Convergent synthesis of 10 nm aryleneethynylene molecular wires by an iterative regioselective deprotection/sonogashira coupling protocol

Article abstract of DOI:10.1021/jo051711o

The synthesis of a new series of rigid-rod aryleneethynylene derivatives of up to ca. 10 nm molecular length (compounds 16 and 17) is reported using iterative Pd-mediated Sonogashira coupling methodology combined with regioselective removal of the differe

Full text of DOI:10.1021/jo051711o

Convergent Synthesis of 10 nm Aryleneethynylene Molecular Wires
by an Iterative Regioselective Deprotection/Sonogashira Coupling
Protocol
Changsheng Wang, Andrei S. Batsanov, and Martin R. Bryce*
Department of Chemistry, UniVersity of Durham, Durham DH1 3LE, U.K.
m.r.bryce@durham.ac.uk
ReceiVed August 12, 2005
The synthesis of a new series of rigid-rod aryleneethynylene derivatives of up to ca. 10 nm molecular
length (compounds 16 and 17) is reported using iterative Pd-mediated Sonogashira coupling methodology
combined with regioselective removal of the different protecting groups (namely, trimethylsilyl and
2-hydroxyprop-2-yl groups) from the terminal alkyne units. Additionally, the TMS-acetylene unit has
been cleanly deprotected to afford a terminal alkyne in the presence of a cyanoethylsulfanyl group. Some
of these molecular wires are functionalized with terminal protected thiophenol units for attachment to
metal surfaces (compounds 16 and 17). Internal electron-acceptor units have been incorporated into their
structures, namely, 9-[di(4-pyridyl)methylene]fluorene (compound 17) or fluorenone (compounds 19-
22). Optical absorption and photoluminescence spectra reveal a red shift in the value of λmax with increasing
molecular length, which approaches saturation at an effective conjugation length of ca. 15-20 π-units in
the molecules, where each phenyl ring or a triple bond is counted as one π-unit.
Introduction
arylenevinylene counterparts is the lack of possible Z/E isomer-
ism. Specific examples include: (a) 2,5-thienylethynylene
oligomers with protected thiol termini;6 (b) p-phenyleneeth-
ynylene oligomers with 5,5′-diethynyl-2,2′-bipyridine moieties
in the backbone;7 (c) 5,5′-diethynyl-2,2′-bipyridine-derived
systems as metal-binding scaffolds;8,9 (d) phenyleneethynylene
pentamers10 and oligo(9,9-dihexyl-2,7-fluorenylethynylenes)11
as fluorophores for organic light-emitting devices; (e) co-
oligomers possessing phenylene- and heterocyclic-enediyne units
in the backbone which are fluorescent;12 (f) a poly(p-phenyl-
eneethynylene) derivative bearing macromolecular polyester
Functional π-conjugated systems which are available in
incremental lengths from ca. 1 to 10 nm are of particular interest
from experimental and theoretical viewpoints as advanced
electronic and photonic materials.1 For example, new fabrication
methods and probes allow these “molecular wires” to be
connected in a controlled manner into hybrid organic/semicon-
ductor device architectures,2 thereby paving the way for studies
of single-molecule devices.3 To enable the covalent anchoring
of wire molecules to metal surfaces, thiols (or protected thiols)
are the most widely used terminal groups.4
Ethynylated aromatic/heteroaromatic systems, with the ge-
neric structure (aryl-CtC-)n, are versatile, shape-persistent,
rigid-rod molecules.5 An attraction compared to that of their
(4) (a) Tour, J. M.; Rawlett, A. M.; Kozaki, M.; Yao, Y.; Jagessar, R.
C.; Dirk, S. M.; Price, D. W.; Reed, M. A.; Zhou, C.-W.; Chen, J.; Wang,
W.; Campbell, I. Chem.-Eur. J. 2001, 7, 5118. (b) Wei, L.; Padmaja, K.;
Youngblood, W. J.; Lysenko, A. B.; Lindsey, J. S.; Bocian, D. J. Org.
Chem. 2004, 69, 1461. (c) Flatt, A. K.; Yao, Y.; Maya, F.; Tour, J. M. J.
Org. Chem. 2004, 69, 1752.
(1) (a) Electronic Materials: The Oligomer Approach; Wegner, G.,
Mu¨llen, K., Eds.; Wiley-VCH: Weinheim, Germany, 1998. (b) Tour, J.
M. Acc. Chem. Res. 2000, 33, 791. (c) Robertson, N.; McGowan, C. A.
Chem. Soc. ReV. 2003, 32, 96. (d) Benniston, A. C. Chem. Soc. ReV. 2004,
33, 573. (e) Low, P. J. Dalton Trans. 2005, 2821.
(5) Bunz, U. H. F. Chem. ReV. 2000, 100, 1065.
(6) Pearson, D. L.; Tour, J. M. J. Org. Chem. 1997, 62, 1376.
(7) Ley, K. D.; Li, Y.; Johnson, J. V.; Powell, D. H.; Schanze, K. S.
Chem. Commun. 1999, 1749.
(2) Reviews: (a) Joachim, C.; Gimewski, J. K.; Aviram, A. Nature 2000,
408, 541. (b) James, D. K.; Tour, J. M. Chem. Mater. 2004, 16, 4423. (c)
McCreery, R. L. Chem. Mater. 2004, 16, 4477.
(3) (a) Maruccio, G.; Cingolani, R.; Rinaldi, R. J. Mater. Chem. 2004,
14, 542. (b) Wassel, R. A.; Gorman, C. B. Angew. Chem., Int. Ed. Engl.
2004, 33, 5120.
(8) Khatyr, A.; Ziessel, R. J. Org. Chem. 2000, 65, 7814.
(9) Goeb, S.; De Nicola, A.; Ziessel, R. J. Org. Chem. 2005, 70, 1518.
(10) (a) Anderson, S. Chem.-Eur. J. 2001, 7, 4706. (b) Atienza, C.;
Insuasty, B.; Seoane, C.; Mart´ın, N.; Ramey, J.; Rahman, G. M. A.; Guldi,
D. M. J. Mater. Chem. 2005, 15, 124.
(11) Lee, S. H.; Nakamura, T.; Tsutsui, T. Org. Lett. 2001, 3, 2005.
10.1021/jo051711o CCC: $33.50 © 2006 American Chemical Society
Published on Web 11/18/2005
108
J. Org. Chem. 2006, 71, 108-116

Synthesis of Aryleneethynylene Molecular Wires
substituents;13 (g) oligomers containing 1,3,5-ethynylphenyl
units; and14,15 (h) fluorenone-containing aryleneethynylene oli-
gomers which are electron dopable.16
extended the aryleneethynylene system are iterative cross-
coupling/deprotection procedures, leading to derivatives with
alternating dihexyloxyphenyl and biphenyl units in the back-
bone. Thus, reaction of 4 with 2 gave 5. The deprotection of 5
proceeded smoothly, as above, to afford 6 in 93% yield.
Following these procedures, compounds 7-12 were obtained
with good yields (69-99%) at each step. A benefit of the
2-hydroxy-2-propyl protecting group is that its high polarity
facilitates the chromatographic separation of any unreacted
starting material or byproducts which do not contain this unit.
Apart from 1 and 2 which require monocouplings to diiodo
reagents, we tried to avoid using piperidine because of its
toxicity and unpleasant smell. Triethylamine was, therefore, used
in some steps. However, as the chain length increased, solubility
in triethylamine was reduced, and THF was needed to dissolve
the building blocks. In some cases, we had to use piperidine,
such as in, for example, the cross-couplings of 10 and 14 with
the corresponding iodides. The molar concentrations of the
terminal alkynes varied for solubility reasons, although the
reactions were very similar and iterative. The extended reaction
times at later stages of the synthesis ensured the complete
consumption of the precious alkynes and suppressed competing
self-coupling reactions. Further optimization of the conditions
might give a higher yield of 17.
To obtain an oligomeric unit end capped with a protected
thiol group, a Sonogashira reaction of 12 with 4-(2-cyanoeth-
ylsulfanyl)iodobenzene16 gave 13 in 84% yield. In the next step,
deprotection of the TMS-acetylene fragment of 13 with
potassium carbonate gave 14, without competing removal of
the cyanoethyl group (which would be cleaved under more
strongly basic conditions, typically sodium alkoxide or TBAF
at room temperature).16 In the final convergent step, a 2-fold
Sonogashira reaction of 14 with the difunctional reagent 15
yielded 17 (18% yield) along with the self-coupled butadiyne
derivative 16 (27% yield). The intramolecular S‚‚‚S′ distances
for 16 and 17 (MM+ calculated values using Hyperchem 6.03)
are 9.9 and 10.4 nm, respectively.
Scheme 2 illustrates how the selective removal of the TMS
group in 3 has been used to furnish a different series of extended
aryleneethynylene derivatives. Compound 18 was obtained in
96% yield by reaction of 3 with potassium carbonate in DCM/
MeOH at room temperature. Two-fold cross-coupling of 18 with
2,7-diiodo-9-fluorenone gave the symmetrical product 19 in 92%
yield, from which the terminal alkyne units were liberated upon
treatment with sodium hydroxide in refluxing toluene (as in
Scheme 1). Iterative reactions using reagent 2 gave compound
21, and subsequent deprotection gave the π-extended system
22. This family of molecular wires with terminal alkyne
substituents could be suitable for the fabrication of devices using
silicon electrodes.21
The X-ray crystal structure of 21 is shown in Figure 1. The
asymmetric unit of 21‚2CDCl3 contains one formula unit. The
molecular rod of 21 has a slightly S-shaped conformation. The
bonds C(23)-C(24), C(27)-C(30), C(37)-C(38), and C(76)-
C(77) are inclined to the plane of the fluorenone moiety by
16.2, 13.1, 4.2, and 13.2°, respectively. The maximum length
of the molecule (by the van der Waals shape) is ca. 56 Å. Two
deuteriochloroform molecules (one of which is disordered by
rotation around its 3-fold axis) are linked to 21 via C-D‚‚‚O
hydrogen bonds. Molecules of 21, related by an inversion center,
We now report the synthesis using iterative Pd-mediated
Sonogashira coupling methodology17 of new, linearly conjugated
aryleneethynylenes, notably the ca. 10 nm molecular wires, 16
and 17. Our route differs from Tour’s iterative approaches to
oligo(aryleneethynylene) wires in the following ways. Iodinated
thiophenes are the key building blocks for Tour’s 2,5-thienyl-
ethynylene oligomers.6 However, because most phenyl deriva-
tives cannot be iodinated by a lithiation/iodination protocol, this
route has limited applicability to systems other than thiophene.
The second route of Tour’s is rather tedious, involving consecu-
tive hydrogenation, Friedel Craft’s acylation, diazotization, and
Sonogashira reactions, which limited the incorporation of
functionality into the oligomer/polymer.18 An aspect which is
crucial to the success of our syntheses is the functionalization
of terminal alkynes with different protecting groups (namely,
trimethylsilyl and 2-hydroxy-2-propyl groups) and the regio-
selective removal of each one in the presence of the other. The
methodology is versatile and has many attractive features, as
illustrated by the end capping of the wires with cyanoethyl-
protected thiophenol derivatives (compounds 16 and 17) and
the inclusion of redox-active moieties, either di(4-pyridyl)-
methylene-9-fluorene (compound 17) or fluorenone (compounds
19-22), in the backbone.
Results and Discussion
Synthesis. Scheme 1 shows the protocol based on the
selective removal9,14 of the 2-hydroxy-2-propyl protecting group
(as acetone) from the unsymmetrical intermediates 3, 5, 7, 9,
and 11, followed at each stage by a Sonogashira cross-coupling
reaction. Starting reagents 1 and 2 were obtained from 1,4-
dihexyloxy-2,5-diiodobenzene19 and 4,4′-diiodobiphenyl, re-
spectively, in 50% and 43% yields by reaction with one
equivalent of 3-hydroxy-3-methylbutyne under standard Sono-
gashira conditions (Pd[PPh3]2Cl2, CuI, piperidine). The hexyl
substituents in 1 prevent solubility problems at later stages of
the synthesis. Initial attempts at preparing 1 using triethylamine
or triisopropylamine instead of the stronger base piperidine were
unsuccessful: only starting materials were recovered. On the
basis of this result, the conditions for the synthesis of 2 were
formulated: for 2, either neat piperidine or piperidine/THF can
be used. Compound 1 was converted into the key reagent 3 by
reaction with trimethylsilylacetylene (Pd[PPh3]2Cl2, CuI, tri-
ethylamine) in 95% yield. Refluxing 3 in toluene in the presence
of sodium hydroxide20 removed the 2-hydroxy-2-propyl unit to
give 4 in 77% yield. The subsequent reactions which linearly
(12) (a) Utesch, N. F.; Diederich, F. Org. Biomol. Chem. 2003, 1, 237.
(b) Nakano, Y.; Ishizuka, K.; Muraoka, K.; Ohtani, H.; Takayama, Y.; Sato,
F. Org. Lett. 2004, 6, 2373.
(13) Wang, Y.; Erdogan, B.; Wilson, J. N.; Bunz, U. H. F. Chem.
Commun. 2003, 1624.
(14) Rodr´ıguez, J. G.; Esquivias, J.; Lafuente, A.; D´ıaz, C. J. Org. Chem.
2003, 68, 8120.
(15) Kozaki, M.; Okada, K. Org. Lett. 2004, 6, 485.
(16) Wang, C.; Batsanov, A. S.; Bryce, M. R.; Sage, I. Org. Lett. 2004,
6, 2181.
(17) Sonogashira, K. J. Organomet. Chem. 2002, 653, 46 and references
therein.
(18) Jones, L. R., II; Schumm, J. S.; Tour, J. M. J. Org. Chem. 1997,
62, 1388.
(19) Peng, Z.; Gharavi, A. R.; Yu, L. J. Am. Chem. Soc. 1997, 119,
4622.
(20) Armes, D. E.; Bull, D.; Takunda, C. Synthesis 1981, 364.
(21) Hurley, P. T.; Ribbe, A. E.; Buriak, J. M. J. Am. Chem. Soc. 2003,
125, 11334.
J. Org. Chem, Vol. 71, No. 1, 2006 109

Wang et al.
SCHEME 1a
a Reagents and conditions: (i) piperidine, Pd[PPh3]2Cl2, CuI, HCtCCMe2OH (1.1 equiv), 50 °C (50% yield); (ii) THF, piperidine, Pd[PPh3]2Cl2, CuI,
HCtCCMe2OH (1.2 equiv), 50 °C (43% yield); (iii) THF, NEt3, Pd[PPh3]2Cl2, CuI, TMSCtCH, 50 °C (95% yield); (iv) toluene, NaOH, reflux (77%
yield); (v) 2, NEt3, Pd[PPh3]2Cl2, CuI, 60 °C (86% yield); (vi) toluene, NaOH, reflux (93% yield); (vii) 1, NEt3, Pd[PPh3]2Cl2, CuI, 60 °C (69% yield); (viii)
toluene, NaOH, reflux (77% yield); (ix) 2, NEt3, Pd[PPh3]2Cl2, CuI, 80 °C (85% yield); (x) toluene, NaOH, reflux (99% yield); (xi) 1, THF, piperidine,
Pd[PPh3]2Cl2, CuI, 50 °C (80% yield); (xii) toluene, NaOH, reflux (97% yield); (xiii) 4-(2-cyanoethylsulfanyl)iodobenzene, NEt3, Pd[PPh3]2Cl2, CuI, THF,
50 °C (84% yield); (xiv) K2CO3, THF, MeOH, 20 °C (62% yield); (xv) 15 (0.5 equiv), THF, piperidine, Pd[PPh3]2Cl2, CuI, 50 °C, 16 (27% yield) + 17
(18% yield).
form a dimer linked at both ends by intermolecular hydrogen
bonds O(7)-H‚‚‚O(4′) [O‚‚‚O 2.775(2), O-H 0.82(3), H‚‚‚O
1.96(3) Å, O-H‚‚‚O angle 178(2)°] and its equivalent O(7′)-
H‚‚‚O(4), whereas the hydroxyl group O(4)-H is hydrogen
110 J. Org. Chem., Vol. 71, No. 1, 2006

Synthesis of Aryleneethynylene Molecular Wires
SCHEME 2a
a Reagents and conditions: (i) K2CO3, DCM, MeOH, 20 °C (96% yield); (ii) 2,7-diiodo-9-fluorenone (0.5 equiv), THF, NEt3, Pd[PPh3]2Cl2, CuI, 50 °C
(92% yield); (iii) toluene, NaOH, reflux (96% yield); (iv) 2 (2.2 equiv), THF, NEt3, Pd[PPh3]2Cl2, CuI, 55 °C (64% yield); (v) toluene, NaOH, reflux (92%
yield).
FIGURE 1. Molecular structure of 21‚2CDCl3 showing hydrogen bonds (other H atoms are omitted) (top) and a dimer (21)2 linked by O-H‚‚‚O
bonds (bottom).
bonded to the triple bond, C(61)tC(62), of another dimer,
related by the translation 2a-c.
Electrochemical Properties. The di(4-pyridyl)methylene-9-
fluorene and fluorenone units impart electron-acceptor charac-
teristics to molecules 17 and 19-22. Cyclic voltammograms
(CVs) of the two symmetrical fluorenone derivatives 20 and
22 are given Figure 2, where two reversible redox waves were
observed when the reduction potentials were limited between
J. Org. Chem, Vol. 71, No. 1, 2006 111

Wang et al.
TABLE 1. UV-Vis Absorption and Photoluminescence Data in
Chloroform Solution
PL
max/nm
absorption λmax/nm (log ꢀ)
compound
λ
4
6
8
10
12
14
16
17
20
22
267(4.36) 280(4.58) 340(4.05)
321(4.72) 368(4.63)
272(4.60) 325(4.85) 374(4.99)
329(4.85) 388(5.03)
380
411
415
431
433
434
451
451
589
597
330(4.91) 390(5.15)
330(4.95) 391(5.18)
330(5.25) 405(5.53)
332(5.29) 401(5.58)
305(4.86) 381(4.84) 452(3.92)
268(3.78) 325(4.99) 396(5.10) 465(4.23) sh
FIGURE 2. Cyclic voltammograms of 20 and 22 in THF vs Ag/Ag+.
FIGURE 3. Differential pulse voltammograms of compounds 17 and
22 in THF vs Ag/Ag+.
0 and -2.3 V. This type of twin-wave reversible redox
chemistry is in agreement with that of 2,7-diethynyl-9-fluo-
renone, the smallest analogue of this class of compounds.22
When the potential was scanned further down to -2.6 V, another
pair of irreversible waves was observed for 22. In the meantime,
the first two redox waves also became irreversible, which is
consistent with a chemical reaction occurring under the strongly
reducing conditions. A differential pulse voltammogram (DPV)
(Figure 3, lower) clearly shows the four reduction waves of
compound 22. No further reduction waves of 20 could be clearly
observed on scanning to more negative potentials; presumably,
these waves (if present) would appear at more cathodic potentials
outside the solvent window because of the smaller number of
triple bonds and the absence of the biphenylene units. For
compound 17, an irreversible fluorenone-type reduction (-1.42
V) due to the di(4-pyridyl)methylene-9-fluorene moiety was
observed, followed by more intense irreversible reduction waves
(-2.12 V) ascribed to the -CtC- units (Figure 2, upper). For
the butadiyne analogue 16, only the irreversible alkyne-related
reduction wave was observed at -2.20 V (data not shown).
Optical Properties. The availability of a series of arylene-
ethynylene oligomers gives us the opportunity to assess the
extent of electronic delocalization along the backbone by
comparing their optical spectra. The solution UV-vis absorption
and photoluminescence spectra of the terminal alkynes with
FIGURE 4. UV-vis absorption spectra (top) and photoluminescence
spectra (bottom) of compounds 16 and 17 compared with those of other
terminal ethynyl building blocks in chloroform solution. For PL
measurements, the excitation wavelength λexc ) 320 nm for all the
compounds, except for 4 (λexc ) 280 nm).
different conjugation lengths, namely, compounds 4, 6, 8, 10,
12, and 14, were obtained and compared with those of molecules
16 and 17 (Table 1 and Figure 4). As the length of the molecules
increased, both the wavelength and the intensity of the primary
λmax (the low-energy bands for 4 and 6) increased. However,
the λmax red shifts were not linearly proportional to the increase
in the molecular length. A plot of the red shift values against
the number of the conjugated π-units (Figure 5) reveals that
the red shift approaches saturation at an effective conjugation
length of ca. 15-20 π-units in the molecules, where each phenyl
ring or a triple bond is counted as one π-unit. (See the
(22) Price, D. W.; Tour, J. M. Tetrahedron 2003, 59, 3131. Wang, C.;
Batsanov, A. S.; Bryce, M. R. Faraday Discuss. 2005, 131, DOI: 10.1039/
b506712j.
112 J. Org. Chem., Vol. 71, No. 1, 2006

Synthesis of Aryleneethynylene Molecular Wires
(DPVs) were recorded in THF-TBA‚PF6 (0.1 M) solution, and
the potentials quoted were referenced to the Ag/Ag+ nonaqueous
reference electrode, which contained a solution of 0.01 M AgNO3
and 0.1 M TBAPF6 in acetonitrile. Pt disk (Φ ) 1.6 mm) and Pt
wire were used as the working and counter electrodes, respectively.
For CVs, the potentials were scanned at 100 mV/sec, and for DPVs,
the potential was scanned at the rate of 50 mV/sec (pulse amplitude
50 mV; pulse width 50 ms). THF was purified with a commercial
solvent purification system and then bubbled with argon through
the solutions for 5 min prior to CV and DPV measurements. Under
these conditions, the background from 0 to -2.50 V was transparent
to reductions and ferrocene was oxidized at a half-wave potential
of 0.22 V.
All the palladium-catalyzed coupling reactions were carried out
under argon atmosphere. THF, used for those reactions, and toluene,
used for the deprotection reactions, were purified using a solvent
purification system. Triethylamine (TEA) was purchased from a
commercial supplier and then refluxed and distilled over sodium
in argon atmosphere. Pd[PPh3]2Cl2 was prepared in our laboratory
using a reported method.25 Piperidine was purchased from a
commercial supplier, dried over sodium hydroxide pellets for a
week, and then distilled under argon. Other chemicals and routine
solvents were used as purchased, without further purification.
X-ray Crystallography. The X-ray diffraction experiment was
carried out on a three-circle diffractometer with a 6 K CCD area
detector, using graphite-monochromated Mo KR radiation (λh )
0.71073 Å) and an open-flow N2 cryostat. The structure was solved
by direct methods and refined by full-matrix least squares against
F2 of all reflections, using SHELXTL software (version 6.12, Bruker
AXS, Madison WI, 2001). Crystal data: C91H92O7 (21)‚2CDCl3;
M ) 1538.39; T ) 120 K; triclinic; space group P1h (No. 2); a )
12.985(1), b ) 14.504(1), c ) 23.877(2) Å; R ) 91.64(1), â )
100.62(1), γ ) 111.35(1)°; V ) 4094.1(6) Å3; Z ) 2; Dc ) 1.248
g cm-3; µ ) 0.27 mm-1; 46 302 reflns with 2θ e 55°, 18 788
unique; Rint ) 0.058, final R ) 0.049 [11 599 data with F2 g 2σ-
(F2)], wR(F2) ) 0.133 (all data). CCDC-280163.
FIGURE 5. UV-vis and PL red shift values of compounds 4, 6, 8,
10, 12, 14, 16, and 17 plotted against the number of conjugated π-units
in the molecules. Each phenyl ring or a triple bond is counted as one
π-unit.
Supporting Information for further discussion.) A similar
convergence of λmax with increasing conjugation length has been
observed in previous phenyleneethynylene oligomers10,23 and
oligo(9,9-dihexyl-2,7-fluorenylethynylenes).11 The broad, low-
intensity emission from 20 and 22 is typical of that of fluorenone
derivatives.24
Conclusions
We have presented the synthesis of a range of new highly
functionalized aryleneethynylene reagents and building blocks
up to 10 nm in length which are amenable to full spectroscopic
and analytical characterization. These molecular wires are
endowed with terminal functionality suitable for further reactions
or for attachment to metal surfaces (compounds 16 and 17).
Moreover, internal electron-acceptor units have been incorpo-
rated into their structures (compounds 16 and 19-22). A key
aspect of the synthetic strategy is the judicious choice of terminal
alkyne protecting groups (namely, trimethylsilyl and 2-hydroxy-
2-propyl groups) and their regioselective removal. We have also
established that the TMS-acetylene unit can be cleanly depro-
tected to afford a terminal alkyne in the presence of a
cyanoethylsulfanyl group. These oligomers show well-defined
optical absorption and emission properties, and electrochemical
studies have established that compounds 16 and 19-22 are n
dopable. These reagents and procedures should be valuable and
highly versatile in molecular electronics applications related to
supramolecular assembly and nanocircuits.
1,4-Dihexyloxy-2-(3-hydroxy-3-methylbutynyl)-5-iodoben-
zene (1). 1,4-Dihexyloxy-2,5-diiodobenzene26 (26.5 g, 50 mmol)
was dissolved in freshly distilled piperidine (250 mL). Pd[PPh3]2-
Cl2 (1.8 g) and CuI (0.6 g) were added to the solution followed by
the addition of 3-hydroxy-3-methylbutyne (4.4 g, 52.3 mmol) in
one portion. The mixture was stirred at room temperature for 1 h
and then at 50 °C for an additional 1 h. The solvent was removed
by vacuum evaporation. Diethyl ether (200 mL) was added to the
brown residue followed by a suction filtration through a Celite pad.
The filtrate was concentrated and then chromatographed (silica gel,
DCM-diethyl ether, 99:1 v/v) to afford 1 (12.2 g, 50%) as a pale-
1
yellow oil which solidified upon storage: mp 48.9-50.7 °C; H
NMR (300 MHz, CDCl3) δ 7.25 (s, 1H), 6.80 (s, 1H), 3.93 (t, J )
6.3 Hz, 4H), 2.23 (s, 1H), 1.78 (m, 4H), 1.62 (s, 6H), 1.49 (m,
4H), 1.34 (m, 8H), 0.91 (m, 6H); 13C NMR (75 Hz, CDCl3) δ 154.3,
151.7, 123.6, 116.1, 112.9, 98.5, 87.4, 78.1, 70.0, 69.7, 65.7, 31.5,
31.44, 31.36, 29.2, 29.1, 25.7, 25.6, 22.59, 22.55, 14.0; MS (ES+)
(m/z) 509.2 (M+ + 23, 100%). Anal. Calcd for C23H35IO3: C, 56.79;
H, 7.25. Found: C, 56.90; H, 7.35.
Experimental Section
4-(3-Hydroxy-3-methylbutynyl)-4′-iodobiphenyl (2). By anal-
ogy to the synthesis of 1, 4,4′-diiodobiphenyl (8.12 g, 20 mmol)
reacted with 3-hydroxy-3-methylbutyne (2.0 g, 23.7 mmol) in a
mixture of THF (80 mL) and piperidine (20 mL), in the presence
of Pd[PPh3]2Cl2 (0.5 g) and CuI (0.25 g). The mixture was stirred
at 50 °C for 2 h to yield an orange suspension. The crude product
was chromatographed (silica gel, DCM-diethyl ether mixture, 95:5
v/v) and then crystallized from an ethanol-water mixture to afford
2 as pale-yellow needles (3.08 g, 43%, mp 179.6-180.1 °C): 1H
General. Melting points were determined in open-end capillaries,
and the temperatures were ramped at 5 °C min-1 near the melting
temperatures, without calibration. Solution 1H NMR and 13C NMR
spectra were recorded on a 300, 400, or 500 MHz spectrometer
operating at (1H) 299.91, 400.13, and 499.99 and (13C) 75.42,
100.62, and 124.99 MHz, respectively. Chemical shifts are reported
in ppm downfield of TMS. MALDI-TOF spectra were obtained
using a dithranol matrix operating in reflector mode. Cyclic
voltammograms (CVs) and differential pulse voltammograms
(23) Francke, V.; Mangel, T.; Mu¨llen, K. Macromolecules 1998, 31,
2447.
(25) Heck, R. F. Palladium Reagents in Organic Synthesis; Academic
Press: London, 1985, p 18.
(24) Pschirer, N. G.; Byrd, K.; Bunz, U. H. F. Macromolecules 2001,
34, 8590.
(26) Peng, Z.; Gharavi, A. R.; Yu, L. J. Am. Chem. Soc. 1997, 119,
4622.
J. Org. Chem, Vol. 71, No. 1, 2006 113

Wang et al.
NMR (300 MHz, CDCl3) δ 7.76 (d, J ) 8.4 Hz, 2H), 7.49 (m,
4H), 7.31 (d, J ) 8.4 Hz, 2H), 2.14 (s, 1H), 1.65 (s, 1H); 13C NMR
(75 Hz, CDCl3) δ 139.72, 139.70, 137.9, 132.1, 128.8, 126.6, 122.1,
94.7, 93.4, 81.8, 65.6, 31.5. Anal. Calcd for C17H15IO: C, 56.37;
H, 4.17. Found: C, 56.45; H, 4.17.
6H), 0.27 (s, 9H); 13C NMR (100 Hz, CDCl3) δ 154.2, 153.6, 140.7,
139.9, 132.6, 132.1, 126.9, 126.8, 122.9, 121.4, 117.4, 116.9, 114.2,
113.9, 101.2, 100.1, 94.6, 87.0, 83.4, 78.0, 69.6, 69.6, 31.61, 31.59,
29.3, 25.73, 25.70, 22.6, 14.1, 14.0, -0.05; MS (EI) (m/z) 574 (M+,
100%). Anal. Calcd for C39H46O2Si: C, 81.48; H, 8.07. Found: C,
81.49; H, 8.07.
1,4-Dihexyloxy-2-(3-hydroxy-3-methylbutynyl)-5-(trimethyl-
silylethynyl)benzene (3). A mixture of compound 1 (4.86 g, 10
mmol), Pd[PPh3]2Cl2 (0.35 g), and CuI (0.12 g) in THF (150 mL)
and triethylamine (20 mL) was degassed with argon followed by
the addition of trimethylsilylacetylene (3 mL, 21 mmol). The flask
was sealed with a glass stopper, reacted at room temperature for
1.5 h, and then at 50 °C for an additional 1.5 h to afford a brown
suspension. The mixture was vacuum evaporated to dryness, and
the solid residue was boiled with hexane (100 mL). The solution
was suction filtered through a Celite pad, and the filtrate was
concentrated in vacuo. The oily residue was column chromato-
graphed (silica gel, DCM) to afford 3 as a pale-yellow oil which
turned into an amorphous solid upon standing (4.32 g, 95%, mp
67.1-69.5 °C): 1H NMR (400 MHz, CDCl3) δ 6.89 (s, 1H), 6.84
(s, 1H), 3.93 (t, J ) 6.4 Hz, 4H), 2.23 (s, 1H), 1.77 (m, 4H), 1.60
(s, 6H), 1.53 (m, 4H), 1.33 (m, 8H), 0.89 (m, 6H), 0.25 (s, 9H);
13C NMR (100 Hz, CDCl3) δ 154.1, 153.5, 117.2, 117.1, 113.7,
113.6, 101.0, 99.8, 99.2, 78.4, 69.4, 65.7, 31.6, 31.5, 31.4, 29.3,
Compound 7. To the stirred mixture of 1 (2.92 g, 6 mmol),
Pd[PPh3]2Cl2 (0.18 g), CuI (0.06 g), and TEA (80 mL) was added
a solution of 6 (2.88 g, 5 mmol) in TEA (50 mL) dropwise within
1.5 h at 60 °C. Heating and stirring were maintained for an
additional 2 h to yield a yellow suspension. The mixture was dried
of solvent by vacuum evaporation, and the residual dark-yellow
solid was dissolved in ethanol (100 mL) with boiling. The solid
which precipitated from the cooled solution was column chromato-
graphed (silica gel, DCM). Subsequent recrystallization from
ethanol yielded 7 as a pale-yellow solid (3.23 g, 69%, mp 141.7-
142.3 °C): 1H NMR (300 MHz, CDCl3) δ 7.60 (s, 8H), 6.99 (s,
1H), 6.98 (s, 1H), 6.96 (s, 1H), 6.92 (s, 1H), 4.00 (m, 8H), 2.09 (s,
1H), 1.82 (m, 8H), 1.64 (s, 6H), 1.54 (m, 8H), 1.36 (m, 16H), 0.90
(m, 12H), 0.27 (s, 9H); 13C NMR (75 Hz, CDCl3) δ 154.1, 153.6,
153.53, 153.46, 140.0, 132.0, 126.8, 122.7, 117.2, 117.0, 116.74,
116.69, 114.1, 113.8, 113.7, 113.3, 101.1, 100.1, 99.2, 94.7, 94.6,
86.91, 86.86, 78.5, 69.6, 69.5, 69.44, 69.40, 65.8, 31.61, 31.58,
31.42, 29.3, 25.7, 22.6, 14.07, 14.05, -0.06; MS (EI) (m/z) 932
(M+, 0.4%), 660 (100%). Anal. Calcd for C62H80O5Si: C, 79.78;
H, 8.64. Found: C, 79.99; H, 8.64.
25.7, 22.6, 14.01, 13.99, -0.1; MS (ES+) (m/z) 935.8 (2M+
+
23, 100%). Anal. Calcd for C17H15IO: C, 73.63; H, 9.71. Found:
C, 73.60; H, 9.75.
1-Ethynyl-2,5-dihexyloxy-4-(trimethylsilylethynyl)benzene (4).
Compound 3 (4.60 g, 10.07 mmol) was dissolved in dry toluene
(100 mL). NaOH powder (2.0 g) was added, and the mixture was
stirred and refluxed under argon for 1 h (oil bath at 138 °C). The
resultant light-brown mixture was cooled and suction filtered
through a Celite pad. The filtrate was vacuum evaporated to dryness,
and the yellow solid was purified by column chromatography (silica
gel, petroleum ether-DCM mixture, 2:1 v/v, bp 40-60 °C) to
afford 4 as a yellow solid (3.05 g, 77%, mp 61.1-62.5 °C): 1H
NMR (300 MHz, CDCl3) δ 6.92 (s, 2H), 3.96 (t, J ) 6.6 Hz, 2H),
3.94 (t, J ) 6.6 Hz, 2H), 3.32 (s, 1H), 1.79 (m, 4H), 1.49 (s, 4H),
1.34 (m, 8H), 0.90 (m, 6H), 0.25 (s, 9H); 13C NMR (75 Hz, CDCl3)
δ 153.94, 153.92, 117.6, 117.1, 114.3, 112.7, 100.8, 100.2, 82.3,
79.9, 69.5, 69.4, 31.6, 31.5, 29.2, 29.1, 25.7, 25.5, 22.61, 22.56,
14.1, 14.0, -0.1; MS (EI) (m/z) 398 (M+, 100%). Anal. Calcd for
C17H15IO: C, 75.32; H, 9.61. Found: C, 75.60; H, 9.70.
Compound 5. Compounds 2 (3.00 g, 8.28 mmol) and 4 (3.10
g, 7.78 mmol) were dissolved in triethylamine (120 mL) with
stirring and heating at 50 °C. Pd[PPh3]2Cl2 (0.30 g) and CuI (0.10
g) were added to the solution, which was stirred at 50 °C for 0.5
h and then at 60 °C for an additional 3 h to yield a dark-yellow
suspension. The mixture was evaporated in vacuo, and diethyl ether
(150 mL) was added. The mixture was suction filtered through
Celite, and the filtrate was dried of solvent. The residual yellow
oil was column chromatographed (silica gel, DCM) to obtain 5 as
a yellow solid (4.23 g, 86%, mp 97.9-99.9 °C): 1H NMR (300
MHz, CDCl3) δ 7.55 (m, 8H), 6.98 (s, 1H), 6.96 (s, 1H), 4.01 (t,
J ) 5.1 Hz, 2H), 3.99 (t, J ) 5.1 Hz, 2H), 2.08 (s, 1H), 1.82 (m,
4H), 1.64 (s, 6H), 1.55 (m, 4H), 1.36 (m, 8H), 0.91 (m, 6H), 0.27
(s, 9H); 13C NMR (75 Hz, CDCl3) δ 154.1, 153.4, 140.0, 139.9,
132.1, 132.0, 126.8, 126.7, 122.7, 122.0, 117.2, 116.7, 114.1, 113.7,
101.1, 100.1, 94.7, 86.9, 81.9, 69.5, 69.4, 65.7, 31.60, 31.58, 31.48,
29.3, 25.7, 22.6, 14.1, 14.0, -0.1; MS (EI) (m/z) 632 (M+, 100%),
614 (M+ - 18, 21%). Anal. Calcd for C42H52O3Si: C, 79.70; H,
8.28. Found: C, 79.54; H, 8.25.
Compound 8. By analogy to the synthesis of 6, compound 7
(3.37 g), toluene (70 mL), and NaOH (1.75 g) were refluxed for 1
h to yield compound 8 as a pale-yellow solid (2.47 g, 77%, mp
54.6-56.6 °C) after column chromatography (silica gel, chloroform-
hexane, 3:2 v/v) and recrystallization from ethanol: 1H NMR (300
MHz, CDCl3) δ 7.61 (s, 4H), 7.60 (s, 4H), 7.01 (s, 1H), 7.00 (s,
1H), 6.98 (s, 1H), 6.96 (s, 1H), 4.01 (m, 8H), 3.35 (s, 1H), 1.84
(m, 8H), 1.54 (m, 8H), 1.36 (m, 16H), 0.90 (m, 12H), 0.27 (s, 9H);
13C NMR (75 Hz, CDCl3) δ 154.1, 153.5, 153.4, 140.05, 139.96,
132.06, 132.05, 126.8, 122.7, 122.6, 117.7, 117.2, 116.8, 114.5,
114.1, 113.7, 112.6, 101.1, 100.1, 94.8, 94.7, 86.9, 86.7, 82.3, 80.0,
69.6, 69.5, 69.4, 31.61, 31.58, 31.51, 29.3, 29.1, 25.7, 25.6, 22.63,
22.58, 14.07, 14.04, 14.02, -0.1; MS (ES+) (m/z) 874.5 (M+
-
14). Anal. Calcd for C60H76O4Si: C, 81.03; H, 8.61. Found: C,
80.89; H, 8.53.
Compound 9. By analogy to the synthesis of 5, compound 8
(2.47 g, 2.78 mmol), compound 2 (1.26 g, 3.48 mmol, 1.25 equiv),
TEA (100 mL), Pd[PPh3]2Cl2 (100 mg), and CuI (35 mg), at 80 °C
for 3 h gave a thick yellow suspension. Ethanol (100 mL) was
added, and a bright yellow solid was obtained by suction filtration.
The solid was column chromatographed (silica gel, DCM) and then
crystallized from chloroform-ethanol to afford 9 as an off-white
solid (2.61 g, 85%, mp 187.1-187.8 °C): 1H NMR (300 MHz,
CDCl3) δ 7.61 (m, 12H), 7.57 (d, J ) 8.2 Hz, 2H), 7.50 (d, J )
8.4 Hz, 2H), 7.05 (s, 2H), 6.99 (s, 1H), 6.96 (s, 1H), 3.98-4.08
(m, 8H), 2.08 (s, 1H), 1.85 (m, 8H), 1.65 (s, 6H), 1.56 (m, 8H),
1.37 (m, 16H), 0.91 (m, 12H), 0.27 (s, 9H); 13C NMR (75 Hz,
CDCl3) δ 154.1, 153.6, 153.5, 140.02, 139.97, 139.9, 132.1, 132.0,
126.8, 126.7, 122.7, 122.0, 117.2, 116.8, 116.7, 114.1, 114.0, 113.7,
101.1, 100.1, 94.78, 94.74, 94.70, 94.66, 87.0, 86.9, 81.9, 69.6,
69.5, 69.4, 65.7, 31.6, 31.5, 29.3, 25.74, 25.71, 25.69, 22.6, 14.07,
14.05, -0.1; HR MALDI-TOF (m/z) (M+) C76H88O5Si requires
1108.63955, found 1108.63971. Anal. Calcd for C76H88O5Si: C,
82.27; H, 7.99. Found: C, 82.08; H, 7.93.
Compound 10. By analogy to the synthesis of 8, compound 9
(2.61 g, 2.35 mmol), toluene (30 mL), and NaOH (1.20 g) were
refluxed for 1 h to give a product which was purified by column
chromatography (silica gel, DCM-hexane, 1:1 v/v) and crystal-
lization from chloroform-ethanol to afford 10 as an off-white solid
(2.46 g, 99%, mp 181.3-182.1 °C): 1H NMR (500 MHz, CDCl3)
δ 7.62-7.58 (m, 16H), 7.05 (s, 2H), 6.99 (s, 1H), 6.96 (s, 1H),
4.06 (t, J ) 6.5 Hz, 4H), 4.01 (m, 4H), 3.15 (s, 1H), 1.85 (m, 8H),
1.56 (m, 8H), 1.37 (m, 16H), 0.91 (m, 12H), 0.27 (s, 9H); 13C NMR
Compound 6. By analogy to the synthesis of 4, compound 5
(3.43 g), toluene 80 (mL), and NaOH (2.0 g) were refluxed for 1
h to afford 6 as off-white/pale-yellow crystals (2.88 g, 93%, mp
87.7-88.4 °C) after column chromatography (silica gel, chloroform-
hexane mixture, 3:2 v/v) and recrystallization from chloroform-
ethanol: 1H NMR (400 MHz, CDCl3) δ 7.6 (m, 8H), 6.98 (s, 1H),
6.96 (s, 1H), 4.01 (t, J ) 6.4 Hz, 2H), 3.99 (t, J ) 6.4 Hz, 2H),
3.15 (s, 1H), 1.82 (m, 4H), 1.55 (m, 4H), 1.35 (m, 8H), 0.90 (m,
114 J. Org. Chem., Vol. 71, No. 1, 2006

Synthesis of Aryleneethynylene Molecular Wires
(125 Hz, CDCl3) δ 154.2, 153.7, 153.5, 140.6, 140.0, 139.9, 132.6,
132.1, 126.88, 126.84, 126.82, 122.88, 122.74, 122.72, 121.3, 69.62,
69.56, 69.46, 31.61, 31.59, 29.32, 29.29, 25.75, 25.72, 25.70, 22.65,
22.64, 14.08, 14.06, -0.1; MALDI-TOF (m/z) 1050.6 (M+). Anal.
Calcd for C73H82O4Si: C, 83.38; H, 7.86. Found: C, 83.62; H,
7.93.
propanol) (10.5 mL) at room temperature, and the mixture was
stirred for 20 min. Solid di(4-pyridyl)ketone28 (1.93 g, 10.5 mmol)
was added in one portion to the resultant dark-red solution followed
by stirring at room temperature for 0.5 h and then at 50 °C for 1
h. Acetic acid (1 mL) was added to the dark-green suspension, and
the mixture was stirred for an additional 1 h. The yellow suspension
was cooled and then suction filtered to afford a yellow solid which
was crystallized from pyridine-ethanol to afford 15 as yellow
crystals (3.66 g, 63%, mp 316.2-317.8 °C): 1H NMR (CDCl3,
300 MHz) δ 6.92 (d, J13 ) 1.2 Hz, 2H), 7.28 (m, 4H), 7.38 (d, J12
) 8.1 Hz, 2H), 7.61 (dd, J12 ) 8.1 Hz, J13 ) 1.2 Hz, 2H), 8.76 (m,
4H); 13C NMR (CDCl3, 75 MHz) δ 92.4, 121.2, 123.7, 134.1, 134.2,
137.8, 138.6, 139.4, 140.2, 148.2, 150.9; MS (ES+) (m/z) 585 (M+
+ 1, 100%). Anal. Calcd for C24H14I2N2: C, 49.34; H, 2.42; N,
4.80. Found: C, 49.40; H, 2.39; N, 4.82.
Compound 11. Compound 1 (0.58 g, 1.19 mmol), Pd[PPh3]2-
Cl2 (30 mg), and CuI (10 mg) were dissolved in freshly distilled
piperidine (100 mL). A solution of compound 10 (0.63 g, 0.6 mmol)
in THF (10 mL) was added, and the mixture was stirred at 50 °C
for 36 h to obtain a clear yellow solution. Solvents were removed
by vacuum evaporation, and ethanol (50 mL) was added to the
residue. A yellow solid was collected by suction filtration, which
after column chromatography (silica gel, DCM) and crystallization
from chloroform-ethanol afforded 11 as a yellow solid (0.68 g,
80%, mp 179.0-180.1 °C): 1H NMR (300 MHz, CDCl3) δ 7.62
(s, 8H), 7.61 (s, 8H), 7.06 (s, 2H), 7.00 (s, 1H), 6.99 (s, 1H), 6.97
(s, 1H), 6.93 (s, 1H), 4.07-3.98 (m, 12H), 2.19 (s, br, 1H), 1.91-
1.79 (m, 12H), 1.65 (s, 6H), 1.60-1.50 (m, 12H), 1.37 (m, 24H),
0.92 (m, 18H), 0.28 (s, 9H); MALDI-TOF (m/z) 1409.9 (M+). Anal.
Calcd for C96H116O7Si: C, 81.77; H, 8.29. Found: C, 81.86; H,
8.32.
Compound 12. By analogy to the synthesis of 10, compound
11 (0.77 g, 0.543 mmol), toluene (40 mL), and NaOH (0.5 g) were
refluxed for 1.5 h to give a product which was purified by column
chromatography (silica gel, chloroform-hexane 85:15 v/v) and
crystallization from chloroform-ethanol to afford 12 as a pale-
yellow solid (0.71 g, 97%, mp 140.3-141.0 °C): 1H NMR (400
MHz, CDCl3) δ 7.632 (s, 8H), 7.628 (s, 4H), 7.622 (s, 4H), 7.07
(s, 2H), 7.03 (s, 1H), 7.00 (s, 2H), 6.98 (s, 1H), 4.08-4.00 (m,
12H), 3.36 (s, 1H), 1.85 (m, 12H), 1.56 (m, 12H), 1.36 (m, 24H),
0.92 (m, 18H), 0.28 (s, 9H); MALDI-TOF (m/z) 1351.7 (M+). Anal.
Calcd for C93H110O6Si: C, 82.62; H, 8.20. Found: C, 82.80; H,
8.25.
Compound 13. To the stirred mixture of 4-(2-cyanoethylsulfa-
nyl)iodobenzene14 (0.40 g, 1.38 mmol, 4 equiv), Pd[PPh3]2Cl2 (25
mg), CuI (10 mg), and TEA (20 mL) was added a solution of
compound 12 (0.47 g, 0.349 mmol) in THF (15 mL) at 50 °C. The
mixture was heated at 50 °C with stirring for 60 h to obtain a pale-
yellow suspension. Vacuum evaporation gave a residual solid.
Column chromatography (silica gel, chloroform then DCM) yielded
compound 13 as a yellow solid (0.44 g, 84%, mp 184.5-485.6
°C): 1H NMR (400 MHz, CDCl3) δ 7.62 (s, 14H), 7.61 (s, 2H),
7.50 (d, J ) 8.4 Hz, 2H), 7.37 (d, J ) 8.4 Hz, 2H), 7.05 (s, 2H),
7.04 (s, 1H), 7.02 (s, 1H), 6.99 (s, 1H), 6.96 (s, 1H), 4.08-3.98 (s,
12H), 3.17 (t, J ) 7.2 Hz, 2H), 2.63 (t, J ) 7.2 Hz, 2H), 1.86 (m,
12H), 1.57 (m, 12H), 1.37 (m, 24H), 0.91 (m, 18H), 0.27 (s, 9H);
MALDI-TOF (m/z) 1511.7 (M+). Anal. Calcd for C102H117NO6-
SSi: C, 80.96; H, 7.79; N, 0.93. Found: C, 81.22; H, 7.89; N,
0.80.
Compound 14. To a solution of compound 13 (0.28 g, 0.186
mmol) in THF (15 mL) was added K2CO3 powder (0.3 g), followed
by methanol (6 mL) dropwise. The resultant yellow suspension was
stirred at room temperature for 1 h. Solvents were removed in vacuo
and yellow solid residue was chromatographed (silica gel, chloro-
form then chloroform-DCM, 2:1 v/v) to afford 14 as a yellow
solid (0.17 g, 62%, mp 167.3-168.2 °C): 1H NMR (300 MHz,
CDCl3) δ 7.63 (s, 16H), 7.50 (d, J ) 8.4 Hz, 2H), 7.36 (d, J ) 8.4
Hz, 2H), 7.06 (s, 2H), 7.05 (s, 1H), 7.03 (s, 2H), 7.00 (s, 1H),
4.08-3.99 (m, 12H), 3.37 (s, 1H), 3.15 (t, J ) 7.2 Hz, 2H), 2.62
(t, J ) 7.2 Hz, 2H), 1.86 (m, 12H), 1.56 (m, 12H), 1.38 (m, 24H),
0.92 (m, 18H); MALDI-TOF (m/z) 1440.8 (M+). Anal. Calcd for
C99H109NO6S: C, 82.52; H, 7.62; N, 0.97. Found: C, 82.02; H,
7.53; N, 0.83.
Compounds 16 and 17. By analogy to the synthesis of 13, the
solution of compound 14 (53 mg, 0.037 mmol) in THF was added
to the stirred solution of 15 (10 mg, 0.017 mmol), Pd[PPh3]2Cl2 (2
mg), CuI (1 mg), and piperidine (10 mL) at 50 °C. The reaction
mixture was stirred for 50 h at 50 °C followed by a vacuum
evaporation. Ethanol (50 mL) was added to the dark-yellow solid
residue, and the mixture was boiled for 5 min and then cooled to
room temperature, followed by a suction filtration to give a yellow
solid. Preparative thin-layer chromatography (silica gel, chloroform-
diethyl ether, 4:1 v/v) gave compound 16 as a yellow solid (14
mg, 27%, mp 202.0-205.0 °C, Rf ) 0.84) followed by 17 as an
orange-yellow solid (11 mg, 18%, mp 195.3-197 °C, Rf ) 0.42).
16: 1H NMR (500 MHz, CDCl3) δ 8.79 (s, 2H), 7.67 (d, J )
7.5 Hz, 1H), 7.62 (s, 16H), 7.53 (d, J ) 8 Hz, 1H), 7.50 (d, J )
8.0 Hz, 2H), 7.42 (s, 2H), 7.37 (d, J ) 8.5 Hz), 7.05 (s, 2H), 7.04
(s, 1H), 7.02 (s, 1H), 7.01 (s, 1H), 6.93 (s, 1H), 6.84 (s, 1H), 4.06
(m, 12H), 3.18 (t, J ) 7.5 Hz, 2H), 2.64 (t, J ) 7.3 Hz, 2H), 1.87
(m, 12H), 1.57 (m, 12H), 1.38 (m, 24H), 0.91 (m, 18H); MALDI-
TOF (m/z) 3210.1 (M+). Anal. Calcd for C222H230N4O12S2: C,
83.06; H, 7.22; N, 1.75. Found: C, 82.14; H, 7.24; N, 1.50.
1
17: H NMR (300 MHz, CDCl3) δ 7.62 (s, 16H), 7.50 (d, J )
8.4 Hz, 2H), 7.37 (d, J ) 8.4 Hz, 2H), 7.05 (s, 2H), 7.04 (s, 1H),
7.02 (s, 2H), 7.01 (s, 1H), 4.05 (m, 12H), 3.17 (t, J ) 7.1 Hz, 2H),
2.63 (t, J ) 7.2 Hz, 2H), 1.86 (m, 12H), 1.56 (m, 12H), 1.38 (m,
24H), 0.91 (m, 18H); MALDI-TOF (m/z) 2878.4 (M+). Anal. Calcd
for C198H216N2O12S2: C, 82.57; H, 7.56; N, 0.97. Found: C, 82.08;
H, 7.53; N, 0.94.
2,5-Dihexyloxy-4-(3-hydroxy-3-methylbutynyl)phenylacet-
ylene (18). Compound 3 (4.32 g, 9.46 mmol) was dissolved in a
mixture of DCM and methanol (50 mL, 1:1 v/v). Powdered K2-
CO3 (2.0 g) was added, and the mixture was stirred at room
temperature for 3 h. The solid was removed by suction filtration
through Celite, and the filtrate was evaporated to dryness. The
crystalline yellow solid was chromatographed on a silica gel column
(eluent DCM-diethyl ether, 98:2 v/v) to yield 18 as pale-yellow
crystals (3.49 g, 96%, mp 42.0-43.8 °C): 1H NMR (400 MHz,
CDCl3) δ 6.92 (s, 1H), 6.87 (s, 1H), 3.95 (m, 4H), 3.32 (s, 1H),
2.19 (s, 1H), 1.78 (m, 4H), 1.62 (s, 6H), 1.47 (m, 4H), 1.33 (m,
8H), 0.90 (m, 6H); 13C NMR (100 Hz, CDCl3) δ 154.1, 153.5,
117.7, 117.1, 114.0, 112.6, 99.3, 82.1, 79.9, 78.3, 69.6, 69.5, 65.7,
31.6, 31.5, 31.4, 29.3, 29.1, 25.7, 25.6, 22.6, 22.5, 14.00, 13.97;
MS (ES+) m/z 407.3 (M+ + 23, 100%). Anal. Calcd for
C25H36O3: C, 78.08; H, 9.44. Found: C, 78.28; H, 9.53.
Compound 19. The mixture of 18 (1.27 g, 3.29 mmol), 2,7-
diiodo-9-fluorenone29 (0.70 g, 1.62 mmol), Pd[PPh3]2Cl2 (120 mg),
CuI (40 mg), THF (25 mL), and TEA (25 mL) was stirred at room
temperature for 3 h and then at 50 °C for 4.5 h to afford an orange
suspension. The liquids were removed by vacuum evaporation, and
2,7-Diiodo-9-[di(4-pyridyl)methylene]fluorene 15. To the solu-
tion of 2,7-diiodofluorene27 (4.18 g, 10 mmol) in dry THF (50 mL)
was added potassium tert-butoxide (1.0 M solution in 2-methyl-
(28) Di(4-pyridyl)ketone was synthesized in 60% yield using a modifica-
tion of the reported method: Minn, F. L.; Trichilo, C. L.; Hurt, C. R.;
Filipescu, N. J. Am. Chem. Soc. 1970, 92, 3600.
(29) Merkushev, E. B.; Simakhina, N. D.; Koveshnikova, G. M. Synthesis
1980, 486.
(27) Okumoto, K.; Shirota, Y. Chem. Mater. 2003, 15, 699.
J. Org. Chem, Vol. 71, No. 1, 2006 115

Wang et al.
diethyl ether (100 mL) was added to the solid residue. The mixture
was sonicated, followed by suction filtration through Celite. The
filtrate was evaporated to dryness, and the residual solid was column
chromatographed (silica gel, DCM-diethyl ether, 9:1 v/v) to afford
19 as an orange solid (1.41 g, 92%, mp 129.8-131.1 °C): 1H NMR
at 1.5 × 10-2 mbar for 24 h). A single crystal for X-ray analysis
was grown by slow evaporation of its deuterated chloroform-
1
ethanol solution: H NMR (300 MHz, CDCl3) δ 7.77 (s, 1H), 7.63-
7.44 (m, 10H), 7.01 (s, 1H), 6.99 (s, 1H), 4.03 (t, J ) 6.5 Hz, 4H),
2.23 (s, 1H), 1.87 (m, 4H), 1.64 (s, 6H), 1.57 (m, 4H), 1.38 (m,
8H), 0.93 (m, 6H); 13C NMR (100 MHz, CDCl3) δ 192.1, 153.8,
153.7, 143.2, 140.01, 139.96, 137.7, 134.5, 132.13, 132.06, 127.3,
126.8, 126.7, 124.7, 122.7, 122.0, 120.5, 116.9, 116.8, 114.4, 113.5,
95.0, 94.7, 94.1, 88.3, 87.0, 81.9, 69.7, 69.6, 65.7, 31.61, 31.58,
31.49, 29.33, 29.30, 25.76, 25.74, 22.65, 22.63, 14.03; MALDI-
TOF MS m/z 1297.7 (M+). Anal. Calcd for C91H92O7: C, 84.22;
H, 7.15. Found: C, 84.26; H, 7.03.
Compound 22. By analogy to the synthesis of 20, compound
21 (0.45 g, 0.35 mmol), toluene (40 mL), and NaOH (0.2 g) were
refluxed for 5 h to yield 22 as orange crystals (0.38 g, 92%, mp
166.8-168.2 °C) after column chromatography (silica gel, chloro-
form-petroleum ether bp 40-60 °C, 4:1 v/v) and recrystallization
from chloroform-ethanol: 1H NMR (400 MHz, CDCl3) δ 7.79
(s, 1H), 7.63 (d, J ) 7.5 Hz, 1H), 7.59 (m, 8H), 7.48 (d, J ) 7.8
Hz, 1H), 7.02 (s, 1H), 7.01 (s, 1H), 4.04 (t, J ) 6.3 Hz, 4H), 3.15
(s, 1H), 1.87 (m, 4H), 1.57 (m, 4H), 1.38 (m, 8H), 0.93 (m, 6H);
13C NMR (75 MHz, CDCl3) δ 192.1, 153.69, 153.59, 143.1, 140.56,
139.8, 137.7, 134.4, 132.6, 132.1, 127.2, 126.84, 126.79, 124.6,
122.8, 121.3, 120.5, 116.8, 116.7, 114.3, 113.4, 94.9, 94.1, 88.2,
87.0, 83.4, 78.1, 69.6, 69.5, 31.61, 31.58, 29.30, 29.27, 25.74, 22.7,
22.6, 14.1; MALDI-TOF MS m/z 1180.7 (M+). Anal. Calcd for
C85H80O5: C, 86.40; H, 6.82. Found: C, 86.36; H, 6.78.
(300 MHz, CDCl3) δ 7.75 (d, J13 ) 1.5 Hz, 1H), 7.60 (dd, J12
)
7.8 Hz, J13 ) 1.5 Hz, 1H), 7.47 (d, J12 ) 7.8 Hz, 1H), 6.92 (s,
1H), 6.88 (s, 1H), 3.97 (m, 4H), 2.39 (s, 1H), 1.81 (m, 4H), 1.63
(s, 6H), 1.53 (m, 4H), 1.35 (m, 8H), 0.90 (m, 6H); 13C NMR (75
MHz, CDCl3) δ 192.1, 153.6, 153.5, 143.1, 137.7, 134.4, 127.2,
124.6, 120.4, 116.8, 116.6, 113.7, 113.2, 99.5, 93.8, 88.1, 78.4,
69.5, 69.4, 65.7, 31.6, 31.5, 31.4, 29.25, 29.23, 25.71, 25.68, 22.62,
14.0. Anal. Calcd for C63H76O7: C, 80.05; H, 8.10. Found: C,
79.79; H, 7.98.
Compound 20. By analogy to the synthesis of 6, a mixture of
18 (1.00 g, 1.06 mmol), toluene (40 mL), and NaOH (0.2 g) was
refluxed for 50 min to yield compound 20 as a pale-yellow solid
(0.84 g, 96%, mp 100.6-101.6 °C), which was purified by column
chromatography (silica gel, DCM-petroleum ether, bp 40-60 °C,
2:1 v/v) and recrystallization from ethanol: 1H NMR (400 MHz,
CDCl3) δ 7.79 (d, J13 ) 1.2 Hz, 1H), 7.64 (dd, J12 ) 6.0 Hz, J13
) 1.2 Hz, 1H), 7.49 (d, J12 ) 6.0 Hz, 1H), 6.983 (s, 1H), 6.975 (s,
1H), 4.00 (m, 4H), 3.36 (s, 1H), 1.85 (m, 4H), 1.52 (m, 4H), 1.36
(m, 8H), 0.91 (m, 6H); 13C NMR (75 MHz, CDCl3) δ 192.1, 154.1,
153.6, 143.2, 137.7, 134.5, 127.3, 124.6, 120.5, 117.7, 116.9, 114.0,
113.1, 94.0, 87.9, 82.5, 79.9, 69.7, 69.6, 31.55, 31.51, 29.2, 29.1,
25.7, 25.6, 22.62, 22.56, 13.99, 13.98; HR MALDI-TOF MS (m/z)
C57H64O5 requires 828.47483, found 828.47394. Anal. Calcd for
C57H64O5: C, 82.57; H, 7.78. Found: C, 82.80; H, 7.83.
Acknowledgment. We thank EPSRC and QinetiQ for
Compound 21. By analogy to the synthesis of compound 5, a
mixture of compound 2 (0.40 g, 1.01 mmol), compound 19 (0.42
g, 0.5 mmol), Pd[PPh3]2Cl2 (40 mg), CuI (15 mg), THF (5 mL),
and TEA (25 mL) was stirred at room temperature for 2 h and at
55 °C for 3 h. Purification by column chromatography (silica gel,
DCM-diethyl ether, 9:1 v/v) and recrystallization from chloroform-
ethanol gave 21 as orange crystals (0.42 g, 64%, mp 207.5-208.6
°C, the sample for elemental analysis was dried under high vacuum
funding this work.
Supporting Information Available: X-ray crystallographic file
for 21 in CIF format and a discussion of the optical data presented
in Table 1. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO051711O
116 J. Org. Chem., Vol. 71, No. 1, 2006