Dihalo-substituted dibenzopentalenes: their practical synthesis and transformation to dibenzopentalene derivatives.
Diiodo- and bromo, iodo-substituted dibenzopentalenes were obtained by treatment of 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene with I(2) and IBr, respectively. These dihalo-substituted pentalenes reacted with terminal ethynes in Sonogashira coupling and with arylboronic acid in Suzuki-Miyaura coupling to give a series of phenylethynyl- and/or aryl-substituted pentalenes. Suzuki-Miyaura coupling of the halopentalenes with in situ prepared pentaleneboronic esters provided bis-, tri-, and tetra(dibenzopentalene)s. It was found that these dibenzopentalene oligomers underwent facile electrochemical reduction and exhibited a bathochromic shift in UV-vis absorption spectra because of their expanded π-systems.
Department of Applied Chemistry, Okayama University of Science, Okayama 700-0005, Japan.
Feng
F
Xu
Lifen
L
Peng
Akihiro
A
Orita
Junzo
J
Otera