Efficient Assembly of Tetracyclic Framework of Fluorenols through Silver‐Catalyzed Tandem Reaction of Acceptor‐Enynals and Alkynes via Unfavorable 6‐endo‐dig Cyclization

Abstract We present a silver‐catalyzed reaction of acceptor‐enynals with alkynes to assemble tetracyclic framework of fluorenols efficiently, in which the reaction was proposed to proceed through an unfavorable 6 ‐endo‐dig cyclization, followed by a tandem [4+2] cycloaddition/Friedel–Crafts reaction. The reaction could be conducted in one pot for diaryl alkynes substrates. For terminal aryl alkyne or arylalkyl alkyne substrates, the Friedel–Crafts reaction has to be performed in the absence of alkynes. The control reactions demonstrated that there was competition between [Ag]⋅⋅⋅alkyne and [Ag]⋅⋅⋅O=CR 2 .