A synthetic strategy leading to monodisperse PPV oligomers by coupling reactions of vinyltrimethylsilanes

Article abstract of DOI:10.1021/jo001795v

A novel strategy for the synthesis of well-defined oligo(phenylenevinylene)s was developed. The procedure is entirely based upon two coupling processes, both involving vinyltrimethylsilanes. Bis(styryl)benzenes 2a-g bearing two octyloxy groups in the central aromatic ring and various substituents on the external aromatic rings were prepared in good yield by a regio- and stereoselective coupling reaction of 1 with different arenediazonium tetrafluoroborates. Oligomers with a more extended conjugated system, 4a-c, and with m-phenylene subunits 13a,b, were also readily obtained by conversion of the unsaturated trimethylsilyl derivatives 3a,c,d to the corresponding boron derivatives and a subsequent coupling reaction with compounds 2a and 2c.

Full text of DOI:10.1021/jo001795v

3878
J . Org. Chem. 2001, 66, 3878-3885
A Syn th etic Str a tegy Lea d in g to Mon od isp er se P P V Oligom er s by
Cou p lin g Rea ction s of Vin yltr im eth ylsila n es
Francesco Babudri, Gianluca M. Farinola, Linda C. Lopez, Maria G. Martinelli, and
Francesco Naso*
Centro CNR di Studio sulle Metodologie Innovative di Sintesi Organiche, Dipartimento di Chimica,
Universita` di Bari, via Amendola 173, 70126 Bari
naso@area.ba.cnr.it
Received December 27, 2000
A novel strategy for the synthesis of well-defined oligo(phenylenevinylene)s was developed. The
procedure is entirely based upon two coupling processes, both involving vinyltrimethylsilanes. Bis-
(styryl)benzenes 2a -g bearing two octyloxy groups in the central aromatic ring and various
substituents on the external aromatic rings were prepared in good yield by a regio- and
stereoselective coupling reaction of 1 with different arenediazonium tetrafluoroborates. Oligomers
with a more extended conjugated system, 4a -c, and with m-phenylene subunits 13a ,b, were also
readily obtained by conversion of the unsaturated trimethylsilyl derivatives 3a ,c,d to the
corresponding boron derivatives and a subsequent coupling reaction with compounds 2a and 2c.
In tr od u ction
vices technology,3d,4,5 and therefore oligomeric models for
these polymers have been studied, mainly in order to
obtain structural information on the solid-state proper-
ties.6 Furthermore, oligophenylenevinylenes, either pure6b,7
or blended with polymers such as polystyrene8 or
PMMA,9 have been successfully used in preparing emis-
sive layers for organic light emitting diodes (OLED).
Nonlinear optical properties10 and amplified stimulated
emission under pulsed optical excitations3d,5c,11 have also
been highlighted in some PPV oligomers.
Organic polymers possessing a long conjugated system
are attracting a widespread interest due to their electrical
and optical properties.1 Despite these special features,
in many cases the structural aspects of these materials
are poorly defined and this uncertainty makes it difficult
to establish firm structure-property relationships. For
this purpose, conjugated monodisperse oligomers play a
key role since a detailed knowledge of their molecular
structure is more easily accessible with respect to their
polymeric counterparts.2 Moreover, conjugated oligomers
may present the same electrical and optical features as
those of the related polydisperse high molecular weight
polymers.3
These important features have stimulated the develop-
(6) (a) Gill, R. E.; Hilberer, A.; van Hutten, P. F.; Berentschol, G.;
Werts, M. P. L.; Meetsma, A.; Wittmann, J . C.; Hadziioannou, G. Synth.
Met. 1997, 84, 637. (b) Van Hutten, P. F.; Krashnikov, V. V.;
Hadziioannou, G. Acc. Chem. Res. 1999, 32, 257. (c)Van Hutten, P. F.;
Wildeman, J .; Meetsma, A.; Hadziioannou, G. J . Am. Chem. Soc. 1999,
121, 5910.
(7) Yang, J . P.; Heremans, P. L.; Hoefnagels, R.; Tachelet, W.;
Dieltiens, P.; Blockuys, F.; Geise, H. J .; Borghs, G. Synth. Met. 2000,
108, 95. Tao, Y.; Donat-Bouillud, A.; D’Iorio, M.; Lam, J .; Gorjanc, T.
C.; Py, C.; Wong, M. S. Synth. Met. 2000, 111-112, 417.
(8) Frederiksen, P.; Bjornholm, T.; Madsen, H. G.; Bechgaard, K.
J . Mater. Chem. 1994, 4, 675. Tachelet, W.; J acobs, S.; Ndayikengu-
rukiye, H.; Geise, H. J .; Gru¨ner, J . Appl. Phys. Lett. 1994, 64, 2364.
(9) Woo, H. S.; Lee, J . G.; Min, H. K.; Oh, E. J .; Park, S. J .; Lee, K.
W.; Lee, J . H.; Cho, S. H.; Kim, T. W.; Park, C.H. Synth. Met. 1995,
71, 2173.
Recent reports have shown that poly(1,4-phenylene-
vinylene) (PPV) and its derivatives are among the most
promising materials in organic electroluminescent de-
(1) Handbook of Conducting Polymers; Skotheim, T. A., Elsen-
baumer, R. L., Reynolds, J . R., Eds.; Marcel Dekker: New York, 1998.
(2) Electronic Materials: The Oligomer Approach; Mu¨llen, K., Weg-
ner, G., Eds.; Wiley-VCH: Weinheim, 1998.
(3) (a) Bubeck, C. In Electronic Materials: The Oligomer Approach;
Mu¨llen, K., Wegner, G., Eds.; Wiley-VCH: Weinheim, 1998; pp 449-
478. (b) Harrison, M. G.; Friend, R. H. In Electronic Materials: The
Oligomer Approach; Mu¨llen, K., Wegner, G., Eds.; Wiley-VCH: Wein-
heim, 1998; pp 515-558. (c) Garnier, F. In Electronic Materials: The
Oligomer Approach; Mu¨llen, K., Wegner, G., Eds.; Wiley-VCH: Wein-
heim, 1998; pp 559-583. (d) Babudri, F.; Cicco, S. R.; Chiavarone, L.;
Farinola, G. M.; Lopez, L. C.; Naso, F.; Scamarcio, G. J . Mater. Chem.
2000, 10, 1573.
(10) (a) Mathy, A.; U¨ berhofen, K.; Schenk, R.; Gregorius, H.; Garay,
R.; Mu¨llen, K.; Bubeck, C. Phys. Rev. B 1996, 53, 4367. (b) Albota, M.;
Beljonne, D.; Ehrlich, J . E.; Fu, J .-Y.; Heikal, A. A.; Hess, S. E.; Kogej,
T.; Levin, M. D.; Marder, S. R.; McCord-Maughon, D.; Perry, J . W.;
Ro¨ckel, H.; Rumi, M.; Subramaniam, G.; Webb, W. W.; Wu, X.-L.; Xu,
C. Science 1998, 281, 1653.
(4) For a general review on synthesis and uses of PPV derivatives,
see: (a) Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew. Chem., Int.
Ed. 1998, 37, 402 and references therein. (b) Moratti, S. C. In
Handbook of Conducting Polymers; Skotheim, T. A., Elsenbaumer, R.
L., Reynolds, J . R., Eds.; Marcel Dekker: New York, 1998; pp 343-
362 and references therein.
(5) For our recent work on PPV systems, see: (a) Babudri, F.; Cicco,
S. R.; Farinola, G. M.; Naso, F.; Bolognesi, A.; Porzio, W. Macromol.
Rapid Commun. 1996, 17, 905. (b) Chiavarone, L.; Farinola, G. M.;
Losacco, A.; Striccoli, M.; Torsi, L.; Scamarcio, G.; Sibilano, M.; Cicco,
S. R.; Babudri, F.; Naso, F. Adv. Sci. Technol. 1999, 27, 271. (c)
Chiavarone, L.; Di Terlizzi, M.; Scamarcio, G.; Farinola, G. M.; Babudri,
F.; Naso, F. Appl. Phys. Lett. 1999, 75, 2053. (d) Naso, F.; Babudri, F.;
Farinola, G. M. Pure Appl. Chem. 1999, 71, 1485. (e) Naso, F. In
Current Trends in Organic Chemistry; Scolastico, C., Nicotra, F., Eds.;
Plenum Publishing Corporation: New York, 1999; pp 259-266.
(11) Brouwer, H.-J .; Krashnikov, T.-A.; Pham, R. E.; Hadziioannou,
G. Appl. Phys. Lett. 1998, 73, 708.
(12) Meier, H. Angew. Chem., Int. Ed. Engl. 1992, 31, 1399.
(13) (a) Drefahl, G.; Ku¨hmsted, R.; Ostwald, H.; Ho¨rhold, H.-H.
Makromol. Chem. 1970, 131, 89. (b) Schenk, R.; Gregorius, H.;
Meerholz, K.; Heinze, J .; Mu¨llen, K. J . Am. Chem. Soc. 1991, 113, 2635.
(c) Gregorius, M.; Baumgarten, M.; Reuter, R.; Tyutyulkov, N.; Mu¨llen,
K. Angew. Chem., Int. Ed. Engl. 1992, 31, 1653. (d) Gill, R. E.;
Meetsma, A.; Hadziioannou, G. Adv. Mater. 1996, 8, 212. (e) Nday-
ikengurukiye, M.; J acobs, S.; Tachelet, W.; Van der Loo, J .; Pollans,
A.; Gense, H. J .; Claeys, M.; Kaufmann, J . M.; J anietz, S. Tetrahedron
1997, 53, 13811. (f) J ung, R.; Schweikart, K. H.; Hanack, M. Synth.
Met. 2000, 111-112, 453. (g) Rumi, M.; Ehrlich, J . E.; Heikal, A. A.;
Perry, J . W.; Barlow, S.; Hu, Z.; McCord-Maughon, D.; Parker, T. C.;
Ro¨ckel, H.; Thayumanavan, S.; Marder, S. R.; Beljonne, D.; Bre´das,
J .-L. J . Am. Chem. Soc. 2000, 122, 9500.
10.1021/jo001795v CCC: $20.00 © 2001 American Chemical Society
Published on Web 04/27/2001

Monodisperse PPV Oligomers
J . Org. Chem., Vol. 66, No. 11, 2001 3879
Sch em e 2
ment of various synthetic methods for PPV oligomers,
mainly based upon the classical procedures used in
organic chemistry to synthesize carbon-carbon double
bonds of stilbene derivatives.12 Thus, Wittig,13 Horner-
Wittig,6c,14 McMurry,15 and Heck6c,16 synthetic strategies,
as well as stepwise approaches requiring different reac-
tion types for each step,17 have been largely employed
for the preparation of PPV oligomers, with various
outcomes with regard to the regio- and stereoselectivity.
Indeed, in some cases, variable amount of cis isomers are
formed,15,17b which can be either converted to an all-trans
isomer by iodine or a thermal isomerization reaction or
separated by chromatography. Moreover, the Heck reac-
tion generates small amounts of regioisomers.16 Stereo-
selective approaches, such as cross-coupling reactions of
unsaturated tin5a,18 and boron19 organometallic reagents,
have mainly been employed, by us and by other workers,
for preparing polydisperse materials rather than well-
defined oligomers. On the contrary, although some regio-
and stereoselective useful coupling reactions of vinyl-
silanes with various compounds have been reported, the
potential use of silicon unsaturated derivatives for the
synthesis of PPV oligomers and polymers so far has
not been exploited. These reactions involve alkenyl-
fluoro compounds,20 alkoxysilanes,21 or alkenylsilacyclo-
butanes22 as starting materials since the simple tri-
methylsilyl unsaturated compounds are considered to be
of poor synthetic interest as reagents for transition metal-
catalyzed cross-coupling reactions.23 To overcome this
drawback, recently we developed a simple strategy by
converting, in a stereoselective way, unsaturated silanes
into boron derivatives, which are then coupled with
organic halides24 or arenediazonium tetrafluoroborates25
in the presence of a Pd catalyst. It is worth noting that
the whole procedure represents a formal Suzuki-
Miyaura type cross-coupling reaction of vinyltrimethyl-
silanes (Scheme 1).
in the field of materials for optical and electronic
devices,3d,5,26 in the present paper we report an unprec-
edented strategy for the stereoselective synthesis of
monodisperse PPV oligomers 4 (Scheme 2), starting with
unsaturated trimethylsilyl derivatives.
Resu lts a n d Discu ssion
Our synthetic approach to PPV oligomers is reported
in the retrosynthetic Scheme 2.
A crucial role in Scheme 2 is represented by the bis-
styryl derivative 2a . In fact, beside contributing with two
double bonds and three phenyl rings to the final struc-
ture, this compound bears two alkoxy substituents which
are needed to increase the solubility of the final product.
The straightforward route leading to derivative 2a is
reported in Scheme 3. The diiodoarene 5 was converted
into the corresponding organomagnesium derivative 6
and cross-coupled with commercially available 1-bromo-
1-(trimethylsilyl)ethene 7 to give R,R′-bis(trimethylsilyl)-
1,4-divinylbenzene 1. This compound was subjected to
reaction with p-bromobenzenediazonium tetrafluoro-
borate 8a by adopting a procedure reported by Kikukawa
and co-workers for the corresponding monosubstituted
system, i.e., R-silylated styrenes.27 As expected from the
work previously reported,27 the reaction was both regio-
and stereoselective. Furthermore, in our case the reaction
appeared to be also chemoselective since only the diazo-
nium functional group was involved in the production of
2a .
Sch em e 1
In connection with our work on the synthesis of
conjugated oligomers and polymers of potential interest
(14) Wang, M. S.; Samoc, M.; Samoc, A.; Luther-Davies, B.; Hum-
phrey, M. G. J . Mater. Chem. 1998, 8, 2005. Yang, J . P.; Heremens, P.
L.; Haefnagels, R.; Tachelet, W.; Dielteens, P.; Blockhuys, F.; Geise,
H. J .; Borghs, G. Synth. Met. 2000, 108, 95.
(15) Rehahn, M.; Schlu¨ter, A. D. Makromol. Chem. Rapid. Commun.
1990, 11, 379.
(16) (a) Heitz, W.; Greiner, A. Makromol. Chem. Rapid Commun.
1988, 9, 581. (b) Heitz, W.; Bru¨gging, W.; Freund, L.; Gailberger, M.;
Greiner, A.; J ung, H.; Kampschulte, U.; Niessner, N.; Osan, F.; et al.
Makromol. Chem. 1988, 189, 119.
(17) (a) Stelmach, U.; Kolshorn, H.; Brehm, I.; Meier, H. Liebigs Ann.
1996, 1449. (b) Maddux, T.; Li, W.; Yu, L. J . Am. Chem. Soc. 1997,
119, 844.
(18) Bao, Z.; Chan, W. K.; Yu, L. J . Am. Chem. Soc. 1995, 117, 12426.
(19) Koch, F.; Heitz, W. Macromol. Chem. Phys. 1997, 198, 1531.
(20) Hiyama, T.; Hatanaka, Y. Pure Appl. Chem. 1994, 66, 1471.
Horn, K. A. Chem. Rev. 1995, 95, 1317.
(21) Tamao, K.; Kobayashi, K.; Ito, Y. Tetrahedron Lett. 1989, 30,
6051.
(22) Denmark, S. E.; Choi, J . Y. J . Am. Chem. Soc. 1999, 121, 5821.
(23) Andreini, B. P.; Carpita, A.; Rossi, R.; Scamuzzi, B. Tetrahedron
1989, 45, 5621.
(24) (a) Farinola, G. M.; Fiandanese, V.; Mazzone, L.; Naso, F. J .
Chem. Soc., Chem. Commun. 1995, 2523. (b) Babudri, F.; Farinola, G.
M.; Fiandanese, V.; Mazzone, L.; Naso, F. Tetrahedron 1998, 54, 1085.
(25) Babudri, F.; Farinola, G. M.; Naso, F.; Panessa, D. J . Org.
Chem. 2000, 65, 1554.
The procedure outlined in Scheme 3 represents a
general methodology for the stereoselective synthesis of
distyryl benzenes with various substituents on the
external aromatic rings. For this reason, along the way
leading to compounds of type 4, it was considered of
interest to investigate further examples of compounds of
type 2 (Scheme 4).
(26) (a) Babudri, F.; Cicciomessere, A. R.; Farinola, G. M.; Fian-
danese, V.; Marchese, G.; Musio, R.; Naso, F.; Sciacovelli, O. J . Org.
Chem., 1997, 62, 3291. (b) Babudri, F.; Cardone, A.; Farinola, G. M.;
Naso, F. Tetrahedron 1998, 54, 14609.
(27) Ikenaga, K.; Matsumoto, S.; Kikukawa, K.; Matsuda, T. Chem.
Lett. 1988, 873.

3880 J . Org. Chem., Vol. 66, No. 11, 2001
Babudri et al.
Sch em e 3
Sch em e 5
Sch em e 6
The results reported in Table 1 show that compounds
2b -f, bearing either electron-donating or electron-
withdrawing groups in the meta or para position were
easily obtained in fair to good yields, according to a
simple experimental protocol (see Experimental Section).
Similar bis(styryl)benzenes with donor-π-donor or ac-
ceptor-donor-acceptor structural motifs have recently
been demonstrated to be important NLO chromophores
exhibiting exceptionally large values of two-photon ab-
sorption cross sections.10b As reported in Scheme 5, we
have also proved that the reaction of 1 with p-nitroben-
zenediazonium tetrafluoroborate 8d is chemoselective,
thus leading to compound 9, which can then react with
the diazonium salt 8e to give the push-pull derivative
2g.
The extension of the conjugated system present in
compound 2a , according to the retrosynthetic Scheme 2,
was carried out by using a coupling reaction with the silyl
derivatives 3a ,c,d (Scheme 6).
corresponding boron counterparts followed by the cross-
coupling reaction with the aromatic dihalide 2a yielded
the oligomers 4a , 4b, and 4c with five or seven aromatic
rings (Scheme 7). The low solubility of the derivative 4b,
in organic solvents, despite the presence of the two alkoxy
chains, prevented its NMR characterization. On the
contrary, the oligomer 4c, with two additional alkyl
chains on the external aromatic rings, showed a higher
The silane homologues 3c and 3d were easily prepared
starting from 3a 24a and the octyl styrene 3b, respectively
(Scheme 6). The latter was obtained, as described in
Scheme 6, by following the procedure previously reported
by us for 3a .24a The homologation process required,
according to our protocol,25 the conversion of the vinyl-
silanes 3a and 3b into the corresponding boron deriva-
tives, by treatment with BCl3 in dichloromethane at 0
°C, followed by a cross-coupling reaction with an arene-
diazonium salt (i.e., p-bromobenzenediazonium tetrafluo-
roborate 8a ). Both steps occurred stereoselectively.
In the final step, conversion of the 2-trimethylsilyl-
styrene24a 3a , or its homologues 3c and 3d , into the
1
solubility, and H and 13C NMR spectra could be recorded
for this compound.
It is worth noting that the transformation of 3a or 3b
into 3c or 3d , respectively (Scheme 6), involved elonga-
tion of the chain with the styryl unit. In principle, the
process could be further iterated. Since in the final cross-
Sch em e 4

Monodisperse PPV Oligomers
J . Org. Chem., Vol. 66, No. 11, 2001 3881
Ta ble 1. Cr oss-Cou p lin g Rea ction s of 1 w ith Ar en ed ia zon iu m Tetr a flu or obor a tes
coupling (Scheme 7) two molecules of unsaturated silane
3 are required for one molecule of dibromo compound 2a ,
each iteration would lead to an increase of two repeating
units in the final chain. However, due to the risk of low
solubility of the final product 4, no efforts were made to
reach n values higher than two.
Finally, the reaction reported in Scheme 8 highlights
an additional feature of our strategy. Indeed, by replacing
2a with 2c in the synthetic Scheme 2 the oligomers 13a
and 13b were obtained. These compounds present the
interesting structural variation of combining the para-
with the meta-bridging substitution pattern on the same
structure. In fact, the meta-bridging provides higher
solubility and, acting as π-conjugation interrupter, has
been demonstrated to induce charge localization both in
Sch em e 7
Sch em e 8

3882 J . Org. Chem., Vol. 66, No. 11, 2001
Babudri et al.
octylbromobenzene (10),34 and 4-bromostilbene (11a )25 were
prepared as reported in the literature. (1-Bromovinyl)tri-
methylsilane (7), (2-bromovinyl)trimethylsilane, and tetrakis-
(triphenylphosphino)palladium(0) were commercial products.
1,4-Bis(octyloxy)-2,5-bis(1-tr im eth ylsilyleth en yl)ben -
zen e (1). In a flame-dried flask was suspended magnesium
(0.450 g, 18.51 mmol) in anhydrous THF (15 mL) in a nitrogen
atmosphere. A solution of 1,4-bis(octyloxy)-2,5diiodobenzene
(5) (3.501 g, 5.97 mmol) in THF (45 mL) was added dropwise
under gentle reflux. After addition completion, the mixture
was further refluxed for 1 h. The resulting solution of the
diorganomagnesium reagent 6 was added dropwise to a
vigorously stirred suspension of (1-bromovinyl)trimethylsilane
(7) (2.670 g, 14.91 mmol) and PdCl2(dppf) (0.270 g, 0.37 mmol)
in THF (20 mL) at 0 °C. The resulting mixture was warmed
to room temperature and stirred for 4 h. After this time the
reaction was quenched with water (100 mL), and the organic
phase was extracted with ethyl acetate (3 × 40 mL) and dried
over anhydrous sodium sulfate. The solvent was removed at
reduced pressure and the residue crystallized from methanol.
A total of 2.21 g (70% yield) of 1 was recovered (mp 69-70
°C). GC/MS (70 eV) m/e 530 (M+, 100), 73 (75), 43 (48). IR
(KBr): ν 1495, 1471, 1394, 1247, 1005, 889, 837 cm-1. 1H NMR
(CDCl3, 500 MHz): δ 0.09 (s, 18H), 0.87 (t, J ) 6.8 Hz, 6H),
1.18-1.44 (m, 20H), 1.71 (quintet, J ) 6.4 Hz, 4H), 3.84 (t, J
) 6.9 Hz, 4H), 5.60 (d, J ) 3.2 Hz, 2H), 5.75 (d, J ) 3.2 Hz,
2H), 6.44 (s, 2H) ppm. 13C NMR (CDCl3, 125 MHz): δ -0.68,
14.09, 22.65, 26.10, 29.25, 29.39, 29.47, 31.61, 69.00, 112.83,
127.18, 133.13, 149.02, 152.52 ppm. Anal. Calcd for C32H58O2-
Si2: C, 72.38; H, 11.01. Found: C, 72.15; H, 10.94.
(E,E)-1,4-Bis(octyloxy)-2,5-bis[2-(4-br om op h en yl)eth e-
n yl]ben zen e (2a). Silane 1 (0.250 g, 0.47 mmol), 4-bromophen-
yldiazonium tetrafluoroborate 8a (0.318 g, 1.17 mmol), and
Pd(dba)2 (0.067 g, 0.12 mmol) were dissolved in dry acetonitrile
(10 mL), at room temperature, under a nitrogen atmosphere.
After 30 min, a yellow-green solid precipitated from the
reaction mixture. This solid was filtered, washed with aceto-
nitrile (10 mL), and purified by flash chromatography (petro-
leum ether/dichloromethane 9/1 as eluent). A yellow solid was
obtained (0.212 g, 65% yield; mp 123-125 °C from methanol).
IR (KBr): ν 1627, 1425, 1205, 1072, 807 cm-1. λmax (CHCl3):
391, 327 nm. 1H NMR (CDCl3, 500 MHz): δ 0.95-1.9 (m, 30H),
4.05 (t, J ) 6.5 Hz, 4H), 7.05 (d, J ) 16.5, Hz, 2H), 7.07 (s,
2H), 7.37 (d, J ) 8.4 Hz, 4H), 7.43 (d, J ) 16.5 Hz, 2H), 7.46
(d, J ) 8.4 Hz, 4H) ppm. 13C NMR (CDCl3, 125 MHz): δ 14.17,
22.75, 26.36, 29.39, 29.48, 29.54, 31.89, 69.62, 110.74, 121.16,
124.28, 126.81, 127.74, 128.03, 131.81, 136.97, 151.20 ppm.
Anal. Calcd for C38H48O2Br2: C, 65.52; H, 6.95. Found: C,
65.36; H, 6.83.
neutral and in ionic (doped) compounds.13c Furthermore,
this special situation of the conjugated system has been
suggested to generate some particular interesting prop-
erties, such as ferromagnetism, on doped oligomers and
polymers with m-phenylene subunits,28 and a blue shift
of the electroluminescence light emission in alkoxy-
substituted poly(p-phenylenevinylene) containing some
meta-linkages.29
Con clu sion s
PPV monodisperse oligomers 4 with up to seven
aromatic rings have been obtained by following a syn-
thetic strategy involving vinyltrimethylsilanes as build-
ing blocks. The aryldesilylation reaction of R,R′-bis-
(trimethylsilyl)-1,4-divinylbenzene 1 with arenediazonium
tetrafluoroborates and the formal Suzuki-Miyaura cross-
coupling process of â-styrylsilanes with aromatic halides
and diazonium salts, following the protocol previously
developed in our laboratories, represent two key reactions
which are both based upon the use of vinylsilanes. Our
methodology compares favorably with other synthetic
approaches to this class of policonjugated compounds for
the simplicity of the experimental procedure, the use of
mild reaction conditions, and the regio- and stereoselec-
tivity of the processes involved. Besides the final products
4, functionalized distyrylbenzenes 2a -f with electron-
donating or electron-withdrawing substituents and push-
pull oligomers such as 2g, which are of potential interest
in the field of materials having NLO properties,10 are
important compounds which become easily accessible by
our procedure. Moreover, besides the oligomers 4a -c
containing only para-linkages, also compounds 13a ,b,
with m-phenylene subunits in the π-chain, are now
readily available through our methodology. Finally, our
procedure, at least in principle, should be suitable for the
preparation of longer chains.
Exp er im en ta l Section
Silica gel 60 (particle size 0.040-0.063) for flash column
chromatography and aluminum sheets with silica gel 60 F254
for TLC were used. GC analyses were performed on a gas
chromatograph equipped with a SE-30 (methylsilicone, 30 m
× 0.25 mm i.d.) capillary column. 1H NMR and 13C NMR
spectra were recorded in CDCl3 at 500 MHz and at 125 MHz,
respectively, using the residual CHCl3 as the standard at 7.24
ppm for 1H spectra and the CDCl3 signal at 77 ppm for 13C
spectra. To obtain reproducible results, it is recommended that
commercial 1 M solutions of BCl3 in methylene chloride be
stored in a freezer under nitrogen over anhydrous Na2CO3.
1,4-Dioxane, tetrahydrofuran, and benzene were distilled from
benzophenone ketyl immediately prior to use. Dichlorometane
was distilled over phosphorus pentoxide and acetonitrile from
4 Å molecular sieves immediately prior to use. All reactions
were performed under a nitrogen atmosphere. Arenediazonium
tetrafluoroborates were prepared from commercial aromatic
amines according to published methods.30 If necessary, the
salts were purified by several recrystallizations from acetone/
diethyl ether and could be stored for several weeks at -4 °C.
Bis(dibenzylideneacetone)palladium(0),31 dichloro[1,1′-bis-
(diphenylphosphino)ferrocene]palladium(II),32 2-trimethysilyl-
styrene (3a ),24a 1,4-bis(octyloxy)-2,5diiodobenzene (5),33 4-n-
(E,E)-1,4-Bis(oct yloxy)-2,5-b is(2-p h en ylet h en yl)b en -
zen e (2b). The compound was prepared starting from 1 (0.237
g, 0.45 mmol), phenyldiazonium tetrafluoroborate 8b (0.224
g, 1.17 mmol), and Pd(dba)2 (0.069 g, 0.12 mmol) in dry
acetonitrile (15 mL) at room temperature (30 min reaction
time). The crude product was purified by flash chromatography
(ethyl acetate/petroleum ether 9/1). A pale yellow solid was
obtained (0.136 g, 56% yield; mp 120-122 °C from methanol).
IR (KBr): ν 1592, 1182, 1057, 962, 759 cm-1. λmax (CHCl3): 391,
322 nm. 1H NMR (CDCl3, 500 MHz): δ 0.90 (t, J ) 6.9 Hz,
6H), 1.24-1.42 (m, 16H), 1.53-1.62 (m, 4H), 1.90 (quintet, J
) 6.5 Hz, 4H), 4.06 (t, J ) 6.5 Hz, 4H), 7.15 (d, J ) 16.4 Hz,
2H), 7.13 (s, 2H), 7.26 (t, J ) 7.5 Hz, 2H), 7.37 (t, J ) 7.5 Hz,
4H), 7.5 (d, J ) 16.4 Hz, 2H), 7.54 (d, J ) 7.5 Hz, 4H) ppm.
13C NMR (CDCl3, 125 MHz): δ 151.05, 137.92, 128.61, 127.33,
126.72, 126.43, 123.44, 110.51, 69.58, 31.82, 29.50, 29.46,
29.29, 26.34, 22.71, 14.15 ppm. Anal. Calcd for C38H50O2: C,
84.71; H, 9.35. Found: C, 84.49; H, 9.17.
(E,E)-1,4-Bis(octyloxy)-2,5-bis[2-(3-br om op h en yl)eth e-
n yl)]ben zen e (2c). The compound was prepared starting from
(28) Fukutome, H.; Takahashi, A.; Ozaki, M. Chem. Phys. Lett. 1987,
133, 34.
(29) Cacialli, F.; Chuah, B. S.; Friend, R. H.; Moratti, S. C.; Holmes,
A. B. Synth. Met. 2000, 111-112, 155.
(32) Hayashi, T.; Konishi, M.; Kobori, Y.; Kumada, M.; Higuchi, T.;
Hirotsu, K. J . Am. Chem. Soc. 1984, 106, 158.
(33) Bao, Z.; Chen, Y.; Cai, R.; Yu, L. Macromolecules 1993, 26, 5281.
(34) Peng, Z.; Gharavi, A. R.; Yu, L. J . Am. Chem. Soc. 1997, 119,
4622.
(30) Roe, A. Org. React. 1949, 5, 193.
(31) Takahashi, Y.; Ito, T.; Sakai, S.; Ishii, Y. J . Chem. Soc., Chem.
Commun. 1970, 1065.

Monodisperse PPV Oligomers
J . Org. Chem., Vol. 66, No. 11, 2001 3883
1 (0.350 g, 0.66 mmol), 3-bromophenyldiazonium tetrafluo-
roborate 8c (0.458 g, 1.69 mmol), and Pd(dba)2 (0.097 g, 0.16
mmol) in dry acetonitrile (12 mL) at room temperature (30
min reaction time). The crude product was purified by flash
chromatography (dichloromethane/petroleum ether 1/8). A
yellow solid was obtained (0.370 g, 80% yield; mp 98-100 °C
from ethanol). IR (KBr): ν 1588, 1474, 1426, 1205, 1156, 966,
880 cm-1. λmax (CHCl3): 391, 328 nm. 1H NMR (CDCl3, 500
MHz): δ 0.86 (t, J ) 6.8 Hz, 6H), 1.19-1.46 (m, 16H), 1.49-
1.59 (m, 4H), 1.86 (quintet, J ) 6.5 Hz, 4H), 4.03 (t, J ) 6.5
Hz, 4H), 7.05 (d, J ) 16.4 Hz, 2H), 7.07 (s, 2H), 7.20 (m, 2H),
7.33-7.37 (m, 2H), 7.41-7.44 (m, 2H), 7.42 (d, J ) 16.4 Hz,
2H), 7.62-7.67 (m, 2H) ppm. 13C NMR (CDCl3, 125 MHz): δ
14.10, 22.67, 26.30, 29.32, 29.42, 29.44, 31.81, 69.48, 110.74,
122.85, 124.92, 125.01, 126.62, 127.44, 129.33, 130.07, 130.15,
140.11, 151.13 ppm. Anal. Calcd for C38H48O2Br2: C, 65.52;
H, 6.95. Found: C, 65.34; H, 6.73.
1,4-Bis(octyloxy)-2-(1-tr im eth ylsilyl-eth en yl)-5-[(1E)-2-
(4-n itr op h en yl)eth en yl]ben zen e (9). The compound was
prepared starting from 1 (0.900 g, 1.70 mmol), 4-nitrophenyl-
diazonium tetrafluoroborate 8d (0.300 g, 1.27 mmol), and Pd-
(dba)2 (0.098 g, 0.17 mmol) in dry acetonitrile (25 mL) at room
temperature (20 min reaction time). The crude product was
purified by flash chromatography (ethyl acetate/petroleum
ether 1/9). A yellow solid was obtained (0.412 g, 56% yield;
mp 112-113 °C from methanol). IR (KBr): ν 1617, 1508, 1407,
1
1261, 1158 cm-1. H NMR (CDCl3, 500 MHz): δ 0.08 (s, 9H),
0.82-0.99 (m, 6H), 1.18-1.59 (m, 20H), 1.76 (quintet, J ) 7.0
Hz, 2H), 1.82 (quintet, J ) 6.5 Hz, 2H), 3.92 (t, J ) 6.8 Hz,
2H), 3.98 (t, J ) 6.5 Hz, 2H), 5.63 (d, J ) 3.1 Hz, 1H), 5.75 (d,
J ) 3.1 Hz, 1H), 6.55 (s, 1H), 6.99 (s, 1H), 7.13 (d, J ) 16.5
Hz, 1H), 7.60 (d, J ) 7.0 Hz, 2H), 7.61 (d, J ) 16.5 Hz, 1H),
8.19 (d, J ) 7.0 Hz, 2H) ppm. 13C NMR (CDCl3, 125 MHz): δ
-0.75, 14.10, 22.66, 26.10, 26.27, 29.26, 29.30, 29.38, 29.45,
29.90, 31.80, 69.03, 69.37, 109.54, 113.92, 123.52, 124.13,
125.50, 126.60, 127.71, 128.68, 137.29, 144.89, 146.37, 149.60,
151.23, 152.31 ppm. Anal. Calcd for C35H53NO4Si: C, 72.49;
H, 9.21; N, 2.42. Found: C, 72.36; H, 9.02; N, 2.18.
(E,E)-1,4-Bis(octyloxy)-2,5-bis[2-(4-n itr oph en yl)eth en yl]-
ben zen e (2d ). The compound was prepared starting from 1
(0.300 g, 0.56 mmol), 4-nitrophenyldiazonium tetrafluoroborate
8d (0.337 g, 1.42 mmol), and Pd(dba)2 (0.082 g, 0.14 mmol) in
dry acetonitrile (20 mL) at room temperature (45 min reaction
time). The crude product was purified by flash chromatography
(ethyl acetate/petroleum ether 9/1). A red solid was obtained
(0.160 g, 45% yield; mp 185-186 °C from ethyl acetate/
petroleum ether). IR (KBr): ν 1625, 1591, 1510, 1426, 1336,
1261, 1215, 1108, 970 cm-1. λmax (CHCl3): 438, 350 nm. 1H
NMR (CDCl3, 500 MHz): δ 0.87 (t, J ) 6.8 Hz, 6H), 1.21-
1.61 (m, 20H), 1.88 (quintet, J ) 6.5 Hz, 4H), 4.07 (t, J ) 6.5
Hz, 4H), 7.12 (s, 2H), 7.20 (d, J ) 16.4 Hz, 2H), 7.61 (d, J )
16.4 Hz, 2H), 7.62 (d, J ) 8.8 Hz, 4H), 8.21 (d, J ) 8.8 Hz,
4H) ppm. 13C NMR (CDCl3, 125 MHz): δ 14.09, 22.66, 26.27,
29.30, 29.37, 31.80, 69.45, 110.79, 124.15, 126.79, 126.82,
127.02, 127.96, 144.34, 146.63, 151.45 ppm. Anal. Calcd for
(E,E)-1,4-Bis(octyloxy)-2-[2-(4-m eth oxyph en yl)eth en yl]-
5-[2-(4-n itr op h en yl)eth en yl]ben zen e (2g). The compound
was prepared starting from 9 (0.100 g, 0.17 mmol), 4-meth-
oxyphenyldiazonium tetrafluoroborate 8e (0.150 g, 0.68 mmol),
and Pd(dba)2 (0.005 g, 0.01 mmol) in dry acetonitrile (15 mL)
at room temperature (20 min reaction time). The crude product
was purified by flash chromatography (ethyl acetate/petroleum
ether 2/8). A red solid was obtained (0.097 g, 93% yield;
mp103-104 °C from ethanol). IR (KBr): ν 1586, 1513, 1377,
1205, 1110, 959 cm-1. λmax (CHCl3): 431, 335 nm. 1H NMR
(CDCl3, 200 MHz): δ 0.78-0.89 (m, 6H), 1.23-1.42 (m, 20H),
1.44-1.58 (m, 2H), 1.82-1.92 (m, 2H), 3.82 (s, 3H), 4.03 (t, J
) 6.5 Hz, 2H), 4.06 (t, J ) 6.5 Hz, 2H), 6.88-6.91 (m, 2H),
7.07 (s, 1H), 7.09 (s, 1H), 7.10 (d, J ) 16.9 Hz, 1H), 7.15 (d, J
) 16.5 Hz, 1H), 7.32 (d, J ) 16.5 Hz, 1H), 7.44-7.47 (m, 2H),
7.59-7.62 (m, 2H), 7.61 (d, J ) 16,9 Hz, 1H), 8.18-8.21 (m,
2H) ppm. 13C NMR (CDCl3, 125 MHz): δ 14.10, 22.67, 26.29,
29.31, 29.40, 29.69, 32.73, 55.32, 69.43, 69.65, 110.21, 111.03,
114.15, 121.11, 124.14, 124.94, 125.97, 126.67, 127.84, 128.84,
129.21, 130.57, 131.51, 144.73, 146.44, 150.83, 151.67, 159.38
ppm. Anal. Calcd for C39H51NO5: C, 76.31; H, 8.37; N, 2.28.
Found: C, 76.54; H, 8.57; N, 2.34.
C
38H48N2O6: C, 72.58; H, 7.69; N, 4.46. Found: C, 72.35; H,
7.39; N, 4.23.
(E,E)-1,4-Bis(oct yloxy)-2,5-b is[2-(4-m et h oxyp h en yl)-
eth en yl]ben zen e (2e). The compound was prepared starting
from 1 (0.430 g, 0.81 mmol), 4-methoxyphenyldiazonium
tetrafluoroborate 8e (0.450 g, 2.03 mmol), and Pd(dba)2 (0.117
g, 0.20 mmol) in dry acetonitrile (15 mL) at room temperature
(15 min reaction time). The crude product was purified by flash
chromatography (ethyl acetate/petroleum ether 2/8). A yellow
solid was obtained (0.320 g, 66% yield; mp 112-113 °C from
methanol). IR (KBr): ν 1604, 1511,1424, 1259, 1176, 1032, 821,
805 cm-1. λmax (CHCl3): 357, 310 nm. 1H NMR (CDCl3, 500
MHz): δ 0.86 (t, J ) 6.8 Hz, 6H), 1.22-1.61 (m, 20H), 1.84
(quintet, J ) 6.5 Hz, 4H), 3.82 (s, 6H), 4.02 (t, J ) 6.5 Hz,
4H), 6.88 (d, J ) 8.7 Hz, 4H), 7.06 (d, J ) 16.4 Hz, 2H), 7.08
(s, 2H), 7.32 (d, J ) 16.4 Hz, 2H), 7.45 (d, J ) 8.7 Hz, 4H)
ppm. 13C NMR (CDCl3, 125 MHz): δ 14.11, 22.68, 26.29, 29.31,
29.42, 29.53, 31.81, 55.29, 69.61, 110.47, 114.07, 121.43,
126.62, 127.67, 128.08, 130.86, 150.93, 159.10 ppm. Anal.
Calcd for C40H54O4: C, 80.22; H, 9.09. Found: C, 79.97; H,
8.98.
(E)-2-(4-n -Octylph en yl)-1-tr im eth ylsilyleth en e (3b). This
product was prepared following the procedure reported for
compound 3a .24a A yellow oil was obtained, which was purified
by distillation in a Kughelroh apparatus (oven temp 150 °C,
10-3 mbar; 80% yield). IR (neat): ν 1608, 986, 868, 836 cm-1
.
1H NMR (CDCl3, 500 MHz): δ 0.18 (s, 9H), 0.91 (t, J ) 7.2
Hz, 3H), 1.22-1.39 (m, 10H), 1.57-1.66 (m, 2H), 2.61 (t, J )
7.6 Hz, 2H), 6.45 (d, J ) 19.1 Hz, 1H), 6.98 (d, J ) 19.1 Hz,
1H), 7.16 (d, J ) 7.9 Hz, 2H), 7.38 (d, J ) 7.9 Hz, 2H) ppm.
Anal. Calcd for C19H32Si: C, 79.09; H, 11.18. Found: C, 78.98;
H, 11.05.
(E)-4-[2-(E)-Tr im eth ylsilyleth en yl]stilben e (3c). A solu-
tion of (E)-2-trimethylsilylvinylmagnesium bromide 12 (11 mL,
0.655 M, 7.20 mmol) in THF was added dropwise to a stirred
solution of (E)-4-bromostilbene 11a (0.900 g, 3.47 mmol) and
NiCl2(dppe) (0.218 g, 0.41 mmol) in anhydrous THF (17 mL)
at 0 °C. The mixture was warmed to room temperature and
stirred for 12 h. After reaction completion (revealed by GC
analysis), water (30 mL) was added to the reaction mixture
and the organic phase was extracted with ethyl acetate (3 ×
20 mL). The combined extracts were dried over anhydrous
sodium sulfate and the solvent was removed at reduced
pressure. The product was purified by flash chromatography
(petroleum ether). A white solid was obtained (0.444 g, 46%
yield; mp 147-150 °C from ethanol). IR (KBr): ν 1626, 1251,
(E,E)-1,4-Bis(octyloxy)-2,5-bis[2-(4-car boeth oxyph en yl)-
eth en yl]ben zen e (2f). The compound was prepared starting
from 1 (0.700 g, 1.32 mmol), 4-carboethoxyphenyldiazonium
tetrafluoroborate 8f (0.871 g, 3.30 mmol), and Pd(dba)2 (0.190
g, 0.33 mmol) in dry acetonitrile (30 mL) at room temperature
(30 min reaction time). The crude product was purified by flash
chromatography (ethyl acetate/petroleum ether 9/1). A yellow
solid was obtained (0.750 g, 83% yield; mp 126-128 °C from
methanol). IR (KBr): ν 1707, 1601, 1275, 1104, 1019, 803, 769
cm-1. λmax (CHCl3): 406, 336 nm. 1H NMR (CDCl3, 500 MHz):
δ 0.86 (t, J ) 6.9 Hz, 6H), 1.20-1.43 (m, 16H), 1.38 (t, J ) 7.1
Hz, 6H), 1.49-1.56 (m, 4H), 1.86 (quintet, J ) 6.4 Hz, 4H),
4.05 (t, J ) 6.5 Hz, 4H), 4.36 (q, J ) 7.1 Hz, 4H), 7.11 (s, 2H),
7.15 (d, J ) 16.4 Hz, 2H), 7.55 (d, J ) 8.7 Hz, 4H), 7.56 (d, J
) 16.4 Hz, 2H), 8.01 (d, J ) 8.7 Hz, 4H) ppm. 13C NMR (CDCl3,
125 MHz): δ 14.09, 14.34, 22.66, 26.28, 29.31, 29.39, 29.44,
31.80, 60.87, 69.51, 110.69, 125.87, 126.24, 126.84, 127.98,
129.03, 129.95, 142.28, 151.27, 166.43 ppm. Anal. Calcd for
1
1242, 992, 969, 831, 797 cm-1. H NMR (CDCl3, 500 MHz): δ
0.15 (s, 9H), 6.48 (d, J ) 19.1 Hz, 1H), 6.85 (d, J ) 19.10 Hz,
1H), 7.07 (d, J ) 16.4 Hz, 1H), 7.11 (d, J ) 16.4 Hz, 1H), 7.21-
7.27 (m, 1H), 7.32-7.37 (m, 2H), 7.41 (d, J ) 8.3 Hz, 2H), 7.47
(d, J ) 8.3 Hz, 2H), 7.48-7.52 (m, 2H) ppm. 13C NMR (CDCl3,
125 MHz): δ -1.23, 126.48, 126.68, 127.61, 128.30, 128.58,
C
44H58O6: C, 77.38; H, 8.56. Found: C, 77.53; H, 8.74.

3884 J . Org. Chem., Vol. 66, No. 11, 2001
Babudri et al.
128.68, 129.55, 136.95, 137.31, 137.67, 143.09 ppm. Anal.
Calcd for C19H22Si: C, 81.95; H, 7.96. Found: C, 81.87; H, 7.79.
(E)-4-Br om o-4′-n -octylstilben e (11b). BCl3 (8.50 mL of a
1 M solution in CH2Cl2, 8.50 mmol) was added dropwise to a
stirred solution of 3b (2.000 g, 6.93 mmol) in anhydrous CH2-
Cl2 (60 mL) at 0 °C under a nitrogen atmosphere. After 30
min, a saturated aqueous solution of Na2CO3 (20 mL) and then
water (10 mL) were added. The organic phase was extracted
with CH2Cl2 (3 × 30 mL) and dried over anhydrous sodium
sulfate, and the solvent was removed under reduced pressure.
The resulting crude boron derivative, 4-bromobenzenediazo-
nium tetrafluoroborate 8a (1.200 g, 4.45 mmol), and palladium
acetate (0.065 g, 0.29 mmol) were dissolved under a nitrogen
atmosphere in dry dioxane (15 mL) at room temperature. The
resulting mixture was stirred for 24 h. After reaction comple-
tion (revealed by GC analysis), water (30 mL) was added to
the reaction mixture and the organic phase was extracted with
ethyl acetate (3 × 30 mL). The combined extracts were dried
over anhydrous sodium sulfate, and the solvent was removed
at reduced pressure. The product was purified by flash
chromatography (petroleum ether). A white solid was obtained
(1.019 g, 62% yield; mp 147-150 °C from ethanol). IR (KBr):
(quintet, J ) 6.4 Hz, 4H), 4.06 (t, J ) 6.4 Hz, 4H), 7.07-7.19
(m, 8H), 7.23-7.28 (m, 2H), 7.33-7.28 (m, 4H), 7.47-7.54 (m,
14H) ppm. 13C NMR (CDCl3, 125 MHz): δ 14.12, 22.69, 26.31,
29.33, 29.44, 29.52, 31.83, 69.57, 110.56, 123.39, 126.48,
126.82, 126.92, 127.57, 128.33, 128,37, 128.67, 136.43, 137.36,
137.39, 151.13 ppm. Anal. Calcd for C54H62O2: C, 87.28; H,
8.41. Found: C, 87.37; H, 8.73.
1,4-Bis(octyloxy)-2,5-bis[(1E)-2-[4-(1E)-2-[4-(1E)-2-p h en -
ylet h en yl]p h en ylet h en yl]p h en ylet h en yl]b en zen e (4b ).
BCl3 (0.67 mL of a 1 M solution in CH2Cl2, 0.67 mmol) was
added dropwise at 0 °C to a stirred solution of (E)-4-[2-(E)-
trimethylsilylethenyl]stilbene 3c (0.156 g, 0.56 mmol) in
anhydrous CH2Cl2 (5 mL). After 30 min a saturated aqueous
solution of Na2CO3 (1.5 mL) was added, followed by water (10
mL). The organic phase was extracted with CH2Cl2 (3 × 10
mL) and dried over anhydrous sodium sulfate, and the solvent
was removed under reduced pressure. The resulting crude
boron derivative, compound 2a (0.056 g, 0.08 mmol), and Pd-
(PPh3)4 (0.023 g, 0.02 mmol) were suspended under a nitrogen
atmosphere in a mixture of toluene (5 mL) and methanol (5
mL), and an aqueous solution of Na2CO3 (2 M, 1.5 mL) was
added dropwise at room temperature. The resulting mixture
was refluxed for 2 h and then water was added. A deep yellow
solid, insoluble in organic solvents, was filtered and purified
by extraction with chloroform in a Soxhlet apparatus (0.063
g, 83% yield; mp 270 °C dec). IR (KBr): ν 1590, 1515, 1201,
964, 821, 803 cm-1 Anal. Calcd for C70H74O2: C, 88.75; H, 7.87.
Found: C, 88.93; H, 7.92.
ν 1510, 1487, 1467, 970, 827 cm-1 1H NMR (CDCl3, 500
.
MHz): δ 0.86 (t, J ) 6.9 Hz, 3H), 1.22-1.38 (m, 10H), 1.56-
1.64 (m, 2H), 2.59 (t, J ) 7.7 Hz, 2H), 6.97 (d, J ) 16.3 Hz,
1H), 7.06 (d, J ) 16.3 Hz, 1H), 7.15 (d, J ) 8.1 Hz, 2H), 7.32-
7.37 (m, 2H), 7.40 (d, J ) 8.1 Hz, 2H), 7.42-7.47 (m, 2H) ppm.
13C NMR (CDCl3, 125 MHz): δ 14.10, 22.66, 29.25, 29.30,
29.47, 31.39, 31.87, 35.74, 121.10, 126.41, 126.47, 127.85,
128.80, 129.39, 131.72, 134.36, 136.49, 143.00 ppm. Anal.
Calcd for C22H27Br: C, 71.15; H, 7.33. Found: C, 71.33; H,
7.55.
(E )-4-[(E )-2-(Tr im e t h ylsilyl)e t h e n yl]-4′-n -oct ylst il-
ben e (3d ). This compound was prepared by following the
procedure reported for 3c, starting from 11b (0.497 g, 1.34
mmol), NiCl2(dppe) (0.050 g, 0.10 mmol) in anhydrous THF
(9 mL), and a THF solution of (E)-2-trimethylsilylvinylmag-
nesium bromide 12 (6 mL, 0.54 M, 3.24 mmol). A white solid
was obtained (0.272 g, 52% yield; mp 87-90 °C from ethanol).
IR (KBr): ν 1598, 1514, 1248, 989, 968, 868, 837 cm-1. 1H NMR
(CDCl3, 500 MHz): δ 0.16 (s, 9H), 0.88 (t, J ) 6.7 Hz, 3H),
1.22-1.38 (m, 10H), 1.48-1.67 (m, 2H), 2.60 (t, J ) 7.7 Hz,
2H), 6.49 (d, J ) 19.1 Hz, 1H), 6.87 (d, J ) 19.1 Hz, 1H), 7.04
(d, J ) 16.3 Hz, 1H), 7.10 (d, J ) 16.3 Hz, 1H), 7.14-7.21 (m,
2H), 7.38-7.48 (m, 6H) ppm. 13C NMR (CDCl3, 125 MHz): δ
-1.20, 14.13, 22.69, 29.29, 29.35, 29.51, 31.44, 31.90, 35.76,
126.43, 126.57, 126.69, 127.35, 128.60, 128.77, 129.33, 134.74,
137.21, 137.46, 142.70, 143.17 ppm. Anal. Calcd for C27H38Si:
C, 83.01; H, 9.80. Found: C, 82.81; H, 9.68.
1,4-Bis(octyloxy)-2,5-bis[(1E)-2-[4-(1E)-2-[4-(1E)-2-(4-n -
oct yl)p h e n yle t h e n yl]p h e n yle t h e n yl]p h e n yle t h e n yl]-
ben zen e (4c). This product was prepared by following the
procedure reported for 4a . The boron derivative was prepared
from 3d (0.082 g, 0.21 mmol), BCl3 (0.27 mL of a 1 M solution
in CH2Cl2, 0.27 mmol), and aqueous Na2CO3 (0.7 mL, 2 M).
The subsequent coupling reaction was performed with 2a
(0.049 g, 0.07 mmol), Pd(PPh3)4 (0.012 g, 0.01 mmol), and
aqueous Na2CO3 (0.7 mL, 2 M) in toluene/methanol (1/1
mixture 10 mL). The crude product was purified by flash
chromatography (petroleum ether/dichloromethane 7/3), fol-
lowed by extraction with chloroform in a Soxhlet apparatus.
A deep yellow solid was obtained (0.049 g, 60% yield; mp 218-
220 °C from dichloromethane/diethyl ether). IR (KBr): ν 1580,
1516, 1194, 966, 827 cm-1. λmax (CHCl3): 432 nm. 1H NMR
(CDCl3, 500 MHz): δ 0.88 (t, J ) 7.1 Hz, 6H), 0.89 (t, J ) 7.0
Hz, 6H), 1.22-1.68 (m, 44H), 1.88 (quintet, J ) 7.0 Hz, 4H),
2.60 (t, J ) 7.6 Hz, 4H), 4.06 (t, J ) 6.3 Hz, 4H), 7.02-7.19
(m, 16H), 7.38-7.55 (m, 22H) ppm. 13C NMR (CDCl3, 125
MHz): δ 14.04, 22.66, 26.38, 29.26, 29.34, 29.48, 29.63, 31.37,
31.90, 35.79, 69.85, 111.04, 123.67, 126.50, 126.60, 126.67,
127.26, 127.47, 128.21, 128.27, 128.56, 128.80, 134.94, 136.69,
137.11, 137.58, 142.77, 151.39 ppm. Anal. Calcd for
C86H106O2: C, 88.15; H, 9.12. Found: C, 88.36; H, 9.27.
1,4-Bis(octyloxy)-2,5-bis[(1E)-2-[4-(1E)-2-ph en yleth en yl]-
p h en yleth en yl]ben zen e (4a ). BCl3 (0.33 mL of a 1 M
solution in CH2Cl2, 0.33 mmol) was added dropwise at 0 °C
under a nitrogen atmosphere to a stirred solution of (E)-1-
trimethylsilyl-2-phenylethene 3a (0.39 g, 0.22 mmol) in an-
hydrous CH2Cl2 (3 mL). After 4 h, a saturated aqueous solution
of Na2CO3 (3 mL) was added, followed by water (10 mL). The
organic phase was extracted with CH2Cl2 (3 × 10 mL) and
dried over anhydrous sodium sulfate, and the solvent was
removed under reduced pressure. The resulting crude boron
derivative, compound 2a (0.071 g, 0.102 mmol), and Pd(PPh3)4
(0.024 g, 0.021 mmol) were suspended under a nitrogen
atmosphere in a mixture of toluene (3.3 mL) and methanol
(3.3 mL), and an aqueous solution of Na2CO3 (2M 1.8 mL) was
added dropwise at room temperature. The resulting mixture
was refluxed for 5 h; then water (50 mL) was added. The
organic phase was extracted with ethyl acetate (3 × 10 mL)
and dried over anhydrous sodium sulfate, and the solvent was
removed under reduced pressure. The residue was purified by
flash chromatography (petroleum ether/dichloromethane 7/3).
A bright yellow solid was obtained (0.050 g, 66% yield; mp
168-170 °C from ethanol). The spectroscopic data are consis-
tent with those reported in the literature.13d
1,4-Bis(octyloxy)-2,5-bis[(1E)-2-[3-(1E)-2-ph en yleth en yl]-
p h en yleth en yl]ben zen e (13a ). The product was prepared
by following the procedure reported for the oligomer 4a , using
the m-bromo derivative 2c instead of 2a . A green-yellow solid
was obtained (0.071 g, 94% yield; mp 149-150 °C from
ethanol). IR (KBr): ν 1631, 1587, 1498, 1474, 1426, 1334, 1205,
966 cm-1. λmax (CHCl3): 391, 349 nm. 1H NMR (CDCl3, 500
MHz): δ 0.79-0.92 (m, 6H), 1.27-1.62 (m, 20H), 1.87 (quintet,
J ) 6.5 Hz, 4H), 4.07 (t, J ) 6.5 Hz, 4H), 7.09-7.20 (m, 8H),
7.24-7.27 (m, 2H), 7.32-7.46 (m, 10H), 7.49-7.54 (m, 6H),
7.62-7.65 (m, 2H) ppm. Anal. Calcd for C54H62O2: C, 87.28;
H, 8.41. Found: C, 87.07; H, 8.33.
1,4-Bis(oct yloxy)-2,5-b is[(E)-2-[4-(1E)-2-[3-(1E)-2-(4-n -
oct yl)p h e n yle t h e n yl]p h e n yle t h e n yl]p h e n yle t h e n yl]-
ben zen e (13b). This product was prepared by following the
procedure reported for 4c, using the m-bromo derivative 2c
instead of 2a . The crude product was purified by flash
chromatography (petroleum ether/dichloromethane 7/3). A
green-yellow solid was obtained (0.048 g, 58% yield; mp 224-
226 °C from dichloromethane/diethyl ether). IR (KBr): ν 1580,
1515, 1205, 966, 823 cm-1. λmax (CHCl3): 364 nm. 1H NMR
IR (KBr): ν 1592, 1511, 1425, 1343, 1203, 963 cm-1. λmax
1
(CHCl3): 419, 391 nm. H NMR (CDCl3, 500 MHz): δ 0.89 (t,
J ) 6.8 Hz, 6H), 1.22-1.47 (m, 16H), 1.52-1.62 (m, 4H), 1.88

Monodisperse PPV Oligomers
J . Org. Chem., Vol. 66, No. 11, 2001 3885
(CDCl3, 500 MHz): δ 0.61-0.92 (m, 12H), 1.20-1.65 (m, 44H),
1.84-1.94 (m, 4H), 2.60 (t, J ) 7.7 Hz, 4H), 4.08 (t, J ) 6.5
Hz, 4H), 7.03-7.19 (m, 16H), 7.32-7.54 (m, 20 H), 7.64 (br s,
2H) ppm. 13C NMR (CDCl3, 125 MHz): δ 13.92, 22.54, 26.27,
29.14, 29.23, 29.37, 29.52, 29.58, 31.25, 31.57, 31.78, 35.67,
69.75, 111.12, 124.02, 124.87, 125.44, 125.58, 126.38, 126.67,
126.79, 127.10, 127.34, 128.41, 128.60, 128.68, 128.77, 128.87,
134.80, 136.50, 137.06, 137.76, 138.44, 142.66, 151.40 ppm.
Anal. Calcd for C86H106O2 C: 88.15; H 9.12. Found: C 88.22;
H 9.17.
Ack n ow led gm en t. This work was financially sup-
ported by the Ministero dell’ Universita` e della Ricerca
Scientifica e Tecnologica, Rome (National Project Ste-
reoselezione in Sintesi Organica. Metodologie ed Appli-
cazioni), by the University of Bari, and by Consiglio
Nazionale delle Ricerche, Rome (National Project Pro-
getto Finalizzato Materiali Speciali per Tecnologie
Avanzate II).
J O001795V