Copper-Catalyzed Regioselective Annulation of β-Keto Esters and Propargyl Acetates: Access to Polysubstituted Furans.

A copper-catalyzed regioselective annulation reaction, conducted without ligands or oxidants, has been developed for the preparation of multisubstituted furans from the readily available starting materials, β-keto esters and propargyl acetates. This process accommodates a wide range of functional groups, resulting in furan skeletons with diverse substitution patterns. The method's potential synthetic utility is highlighted by its applicability in gram-scale preparations and late-stage modifications of natural products.