Algar–Flynn–Oyamada reaction

The Algar–Flynn–Oyamada reaction is a chemical reaction whereby a chalcone undergoes an oxidative cyclization to form a flavonol.

Reaction mechanism

There are several possible mechanisms to explain this reaction; however, these reaction mechanisms have not been elucidated. What is known is that a two-stage mechanism exists. First, dihydroflavonol is formed, which then subsequently oxidizes to form a flavonol.

Proposed mechanisms involving epoxidation of the alkene have been disproven.

The probable mechanisms are thus two possibilities:

• The phenoxide attacks the enone at the beta position, and the alkene directly attacks hydrogen peroxide from the alpha position, forming the dihydroflavonol.
• The phenoxide attacks the enone at the beta position, closing the six-membered ring and forming an enolate intermediate. The enolate then attacks hydrogen peroxide, forming the dihydroflavonol.

See also

• Allan–Robinson reaction
• Auwers synthesis

References