Accessing 2-Arylbenzofurans by CuI2(pip)2-Catalyzed Tandem Coupling/Cyclization Reaction: Mechanistic Studies and Application to the Synthesis of Stemofuran A and Moracin M

An asymmetric dinuclear copper(I) complex, Cu-2(I)(pip)(2) (pip=(2-picolyliminomethyl)pyrrole anion), was used to catalyze the tandem coupling/cyclization reaction of o-iodophenols and terminal alkynes, which led to the formation of valuable 2-arylbenzofurans in good yields. DFT calculations showed that the two proximate copper atoms play cooperative roles throughout the catalytic cycle. Using this catalytic protocol, bioactive natural products stemofuran A and moracin M were concisely synthesized.