Chalcones are easily accessible synthetic building blocks that are used in various heterocyclic syntheses. The rearrangement reaction using an oxidant is a characteristic conversion of chalcones, but applications to organic synthesis have been limited. Here, the development of a new method for synthesizing 3-acylindoles and azaisoflavones using a chalcone rearrangement strategy with hypervalent iodine reagents was described. Furthermore, the obtained new insight was applied to the selective synthesis of two benzofuran isomers from 2-hydroxychalcone derivatives and have demonstrated this method to the synthesis of the natural product, puerariafuran.
Keywords: chalcone; heterocycle; hypervalent iodine reagent; oxidative rearrangement; β-ketoacetal.