The synthesis of bis(oligophenyleneethynylenes): Novel potential nonlinear optical materials

Article abstract of DOI:10.1016/j.tet.2005.11.015

Various functionalised phenyleneethynylene dimers 10 and trimers 12 were synthesised by palladium-catalyzed Sonogashira methodology. These dimers and trimers were coupled to 1,8-diido-10-methoxyanthracene to generate bis(oligophenyleneethynylenes) 17 and

Full text of DOI:10.1016/j.tet.2005.11.015

Tetrahedron 62 (2006) 1485–1493
The synthesis of bis(oligophenyleneethynylenes):
novel potential nonlinear optical materials
*
David J. Armitt and Geoffrey T. Crisp
School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005, Australia
Received 15 August 2005; revised 27 October 2005; accepted 10 November 2005
Available online 2 December 2005
Abstract—Various functionalised phenyleneethynylene dimers 10 and trimers 12 were synthesised by palladium-catalyzed Sonogashira
methodology. These dimers and trimers were coupled to 1,8-diido-10-methoxyanthracene to generate bis(oligophenyleneethynylenes) 17
and 18. Preliminary results towards the construction of both phenyleneethynylene and phenylenevinylene hybrid motifs are presented.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
Oligo- and poly(phenylenevinylene) molecules (OPVs and
PPVs) are a well-known class of organic NLO materials,
and have some of the highest c(2) and c(3) values recorded.4
However, their alkynyl analogues, oligo(phenyleneethyny-
lene)s (OPEs), have not been as thoroughly assessed for
NLO activity, partly because of their poor solubility. Due to
the absence of E–Z photoisomerization, OPEs offer the
potential advantage of durability over their double bond
counterparts,5 but those previously studied have generally
shown a lower NLO response in comparison,6 which has
usually been ascribed to a less effective electron delocali-
zation along the OPE chain.5
The effects produced by a nonlinear optical (NLO) response
in a bulk material have applications in optical switching,
modulation, amplification, beam steering, wavelength filters
and image processing.1 The most important contributions to
this activity come from the second and third order optical
susceptibilities, c(2) and c(3), and can be described on the
molecular level by the first and second order hyperpolar-
izabilities b and g. In order to achieve large c(2) and c(3)
,
high values of b and g and a high density of nonlinear
optical chromophores is desired, and since the polarization
of a molecule is a vector quantity, the alignment of
molecular dipoles which reinforce each other is also
important.
Since the extent of conjugation is dependant on orbital
overlap, coplanarity of the aryl moieties of the chain is an
important factor for high b and g.7 Arylacetylenes are
known to have a very low barrier (!1 kcal molK1) for
rotation around their sp–sp2 bonds,8 hence OPEs exist in a
conformational equilibrium of planar and various twisted
forms.9 It has been shown that properties such as
fluorescence emission and c(3) can be altered or enhanced
through coplanarity enforced by p-stacking10 and hydro-
phobic/hydrophilic interactions11 in Langmuir films, and by
metal–metal bridging in related systems.12 It is our aim to
explore this theme by restricting the rotation of OPEs by
covalent linking,13 hydrogen bonding or steric bulk.
The design of NLO materials continues to present a
significant challenge to organic chemists.2 It is recognized
that attributes which enhance b include high polarizability,
large anharmonicity and extensive electron delocalization.1
In order to exhibit high c(2), the molecules must also be non-
centrosymmetric, and generally, the organic compounds
which have shown the most promise are donor–acceptor
molecules possessing conjugated spacers with a low
HOMO–LUMO band-gap. However, the structural require-
ments for materials having significant g and c(3) are less
well understood; although a high degree of conjugation is
again desirable, a non-centrosymmetric geometry is
unimportant.3
Earlier we reported the synthesis of the thiacyclophane 1
(Fig. 1) as well as some cyclophane precursors14 and
compared their absorption and emission spectra. However,
the X-ray crystal structure of 1 and subsequent molecular
modelling revealed that a consequence of the length of the
‘arms’ of the cyclophane was to induce some twisting
of the OPE chains and this made the synthesis of
Keywords: Nonlinear optics; Sonogashira coupling; Alkynes.
*
Corresponding author. Tel.: C61 8 8303 5712; fax: C61 8 8303 4358;
e-mail: david.armitt@adelaide.edu.au
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.11.015

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Monomer units containing only one ester side-arm were
utilized for the development of OPE and bis(OPE) synthesis
since the precursors were readily available.
Based on previous reports, route (a) was initially investi-
gated.14 Protodesilylation of 3b with potassium fluoride in
methanol gave the terminal alkyne 4a in quantitative yield;
these conditions proved more efficient than either potassium
carbonate–methanol or TBAF. Coupling of 4a with 522
using piperidine as a base, even when diluted with DMF,
afforded the unexpected product 7, which represents an
example of an unusually facile Pd-catalyzed aryl amination
reaction23 (Scheme 2). It was believed that the formation of
7 was a consequence of the extended conjugation of the
desired intermediate 6. However, further experiments with
different primary and secondary amines revealed that this
reaction was specific for piperidine. The ditriflate 6 was
isolated in 47% yield when the base was changed to
triethylamine.
Figure 1. A previously studied thiacyclophane.
dithiacyclophanes extremely challenging. We wished to
prepare extended analogues of the precursors to thiacyclo-
phane 1 with a view to exploring the effects of hydrogen
bonding and steric bulk in the aryl spacer ‘arms’ on inducing
coplanarity of the arylacetylene spacers. Herein we report
the preparation of two bis(OPEs), after investigating various
approaches for extension of OPE chains.
2. Results and discussion
Disappointingly, the reaction of 5 with the phenolic alkyne
4b24 gave a complex mixture of products, which were not
separable by chromatography, either directly or after
attempted derivatization of the phenolic groups.25
The arylacetylene building blocks 2 (Fig. 2) required to
generate the OPEs have been reported previously, or are
commercially available.15 In general, they were synthesized
by palladium-catalyzed coupling of trimethylsilylacetylene
(TMSA) with the corresponding aryl iodides, followed by
protodesilylation under mild conditions.16 The basic
repeating unit of the OPE chains, the iodide 3a,17 was
obtained in 65% overall yield from methyl o-anthranilate18
by following established procedures for similar monomers19
(Scheme 1). Alternatively, the triflate 3b could be used.20
A longer route for chain extension involving alternating
addition of the alkynyl and aryl moieties was then explored.
Reaction of 6 with an excess of TMSA afforded the disilane
8 in 74% yield; however, deprotection of 8 gave low
yields of the corresponding unstable terminal bis-alkyne
(Scheme 2).
The alternative route (b) to bis(OPE) formation proved to be
more efficient. Sonogashira coupling of the arylacetylenes
2a–2g with 3a afforded the dimers 9a–9g in 58–100% yields
(Scheme 3).26 Removal of the TMS groups was readily
achieved with potassium carbonate–methanol to yield the
terminal alkynes 10a–10g without need for purification.27
The OPE segments could be constructed in one of two ways:
(a) the suitably functionalized monomers could be
sequentially added to the anthracene template, extending
the bis(OPE) one unit at a time; or (b) OPEs could be
synthesized independently, then attached to the anthracene
template. The ester side-arm acts as a handle that allows for
further elaboration to groups, which may restrict the rotation
of the aryl rings through hydrogen bonding or steric bulk, as
well as to increase the solubility of the bis(OPE) products.21
Further coupling of 10a–10e with 3a gave the trimers
11a–11e in good yields (Scheme 4), which again were
Figure 2. Monomeric building blocks for constructing OPEs.
Scheme 1. Conditions: (a) BnMe3NICl2, NaHCO3, 100%; (b) TMSA, Pd(PPh3)2Cl2, CuI, 88%; (c) (i) BF3$OEt2, t-BuONO; (ii) NaI, I2, 74%.

D. J. Armitt, G. T. Crisp / Tetrahedron 62 (2006) 1485–1493
1487
Scheme 2. Conditions: (a) Pd(PPh3)4, CuI, piperidine, DMF, 83% (7); (b) Pd(PPh3)4, CuI, Et3N, DMF, 47% (6); (c) TMSA, Pd(PPh3)4, CuI, 74%.
Scheme 3. Conditions: (a) Pd(PPh3)2Cl2, CuI, 89% (9a); 77% (9b); 99% (9c); 58% (9d); 80% (9e); 92% (9f); 100% (9g); 54% (9h); (b) K2CO3, MeOH, 100%
(10a); 78% (9b); 86% (10c); 95% (10d); 97% (10e); 91% (10f); 93% (10g).
Scheme 4. Conditions: (a) Pd(PPh3)2Cl2, CuI, 74% (11a); 76% (11b); 59% (11c); 63% (11d); 61% (11e); (b) K2CO3, MeOH, 100% (12a); 76% (12b); 95%
(12c); 87% (12d); 87% (12e).
deprotected under mild conditions. In principle, this
iterative method could be employed to generate even longer
OPEs. It was found that this approach to OPE synthesis,
where the chains were elaborated from the functionalized
end group,18,26a was more facile than when the direction of
chain growth was reversed.
The dimer 13 was formed by the coupling of monomeric
units 3a and 4a (Scheme 5), which also generated a
significant amount of trimer 14. The dimer was treated with
potassium carbonate–methanol, but partial hydrolysis of the
triflate was observed along with deprotection of the alkyne.
Dimer 13 and trimer 14 are potentially useful building

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D. J. Armitt, G. T. Crisp / Tetrahedron 62 (2006) 1485–1493
Scheme 5. Conditions: (a) Pd(PPh3)2Cl2, CuI, 32% (13); 18% (14).
Scheme 6. Conditions: (a) 3a, Pd(PPh3)2Cl2, CuI, 54%; (b) KF, MeOH, 76%.
blocks for the rapid construction of soluble long chain
OPEs.
this case, an inseparable 3:1 mixture of regioisomers was
obtained where the major component was the desired
E-stilbene, and the minor component was the corresponding
1,1-disubstituted alkene.
It was believed that the presence of an ester in the ortho-
position may have contributed to the unusually facile
hydrolysis of the triflate.28 This hypothesis was tested by the
synthesis and deprotection of the dimer 9h (Scheme 6),
which lacks the ester in close proximity. Removal of the
TMS group could be performed with potassium fluoride–
methanol without concomitant sulfonate cleavage.
The synthesis of hybrid compounds containing both OPE
and OPV motifs, such as 15 (Fig. 3), would provide an
interesting new class of potential NLO materials. However,
many of the procedures widely used for the preparation of
stilbenes29 require strongly basic conditions, which could
cause unwanted silyl deprotection of the arylalkyne building
blocks. Thus, mild methods for the selective preparation of
E-stilbenes were explored.
Scheme 7. Conditions: (a) Pd(OAc)2, dppp, Et3N, 47% (15a); 29% (15b).
The Suzuki–Miyaura coupling of organic halides and
triflates with boronic acids or esters33 usually requires the
ˆ
presence of a base. Recently Genet et al. have
demonstrated that aryldiazonium salts undergo a rapid
palladium-catalyzed coupling reaction with potassium
alkenyltrifluoroborates under neutral conditions.34 Hence,
the aryldiazonium tetrafluoroborate 3c, an intermediate in
the synthesis of 3a, was treated with potassium E-styryl-
trifluoroborate34b,35 to give the stilbene 16b in 58% yield
(Scheme 8). Attempts to extend this methodology to
synthesize nitro- and methoxy-substituted stilbenes were
unsuccessful, although it was suspected the problems lay
with the conversion of the corresponding styrylboronic
acids into their trifluoroborate salts.
Figure 3. A hypothetical hybrid OPE-OPV structure.
The Heck reaction30 has been utilized for the formation of a
new bond between two sp2-carbon atoms under mild
conditions. The triflate 3b was reacted with methyl acrylate
under the conditions described by Cabri31 to afford the
alkynylcinnamate 16a (Scheme 7); only the E-isomer was
The parent bis(dimer) (17) and bis(trimer) (18) were
generated in 35 and 75% yields, respectively, through the
palladium-catalyzed coupling of 5 with 10a and 12a
(Scheme 9). Dimer 10a reacted at room temperature, but
the reaction of 12a was warmed to 60 8C to increase the
solubility of the intermediate monoalkynylated anthracene
and ensure completion. The preparation of the more
functionalized bis(OPEs), and an examination of their
properties, will be discussed in a separate article.36
1
detected by H NMR. Next, 3b was reacted with styrene
under identical conditions to give a mixture of compounds
from which the E-stilbene 16b was isolated in 29% yield.
Finally, 4-nitrostyrene32 was treated with 3b; however, in

D. J. Armitt, G. T. Crisp / Tetrahedron 62 (2006) 1485–1493
1489
Scheme 8. Conditions: (a) Pd(OAc)2, 58%.
Scheme 9. Conditions: (a) Pd(PPh3)2Cl2, CuI, 35% (17); 75% (18).
3. Conclusions
chromatography of the residue (1:2 CH2Cl2/hexane)
afforded 3a17 (3.20 g, 74% from anthranilate) as a pale
yellow oil (Rf 0.28); C13H15IO2SiNa requires 380.9784, found
(MCNa)C 380.9773; dH (300 MHz, CDCl3) 7.93 (1H, d,
JZ8.2 Hz), 7.88 (1H, d, JZ1.9 Hz), 7.20 (1H, dd,
JZ2.2, 8.2 Hz), 3.93 (3H, s), 0.25 (9H, s); EI-MS m/z 358
(MC%), 343.
In summary, an efficient method for the construction of
trimethylsilylethynyl-terminated OPEs bearing different
functional groups was elucidated, which allows access to
a wide range of potential new NLO materials. Removal of
the silyl protecting groups and subsequent attachment to the
anthracene scaffold 5 generated bis(OPEs) 17 and 18 in
which the OPE strands are held in close proximity, which
could encourage coplanarity of the aryl rings and thereby
increase the effective NLO response of the materials relative
to their parent compounds. Preliminary results aimed at
possibly further fine tuning the NLO properties by the
combination of OPE and OPV elements were also
discussed.
4.1.2. Methyl 5-ethynyl-2-O-(trifluoromethanesulfonyl)-
salicylate 4a. A mixture of 3b (0.79 g, 2.08 mmol),
anhydrous KF (116 mg, 2.00 mmol) and MeOH (20 mL)
was stirred at room temperature for 18 h, then concentrated
under vacuum to afford 4a (0.64 g, 100%) as a colourless
oil;27 dH (200 MHz, CDCl3) 8.19 (1H, d, JZ2.2 Hz), 7.70
(1H, dd, JZ2.4, 8.6 Hz), 7.27 (1H, d, JZ8.6 Hz), 3.97 (3H,
s), 3.21 (1H, s).
4. Experimental
4.1. General
Sonogashira coupling of terminal alkynes to 5. A mixture of
522 (1.0 mmol), alkyne (2.2 mmol) and 1:2 Et3N/DMF
(6 mL) was degassed with a stream of N2. Pd(PPh3)4 or
Pd(PPh3)2Cl2 (0.1 mmol) and CuI (0.1 mmol) were added
and the mixture was stirred at room temperature under N2
for 18 h, then poured into saturated NH4Cl (40 mL). The
resulting suspension was extracted with a suitable solvent
(3!30 mL), and the combined extracts were washed with
water (5!30 mL) and brine (30 mL), dried (Na2SO4),
filtered and concentrated under vacuum.
4.1.1. Methyl 2-iodo-5-(trimethylsilylethynyl)benzoate
3a. BF3$OEt2 (6.15 mL, 48.5 mmol) was cooled to
K20 8C under N2, then a solution of methyl 5-(trimethylsil-
ylethynyl)anthranilate23 (3.00 g, 12.1 mmol) in dry ether
(30 mL) was added dropwise over 5 min. The dropping
funnel was rinsed with dry ether (5 mL), then a solution of
tert-butyl nitrite (5.05 mL, 42.4 mmol) in dry ether (15 mL)
was added dropwise over 0.5 h. The resulting suspension
was stirred at K20 8C for a further 10 min, then allowed to
warm to 0 8C over 20 min. Dry ether (150 mL) was added
and the suspension was kept at 0 8C for 15 min, filtered, and
the solid collected was rinsed with ice-cold dry ether
(20 mL) and briefly air dried. The crude diazonium salt 3c
(3.65 g, 10.5 mmol) was dissolved in dry MeCN (39 mL)
and added dropwise to a solution of NaI (1.90 g, 12.6 mmol)
and I2 (0.27 g, 1.05 mmol) in dry MeCN (80 mL) at room
temperature under N2. The dark solution was stirred at room
temperature for 1 h, 20% Na2S2O3 (90 mL) was added and
the mixture was stirred vigorously for 5 min. The mixture
was extracted with CH2Cl2 (3!120 mL), the combined
extracts were washed with brine (120 mL), dried (Na2SO4),
filtered and concentrated under vacuum. Squat column
4.1.3. 1,8-Bis[4-(trifluoromethanesulfonyloxy)-3-(meth-
oxycarbonyl)phenylethynyl]-10-methoxyanthracene 6.
The general procedure was followed using 5 (1.00 g,
2.18 mmol), 4a (1.48 g, 4.79 mmol), CuI (41 mg,
0.22 mmol) and Pd(PPh3)4 (0.25 g, 0.22 mmol). After
extraction with CH2Cl2, flash chromatography of the residue
(1:4 EtOAc/hexane) afforded 6 (0.84 g, 47%) as a yellow
solid (Rf 0.18), mp 140–145 8C (dec); C37H22F6O11S2Na
requires 843.0405, found (MCNa)C 843.0412; dH
(200 MHz, CDCl3) 9.20 (1H, s), 8.36 (2H, dt, JZ0.9,
8.8 Hz), 8.30 (2H, d, JZ2.2 Hz), 7.89 (2H, dd, JZ0.9,
6.8 Hz), 7.68 (2H, dd, JZ2.2, 8.4 Hz), 7.51 (2H, dd, JZ7.0,
8.8 Hz), 7.13 (2H, d, JZ8.6 Hz), 4.17 (3H, s), 3.95 (6H, s);
dC (50 MHz, CDCl3) 163.5, 153.8, 147.6, 136.7, 136.5,
135.8, 132.0, 131.9, 125.1, 125.0, 124.9, 124.6, 124.4,

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D. J. Armitt, G. T. Crisp / Tetrahedron 62 (2006) 1485–1493
124.2, 123.3, 121.4, 120.7, 119.3, 118.8 (q, JCFZ320.5 Hz),
92.1, 90.8, 63.9, 52.9, nmax 1731, 1643, 1429, 1212, 1186,
1062, 1036, 987 cmK1; EI-MS m/z 820 (MC%), 73; UV lmax
(log 3) 435 (3.91), 411 (3.98), 390 (3.81), 287 (4.49), 268
(4.82) nm; fluorescence lem 455, 481 nm.
extracted with ether (3!50 mL). The extracts were washed
with water (5!50 mL) and brine (50 mL), dried (MgSO4),
filtered and concentrated under vacuum. Flash chromato-
graphy of the residue (3:7 CH2Cl2/hexane) afforded 9a
(0.83 g, 89%) as a yellow oil (Rf 0.28); C21H21O2Si requires
333.1311, found (MCH)C 333.1307; dH (200 MHz,
CDCl3) 8.08 (1H, dd, JZ0.9, 1.3 Hz), 7.55–7.60 (4H, m),
7.34–7.39 (3H, m), 3.96 (3H, s), 0.26 (9H, s); dC (50 MHz,
CDCl3) 165.9, 134.6, 134.1, 133.8, 131.9, 131.8, 128.7,
128.4, 123.6, 123.1, 122.9, 103.6, 97.3, 96.2, 88.0, 52.3,
4.1.4. 1,8-Bis[3-(methoxycarbonyl)-4-(piperidin-1-yl)-
phenylethynyl]-10-methoxyanthracene 7. A mixture of 5
(0.24 g, 0.53 mmol), 4a (0.36 g, 1.17 mmol) and 1:1
piperidine/DMF (4 mL) was degassed with a stream of
N2. Pd(PPh3)4 (62 mg, 0.05 mmol) and CuI (10 mg,
0.05 mmol) were added and the mixture was stirred at
room temperature under N2 for 23 h, then poured into
saturated NH4Cl (20 mL). The mixture was extracted with
CH2Cl2 (3!15 mL), the combined extracts were dried
(Na2SO4), filtered and concentrated under vacuum. Flash
chromatography of the residue (3:7 EtOAc/hexane) afforded
7 (0.30 g, 83%) as a yellow solid (Rf 0.37), mp 142–144 8C;
dH (200 MHz, CDCl3) 9.41 (1H, s), 8.28 (2H, d, JZ8.8 Hz),
8.01 (2H, d, JZ2.0 Hz), 7.76 (2H, d, JZ6.6 Hz), 7.44–7.52
(4H, m), 6.70 (2H, d, JZ8.6 Hz), 4.14 (3H, s), 3.85 (6H, s),
3.00–3.05 (8H, m), 1.59–1.73 (12H, m); dC (75 MHz,
CDCl3) 167.8, 153.1, 152.8, 135.8, 135.1, 131.9, 130.3,
124.9, 124.4, 122.7, 121.9, 119.8, 118.3, 114.5, 94.7, 87.0,
63.5, 53.4, 52.0, 25.9, 24.1; nmax 2201, 1725, 1599, 1497,
1450, 1435, 1246, 1231, 1208, 1129, 1079, 1017, 920, 822,
732 cmK1; EI-MS m/z 690 (MC%), 45.
K0.2; nmax 2157, 1729, 1250, 1185, 1071, 1036, 848 cmK1
;
EI-MS m/z 332 (MC%), 317; UV lmax (log 3) 340 (4.61), 330
(4.62), 306 (4.64), 296 (4.54), 288 (4.50), 267 (4.45), 247
(4.57), 236 (4.63) nm; fluorescence lem 367 nm.
4.1.7. Methyl 5-ethynyl-2-(phenylethynyl)benzoate 10a.
A mixture of 9a (0.26 g, 0.78 mmol), anhydrous K2CO3
(65 mg, 0.47 mmol) and 1:1 MeOH/CH2Cl2 (8 mL) was
stirred at room temperature for 3 h, then diluted with
CH2Cl2 (20 mL), washed with water (15 mL) and brine
(15 mL), dried (Na2SO4), filtered and concentrated under
vacuum to afford 10a (0.21 g, 100%) as a pale yellow oil;27
dH (200 MHz, CDCl3) 8.10 (1H, t, JZ1.1 Hz), 7.55–7.60
(4H, m), 7.37 (3H, m), 3.97 (3H, s), 3.21 (1H, s).
4.1.8. Methyl 5-ethynyl-2-[4-(trifluoromethanesulfony-
loxy)phenylethynyl]benzoate 10h. A mixture of 9h
(0.53 g, 1.10 mmol), anhydrous KF (64 mg, 1.10 mmol)
and MeOH (10 mL) was stirred at room temperature for
18 h, then diluted with CH2Cl2 (25 mL), washed with water
(15 mL) and brine (15 mL), dried (Na2SO4), filtered and
concentrated under vacuum to afford 10h (0.34 g, 76%) as a
yellow oil;27 dH (200 MHz, CDCl3) 8.12 (1H, t, JZ1.1 Hz),
7.65 (2H, m), 7.60 (2H, d, JZ1.1 Hz), 7.28 (2H, m), 3.96
(3H, s), 3.23 (1H, s).
4.1.5. 1,8-Bis[3-(methoxycarbonyl)-4-(trimethylsily-
lethynyl)phenylethynyl]-10-methoxyanthracene 8. A
mixture of 6 (0.44 g, 0.53 mmol), CuI (10 mg, 0.05 mmol)
and 1:2 Et3N/NMP (6 mL) was degassed with a stream of
N2. Pd(PPh3)4 (62 mg, 0.05 mmol) and TMSA (0.30 mL,
2.13 mmol) were added and the mixture was stirred at room
temperature for 19 h. The mixture was poured into saturated
NH4Cl (30 mL) and extracted with CH2Cl2 (3!20 mL).
The combined extracts were washed with water (20 mL)
and brine (20 mL), dried (Na2SO4), filtered and concen-
trated under vacuum. The residue was applied to a short
column of silica, eluted with 1:1 EtOAc/hexane (100 mL)
and the eluant was concentrated under vacuum. Flash
chromatography of the residue (1:4 EtOAc/hexane) afforded
8 (0.28 g, 74%) as a yellow oil (Rf 0.40); C45H40O5Si2Na
requires 739.2312, found (MCNa)C 739.2316; dH
(300 MHz, CDCl3) 9.29 (1H, s), 8.33 (2H, d, JZ8.5 Hz),
8.17 (2H, d, JZ1.6 Hz), 7.83 (2H, dd, JZ0.8, 6.9 Hz), 7.61
(2H, dd, JZ1.6, 8.0 Hz), 7.51 (2H, dd, JZ6.7, 8.8 Hz), 7.45
(2H, d, JZ8.0 Hz), 4.16 (3H, s), 3.89 (6H, s), 0.31 (18H, s);
dC (75 MHz, CDCl3) 165.9, 153.4, 134.5, 134.4, 134.0,
133.3, 132.9, 131.7, 131.6, 124.9, 124.4, 123.6, 122.9,
121.1, 119.4, 103.0, 101.9, 93.7, 90.6, 63.6, 52.1, K0.1;
nmax 2157, 1732, 1677, 1601, 1491, 1437, 1286, 1249, 1079,
845, 760, 739 cmK1; EI-MS m/z 716 (MC%); UV lmax
(log 3) 308 (4.85), 289 (4.88), 231 (5.10) nm; fluorescence
lem 377 nm.
4.1.9. Methyl 2-[3-(methoxycarbonyl)-4-(phenylethynyl)-
phenylethynyl]-5-(trimethylsilylethynyl)benzoate 11a.
The procedure for 9a was followed using 3a (0.34 g,
0.94 mmol), 10a (0.27 g, 1.03 mmol), CuI (9 mg,
0.05 mmol) and Pd(PPh3)2Cl2 (33 mg, 0.05 mmol). After
extraction with CH2Cl2, flash chromatography of the residue
(3:17 EtOAc/hexane) afforded 11a (0.34 g, 74%) as a pale
yellow solid (Rf 0.12, 1:1 CH2Cl2/hexane), mp 118–121 8C;
C31H26O4SiNa requires 513.1498, found (MCNa)C
513.1485; dH (300 MHz, CDCl3) 8.17 (1H, dd, JZ0.6,
1.6 Hz), 8.10 (1H, t, JZ0.8 Hz), 7.66 (1H, d, JZ1.6 Hz),
7.64 (1H, br s), 7.57–7.61 (4H, m), 7.35–7.39 (3H, m), 3.98
(3H, s), 3.97 (3H, s), 0.27 (9H, s); dC (75 MHz, CDCl3)
165.9, 165.7, 134.6, 134.4, 134.1, 134.0, 133.9, 133.8,
132.1, 131.9, 131.8, 128.7, 128.4, 123.8, 123.4, 123.1,
122.9, 103.4, 97.7, 97.3, 96.5, 94.8, 90.6, 88.1, 52.32, 52.28,
K0.2; nmax 1731, 1647, 1503, 1293, 1248, 1189, 1072,
1036, 847 cmK1; EI-MS m/z 490 (MC%), 475; UV lmax
(log 3) 351 (4.78), 249 (4.34) nm; fluorescence lem 388 nm.
4.1.6. Methyl 5-(trimethylsilylethynyl)-2-(phenylethynyl)-
benzoate 9a. A mixture of 3b (1.00 g, 2.79 mmol), 2a
(0.33 mL, 3.07 mmol) and 1:2 Et3N/DMF (12 mL) was
degassed with a stream of N2. CuI (27 mg, 0.14 mmol) and
Pd(PPh3)2Cl2 (98 mg, 0.14 mmol) were added and the
mixture was stirred at room temperature under N2 for 18 h.
The mixture was poured into saturated NH4Cl (50 mL) and
4.1.10. Methyl 5-ethynyl-2-[3-(methoxycarbonyl)-
4-(phenylethynyl)phenylethynyl]benzoate 12a. The pro-
cedure for 10a was followed using 11a (0.41 g, 0.83 mmol)
and anhydrous K2CO3 (0.11 g, 0.83 mmol) to afford 12a
(0.34 g, 100%) as a yellow-orange solid;27 dH (300 MHz,
CDCl3) 8.18 (1H, dd, JZ0.4, 1.5 Hz), 8.13 (1H, t,
JZ1.1 Hz), 7.68 (1H, dd, JZ1.6, 8.0 Hz), 7.65 (1H, d,

D. J. Armitt, G. T. Crisp / Tetrahedron 62 (2006) 1485–1493
1491
JZ0.4 Hz), 7.57–7.61 (4H, m), 7.37 (3H, m), 3.984 (3H, s),
3.981 (3H, s), 3.23 (1H, s).
and Pd(OAc)2 (11 mg, 0.05 mmol) were added and the
mixture was stirred at room temperature under N2 in the
dark for 19 h. The solution was diluted with CH2Cl2
(40 mL), washed with water (5!25 mL) and brine (25 mL),
dried (Na2SO4), filtered and concentrated under vacuum.
Flash chromatography of the residue (2:3 CH2Cl2/hexane)
afforded 15b (0.19 g, 58%) as a colourless oil (Rf 0.22, 1:2
CH2Cl2/hexane); C21H22O2Si requires 334.1389, found
(MC%) 334.1385; dH (200 MHz, CDCl3) 8.04 (1H, dd,
JZ0.5, 1.8 Hz), 7.99 (1H, d, JZ16.3 Hz), 7.68 (1H, d,
JZ8.2 Hz), 7.51–7.59 (3H, m), 7.27–7.41 (3H, m), 7.04
(1H, d, JZ16.3 Hz), 3.93 (3H, s), 0.27 (9H, s); dC (50 MHz,
CDCl3) 167.1, 139.0, 137.2, 135.0, 134.3, 132.3, 128.7,
128.3, 128.1, 126.9, 126.7, 126.5, 122.0, 104.0, 96.0,
52.2, K0.1; nmax 2159, 1722, 1492, 1295, 1248, 1208,
1073, 845 cmK1; EI-MS m/z 334 (MC%), 319; UV lmax
(log 3) 327 (4.15), 269 (4.14), 259 (4.21) nm; fluorescence
lem 398 nm.
4.1.11. Methyl 2-O-trifluoromethanesulfonyl-5-[2-
(methoxycarbonyl)-4-(trimethylsilylethynyl)phenyl-
ethynyl]-salicylate 13, and methyl 2-{4-[4-(trifluoro-
methanesulfonyloxy)-3-(methoxycarbonyl)phenylethy-
nyl]-3-[methoxycarbonyl]phenylethynyl}-5-(trimethyl-
silylethynyl)benzoate 14. The procedure for 9a was
followed using 3a (0.40 g, 1.10 mmol), 4a (0.37 g,
1.21 mmol), CuI (11 mg, 0.06 mmol) and Pd(PPh3)2Cl2
(39 mg, 0.06 mmol). After extraction with CH2Cl2, flash
chromatography of the residue (1:1 CH2Cl2/hexane, then
2:1) afforded 13 (0.36 g, 32%) as a pale yellow oil (Rf 0.54,
2:1 CH2Cl2/hexane); C24H22F3O7SSi requires 539.0808,
found (MCH)C 539.0808; dH (200 MHz, CDCl3) 8.25 (1H,
d, JZ2.2 Hz), 8.10 (1H, t, JZ1.3 Hz), 7.79 (1H, dd, JZ2.2,
8.4 Hz), 7.58 (2H, d, JZ1.1 Hz), 7.30 (1H, d, JZ8.6 Hz),
3.98 (3H, s), 3.96 (3H, s), 0.27 (9H, s); dC (50 MHz, CDCl3)
165.5, 163.5, 147.7, 136.9, 135.8, 134.7, 134.2, 134.0,
4.1.14. 1,8-Bis[3-(methoxycarbonyl)-4-(phenylethynyl)-
phenylethynyl]-10-methoxyanthracene 17. The general
procedure was followed using 5 (0.17 g, 0.37 mmol), 10a
(0.21 g, 0.82 mmol), CuI (7 mg, 0.04 mmol) and Pd(PPh3)2Cl2
(26 mg, 0.04 mmol). After extraction with CH2Cl2, flash
chromatography of the residue (gradient elution 1:9 EtOAc/
hexane to 1:3) afforded 17 (94 mg, 35%) as a yellow solid
(Rf 0.29, 1:4 EtOAc/hexane), mp 95–105 8C (dec);
C51H32O5 requires 724.2250, found (MC%) 724.2246; dH
(200 MHz, CDCl3) 9.37 (1H, br s), 8.35 (2H, dt, JZ1.1,
8.8 Hz), 8.24 (2H, dd, JZ0.5, 1.8 Hz), 7.85 (2H, dd, JZ0.7,
6.8 Hz), 7.49–7.62 (8H, m), 7.42 (2H, dd, JZ0.5, 8.1 Hz),
7.18–7.31 (6H, m), 4.18 (3H, s), 3.93 (6H, s); dC (75 MHz)
165.8, 153.6, 134.3, 134.1, 133.6, 132.1, 132.0, 131.9,
131.2, 128.6, 128.4, 128.3, 125.0, 124.5, 123.6, 123.2,
122.9, 121.3, 119.6, 96.5, 93.9, 90.3, 88.1, 63.7, 52.3; nmax
1723, 1500, 1281, 1184, 1074, 1036, 992 cmK1; EI-MS m/z
724 (MC%), 709, 694, 634, 588; UV lmax (log 3) 438 (4.26),
414 (4.31), 391 (4.19), 331 (4.66), 307 (4.72), 267 (4.87),
247 (4.70) nm; fluorescence lem 457, 484 nm.
132.1, 124.8, 124.2, 123.9, 123.1, 122.4, 118.7 (q, JCF
Z
319.1 Hz), 103.3, 98.1, 92.8, 90.8, 52.8, 52.4, K0.2; EI-MS
m/z 538 (MC%), 523, 405, 375, 332. Further elution afforded
14 (0.14 g, 18%) as a yellow solid (Rf 0.22), mp 129–
132 8C; C34H27F3O9SSiNa requires 719.0995, found (MC
Na)C 719.1000; dH (200 MHz, CDCl3) 8.26 (1H, d, JZ
2.2 Hz), 8.20 (1H, d, JZ1.1 Hz), 8.10 (1H, t, JZ1.1 Hz),
7.80 (1H, dd, JZ2.2, 8.4 Hz), 7.70 (1H, dd, JZ1.6, 8.1 Hz),
7.63 (1H, d, JZ7.9 Hz), 7.58 (2H, d, JZ1.3 Hz), 7.30 (1H,
d, JZ8.4 Hz), 3.99 (3H, s), 3.98 (3H, s), 3.97 (3H, s), 0.26
(9H, s); dC (50 MHz, CDCl3) 165.6, 165.5, 163.5, 147.7,
136.9, 135.8, 134.7, 134.6, 134.2, 134.0, 133.9, 132.3,
131.9, 128.6, 124.8, 124.2, 123.9, 123.6, 123.1, 122.8,
122.6, 125.1 (q, JCFZ322.7 Hz), 103.4, 97.9, 94.5, 93.0,
91.1, 90.9, 52.8, 52.44, 52.37, K0.2; nmax 2157, 1734, 1501,
1291, 1249, 1210, 1140, 1072, 985, 845 cmK1; EI-MS m/z
696 (MC%), 563, 274, 259, 237, 77; UV lmax (log 3) 348
(4.52), 318 (4.32); fluorescence lem 386, 405 nm.
4.1.12. Methyl 2-methoxycarbonyl-4-(trimethylsilylethy-
nyl)cinnamate 15a. To a solution of 3b (0.50 g, 1.31 mmol)
in DMF (3 mL) were added Et3N (0.20 mL, 1.45 mmol),
methyl acrylate (0.24 mL, 2.63 mmol), dppp (15 mg,
0.04 mmol) and Pd(OAc)2 (7 mg, 0.03 mmol), and the
mixture was stirred at 80 8C under N2 for 6.5 h. After
cooling, the mixture was diluted with CH2Cl2 (30 mL),
washed with 5% HCl (2!20 mL), water (3!20 mL) and
brine (20 mL), dried (Na2SO4), filtered and concentrated
under vacuum. Flash chromatography of the residue (7:3
CH2Cl2/hexane) afforded 15a (0.20 g, 47%) as a colourless
4.1.15. 1,8-Bis{3-[methoxycarbonyl]-4-[3-(methoxy-
carbonyl)-4-(phenylethynyl)phenylethynyl]phenylethy-
nyl}-10-methoxyanthracene 18. The general procedure
was followed using 5 (0.17 g, 0.38 mmol), 12a (0.35 g,
0.83 mmol), CuI (7 mg, 0.04 mmol) and Pd(PPh3)2Cl2
(26 mg, 0.04 mmol), except that the reaction was stirred at
60 8C. After extraction with CH2Cl2, flash chromatography
of the residue (9:1 CH2Cl2/hexane then CH2Cl2) afforded 18
(0.30 g, 75%) as a dark yellow solid (Rf 0.18, CH2Cl2), mp
158–165 8C (dec); C71H44O9Na requires 1063.2883, found
(MCNa)C 1063.2866; dH (300 MHz, CDCl3) 9.36 (1H, br
s), 8.36 (2H, dt, JZ1.0, 8.8 Hz), 8.22 (2H, dd, JZ0.3,
1.5 Hz), 8.07 (2H, dd, JZ0.4, 1.8 Hz), 7.83 (2H, dd, JZ1.0,
7.0 Hz), 7.50–7.59 (10H, m), 7.43 (2H, dd, JZ0.4, 8.0 Hz),
7.37 (2H, dd, JZ0.4, 7.8 Hz), 7.22–7.34 (6H, m), 4.18
(3H, s), 3.95 (6H, s), 3.94 (6H, s); dC (75 MHz, CDCl3) 96.5,
95.1, 93.9, 90.63, 90.60, 88.2, 63.7, 52.3, 52.2; nmax 1771,
oil (Rf 0.38); C17H20O4Si requires 316.1131, found (MC%
)
316.1134; dH (300 MHz, CDCl3) 8.41 (1H, d, JZ16.2 Hz),
8.04 (1H, d, JZ1.6 Hz), 7.59 (1H, dd, JZ1.6, 8.2 Hz), 7.54
(1H, d, JZ8.0 Hz), 6.31 (1H, d, JZ15.9 Hz), 3.93 (3H, s),
3.81 (3H, s), 0.26 (9H, s); dC (75 MHz, CDCl3) 166.8,
166.5, 142.9, 136.0, 135.2, 134.3, 129.9, 129.6, 127.8,
121.2, 103.3, 97.5, 52.5, 51.8, K0.2; EI-MS m/z 316 (MC%),
301.
1734, 1505, 1287, 1244, 1184, 1074, 1037, 991 cmK1
;
4.1.13. Methyl 5-(trimethylsilylethynyl)-2-E-(2-pheny-
lethenyl)benzoate 15b. 1,4-Dioxane (4 mL) was degassed
with a stream of N2. Crude 3c (0.35 g, 1.00 mmol),
potassium E-styryltrifluoroborate34a,35 (0.25 g, 1.20 mmol)
ESI-MS m/z 1063 (MCNa)C; UV lmax (log 3) 440 (4.48),
416 (4.57), 396 (4.55), 351 (5.01), 321 (4.85), 266 (4.95),
248 (4.85); fluorescence lem 465, 488.

1492
D. J. Armitt, G. T. Crisp / Tetrahedron 62 (2006) 1485–1493
1991, 95, 10631–10643. (c) Cheng, L.-T.; Tam, W.;
Acknowledgements
Marder, S. R.; Stiegman, A. E.; Rikken, G.; Spangler, C. W.
J. Phys. Chem. 1991, 95, 10643–10652.
We thank M. Crisp for assistance with the synthesis of
trimer 11d, and the Central Science Laboratory, University
of Tasmania, and the School of Chemistry, Monash
University, for mass spectrometric services. We also
gratefully acknowledge the financial support of the
Australian Research Council.
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Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tet.2005.11.
015. General experimental methods and compound charac-
terization data for 9b–g, 10b–g, 11b–e, and 12b–e.
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36. Armitt, D. J.; Crisp, G. T., submitted for publication.