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β-Dicarbonyl Compounds via Crossed Claisen Condensations

β-Dicarbonyl Compounds via Crossed Claisen Condensations

Crossed Claisen condensations are base-promoted reactions between two different ester molecules producing β-dicarbonyl compounds. The reaction involving esters, with both containing α hydrogen, results in a mixture of four different products that are difficult to isolate. This reduces the synthetic utility of the reaction.

Esters to β-Ketoesters: Claisen Condensation Mechanism

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...

Esters to β-Ketoesters: Claisen Condensation Overview

Esters to β-Ketoesters: Claisen Condensation Overview

Regular Claisen condensation is a base-promoted reaction involving identical esters with two α hydrogens, condensing to produce β-ketoesters. It is a nucleophilic acyl substitution reaction wherein one of the ester molecules, upon deprotonation by the base, forms a nucleophilic enolate ion, while the other molecule serves as an electrophile.

Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization

Intramolecular Claisen Condensation of Dicarboxylic Esters: Dieckmann Cyclization

Dieckmann cyclization is an intramolecular Claisen condensation of diesters. The reaction occurs in the presence of a base and generates a cyclic β-ketoester as the final product. Commonly, 1, 6 and 1, 7-diesters are preferred substrates for the reaction since the generated five, and six-membered cyclic β-keto esters are particularly more stable.

Types of Step-Growth Polymers: Polyesters

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The introduction of polyesters has brought major development to the textile industry. The wrinkle-free behavior of polyester blends has eliminated the need for starching and ironing clothes.
Polyesters are commonly prepared from terephthalic acid and ethylene glycol; the crude product is known as poly(ethylene terephthalate) or PET. However, polyesters are synthesized industrially by transesterification of dimethyl terephthalate with ethylene glycol at 150 °C. The two reactants and the polymer...

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

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.’

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Related Experiment Video

Updated: Nov 3, 2025

Preparation of Gynura bicolor DC samples for High-Resolution Tandem Mass Spectrometry

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Three new sesquiterpene polyol esters from Celastrus angulatus.

Wei Zhao¹, Xia Chang², Hang Yuan²

¹High & New Technology Research Center of Henan Academy of Science, Zhengzhou 450002 PR China.

Journal of Asian Natural Products Research

|June 7, 2021

Summary

Researchers discovered three new sesquiterpene polyol esters, angulatins S-U, from Celastrus angulatus. These compounds were structurally identified using advanced nuclear magnetic resonance (NMR) techniques.

Keywords:

Celastraceae Celastrus angulatus angulatin S angulatin T angulatin U sesquiterpene polyol ester

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Area of Science:

Natural Product Chemistry
Organic Chemistry
Phytochemistry

Background:

Celastrus angulatus Maxim. is a plant source of bioactive compounds.
Sesquiterpene polyol esters are a class of natural products with diverse biological activities.

Purpose of the Study:

To isolate and structurally elucidate new compounds from Celastrus angulatus.
To characterize the chemical constituents of Celastrus angulatus.

Main Methods:

Isolation of compounds using chromatographic techniques.
Structure determination primarily through 1D Nuclear Magnetic Resonance (NMR) and 2D NMR analysis.

Main Results:

Three new sesquiterpene polyol ester compounds, named angulatins S, T, and U, were isolated.
The structures were fully elucidated, revealing complex esterification patterns on a β-dihydroagarofuran skeleton.
Three known compounds were also identified.

Conclusions:

The study expands the known chemical diversity of sesquiterpene polyol esters from Celastrus angulatus.
The detailed structural information provides a basis for further investigation into the biological activities of these novel compounds.