p‑TsOH Promoted Au(I)-Catalyzed Consecutive Endo Cyclization of Yne-Tethered Ynamide: Access to Benzofused Dihydroisoquinolones

A novel synthetic route to benzo­[f]­dihydro­isoquinolone through a p-TsOH promoted cascade cyclization of easily accessible diyne-tethered ynamides in the presence of a Au­(I)-catalyst is described. This reaction unveils a broad substrate scope, constructing a wide range of benzo­[f]­dihydro­isoquinolones in good yields. The diyne-tethered ynamides are synthesized from inexpensive o-iodoaniline through Sonogashira couplings and the Cu-mediated C–N bond formation. The role of p-TsOH is examined, and the reaction pathway is also deduced. The benzo­[f]­isoquinoline scaffold is constructed from benzo­[f]­dihydro­isoquinolones.