Gold and TfOH-Cocatalyzed Tandem Reaction of ortho-Akynylarylaldehydes with Cyclopropenes: an Efficient Route to Functionalized Benzo[7]annulene Derivatives

A novel gold(III) and TfOH-cocatalyzed reaction of ortho-alkynylbenzaldehydes with cyclopropenes was described for the synthesis of a variety of functionalized benzo[7]annulene derivatives in a highly stereoselective manner. This reaction could undergo tandem [4+2] cycloaddition/ring expansion to achieve the construction of seven-membered-carbocycles, along with the cleavage of double bond of cyclopropenes. The reaction features simple operations, commercially available catalysts and broad substrate scope with good efficiencies.