Regioselective Access to Structurally Diverse Coumarin Analogues via Iron-catalyzed Annulation Reactions

A highly efficient iron-catalyzed propargylation-alkyne oxacyclization-isomerization strategy is disclosed to expeditiously assemble representative bioactive furo[3,2-c]coumarins and pyrano[3,2-c]coumarins with moderate to good yields and a broad substrate scope. The regioselective access to different coumarins is mainly dependent on the terminal group of the secondary propargylic alcohol.