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

Abstract

A facile synthesis of a diverse array of benzo[b]fluorenone derivatives has been developed. The method involves a Cu0/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 11H‐benzo[b]fluoren‐11‐ones in moderate yields.