Regioselective Bismuth‐Catalyzed Synthesis of Pyranocoumarins and Furocoumarins from 4‐Hydroxycoumarins and Propargyl Alcohols

An efficient method for the bismuth‐catalyzed regioselective synthesis of pyranocoumarins and furocoumarins has been developed from the reaction of 4‐hydroxycoumarins with propargyl alcohols. The reaction proceeds through sequential propargylation and intramolecular cyclization reactions catalyzed by bismuth(III) triflate.