Copper(I) Iodide Catalyzed Domino Knoevenagel Hetero-Diels-Alder Reaction of Terminal Acetylenes: Synthesis of Pyrano[2,3-c]pyrazoles

A new and efficient CuI-catalyzed domino Knoevenagel hetero-Diels-Alder reaction of 1-oxa-1,3-butadienes with terminal unactivated acetylenes as building blocks to afford pyrano[2,3-c]pyrazoles has been developed. The products were obtained in good to high yields in most cases. Synthesis of polycyclic compounds in one-pot, with easy workup, and mild reaction conditions are advantages of our reported method.