Oxidation of enol acetate of flavanone with thallium(III) nitrate or phenyliodonium diacetate: a convenient new route to isoflavone and flavone

A new high-yield method has been described for the preparation of isoflavone by oxidation of enol acetate of flavanone with thallium(III) nitrate or phenyli-odonium diacetate in trimethyl orthoformate in the presence of 70 % perchloric acid at room temperature. Flavone could also be prepared in high yield from the enol acetate by oxidation with the same reagents in glacial acetic acid at room temperature. Some key intermediates of these oxidations were investigated with quantum chemical (HF and DFT) methods.