Chemistry Letters Vol.33, No.5 (2004)
529
were obtained in reasonable yields.
ganic materials. Further investigation on the relation between
substituents on 1 and 4 and refractive indices is underway in
our laboratory.
We next challenged to synthesize hexatriynes 4 by use of
propargyl sulfone 5 with electron-withdrawing group and alde-
hyde 6 with electron-donating group as starting compounds
(Scheme 3). Hexatriynes 4 are expected to bring about high bi-
refringence because of long conjugation along the molecular
long axis as well. Fluorophenylpropargyl sulfone 5a was pre-
pared by H2O2-oxidation of the corresponding sulfide which
was derived from Sonogashira coupling between fluoroiodoben-
zene and phenyl propargyl sulfide. Aldehyde 6a was prepared
by MnO2-oxidation of 4-methoxyphenylpropargyl alcohol
which was produced from Sonogashira coupling between
iodomethoxybenzene and propargyl alcohol.
When (4-fluorophenyl)propargyl sulfone 5a was treated
consecutively with LDA, 4-methoxyphenylpropynal 6a, ClP(O)-
(OEt)2 and LiHMDS, the one-pot protocol for acetylene synthe-
sis proceeded smoothly to give the desired fluorophenyl(methox-
yphenyl)hexatriyne 4a in 68% yield. This process can be utilized
for access to other hexatriyne derivatives substituted by pentyl-
oxy and trifluoromethyl groups 4b and 4c.
We are grateful to Dr. Chizu Sekine of Sumitomo Chemical
Co. Ltd., for refractive index analyses. Financial support from
New Energy and Industrial Technology Development Organiza-
tion (NEDO) of Japan for Industrial Technology Research Grant
Program (01B68006d) and the Sumitomo Foundation to A.O. is
gratefully acknowledged.
References and Notes
1
H. H. B. Meng, L. R. Dalton, and S. T. Wu, Mol. Cryst. Liq.
Cryst., 259, 303 (1994); S. T. Wu, J. D. Margerum, M. S.
Ho, M. Fung, C. S. Hsu, S. M. Chen, and K. T. Tsai, Mol.
Cryst. Liq. Cryst., 261, 79 (1995); C. S. Hsu, K. T. Tsay,
A. C. Chang, S. R. Wang, and S. T. Wu, Liq. Cryst., 19,
4409 (1995).
2
H. Takatsu, K. Takeuchi, Y. Tanaka, and M. Sasaki, Mol.
Cryst. Liq. Cryst., 141, 279 (1986); S. T. Wu, U. Finkenzeller,
and V. Reiffenrath, J. Appl. Phys., 65, 4372 (1989); Y. Goto, T.
Inukai, A. Fujita, and D. Demus, Mol. Cryst. Liq. Cryst., 260,
23 (1995); A. J. Seed, K. J. Toyne, J. W. Goodby, and M. Hird,
J. Mater. Chem., 10, 2069 (2000).
SO Ph
2
F
5a (1.1 equiv.)
3
4
C. Sekine, K. Fujisawa, N. Konya, and M. Minai, Mol. Cryst.
Liq. Cryst., 332, 235 (1999); T. Tanaka, C. Sekine, T. Ashida,
and M. Ishitobi, N. Konya, M. Minai, and K. Fujisawa, Mol.
Cryst. Liq. Cryst., 346, 209 (2000).
K. Sonogashira, Y. Tohda, and N. Hagihara, Tetrahedron Lett.,
1975, 4467; Y. Tohda, K. Sonogashira, and N. Hagihara, Syn-
thesis, 1977, 777; S. Takahashi, Y. Kuroyama, K. Sonogashira,
and N. Hagihara, Synthesis, 1980, 627.
1) LDA
THF
2)
MeO
CHO
6a
3) ClP(O)(OEt)
2
4) LiHMDS
4a
1
2
4a (R =F, R =CH ) 68%
4b (R =F, R =C H ) 74%
4c (R =CF , R =CH ) 39%
3
1
2
1
2
OR
R
5
11
5
6
A. L. K. Shi Shun, E. T. Chernick, S. Eisler, and R. R.
Tykwinski, J. Org. Chem., 68, 1339 (2003).
1
2
3
3
F. Ye, A. Orita, A. Doumoto, and J. Otera, Tetrahedron, 59,
5635 (2003); A. Orita, F. Ye, A. Doumoto, and J. Otera, Chem.
Lett., 32, 104 (2003); A. Orita, D. Hasegawa, T. Nakano, and J.
Otera, Chem.—Eur. J., 8, 2000 (2002); A. Orita, D. L. An, T.
Nakano, J. Yaruva, N. Ma, and J. Otera, Chem.—Eur. J., 8,
2005 (2002); A. Orita, N. Yoshioka, P. Struwe, A. Braier, A.
Beckmann, and J. Otera, Chem.—Eur. J., 5, 1355 (1999).
To a THF solution (10 mL) of 4-pentyloxybenzyl phenyl sul-
fone (2a) (280 mg, 0.88 mmol) was added BuLi (0.60 mL,
1.6 M THF solution, 0.97 mmol) at ꢁ78 ꢂC, and the mixture
was stirred for 0.5 h. To this solution was added a THF solution
(2 mL) of 2,5-dimethylbenzene-1,4-dipropynal (3a) (84 mg,
0.4 mmol), and the mixture was stirred for 5 min. After
ClP(O)(OEt)2 (0.14 mL, 0.96 mmol) had been added, the reac-
tion mixture was stirred at RT for 2 h. After t-BuOK (896 mg,
8.0 mmol) had been added at 0 ꢂC, the mixture was stirred at
RT for 3 h. After usual workup with sat. NH4Cl aq/CH2Cl2,
the combined organic layer was washed with brine and dried
over anhydrous magnesium sulfate. The organic layer was
evaporated under vacuum, and the residue was subjected to
column chromatography to give 1a (135 mg, 64%). 1a: 1H
NMR (500 MHz, CD2Cl2): ꢁ 0.93 (t, J ¼ 7:0 Hz, 6H), 1.34–
1.46 (m, 8H), 1.75–1.81 (m, 4H), 2.40 (s, 6H), 3.96 (t, J ¼
6:6 Hz, 4H), 6.84 (d, J ¼ 8:5 Hz, 4H), 7.32 (s, 2H), 7.46 (d,
J ¼ 8:5 Hz, 4H); 13C NMR (125 MHz, CD2Cl2): ꢁ 14.0,
20.0, 22.4, 28.1, 28.8, 68.1, 72.7, 79.5, 79.7, 83.6, 113.3,
114.6, 122.5, 133.5, 134.1, 138.7, 160.0. Elemental analysis
calcd (%) for C38H38O2: C 86.65, H 7.27; found: C 86.62, H
7.29.
Scheme 3.
With new acetylenes, 1 and 4, in hand, we measured bire-
fringences of these compounds, and the refractive indices of sev-
eral of them were evaluated as extrapolated values from mix-
tures containing 10wt % of each test compounds in MJ931381
(Merck, Japan) by use of Abbe refractometer (2T, Atago)
(Table 1). As we expected, refractive indices of bis(diynyl)ben-
zenes 1a, b, and e were found considerably larger in comparison
with other simpler aromatic acetylenes such as 7. Hexatriyne 4b
showed a remarkably high birefringence value larger than 0.5,
and it has been disclosed that hexatriyne 4 is a promising com-
pound for high birefringent organic material.
7
In summary, we have succeeded in the convenient syntheses
of bis(diynyl)benzenes 1 and hexatriynes 4, and disclosed that
these compounds are promising for high birefringence (ꢀn) or-
Table 1. Refractive indices of 1 and 4
compound
Refractive Index
1a
1b
1e
4b
0.44 (185 °C, 633 nm)
0.31 (135 °C, 633 nm)
0.46 (210 °C, 633 nm)
0.52 (90 °C, 633 nm)
C H
C H
3
7
3
7
(7)
a
0.26 (20 °C, 589 nm)
8
C. Sekine, K. Fujisawa, N. Konya, and M. Minai, Liq. Cryst.,
28, 1361 (2001).
a
Ref 8.
Published on the web (Advance View) April 5, 2004; DOI 10.1246/cl.2004.528