A New Approach to the Synthesis of Isoflavones, 2′-Hydroxyisoflavones and an Alternative Synthesis of (±)-Pterocarpin

A new approach to the synthesis of isoflavones and 2′-hydroxyisoflavones, useful intermediates for synthesis of pterocarpinoids, are described. The 2′-hydroxyisoflavone (VIII; R=CH3, R′=H) synthesized by this method, was converted into (±)-pterocarpin (VII; R=CH3, R′=H). Attempts to obtain the corresponding isoflavane or isoflavene from the coumarine (XVII) failed.