Dakin oxidation

Dakin oxidation is a chemical reaction that involves the oxidative cleavage of phenols and aromatic or aliphatic aldehydes, in the presence of hydrogen peroxide, to form benzenediols and diketones, respectively. This reaction is named after Henry Drysdale Dakin, a British chemist who first described the process in the early 20th century. The Dakin oxidation is particularly significant in the field of organic chemistry for its utility in the selective cleavage and functionalization of aromatic compounds, making it a valuable tool in the synthesis of complex organic molecules.

Mechanism

The mechanism of the Dakin oxidation involves several key steps. Initially, the phenol or aldehyde substrate reacts with hydrogen peroxide, forming a hydroperoxy intermediate. This intermediate then undergoes a series of rearrangements and cleavages, facilitated by the presence of a base, to yield the final benzenediol or diketone product. The choice of base, typically a weak base such as sodium carbonate (Na2CO3) or bicarbonate (NaHCO3), is crucial for the reaction's selectivity and yield.

Applications

The Dakin oxidation has found widespread application in the synthesis of pharmaceuticals, agrochemicals, and natural products. Its ability to selectively cleave and functionalize aromatic compounds makes it a valuable tool in the construction of complex molecular architectures. Additionally, the reaction's mild conditions and use of hydrogen peroxide, a relatively benign oxidant, make it attractive from a green chemistry perspective.

Variants

Several variants of the Dakin oxidation exist, each tailored to specific types of substrates or desired outcomes. These include the Dakin-West reaction, which is applied to amino acids and peptides to yield α-keto acids and amides, and the Baeyer-Villiger oxidation, which, although not a direct variant, shares conceptual similarities in the oxidative cleavage of substrates.

Limitations

Despite its utility, the Dakin oxidation has limitations. The reaction's selectivity can be influenced by the presence of substituents on the aromatic ring, potentially leading to a mixture of products. Additionally, the reaction conditions may not be suitable for substrates sensitive to oxidative conditions or basic environments.

See Also

• Phenol
• Aldehyde
• Hydrogen peroxide
• Organic synthesis
• Green chemistry

References

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  Dakin oxidation overall scheme

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  Dakin oxidation base-catalyzed mechanism

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  Hydrogen bond stabilization of Dakin oxidation substrate

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  Dakin oxidation by-product

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  Good migration

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  Bad migration 1

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  Bad migration

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  Dakin oxidation acid-catalyzed mechanism