Fe(III)-Catalyzed Ring Expansion of Cyclopropenone from Olefins via Radicals to Access Pyrone and Indanone Derivatives

A novel approach for the synthesis of pyrone and indanone derivatives utilizing Fe(III)-catalyzed reductive radical ring expansion of olefins and cyclopropenone has been proposed. The preliminary mechanism study shows that the alkyl radical is formed by hydrogen atom transfer, which can open the tension ring and then generate the intermediate. There are two paths for the intermediate: when there is a hydroxyl group at the β-position of the olefin, the reaction produces pyrones, and otherwise 1-indanone is generated. This method has mild conditions and wide substrate adaptability and allows the indanone fragment to be conveniently accessed.