スライド 1

Transannular Cyclization of
Dehydrobenzo[12]annulene Induced
by Nucleophilic Attack
Tobe Lab
Ayumi Yoshizaki
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Contents
• Introduction - π-Conjugated compounds
Application
Frame-work
Dibenzoindacene
• Motivation
• Experiments & Results
• Future Work
• Summary
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π-Conjugated compounds
2D π-conjugated compounds have attracted
attention as organic semiconductors.
E
・・・
N=1
N=2
Ethylene
N=3
Allyl Radical
N=4
N=5
N→∞
Butadiene Pentadienyl Radical
Energy bands of olefins
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Application
Pentacene
Pentacene has already been put to practical use in
thin-film transistor. But, it unfortunately is prone
toward oxidative degradation.
There is demand for alternative, acene-like topologies.
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Frame-work
• Acenes
condensed benzene ring in a line
• Dibenzopentalene
Pentalene
• Dibenzoindacene
Attractive Structural Motifs
Indacene
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Dibenzoindacene
• Antiaromatic (20 π-electorons)
p-Xylylene
• p-Xylylene core
• More resistant to degrade acenes
It does not possess any internal s-cis diene linkage.
s-cis diene
Fully conjugated dibenzoindacenes are
extremely rare.
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The Hückel Rule
• Aromatic
(4n+2) π-electrons (n = 0, 1, 2, 3, …)
• Antiaromatic
(4n) π-electrons (n = 0, 1, 2, 3, …)
E
x
Cyclic π-Conjugated
Polyene
Benzene
(4n+2) π
1,3-Cyclobutadiene
(4n) π
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Example１ of Dibenzoindacene
• Transannular Cyclization is induced by Iodine,
electrophilic.
• Tetraiodides
These rapidly oxidized to the corresponding diones
upon exposure to air.
R = H, Decane, Dodecane
Tetraiodides
T. M. Swager, et al. J. Org. Chem. 1994, 59, 1294-1301.8
Example 2 of Dibenzoindacene
• The Synthesis of Stable Dibenzoindacenes
Multiple Steps 2 or 3 months
1 : R=H
2 : R = Decane
M. M. Haley, et al. Angew. Chem. Int. Ed. ASAP
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Electronic Absorption Spectra
pentacene
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M. M. Haley, et al. Angew. Chem. Int. Ed. ASAP 10
Motivation
• The dibenzoindacene (tetraiodides) synthesized in a
single step is unstable.
• Multiple steps are required to synthesize the stable
one.
• For easy synthesis, a short-step synthesis rout is
required.
• I have studied to synthesize a dibenzoindacene with
transannular cyclization.
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Transannular Cyclization
J.Otera, et al. Chem. Lett. 2008, 37, 1296-1297.
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Synthesis of
Dehydrobenzo[12]annulene
Dehydrobenzo[12]annulene
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Identification by NMR
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3
4
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1
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Transannular Cyclization of
Dehydrobenzo[12]annulene
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Various reaction conditions were investigated.
（concentration of material, equivalent of BuLi,
reaction time, reaction temperature）
Reaction conditions were optimized.
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Identification by NMR
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Future Work 1
• I will study reaction conditions for the next
transannular cyclization.
• Then I will mesure its physical properties, and tune
them by using other reagents instead of BuLi and BuI.
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Future Work ２
• Bergman Cycloaromatization
W. M. Dai, et al. J. Am. Chem. Soc. 1992, 114, 7360-7371. 18
Future Work ２
• Bergman Cycloaromatization of 3
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Summary
• Dibenzoindacene are rare fully conjugated species.
• The reaction conditions for transannular cyclization
of dehydrobenzo[12]annulene were optimized.
• Future works are transannular cyclization of the next
step and bergman cycloaromatization to synthesize
π-conjugated compounds with short-steps.
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