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

Abstract 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. magnified image