Algar–Flynn–Oyamada reaction

The Algar - Flynn - Oyamada reaction is a chemical reaction in the field of organic chemistry. It is used in the synthesis of flavonols ( derivatives of flavones with an additional hydroxy group ) of chalcones. The reaction proceeds under oxidising conditions in basic medium using hydrogen peroxide as oxidizing agent.

Mechanism

There are several mechanisms to explain the reaction possible, but which the reaction follows has not been elucidated. It is known that a two-step mechanism is present, in which first a dihydroflavonol is formed, which is then oxidized to the flavonol. Those mechanisms can be eliminated, which run over a epoxidisches intermediate which can be formed in a Prileschajew reaction by oxidation of the double bond with hydrogen peroxide. As a probable mechanisms there are thus two possibilities:

• The nucleophilic attack of the phenolate formed by base on the double bond under direct attack at the hydrogen peroxide.
• Nucleophilic attack of the phenolate to form an enolate, which then acts on hydrogen peroxide.