Palladium-Catalyzed Reaction of Haloarenes with Diarylethynes: Synthesis, Structural Analysis, and Properties of Methylene-Bridged Arenes

Fluorenes
and methylene-bridged polyarenes were easily and efficiently
synthesized from haloarenes (or aryl triflates) and diarylethynes
by a one-pot, two-step procedure. This protocol involves the palladium-catalyzed
cycloisomerization and a subsequent base-mediated retro-aldol condensation.
A major advantage is that the starting materials need not have ortho functional groups to complete the annulation. The
backbone of the designed products was enlarged using dihaloarenes,
highly π-conjugated haloarenes, or diarylalkynes. The mechanism
of the formation of benzo­[a]­fluorene was investigated.
The bowl-shaped structure of methylene-bridged indenocorannulene was
verified by X-ray crystallography. The photophysical and electrochemical
properties of the products thus prepared were investigated.