Gold-Catalyzed Sequential Cyclization of 1-En-3,9-Diyne Esters to Partially Hydrogenated 3H-Dicyclopenta[a,b]naphthalenes.

A synthetic method that relies on a gold(I)-catalyzed cycloisomerization of 1-en-3,9-diyne esters to spiro[4.4]non-2-ene-substituted 1,2-dihydronaphthalenes is described. Robust with a wide variety of substitution patterns tolerated, the reaction provides the first example of a one-step strategy to construct such novel and architecturally challenging members of the carbocycle family in good to excellent yields. A mechanism is proposed in which the sequential cycloisomerization pathway was thought to involve a gold-catalyzed 1,3-acyloxy migration/Nazarov cyclization followed by a formal [4+2] cycloaddition to give the tetracarbocyclic product.