Retro-Diels-Alder approach to the synthesis of π-expanded azuliporphyrins and their porphyrinoid aromaticity.
Bicyclo[2.2.2]octadiene (BCOD) fused azuliporphyrins were synthesized by 3+1 porphyrin synthesis of azulitripyrranes with diformylpyrroles. Subsequent retro-Diels-Alder reaction of the BCOD-fused azuliporphyrins afforded azulibenzo-, azulidibenzo-, and azulitribenzoporphyrins 1-5. NMR and UV/Vis spectra, as well as nucleus-independent chemical shift (NICS) calculations revealed that 1-5 and their diprotonated dications exhibit relatively low porphyrinoid aromaticity, which was dependent on the position and number of fused benzene rings present.
Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan. okujima.tetsuo.mu@ehime-u.ac.jp
Tetsuo
T
Okujima
Tasuku
T
Kikkawa
Haruyuki
H
Nakano
Hiroshi
H
Kubota
Nobumasa
N
Fukugami
Noboru
N
Ono
Hiroko
H
Yamada
Hidemitsu
H
Uno