Construction of 2-Substituted-3-aryl Benzofurans and Indoles through an Acid-Catalyzed Cascade Intramolecular Friedel-Crafts Reaction/Rearrangement/Aromatization Process.

We present here a new method for the synthesis of 2-substituted-3-aryl benzoheterocycles through a more challenging constrained [1,5]-type Friedel-Crafts reaction/rearrangement and aromatization process. By using the readily available 2-aryoxy-1,3-indandiones and 2-arylamino-1,3-indandiones, a range of 2-substituted-3-aryl benzofurans and indoles were prepared in good to excellent yields (yields up to 86%) under the catalysis of CFSOH or Sm(OTf). Compared with previous methods for constructing similar structures, this approach offers several advantages, including the use of easily accessible starting materials, mild reaction conditions, high yield, excellent regio- and diastereoselectivity, and a broad substrate scope.