Facile and Diverse Synthesis of Benzo[ b ]fluorenone Derivatives through a Copper/Selectfluor‐Catalyzed Tandem Annulation of 1,6‐Enynes

A facile synthesis of a diverse array of benzo[ b ]fluorenone derivatives has been developed. The method involves a Cu 0 /Selectfluor‐catalyzed tandem annulation of 1,6‐enynes, which takes place under mild reaction conditions. For tert ‐butylethynyl‐substituted 1,6‐enynes, the major reaction pathway was a tandem annulation/C–C‐bond‐cleavage/fluorination process leading to fluorinated benzo[ b ]fluorenones as the major products; tert ‐butyl‐substituted benzo[ b ]fluorenones were obtained as the minor products. For arylethynyl‐substituted 1,6‐enynes, the substrates underwent tandem annulations to give 5‐aryl‐substituted benzo[ b ]fluorenones in moderate to excellent yields. For (trimethylsilyl)ethynyl‐substituted 1,6‐enynes, the reaction involved a tandem annulation/C–Si‐bond‐cleavage process to deliver 11 H ‐benzo[ b ]fluoren‐11‐ones in moderate yields.