Reaction of 4‑(Alkynyloxy)cyclohexa-2,5-dienones\nwith Dimethyl Sulfoxide: A Catalyst-Free Formation of 6/5/3-Fused\nTricyclic Enones

6/5/3-Fused\ntricyclic enones were obtained when 4-(alkynyloxy)cyclohexa-2,5-dienones\nwere treated with DMSO at 150 °C. The reaction proceeded via\na four-membered oxathietene intermediate. The protocol developed is\natom economical, has a broad substrate scope, and is amenable to gram-scale\nsynthesis. The products obtained are susceptible to further synthetic\ntransformations.