2011. 12. 14.
Tobe Laboratory
Kitabayashi Kenichi
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Synthesis of Dizethrenylacetylene(Candidate for tetraradical)
Contents
1. Introduction - singlet diradical - zethrene - previous work in our laboratory2. Purpose of this work - tetraradical - zethrenedimers3. Experiment and discussion - synthetic route to dizethrenylacetylene - physical properties of dizethrenylbutadiyne 4. Future work and Summary
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t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
Mes
MesMes
Mes
y = 1y = 0
closed shell singlet diradical
0 < y < 1
open shell
diradical character
y
Singlet Diradical
H H H H H H
p-quinodimethane3
閉殻 開殻一重項ジラジカル
y = 0.81
y = 0.76Kubo, T. et al. Angew. Chem. Int. Ed. 2005, 44, 6564.
Kubo, T. et al. J. Am. Chem. Soc. 2010, 132, 11021.
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu = C CH3
CH3
CH3
Mes =
714
4
Moderate Singlet Diradical
Nakano, M. et al. Comp. Lett. 2007, 3, 333. zethrene(dibenzo[de,mn]tetracene)
7147 714
14
spin density
It is predicted theoretically that large spin density and frontier orbital coefficients of zethrene are located at the 7,14-positions.
LUMO −2.34 eVHOMO −4.56 eV (B3LYP/6-31G*)
Tobe, Y. et al. Pure Appl. Chem. 2010, 82, 871.
Zethrene is predicted to exhibit moderate singlet diradical character (y = 0.41) and high two-photon absorption property by computational studies.
Previous Syntheses of Zethrene
5
NC
CN
O
O
O
O(EtO2C)2HCOC
COCH(CO2Et)2
2 steps81%
2 steps1%>
Cu Cu
I I
pyridinerefluxCu
I
H(solvent)
(a)
(b)
Tetradehydrodinaphto[10]annulene
22% (a)50% (b)
Clar, E. et al. Chem. Ber. 1955, 88, 1520.
(a) Sondheimer, F. et al. Tetrahedron 1970, 26, 2141.(b) Staab, H. A. et al. Chem. Ber. 1971, 104, 1182.
Stepwise approach
Transannular cyclization
I2II
CHCl3
Ph
Ph
PhPd(PPh3)4, CuI
Et3N
1a ; R = H; 20%1b ; R = t-Bu; 22%
3a ; R = H; 65%3b ; R = t-Bu; 88%
I I
Me3Si SiMe3
Pd(PPh3)4, CuIDBU, NaOH aq.
benzene
R
RR
R R
R R
R R
R R
R R R
R R
R = H or t-Bu
2a ; R = H; 65%2b ; R = t-Bu; 68%
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Synthesis and Physical Properties of 3b
transannular cyclization
crosscoupling
Ph =
crosscoupling
zethrene
TPAcross−section
492 GM(650 nm)
509 GM (604 nm)
1138 GM (604 nm)
diphenyl-zethrene
rubrene
67 GM (612 nm)
0.4320.407 0.324diradical character ̶K
GM = 10−50 cm4 s photon−1 molecule−1
3b
TPA cross−section : 二光子吸収断面積
PhPh
Tobe, Y. et al. Org. Lett. 2009, 11, 4104.
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A Stable Tetraradical
Bertrand, G. et al. Angew. Chem. Int. Ed. 2004, 43, 4876.Bertrand, G. et al. Dalton Trans. 2008, 4482.
1.547Å
1.404Å1.411Å 1.383Å
quinoid structure
There is only a weak interaction between both diradical sites.
・ B2−C2 bond length is a little shorter than normal B−C bond length.
・ There is an alternation between slightly shorter and longer in the phenylene ring.
t-BuBP
PBt-Bu
i-Pr i-Pr
i-Pr i-Pr
BBP
PB
PB
PHt-But-Bu
i-Pr i-Pr
i-Pr i-Pr i-Pr i-Pr
i-Pr i-Pr
BBHP
PB
PB
Pt-But-Bu
i-Pr i-Pr
i-Pr i-Pr i-Pr i-Pr
i-Pr i-Pr
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Zethrene Dimers (Candidates for tetraradical)
・Zethrenylzethrene
tert-Butyl groups are omitted for clarity.
・ Dizethrenylacetylene (n = 1) Dizethrenylbutadiyne (n = 2)
Interaction between diradicals
・ The two zethrene backbones of 4a would be considerably twisted because of strong steric repulsion.・ Since the steric repulsion of the 4b would be small because of the acetylene spacer, two zethrene backbones would adopt a co-planar conformation. Therefore, interaction between two diradicals would become stronger as expressed by the cumulenic resonance structure.
H2C C C CH2
cumulene
Ph
Ph
Ph
Ph
4a
Ph
Ph
Ph
Ph
Ph
Ph
CC
n
n
n4b ; n = 14c ; n = 2
PhPhX
t-Bu
t-Bu t-Bu
t-Bu
6a ; X = Br6b ; X =Cl
TMS
PhPh
4b
Ph
6aor6b
t-Bu t-Bu
t-Bu t-But-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
desilylation
t-Bu
t-Bu
Ph
t-But-Bu
t-But-Bu
Ph
4a
t-Bu
t-Bu
XI
t-Bu
t-Bu t-Bu
t-Bu
7a ; X = Br7b ; X = Cl
5a
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Retrosynthetic Analyses of Zethrene Dimers
TMS = Si CH3
CH3
CH3
homo coupling
crosscoupling
precursors of4a and 4b
My first project is to synthesize asymmetric 7,14-dihalozethrenes 7a and 7b.
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Synthetic Studies for Asymmetric Disubstituted Zethrenes
Transannular cyclization of 1b with IBr and ICl did not give asymmetric 7,14-dihalozethrenes.
XI
t-Bu
t-Bu t-Bu
t-Bu
7a ; X = Br, 7b ; X = Cl
t-Bu
t-Bu t-Bu
t-Bu
IXXX
t-Bu
t-Bu t-Bu
t-Bu
2c ; X = Br; 60%2d ; X = Cl; 36%
IX
CHCl3 CHCl3
1b
PhPd(PPh3)4,
CuI
Et3N
PhXXX
t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu
2b ; X = I; 68%2c ; X = Br; 60%
6c ; X = I6a ; X = Br
2bPh
t-Bu
t-Bu t-Bu
t-Bu
3b
Ph 2c1b
I2 or IBr
CHCl3
startingmaterial
phenyl-acetylene
halophenylethynyl-zethrene 3b starting material
2b2c
0.7 eq
1.0 eq
6c ; 8%
6a ; 17%
16%
6%
2b ; 60% recovery
2c ; 45% recovery
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Synthetic Route to Dizethrenylacetylene
Quast, H. et al.J. Org. Chem. 2008, 73, 4956.(*)
PhPd(PPh3)4,
CuI
Et3N
PhX
Pd(PPh3)4,CuI
Et3N
TMS
Ph
TMS
K2CO3 Ph
THF,MeOH
Ph
Ph
Pd(0),Cu(I)
CHCl3XX
t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu
t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-But-Bu
t-Bu t-Bu
t-Bu
t-Bu
t-Bu t-Bu
t-Bu
I2 or IBr
(CH3)3CClAlCl3
t-Bu
NO2NO2 NH2NH2H2, Pd-C
fuming HNO3
I I1) H2SO42) NaNO23) KI
H2O, EtOH
TMS TMSTMSPdCl2(PPh3)2,
CuIPd(PPh3)4, CuIDBU, NaOH aq
benzene,pyridine
977%
829%
Ac2Ot-Bu t-Bu t-Bu t-Bu t-Bu t-Bu t-Bu
t-Bu t-Bu
Et3N
1b22%
2b ; X = I; 68%2c ; X = Br; 60%
6c ; X = I; 8%6a ; X = Br; 17%
(X = Br)
5b24%
5a95%
(*)EtOH,THF
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4b
6c or 6a
PhPhX
Pd(PPh3)4,CuI
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
t-Bu t-Bu
Ph
Pht-Bu
t-Bu t-Bu
t-Bu
t-Bu t-Bu
t-But-Bu
R
4c5a ; R = H5b ; R = TMS
6a ; X = Br6c ; X = I
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Sonogashira Coupling for Dizethrenylacetylene
dizethrenylbutadiyne
Attempted Sonogashira coupling of 6 and 5 did not give 4b but 4c which is a homocoupled product of 5a.
6 5 solvent additive temperature 4c6a 5a Et3N - 50 °C
10 ~ 15 %6a 5b benzene
DBUH2O 60 °C
6a 5bbenzenepyridine
DBUNaOH aq
95 °Creflux
6c 5bbenzenepyridine
DBUNaOH aq 70 °C
-2.3 -1.8 -1.3 -0.8 -0.3 0.2 0.7 1.2voltage /V
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300 350 400 450 500 550 600 650 700 7500
0.2
0.4
0.6
0.8
1
1.2
1.4
wave length / nm
Nor
mal
ized
inte
nsity
/ a.
u.UV Spectra and CV of Dizethrenylbutadiyne
UV spectra of 4c (red) and 3b (blue) in CH2Cl2 at 25 ˚C
Cyclic voltammogram of 4c and 3b in CH2Cl2 (1.0 mM, V vs. Ag/Ag+ in CH2Cl2 containing nBu4NClO4
as a supporting electrolyte, scan rate: 100 mV/s, Fc/Fc+ = 0 V)
Ph
Ph
t-Bu
t-Bu t-Bu
t-Bu
3b
lmax / nm Ered2 / V Ered1 / V Eox1 / V Eox2 / V Eox3 / V
+0.36 +0.71+0.21-1.54-1.68561
578 -1.81 +0.16 +0.65
・ Absorption maximum of 4c was blue shifted compared to that of 3b.・ Small shoulders were observed in the long-wave length region for 4c.
・ Splits of two oxidation waves and reduction waves indicate electron interaction between two zethrene backbones in 4c.
Ph
Pht-Bu
t-Bu t-Bu
t-Bu
t-Bu t-Bu
t-But-Bu
4c
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Future Work・ Synthesis of dizethrenylacetylene by Negishi coupling will be carried out.
・ Physical properties of dizethrenylbutadiyne and dizethrenylacetylene will be investigated.
・ Zethrenylzethrene will be synthesized.
Ph
t-Bu
t-Bu t-Bu
t-Bu
n-BuLi
THFZnCl2
Ph
t-Bu
t-Bu t-Bu
t-Bu
ZnCl
PhX
t-Bu
t-Bu t-Bu
t-Bu
6c ; X = I6a ; X = Br
Pd(PPh3)4
THF, toluene
Ph
Ph
t-Bu
t-Bu t-Bu
t-Bu
t-Bu
t-Bu t-Bu
t-Bu
4b
5a
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Summary
・ Recently, tetra-tert-butyl-7,14-bis(phenylethynyl)zethrene derivatives which exhibited high stability, high solubility, and high two-photon absorption property were synthesized.
・ Transannular cyclization of the [10]annulene with ICl and IBr did not give asymmetric 7,14-dihalozethrenes.
・ Attempted Sonogashira coupling of 7-ethynyl-14-(phenylethynyl)zethrene and 7-halo-14-(phenylethynyl)zethrene did not give dizethrenylacetylene but dizethrenylbutadiyne which is a homocoupled product of 7-ethynyl-14-(phenylethynyl)zethrene.
・ UV spectrum and Cyclic voltammogram of dizethrenylbutadiyne indicated electron interaction between two zethrene backbones in dizethrenylbutadiyne.
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