Gold-catalyzed cycloisomerization of o-alkynylbenzaldehydes with a pendant unsaturated bond:: [3+2] cycloaddition of gold-bound 1,3-dipolar species with dipolarophiles

A new and novel Au-catalyzed cycloisomerization of ynals bearing a pendant unsaturated bond leading to synthetically valuable [6.7.n]-tricyclic compounds were developed. This study strongly supports the intermediacy of [3 + 2] cycloaddition proposed by DFT calculation and provides an easy access to key skeletons found in a variety of natural products.