Synthesis and structural analysis of substituted tripod-shaped tri- and tetra(p-phenylene)s

Article abstract of DOI:10.1002/ejoc.201000786

We report here the synthesis of several tripod-shaped oligo(p-phenylene)s with legs composed of three or four phenylene units. Each leg is end-capped with an iodine atom or a TMS or carboxyl group, and an ethoxy group is present on the functional arm. The

Full text of DOI:10.1002/ejoc.201000786

FULL PAPER
DOI: 10.1002/ejoc.201000786
Synthesis and Structural Analysis of Substituted Tripod-Shaped Tri- and
Tetra(p-phenylene)s
Jesús Hierrezuelo,[a] Elena Guillén,[a] J. Manuel López-Romero,*[a] Rodrigo Rico,[a]
M. Rosa López-Ramírez,[b] J. Carlos Otero,[b] and Chengzhi Cai[c]
Keywords: Arenes / Cross-coupling / Nanostructures / Density functional calculations / Raman spectroscopy
We report here the synthesis of several tripod-shaped oligo-
(p-phenylene)s with legs composed of three or four phenyl-
ene units. Each leg is end-capped with an iodine atom or a
TMS or carboxyl group, and an ethoxy group is present on
the functional arm. The tripod containing methyl tri(ethylene
glycol) side chains was designed for biological applications.
The key step in the synthesis is the Pd-catalyzed Suzuki
cross-coupling reaction of the silicon-derived core molecule
with the appropriately substituted p-biphenyl moiety. This
pounds, as iterative coupling of the substituted p-biphenyl
building blocks with the first-generation tripods will allow
the homologation of the tripod legs to obtain giant tripod-
shaped oligo(p-phenylene)s. Also, the iodine end-capped leg
with the ethoxy group on the functional arm permits modular
design of the tripod for further functionalization, which will
define the applications of the tripod-nanostructured surfaces.
The structure of some of the synthesized tripods was studied
through both experimental (Raman spectra) and theoretical
synthesis should be considered a new strategy for these com- (DFT calculation) methods.
(i) “molecular caltrops” with four phenylacetylene legs ex-
Introduction
tending from either a tetrahedral silicon core[6,7] or from an
adamantane core,[8,9] (ii) conically shaped dendron adsorb-
ates with a functional group at the core,[10–13] and (iii) tri-
pod-shaped oligo(p-phenylene)s joined together by a single
silicon atom[14,15] to be used for the functionalization of dif-
ferent surfaces (Figure 1). However, these reported tripod-
shaped molecules cannot be used for biological applica-
tions, because the hydrophobic tripod framework, or in
some cases its alkyl side chains,[14] are known to interact
nonspecifically with protein molecules, thus interfering with
the specific interaction of target molecules with the ligand
on the focal point of the tripod. To overcome the problem,
we must develop modified tripod molecules with appropri-
ate side chains to avoid the interaction with protein mole-
cules.
We have chosen tripodal oligo(p-phenylene)s as the ideal
anisotropic adsorbates for two reasons. Firstly, we have
shown that the p-phenylene legs are sufficiently rigid to
maintain the perpendicular orientation of the functional
arm at the focal point of the tripod with respect to the sur-
face.[16,17] Secondly, the functional arm of these tripods can
be readily functionalized on the surface; for example, the
bromophenyl-terminated arm reacts on the surface with ar-
ylboronic acid derivatives through Suzuki coupling in high
yield (Ͼ90%).[18]
Controlling the orientation and spacing of functional
moieties in organic thin films is of great importance for
both the study of fundamental biomolecular interactions at
interfaces and for biosensor applications. An optimal spac-
ing exists between the functional moieties that are perpen-
dicularly oriented on the film surface for maximizing the
binding strength and density of target molecules. In ad-
dition, the thin films should resist the nonspecific adsorp-
tion of proteins and should ideally be readily functionalized
by using bio-orthogonal reactions, such as click or Suzuki
reactions.[1–3]
The most common method to control the average density
of the functional groups on monolayer surfaces prepared
by self-assembly of monodentate adsorbates is by co-depo-
sition with inert analogous adsorbates. However, it is not
possible to avoid nonrandomized mixing on the nanoscale
that prevents controlling the spacing between the functional
surface groups.[4,5]
To avoid this problem and to control the orientation of
the functional moieties, several large, shape-persistent, and
self-standing molecules have been developed, including:
[a] Dept. de Química Orgánica, Facultad de Ciencias,
Universidad de Málaga,
29071 Málaga, Spain
[b] Dept. de Química Física, Facultad de Ciencias,
Universidad de Málaga,
A tripod with three hepta(p-phenylene) legs was synthe-
sized by coupling of three hexa(p-phenylene) building
blocks to a tetraphenylsilicon core, in accordance with ret-
rosynthetic pathway A (Scheme 1).[14] The limitations of
this approach include the low solubility of the oligo(p-phen-
29071 Málaga, Spain
[c] Dept. of Chemistry & Center for Materials Chemistry,
University of Houston,
Houston, TX 77204-5003, USA
E-mail: jmromero@uma.es
View this journal online at
wileyonlinelibrary.com
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Substituted Tripod-Shaped Tri- and Tetra(p-phenylene)s
Figure 1. Self-standing and shape-persistent molecules for surface nanostructuration.
ylene) moieties, even with side chains, and the difficulty of 1,4-dibromo-2,5-dimethoxybenzene and p-trimethylsilyl-
chemical differentiation between both ends of the oligo(p- phenylboronic acid. The reaction of trimethoxy derivative 4
phenylene) moiety.
with n-butyllithium in THF followed by trimethoxy borate
generated compound 5 in 28% yield (Scheme 2).
The use of a silicon atom as the core for constructing
tripod structures was described by Tour.[6] The coupling of
5 with 6 under standard Suzuki conditions by using
Pd(PPh3)4 as a catalyst produced tripod 1 in good yield
(71%). We recently improved this reaction by using hetero-
geneous Pd/C nanoparticles as the catalyst[26] to obtain 1 in
75% yield. This catalyst avoids the removal of tri-
phenylphosphane oxide from the conventional Pd(PPh3)4
catalyst and allows large-scale synthesis of the compound.
Compound 1 is soluble in most organic solvents.
Following the same pathway, we prepared methylated tri-
pods 2 (Scheme 3). We chose dimethylated p-biphenyl as the
tripod leg as it can be easily brominated on the methyl
groups (see below), allowing further functionalization.
p-Biphenyl 7 was prepared by following the procedure re-
ported by Müllen[27] in a repetitive approach starting from
5-bromo-2-iodo-p-xylene and p-trimethylsilylphenylboronic
acid (62% yield). However, we obtained a better yield
(98%) when compound 7 was synthesized from p-dibro-
moxylene and p-trimethylsilylphenylboronic acid under Su-
zuki monocoupling conditions: Pd(PPh3)4 and CsCO3 in
toluene/methanol. Then, boronic acid 8 was prepared in
quantitative yield under the same conditions as those used
to prepare 5. Acid 8 is also soluble in DME and some other
common organic solvents. The Suzuki reaction of 8 and the
Scheme 1. Retrosynthetic analysis.
In this paper, we report the synthesis of several substi-
tuted tripod shaped p-phenylenes, with each tripod leg com-
posed of three or four phenylene units, by coupling biphenyl
derivatives to a silicon core, following an approach
(Scheme 1, pathway B) that is conceptually different to that
previously mentioned (Scheme 1, pathway A). The key step
for the synthesis of the tripods is the Pd-catalyzed Suzuki
cross-coupling of a triphenylene-silicon core with p-bi-
phenyl building blocks. One of the tripods has oligo(eth-
ylene glycol) (OEG) side chains for resisting any nonspecific
adsorption of proteins.[19–24] Finally, a discussion on the
structure of selected tripods was presented on the basis of
Raman spectra and density functional theory calculations.
Results and Discussion
We first tested the above approach for the preparation triiodide in a refluxing mixture of DME/water gave only
of simple tripod 1 (Scheme 2). Biphenyl 4 was prepared by trisubstituted product 2a, in which hydrolysis of the ethylsil-
following the procedure reported by Lee[25] starting from oxyl group was observed (Scheme 3). When the reaction
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Scheme 2. Reagents and conditions: (i) 1. nBuLi/THF; 2. B(OMe)3/THF; 3. H+. (ii) 6, Pd(PPh3)4/CsCO3/toluene/abs. EtOH.
was carried out in toluene/absolute ethanol, no hydrolysis Pd(dppf)2Cl2 as a catalyst in DME to provide 11 in 55%
was observed, and tripod 2b was obtained in 60% yield. yield (Scheme 4). Coupling of 11 with triiodide 6 gave
The three TMS groups in 2b could be readily replaced with OEG-modified tripod 3a in 43% yield. As above, the TMS
an iodine atom, allowing the end-capping of the tripod legs terminated p-phenylenes could be exchanged with an iodine
with a variety of surface-active groups for chemisorption at atom (compound 3c) that can be used for applying various
different substrate surfaces. Thus, treatment of 2b with ICl functionalities. Again, when the reaction was performed in
(3 equiv.) in CCl4 gave triiodide 2c in 45% yield. Suzuki aprotic solvent, no hydrolysis of the Si–OEt bond in 3b was
coupling of 2c with commercial p-carboxyphenylboronic observed during the Suzuki coupling.
acid gave carboxylic acid terminated tripod 2d in 53% yield.
Finally, more simple compound 12 was prepared by cou-
pling p-methoxycarboxyphenylboronic acid pinacol ester
with 6 in the presence of Ag2CO3 and Pd(PPh3)4 as a cata-
lyst (Scheme 5). This compound was prepared to check the
accuracy of the theoretical results.
Structural Analysis
As described before, we chose tripodal oligo(p-phenyl-
ene)s as the ideal anisotropic adsorbates for silicon surfaces
due to the rigidity of the p-phenylene chain. These com-
pounds have proved to be rigid enough to maintain the per-
pendicular orientation of the functional head with respect
to the surface during the deposition process. To support
this statement we have optimized four different tripodal
structures for obtaining precise information about their
footprint areas and heights once the tripod is anchored to
the surface by the three legs.
Quantum chemical calculations are currently an essential
complementary tool for structural research as is the analysis
of vibrational spectra. The geometries of the four selected
tripods, compounds 2c, 2d, 3c, and 12 (Figure 2) were fully
optimized without imposing any constraints by using the
functional hybrid B3LYP with either 6-31G (compounds 12
and 2d) or LanL2DZ (compounds 2c and 3c) basis sets (see
the Experimental section). In the case of compound 3c, the
OEG side chains were initially directed to be almost in par-
Scheme 3. Reagents and conditions: (i) 1. nBuLi/THF; 2. B(OMe)3/
THF; 3. H+. (ii) 6, Pd(PPh3)4/CsCO3/DME/H2O. (iii) 6, Pd(PPh3)4/
CsCO3/toluene/abs. EtOH. (iv) 2b, ICl/CCl4. (v) 2c, p-carboxy-
phenylboronic acid, Pd(PPh3)4/CsCO3/toluene/abs. EtOH.
The synthesis of tri(ethylene glycol) monomethyl ether allel with the functional arm to enable the legs to bind to
substituted tripod 3 was carried out from 7 (Scheme 4). the surface. This initial configuration remained unchanged
Benzylic bromination of 7 catalyzed with AIBN in the pres- during the optimization process, as can be seen in Figure 2.
ence of NBS in refluxing CCl4 gave tribromo derivative 9 These compounds are representative of tripods having two
in good yield (52%). The coupling of 9 with commercial (i.e., 12), three (i.e., 2c and 3c), and four (i.e., 2d) phenylene
tri(ethylene glycol) monomethyl ether was carried out with units in each leg, covering triangular areas with sides of 18,
Na in dry benzene to obtain 10 in 59% yield. Because we 26, 26, and 33 Å, respectively. This means there is 2 Å for
had observed that the monolithiation of aryl bromides in the silicon central head and an increase of 8 Å per phenyl-
the presence of ethylene glycol substituents fails,[17] we de- ene unit in each leg. The areas covered are ca. 135, 299,
cided to prepare the boronic ester by using a palladium- 286, and 462 Å2, respectively. Concerning the height of the
catalyzed reaction.[28] Thus, bromide 10 was treated with tripods, the silicon atom is 3, 4, 4, and 6 Å above its respec-
bis(pinacolato)diboron in the presence of KOAc and tive base.
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Substituted Tripod-Shaped Tri- and Tetra(p-phenylene)s
Scheme 4. Reagents and conditions: (i) NBS/AIBN/CCl4; (ii) tri(ethylene glycol)monomethyl ether/Na/benzene. (iii) Bis(pinacolato)di-
boron/Pd(dppf)2Cl2/KOAc/DME. (iv) 6, Pd(PPh3)4/CsCO3/DME/H2O. (v) 6, Pd(PPh3)4/CsCO3/toluene/abs. EtOH. (vi) 3a, ICl/CCl4.
2c, and 3c with two, three, and three phenylene rings in each
leg, respectively. Compound 2d was obtained as a syrup in
very small quantities, and therefore, it was not possible to
purify it and obtain its Raman spectrum. However, for the
smallest compounds 12 and 2c, it was possible to calculate
the theoretical Raman spectrum. The respective B3LYP/6-
31G and LanL2DZ calculated spectra are also shown in
Figure 3. The force fields do not show imaginary wave-
numbers, which confirms that the optimized structure of
these compounds corresponds to a minimum. A very good
Scheme 5. Reagents and conditions: (i) Pd(PPh3)4/Ag2CO3/THF.
agreement between the experimental and the theoretical
wavenumbers and intensities is observed, which once again
demonstrates the value of DFT methods for analyzing the
vibrational spectrum of complex molecules for which no
previous vibrational analysis could be made. The strongest
Raman bands correspond to characteristic normal modes
of the oligo(p-phenylene) legs and are assigned as shown in
the calculated spectra of Figure 3 according to the main
internal coordinate contributing to each fundamental.
Raman spectroscopy has repeatedly demonstrated its
value in studying the structure of complex molecules of bio-
logical interest.[29–32] Moreover, Raman intensities of oli-
go(p-phenylene)s have been related to the number of phenyl
rings in the molecule, as well as to its planarity and rigidity,
given that these depend on the conjugation of the system.[16]
Figure 3 shows the experimental Raman spectra of solid 12,
Figure 2. B3LYP-optimized structures of compounds 2c, 2d, 3c, and 12.
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sity ratio decreases as the number of conjugated phenyl
rings increases, therefore indicating greater conjugation in
the system and an increase in the molecular rigidity. The
calculated structures show a dependence on the oligomer
length and the torsional angle between the phenyl rings: a
higher number of aromatic rings would result in a lower
torsional angle[37] and, therefore, more planarity. The opti-
mized structures of compounds 12 and 2c show similar tor-
sional angles of 36 and 47°, respectively. Although a higher
planarity is expected in 2c due to the extra aromatic ring,
the presence of two substituents in the central ring of the
leg explains a higher torsional angle.
Generally speaking, the lack of equivalence between the
phenylene rings complicates the analysis of the Raman in-
tensities and prevents us from drawing conclusions about
the planarity/rigidity of the tripods studied. In spite of this,
the ratio I1280/I1220 is very similar for unsubstituted tri(p-
phenylene) (I1280/I1220 = 5)[35] and for compounds 3c and
2d (I1280/I1220 = 6), indicating that the structure of the tri-
pods and the rigidity of the legs is not significantly affected
by very large substituents.
Figure 3. Experimental and B3LYP calculated Raman spectra of
compounds 2c, 3c, and 12.
Conclusions
We have carried out the synthesis of several tripod-
shaped molecules including one with tri(ethylene glycol)
mono methyl ether side chains on the tripod legs (i.e., 3a–
c) designed for biological applications. The key step in the
synthesis is the Pd-catalyzed Suzuki cross-coupling reaction
of the triiodophenylsilane as the core of the tripod with
substituted biphenyl moieties. Due to the presence of the
iodine atom, the three tripod legs can be end-capped with
a variety of functional groups for surface immobilization,
such as carboxylic acid groups (i.e., 2d) for attachment onto
amino-terminated surfaces. Iterative coupling of the substi-
tuted biphenyl building blocks with first-generation tripods
1–3 will allow the homologation of the tripod legs to give
giant tripod-shaped oligo(p-phenylene)s, which is currently
being undertaken in our laboratories.
The characteristic and very strong Raman bands at ca.
1270 and 1600 cm–1 are assigned to ν(C–C)interring and aro-
matic ν(C–C)ring (mode 8a; νring) stretching fundamentals,
respectively. Other Raman bands recorded at around
1200 cm–1 are also characteristic of these oligomers and are
assigned to the δ(CH) in-plane bending of the CH aromatic
bonds. These bands are always present in the Raman spec-
tra of oligo(p-phenylene)s and can be used as a test for the
quality of the synthetic routes in these samples.[33,34] As dis-
cussed in previous studies,[16] the splitting and broadening
of the band at ca. 1600 cm–1, as observed in the spectrum
of 12 as a shoulder and well pronounced in the cases of
compounds 2c and 3c, are due to the presence of nonequiv-
alent benzene rings in each leg. This behavior is reproduced
by the DFT force fields, which predict two strong bands at
1601 and 1580 cm–1 for compound 12 and three bands at
1601, 1595, and 1580 cm–1 for compound 2c. In the latter,
Experimental Section
these aromatic ν(C–C)
bands are assigned to each one
ring
General: Compounds 4 and 6 were prepared according to literature
procedures.[6,25] Compound 7 was prepared following the procedure
described in the Experimental Section or according to a known
procedure.[27] Melting points were determined with a Gallenkamp
of the three different aromatic rings of the leg. The terminal
ring substituted by iodine shows the lowest wavenumber at
1580 cm–1 and the central ring shows the highest one at
1601 cm–1. As a result of the splitting, the intensity of the instrument. UV spectra were recorded with a Hewlett–Packard
band at 1600 cm–1 is reduced, causing an apparent enhance-
8452A spectrophotometer, and IR spectra were recorded with
ment in the weaker band at 1270 cm–1.
Beckman Aculab IV and Perkin–Elmer 883 spectrophotometers.
Mass spectrometry was done with a Thermo Finnigan instrument
The Raman spectra of a series of penta(p-phenylene) de-
by using the direct injection and electron ionization (EI) modes.
rivatives have previously been studied by our group,[16]
HRMS were recorded with a Micromass (Autospec-Q) spectrome-
where the changes in the intensity ratio between the bands
ter. 1H and 13C NMR spectra were recorded with a 400 MHz ARX
recorded at ca. 1280 and 1220 cm–1 were considered. They
were found to be related to the planarity of these molecules.
It has been demonstrated[35,36] that the Raman intensity ra-
tio I1280/I1220 in oligo(p-phenylene)s is related to the number
400 Bruker spectrometer by using the residual solvent peak in
CDCl3 (δH 7.24 ppm for 1H and δC = 77.0 ppm for 13C) or
CD3SOCD3 (δH = 2.50 ppm for 1H and δC = 39.5 ppm for 13C).
TLC analyses were performed on Merck silica gel 60 F 254 plates,
of phenyl rings in the molecule and its planarity. This inten- and column chromatography was performed on silica gel 60 (0.040–
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Substituted Tripod-Shaped Tri- and Tetra(p-phenylene)s
0.063 mm). Raman spectra were recorded with a Renishaw Invia 505 (29). HRMS (ESI): calcd. for C65H62O10Si 1030.4112; found
micro-Raman spectrometer by using the 514.5 nm exciting line
from an argon ion laser. The microscope was equipped with a 50ϫ
objective (numerical aperture of 0.75). To avoid excessive heating
during measurement of the Raman spectra, the output power of
the laser was 3 mW on the sample surface by using 10% of the
maximum laser power and co-adding 5 scans of 10 s of exposure.
The resolution was set at 4 cm–1 and the geometry of micro-Raman
measurements was 180°. The micro-Raman measurements were
performed by putting the sample in a glass slide. Before each mea-
surement, the instrument was calibrated with a standard Si sample
(520 cm–1).
1030.4107.
Suzuki Coupling Procedure for the Reaction of 5 with 6 under Pd/C
Catalysis: Under an argon atmosphere, a 25-mL round-bottomed
flask was charged with Pd/C[26] (12 mg), boronic acid 5 (0.14 g,
0.49 mmol), K2CO3 (0.11 g, 0.75 mmol), and dimethylacetamide
(DMA)/water (20:1, 8 mL). This mixture was degassed with argon
purge for 5 min, and the reaction was initiated by the addition of
6 (0.10 g, 0.15 mmol) and placed in an oil bath at 70 °C for 12 h.
The catalyst was filtered off and washed with acetonitrile (50 mL).
The combined organic layer was concentrated to dryness under
vacuum to give a crude residue, which was separated by column
chromatography (CH2Cl2/cyclohexanes, 9:1) to obtain 1a as a yel-
lowish foam (117 mg, 75%).
Computational Details: All calculations were carried out with the
GAUSSIAN 03 program package.[38] Density functional theory cal-
culations by using Becke’s three parameter hybrid function com-
bined with the Lee–Yang–Parr correlation function (B3LYP)[39]
was chosen owing to its good performance in predicting molecular
structure as well as force fields.[40]
Tripods 2
(4Ј-Bromo-2Ј,5Ј-dimethyl)biphenyl-4-yltrimethylsilane (7): An oven-
dried round-bottomed flask was fitted with a condenser, placed
under an argon atmosphere, and charged with p-trimethylsilyl
phenylboronic acid (5.00 g, 25.76 mmol), p-dibromoxylene
(34.00 g, 128.79 mmol), Cs2CO3 (16.80 g, 51.52 mmol), and
Pd(PPh3)4 (2.98 g, 2.58 mmol). The flask was evacuated and refilled
with argon (3ϫ) and then toluene/methanol (1:1, 200 mL) was
added. The reaction mixture was heated to reflux for 18 h. When
the reaction was complete, the inorganic solids were removed by
filtration through Celite and washing with several portions of
dichloromethane; then the solvent was evaporated. The residue was
absorbed onto silica, then subjected to column chromatography
Tripod 1
2,5-Dimethoxy-p-(4Ј-methoxyphenyl)phenylboronic Acid (5): Under
an argon atmosphere, n-butyllithium (1.6  in hexanes, 2.9 mL,
4.6 mmol) was added over a solution of 4[25] (1.32 g, 8.40 mmol) in
anhydrous THF (30 mL) at –78 °C. The reaction mixture was
stirred at –78 °C for 1 h. After this period, a solution of trimeth-
ylborate (1.24 mL, 11.07 mmol) in THF (50 mL) was added at
–78 °C. Then, the cold bath was removed, and the mixture was left
to reach room temperature over 12 h. HCl (1 , 15 mL) was added,
and the resulting solution was stirred for 1.5 h. The organic phase
was extracted with CH2Cl2 (3ϫ10 mL) and water (1ϫ10 mL),
dried with MgSO4, filtered, and concentrated under vacuum. The
residue was separated by column chromatography (CH2Cl2) to give
5 as a yellowish solid (283 mg, 28%). M.p. 99–100 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.48 (d, J = 8.4 Hz, 2 H, Ar-H), 7.40 (s, 1
H, Ar-H), 6.95 (d, J = 8.4 Hz, 2 H, Ar-H), 6.86 (s, 1 H, Ar-H),
3.89 (s, 3 H, OCH3), 3.84 (s, 3 H, OCH3), 3.79 (s, 3H, OCH3) ppm.
13C NMR (100 MHz, CDCl3): δ = 158.7 (C), 153.7 (C), 150.7 (C),
131.3 (C), 130.51 (C), 130.50 (2 CH), 116.5 (CH), 113.5 (2 CH),
112.5 (CH), 56.2 (OCH3), 55.7 (OCH3), 55.2 (OCH3) ppm. MS:
m/z (%) = 289 (10), 288 (100) [M]+. HRMS (ESI): calcd. for
C15H17BO5 288.1169; found 288.1164.
(cyclohexane) to give 7 as a solid (8.41 g, 98%). M.p. 67–69 °C
(ref.[27] 67.4–67.8). IR (KBr): ν = 2949, 1247, 823 cm–1. H NMR
1
˜
(400 MHz, CDCl3): δ = 7.55 (d, 2 H, J = 8.0 Hz, Ar-H), 7.43 (s, 1
H, Ar-H), 7.26 (d, 2 H, J = 8.0 Hz, Ar-H), 7.08 (s, 1 H, Ar-H),
2.37 (s, 3 H, CH3), 2.21 (s, 3 H, CH3), 0.29 [s, 9 H, Si(CH3)3] ppm.
13C NMR (100 MHz, CDCl3): δ = 141.2, 141.0, 139.0, 135.0, 134.6,
133.7 (CH), 133.1 (2 CH), 132.0 (CH), 128.3 (2 CH), 123.4, 22.3
(CH3), 19.7 (CH3), –1.1 [Si(CH3)3]. MS: m/z (%) = 333 (42) [M]+,
317 (100), 178 (11).
2,5-Dimethyl-p-(4Ј-trimethylsilylphenyl)phenylboronic Acid (8): Fol-
lowing the procedure outlined for 4,[25] compound 7 (1.65 g,
4.95 mmol) was treated with anhydrous THF (20 mL), nBuLi
(3.40 mL, 5.45 mmol), and neat B(OMe)3 (1.1 mL, 9.9 mmol). Af-
ter acidic treatment with 1  HCl (20 mL), the reaction mixture
was extracted with EtOAc (2ϫ30 mL), dried with anhydrous
Na2SO4, and concentrated in vacuo. The residue was separated by
column chromatography (cyclohexanes/EtOAc, 4:1 to 3:1) to ob-
Ethoxy Tri(2Ј,5Ј,4ЈЈ-trimethoxy[4,1Ј;4Ј,1ЈЈ]terphenyl)silane (1): Un-
der an argon atmosphere, compound 6[6] (0.08 g, 0.11 mmol), 5
(0.10 g, 0.36 mmol), Cs2CO3 (0.02 g, 0.64 mmol), and Pd(PPh3)4
(0.04 g, 0.03 mmol) were dissolved in a degassed (Ar) mixture of
toluene (5 mL) and absolute EtOH (4 mL). The reaction mixture
was stirred for 12 h at room temperature. After this period, the
reaction was filtered through Celite, and the solution was dried
with MgSO4. The solvent was removed in vacuo to give a crude
reaction that was separated by column chromatography (CH2Cl2/
cyclohexanes, 9:1) to obtain 1 as a yellowish foam (80 mg, 71%).
M.p. 68–70 °C. 1H NMR (400 MHz, CDCl3): δ = 7.78 (d, J = 8 Hz,
6 H, Ar-H), 7.63 (d, J = 8 Hz, 6 H, Ar-H), 7.52 (d, J = 8 Hz, 6 H,
tain 8 as a white solid (1.48 g, 100%). M.p. 118–120 °C. IR (KBr):
ν = 1395, 1333, 839, 823 cm–1. H NMR (400 MHz, CDCl ): δ =
1
˜
3
8.12 (s, 1 H, Ar-H), 7.59 (d, J = 8 Hz, 2 H, Ar-H), 7.36 (d, J =
7.6 Hz, 2H, Ar-H), 7.17 (s, 1 H, Ar-H), 2.82 (s, 3H, CH3), 2.34 (s,
3H, CH3), 0.31 [s, 9H, Si(CH3)3] ppm. 13C NMR (100 MHz,
CDCl3): δ = 145.5 (C), 143.5 (C), 142.0 (C), 139.5 (CH), 139.0 (C),
136.0 (C), 133.1 (2 CH), 132.1 (CH), 131.8 (C), 128.3 (2 CH), 22.5
(CH3), 20.1 (CH3), –1.1 [Si(CH3)3] ppm. MS: m/z (%) = 298 (2)
[M]+, 254 (26), 239 (100).
Ar-H), 6.98 (s, 3 H, Ar-H), 6.97 (d, J = 8 Hz, 6 H, Ar-H), 6.96 (s, Tri(2Ј,5Ј-dimethyl-4ЈЈ-trimethylsilyl[4,1Ј;4Ј,1ЈЈ]terphenyl)silanol (2a): A
3 H, Ar-H), 3.97 (q, J = 7 Hz, 2 H, OCH2CH3), 3.84 (s, 9 H, 3 degassed solution of 6 (0.25 g, 0.40 mmol), 8 (0.40 g, 1.32 mmol),
OCH3), 3.79 (s, 9 H, 3 OCH3), 3.78 (s, 9 H, 3 OCH3), 1.31 (t, J = Pd(PPh3)4 (0.04 g, 0.03 mmol), CsCO3 (0.08 g, 2.38 mmol) in H2O
7 Hz, 3 H, OCH2CH3) ppm. 13C NMR (100 MHz, CDCl3): δ = (5 mL), and DME (20 mL) was heated at reflux for 12 h. After this
158.8 (3 C), 150.6 (3 C), 150.5 (3 C), 139.9 (3 C), 135.3 (6 CH), period, the mixture was cooled to room temperature and then fil-
133.0 (3 C), 130.6 (3 C), 130.5 (6 CH), 130.2 (3 C), 129.6 (3 C), tered and extracted with CHCl3 (2ϫ10 mL). The organic phase
128.8 (6 CH), 114.7 (3 CH), 114.5 (3 CH), 113.6 (6 CH), 60.5 was dried with MgSO4, and the solvent was removed in vacuo. The
(OCH2CH3), 56.4 (6 OCH3), 55.3 (3 OCH3), 18.5 (OCH2CH3)
residue was purified by column chromatography (cyclohexanes/
ppm. MS: m/z (%) = 1030 (100) [M]+, 985 (19), 711 (30), 675 (30),
EtOAc, 9:1) to give 2a as a yellowish syrup (92 mg, 24%). 1H NMR
Eur. J. Org. Chem. 2010, 5672–5680
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5677

J. M. López-Romero et al.
FULL PAPER
(400 MHz, CDCl3): δ = 7.80 (d, J = 8.0 Hz, 6 H, Ar-H), 7.58 (d,
J = 8.0 Hz, 6 H, Ar-H), 7.46 (d, J = 8.0 Hz, 6 H, Ar-H), 7.37 (d,
J = 8 Hz, 6 H, Ar-H), 7.19 (s, 3 H, Ar-H), 7.16 (s, 3 H, Ar-H),
2.31 (s, 9 H, 3 CH3), 2.30 (s, 9 H, 3 CH3), 0.30 [s, 27 H, 3 Si-
= 6.8 Hz, 3 H, OCH2CH3) ppm. 13C NMR (100 MHz, CDCl3): δ
= 169.0 (3 C=O), 143.2 (3 C), 143.3 (3 C), 141.1 (3 C), 141.1 (3 C),
139.7 (3 C), 137.3 (6 CH), 135.5 (6 CH), 132.9 (3 C), 132.1 (3 C),
132.0 (3 C), 131.9 (3 CH), 131.6 (3 CH), 131.3 (6 CH), 130.0 (6
(CH3)3] ppm. 13C NMR (100 MHz, CDCl3): δ = 143.4 (3 C), 142.0 CH), 129.0 (3 C), 128.6 (6 CH), 128.5 (6 CH), 21.1 (3 CH3), 20.1
(3 C), 140.9 (3 C), 140.6 (3 C), 138.6 (3 C), 135.2 (6 CH), 133.1 (6
CH), 132.7 (3 C), 132.6 (3 C), 132.1 (3 C), 132.0 (3 CH), 131.9 (3
CH), 128.8 (6 CH), 128.5 (6 CH), 20.0 (3 CH3), 19.9 (3 CH3), –1.0
[3 Si(CH3)3] ppm. MS: m/z (%) = 1035 (Ͻ1) [M]+, 330 (63), 315
(100). HRMS (ESI): calcd. for C69H76OSi4Na 1055.4871; found
1055.4430.
(3 CH3), 59.9 (OCH2CH3), 19.5 (OCH2CH3) ppm. HRMS (ESI):
calcd. for C83H68O7SiNa 1227.4632; found 1227.4651.
Tripods 3
[4Ј-Bromo-2Ј,5Ј-bis(bromomethyl)biphenyl-4-yl]trimethylsilane (9):
Under an argon atmosphere, over
a solution of 7 (4.88 g,
14.65 mmol) and AIBN (100 mg) in carbon tetrachloride (200 mL)
was added NBS (5.22 g, 29.31 mmol). The reaction mixture was
heated at reflux for 12 h. After this period, the mixture was filtered
while hot and then the solvent was removed in vacuo. The solid
residue was purified by column chromatography (cyclohexanes) to
give 9 as a white solid (3.73 g, 52%). M.p. 100–102 °C. IR (KBr):
Ethoxy Tri(2Ј,5Ј-dimethyl-4ЈЈ-trimethylsilyl[4,1Ј;4Ј,1ЈЈ]terphenyl)si-
lane (2b): Following the procedure outlined for 1, compound 6
(0.25 g, 0.4 mmol) was coupled with 8 (0.4 g, 1.32 mmol) in the
presence of Cs2CO3 (0.07 g, 2.20 mmol) and Pd(PPh3)4 (0.04 g,
0.04 mmol) in toluene (15 mL) and absolute EtOH (12 mL). Com-
pound 2b was isolated by column chromatography (cyclohexanes/
EtOAc, 9:1) to give a solid foam (254 mg, 60%). M.p. 139–142. IR
ν = 1248, 1215, 1051, 838, 823 cm–1. 1H NMR (400 MHz, CDCl ):
˜
3
δ = 7.74 (s, 1 H, Ar-H), 7.60 (d, J = 8.4 Hz, 2 H, Ar-H), 7.39 (d,
J = 8 Hz, 2 H, Ar-H), 7.33 (s, 1 H, Ar-H), 4.57 (s, 2 H, CH2), 4.36
(s, 2 H, CH2), 0.30 [s, 9 H, Si(CH3)3] ppm. 13C NMR (100 MHz,
CDCl3): δ = 141.8 (C), 140.4 (C), 138.7 (C), 137.4 (C), 137.1 (C),
135.4 (CH), 133.5 (2 CH), 133.0 (CH), 128.0 (2 CH), 123.4 (C),
32.6 (CH2), 30.3 (CH2), –1.1 [Si(CH3)3] ppm. MS: m/z (%) = 490
(25) [M]+, 411 (26), 317 (8), 257 (100), 178 (59), 73 (27). HRMS
(ESI): calcd. for C17H19Br3Si 487.8806; found 487.8810.
(KBr): ν = 2917, 2849, 1248, 1116, 825 cm–1. 1H NMR (400 MHz,
˜
CDCl3): δ = 7.78 (d, J = 8.0 Hz, 6 H, Ar-H), 7.57 (d, J = 8.0 Hz,
6 H, Ar-H), 7.44 (d, J = 8.0 Hz, 6 H, Ar-H), 7.36 (d, J = 8 Hz, 6
H, Ar-H), 7.19 (s, 3 H, Ar-H), 7.16 (s, 3 H, Ar-H), 3.99 (q, J =
7.0 Hz, 2 H, OCH2CH3), 2.31 (s, 9 H, 3 CH3), 2.29 (s, 9 H, 3 CH3),
1.32 (t, J = 7.0 Hz, 3 H, OCH2CH3), 0.30 [s, 27 H, 3 Si(CH3)3]
ppm. 13C NMR (100 MHz, CDCl3): δ = 143.3 (3 C), 142.0 (3 C),
140.9 (3 C), 140.6 (3 C), 138.6 (6 CH), 135.2 (6 CH), 133.1 (6 CH),
132.7 (3 C), 132.6 (3 C), 131.9 (6 CH), 131.8 (6 C), 128.7, (3 CH),
128.5 (9 CH), 59.9 (OCH2CH3), 20.0 (6 CH3), 18.5 (OCH2CH3),
–1.0 [3 Si(CH3)3] ppm. MS: m/z (%) = 1060 (0) [M]+, 330 (70), 315
(100). HRMS (ESI): calcd. for C71H80OSi4Na 1083.5184; found
1083.5184.
{4Ј-Bromo-2Ј,5Ј-bis[(2-methoxyethoxy)methyl]biphenyl-4-yl}tri-
methylsilane (10): Under an argon atmosphere, over tri(ethylene
glycol)monomethyl ether (38.60 mL, 241.24 mmol) at 0 °C was
added Na (0.63 g, 27.38 mmol) in small portions. The reaction mix-
ture was stirred for 30 min at 0 °C and then was left to reach room
temperature till complete Na dissolution. Then, a solution of 9
(3.63 g, 7.40 mmol) in dry benzene (50 mL) was added by cannula.
The reaction mixture was stirred and heated at 70 °C for 3 h. After
this period, the mixture was cooled and Et2O (100 mL) was added.
The ethereal solution was washed with H2O (3ϫ20 mL), dried with
CaCl2, and concentrated to dryness. Compound 10 was isolated by
column chromatography (cyclohexane/EtOAc, 6:4) as a yellowish
Ethoxy Tri(2Ј,5Ј-dimethyl-4ЈЈ-iodo[4,1Ј;4Ј,1ЈЈ]terphenyl)silane (2c):
ICl (1  in CH2Cl2, 0.16 mL, 0.16 mmol) was added dropwise to a
solution of 2b (0.14 g, 0.13 mmol) in dry CCl4 (3 mL) at 0 °C under
an argon atmosphere. The reaction mixture was warmed to room
temperature and stirred for 1 h. A solution of sodium disulfide was
added, and the layers were separated. The aqueous layer was ex-
tracted with CH2Cl2, and the combined organic phase was washed
with water. The organic phase was dried with MgSO4, and then
the solvent was removed in vacuo. Compound 2c was isolated by
column chromatography (cyclohexanes/EtOAc, 9:1) as a solid foam
syrup (2.85 g, 59%). IR (KBr): ν = 3325, 2874, 1248, 1097, 1046,
˜
1
840, 827 cm–1. H NMR (400 MHz, CDCl3): δ = 7.71 (s, 1 H, Ar-
H), 7.52 (d, J = 7.8 Hz, 2 H, Ar-H), 7.36 (s, 1 H, Ar-H), 7.28 (d,
J = 7.8 Hz, 2 H, Ar-H), 4.60 (s, 2 H, PhCH2), 4.38 (s, 2 H, PhCH2),
3.67–3.46 (m, 24 H, 12 CH2O), 3.32 (s, 3 H, OCH3), 3.31 (s, 3 H,
OCH3), 0.27 [s, 9 H, Si(CH3)3] ppm. 13C NMR (100 MHz, CDCl3):
δ = 140.5 (C), 139.9 (C), 139.3 (C), 136.6 (C), 133.0 (C), 132.5 (2
CH), 130.2 (CH), 128.2 (CH), 121.4 (2 CH), 72.1 (CH2O), 71.8
(CH2O), 70.5 (4 CH2O), 70.44 (2 CH2O), 70.36 (4 CH2), 70.0
(CH2O), 69.6 (CH2O), 58.8 (2 OCH3), –1.2 [Si(CH3)3] ppm. MS:
m/z (%) = 656 (Ͻ1) [M]+, 166 (67), 161 (30), 117 (76), 103 (31), 83
(42), 82 (100), 73 (77), 67 (71). HRMS (ESI): calcd. for C31H49BrO-
8SiNa 679.2278; found 679.2276.
1
(71 mg, 45%). H NMR (400 MHz, CDCl3): δ = 7.81–7.73 (m, 12
H, Ar-H), 7.46–7.41 (m, 6 H, Ar-H), 7.19–7.10 (m, 12 H, Ar-H),
4.00 (q, J = 6.8 Hz, 2 H, OCH2CH3), 2.32 (s, 9 H, 3 CH3), 2.26 (s,
9 H, 3 CH3), 1.33 (t, J = 6.8 Hz, 3 H, OCH2CH3) ppm. 13C NMR
(100 MHz, CDCl3): δ = 143.1 (3 C), 141.1 (3 C), 141.0 (3 C), 139.7
(3 C), 137.2 (6 CH), 135.2 (6 CH), 132.8 (3 C), 132.5 (3 C), 132.4
(3 C), 131.9 (3 CH), 131.6 (3 CH), 131.2 (6 CH), 128.7 (6 CH),
92.5 (3 CI), 20.0 (3 CH3), 19.8 (3 CH3), 59.9 (OCH2CH3), 18.5
(OCH2CH3) ppm. HRMS (ESI): calcd. for C62H53I3OSiNa
1245.0897; found 1245.0899.
{2Ј,5Ј-Bis[(2-methoxyethoxy)methyl]-4Ј-(4,4,5,5-tetramethyl-1,3,2-di-
Ethoxy Tri(2Ј,5Ј-dimethyl-4ЈЈЈ-carboxy[4,1Ј;4Ј,1ЈЈ;4ЈЈ,1ЈЈЈ]tetraphen- oxaborolan-2-yl)biphenyl-4-yl}trimethylsilane (11): Under an argon
yl)silane (2d): Following the procedure outlined for 1, compound
2c (0.05 g, 0.04 mmol) was coupled with p-carboxyphenylboronic
acid (0.04 g, 0.14 mmol) in the presence of Cs2CO3 (8.0 mg,
0.2 mmol) and Pd(PPh3)4 (14 mg, 0.0123 mmol) in toluene (3 mL)
and absolute EtOH (2 mL). Compound 2d was isolated by column
atmosphere, a degassed solution of 10 (1.14 g, 1.73 mmol), bis(pi-
nacolato)diboron (0.53 mg, 2.08 mmol), Pd(dppf)2Cl2 (0.30 g,
0.35 mmol), and KOAc (0.51 g, 5.19 mmol) in dry DME (20 mL)
was heated at reflux for 12 h. After this period, the reaction was
cooled to room temperature, filtered, and diluted with CH2Cl2
chromatography (cyclohexanes/EtOAc, 9:1) to give a yellowish (15 mL). The organic solution was washed with H2O (2ϫ10 mL)
1
syrup (26 mg, 53%). H NMR (400 MHz, CDCl3): δ = 8.00 (d, J
and brine, then dried with MgSO4, and concentrated to dryness.
= 7.9 Hz, 6 H, Ar-H), 7.89–7.70 (m, 18 H, Ar-H), 7.50–7.40 (m, 6 The residue was separated by column chromatography (EtOAc/cy-
H, Ar-H), 7.21–7.10 (m, 12 H, Ar-H), 3.98 (q, J = 6.8 Hz, 2 H, clohexanes, 8:2) to give compound 11 as a yellowish syrup (675 mg,
OCH2CH3), 2.34 (s, 9 H, 3 CH3), 2.29 (s, 9 H, 3 CH3), 1.30 (t, J 55%). IR (KBr): ν = 2870, 1337, 1142, 1098, 1068, 839 cm–1. 1H
˜
5678
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 5672–5680

Substituted Tripod-Shaped Tri- and Tetra(p-phenylene)s
NMR (400 MHz, CDCl3): δ = 7.91 (s, 1 H, Ar-H), 7.53 (d, J =
8.0 Hz, 2 H, Ar-H), 7.40 (s, 1 H, Ar-H), 7.39 (d, J = 8.0 Hz, 2 H,
Ar-H), 4.81 (s, 2 H, PhCH2), 4.40 (s, 2 H, PhCH2), 3.65–3.46 (m,
J = 8.4 Hz, 6 H, Ar-H), 7.48 (d, J = 8.2 Hz, 6 H, Ar-H), 7.47 (s, 3
H, Ar-H), 7.24 (s, 3 H, Ar-H), 7.21 (d, J = 8.2 Hz, 6 H, Ar-H),
4.50 (s, 6 H, 3 PhCH2), 4.47 (s, 6 H, 3 PhCH2), 3.7–3.4 (m, 72 H,
24 H, 12 CH2O), 3.34 (s, 3 H, OCH3), 3.33 (s, 3 H, OCH3), 1.33 36 CH2O), 3.32 (s, 9 H, 3 OCH3), 3.31 (s, 9 H, 3 OCH3) ppm. 13C
(s, 12 H, 4 CH3), 0.28 [s, 9 H, Si(CH3)3] ppm. 13C NMR (100 MHz,
NMR (100 MHz, CDCl3): δ = 141.8 (3 C), 140.9 (3 C), 140.1 (3
CDCl3): δ = 144.6 (C), 144.4 (C), 141.1 (C), 139.1 (C), 137.8 (C), C), 139.9 (3 C), 137.2 (6 CH), 135.1 (3 C), 134.9 (6 CH), 134.5 (3
133.3 (CH), 133.0 (2 CH), 129.2 (C), 128.6 (2 CH), 83.6 (2 C-O), C), 134.4 (3 C), 131.4 (3 CH), 131.3 (6 CH), 130.7 (3 CH), 128.8
72.1 (CH2O), 71.89 (CH2O), 71.88 (CH2O), 70.9 (CH2O), 70.62 (6 CH), 93.1 (3 C-I), 71.8 (6 CH2O), 70.9 (3 PhCH2), 70.7 (3
(CH2O), 70.56 (4 CH2O), 70.50 (2 CH2O), 70.47 (CH2O), 69.6 PhCH2), 70.51 (12 CH2O), 70.48 (12 CH2O), 69.7 (6 CH2O), 58.99
(CH2O), 69.5 (CH2O), 59.0 (2 CH3O), 24.9 (4 CH3), –1.1 [Si(CH3) (3 OCH3), 58.96 (3 OCH3) ppm. HRMS (ESI): calcd. for
3] ppm. MS: m/z (%) = 704 (Ͻ1) [M]+, 540 (24), 376 (26), 147 (42),
103 (36), 73 (58), 59 (100). HRMS (ESI): calcd. for C37H61BO10S-
iNa 727.4025; found 727.4017.
C102H133I3O25SiNa 2189.5937; found 2189.5962.
Tripod 12
Ethoxy Tri(4Ј-trimethylsilyl[4,1Ј]biphenyl)silane (12): Following the
procedure outlined for 1, compound 6 (0.10 g, 0.15 mmol) was cou-
pled with p-(carboxymethyl)phenylboronic acid pinacol ester
(0.14 g, 0.50 mmol) in the presence of Ag2CO3 (0.50 g, 0.90 mmol)
and Pd(PPh3)4 (0.02 g, 0.02 mmol) in refluxing THF (20 mL) for
12 h. Compound 12 was isolated by column chromatography (cy-
clohexanes/CH2Cl2, 9:1) to give a white solid (50 mg, 47%). M.p.
158–160 °C. 1H NMR (400 MHz, CDCl3): δ = 8.11 (d, J = 7.8 Hz,
6 H, Ar-H), 7.77 (d, J = 7.8 Hz, 6 H, Ar-H), 7.69–7.65 (m, 12 H,
Ar-H), 3.94 (q, J = 7 Hz, 2 H, OCH2CH3), 3.90 (s, 9 H, 3 OCH3),
1.28 (t, J = 7 Hz, 3 H, OCH2CH3). 13C NMR (100 MHz, CDCl3):
δ = 166.9 (3 C=O), 145.2 (3 C), 141.6 (3 C), 135.9 (6 CH), 134.0
(6 CH), 130.1 (3 C), 129.2 (3 C), 127.1 (6 CH), 126.8 (6 CH), 59.9
(OCH2CH3), 52.1 (3 OCH3), 18.4 (OCH2CH3). MS: m/z (%) = 706
[M]+, 683 (18), 682 (65) [M]+, 555 (28), 479 (84), 435 (100), 324
(25). HRMS (ESI): calcd. for C44H38O7SiNa 729.2284; found
729.2286.
Tri{2Ј,5Ј-bis[(2-methoxyethoxy)methyl]-4ЈЈ-trimethylsilyl-
[4,1Ј;4Ј,1ЈЈ]}terphenylsilanol (3a): Following the procedure outlined
for 2a, compound 6 (0.13 g, 0.20 mmol) was coupled with 11
(0.43 g, 0.66 mmol) in the presence of Cs2CO3 (0.04 g, 1.19 mmol)
and Pd(PPh3)4 (0.02 g, 0.02 mmol) in H2O (3 mL) and DME
(10 mL). Compound 3a was isolated by column chromatography
(cyclohexanes/EtOAc, 9:1) to give a colorless syrup (172 mg, 43%).
IR (KBr): ν = 2870, 1092, 836 cm–1. 1H NMR (400 MHz, CDCl ):
˜
3
δ = 7.57 (d, J = 8.0 Hz, 6 H, Ar-H), 7.60–7.48 (m, 18 H, Ar-H),
7.42 (d, J = 8.0 Hz, 6 H, Ar-H), 4.51 (s, 6 H, 3 PhCH2), 4.47 (s, 6
H, 3 PhCH2), 3.8–3.4 (m, 72 H, 36 CH2O), 3.31 (s, 9 H, 3 OCH3),
3.30 (s, 9 H, 3 OCH3), 0.30 [s, 27 H, 3 Si(CH3)3] ppm. 13C NMR
(100 MHz, CDCl3): δ = 142.2 (3 C), 141.1 (3 C), 140.7 (3 C), 140.5
(3 C), 139.1 (3 C), 135.2 (6 CH), 134.8 (3 C), 134.7 (3 C), 133.1 (6
CH), 132.4 (3 C), 131.1 (3 CH), 130.9 (3 CH), 128.9 (6 CH), 128.6
(6 CH), 71.8 (6 CH2O), 70.9 (3 PhCH2), 70.8 (3 PhCH2), 70.6 (12
CH2O), 70.5 (12 CH2O), 69.6 (6 CH2O), 59.0 (6 OCH3), –1.1 [3
Si(CH3)3] ppm. HRMS (ESI): calcd. for C111H160O25Si4Na
2028.0224; found 2028.0750.
Acknowledgments
Ethoxy Tri{2Ј,5Ј-bis[(2-methoxyethoxy)methyl]-4ЈЈ-trimethylsilyl-
[4,1Ј;4Ј,1ЈЈ]}terphenylsilane (3b): Following the procedure outlined
for 1, compound 6 (0.08 g, 0.12 mmol) was coupled with 11 (0.25 g,
0.40 mmol) in presence the of Cs2CO3 (0.02 g, 0.60 mmol),
Pd(PPh3)4 (0.01 g, 0.01 mmol), toluene (5 mL), and absolute EtOH
(4 mL). Compound 3b was isolated by column chromatography
This work was funded by the Spanish Ministerio de Ciencia e Inno-
vación (Project Numbers NAN04-09312-C03, CTQ2007-62386-
PPQ, and CTQ2009-08549), Junta de Andalucía (Project Number
FQM-01895), and The Welch Foundation (grant E-1498 to C.C.).
(cyclohexanes/EtOAc, 9:1) as a colorless syrup (39 mg, 16%). IR
1
(KBr): ν = 2868, 1097, 837 cm–1. H NMR (400 MHz, CDCl ): δ
˜
[1] L. Nebhani, B.-C. Kowollik, Adv. Mater. 2009, 21, 3442–3468.
3
= 7.78 (d, J = 8.0 Hz, 6 H, Ar-H), 7.57 (d, J = 8.0 Hz, 6 H, Ar- [2] H. C. Kolb, M. G. Finn, K. B. Sharpless, Angew. Chem. Int.
Ed. 2001, 40, 2004–2021.
H), 7.51 (d, J = 8.0 Hz, 6 H, Ar-H), 7.50 (s, 6 H, Ar-H), 7.43 (d,
J = 8.0 Hz, 6 H, Ar-H), 4.53 (s, 6 H, 3 PhCH2), 4.48 (s, 6 H, 3
PhCH2), 3.99 (q, J = 7.2, 7.2 Hz, 2 H, OCH2CH3), 3.63–3.45 (m,
72 H, 36 CH2O), 3.31 (s, 9 H, 3 OCH3), 3.30 (s, 9 H, 3 OCH3),
1.34 (t, J = 7.2 Hz, 3 H, OCH2CH3), 0.31 [s, 27 H, 3 Si(CH3)3]
ppm. 13C NMR (100 MHz, CDCl3): δ = 142.0 (3 C), 141.0 (3 C),
140.7 (3 C), 140.4 (3 C), 139.0 (3 C), 135.1 (6 CH), 134.7 (3 C),
134.6 (3 C), 133.0 (6 CH), 132.9 (3 C), 131.0 (3 CH), 130.8 (3 CH),
128.8 (6 CH), 128.6 (6 CH), 71.77 (3 CH2O), 71.75 (3 CH2O), 70.8
(3 PhCH2), 70.7 (3 PhCH2), 70.48, 70.45, 70.42, 70.38, 70.36 (24
CH2O), 69.56 (3 CH2O), 69.52 (3 CH2O), 59.8 (OCH2CH3), 58.87
(3 OCH3), 58.85 (3 OCH3), 18.4 (OCH2CH3), –1.1 [3 Si(CH3)3]
ppm. HRMS (ESI): calcd. for C113H164O25Si4Na 2056.0536; found
2056.0530.
[3] M. Meldal, C. W. Tornoe, Chem. Rev. 2008, 108, 2952–3015.
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