Baker–Venkataraman rearrangement

Baker–Venkataraman rearrangement is a significant chemical reaction that involves the rearrangement of acyl phenols into aryl ketones. This reaction is pivotal in organic chemistry, especially in the synthesis of flavones and coumarins, which are essential compounds in pharmaceuticals, agrochemicals, and dyestuffs. The Baker–Venkataraman rearrangement is named after the chemists W. S. Baker and K. Venkataraman, who developed this reaction.

Mechanism

The mechanism of the Baker–Venkataraman rearrangement begins with the formation of an ester from the acyl phenol by reaction with an acyl chloride or anhydride in the presence of a base. This ester then undergoes an intramolecular nucleophilic acyl substitution, facilitated by the base, to form a ketene acetal. Finally, hydrolysis of the ketene acetal yields the aryl ketone product. The overall process transforms the acyl group from the phenolic oxygen to the ortho carbon atom of the aromatic ring, effectively rearranging the molecule.

Applications

The Baker–Venkataraman rearrangement has been widely used in the synthesis of complex organic molecules. Its ability to convert acyl phenols into aryl ketones makes it a valuable tool in the construction of heterocyclic compounds, such as flavones and coumarins, which have diverse biological activities. These compounds are found in many natural products and have applications in medicine, such as in the treatment of cancer and cardiovascular diseases, as well as in agrochemicals and dyestuffs.

Variations

Several variations of the Baker–Venkataraman rearrangement exist, which involve different conditions or catalysts to improve the yield or selectivity of the reaction. For example, the use of different bases or solvents can significantly affect the outcome of the reaction. Additionally, microwave-assisted and ultrasonic conditions have been explored to enhance the efficiency of the rearrangement.

See also

• Flavone synthesis
• Coumarin
• Organic synthesis
• Nucleophilic acyl substitution