Lewis Acid‐Catalyzed Tandem Annulation of Propargylic Alcohols with 2‐Allylphenols and Their Anti‐tumor Activities

A novel bismuth(III) trifluoro‐methanesulfonate‐catalyzed and environmentally benign synthetic strategy for the construction of a wide range of structurally diverse, sophisticated [5,6,5]‐oxygen‐containing tricyclic frameworks with easy‐to handle propargylic alcohols and 2‐allylphenols as substrates in the presence of Bi(OTf)₃ and AgOTf is described. This Lewis acid catalyzed [3+2] annulation protocol, which tolerates a great deal of functional groups, proceeds through a sequential Meyer‐Schuster rearrangement, nucleophilic substitution, 5‐exo‐trig cyclization, 5‐endo‐trig cyclization, and proton exchange sequences, affording a versatile approach for accessing oxygen‐containing tricyclic skeletons in moderate‐to‐excellent yields. In addition, most of the obtained compounds exhibited anti‐tumor activities against three types of human cancer cell lines in vitro, including Caco‐2 colon cancer cells, MCF‐7 breast cancer cells, and Hepg‐2 liver cancer cells.