ARYLLEAD MEDIATED SYNTHESIS OF ISOFLAVANONE AND ISOFLAVONE DERIVATIVES

The reaction of aryllead (IV) triacetates with 3-(phenylthio)-chroman-4-one and 2-p-methoxyphenyl-3-(phenylthio)-chroman-4-one derivatives was carried out in chloroform in presence of pyridine to afford moderate to quantitative yields of the corresponding hindered 3-aryl-3-phenylthiochroman-4-one derivatives. Removal of the phenylthio group by oxidation with dimethyldioxirane led to the corresponding isoflavones and 2-p-methoxyphenylisoflavones, and by reduction with a large excess of nickel boride to the isoflavanones and 2-(4'-anisyl)-isoflavanones respectively. In the 2-p-methoxypheriyl series the nickel boride reduction of the compounds bearing ortho-substituted 3-aryl groups gave the chalcones which were recyclised under basic catalysis.