The action of iodine and silver acetate varies with the type of flavanones employed, and yields the intermediate stages postulated in the new flavone synthesis using iodine and sodium acetate. The polyhydroxyflavanones, naringenin and hesperetin form directly the 3-acetates which can be hydrolysed to the 3-hydroxy compounds. On the other hand from naringenin 7:4′-dimethyl ether and 5:7-dimethoxy flavanone, the 3-iodo compounds can be isolated as the first intermediates. The behaviour of the 3-hydroxy flavanones in acid and alkaline conditions also varies; either dehydrogenation to flavonol or dehydration to flavone taking place.
Our thanks are due to Dr. Pew of the Forest Products Laboratory, Madison, U.S.A., for the generous supply of 3-hydroxy naringenin used in this work.