Palladium-Catalyzed Oxyarylation, Azaarylation and α-Arylation Reactions in the Synthesis of Bioactive Isoflavonoid Analogues

Isoflavonoids constitute an important class of natural products, comprising great structural diversity. Known as phytoalexins and phytoestrogens, these compounds exhibit interesting biological activities. The corresponding carba-analogues, in which the oxygen atom at the B-ring is replaced by a methylene, are emerging as an attractive alternative for the preparation of new bioactive compounds. In this review, we report our results on the synthesis of isoflavonoid analogues (5-carba-pterocarpans, 1-carba-isoflavanones, 5-carba-11-aza-pterocarpan and pterocarpanquinones) with anti-cancer, anti-parasitic and anti-viral properties. Palladium-catalyzed oxyarylation and azaarylation of dihydronaphthalenes and alpha-arylation of alpha-tetralones were the key steps in the developed synthetic approaches. A historical background, as well as a brief mechanistic discussion of these reactions, will be presented.