Flavone oxidative degradation

Chromones are readily oxidized by permanganate or dichromate with opening of the pyran ring and the formation of a salicylic acid (402). Flavones and isoflavones are also degradatively oxidized for example oxidation of munetone (403) with alkaline hydrogen peroxide yields 2-methoxybenzoic acid and 4-hydroxy-2-isopropylbenzofuran-5-carboxylic (isotubaic) acid. 

However, in the last paper of this series, the degradation involving periodate oxidation of a methylated keyakinin to tangeritin was described, and tangeritin has been assigned the structure of 3,4, 5,6,7-pentamethoxy-flavone. But this structure has since been revised to 4, 5,6,7,8-penta-methoxyflavone and, presumably, the structures of keyakinin and keyakinol are now to be revised in accordance therewith. 

The most important yellow dye in ancient and medieval times was weld, a flavone derivative extracted from the seeds, stems, and leaves of Reseda luteola, commonly known as dyer s rocket. Weld is resistant to atmospheric oxidation, rendering it quite lightfast and hence extremely popular and useful. In combination with the blue dye woad it was used to produce the Lincoln green made famous by Robin Hood and his merry men. Quercitron, a flavonol derivative, is much more susceptible to degradation by light and hence was not as important [23]. 

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