Flavones

  Flavones are a class of flavonoids based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one) shown on the right.

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Natural flavones include Apigenin (4',5,7-trihydroxyflavone), Luteolin (3',4',5,7-tetrahydroxyflavone) and Tangeritin (4',5,6,7,8-pentamethoxyflavone). Synthetic flavones are Diosmin and Flavoxate

Organic chemistry

In organic chemistry several methods exist for the synthesis of flavones:

• the Allan-Robinson reaction
• the Auwers synthesis
• the Baker-Venkataraman rearrangement
• the Algar-Flynn-Oyamada reaction

Another method is the dehydrative cyclization of certain 1,3-diaryl diketones ^[1]

this particular study making use of an ionic liquid solvent and microwave irradiation.

Wessely-Moser rearrangement

The Wessely-Moser rearrangement (1930) ^[2] has been an important tool in structure elucidation of flavonoids. It involves the conversion of 5,7,8-trimethoxyflavone into 5,6,7-trihydroxyflavone on hydrolysis of the methoxy groups to phenol groups. It also has synthetic potential for example^[3]:

This rearrangement reaction takes place in several steps: A ring opening to the diketone, B bond rotation with formation of a favorable acetylacetone-like phenyl-ketone interaction and C hydrolysis of two methoxy groups and ring closure.

References