Baylis-Hillman reaction

What is Baylis-Hillman reaction?

The Baylis-Hillman reaction involves the catalytic coupling of activated vinyl systems with aldehydes, resulting in the production of α-hydroxyalkylated or α-arylated products, with 1,4-diazabicyclo[2.2.2]octane (DABCO) typically used as the catalyst.

Baylis-Hillman reaction
Baylis-Hillman reaction

The Baylis-Hillman reaction was first described by John Baylis and Anthony Hillman in the 1970s, and it has since become a widely used method for the synthesis of a variety of compounds..

The general equation for the Baylis-Hillman reaction is as follows:

R-C(=O)-R’ + CO2 + organocatalyst → R-C(O)-O-R’ + H2O

In this equation, R and R’ represent alkyl or aryl groups. The organocatalyst, which is typically an amine or an imine, facilitates the reaction by activating the carbon dioxide molecule and coordinating with the aldehyde or ketone..

The Baylis-Hillman reaction is a useful method for the synthesis of alkyl and aryl alkyl carbonates because it allows for the introduction of a carbonate group into a molecule without the need for expensive and potentially hazardous reagents, such as phosgene. It is also a useful alternative to traditional methods for the synthesis of alkyl and aryl alkyl carbonates, such as the carbonylation of alcohols..

There are several variations of the Baylis-Hillman reaction, including the use of different organocatalysts, such as triethylamine and pyrrolidine, and the use of different solvents, such as dimethylformamide and dimethylsulfoxide..

Summary

The Baylis-Hillman reaction is a widely used and versatile chemical reaction that plays an important role in the synthesis of a variety of compounds..

Example

One example of the Baylis-Hillman reaction is the conversion of cyclohexanone to 1,6-hexanediol carbonate..

Cyclohexanone can be converted to 1,6-hexanediol carbonate through the following reaction:

cyclohexanone + CO2 + triethylamine → 1,6-hexanediol carbonate + H2O

In this reaction, triethylamine serves as the organocatalyst, and cyclohexanone is converted into 1,6-hexanediol carbonate through the introduction of a carbonate group..

This reaction is typically carried out in the presence of a solvent, such as dimethylformamide or dimethylsulfoxide, and the progress of the reaction can be monitored through the use of gas chromatography or infrared spectroscopy..

1,6-Hexanediol carbonate is a valuable chemical intermediate that is used in the synthesis of a wide range of compounds, including plastics, fragrances, and flavors. The Baylis-Hillman reaction is a useful method for the synthesis of 1,6-hexanediol carbonate from cyclohexanone, and it is often used on a large scale in the chemical industry..

Mechanism of reaction

The mechanism of the Baylis-Hillman reaction involves several steps. The overall reaction is the conversion of an aldehyde or ketone into an alkyl or aryl alkyl carbonate through the use of an organocatalyst and a carbon dioxide source..

The first step of the mechanism is the coordination of the organocatalyst, typically an amine or an imine, with the aldehyde or ketone. This step typically involves the formation of a complex between the organocatalyst and the aldehyde or ketone..
In the second step, the organocatalyst activates the carbon dioxide molecule and coordinates with it, forming a carbonate adduct..
In the third step, the carbonate adduct undergoes an intramolecular nucleophilic attack on the aldehyde or ketone, resulting in the formation of an alkyl or aryl alkyl carbonate..
In the final step, the alkyl or aryl alkyl carbonate is released from the organocatalyst, resulting in the formation of the final product..
Overall, the mechanism of the Baylis-Hillman reaction involves the coordination of the organocatalyst with the aldehyde or ketone, the activation of carbon dioxide by the organocatalyst, and the intramolecular nucleophilic attack of the carbonate adduct on the aldehyde or ketone. This reaction is typically carried out in the presence of a solvent, such as dimethylformamide or dimethylsulfoxide, and it requires the presence of an organocatalyst to facilitate the reaction..

References

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