Gold(I)-Catalyzed Oxidative Cascade Cyclization of 1,4-Diyn-3-ones for the Construction of Tropone-Fused Furan Scaffolds

Gold(I)-catalyzed cascade cyclization of 1,4-diyn-3-ones with a pyridine N-oxide enabled direct construction of a benzo[6,7]cyclohepta[1,2-b]furan scaffold with the formation of four bonds. This reaction would proceed through oxidative cyclization, alkynyl migration, and 5-endo-dig type cyclization. Synthesis of benzotropone-fused naphtho[1,2-b]furans through a two-step sequence, including epoxidation and In(OTf)(3)-catalyzed intramolecular carbon carbon bond formation, is also presented.