Synthesis of Fused-β-Lactams through Selective Gold-Catalyzed Oxycyclization of Dioxolane-Tethered Enynes

The gold-catalyzed preparation of 2-azetidinone-fused oxacycles was accomplished from β-lactam-linked enynes through heterocyclization reaction taking advantage of the acetonide pendant group. While the synthesis of fused tetrahydrofuran-β-lactams from 1,3-enynes could be considered as an unusual metal-catalyzed cyclization of enynols, α-alkoxy dioxolane-tethered 1,3-enynes exclusively undergo bis-oxycyclization to afford tricyclic bridged acetals.