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Mn複合体によって触媒化された非活性化原C-H結合の誘導型γ-乳酸化:ステレオ選択的天然産物多様化への応用

  • 0Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17003, Catalonia, Spain.
Journal of the American Chemical Society +

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2022年10月13日

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Alkylation of β-Diester Enolates: Malonic Ester Synthesis 01:14

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Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.

The reaction proceeds via abstraction of the acidic α hydrogen from a ꞵ-diester to produce a doubly stabilized enolate ion. The nucleophilic enolate attacks the alkyl halide in an SN2 manner to form an alkylated malonic ester intermediate with a new C–C bond. Further treating the intermediate with aqueous acid or base results in...

Acid-Catalyzed α-Halogenation of Aldehydes and Ketones 01:21

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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...

α-Alkylation of Ketones via Enolate Ions 01:10

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Ketones with α protons are deprotonated by strong bases like lithium diisopropylamide (LDA) to form enolate ions. The anion is stabilized by resonance, and its hybrid structure exhibits negative charges on the carbonyl oxygen and the α carbon. This ambident nucleophile can attack an electrophile via two possible sites: the carbonyl oxygen, known as O-attack, or the α carbon, known as C-attack. The nucleophilic attack via the carbanionic site is preferred. This is due to the...

α-Halogenation of Carboxylic Acid Derivatives: Overview 01:14

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Unlike aldehydes and ketones, carboxylic acids do not readily participate in α halogenation reactions via enols or enolate intermediates. However, α-halogenated acids are obtained through other methods. One of the approaches is the Hell–Volhard–Zelinsky (HVZ) reaction, wherein the carboxylic acid is treated with halogen in the presence of PBr3. It involves the conversion of acid to acid halide, which exists in equilibrium with its enol form. The enol attacks the...

Preparation of Carboxylic Acids: Carboxylation of Grignard Reagents 01:13

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Carboxylic acids can be prepared by the carboxylation of Grignard reagents (RMgX). This method is convenient for converting alkyl (primary, secondary or tertiary), vinyl, benzyl, and aryl halides to carboxylic acids with one additional carbon than the starting RMgX.

The carboxylation mechanism involves two steps. In the first step, the nucleophilic attack of the Grignard reagent on the electrophilic site of the carbon dioxide generates the magnesium salt of the carboxylate ion. In the...

Acid-Catalyzed Aldol Addition Reaction 01:15

2.7K

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.

Figure 1. The acid-catalyzed aldol addition reaction of ketones.
First, as shown in Figure 2, the acid protonates the ketone molecule to form the protonated ketone. The conjugate base of the acid deprotonates the α carbon of the protonated ketone to form the enol.

Figure 2. Formation of the enol.