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 w as carried out in chloroform in presence of pyridine to afford moderat e to quantitative yields of the corresponding hindered 3-aryl-3-phenyl thiochroman-4-one derivatives. Removal of the phenylthio group by oxid ation 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 res pectively. In the 2-p-methoxypheriyl series the nickel boride reductio n of the compounds bearing ortho-substituted 3-aryl groups gave the ch alcones which were recyclised under basic catalysis.