Chapter 15
α-Carbon Chemistry: Enols, Enolates, and Enamines
Реакционная способность энолов
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 ...
Реакционная способность ионов енолирования
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, ...
Виды энолов и энолатов
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 ...
Конвенции механизма Enolate
When a carbonyl compound is treated with a strong base, the α position gets deprotonated to give a resonance-stabilized intermediate called an ...
Региоселективное образование энолатов
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, ...
Стереохимические эффекты энолизации
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 ...
Катализируемое кислотой α-галогенирование альдегидов и кетонов
By replacing an α-hydrogen with a halogen, acid-catalyzed α-halogenation of aldehydes or ketones yields a monohalogenated product
In the first ...
Стимулируемое основаниями α-галогенирование альдегидов и кетонов
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. ...
Многократное галогенирование метилкетонов: галоформная реакция
A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with ...
α-Галогенирование производных карбоновой кислоты: обзор
Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, ...
α-Бромирование карбоновых кислот: реакция Хелла–Фольхарда–Зелинского
The method to achieve α-brominated carboxylic acids using a mixture of phosphorus tribromide and bromine is known as the ...
Реакции α-галокарбонильных соединений: нуклеофильное замещение
Nucleophilic substitution in α-halocarbonyl compounds can be achieved via an SN2 pathway. The reaction in α-haloketones is generally carried out ...
Нитрозирование энолов
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 ...
Образование C–C связей: обзор конденсации альдола
Aldol condensation is an important route in synthetic organic chemistry used to generate a new carbon–carbon bond under basic or acidic conditions. ...
Катализируемая основаниями реакция добавления алдола
As depicted in Figure 1, base-catalyzed aldol addition involves adding two carbonyl compounds in aqueous sodium hydroxide to form a β-hydroxy ...
Реакция кислотно-катализируемого присоединения алдола
The aldol reaction of a ketone under acidic conditions successfully forms an unsaturated carbonyl as the final product instead of an aldol. The ...
Обезвоживание альдол до эналов: катализируемая основаниями конденсация альдол
This lesson delves into the aldol condensation catalyzed by bases, where aldols undergo dehydration to enals. As shown in Figure 1, the β-hydroxy ...
Обезвоживание альдол до енонов: катализируемая кислотой конденсация альдола
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. ...
Внутримолекулярная альдольная реакция
Intramolecular aldol reaction occurs in dicarbonyl compounds such as dialdehydes, diketones, and keto-aldehydes. The dicarbonyl compounds possess more ...
С–С расщепление связи: ретро-алдоловая реакция
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 ...
Реакции Crossed Aldol: обзор
Crossed aldol addition is the reaction between two different carbonyl compounds under acidic or basic conditions. Here, both the carbonyl compounds ...
Перекрестная реакция Альдолы с использованием слабых оснований
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 ...
Кетоны с неенолизизируемыми ароматическими альдегидами: конденсация Клейзена–Шмидта
Benzaldehyde, like formaldehyde, lacks an α hydrogen and cannot enolize to form an enolate. Hence, the reaction of benzaldehyde with a ketone in the ...
Скрещенная реакция Альдола с использованием сильных оснований: направленная Альдольная реакция
The reaction between two different carbonyl compounds comprising α hydrogen in the presence of a strong base like lithium diisopropylamide (LDA) to ...
Конденсация альдола с β-диэфирами: конденсация Кневенагеля
The Knoevenagel condensation is an aldol-type reaction involving the condensation of aldehydes or ketones with active methylene compounds such as ...
Сложные эфиры в β-кетостеры: обзор конденсации Claisen
Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It ...
Сложные эфиры в β-кетостеры: механизм конденсации Claisen
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the ...
Конденсация альдола против конденсации Claisen
Aldol condensation is an acid or base-catalyzed condensation between aldehydes or ketones to give an α,ꞵ-unsaturated carbonyl compound. A ...
Внутримолекулярная конденсация дикарбоновых эфиров методом Клейзена: циклизация Дикмана
Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic ...
β-дикарбонильные соединения через скрещенные конденсаты Claisen
Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction ...
α-алкилирование кетонов с помощью ионов енолирования
Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by ...
Факторы, влияющие на α-алкилирование кетонов: выбор основания
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 ...
Алкилирование β-кетоэфирных енолатов: синтез ацетоуксусных эфиров
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 ...
Алкилирование β-диэфирных энолатов: синтез малоновых эфиров
Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.
The ...
Конъюгированное дополнение к α,β-ненасыщенным карбонильным соединениям
α,β-Unsaturated carbonyl compounds are molecules bearing a carbonyl and alkene functionality in conjugation with each other. The conjugation in ...
Сопряженное присоединение (1,4-присоединение) и прямое присоединение (1,2-присоединение)
α,β-Unsaturated carbonyl compounds with two electrophilic sites, the carbonyl carbon, and the β carbon, are susceptible to nucleophilic ...
Сопряженное присоединение энолатов: присоединение Михаила
The attack of a nucleophile at the β carbon of an α,β-unsaturated carbonyl compound is called conjugate addition. Conjugate addition ...
Циклогексеноны через добавление Майкла и конденсацию альдола: аннуляция Робинсона
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, ...
Синтез α-замещенных карбонильных соединений: реакция энамина аиста
α-Substituted ketones or aldehydes can be synthesized from enamines by the Stork enamine reaction, named after its pioneer Gilbert Stork. Enamines ...
Неенолизизируемые альдегиды до кислот и спиртов: реакция канниццаро
The Cannizzaro reaction is a base-promoted redox reaction producing a primary alcohol and a carboxylic acid from two molecules of a nonenolizable ...
Авторские права © 2025 MyJoVE Corporation. Все права защищены