Sequential Gold-Catalyzed Carbene Transfer/Ring Closure: Oxidative Cyclization of β-(2-Alkynylphenyl)-α,β-ynones to Indenofuranones

β-(2-Alkynylphenyl)-α,β-ynones undergo a gold-catalyzed oxidative two-fold cyclization in the presence of N-oxides to give 1,3-disubstituted-8H-indeno[1,2-c]furan-8-ones in good yields. This cascade process is triggered by a selective oxygen transfer from an N-oxide onto the gold-activated alkynone to generate a α-dioxocarbene intermediate which, via carbene transfer across the remaining alkyne moiety and subsequent cyclization through nucleophilic attack by a carbonyl oxygen, achieves the construction of 1,3-disubstituted fused polycyclic furans. (Figure presented.).