Synthetic Studies on the Benzofuran Derivatives. Part III. Reaction of 7-Hydroxy-8-formyl-2-methylisoflavone with Ethyl Bromomalonate and Synthesis of Furano(2′,3′:7,8)-2-methylisoflavone

5′-Carbethoxy-furano(2′,3′: 7,8)-2-methylisofiavone (IV) was obtained from 7-hydroxy-8-formyl-2-methylisoflavone (III) and ethyl bromomalonate by Tanaka’s method for benzofuran synthesis. The condensation product IV was hydrolyzed to give the free acid V, which was decarboxylated in quinoline with copper powder to yield furano(2′,3′: 7,8)-2-methylisoflavon (VIII). The structures of the condensation product and its derivatives were discussed.