Modifications in the iodine oxidation of hydroxy flavanones and their methyl ethers

Summary

A modified procedure for the action of iodine and silver acetate gives rise to purer products. Agreeing with earlier observations, hesperetin gives a good yield of 3-acetoxy hesperetin and hesperetin 7∶3′-dimethyl ether yields the 3-iodo-compound. The iodoflavanones invariably yield the corresponding flavones by the action of pyridine. In the treatment with alcoholic potash, those which have a free 5-hydroxyl,e.g., 3-iodo naringenin 7∶4′-dimethyl ether and 3-iodo hesperetin 7∶3′-dimethyl ether yield only the corresponding flavones; whereas 3-iodo-5∶7-dimethoxy flavanone having no free 5-hydroxyl group gives a mixture of products, containing the flavone, the flavonol and the 2-hydroxy-2-benzyl 4∶6-dimethoxy coumaranone. The difference seems to depend on the stability of the oxygen ring.