Gold-Catalyzed Spirocyclization of Furan-ynones and Unexpected Skeleton Rearrangement of the Resulting Spirohydrofurans

A gold-catalyzed cyclization of aniline-tethered furan-ynones has been developed. The reaction proceeds via trapping of the resulting stabilized cationic intermediate with an amide group leading to polycycles featured with a spiro-cyclohexadienone-hydrofuran framework with high efficiency. The resulting N-alkyl products undergo photorearrangements to afford the ring-enlarged benzo[b]azepine derivatives or iron-promoted novel rearrangement to diketone-containing spirocycles involving multiple C-X bond cleavages and formations.