲核取代
Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out ...
烯醇的亚硝化
The nitrosation reaction is one of the methods of preparing 1,2-diketones. The enol tautomer of the starting ketone reacts with sodium nitrite in ...
C-C 键形成:羟醛缩合概述
Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. ...
碱催化的 Aldol 加成反应
As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy ...
酸催化的 Aldol 加成反应
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The ...
醛醇脱水为 Enals:碱催化的 Aldol 缩合
This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy ...
羟醛脱水为烯酮:酸催化羟醛缩合
As shown in Figure 1, under acidic conditions, the β-hydroxy ketone undergoes dehydration via an E1 elimination reaction to form an enone.
Figure 1. ...
分子内羟醛反应
Intramolecular aldol reaction occurs in dicarbonyl compounds such as dialdehydes, diketones, and keto-aldehydes. The dicarbonyl compounds possess more ...
C-C 键裂解:逆醛反应
The reverse of the aldol addition reaction is called the retro-aldol reaction. Here, the carbon–carbon bond in the aldol product is cleaved under ...
交叉 Aldol 反应:概述
Crossed aldol addition is the reaction between two different carbonyl compounds under acidic or basic conditions. Here, both the carbonyl compounds ...
使用弱碱的交叉羟醛反应
This lesson deals with the crossed aldol reaction using weak bases. The self-condensation of an aldehyde having α hydrogen is prevented by adding it ...
具有不可烯醇化芳香醛的酮:Claisen-Schmidt 缩合反应
Benzaldehyde, like formaldehyde, lacks an α hydrogen and cannot enolize to form an enolate. Hence, the reaction of benzaldehyde with a ketone in the ...
使用强碱的交叉 Aldol 反应:定向 Aldol 反应
The reaction between two different carbonyl compounds comprising α hydrogen in the presence of a strong base like lithium diisopropylamide (LDA) to ...
醛缩合与 β-二酯:Knoevenagel 缩合
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as ...
酯到 β-酮酯:Claisen 缩合概述
Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It ...
酯到 β-酮酯:Claisen 缩合机制
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the ...
Aldol 冷凝与 Claisen 冷凝
Aldol condensation is an acid or base-catalyzed condensation between aldehydes or ketones to give an α,ꞵ-unsaturated carbonyl compound. A ...
二羧酸酯的分子内 Claisen 缩合:Dieckmann 环化
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic ...
β-二羰基化合物通过交叉 Claisen 缩合
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction ...
酮的α-烷基化通过烯醇化离子
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by ...
影响酮α烷基化的因素:碱的选择
α-Alkylation of ketones is achieved in the presence of alkyl halides and a base. The reaction proceeds via the formation of an enolate ion followed ...
β-酮酯烯醇化物的烷基化反应:乙酰乙酸酯合成
Acetoacetic ester synthesis is a method to obtain ketones from alkyl halides and β-keto esters. The reaction occurs in the presence of an alkoxide ...
β-二酯烯醇化物的烷基化反应:丙二酸酯合成
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
The ...
α，β-不饱和羰基化合物的偶联加成反应
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in ...
共轭加成法（1,4 加法）与直接加法（1,2 加法）
α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic ...
烯醇酸盐的共轭加成:Michael Addition
The attack of a nucleophile at the β carbon of an α,β-unsaturated carbonyl compound is called conjugate addition. Conjugate addition ...
通过 Michael Addition 和 Aldol condensation 的环己酮:Robinson 环环
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, ...
α取代羰基化合物的合成:Stork Enamine 反应
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines ...
不可烯醇化醛对酸和醇的影响:Cannizzaro 反应
The Cannizzaro reaction is a base-promoted redox reaction producing a primary alcohol and a carboxylic acid from two molecules of a nonenolizable ...
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