Facile and efficient synthesis of polyfunctionalized benzofurans: three-component coupling reactions from an alkynylsilane, an o-hydroxybenzaldehyde derivative, and a secondary amine by a Cu(I)-Cu(II) cooperative catalytic system

The combination of 5 mol % Cu(OTf)2 and CuCl in the presence of DMAP effectively catalyzed a three-component coupling reaction involving an alkynylsilane, an o-hydroxybenzaldehyde derivative, and a secondary amine. The reaction proceeded via intramolecular 5-exo-dig cyclization, resulting in direct synthesis of the corresponding benzofuran derivatives in moderate to excellent yields.