Gold-catalyzed cyclization and cycloisomerization of yne-tethered ynamide: the significance of a masked enol-equivalent of an amide

This perspective briefly describes the conceptual manifestation of a Bronsted acid promoted Au-catalyzed cyclization of yne-tethered ynamides for the construction of novel N-heterocycles. A hetero-atom assisted intramolecular 6-endo-dig cyclization of a transient ketene N,O-acetal (a masked enol-ether of an amide), generated from an ambivalent ynamide through the attack of p-TsOH, with a Au-activated yne-motif creates dihydropyridinones and benzo[f]dihydroisoquinolones. The Au(I)-catalyzed cycloisomerization of an alkyne-tethered ketene N, N-acetal to manufacture unusual cyclobutene-fused azepine scaffolds is also highlighted.