Synthesis and Self-Association, Absorption, and Fluorescence Properties of Differentially Functionalized Hexakis(p-substituted-phenylethynyl)benzenes

Article abstract of DOI:10.1021/jo049948s

The dual Sonogashira coupling reactions of 1,3,5-tribromo-2,4,6-triiodobenzene with p-X-phenyl-acetylene followed by another p-Y-phenylacetylene (X, Y = OSiMe₂Bu-t or CO₂Et) produced a series of differentially functionalized hexakis(

Full text of DOI:10.1021/jo049948s

Syn th esis a n d Self-Associa tion , Absor p tion , a n d F lu or escen ce
P r op er ties of Differ en tia lly F u n ction a lized
Hexa k is(p-su bstitu ted -p h en yleth yn yl)ben zen es
Kenji Kobayashi* and Norifumi Kobayashi
Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422-8529, J apan
skkobay@ipc.shizuoka.ac.jp
Received J anuary 8, 2004
The dual Sonogashira coupling reactions of 1,3,5-tribromo-2,4,6-triiodobenzene with p-X-phenyl-
acetylene followed by another p-Y-phenylacetylene (X, Y ) OSiMe2Bu-t or CO2Et) produced a series
of differentially functionalized hexakis(p-substituted-phenylethynyl)benzenes with D3h symmetry
(3h : 1,3,5-X-2,4,6-Y) and C2v symmetry (3g,i: 1,2,3,5-X-4,6-Y; 3f,j: 1-X-2,3,4,5,6-Y). In a similar
manner, 1,3,5-tris(p-X-phenylethynyl)-2,4,6-tris(p-Y-phenylethynyl)benzenes and 1,2,3,5-tetrakis-
(p-X-phenylethynyl)-4,6-bis(p-Y-phenylethynyl)benzenes (3l: X ) OSiMe2Bu-t, Y ) NO2; 3m ,n :
X ) N(n-octyl)2, Y ) NO2; 3o,p : X ) N(n-octyl)2, Y ) CH(OCH2CH2O); 3q,r : X ) N(n-octyl)2, Y )
CHO; 3s,t: X ) N(n-octyl)2, Y ) CHdC(CN)2) were prepared. Compounds 3 with electron-
withdrawing groups self-aggregated by a π-π stacking interaction and solvophobic effect. In the
absorption and fluorescence spectra of 3, λmax(abs) and λmax(em) showed red shifts as the donor-
acceptor dipole at the end functional groups of the para position was increased. In the absorption
spectra, λmax(abs) showed red shifts upon increasing the number of combination of electron-donating
and -withdrawing groups on the diagonal line in a molecule, whereas λmax(em) in the fluorescence
spectra exhibited red shifts upon decreasing the molecular symmetry.
In tr od u ction
of hexa(phenylethynyl)benzene.11 The Sonogashira cou-
pling reaction is a powerful method for the synthesis of
D6h symmetry hexaethynylbenzenes from hexabromoben-
zene and terminal acetylenes.1,12,13 Differentially substi-
tuted D3h symmetry hexaethynylbenzenes have been
synthesized effectively by the Sonogashira coupling reac-
Hexaethynylbenzene derivatives with D6h or D3h sym-
metry have attracted considerable attention in the field
of materials science because of their divergent and
extended π-conjugated system. They have potential as a
building block for hypothetical 2-D carbon allotropes such
as graphyne and graphdiyne,1-4 and serve as core struc-
tures for dendritic materials5 and for discotic liquid
crystals.6 Differentially functionalized D3h symmetry
hexakis(p-substituted-phenylethynyl)benzenes with elec-
tron-donating and -withdrawing groups at the 1,3,5- and
2,4,6-positions, respectively, would also have potential as
second-order nonlinear optical materials.7-10 Kondo and
co-workers reported the third-order optical nonlinearity
(7) For octupolar nonlinear optical materials, see: (a) Ledoux, I.;
Zyss, J .; Siegel, J . S.; Brienne, J .; Lehn, J .-M. Chem. Phys. Lett. 1990,
172, 440-444. (b) Zyss, J .; Ledoux, I. Chem. Rev. 1994, 94, 77-105.
(c) Voigt-Martin, I. G.; Li, G.; Yakimanski, A.; Schulz, G.; Wolff, J . J .
J . Am. Chem. Soc. 1996, 118, 12830-12831. (d) McDonagh, A. M.;
Humphrey, M. G.; Samoc, M.; Luther-Davies, B.; Houbrechts, S.; Wada,
T.; Sasabe, H.; Persoons, A. J . Am. Chem. Soc. 1999, 121, 1405-1406.
(e) Wolff, J . J .; Siegler, F.; Matschiner, R.; Wortmann, R. Angew. Chem.,
Int. Ed. 2000, 39, 1436-1439. (f) Brunel, J .; Ledoux, I.; Zyss, J .;
Blanchard-Desce, M. Chem. Commun. 2001, 923-924. (g) Cho, B. R.;
Park, S. B.; Lee, S. J .; Son, K. H.; Lee. S. H.; Lee, M.-J .; Yoo, J .; Lee,
Y. K.; Lee, G. J .; Kang, T. I.; Cho, M.; J eon, S.-J . J . Am. Chem. Soc.
2001, 123, 6421-6422. (h) Nakano, M.; Fujita, H.; Takahata, M.;
Yamaguchi, K. J . Am. Chem. Soc. 2002, 124, 9648-9655.
(1) (a) Diercks, R.; Armstrong, J . C.; Boese, R.; Vollhardt, K. P. C.
Angew. Chem., Int. Ed. Engl. 1986, 25, 268-269. (b) Boese, R.; Green,
J . R.; Mittendorf, J .; Mohler, D. L.; Vollhardt, K. P. C. Angew. Chem.,
Int. Ed. Engl. 1992, 31, 1643-1645.
(8) For octupolar nonlinear optical materials with a supramolecular
system, see: (a) Thalladi, V. R.; Brasselet, S.; Bla¨ser, D.; Boese, R.;
Zyss, J .; Nangia, A.; Desiraju, G. R. Chem. Commun. 1997, 1841-
1842. (b) Thalladi, V. R.; Brasselet, S.; Weiss, H.-C.; Bla¨ser, D.; Katz,
A. K.; Carrell, H. L.; Boese, R.; Zyss, J .; Nangia, A.; Desiraju, G. R. J .
Am. Chem. Soc. 1998, 120, 2563-2577. (c) Wolff, J . J .; Gredel, F.;
Oeser, T.; Irngartinger, H.; Pritzkow, H. Chem. Eur. J . 1999, 5, 29-
38. (d) Se´ne´chal, K.; Maury, O.; Bozec, H. L.; Ledoux, I.; Zyss, J . J .
Am. Chem. Soc. 2002, 124, 4560-4561.
(2) (a) Diederich, F. Nature 1994, 369, 199-207. (b) Haley, M. M.
Synlett 1998, 557-565.
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38, 3499-3502.
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Wakabayashi, T.; Shida, T.; Achiba, Y. Tethahedron 2001, 57, 3629-
3636.
(9) For donor-acceptor diphenylacetylenes with second-order non-
linear optical properties, see: Dehu, C.; Meyers, F.; Bre´das, J . L. J .
Am. Chem. Soc. 1993, 115, 6198-6206.
(5) (a) Kayser, B.; Altman, J .; Beck, W. Chem. Eur. J . 1999, 5, 754-
758. (b) Mongin, O.; Hoyler, N.; Gossauer, A. Eur. J . Org. Chem. 2000,
1193-1197.
(6) (a) Praefcke, K.; Kohne, B.; Singer, D. Angew. Chem., Int. Ed.
Engl. 1990, 29, 177-179. (b) Kumar, S.; Varshney, S. K. Angew. Chem.,
Int. Ed. 2000, 39, 3140-3142. (c) Kouwer, P. H. J .; Mijs, W. J .; J ager,
W. F.; Picken, S. J . J . Am. Chem. Soc. 2001, 123, 4645-4646. (d) Ito,
S.; Inabe, H.; Morita, N.; Ohta, K.; Kitamura, T.; Imafuku, K. J . Am.
Chem. Soc. 2003, 125, 1669-1680.
(10) For nonlinear optical chromophores with donor and acceptor
groups based on through-space delocalization, see: (a) Bartholomew,
G. P.; Bazan, G. C. J . Am. Chem. Soc. 2002, 124, 5183-5196. (b)
Bartholomew, G. P.; Ledoux, I.; Mukamel, S.; Bazan, G. C.; Zyss, J . J .
Am. Chem. Soc. 2002, 124, 13480-13485.
(11) Kondo, K.; Yasuda, S.; Sakaguchi, T.; Miya, M. J . Chem. Soc.,
Chem. Commun. 1995, 55-56.
10.1021/jo049948s CCC: $27.50 © 2004 American Chemical Society
Published on Web 03/06/2004
J . Org. Chem. 2004, 69, 2487-2497
2487

Kobayashi and Kobayashi
CHART 1
SCHEME 1a
a
Reagents and conditions: (a) PdCl2(PPh3)2 (10 mol %), CuI
(20 mol %), PPh3 (20 mol %), Et3N, reflux, 50-112 h; (b) KOH (12
equiv), MeOH-THF-H2O, rt, 28 h; (c) KOH (60 equiv), THF-
H2O, 70 °C, 46 h.
Resu lts a n d Discu ssion
Syn th esis of F u n ction a lized Hexa k is(p-su bstitu t-
ed -p h en yleth yn yl)ben zen es w ith D6h Sym m etr y.
The Sonogashira coupling reaction of hexabromobenzene
1a with 8 equiv of p-methoxyphenylacetylene 2a , p-(tert-
butyldimethylsilyloxy)phenylacetylene 2b, or p-(ethoxy-
carbonyl)phenylacetylene 2c in the presence of PdCl2-
(PPh3)2 (10 mol %), CuI (20 mol %), and PPh3 (20 mol %)
in Et3N at refluxing temperature gave hexakis(p-meth-
oxyphenylethynyl)benzene 3a , hexakis[p-(tert-butyldi-
methylsilyloxy)phenylethynyl]benzene 3b, or hexakis[p-
(ethoxycarbonyl)phenylethynyl]benzene 3d in 68%, 68%,
or 73% yield, respectively (Scheme 1). The deprotection
of 3b or 3d by KOH quantitatively produced hexakis(4-
hydroxyphenylethynyl)benzene 3c or hexakis(4-carboxy-
phenylethynyl)benzene 3e, respectively.
Syn th esis of Differ en tia lly F u n ction a lized Hexa -
k is(p-su bstitu ted -p h en yleth yn yl)ben zen es w ith D3h
a n d C2v Sym m etr ies. To synthesize differentially func-
tionalized hexakis(p-substituted-phenylethynyl)benzenes
with D3h (1,3,5-X-2,4,6-Y) and C2v (1-X-2,3,4,5,6-Y or
1,2,3,5-X-4,6-Y) symmetries, we chose the dual Sono-
gashira coupling reactions of 1,3,5-tribromo-2,4,6-triiodo-
benzene 1b with p-X-phenylacetylene followed by another
p-Y-phenylacetylene because the Sonogashira coupling
reaction is tolerant of functional groups such as ester and
cyano groups.12 The compound 1b16 was synthesized by
the reaction of 1,3,5-tribromobenzene with H5IO6 and KI
in H2SO4.17
The Sonogashira coupling reaction of 1b with 2b-d
(2b: X ) OSiMe2Bu-t, 2c: X ) CO2Et, 2d : X ) N(n-
octyl)2) was carried out in the presence of PdCl2(PPh3)2
(3 mol %), CuI (6 mol %), and PPh3 (6 mol %) in Et3N.
The results and the structures of products are sum-
marized in Table 1 and Chart 2, respectively. The
reaction of 1b with 4 equiv of 2c at refluxing temperature
gave 1,3,5-tribromo-2,4-bis[p-(ethoxycarbonyl)phenyl-
ethynyl]-6-iodobenzene 4, 1,3,5-tribromo-2,4,6-tris[p-
(ethoxycarbonyl)phenylethynyl]benzene 5, and 1,3-dibro-
mo-2,4,5,6-tetrakis[p-(ethoxycarbonyl)phenylethynyl]-
benzene 6 in 10%, 21%, and 20% yields, respectively
(entry 1). The reaction of 1b with 2.8 equiv of 2b at
tion of 1,3,5-tribromo-2,4,6-triformylbenzene with termi-
nal acetylenes followed by the Corey-Fuchs dibromo-
olefination and then treatment with LDA (Rubin’s
method),3 or by the Sonogashira coupling reaction of
1,3,5-trichloro-2,4,6-triiodobenzene followed by the Negishi
coupling reaction (Sonoda-Tobe’s method).14 However,
the properties of differentially functionalized hexakis(p-
substituted-phenylethynyl)benzenes have not been sys-
tematically studied so far. As a part of our project on the
construction of hydrogen-bonded or metal-coordinated
porous networks in the solid state of host molecules with
extended π-conjugated system,15 we have chosen the dual
Sonogashira coupling reactions using 1,3,5-tribromo-
2,4,6-triiodobenzene because the Sonogashira coupling
reaction is tolerant of functional groups such as ester and
cyano groups.12 Here, we report the synthesis of a series
of differentially functionalized hexakis(p-substituted-
phenylethynyl)benzenes 3 with D6h, D3h (1,3,5-X-2,4,6-
Y), and C2v (1-X-2,3,4,5,6-Y or 1,2,3,5-X-4,6-Y) symmetries
(Chart 1), and their self-association, absorption, and
fluorescence properties.
(12) (a) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara,
N. Synthesis 1980, 627-629. (b) Sonogashira, K. In Metal-catalyzed
Cross-coupling Reactions; Diederich, F., Stang, P. J ., Eds.; Wiley-
VCH: Weinheim, Germany, 1998; Chapter 5.
(13) Tao, W.; Nesbitt, S.; Heck, R. F. J . Org. Chem. 1990, 55, 63-
69.
(14) Sonoda, M.; Inaba, A.; Itahashi, K.; Tobe, Y. Org. Lett. 2001, 3,
2419-2421.
(15) For 2-D or 3-D hydrogen-bonded porous networks of hexakis-
(p-substituted-phenyl)benzenes with D6h symmetry, see: (a) Kobayashi,
K.; Shirasaka, T.; Sato, A.; Horn, E.; Furukawa, N. Angew. Chem.,
Int. Ed. 1999, 38, 3483-3486. (b) Kobayashi, K.; Shirasaka, T.; Horn,
E.; Furukawa, N. Tetrahedron Lett. 2000, 41, 89-93. (c) Kobayashi,
K.; Sato, A.; Sakamoto, S.; Yamaguchi, K. J . Am. Chem. Soc. 2003,
125, 3035-3045.
(16) Barluenga, J .; Gonza´lez, J . M.; Garc´ıa-Mart´ın, M. A.; Campos,
P. J . Tetrahedron Lett. 1993, 34, 3893-3896.
(17) Mattern, D. L. J . Org. Chem. 1983, 48, 4772-4773.
2488 J . Org. Chem., Vol. 69, No. 7, 2004

Hexakis(p-substituted-phenylethynyl)benzenes
TABLE 1. Th e Son oga sh ir a Cou p lin g Rea ction of 1b
[p-(tert-butyldimethylsilyloxy)phenylethynyl]benzene 9,
and 1,3-dibromo-2,4,5,6-tetrakis[p-(tert-butyldimethylsi-
lyloxy)phenylethynyl]benzene 10 in 14%, 37%, 12%, and
3% yields, respectively (entry 3), whereas 9, 10, and
1-bromo-2,3,4,5,6-pentakis[p-(tert-butyldimethylsilyloxy)-
phenylethynyl]benzene 11 were obtained in 17%, 36%,
and 5% yields, respectively, when 3.7 equiv of 2b was
used under the same conditions (entry 4). The reaction
1b with 3.7 equiv of 2b at 55 °C followed by the additional
reaction using 0.75 equiv of 2b gave 8, 9, and 10 in 20%,
47%, and 13% yields, respectively (entry 5). The reaction
of 1b with 3.7 equiv of p-(N,N-di-n-octylamino)phenyl-
acetylene 2d at refluxing temperature produced 1,3,5-
tribromo-2,4,6-tris[p-(N,N-di-n-octylamino)phenylethynyl]-
benzene 12 and 1,3-dibromo-2,4,5,6-tetrakis[p-(N,N-di-
n-octylamino)phenylethynyl]benzene 13 in 57% and 9%
yields, respectively (entry 6). Thus, the product ratio for
the Sonogashira coupling reaction of 1b with the p-
substituted-phenylacetylenes 2b-d strongly depends on
the nature and the stoichiometry of 2b-d and the
reaction temperature.
w ith 2b-d
products,
yield (%)
entry
acetylene
conditions
4
5
6
1
2
2c
2c
4.0 equiv, reflux, 24 h
2.5 equiv, reflux, 14 h
and then 1.4 equiv,
55 °C, 24 h
10
32
21
17
20
32
products,
yield (%)
entry acetylene
conditions
7
8
9
10 11
3
4
5
2b
2b
2b
2.8 equiv, reflux, 40 h
3.7 equiv, reflux, 40 h
3.7 equiv, 55 °C, 150 h
and then 0.75 equiv,
55 °C, 90 h
14 37 12
3
0
5
0
0
0
0
17 36
20 47 13
Subsequently, the Sonogashira coupling reactions of
halides of mono-, bis-, tris-, tetrakis-, or pentakis(p-X-
phenylethynyl)benzenes 4-13 with p-Y-phenylacetylenes
2b-f were conducted. The Sonogashira coupling reaction
of 4, 5, or 6 with 7.5-4.3 equiv of 2b in the presence of
PdCl2(PPh3)2 (8-6.5 mol %), CuI (16-13 mol %), and
PPh3 (16-13 mol %) in Et3N at refluxing temperature
gave 1,2,3,5-tetrakis[p-(tert-butyldimethylsilyloxy)phen-
ylethynyl]-4,6-bis[p-(ethoxycarbonyl)phenylethynyl]-
benzene 3g, 1,3,5-tris[p-(tert-butyldimethylsilyloxy)phen-
ylethynyl]-2,4,6-tris[p-(ethoxycarbonyl)phenylethynyl]-
benzene 3h , or 1,3-bis[p-(tert-butyldimethylsilyloxy)phen-
ylethynyl]-2,4,5,6-tetrakis[p-(ethoxycarbonyl)phenyleth-
ynyl]benzene 3i in 56%, 70%, or 63% yield, respectively
(Scheme 2). The reaction of 7 or 11 with 2c under similar
conditions produced 1-[p-(tert-butyldimethylsilyloxy)-
phenylethynyl]-2,3,4,5,6-pentakis[p-(ethoxycarbonyl)-
phenylethynyl]benzene 3j or 1,2,3,4,5-pentakis[p-(tert-
butyldimethylsilyloxy)phenylethynyl]-6-[p-(ethoxycarbon-
yl)phenylethynyl]benzene 3f in 86% or 61% yield, respec-
tively (Scheme 3). The reaction of 9 with p-nitrophenyl-
acetylene 2e under similar conditions produced 1,3,5-
tris[p-(tert-butyldimethylsilyloxy)phenylethynyl]-2,4,6-
tris(p-nitrophenylethynyl)benzene 3l in 54% yield (Scheme
4). The reaction of 12 or 13 with 2e under similar con-
ditions produced 1,3,5-tris[p-(N,N-di-n-octylamino)phen-
ylethynyl]-2,4,6-tris(p-nitrophenylethynyl)benzene 3m or
1,2,3,5-tetrakis[p-(N,N-di-n-octylamino)phenylethynyl]-
4,6-bis(p-nitrophenylethynyl)benzene 3n in 50% or 8%
yield, respectively. The hydrolysis of 3h by KOH in THF-
H2O quantitatively produced 1,3,5-tris(p-carboxyphenyl-
ethynyl)-2,4,6-tris(p-hydroxyphenylethynyl)benzene 3k .
The Sonogashira coupling reaction of 12 or 13 with
p-(1,3-dioxolan-2-yl)phenylacetylene 2f under similar
conditions gave 1,3,5-tris[p-(N,N-di-n-octylamino)phen-
ylethynyl]-2,4,6-tris[p-(1,3-dioxolan-2-yl)phenylethynyl]-
benzene 3o or 1,2,3,5-tetrakis[p-(N,N-di-n-octylamino)-
phenylethynyl]-4,6-bis[p-(1,3-dioxolan-2-yl)phenylethynyl]-
benzene 3p in 23% or 36% yield, respectively (Scheme
5). The hydrolysis of 3o or 3p by 1 M HCl in THF
produced 1,3,5-tris[p-(N,N-di-n-octylamino)phenylethyn-
yl]-2,4,6-tris(p-formylphenylethynyl)benzene 3q or 1,2,3,5-
tetrakis[p-(N,N-di-n-octylamino)phenylethynyl]-4,6-bis(p-
products,
yield (%)
entry
6
acetylene
conditions
3.7 equiv, reflux, 43 h
12
13
2d
57
9
CHART 2
refluxing temperature produced 1,3,5-tribromo-2-[p-(tert-
butyldimethylsilyloxy)phenylethynyl]-4,6-diiodoben-
zene 7, 1,3,5-tribromo-2,4-bis[p-(tert-butyldimethylsilyloxy)-
phenylethynyl]-6-iodobenzene 8, 1,3,5-tribromo-2,4,6-tris-
J . Org. Chem, Vol. 69, No. 7, 2004 2489

Kobayashi and Kobayashi
SCHEME 2a
SCHEME 4a
a
a
Reagents and conditions: (a) PdCl2(PPh3)2 (6.5-8 mol %), CuI
Reagents and conditions: (a) PdCl2(PPh3)2 (7-8 mol %), CuI
(14-16 mol %), PPh3 (14-16 mol %), Et3N, reflux, 40-74 h.
(13-16 mol %), PPh3 (13-16 mol %), Et3N, reflux, 43-65 h.
SCHEME 3a
SCHEME 5a
a
Reagents and conditions: (a) PdCl2(PPh3)2 (6.5-8 mol %), CuI
(13-16 mol %), PPh3 (13-16 mol %), Et3N, reflux, 48-91 h.
formylphenylethynyl)benzene 3r in 82% or 74% yield,
respectively, which were converted, by the reaction of 3
equiv of malononitrile in CHCl3 in the presence of Et3N
and benzoic acid (30 mol % each), into 1,3,5-tris[p-(2,2-
dicyanoethenyl)phenylethynyl]-2,4,6-tris[p-(N,N-di-n-oc-
tylamino)phenylethynyl]benzene 3s or 1,3-bis[p-(2,2-
dicyanoethenyl)phenylethynyl]-2,4,5,6-tetrakis[p-(N,N-di-
n-octylamino)phenylethynyl]benzene 3t in 67% or 62%
yield, respectively.
Self-Associa tion Beh a vior . It is known that m-
phenylacetylene macrocycles, as well as m-diethynylben-
zene macrocycles, with electron-withdrawing groups at
the peripheral positions self-aggregate by a π-π stacking
a
Reagents and conditions: (a) PdCl2(PPh3)2 (6-9 mol %), CuI
(12-18 mol %), PPh3 (12-18 mol %), Et3N, reflux, 31-87 h; (b) 1
M HCl (10-12 equiv), THF, rt, 16 h; (c) malononitrile (3 equiv),
Et3N (30 mol %), PhCO2H (30 mol %), CHCl3, rt, 24 h to 50 °C,
100 h.
interaction and solvophobic effect.18 It was found that this
behavior is also the case for hexa(arylethynyl)benzene
derivatives with electron-withdrawing groups. In the H
1
NMR spectra of 3d with the ethoxycarbonyl group in
2490 J . Org. Chem., Vol. 69, No. 7, 2004

Hexakis(p-substituted-phenylethynyl)benzenes
1
F IGURE 2. Concentration dependence of H NMR chemical
1
shifts for the aromatic ortho protons with respect to the
methoxy group of 3a and ethoxycarbonyl group of 3d in a 1:4
mixture of acetone-d6 and CDCl3 at 23 °C: (a) 3a alone, (b)
the 3a unit in a 1:1 mixture of 3a and 3d , (c) 3d alone, and
(d) the 3d unit in a 1:1 mixture of 3a and 3d .
F IGURE 1. Concentration dependence of H NMR chemical
shifts for the aromatic ortho protons with respect to the
ethoxycarbonyl, nitro, formyl, and 2,2-dicyanoethenyl groups
of 3d , 3m , 3q, and 3s, respectively: (a) 3d , (b) 3m , and (c) 3s
in CDCl3 at 23 °C; (d) 3m , (e) 3q, and (f) 3s in a 1:4 mixture
of acetone-d6 and CDCl3 at 23 °C.
A solvophobic effect was also observed in the associa-
tion of hexa(arylethynyl)benzene derivatives. In a 1:4
mixture of acetone-d6 and CDCl3 at 23 °C, the KE was
increased to 449.2 M-1 for 3d , 93.0 M-1 for 3m , and 126.3
M-1 for 3s, the values of which are approximately seven
times greater than those in CDCl3. Compound 3q with
alternate dioctylamino and formyl groups also self-
aggregated with KE ) 23.6 M-1. Thus, the KE increased
in the order 3q < 3m < 3s < 3d with increasing the
electron-withdrawing ability of functional groups at the
para position (Table 2). For 3a , no association was
detected. These results clearly indicate the electron-
withdrawing effect for the self-association of hexa(aryl-
TABLE 2. Ca lcu la ted In d efin ite-Associa tion Con sta n ts
(KE) a n d Sa tu r a tion Ch em ica l Sh ift Ch a n ges (∆δSa t) of 3a ,
3d , 3m , 3q, a n d 3s in CDCl3 or a 1:4 Mixtu r e of Aceton e-d 6
a n d CDCl3 a t 23 °Ca
compd
solvent
KE (M-1
∼0
∼0
55.0 ( 6.0
)
∆δsat (ppm)
NA
NA
-1.26 ( 0.02
3a
CDCl3
acetone-d6/CDCl3 ) 1/4
3d
CDCl3
acetone-d6/CDCl3 ) 1/4 449.2 ( 23.0 -1.54 ( 0.05
3m
CDCl3
14.4 ( 0.7
93.0 ( 3.6
23.6 ( 1.2
20.5 ( 3.3
-0.97 ( 0.02
-0.62 ( 0.01
-0.44 ( 0.01
-0.37 ( 0.03
acetone-d6/CDCl3 ) 1/4
acetone-d6/CDCl3 ) 1/4
CDCl3
3q
3s
acetone-d6/CDCl3 ) 1/4 126.3 ( 11.4 -0.37 ( 0.01
1
ethynyl)benzene derivatives.18 However, in the H NMR
a
Determined on the basis of the indefinite-association model
by nonlinear least-squares fitting of chemical shift data.18 All
correlation coefficients were r > 0.99.
spectra of a 1:1 mixture of 3a and 3d in a 1:4 mixture of
acetone-d6 and CDCl3, the signals of the aromatic protons
for the 3a unit were undoubtedly shifted upfield upon
increasing the concentration. In this mixture, the upfield
chemical shift changes of the aromatic protons for the
3d unit were unambiguously smaller than those for 3d
alone over the same concentration range (Figure 2). This
result suggests, in a 1:1 mixture of 3a and 3d , coexistence
of self-association of 3d and a hetero-association between
donor 3a and acceptor 3d .18a
CDCl3, the signals of the aromatic protons were shifted
upfield upon increasing the concentration (Figure 1),
indicating that 3d self-aggregates by a π-π stacking
interaction. When the chemical shift changes for the
aromatic protons of 3d as a function of the concentration
were analyzed by the π-stacked infinite (isodesmic)
association model,18 the indefinite-association constant
(KE) of n aggregates of 3d was estimated to be KE ) 55.0
M-1 in CDCl3 at 23 °C (Table 2). Compounds 3m and 3s,
which possess alternately the electron-donating dioctyl-
amino group and the electron-withdrawing nitro or 2,2-
dicyanoethenyl group, also self-aggregated by a π-π
Absor p tion a n d F lu or escen ce P r op er ties. The
selected absorption and fluorescence spectral data of the
differentially functionalized hexakis(p-substituted-phen-
ylethynyl)benzenes 3a -t are summarized in Table 3.19
In the absorption spectra, for all compounds λmax(abs),
the absorption maximum, and λcut-off, the wavelength at
which the transmittance is 95%, are in the range from
360 to 481 nm and from 410 to 601 nm in CHCl3,
respectively, depending on the nature of the end func-
tional groups.19 A notable solvatochromism was not
observed, although a slight red shift of λmax(abs) was
observed as the dielectric constant of solvents was
stacking interaction, with KE ) 14.4 and 20.5 M-1
,
1
respectively. On the other hand, the H NMR spectra of
3a with the methoxy group did not show any chemical
shift changes even at higher concentration, indicating no
association.
increased.20
λmax(abs) for all of 3a -t in CHCl3 were red-
(18) (a) Shetty, A. S.; Zhang, J .; Moore, J . S. J . Am. Chem. Soc. 1996,
118, 1019-1027. (b) Lahiri, S.; Thompson, J . L.; Moore, J . S. J . Am.
Chem. Soc. 2000, 122, 11315-11319. (c) Tobe, Y.; Utsumi, N.; Kawa-
bata, K.; Nagano, A.; Adachi, K.; Araki, S.; Sonoda, M.; Hirose, K.;
Naemura, K. J . Am. Chem. Soc. 2002, 124, 5350-5364.
(19) For all absorption and fluorescence spectra and their data for
the individual derivatives 3, see the Supporting Information (Figures
S1-S17 and Table S1).
J . Org. Chem, Vol. 69, No. 7, 2004 2491

Kobayashi and Kobayashi
TABLE 3. Selected Absor p tion a n d F lu or escen ce
Sp ectr a l Da ta for 3a
λ
max(abs)
(nm)
λcut-off
λ
max(em) Stokes
(nm)b shift (nm)
compd
solvent
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
log ꢀ (nm)
3a
3b
3d
3f
3g
3h
363.8
362.3
360.2
364.5
367.6
368.8
332.6
316.6
364.5
308.9
367.4
364.0
378.3
318.1
380.0
316.8
464.0
340.2
433.2
332.0
428.6
319.8
418.6
401.2
321.0
423.8
318.6
434.2
318.8
434.0
315.2
418.6
398.0
411.0
448.6
329.0
440.8
325.3
440.4
323.8
452.4
328.6
434.8
323.4
415.8
316.2
427.4
319.4
426.0
317.4
480.8
375.2
436.0
384.8
5.19 416.0
5.22 414.3
5.28 409.8
5.19 422.7
5.20 426.2
5.20 425.6
5.17
459.0
458.0
456.0
466.0
466.8
462.6
95.2
95.7
95.8
101.5
99.2
93.8
5.16
1,4-dioxane
5.19 420.3
4.65
5.17 425.2
5.16 421.4
5.09 458.6
4.80
5.11 443.2
4.75
4.97 558.2
4.95
5.01 566.6
4.85
5.08 485.0
4.89
5.12 455.8
5.12
460.0
95.5
3i
3j
3l
CHCl3
CHCl3
CHCl3
466.6
466.8
NA
99.2
102.8
NA
1,4-dioxane
CHCl3
469.6
NA
89.6
NA
3m
3n
3o
F IGURE 3. Absorption spectra of 3h , 3l, 3m , 3o, 3q, and 3s
(1 × 10-5 M) in CHCl3.
CHCl3
NA
NA
CHCl3
504.8
76.2
hexane
472.2
501.8
53.6
100.6
4.90
1,4-dioxane
CH2Cl2
5.08 477.0
4.88
5.15 496.6
4.98
5.11 514.6
5.03
5.07 508.4
5.12 479.2
5.05 497.4
5.02 527.8
5.00
5.03 510.1
4.99
5.05 512.4
4.99
5.03 533.2
5.00
5.01 547.0
4.91
5.07 512.0
4.90
5.02 529.6
4.90
5.04 529.6
4.92
4.92 595.6
5.08
5.04 601.0
5.05
492.6
530.8
569.6
68.8
96.6
CH3CN
135.6
3p
3q
CHCl3
hexane
1,4-dioxane
CHCl3
515.1
479.2
500.6
555.6
96.5
81.2
89.6
107.0
F IGURE 4. Diagram for λmax(abs) and λmax(em) of 3b, 3d , and
3f-j in CHCl3.
benzene
1,4-dioxane
CH2Cl2
527.2
541.2
575.2
563.8
508.4
533.6
540.4
NA
86.4
100.8
122.8
129.0
92.6
longer wavelength was noticeably red-shifted as the
donor-acceptor dipole at the end functional groups of the
para position was increased (Table 3 and Figure 3).
λmax(abs) of 3s, which has the combination of N,N-dioc-
3r
CHCl3
tylamino and 2,2-dicyanoethenyl groups, reached 481
nm.21,22 This result reflects the π-electron delocalization
over the p- and o-bis(p-substituted-phenylethynyl)ben-
zene units in 3. In a series of derivatives with tert-
butyldimethylsilyloxy and ethoxycarbonyl groups 3b, 3d ,
and 3f-j in CHCl3, λmax(abs) showed slight red shifts
upon increasing the number of combination of the
electron-donating and -withdrawing groups on the di-
agonal line in a molecule (λmax(abs): 3b ,d < 3f,j <
3g,i < 3h ), as shown in Figure 4.10a This phenomenon
was also observed, and more distinctively, for other
combinations of the end functional groups: 3m vs 3n
(∆λmax(abs) ) 31 nm), 3o vs 3p (∆λmax(abs) ) 10 nm), 3q
vs 3r (∆λmax(abs) ) 14 nm), and 3s vs 3t (∆λmax(abs) )
45 nm) in CHCl3. The difference in the ∆λmax(abs) was
increased upon increasing the donor-acceptor dipole at
the end functional groups of the para position. These
results also reflect the π-electron delocalization.
hexane
benzene
1,4-dioxane
CHCl3
106.2
114.4
NA
3s
3t
CHCl3
NA
NA
a
Absorption and fluorescence spectra were measured at [3] )
1.0 × 10-5 M and [3] ) 1.0 × 10-6 M, respectively, at room
temperature. For all data in various solvents, see the Supporting
b
Information. The excitation wavelength is almost the same as
max(abs) in each case because the excitation spectrum of each 3
almost matched the absorption spectrum.
λ
shifted by 10-131 nm relative to λmax(abs) ) 350 nm of
the parent hexa(phenylethynyl)benzene,11 which is prob-
ably due to the electron-donating and electron-withdraw-
ing effects.7f,g,10a In a series of the D3h symmetry deriva-
tives 3h , 3l, 3m , 3o, 3q, and 3s in CHCl3, λmax(abs) at a
(21) For nonlinear optical materials with the 2,2-dicyanoethenyl
group, see: Katz, H. E.; Singer, K. D.; Sohn, J . E.; Dirk, C. W.; King,
L. A.; Gordon, H. M. J . Am. Chem. Soc. 1987, 109, 6561-6563.
(22) For photoluminescent materials with the 2,2-dicyanoethenyl
group, see: Ogura, K.; Zhao, R.; Yanai, H.; Maeda, K.; Tozawa, R.;
Matsumoto, S.; Akazome, M. Bull. Chem. Soc. J pn. 2002, 75, 2359-
2370.
(20) The dielectric constants of solvents used here are as follows:
hexane 1.89; 1,4-dioxane 2.21; benzene 2.28; CHCl3 4.81; CH2Cl2 8.9;
CH3CN 37.5.
2492 J . Org. Chem., Vol. 69, No. 7, 2004

Hexakis(p-substituted-phenylethynyl)benzenes
F IGURE 5. Emission spectra of 3h , 3l, 3o, and 3q (1 × 10-6
M) in 1,4-dioxane. The excitation wavelength is almost the
same as λmax(abs) in each case.
F IGURE 6. Emission spectra of 3o (1 × 10-6 M) in (a) hexane,
(b) 1,4-dioxane, (c) CHCl3, (d) CH2Cl2, and (e) CH3CN. The
excitation wavelength is almost the same as λmax(abs) in each
case.
The differentially functionalized hexakis(p-substituted-
phenylethynyl)benzenes 3, except for 3l in CHCl3 and
3m , 3n , 3s, and 3t in all solvents, are highly fluorescent,
tions of 1b with two kinds of 2. Compounds 3 with
electron-withdrawing groups were found to self-aggregate
by a π-π stacking interaction and solvophobic effect,
wherein the KE increased with increasing the electron-
withdrawing ability of functional groups at the para
position. In the absorption spectra of 3, λmax(abs) showed
red shifts when the donor-acceptor dipole at the end
functional groups of the para position or the number of
combinations of these was increased. In the fluorescence
spectra of 3, λmax(em) exhibited red shifts upon increasing
the donor-acceptor dipole at the end functional groups
of the para position or upon decreasing the symmetry of
a molecule. The introduction of differentially functional
groups into hexa(phenylethynyl)benzene would endow it
with potential as a building block for molecular de-
vices.3,6,11 Studies are in progress to explore the nonlinear
optical properties in 3, as well as the application of 3c,
3e, and 3k directed toward a 2-D hydrogen-bonded or
metal-coordinated porous network with an asymmetric
substituent.
λ
max(em) being in the range from 456 to 564 nm (Table
3).19 The excitation spectra of 3 almost matched the
absorption spectra, except for 3h in which the excitation
spectrum matched only the region of λmax(abs) at a longer
wavelength. In the majority of cases, the emission showed
a relatively large Stokes shift in the range from 81 to
129 nm, except for 3o. The large Stokes shift value is
consistent with a nuclear reorganization taking place
after excitation, prior to emission, as a result of electronic
redistribution.7f In a series of the D3h symmetry deriva-
tives 3h , 3l, 3o, and 3q in CHCl3 or 1,4-dioxane, λmax
-
(em) was red-shifted as the donor-acceptor dipole at the
end functional groups of the para position was increased
(Table 3 and Figure 5). λmax(em) of 3q in CHCl3, which
has the combination of N,N-dioctylamino and formyl
groups, reached 556 nm. In a series of derivatives with
tert-butyldimethylsilyloxy and ethoxycarbonyl groups 3b,
3d , and 3f-j in CHCl3, λmax(em) exhibited modest red
shifts upon decreasing the symmetry of a molecule (λmax
-
Exp er im en ta l Section
(em): D6h (3b,d ) < D3h (3h ) < C2v (3f,g,i,j), as shown in
Figure 4. This behavior was also observed with other
combinations of the end functional groups: 3o vs 3p
(∆λmax(em) ) -10 nm) and 3q vs 3r (∆λmax(em) ) -8 nm)
in CHCl3. These results would arise from a greater
stabilization of the charge redistribution by the dipole
orientation.10a In contrast to 3b, 3d , and 3h , the deriva-
tives bearing N,N-dioctylamino group 3o-r showed a
modest solvatochromic shift as the dielectric constant of
the solvents was increased (Table 3), indicative of a polar
excited state.7f,10a,20 In the case of 3o, λmax(em) in CH3CN
was red-shifted by 98 nm relative to that in hexane
(Figure 6).
p-Substituted-phenylacetylenes 2a -f were prepared accord-
ing to the literature.12a
1,3,5-Tr ibr om o-2,4,6-tr iiod oben zen e (1b). The compound
1b16 was prepared by the modified procedure of the literature.17
To concentrated H2SO4 (410 mL) at room temperature was
added periodic acid (27.36 g, 120 mmol) in small portions over
15 min. After dissolution of the periodic acid, crushed KI (59.78
g, 360 mmol) was added in small portions at 0 °C over 1 h. To
the resulting deep purple solution at 0 °C was added 1,3,5-
tribromobenzene (12.59 g, 40.0 mmol) in small portions over
25 min. After the solution was stirred at room temperature
for 62 h, the resulting thick mixture was poured onto ice. The
resulting precipitate was filtered and washed with H2O and
then MeOH. The solid was triturated with MeOH, filtered, and
recrystallized from pyridine-EtOH to give 1b (18.46 g, 66%
yield) in four crops as pale yellow needle crystals. Mp 268 °C;
13C NMR (DMSO-d6) δ 138.6, 108.2.
Con clu sion
We have demonstrated the synthesis of a series of
differentially functionalized hexakis(p-substituted-phen-
ylethynyl)benzenes 3 with D6h symmetry by the Sono-
gashira coupling reaction of 1a with 2, or with D3h and
C2v symmetries by the dual Sonogashira coupling reac-
Typ ica l P r oced u r e for th e Son oga sh ir a Cou p lin g
Rea ction of 1a w ith 2: Hexa k is[p-(ter t-bu tyld im eth yl-
silyloxy)p h en yleth yn yl]ben zen e (3b). To a mixture of 1a
(1.10 g, 2.00 mmol), PdCl2(PPh3)2 (140 mg, 0.20 mmol), CuI
(76.2 mg, 0.40 mmol), and PPh3 (105 mg, 0.40 mmol) under
J . Org. Chem, Vol. 69, No. 7, 2004 2493

Kobayashi and Kobayashi
an argon atmosphere were added Et3N (50 mL) and then a
solution of 2b (3.72 g, 16.0 mmol) in Et3N (20 mL). The
resulting mixture was stirred at refluxing temperature for 109
h. After evaporation of Et3N, the residue was triturated with
CHCl3 and filtered. The filtrate was partitioned between CHCl3
and H2O, where the aqueous layer was neutralized with
diluted HCl. The organic layer was washed with H2O and brine
and dried over Na2SO4. After evaporation of solvent, the
residue was subjected to column chromatography on silica gel
eluted with hexane-CHCl3 (1.7:1) to give slightly crude 3b,
which was dissolved in a minimum amount of CHCl3 and
poured into hexane to give 3b (2.00 g, 68% yield). Pale yellow
4.42 (q, J ) 7.1 Hz, 4H), 1.43 (t, J ) 7.1 Hz, 6H); 13C NMR
(CDCl3) δ 165.9, 134.0, 131.7, 130.9, 129.6, 129.1, 126.8, 126.4,
109.7, 98.2, 91.3, 61.3, 14.3; UV-vis (CHCl3) λmax (log ꢀ) 315.1
(4.87), 335.2 nm (4.81).
1,3,5-Tr ib r om o-2,4,6-t r is[p -(et h oxyca r b on yl)p h en yl-
eth yn yl]ben zen e (5). Pale yellow solid; mp 232 °C; 1H NMR
(CDCl3) δ 8.03 (d, J ) 8.2 Hz, 6H), 7.66 (d, J ) 8.2 Hz, 6H),
4.40 (q, J ) 7.1 Hz, 6H), 1.42 (t, J ) 7.1 Hz, 9H); 13C NMR
(CDCl3) δ 165.9, 131.7, 130.9, 129.5, 128.9, 127.5, 126.6, 98.7,
89.9, 61.3, 14.3; UV-vis (CHCl3) λmax (log ꢀ) 316.3 (5.04), 337.3
nm (5.06).
1,3-Dibr om o-2,4,5,6-tetr a k is[p-(eth oxyca r bon yl)p h en -
yleth yn yl]ben zen e (6). Yellow solid; mp 209 °C; 1H NMR
(CDCl3) δ 8.09-8.03 (m, 8H), 7.70 (d, J ) 9.0 Hz, 2H), 7.67 (d,
J ) 8.5 Hz, 4H), 7.61 (d, J ) 8.4 Hz, 2H), 4.42 (q, J ) 7.1 Hz,
8H), 1.43 (t, J ) 7.1 Hz, 12H); 13C NMR (CDCl3) δ 165.74,
165.67, 165.6, 131.8, 131.6, 131.1, 131.0, 130.9, 129.7, 129.6,
129.5, 128.9, 128.7, 128.2, 127.4, 126.93, 126.87, 126.7, 99.9,
99.7, 98.7, 89.54, 89.46, 89.4, 61.2, 14.3; UV-vis (CHCl3) λmax
(log ꢀ) 329.8 nm (5.06).
1
solid; mp 275 °C dec; H NMR (CDCl3) δ 7.52 (d, J ) 8.6 Hz,
12H), 6.84 (d, J ) 8.6 Hz, 12H), 1.02 (s, 54H), 0.24 (s, 36H);
13C NMR (CDCl3) δ 156.4, 133.3, 127.0, 120.3, 116.2, 99.1, 86.8,
25.6, 18.3, -4.4; IR (KBr) ν 2204, 1602, 1509, 1264 cm-1. Anal.
Calcd for C90H114O6Si6: C, 74.02; H, 7.87. Found: C, 73.80;
H, 7.93.
Hexa k is(p-m eth oxyp h en yleth yn yl)ben zen e (3a ). Reac-
tion conditions: 1a (1.10 g, 2.00 mmol), PdCl2(PPh3)2 (140 mg,
0.20 mmol), CuI (76.2 mg, 0.40 mmol), PPh3 (105 mg, 0.40
mmol), Et3N (30 mL), and a solution of 2a (2.12 g, 16.0 mmol)
in Et3N (15 mL) at refluxing temperature for 112 h. Purifica-
tion: column chromatography on silica gel eluted with hex-
ane-CHCl3 (1:4.5) followed by reprecipitation with CHCl3-
hexane; 68% yield. Yellow solid; mp 320 °C dec; 1H NMR
(CDCl3) δ 7.58 (d, J ) 8.8 Hz, 12H), 6.91 (d, J ) 8.8 Hz, 12H),
3.86 (s, 18H); 13C NMR (CDCl3) δ 160.0, 133.3, 127.0, 115.6,
Th e Son oga sh ir a Cou p lin g Rea ction of 1b w ith 2b
(Ta ble 1, en tr y 4). To a mixture of 1b (2.07 g, 3.00 mmol),
PdCl2(PPh3)2 (63.2 mg, 0.090 mmol), CuI (34.3 mg, 0.18 mmol),
and PPh3 (47.2 mg, 0.18 mmol) under an argon atmosphere
were added Et3N (35 mL) and then a solution of 2b (2.58 g,
11.1 mmol; 3.7 equiv) in Et3N (15 mL). The resulting mixture
was stirred at refluxing temperature for 40 h. After the
solution was cooled to room temperature, Et2O was added to
the reaction mixture, which was filtered. After evaporation of
the filtrate, the residue was partitioned between CHCl3 and
H2O, where the aqueous layer was neutralized with diluted
HCl. The organic layer was washed with H2O and brine and
dried over Na2SO4. After evaporation of solvent, the residue
was subjected to column chromatography on silica gel eluted
with hexane-CH2Cl2 (7.5:1) to give 9 (524 mg, 17% yield), with
hexane-CH2Cl2 (4:1) to separate crude 10, and then with
hexane-CH2Cl2 (3:1) to give 11 (182 mg, 5% yield). The crude
10 was purified by reprecipitation with CHCl3-EtOH to give
10 (1.24 g, 36% yield).
114.1, 99.0, 86.6, 55.4; IR (KBr) ν 2201, 1605, 1513, 1251 cm-1
.
Anal. Calcd for C60H42O6: C, 83.90; H, 4.93. Found: C, 83.90;
H, 5.01.
H exa k is[p -(et h oxyca r b on yl)p h en ylet h yn yl]b en zen e
(3d ). Reaction conditions: 1a (1.10 g, 2.00 mmol), PdCl2(PPh3)2
(140 mg, 0.20 mmol), CuI (76.2 mg, 0.40 mmol), PPh3 (105 mg,
0.40 mmol), Et3N (30 mL), and a solution of 2c (2.79 g, 16.0
mmol) in Et3N (15 mL) at refluxing temperature for 50 h.
Purification: column chromatography on silica gel eluted with
CHCl3-EtOAc (1:1) followed by reprecipitation with CHCl3-
hexane. Yield 73%; yellow solid; mp 290 °C dec; 1H NMR
(CDCl3, 5 mM) δ 7.89 (d, J ) 8.3 Hz, 12H), 7.47 (d, J ) 8.3
Hz, 12H), 4.41(q, J ) 7.2 Hz, 12H), 1.44 (t, J ) 7.2 Hz, 18H);
13C NMR (CDCl3) δ 165.5, 131.4, 130.4, 129.3, 127.6, 127.1,
When 2.8 equiv of 2b was used under the same conditions,
a mixture of 7, 8, 9, and 10 was produced (Table 1, entry 3),
which was subjected to column chromatography on silica gel
eluted with hexane-CH2Cl2 (20:1) to give 7 (14% yield), with
hexane-CH2Cl2 (10:1) to separated crude 8, with hexane-CH2-
Cl2 (7.5:1) to give 9 (12% yield), and then with hexane-CH2-
Cl2 (4:1) to give 10 (3% yield). The crude 8 was purified by
reprecipitation with hexane-EtOH to give 8 (37% yield). On
the other hand, the reaction of 1b with 3.7 equiv of 2b at 55
°C for 150 h followed by the additional reaction using 0.75
equiv of 2b at 55 °C for 90 h gave 8, 9, and 10 in 20%, 47%,
and 13% yields, respectively (Table 1, entry 5).
99.0, 89.6, 61.2, 14.3; IR (KBr) ν 2210, 1723, 1605, 1290 cm-1
.
Anal. Calcd for C72H54O12: C, 77.82; H, 4.90. Found: C, 77.72;
H, 4.94.
Th e Son oga sh ir a Cou p lin g Rea ction of 1b w ith 2c
(Ta ble 1, En tr y 1). To a mixture of 1b (1.00 g, 1.44 mmol),
PdCl2(PPh3)2 (30.3 mg, 0.043 mmol), CuI (16.5 mg, 0.086
mmol), and PPh3 (22.7 mg, 0.086 mmol) under an argon
atmosphere were added Et3N (40 mL) and then a solution of
2c (1.00 g, 5.74 mmol) in Et3N (15 mL). The resulting mixture
was stirred at refluxing temperature for 24 h. After evapora-
tion of Et3N, the residue was triturated with CHCl3 and
filtered. The filtrate was partitioned between CHCl3 and H2O,
where the aqueous layer was neutralized with diluted HCl.
The organic layer was washed with H2O and brine and dried
over Na2SO4. After evaporation of solvent, the residue was
subjected to column chromatography on silica gel eluted with
hexane-CHCl3 (1:3) to separate the fractions containing 4 and
the fractions containing 5 and 6. The crude 4 was purified by
repeated recrystallization from CHCl3-hexane to give 4 (115
mg, 10% yield). The mixture of 5 and 6 was separated and
purified with recycle preparative GPC with CHCl3 as an eluent
to give 5 (247 mg, 21% yield) and 6 (267 mg, 20% yield).
1,3,5-Tr ibr om o-2-[p-(ter t-bu tyld im eth ylsilyloxy)p h en -
yleth yn yl]-4,6-d iiod oben zen e (7). White solid; mp 153 °C;
1H NMR (CDCl3) δ 7.48 (d, J ) 8.6 Hz, 2H), 6.85 (d, J ) 8.6
Hz, 2H), 1.00 (s, 9H), 0.23 (s, 6H); 13C NMR (CDCl3) δ 157.1,
137.6, 133.7, 133.5, 126.5, 120.4, 114.5, 107.4, 99.2, 90.1, 25.6,
18.2, -4.4; UV-vis (CHCl3) λmax (log ꢀ) 323.4 (4.45), 338.3 nm
(4.42).
1,3,5-Tr ibr om o-2,4-bis[p-(ter t-bu tyld im eth ylsilyloxy)-
p h en yleth yn yl]-6-iod oben zen e (8). White solid; mp 174 °C;
1H NMR (CDCl3) δ 7.51 (d, J ) 8.6 Hz, 4H), 6.86 (d, J ) 8.6
Hz, 4H), 1.00 (s, 18H), 0.23 (s, 12H); 13C NMR (CDCl3) δ 157.0,
133.4, 132.4, 128.3, 127.4, 120.4, 114.8, 109.2, 99.6, 88.4, 25.6,
18.2, -4.4; UV-vis (CHCl3) λmax (log ꢀ) 324.1 (4.76), 335.6 nm
(4.76).
On the other hand, the reaction of 1b with 2.5 equiv of 2c
at refluxing temperature for 14 h followed by the additional
reaction using 1.4 equiv of 2c at 55 °C for 24 h gave 4, 5, and
6 in 32%, 17%, and 32% yields, respectively (Table 1, entry
2).
1,3,5-Tr ib r om o-2,4,6-t r is[p -(ter t-b u t yld im et h ylsilyl-
oxy)p h en yleth yn yl]ben zen e (9). White solid; mp 163 °C;
1H NMR (CDCl3) δ 7.55 (d, J ) 8.6 Hz, 6H), 6.87 (d, J ) 8.6
Hz, 6H), 1.00 (s, 27H), 0.24 (s, 18H); 13C NMR (CDCl3) δ 156.9,
133.4, 127.8, 127.2, 120.4, 115.1, 99.7, 87.1, 25.6, 18.2, -4.4;
UV-vis (CHCl3) λmax (log ꢀ) 336.9 nm (5.00).
1,3,5-Tr ibr om o-2,4-bis[p-(et h oxyca r b on yl)p h en ylet h -
1
yn yl]-6-iod oben zen e (4). White solid; mp 238 °C; H NMR
(CDCl3) δ 8.08 (d, J ) 8.2 Hz, 4H), 7.68 (d, J ) 8.2 Hz, 4H),
2494 J . Org. Chem., Vol. 69, No. 7, 2004

Hexakis(p-substituted-phenylethynyl)benzenes
1,3-Dib r om o-2,4,5,6-t et r a k is[p -(ter t-b u t yld im et h ylsi-
lyloxy)p h en yleth yn yl]ben zen e (10). Yellow solid; mp 218
°C; H NMR (CDCl3) δ 7.55 (d, J ) 8.6 Hz, 2H), 7.53 (d, J )
7.1 Hz, 6H), 1.44 (t, J ) 7.1 Hz, 9H), 1.02 (s, 27 H), 0.26 (s,
18H); 13C NMR (CDCl3) δ 166.0, 156.7, 133.4, 131.6, 130.1,
129.4, 128.7, 127.9, 126.0, 120.4, 115.8, 100.4, 97.9, 90.3, 86.4,
61.1, 25.6, 18.2, 14.3, -4.4; IR (KBr) ν 2209, 1719, 1602, 1509,
1274 cm-1. Anal. Calcd for C81H84O9Si3: C, 75.66; H, 6.58.
Found: C, 75.64; H, 6.65.
1
8.6 Hz, 4H), 7.46 (d, J ) 8.6 Hz, 2H), 6.87 (d, J ) 8.6 Hz, 2H),
6.85 (d, J ) 8.6 Hz, 4H), 6.82 (d, J ) 8.6 Hz, 2H), 1.00 (s,
36H), 0.24 (s, 24H); 13C NMR (CDCl3) δ 156.9, 156.69, 156.66,
133.44, 133.42, 133.3, 128.4, 127.6, 127.3, 127.0, 120.4, 115.7,
115.6, 115.3, 100.4, 100.1, 99.1, 87.6, 86.8, 86.5, 25.6, 18.2,
-4.4; UV-vis (CHCl3) λmax (log ꢀ) 337.8 nm (5.02).
1-Br om o-2,3,4,5,6-p en ta k is[p-(ter t-bu tyld im eth ylsilyl-
oxy)p h en yleth yn yl]ben zen e (11). Yellow solid; mp 233 °C;
1H NMR (CDCl3) δ 7.57-7.50 (m, 10H), 6.88-6.83 (m, 10H),
1.05 (s, 45H), 0.28 (s, 30H); 13C NMR (CDCl3) δ 156.6, 156.5,
156.4, 133.4, 133.3, 127.7, 127.2, 127.0, 126.7, 120.3, 116.2,
116.1, 115.8, 99.7, 99.6, 98.6, 87.2, 86.9, 86.3, 25.6, 18.2, -4.4;
UV-vis (CHCl3) λmax (log ꢀ) 351.4 nm (5.12).
Th e Son oga sh ir a Cou p lin g Rea ction of 1b w ith 2d
(Ta ble 1, En tr y 6). To a mixture of 1b (2.33 g, 3.40 mmol),
PdCl2(PPh3)2 (70.8 mg, 0.10 mmol), CuI (38.5 mg, 0.20 mmol),
and PPh3 (53.0 mg, 0.20 mmol) under an argon atmosphere
were added Et3N (40 mL) and then a solution of 2d (4.25 g,
12.4 mmol) in Et3N (15 mL). The resulting mixture was stirred
at refluxing temperature for 43 h. After the solution was cooled
to room temperature, Et2O was added to the reaction mixture,
which was filtered. After evaporation of the filtrate, the residue
was partitioned between CHCl3 and H2O. The organic layer
was washed with H2O and brine and dried over Na2SO4. After
evaporation of solvent, the residue was subjected to column
chromatography on silica gel eluted with hexane-CHCl3 (3.3:
1) to give 12 (2.57 g, 57% yield) and then with hexane-CHCl3
(2:1) to separate the fractions containing 13. The crude 13 was
purified with recycle preparative GPC with CHCl3 as an eluent
to give 13 (461 mg, 9% yield).
1,2,3,4,5-P en ta k is[p-(ter t-bu tyld im eth ylsilyloxy)p h en -
yle t h yn yl]-6-[p -(e t h oxyca r b on yl)p h e n yle t h yn yl]b e n -
zen e (3f). Reaction conditions: 11 (138 mg, 0.11 mmol),
PdCl2(PPh3)2 (5.2 mg, 0.0074 mmol), CuI (2.8 mg, 0.015 mmol),
PPh3 (3.9 mg, 0.015 mmol), Et3N (10 mL), and a solution of
2c (50.0 mg, 0.29 mmol) in Et3N (5 mL) at refluxing temper-
ature for 48 h. Purification: column chromatography on silica
gel eluted with hexane-CHCl3 (1:1.5) followed by recycle
1
preparative GPC. Yield 61%; yellow solid; mp 255 °C dec; H
NMR (CDCl3) δ 8.05 (d, J ) 8.4 Hz, 2H), 7.67 (d, J ) 8.4 Hz,
2H), 7.53-7.49 (m, 10H), 6.85-6.82 (m, 10H), 4.42 (q, J ) 7.1
Hz, 2H), 1.44 (t, J ) 7.1 Hz, 3H), 1.02 (s, 45 H), 0.26 (s, 30H);
13C NMR (CDCl3) δ 166.0, 156.6, 156.50, 156.46, 133.4, 133.35,
133.31, 131.6, 130.1, 129.5, 128.0, 127.8, 127.4, 127.1, 125.8,
120.4, 120.3, 116.1, 116.0, 99.6, 99.5, 99.3, 97.5, 90.6, 86.7, 86.6,
86.5, 61.2, 25.6, 18.2, 14.3, -4.4; IR (KBr) ν 2206, 1719, 1602,
1509, 1272 cm-1. Anal. Calcd for C87H104O7Si5: C, 74.52; H,
7.48. Found: C, 74.46; H, 7.56.
1,2,3,5-Tetr a k is[p-(ter t-bu tyld im eth ylsilyloxy)p h en yl-
eth yn yl]-4,6-bis[p-(eth oxyca r bon yl)p h en yleth yn yl]ben -
zen e (3g). Reaction conditions: 4 (164 mg, 0.21 mmol),
PdCl2(PPh3)2 (11.7 mg, 0.017 mmol), CuI (6.4 mg, 0.033 mmol),
PPh3 (8.8 mg, 0.033 mmol), Et3N (20 mL), and a solution of
2b (364 mg, 1.57 mmol) in Et3N (10 mL) at refluxing temper-
ature for 65 h. Purification: column chromatography on silica
gel eluted with hexane-CHCl3 (1:2.5) followed by recycle
1
preparative GPC. Yield 56%; yellow solid; mp 295 °C dec; H
NMR (CDCl3) δ 8.05 (d, J ) 8.2 Hz, 4H), 7.68 (d, J ) 8.2 Hz,
4H), 7.51 (d, J ) 8.7 Hz, 2H), 7.50 (d, J ) 8.7 Hz, 4H), 7.49 (d,
J ) 8.7 Hz, 2H), 6.85 (d, J ) 8.7 Hz, 2H), 6.84 (d, J ) 8.7 Hz,
6H), 4.42 (q, J ) 7.2 Hz, 4H), 1.43 (t, J ) 7.2 Hz, 6H), 1.02 (s,
36H), 0.25 (s, 24H); 13C NMR (CDCl3) δ 166.1, 156.8, 156.7,
156.6, 133.4, 133.3, 131.6, 130.2, 129.6, 128.3, 127.9, 127.8,
127.2, 125.9, 120.5, 120.42, 120.36, 116.0, 115.8, 115.7, 100.1,
99.6, 97.7, 90.3, 86.5, 86.3, 61.2, 25.6, 18.3, 14.3, -4.4; IR (KBr)
ν 2208, 1719, 1602, 1509, 1273 cm-1. Anal. Calcd for C84H94O8-
Si4: C, 75.07; H, 7.05. Found: C, 75.20; H, 7.05.
1,3,5-Tr ibr om o-2,4,6-tr is[p-(N,N-d i-n -octyla m in o)p h en -
yleth yn yl]ben zen e (12). Yellow solid; mp 59.4 °C; H NMR
1
(CDCl3) δ 7.48 (d, J ) 8.9 Hz, 6H), 6.60 (d, J ) 8.9 Hz, 6H),
3.30 (t, J ) 7.4 Hz, 12H), 1.60-1.50 (m, 12H), 1.35-1.25 (m,
60H), 0.90 (t, J ) 6.9 Hz, 18H); 13C NMR (CDCl3) δ 148.6,
133.2, 128.1, 125.6, 111.2, 107.8, 101.3, 86.8, 51.0, 31.8, 29.5,
29.3, 27.2, 27.1, 22.6, 14.1; UV-vis (CHCl3) λmax (log ꢀ) 395.2
nm (5.09).
1,3-Dibr om o-2,4,5,6-tetr a k is[p-(N,N-d i-n -octyla m in o)-
p h en yleth yn yl]ben zen e (13). Dark red solid; mp 53 °C; 1H
NMR (CDCl3) δ 7.52-7.46 (m, 8H), 6.63-6.57 (m, 8H), 3.31
(t, J ) 7.3 Hz, 16H), 1.65-1.55 (m, 16H), 1.36-1.29 (m, 80H),
0.92 (t, J ) 6.6 Hz, 24H); 13C NMR (CDCl3) δ 148.5, 148.3,
133.4, 127.4, 127.3, 127.1, 125.7, 111.2, 109.0, 108.7, 108.2,
101.7, 101.3, 100.4, 87.4, 86.7, 86.3, 51.0, 31.8, 29.5, 29.3, 27.25,
27.16, 22.6, 14.1; UV-vis (CHCl3) λmax (log ꢀ) 393.2 nm (5.03).
Typ ica l P r oced u r e for th e Son oga sh ir a Cou p lin g
Rea ction of Ha lid es of Mon o-, Bis-, Tr is-, Tetr a k is-, or
P en t a k is(p -su b st it u t ed -p h en ylet h yn yl)b en zen es 4-13
w ith 2: 1,3,5-Tr is[p-(ter t-bu tyld im eth ylsilyloxy)p h en yl-
eth yn yl]-2,4,6-tr is[p-(eth oxycar bon yl)ph en yleth yn yl]ben -
zen e (3h ). To a mixture of 5 (233 mg, 0.28 mmol), PdCl2(PPh3)2
(14.7 mg, 0.021 mmol), CuI (8.0 mg, 0.042 mmol), and PPh3
(11.0 mg, 0.042 mmol) under an argon atmosphere were added
Et3N (25 mL) and then a solution of 2b (391 mg, 1.68 mmol)
in Et3N (15 mL). The resulting mixture was stirred at refluxing
temperature for 65 h. After evaporation of Et3N, the residue
was triturated with CHCl3 and filtered. The filtrate was
partitioned between CHCl3 and H2O, where the aqueous layer
was neutralized with diluted HCl. The organic layer was
washed with H2O and brine and dried over Na2SO4. After
evaporation of solvent, the residue was subjected to column
chromatography on silica gel eluted with hexane-CHCl3 (1:
2.5) to separate the fractions containing 3h . The crude 3h was
purified by reprecipitation with CHCl3-hexane followed by
recycle preparative GPC with CHCl3 as an eluent to give 3h
(252 mg, 70% yield). Yellow solid; mp 312 °C dec; 1H NMR
(CDCl3) δ 8.06 (d, J ) 8.3 Hz, 6H), 7.69 (d, J ) 8.3 Hz, 6H),
7.50 (d, J ) 8.6 Hz, 6H), 6.86 (d, J ) 8.6 Hz, 6H), 4.42 (q, J )
1,3-Bis[p-(ter t-bu tyld im eth ylsilyloxy)p h en yleth yn yl]-
2,4,5,6-t et r a k is[p -(et h oxyca r b on yl)p h en ylet h yn yl]b en -
zen e (3i). Reaction conditions: 6 (267 mg, 0.29 mmol),
PdCl2(PPh3)2 (13.6 mg, 0.019 mmol), CuI (7.3 mg, 0.039 mmol),
PPh3 (10.1 mg, 0.039 mmol), Et3N (20 mL), and a solution of
2b (287 mg, 1.24 mmol) in Et3N (10 mL) at refluxing temper-
ature for 43 h. Purification: column chromatography on silica
gel eluted with CHCl3 followed by reprecipitation with CHCl3-
hexane and then recycle preparative GPC. Yield 63%; yellow
1
solid; mp 265 °C dec; H NMR (CDCl3) δ 8.01 (d, J ) 8.2 Hz,
8H), 7.62 (d, J ) 8.2 Hz, 8H), 7.46 (d, J ) 8.5 Hz, 4H), 6.81 (d,
J ) 8.5 Hz, 4H), 4.42 (q, J ) 7.2 Hz, 8H), 1.44 (t, J ) 7.2 Hz,
12H), 1.02 (s, 18 H), 0.25 (s, 12H); 13C NMR (CDCl3) δ 165.82,
165.75, 165.7, 156.6, 133.3, 131.6, 131.5, 130.1, 130.0, 129.34,
129.31, 128.7, 127.8, 127.7, 127.5, 127.4, 126.8, 126.3, 120.2,
115.7, 100.6, 98.5, 98.2, 98.1, 90.4, 90.2, 90.1, 86.5, 61.1, 25.6,
18.2, 14.3, -4.4; IR (KBr) ν 2207, 1719, 1603, 1509, 1275 cm-1
.
Anal. Calcd for C78H74O10Si2: C, 76.32; H, 6.08. Found: C,
76.34; H, 6.17.
1-[p-(ter t-Bu t yld im et h ylsilyloxy)p h en ylet h yn yl]-2,3,-
4,5,6-p en t a k is[p -(et h oxyca r b on yl)p h en ylet h yn yl]b en -
zen e (3j). Reaction conditions: 7 (206 mg, 0.26 mmol),
PdCl2(PPh3)2 (14.4 mg, 0.021 mmol), CuI (7.9 mg, 0.042 mmol),
PPh3 (10.8 mg, 0.041 mmol), Et3N (20 mL), and a solution of
2c (405 mg, 2.33 mmol) in Et3N (10 mL) at refluxing temper-
ature for 91 h. Purification: column chromatography on silica
gel eluted with CHCl3 followed by reprecipitation with CHCl3-
hexane and then recycle preparative GPC. Yield 86%; yellow
1
solid; mp 240 °C dec; H NMR (CDCl3) δ 7.99 (d, J ) 8.1 Hz,
J . Org. Chem, Vol. 69, No. 7, 2004 2495

Kobayashi and Kobayashi
10H), 7.59 (d, J ) 8.1 Hz, 10H), 7.43 (d, J ) 8.5 Hz, 2H), 6.79
(d, J ) 8.5 Hz, 2H), 4.42 (q, J ) 7.1 Hz, 10H), 1.45 (t, J ) 7.1
Hz, 15H), 1.02 (s, 9H), 0.25 (s, 6H); 13C NMR (CDCl3) δ 165.62,
165.55, 165.5, 156.6, 133.3, 131.5, 131.41, 131.37, 130.1, 130.0,
129.2, 128.8, 127.5, 127.41, 127.35, 127.3, 127.1, 126.7, 120.1,
115.5, 100.8, 98.6, 98.5, 98.4, 90.1, 89.90, 89.86, 86.4, 61.1, 25.6,
NMR (CDCl3) δ 7.73 (d, J ) 8.2 Hz, 6H), 7.52 (d, J ) 8.2 Hz,
6H), 7.46 (d, J ) 8.8 Hz, 6H), 6.59 (d, J ) 8.8 Hz, 6H), 5.87 (s,
3H), 4.21-4.14 (m, 6H), 4.13-4.04 (m, 6H), 3.31 (t, J ) 7.3
Hz, 12H), 1.67-1.55 (m, 12H), 1.36-1.29 (m, 60H), 0.91 (t,
J ) 6.9 Hz, 18H); 13C NMR (75 MHz, CDCl3) δ 148.4, 137.8,
133.2, 131.8, 128.8, 126.5, 124.7, 124.6, 111.2, 108.6, 103.4,
101.7, 97.5, 88.7, 86.0, 65.3, 51.0, 31.8, 29.5, 29.3, 27.3, 27.2,
22.7, 14.1; IR (KBr) ν 2185, 1603, 1523, 812 cm-1. Anal. Calcd
for C111H141N3O6: C, 82.64; H, 8.81; N, 2.60. Found: C, 82.81;
H, 8.71; N, 2.60.
18.2, 14.3, -4.4; IR (KBr) ν 2202, 1719, 1604, 1509, 1275 cm-1
.
Anal. Calcd for C75H64O11Si: C, 77.03; H, 5.52. Found: C,
76.91; H, 5.69.
1,3,5-Tr is[p-(ter t-bu tyldim eth ylsilyloxy)ph en yleth yn yl]-
2,4,6-tr is(p-n itr oph en yleth yn yl)ben zen e (3l). Reaction con-
ditions: 9 (355 mg, 0.35 mmol), PdCl2(PPh3)2 (18.6 mg, 0.027
mmol), CuI (10.1 mg, 0.053 mmol), PPh3 (13.9 mg, 0.053
mmol), Et3N (20 mL), and a solution of 2e (322 mg, 2.20 mmol)
in Et3N (15 mL) at refluxing temperature for 74 h. Purifica-
tion: column chromatography on silica gel eluted with hex-
ane-CHCl3 (1.2:1) followed by reprecipitation with CHCl3-
hexane. Yield 54%; yellow solid; mp 320 °C dec; 1H NMR
(CDCl3) δ 8.21 (d, J ) 8.8 Hz, 6H), 7.70 (d, J ) 8.8 Hz, 6H),
7.45 (d, J ) 8.6 Hz, 6H), 6.85 (d, J ) 8.6 Hz, 6H), 1.01 (s,
27H), 0.26 (s, 18 H); 13C NMR (CDCl3) δ 157.2, 147.4, 133.3,
132.4, 129.8, 129.4, 125.5, 123.8, 120.1, 115.1, 101.4, 96.7, 92.1,
85.9, 25.6, 18.3, -4.3; IR (KBr) ν 2206, 1599, 1521, 1342, 1267
cm-1. Anal. Calcd for C72H69N3O9Si3: C, 71.79; H, 5.77; N, 3.49.
Found: C, 71.50; H, 5.75; N, 3.34.
1,2,3,5-Tetr akis[p-(N,N-di-n -octylam in o)ph en yleth yn yl]-
4,6-bis[p-(1,3-d ioxola n -2-yl)p h en yleth yn yl]ben zen e (3p ).
Reaction conditions: 13 (299 mg, 0.19 mmol), PdCl2(PPh3)2 (7.9
mg, 0.011 mmol), CuI (4.3 mg, 0.023 mmol), PPh3 (5.9 mg,
0.023 mmol), Et3N (15 mL), and a solution of 2f (158 mg, 0.91
mmol) in Et3N (10 mL) at refluxing temperature for 31 h.
Purification: column chromatography on silica gel eluted with
hexane-CHCl3 (1:1.5) followed by recycle preparative GPC.
1
Yield 36%; brown solid; mp 54.5 °C; H NMR (CDCl3) δ 7.72
(d, J ) 8.2 Hz, 4H), 7.54 (d, J ) 8.7 Hz, 2H), 7.51 (d, J ) 8.2
Hz, 4H), 7.49 (d, J ) 8.8 Hz, 4H), 7.45 (d, J ) 8.9 Hz, 2H),
6.63-6.57 (m, 8H), 5.87(s, 2H), 4.22-4.13 (m, 4H), 4.12-4.04
(m, 4H), 3.31 (t, J ) 7.3 Hz, 16H), 1.67-1.55 (m, 16H), 1.36-
1.29 (m, 80H), 0.91 (t, J ) 6.9 Hz, 24H); 13C NMR (CDCl3) δ
148.3, 148.2, 148.1, 137.7, 133.3, 133.2, 131.8, 128.0, 127.6,
126.4, 126.1, 124.9, 124.7, 111.2, 109.5, 109.1, 108.9, 103.5,
101.1, 100.9, 100.4, 97.2, 89.0, 86.3, 86.1, 65.3, 51.0, 31.8, 29.5,
29.3, 27.3, 27.2, 22.6, 14.1; IR (KBr) ν 2187, 1604, 1523, 812
cm-1. Anal. Calcd for C124H170N4O4‚H2O: C, 82.80; H, 9.64; N,
3.11. Found: C, 82.71; H, 9.45; N, 3.07.
1,3,5-Tr is[p-(N,N-di-n -octylam in o)ph en yleth yn yl]-2,4,6-
tr is(p-n itr op h en yleth yn yl)ben zen e (3m ). Reaction condi-
tions: 12 (1.68 g, 1.30 mmol), PdCl2(PPh3)2 (66.5 mg, 0.095
mmol), CuI (36.0 mg, 0.19 mmol), PPh3 (49.6 mg, 0.19 mmol),
Et3N (80 mL), and a solution of 2e (1.15 g, 7.80 mmol) in Et3N
(30 mL) at refluxing temperature for 40 h. Purification:
column chromatography on silica gel eluted with hexane-
CHCl3 (1.2:1) followed by reprecipitation with Et2O-MeOH.
Yield 50%; orange red solid; mp 61 °C; 1H NMR (CDCl3, 10
mM) δ 8.16 (d, J ) 8.9 Hz, 6H), 7.71 (d, J ) 8.9 Hz, 6H), 7.38
(d, J ) 8.9 Hz, 6H), 6.56 (d, J ) 8.9 Hz, 6H), 3.32 (t, J ) 7.3
Hz, 12H), 1.67-1.55 (m, 12H), 1.36-1.29 (m, 60H), 0.90 (t,
J ) 6.9 Hz, 18H); 13C NMR (CDCl3) δ 148.7, 146.7, 133.3,
132.2, 130.7, 130.2, 123.6, 123.4, 111.0, 108.2, 103.1, 95.9, 93.8,
86.3, 50.9, 31.8, 29.5, 29.4, 27.3, 27.2, 22.7, 14.1; IR (KBr) ν
1,3,5-Tr is[p-(N,N-di-n -octylam in o)ph en yleth yn yl]-2,4,6-
tr is(p-for m ylp h en yleth yn yl)ben zen e (3q). To a solution of
3o (170 mg, 0.11 mmol) in THF (4 mL) under an argon
atmosphere was added 1 M HCl (1.3 mL). After being stirred
at room temperature for 16 h, the reaction mixture was
neutralized with aqueous Na2CO3 and extracted with Et2O.
The organic layer was washed with H2O and brine and dried
over Na2SO4. After evaporation of solvents, the residue was
subjected to column chromatography on silica gel eluted with
hexane-EtOAc (10:1) followed by recycle preparative GPC to
give 3q (128 mg, 82% yield). Deep orange solid; mp 84 °C; 1H
NMR (CDCl3) δ 10.04 (s, 3H), 7.88 (d, J ) 8.2 Hz, 6H), 7.80
(d, J ) 8.2 Hz, 6H), 7.45 (d, J ) 8.9 Hz, 6H), 6.59 (d, J ) 8.9
Hz, 6H), 3.32 (t, J ) 7.4 Hz, 12H), 1.67-1.55 (m, 12H), 1.36-
1.29 (m, 60H), 0.90 (t, J ) 6.9 Hz, 18H); 13C NMR (CDCl3) δ
191.4, 148.6, 135.4, 133.3, 132.2, 130.0, 129.8, 129.6, 124.0,
111.2, 108.1, 102.9, 97.0, 92.2, 85.9, 51.0, 31.8, 29.5, 29.3, 27.2,
2193, 1604, 1522, 1337, 851, 813 cm-1. Anal. Calcd for C102
126N6O6: C, 79.96; H, 8.29; N, 5.49. Found: C, 79.86; H, 8.26;
N, 5.38.
-
H
1,2,3,5-Tetr akis[p-(N,N-di-n -octylam in o)ph en yleth yn yl]-
4,6-bis(p-n itr op h en yleth yn yl)ben zen e (3n ). Reaction con-
ditions: 13 (240 mg, 0.15 mmol), PdCl2(PPh3)2 (8.4 mg, 0.012
mmol), CuI (3.4 mg, 0.018 mmol), PPh3 (4.7 mg, 0.018 mmol),
Et3N (15 mL), and a solution of 2e (95.2 mg, 0.65 mmol) in
Et3N (10 mL) at refluxing temperature for 60 h. Purification:
column chromatography on silica gel eluted with hexane-
CHCl3 (1.5:1) followed by recycle preparative GPC. Yield 8%;
27.1, 22.6, 14.1; IR (KBr) ν 2725, 2189, 1702, 1601, 1523 cm-1
.
Anal. Calcd for C105H129N3O3: C, 85.14; H, 8.78; N, 2.84.
Found: C, 84.91; H, 8.82; N, 2.69.
1,2,3,5-Tetr akis[p-(N,N-di-n -octylam in o)ph en yleth yn yl]-
4,6-bis(p-for m ylp h en yleth yn yl)ben zen e (3r ). Yield 74%;
1
red solid; mp 57 °C; H NMR (CDCl3) δ 8.23 (d, J ) 8.9 Hz,
1
4H), 7.77 (d, J ) 8.9 Hz, 4H), 7.51 (d, J ) 8.9 Hz, 2H), 7.47 (d,
J ) 8.9 Hz, 4H), 7.43 (d, J ) 8.9 Hz, 2H), 6.61 (d, J ) 8.9 Hz,
8H), 3.32 (t, J ) 7.4 Hz, 16H), 1.67-1.55 (m, 16H), 1.36-1.29
(m, 80H), 0.90 (t, J ) 7.0 Hz, 24H); 13C NMR (CDCl3) δ 148.6,
148.5, 148.3, 146.9, 133.3, 133.1, 132.3, 130.8, 129.2, 128.1,
126.5, 123.7, 123.6, 111.2, 109.0, 108.6, 108.2, 102.4, 101.8,
101.3, 95.5, 93.7, 86.2, 86.1, 85.7, 51.0, 31.8, 29.5, 29.3, 27.3,
27.2, 22.6, 14.1; IR (KBr) ν 2192, 1604, 1521, 1338, 853, 810
cm-1. Anal. Calcd for C118H160N6O4: C, 82.09; H, 9.34; N, 4.87.
Found: C, 82.27; H, 9.52; N, 4.77.
deep red solid; mp 49.7 °C; H NMR (CDCl3) δ 10.05 (s, 2H),
7.90 (d, J ) 8.3 Hz, 4H), 7.81 (d, J ) 8.3 Hz, 4H), 7.55-7.43
(m, 8H), 6.62-6.58 (m, 8H), 3.31 (t, J ) 7.2 Hz, 16H), 1.67-
1.56 (m, 16H), 1.35-1.28 (m, 80H), 0.91 (t, J ) 6.9 Hz, 24H);
13C NMR (CDCl3) δ 191.5, 148.5, 148.4, 148.2, 135.3, 133.3,
133.1, 132.2, 130.2, 129.6, 128.8, 127.9, 126.4, 123.9, 111.2,
109.1, 108.7, 108.4, 102.0, 101.5, 101.0, 96.5, 92.6, 86.3, 86.1,
85.9, 51.0, 31.8, 29.5, 29.3, 27.2, 27.1, 22.6, 14.1; IR (KBr) ν
2728, 2187, 1703, 1604, 1522, 811 cm-1. Anal. Calcd for
C
120H162N4O2: C, 85.15; H, 9.65; N, 3.31. Found: C, 84.88; H,
9.65; N, 3.27.
1,3,5-Tr is[p-(N,N-di-n -octylam in o)ph en yleth yn yl]-2,4,6-
tr is[p-(1,3-d ioxola n -2-yl)p h en yleth yn yl]ben zen e (3o). Re-
action conditions: 12 (800 mg, 0.60 mmol), PdCl2(PPh3)2 (37.9
mg, 0.054 mmol), CuI (20.6 mg, 0.11 mmol), PPh3 (28.3 mg,
0.11 mmol), Et3N (45 mL), and a solution of 2f (941 mg, 5.40
mmol) in Et3N (10 mL) at refluxing temperature for 87 h.
Purification: column chromatography on silica gel eluted with
hexane-CHCl3 (3:7) and then hexane-EtOAc (5:1) followed
by reprecipitation with EtOAc-MeOH and then recycle pre-
parative GPC. Yield 23%; deep orange solid; mp 92 °C; 1H
1,3,5-Tr is[p-(2,2-d icya n oeth en yl)p h en yleth yn yl]-2,4,6-
tr is[p-(N,N-d i-n -octyla m in o)p h en yleth yn yl]ben zen e (3s).
To a solution of 3q (73.6 mg, 0.050 mmol) in CHCl3 (5 mL)
were added benzoic acid (1.8 mg, 0.015 mmol), Et3N (2.1 µL,
0.015 mmol), and malononitrile (10.5 mg, 0.16 mmol). The
resulting mixture was stirred at room temperature for 24 h
and then at 50 °C for 100 h. The mixture was washed with
H2O and brine and dried over Na2SO4. After evaporation of
solvents, the residue was subjected to column chromatography
2496 J . Org. Chem., Vol. 69, No. 7, 2004

Hexakis(p-substituted-phenylethynyl)benzenes
on Al2O3 eluted with hexane-CHCl3 (1.1:0.9) to separate the
fractions containing 3s. The crude 3s was purified by recycle
preparative GPC with CHCl3 as an eluent followed by repre-
cipitation with CHCl3-hexane to give 3s (54.0 mg, 67% yield).
85.6; IR (KBr) ν 3500-3000, 2202, 1607, 1513, 1233 cm-1
.
Anal. Calcd for C54H30O6‚2.5(H2O): C, 79.11; H, 4.30. Found:
C, 79.22; H, 4.05.
Hexa k is(4-ca r b oxyp h en ylet h yn yl)ben zen e (3e). To a
solution of 3d (520 mg, 0.47 mmol) in THF (30 mL) under an
argon atmosphere was added a solution of KOH (1.87 g, 28
mmol) in H2O (30 mL). The resulting mixture was stirred at
70 °C for 46 h. After evaporation of THF, the aqueous residue
was acidified with 2 M HCl. The resulting precipitate was
filtered and washed with H2O and then MeOH. The solid was
triturated with MeOH-CH2Cl2 and filtered to give 3e (396 mg,
90% yield). Yellow brown solid; mp 300 °C dec; 1H NMR
(DMSO-d6) δ 7.62 (d, J ) 7.8 Hz, 12H), 7.26 (d, J ) 7.8 Hz,
12H); 13C NMR (DMSO-d6) δ 166.3, 131.2, 131.0, 129.2, 126.9,
125.8, 98.9, 88.9; IR (KBr) ν 3300-2700, 2205, 1685, 1604,
1280 cm-1. Anal. Calcd for C60H30O12‚1.5(H2O): C, 74.30; H,
3.43. Found: C, 74.21; H, 3.64.
1
Dark red solid; mp 119 °C; H NMR (CDCl3, 10 mM) δ 7.88
(d, J ) 8.5 Hz, 6H), 7.74 (d, J ) 8.5 Hz, 6H), 7.72 (s, 3H), 7.42
(d, J ) 8.8 Hz, 6H), 6.60 (d, J ) 8.8 Hz, 6H), 3.32 (t, J ) 7.3
Hz, 12H), 1.67-1.55 (m, 12H), 1.36-1.27 (m, 60H), 0.91 (t,
J ) 6.9 Hz, 18H); 13C NMR (CDCl3) δ 158.3, 148.7, 133.3,
132.5, 130.6, 130.32, 130.26, 130.2, 123.7, 113.7, 112.7, 111.2,
108.1, 103.5, 97.0, 94.1, 86.2, 82.3, 50.9, 31.8, 29.5, 29.3, 27.3,
27.1, 22.6, 14.1; IR (KBr) ν 2225, 2197, 1604, 1577, 1523, 814
cm-1. Anal. Calcd for C114H139N9: C, 84.24; H, 8.00; N, 7.76.
Found: C, 84.07; H, 8.06; N, 7.50.
1,3-Bis[p-(2,2-d icya n oet h en yl)p h en ylet h yn yl]-2,4,5,6-
t e t r a k is[p -(N ,N -d i-n -oct yla m in o)p h e n yle t h yn yl]b e n -
zen e (3t). Yield 62%; dark red solid; mp 37 °C; 1H NMR
(CDCl3) δ 7.91 (d, J ) 8.5 Hz, 4H), 7.77 (d, J ) 8.5 Hz, 4H),
7.74 (s, 2H), 7.52-7.42 (m, 8H), 6.61 (d, J ) 8.9 Hz, 8H), 3.31
(t, J ) 7.4 Hz, 16H), 1.66-1.56 (m, 16H), 1.36-1.27 (m, 80H),
0.90 (t, J ) 6.9 Hz, 24H); 13C NMR (CDCl3) δ 158.5, 148.63,
148.55, 148.3, 133.3, 133.1, 132.6, 130.7, 130.6, 130.2, 129.3,
126.6, 123.6, 113.8, 112.7, 111.3, 109.1, 108.6, 108.2, 102.6,
102.0, 101.3, 96.5, 94.5, 86.3, 86.1, 85.8, 82.3, 51.0, 31.8, 29.5,
29.3, 27.3, 27.2, 22.6, 14.1; IR (KBr) ν 2225, 2190, 1603, 1577,
1521, 812 cm-1. Anal. Calcd for C126H162N8‚2(H2O): C, 82.94;
H, 9.17; N, 6.14. Found: C, 82.94; H, 9.10; N, 5.79.
1,3,5-Tr is(p-car boxyph en yleth yn yl)-2,4,6-tr is(p-h ydr oxy-
p h en yleth yn yl)ben zen e (3k ). Yield 99%; yellow solid; mp
1
230 °C dec; H NMR (DMSO-d6) δ 10.16 (s, 3H), 8.00 (d, J )
8.3 Hz, 6H), 7.67 (d, J ) 8.3 Hz, 6H), 7.41 (d, J ) 8.5 Hz, 6H),
6.84 (d, J ) 8.5 Hz, 6H); 13C NMR (DMSO-d6) δ 166.6, 158.6,
133.3, 131.3, 130.4, 129.1, 128.2, 126.9, 124.7, 115.5, 112.6,
101.0, 97.4, 90.2, 85.8; IR (KBr) ν 3600-2500, 2208, 1686,
1604, 1512, 1269 cm-1. Anal. Calcd for C57H30O9‚2(H2O): C,
76.50; H, 3.83. Found: C, 76.43; H, 3.95.
Hexa k is(4-h yd r oxyp h en yleth yn yl)ben zen e (3c). To a
solution of 3b (749 mg, 0.51 mmol) in MeOH (15 mL) and THF
(15 mL) at 0 °C under an argon atmosphere was added a 2.2
M aqueous solution of KOH (2.8 mL, 6.2 mmol). After being
stirred at room temperature for 28 h, the reaction mixture was
diluted with H2O (5 mL). After evaporation of organic solvents,
the aqueous residue was acidified with 0.5 M HCl and
extracted with EtOAc. The organic layer was washed with H2O
and brine and dried over Na2SO4. After evaporation of solvent,
the residue was dissolved in a minimum amount of EtOAc and
poured into hexane to give 3c (388 mg, 98% yield). Yellow
Ack n ow led gm en t. We thank Prof. Hisao Murai
(Shizuoka University) for our use of his UV-vis absorp-
tion and fluorescence spectrometers. This work was
supported in part by a Grant-in-Aid from the Ministry
of Education, Science, Sports, Culture, and Technology,
J apan (Nos. 14045233 and 14340217).
Su p p or tin g In for m a tion Ava ila ble: Absorption and
1
fluorescence spectra and their data for 3 and H NMR spectra
of 3-13. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
brown solid; mp 190 °C dec; H NMR (DMSO-d6) δ 10.13 (s,
6H), 7.42 (d, J ) 8.5 Hz, 12H), 6.85 (d, J ) 8.5 Hz, 12H); 13C
NMR (DMSO-d6) δ 158.9, 133.2, 126.0, 116.2, 112.1, 100.0,
J O049948S
J . Org. Chem, Vol. 69, No. 7, 2004 2497