Synthesis and testing of new end-functionalized oligomers for molecular electronics

Article abstract of DOI:10.1016/j.tet.2003.09.004

Several new classes of oligomers have been synthesized with functionalities designed to aid in the understanding of molecular device behavior, specifically when molecules are interfaced between proximal electronic probes. The compounds synthesized are series of azobenzenes, bipyridines and oligo(phenylene vinylene)s that bear acetyl-protected thiols for ultimate attachment to metallic surfaces. Some initial electrochemical and solid-state test results are also reported.

Full text of DOI:10.1016/j.tet.2003.09.004

Tetrahedron 59 (2003) 8555–8570
Synthesis and testing of new end-functionalized oligomers
for molecular electronics
Austen K. Flatt,a Shawn M. Dirk,a Jay C. Henderson,a Dwanleen E. Shen,a Jie Su,b
a
Mark A. Reedb and James M. Tour
,
,
*
*
aDepartment of Chemistry and Center for Nanoscale Science and Technology, Rice University, 6100 Main Street,
MS-222, Houston, TX 77005, USA
bDepartments of Electrical Engineering, Applied Physics, and Physics, Yale University, P.O. Box 208284, New Haven, CT 06520, USA
Received 8 May 2003; revised 4 September 2003; accepted 4 September 2003
Abstract—Several new classes of oligomers have been synthesized with functionalities designed to aid in the understanding of molecular
device behavior, specifically when molecules are interfaced between proximal electronic probes. The compounds synthesized are series of
azobenzenes, bipyridines and oligo(phenylene vinylene)s that bear acetyl-protected thiols for ultimate attachment to metallic surfaces. Some
initial electrochemical and solid-state test results are also reported.
q 2003 Elsevier Ltd. All rights reserved.
1. Introduction
the electron deficient nature of pyridyl oligomers, and the
high electrical transport seen in OPVs,10 these molecules are
good candidates to study device behavior.
Due to physical and economic constraints, silicon based
semiconductor technology is rapidly nearing a production
brick wall.1 As the miniaturization of solid-state silicon
circuitry continues in order to increase speed, capacity and
computing power, a point will be reached at which
processors can no longer be made smaller, faster and
cheaper. It has been proposed that by incorporating organic
molecules into functioning molecular circuits, one may
overcome many of the challenges that complimentary
metal-oxide semiconductor (CMOS) technology is facing.2
Work performed in the molecular electronics field has
demonstrated that single molecules exhibit reversible
switching behavior, which may lead researchers to molecu-
lar memory and logic devices.3–5 Our research has centered
around oligo(phenylene ethynylene)s (OPEs) which, with
the redox active nitro group, have demonstrated negative
differential resistance (NDR) at variable temperatures.2
In addition to these syntheses, we performed electro-
chemical testing of selected compounds, a method found
to be useful for qualitative comparisons of molecular
electronic devices.11 We also include some results obtained
from planar test devices using the bipyridyl compounds
which show a resetable on-off state and NDR behavior.
2. Azobenzenes
It has been shown that OPEs containing a redox active
aromatic nitro functionality exhibit NDR at various
temperatures.3 The proposed mechanism is that the redox
center contributes to the switching behavior of the
mononitro OPE.12 However, other theories have recently
been put forth for NDR behavior including molecule/metal-
based contact variations that could result in NDR-like
performance.13,14 By incorporating an azo functionality into
an OPE, an additional redox center is created where
switching behavior is likely to be observed.
Several new classes of potential molecular electronics
molecules have been synthesized in our laboratory in order
to develop further understanding of the switching pro-
cess.6–9 In this paper, we will discuss our synthetic work
on azobenzene derivatives, pyridine systems, and oligo-
(phenylene vinylene)s (OPVs) that have been synthesized as
possible device candidates and that all bear protected thiol
end groups for self-assembled attachment to metallic
probes. Due to the additional redox center of azobenzenes,
In addition to the redox active site, azobenzenes are known
to change between the E and Z configurations when
irradiated with light, giving rise to other probable switching
mechanisms,15 although we are not exploiting that manifold
here.
Keywords: oligomers; molecular electronics.
*
Corresponding authors. Tel.: þ1-713-348-6246; fax: þ1-713-348-6250;
e-mail: tour@rice.edu
The azobenzene derivatives synthesized are shown in
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.09.004

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A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
As shown in Scheme 2, coupling 5 with 4-ethynyl-1-
thioacetylbenzene17 afforded the expected dicoupled pro-
duct 2. Since our experiments have shown that compounds
without thioacetyl (‘alligator clips’ for adhesion to metallic
surfaces after acetyl removal) produced cleaner electro-
chemical results that are still quantitatively similar to the
sulfur-bearing systems,11 we made 6 by coupling phenyl-
acetylene to 5 under the same conditions as those used to
make 2. It is important to note that in both of these coupling
reactions, none of the hydrazo product was obtained.
Figure 2 shows the cyclic voltamagram (CV) of 6. It is
evident from the data that the azo linkage contains an
additional redox center compared to the unfunctionalized
OPE (vide infra). From Figure 2, there are two clear
reduction peaks at 21.3 and 22.1 V as well as smaller
features at 21.4 and 21.8 V. The reductions are reasonably
reversible. However, because oxygen and water were not
rigorously excluded, this data was used, as we have done
in our prior work, only for comparison between molecules
and to make relative assessments regarding solid-state
behavior.
Figure 1. Azobenzene derivatized compounds 1–3 and hydrazo compound
4.
Figure 1 as compounds 1–3 as well as the hydrazo
compound 4.
Compound 1 was synthesized from p-iodoaniline as shown
in Scheme 1. Oxidizing p-iodoaniline using potassium
permanganate and copper(II) sulfate afforded 5 in a lower
than expect yield.16 Attempts to replace the diiodide using
tert-butyllithium at 2788C, followed by adding sulfur and
quenching with acetyl chloride were met with no success.
However, using n-butyllithium, 1 was afforded, albeit in low
yield.
Figure 2. CV of compound 6.
Compounds 3 and 4 were synthesized from 2-nitro-4-
iodoaniline as shown in Scheme 3. 2-Nitro-4-iodoaniline
was oxidatively coupled using mercury(II) oxide and
iodine18 to afford the azo derivative 7, exclusively as the
E isomer, in low yield. This poor yield is presumably due to
the low reactivity of the electron deficient aniline and the
stericly hindered azo product. 7 was then subjected to
palladium-catalyzed coupling with 4-ethynyl-1-thioacetyl-
benzene to yield both the azo compound 3, and the hydrazo
product 4.
Scheme 1. Synthesis of substituted azobenzene 1.
Figure 3 shows the CV of the dinitro azo compound 3 with
multiple reduction peaks at 21.3, 22.0 and 22.3 V and a
small peak at 21.8 V. We are currently awaiting solid-state
testing of these compounds in order to assess their
applicability for molecular electronics.
3. Pyridyl devices
Scheme 2. Synthesis of compounds 2 and 6.
By replacing the phenyl8 or biphenyl9 core of the OPE

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8557
Scheme 3. Synthesis of compounds 3 and 4.
the bipyridyl system would be present. Molecular modeling
(AM1 theory) indicates a reduction of the dihedral angle
from 45.58 for the 2-20-dinitro-biphenyl system to 35.18 for
the 2-20-dinitro-bipyridyl system. This will ultimately
increase the overlap of the extended p-orbitals, lowering
the resistance through the molecule. The pyridyl based
systems synthesized are shown in Figure 4.
Scheme 4 shows the synthesis of the target compound 8 with
two thioacetates. The dinitro-bipyridyl compound 11 was
obtained by an Ullmann20 coupling of commercially
available 2-chloro-3-nitropyridine.21 11 was brominated
under harsh conditions, presumably necessary due to the
electron deficient nature of the system,22 to afford 12. 12
was coupled with trimethylsilylacetylene in fair yield to
afford the dicoupled product 13. Deprotection of the
terminal alkynes was accomplished using potassium
carbonate and the resulting bis-alkyne was then coupled
with 4-(thioacetyl)iodobenzene23 to afford the target 8. Also
shown in Scheme 4 is the synthesis of the unfunctionalized
compound 14 (for CV) accomplished by coupling inter-
mediate 12 with phenylacetylene.
Figure 3. CV of the dinitro azo compound 3.
molecule with one or two pyridine moieties, we surmise that
the LUMO will be lowered, producing a better match with
the Fermi level of the metal contact and higher current
through the device.12,19 In addition, due to the absence of
the 2- and 20-steric interactions, less inter-ring twisting in
Scheme 5 shows the synthesis of the dinitro-bipyridyl
compound 9 with one thioacetate. Intermediate 12 was first
coupled to trimethylsilylacetylene to afford 15 and then
coupled to phenylacetylene to yield 16. 16 was then
deprotected with potassium carbonate and coupled to
4-(thioacetyl)iodobenzene to afford the target compound
9. The solid-state test results of compounds 8 and 9 are
discussed later in this paper.
Scheme 6 shows the synthesis of the 30-nitro-pyridine
molecule 10. 2-Amino-5-bromopyridine was nitrated to
give the mononitro compound 17.24 17 was converted to the
dibromo compound 18,25 coupled with phenylacetylene,
trimethylsilylacetylene, deprotected and finally coupled
with 4-(thioacetyl)iodobenzene to afford 10.
4. Oligo(phenylene vinylene)s
Figure 4. Pyridyl based targets 8–10.
In an attempt to design more efficient molecular devices

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Scheme 4. Synthesis of the dithioacetate dinitro-bipyridyl 8 and the unfunctionalized derivative 14.
(lower impedance, larger ON:OFF ratios and longer
electronic hold times), several features need to be
optimized. In order to achieve the highest efficiency in
terms of energy used, transport needs to be maximized
across a molecular device. To date, most of our research has
focused on OPE-based devices.1,2 Recent work by Chidsey
et al.10 has shown that electrical transport is higher through
OPVs than through OPEs. Similar results, both theoretically
and experimentally, have been obtained by Shashidhar
et al.26 To study OPVs in a molecular electronic device,
three new OPVs were synthesized as shown in Figure 5.
Initially 4-vinylphenyl thioacetate (25) was chosen as the
group to carry the alligator clip. 25 was previously
Scheme 5. Synthesis of the monothioacetate dinitro-bipyridyl compound 9.

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8559
Scheme 6. Synthesis of the mononitro-monothioacetate pyridine compound 10.
Initial attempts to synthesize 21 resulted in the
formation of arylthioether 29 as shown in Scheme 8.
The attempted synthesis of 21 began with a Heck30
coupling of 4-iodo-2-nitroaniline with styrene to produce
2-nitro-4-styrylaniline. Diazotization of 26 produced 27
in high yield, which was then halogenated with I2 and
NaI to afford 28. Disappointingly, the Heck coupling of
28 with 25 yielded no desired product and instead formed
29.
In an effort to avoid the sulfur deprotection and thioether
formation, 24 was coupled to 28 to form 30 in excellent
yield as shown in Scheme 9. However, 30 was not reactive
under the Heck conditions to form the desired 21.
Figure 5. OPV based potential devices.
In order to overcome the problems with the acetyl-
protecting group, the ethyltrimethylsilyl group was used t0o
protect the sulfur. Coupling of 2-(trimethylsilyl)ethyl-4 -
bromophenyl sulfide31 directly with 24 did not afford the
desired compound, and in fact only resulted in recovery of
starting material. This may be due to the fact that the aryl
bromide is electron rich and slow to couple with the
stannane under Stille conditions. With this in mind, the aryl
bromide was converted to an aryl iodide by lithiating and
quenching with diiodoethane to form 31.31 Coupling 31
synthesized by Overberger and Lebovits,27 however, their
synthesis required extreme temperatures in excess of 4608C.
Our route, in Scheme 7, is higher yielding and more easily
accessed.
The synthesis of 25 began by refluxing vinyl magnesium
bromide with tributyltin chloride to produce the vinyl
stannane 24.28 A subsequent Stille29 coupling produced 25.
Scheme 7. Synthesis of alligator clip 25.

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Scheme 8. Attempted synthesis of 21.
with 24 resulted in the formation of the desired alligator clip
32 in high yield as shown in Scheme 10.
Compound 33 was synthesized by coupling 28 with 32
under Heck conditions as shown in Scheme 11.
In order to examine the effects of a nitro group in the OPV
system, an unfunctionalized wire was synthesized. The
synthesis of 22 began by coupling 4-bromoiodobenzene
with styrene to produce 34 as shown in Scheme 12.
Scheme 9. Attempted synthesis of 21 from 28.
Scheme 10. The synthesis of alligator clip 32.
Scheme 11. Synthesis of compound 33.
Scheme 12. Synthesis of compound 35.

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8561
Scheme 13. Synthesis of compound 36.
Scheme 14. Deprotection of the ethyltrimethylsilyl groups to afford 21, 22 and 23.
Compound 34 was then coupled with 32 to afford 35 in high
yield.
corresponding oxidations.11 We note the first reduction
potentials of the unsubstituted and mononitro OPVs and
OPEs are not significantly different, suggesting the LUMO
of the mononitro compound was not lowered. However,
previous calculations have shown the LUMO differences to
be quite significant in non-electrolytic media, resulting in
proposals for the observed switching behavior in solid-state
systems.12
The mononitro OPV containing two alligator clips, 23, was
synthesized by dicoupling 2,5-dibromonitrobenzene with 32
under Heck conditions to afford the desired compound 36 as
shown in Scheme 13.
With the completed ethyltrimethylsilyl-protected com-
pounds in hand, initial assembly experiments using in situ
deprotection failed to form adequate self-assembled mono-
layers (SAMs). It was determined that the acetyl precursor
was preferred for the in situ deprotection and assembly.
Replacement of the ethyltrimethylsilyl group with the acetyl
group was accomplished using 10 equiv. of TBAF for
deprotection followed by the addition of 20 equiv. of acetyl
chloride,31 thereby affording the desired acetyl protected
compounds 21, 22 and 23 as shown in Scheme 14.
The CV differences between the OPVs (Fig. 6(a) and (b))
and their corresponding OPEs (Fig. 6(c) and (d)) are subtle
enough that one would expect similar behaviors in device
embodiments. This subtle difference was unexpected based
on reports.10,26,32–36 Therefore, we await solid-state testing
in order to definitively evaluate the differences between the
OPVs and their corresponding OPEs.37
5. Planar testbed results
The CVs of compounds 21 and 22 were compared to the
CVs of the corresponding OPEs which have been shown to
have NDR behavior if mononitro-substituted.11 As shown in
Figure 6, both the unfunctionalized OPVs and the OPEs
(Fig. 6(a) and (c), respectively) have first reduction
potentials at 21.2 V and another small reduction feature
at 22.3 V. However, nitro-containing OPVs and OPEs
(Fig. 6(b) and (d), respectively), as observed for compound
3, show multiple reduction events due to the nitro group
being able to undergo further electron reduction and
Compounds 8 and 9 have been tested for device behavior
using the planar device testbed wherein a SAM of the
compound is made on a lithographically patterned Au
substrate followed by Au evaporation atop the SAM
structure.3,4,11 The device size can range from 1 to 5 mm2.
As shown in Figure 7, compound 8 exhibited reproducible
NDR in both sweep directions at room temperature.
Previously, NDR had been reported only in the positive
direction (in the negative sweep direction, the NDR was far

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A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
Figure 6. Cyclic voltametry results for OPVs 21 (a) and 22 (b) and their corresponding OPEs (c) and (d), respectively.
less pronounced) for the mononitro OPE device and sharp
voltage peaks were only seen at low temperatures.3
returned to the system. The ‘resetablility’ of the dinitro-
bipyridyl system is similar to the device behavior observed
with the mononitro OPE, where after an applied negative
voltage pulse, NDR returns to the system.4
A device built from compound 9 also exhibited reproducible
NDR in the testbed as well as a resetable state as shown in
Figure 8. The first voltage sweep reveals NDR in the
positive direction at a peak voltage of 1.5 V and a peak
current of ,50 pA. However, the NDR peak weakens
noticeably upon subsequent voltage sweeps in the range of
0–2.5 V. After an applied negative voltage pulse, the NDR
returns to the original peak current and device behavior is
6. Summary
Several new classes of oligomers have been synthesized
bearing functionalities to interface between proximal
electronic probes for molecular electronics studies. The
Figure 8. A resetable state is observed for a device built from 9. After the
first sweep, the current is reduced dramatically as seen in voltage sweeps
2–8. Following the 8th sweep, a negative voltage pulse of ,2.5 V (not
shown) is given to restore NDR to the device, as seen in the 9th voltage
sweep. T¼300 K.
Figure 7. Positive and negative NDR in the dinitro-bipyridyl device built
from 8. T¼300 K.

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8563
compounds synthesized were series of azobenzenes,
bipyridines and oligo(phenylene vinylene)s. Some initial
electrochemical results point to electrical similarities
between these oligomers and previously prepared OPEs.
Initial solid-state test results are also reported for the new
class of bipyridines which show encouraging resetable NDR
behavior at room temperature.
in an oil bath while stirring. Upon cooling, all solvents were
removed in vacuo.
7.5. General Heck coupling procedure30
To an oven dried glass screwcap tube or round-bottom flask
all solids including the aryl halide (bromide or iodide),
alkene, base (if solid), and palladium(II) acetate catalyst
were added. The atmosphere was removed via vacuum and
replaced with dry N2 (3£). Solvent and remaining liquids
were added and the reaction was heated in an oil bath while
stirring. Upon cooling, the reaction was quenched with the
addition of water. The reaction mixture was extracted with a
suitable organic solvent (3£). The organic layer was dried
with MgSO4 and filtered. The solvent was then removed in
vacuo.
7. Experimental
7.1. General
All reactions were performed under an atmosphere of N2
unless otherwise stated. Tetrahydrofuran (THF) was
distilled from sodium benzophenone ketyl. Hexanes were
distilled. Triethylamine (TEA), diisopropylethylamine
(DIEA) and CH2Cl2 were distilled from CaH2 under N2.
Silica gel plates were 250 mm thick, 40 F254 grade obtained
from EM Science. Silica gel was grade 60 (230–400 mesh)
from EM Science. Mass spectrometry was performed at
Rice University’s Mass Spectrometry lab. All new com-
pounds were named using the Beilstein Autonom feature.
7.6. General procedure for the deprotection of
trimethylsilyl protected alkynes39
To a round-bottom flask equipped with a stir bar were added
the protected alkyne, K2CO3 (5 equiv. per protected
alkyne), methanol, and CH2Cl2. The reaction was stirred,
and upon completion, the reaction mixture was diluted with
CH2Cl2 and washed with brine (3£). The organic layer was
dried over MgSO4, and the solvent removed in vacuo.
7.2. General procedure for electrochemical testing of
compounds
7.7. General procedure for the diazotization of anilines
with nitrosonium tetrafluoroborate in the acetonitrile–
sulfolane system40
The CVs were performed on a BAS CV-50W using a glassy
carbon electrode as the working electrode, platinum wire as
the auxiliary electrode, and a Ag/AgNO3 non-aqueous
reference electrode. The solutions were 1 mM in DMF and
0.1 M in n-Bu4NBF4. The scan rate was 0.1 V/s at 238C.
Oxygen and water were not rigorously excluded from the
vessels.
NOBF439 was weighed out in a N2-filled dry box and placed
in a round-bottom flask equipped with a magnetic stirring
bar and sealed with a septum. Acetonitrile and sulfolane
were injected in a 5 to 1 volume ratio and the resulting
suspension was cooled in a dry ice/acetone bath to 2408C.
The solution of the aniline was prepared by adding warm
sulfolane (45–508C) to the amine under a N2 blanket,
sonication for 1 min and subsequent addition of acetonitrile
(10–20% by volume). The aniline solution was then added
to the nitrosonium salt suspension over a period of 10 min.
The reaction mixture was kept at 2408C for 30 min and was
then allowed to warm to the room temperature. At this point,
the diazonium salt was precipitated by the addition of ether
or CH2Cl2, collected by filtration, washed with ether or
CH2Cl2 and dried. Additional purification of the salt was
accomplished by re-precipitation from DMSO by CH2Cl2
and/or ether addition.
7.3. General procedure for coupling a terminal alkyne
with an aryl halide (Castro–Stephens/Sonogashira
protocol)38
To an oven dried screw cap tube with a magnetic stir bar
were added the aryl halide, bis(triphenylphosphine)palla-
dium(II) dichloride (5 mol% based on aryl halide), and
copper(I) iodide (10 mol% based on aryl halide). The vessel
was then sealed with a rubber septum, evacuated and
backfilled with N2 (3£). A cosolvent of THF was added
followed by the amine. The terminal alkyne was then added
and the reaction was heated, if necessary, until the aryl
halide was consumed as judged by TLC. The reaction vessel
was cooled to room temperature and quenched with water.
The organic layer was diluted with CH2Cl2 and washed with
a saturated solution of NH4Cl. The organic layer was
dried using anhydrous MgSO4 and the solvent was removed
in vacuo. The crude product was then purified by flash
chromatography (silica gel).
7.7.1. Thioacetic acid S-[4-(4-acetylsulfanyl-phenylazo)-
phenyl] ester (1). To a 100 mL round-bottom flask
was added bis-(4-iodo-phenyl)-diazene (5)16 (0.50 g,
1.15 mmol). THF (50 mL) was added and the solution
cooled to 2788C. n-Butyllithium (1.04 mL of a 2.21 M
solution in hexanes) was added dropwise. The mixture was
kept at 2788C and stirred for 45 min. With a strong backfill
of N2, the septum was removed, sulfur powder (0.078 g,
2.419 mmol) was quickly added, and the septum replaced.
The reaction mixture was warmed to 08C and stirred for
10 min. The mixture was recooled to 2788C and acetyl
chloride (0.20 mL, 2.76 mmol) was added. The solution was
allowed to warm to room temperature overnight and the
next day it was poured into H2O (100 mL) and extracted
7.4. General Stille coupling reaction procedure29
To an oven dried screwcap tube or round-bottom flask, all
solids including the aryl halide (bromide or iodide), and
palladium catalyst were added. The atmosphere was
removed via vacuum and replaced with dry N2 (3£). THF
and tin compounds were added and the reaction was heated

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A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
with CH2Cl2 (3£). The organic extracts were combined,
washed with brine, dried over anhydrous MgSO4, and the
solvent was removed in vacuo. Flash chromatography, silica
gel (CH2Cl2) afforded the product (0.025 g, 7%). Mp: 162–
1648C. IR (KBr) 3018.9, 1698.9, 1215.3, 1115.9, 756.7,
1715.0, 1528.9, 1426.4, 1215.5, 929.0, 769.9, 667.8 cm21
.
1H NMR (400 MHz, CDCl3) d 9.34 (s, 2H), 8.45 (d, J¼
2.4 Hz, 2H), 7.64 (dd, J¼9.0, 2.4 Hz, 2H), 7.54 (d, J¼
9.4 Hz, 4H), 7.42 (d, J¼9.4 Hz, 4H), 7.19 (d, J¼9.4 Hz,
2H), 2.45 (s, 6H). 13C NMR (100 MHz, CDCl3) d 193.8,
144.8, 139.7, 134.7, 133.0, 132.5, 130.3, 128.9, 124.2,
114.8, 114.7, 89.5, 88.9, 30.7. HRMS calcd for
C32H23N4O6S2: 623.1059. Found: 623.1054.
1
667.4 cm21. H NMR (400 MHz, CDCl3) d 7.97 (d, J¼
8.8 Hz, 4H), 7.59 (d, J¼8.8 Hz, 4H), 2.48 (s, 6H). 13C NMR
(100 MHz, CDCl3) d 193.6, 153.0, 135.4, 131.8, 124.0,
30.8. HRMS calcd for C16H14N2O2S2: 330.0496. Found:
330.0495.
7.7.5. Bis-(4-iodo-phenyl)-diazene (5).16 Potassium per-
manganate (7.50 g, 86.3 mmol) and copper(II) sulfate
pentahydrate (7.50 g, 30.0 mmol) were ground until hom-
ogenous and added to a 500 mL round-bottom flask
containing 4-iodoaniline (4.38 g, 20.0 mmol) and a mag-
netic stir bar. CHCl3 (200 mL) was added and the
suspension was allowed to stir for 4 days. Upon completion,
the reaction was filtered through a silica gel plug, washed
with CHCl3, and the solvent was removed in vacuo. Flash
chromatography, silica gel (CH2Cl2) afforded the desired
product as an orange solid (1.25 g, 15%). 1H NMR
(400 MHz, CDCl3) d 7.86 (d, J¼9 Hz, 4H), 7.64 (d, J¼
9 Hz, 4H).
7.7.2. Thioacetic acid S-(4-{4-[4-(4-acetylsulfanyl-phenyl
ethynyl)-phenylazo]-phenylethynyl}-phenyl) ester (2).
Bis-(4-iodo-phenyl)-diazene (5)16 (0.69 g, 1.59 mmol)
was coupled to 4-ethynyl-1-thioacetylbenzene1 (0.63 g,
3.57 mmol) following the general coupling procedure at
50–608C for 20 min. The mixture was poured into ether
and washed with a saturated aqueous ammonium chloride
solution. The organic layer was dried using anhydrous
MgSO4 and concentrated in vacuo. The remaining solid
was dissolved in hot CH2Cl2 and filtered. The filtrate was
concentrated to afford the product (0.36 g, 43%). Mp:
decomposes at 2468C. IR (KBr) 3051.7, 2923.0, 2206.6,
1911.7, 1692.0, 1594.4, 1557.4, 1497.5, 1479.5, 1396.5,
1353.5, 1297.5, 1282.8, 1261.4, 1221.0, 1181.4, 1154.1,
1110.3, 1012.2, 951.0, 852.3, 823.8, 734.3, 708.4,
7.7.6. Bis-(4-phenylethynyl-phenyl)-diazene (6). Bis-(4-
iodo-phenyl)-diazene (5) (0.25 g, 0.58 mmol) was coupled
to phenylacetylene (0.15 mL, 1.38 mmol) according to the
general procedure. Flash chromatography, silica gel (5:1
hexanes/CH2Cl2) afforded the product (0.088 g, 40%). Mp:
decomposes at 2468C. IR (KBr) 3019.1, 2399.9, 1215.3,
769.3, 668.8 cm21. 1H NMR (400 MHz, CDCl3) d 7.94 (d,
J¼6.4 Hz, 4H), 7.69 (d, J¼6.4 Hz, 4H), 7.58 (m, 4H), 7.39
(m, 6H). 13C NMR (100 MHz, CDCl3) d 152.2, 132.9,
132.1, 129.1, 128.9, 126.7, 123.5, 123.3, 92.6, 89.6. HRMS
calcd for C28H18N2: 382.1470. Found: 382.1469.
1
622.7 cm21. H NMR (400 MHz, CDCl3) d 7.95 (d, J¼
9 Hz, 4H), 7.69 (d, J¼9 Hz, 4H), 7.6 (d, J¼9 Hz, 4H), 7.43
(d, J¼9 Hz, 4H), 2.45 (s, 6H). 13C NMR (100 MHz, CDCl3)
d 193.8, 152.4, 134.7, 133.0, 132.7, 128.9, 125.8, 124.6,
123.5, 91.7, 91.4, 30.7. HRMS calcd for C32H22N2O2S2:
530.1123. Found: 530.1122.
7.7.3. Thioacetic acid S-(4-{4-[4-(4-acetylsulfanyl-phenyl-
ethynyl)-2-nitro-phenylazo]-3-nitro-phenylethynyl}-
phenyl) ester (3). Bis-(4-iodo-2-nitro-phenyl)-diazene (7)
(0.100 g, 0.286 mmol) was coupled to 4-ethynyl-1-thio-
acetylbenzene1 (0.11 g, 2.29 mmol) according to the
general coupling procedure. After 30 min the reaction was
complete and poured into CH2Cl2 (100 mL) and MeOH
(100 mL). Care was taken to remove mainly the more
volatile CH2Cl2 on the rotovap. The precipitate was vacuum
filtered and washed with MeOH to afford 3 (0.06 g, 30%).
Mp: decomposes at 3508C. IR (KBr) 2359.5, 2341.3,
7.7.7. Bis-(4-iodo-2-nitro-phenyl)-diazene (7). To
a
250 mL round-bottom flask charged with a magnetic stir
bar was added 4-iodo-2-nitroaniline (2.00 g, 7.58 mmol),
mercury(II) oxide (2.46 g, 11.36 mmol), and iodine (2.88 g,
11.36 mmol). CH2Cl2 (80 mL) was added and the reaction
mixture was allowed to stir overnight. The next day the
suspension was filtered through a silica gel plug and washed
with copious amounts of CH2Cl2. The filtrate was then
washed with a saturated aqueous solution of sodium
thiosulfate, dried over anhydrous MgSO4, and the solvent
removed in vacuo. Flash chromatography, silica gel (1:1
petroleum ether/diethyl ether) afforded the product as brown
crystals (0.15 g, 4%). Mp: 2448C. IR (KBr) 3076.3, 3019.1,
1714.9, 1529.2, 1087.8, 772.0, 667.0 cm21 1H NMR
.
(400 MHz, CDCl3) d 8.12 (d, J¼1.9 Hz, 2H), 7.82 (dd,
J¼7.6, 1.9 Hz, 2H), 7.73 (d, J¼7.6 Hz, 2H), 7.62 (d, J¼
9.0 Hz, 4H), 7.46 (d, J¼9.0 Hz, 4H), 2.47 (s, 6H). Repeated
attempts to obtain the 13C NMR, even at 125 MHz, were
unsuccessful due to the insolubility of the material. HRMS
calcd for C32H20N4O6S2: 620.0824. Found: 620.0820.
1517.1, 1336.1, 1215.1, 1090.6, 840.0, 756.3, 666.5 cm21
.
1H NMR (400 MHz, CDCl3) d 8.31 (d, J¼2.0 Hz, 2H), 8.05
(dd, J¼8.1, 2.0 Hz, 2H), 7.40 (d, J¼8.1 Hz, 2H). 13C NMR
(100 MHz, CDCl3) d 148.4, 144.8, 143.3, 133.6, 120.3,
97.6. HRMS calcd for C12H6N4O4I2: 523.8478. Found:
523.8492.
7.7.4. Thioacetic acid S-[4-(4-{N0-[4-(4-acetylsulfanyl-
phenylethynyl)-2-nitro-phenyl]-hydrazino}-3-nitro-phenyl-
ethynyl)-phenyl] ester (4). The filtrate and MeOH wash-
ings from 3 were combined and the solvent was removed in
vacuo. The residue was dissolved in a minimum amount of
CH2Cl2 followed by the addition of hexanes (100 mL). Care
was taken to remove only mainly the more volatile CH2Cl2
in vacuo. The solid was vacuum filtered and washed with
hexanes. The solid was purified by flash chromatography,
silica gel (CH2Cl2) to afford 4 as an orange solid (0.105 g,
59%). Mp: 226–2328C. IR (KBr) 3370.9, 3018.9, 2399.7,
7.7.8. Thioacetic acid S-{4-[50-(4-acetylsulfanyl-phenyl-
ethynyl)-3,30-dinitro-[2,20]bipyridinyl-5-ylethynyl]-phe-
nyl} ester (8). Compound 13 (1.6 g, 3.7 mmol), potassium
carbonate (4.5 g, 33 mmol), methanol (15 mL) and dichlor-
omethane (15 mL) were used following the general
deprotection method. A short silica gel plug (1:1 hexanes/
CH2Cl2) afforded the desired product as a brown solid
(1.06 g, 99% yield). 1H NMR (200 MHz, CDCl3) d 8.88 (d,

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8565
J¼1.8 Hz, 2H), 8.58 (d, J¼1.8 Hz, 2H), 3.45 (s, 2H). The
deprotected material (1.06 g, 3.65 mmol) was then immedi-
ately coupled according to the general procedure using
bis(dibenzylideneacetone)palladium (0.11 g, 0.18 mmol),
copper(I) iodide (0.07 g, 0.37 mmol), triphenylphosphine
(0.20 g, 0.74 mmol), THF (18 mL), DIEA (2.5 mL,
15 mmol), and 4-(thioacetyl)iodobenzene1 (3.05 g,
10.95 mmol). The tube was placed in a 508C oil bath for
1 h. Flash chromatography, silica gel (CH2Cl2) gave the
desired product as an orange-yellow solid (1.51 g, 69%).
Mp: 198–1998C. IR (KBr) 3394.5, 3057.1, 2212.6, 1705.2,
1542.8, 1487.5, 1446.0, 1351.6, 1108.2, 1084.1, 954.2,
palladium (0.05 g, 0.09 mmol), copper(I) iodide (0.03 g,
0.18 mmol), triphenylphosphine (0.10 g, 0.37 mmol), THF
(10 mL), DIEA (0.38 mL, 2.18 mmol), and 4-(thioacetyl)-
iodobenzene1 (0.51 g, 1.82 mmol). The tube was placed in a
508C oil bath for 3 h. Column chromatography, silica gel
(1:1 hexanes/CH2Cl2 then ethyl acetate) and precipitation
from CH2Cl2 and hexanes gave the desired product as an
orange solid (0.41 g, 55%). Mp: decomposes at 1108C. IR
(KBr) 3042.4, 2929.7, 2215.3, 2151.2, 1712.4, 1696.4,
1665.5, 1647.5, 1588.3, 1540.3, 1490.4, 1448.8, 1379.5,
1348.4, 1244.3, 1123.8, 827.9, 756.8, 688.0, 619.8,
1
526.9 cm21. H NMR (400 MHz, CDCl3) d 8.90 (d, J¼
829.1, 619.1, 598.1, 544.3. cm21
.
1H NMR (200 MHz,
1.9 Hz, 1H), 8.45 (d, J¼1.9 Hz, 1H), 7.68 (m, 2H), 7.58
(d, J¼8.8 Hz, 2H), 7.43 (m, 5H), 2.44 (s, 3H). 13C NMR
(100 MHz, CDCl3) d 193.4, 155.6, 146.6, 136.1, 134.8,
134.7, 133.1, 132.8, 130.7, 130.4, 129.0, 122.9, 121.7,
120.1, 100.2, 96.4, 85.7, 85.6, 30.8. HRMS calcd for
C23H14N2O3S: 398.0725. Found: 398.0723.
CDCl3) d 8.93 (d, J¼1.7 Hz, 2H), 8.62 (d, J¼1.8 Hz, 2H),
7.60 (d, J¼7.6 Hz, 4H), 7.45 (d, J¼7.6 Hz, 4H), 2.44 (s,
6H). 13C NMR (100 MHz, CDCl3) d 193.3, 155.2, 149.4,
144.1, 135.4, 134.8, 132.9, 130.5, 122.8, 122.2, 96.0, 85.2,
30.8. HRMS calcd for C30H18N4O6S2: 594.0668. Found:
594.0664.
7.7.11. 3,30-Dinitro-[2,20]bipyridinyl (11).21 To a 250 mL
round-bottom flask equipped with a reflux condenser and
stir bar was added 2-chloro-3-nitropyridene (12.0 g,
75.8 mmol) in dimethylformamide (50 mL). Copper bronze
(12.0 g, 189.0 mmol) was added slowly and the mixture was
heated to 1458C for 5.5 h. The reaction was then poured
onto ice and filtered. The remaining filtrate was extracted
in a Soxhlet extractor with acetonitrile for 4 days. The
acetonitrile was then poured into a large amount of dilute
ammonium hydroxide solution to precipitate the product,
which was then filtered. The solid was dissolved in CH2Cl2
and washed with dilute ammonium hydroxide solution. The
organic layers were combined and dried over anhydrous
MgSO4 and the solvent removed in vacuo to give a brown-
yellow solid (5.8 g, 62%). Mp: 208–2108C. 1H NMR
(400 MHz, DMSO) d 8.93 (dd, J¼3.6, 1.2 Hz, 2H), 8.72
(dd, J¼7.2, 1.1 Hz, 2H), 7.88 (dd, J¼3.6, 4.8 Hz, 2H).
7.7.12. 5,50-Dibromo-3,30-dinitro-[2,20]bipyridinyl (12).22
To a 100 mL round-bottom flask was added 11 (3.9 g,
15.8 mmol) and a stir bar. Dry methanol (25 mL) and dry
CH2Cl2 (25 mL) were added and cooled to 08C. To a three-
necked 500 mL round-bottom flask was added KBr (120 g,
1008.4 mmol) and an addition funnel with H2SO4 (conc.,
90 mL) was placed on top. The system was then sealed with
rubber septas and the two flasks connected via a cannula.
The H2SO4 was slowly added over 20 min (the temperature
must stay below 758C to prevent formation of Br2). The
precipitate that formed was filtered off and the solution
re-subjected to HBr. This affords the salt as a light yellow
powder. The salt and a stir bar were then added to a
screwcap tube and the vessel sealed with a rubber septum,
evacuated and backfilled with N2 (3£). Br2 (5 mL) was then
added and the screwcap affixed. The mixture was heated in a
1658C oil bath for 24 h. The reaction mixture was cooled
and poured into a saturated solution of sodium thiosulfate to
remove excess bromine. The crude product was extracted
with CH2Cl2 (3£) and the organic layers were combined and
dried over anhydrous MgSO4 and the solvent removed
in vacuo. The crude product was purified by column
chromatography, silica gel (1:2 hexanes/CH2Cl2) to afford
the desired product as a white-yellow solid (3.46 g, 54%).
Mp: 158–1608C. IR (KBr) 3065.9, 2869.5, 1578.2, 1545.2,
1426.6, 1346.4, 1234.0, 1103.0, 1025.6, 897.1, 879.1, 788.8,
7.7.9. Thioacetic acid S-[4-(3,30-dinitro-50-phenylethynyl-
[2,20]bipyridinyl-5-ylethynyl)-phenyl] ester (9). Com-
pound 16 (0.51 g, 1.15 mmol), potassium carbonate
(1.59 g, 11.5 mmol), methanol (15 mL), and dichloro-
methane (15 mL) were used following the general deprotec-
tion method to give the desired product as a reddish brown
solid (0.41 g, 98%). The deprotected material (0.40 g,
1.09 mmol) was then immediately coupled according to the
general procedure given using bis(dibenzylideneacetone)-
palladium (0.03 g, 0.05 mmol), copper(I) iodide (0.02 g,
0.11 mmol), triphenylphosphine (0.06 g, 0.22 mmol), THF
(10 mL), DIEA (0.38 mL, 2.18 mmol), and 4-(thioacetyl)-
iodobenzene1 (0.36 g, 1.31 mmol). The tube was placed in a
55–608C oil bath for 2 h. Flash chromatography, silica gel
(CH2Cl2) followed by precipitation from CH2Cl2 in hexanes
gave the desired product as an orange-yellow solid (0.41 g,
74% yield). Mp: 161–1628C. IR (KBr) 3442.2, 3245.4,
3071.3, 2210.8, 1709.4, 1595.7, 1543.0, 1488.6, 1444.6,
1349.3, 1110.2, 1078.7, 1028.9, 943.0, 908.3, 821.7, 764.9,
1
617.8 cm21. H NMR (400 MHz, CDCl3) d 8.93 (m, 2H),
8.61 (m, 2H), 7.60 (m, 3H), 7.43 (m, 6H), 2.45 (s, 3H). 13C
NMR (100 MHz, CDCl3) d 193.1, 155.1, 149.4, 149.1,
144.2, 135.3, 135.2, 134.7, 132.9, 132.4, 130.6, 130.2,
129.0, 122.8, 122.6, 122.1, 121.8, 97.0, 96.0, 85.2, 83.8,
30.7. HRMS calcd for C28H16N4O5S: 520.0841. Found:
520.0839.
7.7.10. Thioacetic acid S-[4-(5-nitro-6-phenylethynyl-
pyridin-3ylethynyl)-phenyl] ester (10). To a 50 mL
round-bottom flask containing a stir bar was added 20
(0.62 g, 1.89 mmol) and THF (10 mL). Acetic acid
(0.22 mL, 3.78 mmol) and then 1.0 M TBAF in THF were
then added and the reaction was allowed to stir for 15 min.
The reaction was then poured into water and the product
extracted with CH2Cl2 (3£). The organic layers were
combined and dried over anhydrous MgSO4 and the solvent
was removed in vacuo. The product was purified by column
chromatography; silica gel (CH2Cl2) afforded the product as
1
a light yellow solid (0.47 g, 98%). H NMR (400 MHz,
CDCl3) d 8.86 (d, J¼1.9 Hz, 1H), 8.42 (d, J¼1.9 Hz, 1H),
7.67 (m, 2H), 7.40 (m, 3H), 3.44 (s, 1H). The deprotected
material (0.47 g, 1.82 mmol) was then coupled according
to the general procedure using bis(dibenzylideneacetone)-

8566
A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
1
753.7, 649.2, 551.7 cm21. H NMR (400 MHz, CDCl3) d
8.90 (d, J¼2.2 Hz, 2H), 8.68 (d, J¼2.2 Hz, 2H). 13C NMR
(100 MHz, CDCl3) d 154.7, 149.0, 144.2, 136.0, 121.3.
HRMS calcd for C10H4Br2N4O4: 403.8581. Found: 403.8580.
1.49 mmol) was coupled with phenylacetylene (0.33 mL,
3.0 mmol) according to the general coupling procedure.
Bis(triphenylphosphine)palladium(II) dichloride (0.05 g,
0.07 mmol), copper(I) iodide (0.03 g, 0.14 mmol), THF
(5 mL), and DIEA (0.78 mL, 4.5 mmol) were combined and
the mixture was heated in a 558C oil bath for 3.5 h. Column
chromatography, silica gel (1:1 hexanes/CH2Cl2) afforded
the product as a brown-yellow solid (0.51 g, 77%). IR (KBr)
3060.9, 2958.3, 2217.2, 2141.1, 1595.7, 1542.8, 1442.9,
1349.4, 1248.9, 1028.7, 912.5, 848.8, 759.1, 689.4,
7.7.13. 3,30-Dinitro-5,50-bis-trimethylsilanylethynyl-[2,20]-
dinitro-bipyridinyl (13). Compound 12 (3.51 g,
8.69 mmol) was coupled with TMSA (1.72 mL,
12.17 mmol) following the general coupling procedure.
Bis(triphenylphosphine)palladium(II) dichloride (0.3 g,
0.43 mmol), copper(I) iodide (0.16 g, 0.86 mmol), THF
(6 mL), and DIEA (6.05 mL, 34.76 mmol) were combined
and the mixture was stirred at room temperature for 3 h.
Column chromatography, silica gel (1:1 hexanes/CH2Cl2)
afforded the product as a dark yellow solid (1.64 g, 43%).
Mp: 157–1598C. IR (KBr) 3083.6, 2956.5, 2896.5, 2156.5,
1594.8, 1542.8, 1448.0, 1382.9, 1358.6, 1248.0, 1191.7,
1
524.1 cm21. H NMR (400 MHz, CDCl3) d 8.87 (d, J¼
2.1 Hz, 2H), 8.55 (d, J¼2.1 Hz, 2H), 7.58 (m, 2H), 7.40 (m,
3H), 0.31 (s, 9H). 13C NMR (100 MHz, CDCl3) d 155.6,
155.2, 149.4, 149.1, 144.1, 143.9, 135.7, 135.2, 132.4,
130.2, 129.1, 122.6, 122.3, 121.8, 103.8, 98.7, 97.0, 83.8,
0.0. HRMS calcd for: C23H18N4O4Si: 442.1097. Found:
442.1095.
1029.8, 950.2, 918.5, 843.6, 759.9, 696.3, 641.6 cm21. H
1
NMR (400 MHz, CDCl3) d 8.83 (d, J¼1.9 Hz, 2H), 8.52 (d,
J¼1.9 Hz, 2H), 0.28 (s, 18H). 13C NMR (100 MHz, CDCl3)
d 155.5, 149.4, 143.9, 135.7, 122.2, 103.8, 98.7, 0.0. HRMS
calcd for C20H22N4O4Si2: 438.1180. Found: 438.1180.
7.7.17. 5-Bromo-3-nitro-pyridin-2-ylamine (17).24 To a
250 mL round-bottom flask was added sulfuric acid (60 mL)
and a stir bar and the mixture was cooled to 08C. 4-Bromo-
2-aminopyridine (10.0 g, 57.8 mmol) was then added
slowly. Fuming nitric acid (1.9 mL) was then added
dropwise and the solution began to turn yellow. The
solution was stirred for 1 h at 08C, 1.5 h at room
temperature, and 1 h at 508C (during which time it turned
orange-red). The mixture was poured onto ice, neutralized,
and the precipitate filtered and washed with cold water to
give a dark yellow solid (10.4 g, 83%). Mp: decomposes at
7.7.14. 3,30-Dinitro-5,50-bis-phenylethynyl-[2,20]bipyridinyl
(14). Compound 12 (0.21 g, 0.52 mmol) was coupled with
phenylacetylene (0.23 mL, 2.08 mmol) following the gen-
eral coupling procedure. Bis(triphenylphosphine)palla-
dium(II) dichloride (0.02 g, 0.03 mmol), copper(I) iodide
(0.01 g, 0.06 mmol), THF (1 mL), and DIEA (0.36 mL,
2.08 mmol) were added and the tube was capped and heated
in a 508C oil bath for 1 h then allowed to stir for 15 h at
room temperature. Column chromatography, silica gel (1:1
hexanes/CH2Cl2) afforded the product as a dark yellow solid
(0.13 g, 48%). Mp: decomposes at 2268C. IR (KBr) 3068.0,
2209.4, 1544.0, 1489.0, 1442.5, 1350.3, 1029.9, 909.4,
1
1808C. H NMR (400 MHz, CDCl3) d 8.57 (d, J¼2.3 Hz,
1H), 8.40 (d, J¼2.3 Hz, 1H), 6.79 (br s, 2H).
7.7.18. 2,5-Dibromo-3-nitro-pyridine (18).25 To a 50 mL
round-bottom flask was added 17 (0.5 g, 2.3 mmol) in HBr
(2 mL, 48%) with a stir bar. This was cooled to 08C and
bromine (0.41 mL, 8.0 mmol) was added followed by
sodium nitrite (0.47 g, 6.9 mmol). After 0.5 h, the solution
was warmed to room temperature and an additional portion
of sodium nitrite (1 g, 14.5 mmol), HBr (1 mL, 48%) and
water (2 mL). After the bubbling stopped, the solution was
made alkaline and sodium thiosulfite was added to remove
excess bromine. The product was then extracted with
CH2Cl2 (3£). The organic layers were combined and dried
over anhydrous MgSO4 and the solvent was removed in
vacuo to give a yellow solid (0.33 g, 51%). Mp: 93–948C.
1H NMR (400 MHz, CDCl3) d 8.64 (d, J¼2.2 Hz, 1H), 8.25
(d, J¼2.2 Hz, 1H).
1
821.9, 764.3, 689.7 cm21. H NMR (400 MHz, CDCl3) d
8.93 (d, J¼1.8 Hz, 2H), 8.60 (d, J¼1.8 Hz, 2H), 7.58 (m,
4H), 7.41 (m, 6H). 13C NMR (100 MHz, CDCl3) d 155.1,
149.1, 144.2, 135.2, 132.4, 130.1, 129.0, 122.5, 121.8, 97.0,
83.8. HRMS calcd for C26H14N4O4: 446.1015. Found:
446.1014.
7.7.15. 50-Bromo-3,30-dinitro-5-trimethylsilanylethynyl-
[2,20]bipyridinyl (15). Compound 12 (0.34 g, 0.84 mmol)
was coupled with TMSA (0.09 mL, 0.84 mmol) following
the general coupling procedure. Bis(triphenylphosphine)-
palladium(II) dichloride (0.03 g, 0.04 mmol), copper(I)
iodide (0.015 g, 0.08 mmol), THF (5 mL), and DIEA
(0.29 mL, 1.68 mmol) were combined and the mixture
was allowed to stir at room temperature for 1 h. Column
chromatography, silica gel (1:1 hexanes/CH2Cl2) afforded
the product as a yellow solid (0.25 g, 71%). IR (KBr)
3069.4, 2960.2, 2359.8, 1585.4, 1543.7, 1436.8, 1344.3,
1249.9, 1105.2, 1029.1, 848.3, 812.6, 784.7, 764.0,
7.7.19. 5-Bromo-3-nitro-2-phenylethynyl-pyridine (19).
Compound 18 (2.05 g, 7.27 mmol) was coupled to phenyl-
acetylene (0.80 mL, 7.27 mmol) according to the general
coupling procedure. Bis(triphenylphosphine)palladium(II)
dichloride (0.15 g, 0.21 mmol), copper(I) iodide (0.08 g,
0.43 mmol), THF (10 mL), and DIEA (2.5 mL, 14.5 mmol)
were combined and the reaction mixture was allowed to stir
for 2 h at room temperature. Column chromatography, silica
gel (1:1 hexanes/CH2Cl2) afforded the product as dark
yellow flakes (1.32 g, 60%). Mp: 83–858C. IR (KBr)
3071.3, 2218.4, 1577.4, 1544.6, 1513.7, 1487.0, 1434.8,
1369.0, 1334.9, 1218.9, 1151.0, 1100.0, 1070.5, 913.9,
1
646.9 cm21. H NMR (400 MHz, CDCl3) d 8.89 (d, J¼
2.0 Hz, 1H), 8.83 (d, J¼2.0 Hz, 1H), 8.67 (d, J¼2.0 Hz,
1H), 8.53 (d, J¼2.0 Hz, 1H), 0.29 (s, 9H). 13C NMR
(100 MHz, CDCl3) d 155.6, 154.6, 149.4, 149.0, 144.3,
143.8, 135.9, 135.7, 122.4, 121.1, 104.0, 98.6, 0.0. HRMS
calcd for C15H13BrN4O4Si: 419.9890. Found: 419.9884.
892.7, 836.9, 755.7, 687.1, 518.8 cm21
.
1H NMR
7.7.16. 3,30-Dinitro-50-phenylethynyl-5-trimethylsilanyl-
(400 MHz, CDCl3) d 8.87 (d, J¼2.0 Hz, 1H), 8.52 (d,
ethynyl-[2,20]bipyridinyl (16). Compound 15 (0.63 g,
J¼2.2 Hz, 1H), 7.66 (m, 2H), 7.40 (m, 3H). 13C NMR

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8567
(100 MHz, CDCl3) d 155.1, 136.1, 135.3, 133.0, 130.7,
129.0, 121.5, 119.1, 99.7, 84.9. HRMS calcd for
C13H7BrN2O2: 301.9695. Found: 301.9691.
product was purified by running the material through a plug
of silica to afford the desired product as a bright yellow solid
(0.09 g, 54%). Mp: 200–2108C dec. IR (KBr) 3022.9,
1699.5, 1589.0, 1510.3, 1488.1, 1447.7, 1417.5, 1352.6,
1120.7, 1011.2, 967.2, 945.8, 861.8, 826.2, 754.4, 691.9,
7.7.20. 3-Nitro-2-phenylethynyl-5-trimethylsilanylethynyl-
pyridene (20). Compound 19 (1.3 g, 4.28 mmol) was
coupled with TMSA (0.73 mL, 5.14 mmol) following the
general coupling procedure. Bis(triphenylphosphine)palla-
dium(II) dichloride (0.09 g, 0.13 mmol), copper(I) iodide
(0.05 g, 0.26 mmol), THF (10 mL), and DIEA (1.49 mL,
8.56 mmol) were combined and the mixture was allowed to
stir at room temperature for 2 h. Column chromatography,
silica gel (1:2 hexanes/CH2Cl2) afforded the product as a
dark yellow solid (0.62 g, 44%). Mp: 78–798C. IR (KBr)
3057.4, 2955.8, 2896.1, 2217.6, 2159.9, 1595.4, 1543.9,
1491.4, 1448.1, 1346.2, 1247.1, 1187.9, 1157.7, 1070.7,
960.4, 918.7, 862.2, 842.8, 806.7, 766.4, 751.2, 685.1,
1
615.9, 549.2 cm21. H NMR (400 MHz, CDCl3) d 7.55–
7.49 (m, 8H), 7.39–7.33 (m, 4H), 7.27–7.23 (m, 1H), 7.12–
7.11 (m, 3H), 2.42 (s, 3H). 13C NMR (100 MHz, CDCl3) d
194.6, 139.0, 137.7, 137.5, 136.7, 135.1, 130.2, 129.3,
129.1, 128.6, 128.1, 127.9, 127.6, 127.4, 127.3, 127.2,
127.0, 30.6. HRMS calcd for C24H20OS: 356.1235. Found:
356.1237.
7.7.23. Thioacetic acid S-[4-(2-{4-[2-(4-acetylsulfanyl-
phenyl)-vinyl]-3-nitro-phenyl}-vinyl)-phenyl] ester (23).
To a large test-tube equipped with a stir bar was added 36
(0.12 g, 0.20 mmol) and THF (3 mL). To the solution was
added dropwise TBAF (4.0 mL, 1 M in THF). The solution
changed from yellow to dark purple and it was allowed to
stir for 1 h. Acetyl chloride (0.6 mL, 8 mmol) was added
and the dark purple solution changed to light yellow. The
solution was allowed to stir for 15 min and then worked up
with water (10 mL) and extracted with ethyl acetate
(20 mL). The organics were dried over MgSO4, filtered,
and the solvent was removed in vacuo. The crude product
was purified by running the material through a plug of silica
to yield the desired compound as a bright yellow solid
(0.036 g, 36%). Mp: 170–1808C dec. IR (KBr) 3429.3,
3025.2, 1697.3, 1520.6, 1403.3, 1349.0, 1118.3, 1088.2,
1
631.6, 561.4, 529.6 cm21. H NMR (400 MHz, CDCl3) d
8.79 (d, J¼2.0 Hz, 1H), 8.35 (d, J¼2.0 Hz, 1H), 7.64 (m,
2H), 7.37 (m, 3H), 0.26 (s, 9H). 13C NMR (100 MHz,
CDCl3) d 156.0, 146.5, 136.1, 135.2, 133.1, 130.6, 129.0,
121.7, 120.2, 104.0, 100.0, 99.1, 85.6, 0.0. HRMS calcd for
C18H16N2O2Si: 320.0983. Found: 320.0981.
7.7.21. Thioacetic acid S-{4-[2-(2-nitro-4-styryl-phenyl)-
vinyl]-phenyl} ester (21). To a large test-tube equipped
with a stir bar was added 33 (0.15 g, 0.32 mmol) and THF
(4 mL). To the solution was added dropwise TBAF (3.2 mL,
1 M in THF). The solution changed from light orange to
dark purple and the solution was allowed stirred for 1 h.
Acetyl chloride was added (0.5 mL, 6.4 mmol) and the dark
purple solution changed to light yellow. The solution was
allowed to stir for 15 min and then worked up with water
(10 mL) and extracted with ethyl acetate (20 mL). The
organics were dried over MgSO4, filtered, and the solvent
was removed in vacuo. The crude product was purified by
running the material through a plug of silica to yield the
desired compound as a bright yellow solid (0.12 g, 95%).
Mp: 128–1318C. IR (KBr) 3027.5, 2923.6, 1706.5, 1634.6,
1523.1, 1492.8, 1449.2, 1406.1, 1347.1, 1318.5, 1283.2,
1258.3, 1215.6, 1187.6, 1121.7, 1088.3, 1011.4, 965.5,
1011.0, 946.5, 828.2, 618.5, 552.6 cm21
.
1H NMR
(400 MHz, CDCl3) d 8.08 (d, J¼1.6 Hz, 1H), 7.75 (d, J¼
8.0 Hz, 1H), 7.71 (dd, J¼8.0, 1.6 Hz, 1H), 7.62 (d, J¼
16.4 Hz, 1H), 7.58–7.54 (m, 3H), 7.42 (d, J¼8.0 Hz, 4H),
7.18–7.08 (m, 3H), 2.43 (s, 3H), 2.42 (s, 3H). 13C NMR
(100 MHz, CDCl3) d 194.0, 194.0, 148.7, 137.8, 137.7,
135.0, 135.0, 132.9, 131.6, 130.8, 130.7, 128.6, 128.4,
128.2, 127.9, 127.7, 127.4, 124.8, 122.8, 30.5. HRMS calcd
for C26H21NO4S2: 475.0912. Found: 475.0912.
7.7.24. Tributylvinylstannane (24).27 Vinyl magnesium
bromide (100.0 mL of a 1 M solution in THF) and
tributyltin chloride (13.8 mL, 50.0 mmol) were added to a
N2 purged 250 mL round-bottom flask equipped with a stir
bar and a condenser. The solution was heated at reflux
overnight and then cooled to room temperature. NH4Cl (aq)
(80 mL) was added slowly to the mixture and the organics
were decanted into a 500 mL round-bottom flask. The
remaining aqueous layer was washed with ether (4£50 mL)
and the ether was decanted into the round-bottom. The
product was purified by distilling at 1158C at 2.5 mm Hg to
yield the desired product as a clear liquid (11.79 g, 74%). 1H
NMR (400 MHz, CDCl3) d 6.45 (dd, J¼20.8, 14.1 Hz, 1H),
6.13 (dd, J¼14.0, 3.7 Hz, 1H), 5.64 (dd, J¼20.7, 3.6 Hz,
1H), 1.49 (m, 6H), 1.29 (sex, J¼7.2 Hz, 6H), 0.87 (m, 15H).
7.7.25. 4-Vinylbenzenethioacetate (25).26 4-(Thioacetyl)-
iodobenzene1 (1.92 g, 6.92 mmol), bis(dibenzylideneacetone)-
palladium (0.120 g, 0.21 mmol), triphenylarsene (0.129 g,
0.42 mmol), tributylvinylstannane 24 (2.12 mL, 7.27 mmol),
and THF (15 mL) were coupled according to the general
Stille coupling procedure. The crude product was purified
via column chromatography, silica gel (1:1 CH2Cl2/
petroleum ether) to yield 0.844 g (68%) of a yellow oil.
1
906.0, 814.2, 751.1, 690.0, 615.8, 564.9, 529.4 cm21. H
NMR (400 MHz, CDCl3) d 8.07 (d, J¼1.6 Hz, 1H), 7.74
(d J¼8.4 Hz, 1H), 7.70 (dd, J¼8.4, 1.6 Hz, 1H), 7.62 (d,
J¼16.0 Hz, 1H), 7.57–7.48 (m, 4H), 7.42–7.36 (m, 4H),
7.30 (tt, J¼7.2, 2.0 Hz, 1H), 7.21 (d, J¼16.0 Hz, 1H), 7.09
(dd, J¼16.0, 2.0 Hz, 2H), 2.42 (s, 3H). 13C NMR (100 MHz,
CDCl3) d 194.2, 148.8, 138.5, 138.1, 136.7, 135.2, 132.8,
132.0, 131.5, 130.9, 129.3, 129.0, 128.7, 128.5, 128.1,
127.3, 126.2, 125.1, 122.8, 30.7. HRMS calcd for
C24H19NO3S: 401.1086. Found: 401.1084.
7.7.22. Thioacetic acid S-{4-[2-(4-styrylphenyl)-vinyl]-
phenyl} ester (22). To a large test-tube equipped with a stir
bar was added 35 (0.20 g, 0.48 mmol) and THF (5 mL). To
the solution was added dropwise TBAF (4.8 mL, 1 M in
THF). The solution changed from light yellow to blood-red
and stirring was continued for 1 h. Acetyl chloride (0.7 mL,
9.6 mmol) was added and the solution changed to light
yellow. After stirring for an additional 15 min the mixture
was worked up with water (10 mL) and extracted with ethyl
acetate (20 mL). The organics were dried over MgSO4,
filtered, and the solvent was removed in vacuo. The crude

8568
A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
IR (KBr) 3087.9, 3008.5, 2956.8, 2922.6, 2853.8, 1708.7,
1629.2, 1593.3, 1491.8, 1420.9, 1395.5, 1352.6, 1269.1,
1114.0, 1093.0, 1013.1, 989.9, 949.9, 913.8, 837.0, 738.0,
610.1 cm21. 1H NMR (400 MHz, CDCl3) d 7.42 (dt, J¼8.2,
1.8 Hz, 2H), 7.34 (dt, J¼8.2, 1.9 Hz, 2H), 6.70 (dd, J¼17.7,
10.9 Hz, 1H), 5.78 (dd, J¼17.6, 0.8 Hz, 1H), 5.31 (dt, J¼
10.9, 0.7 Hz, 1H), 2.40 (s, 3H). 13C NMR (100 MHz,
CDCl3) d 194.5, 139.2, 136.4, 135.0, 127.5, 127.4, 115.9,
30.6.
7.7.29. 2-Nitro-4-styryl-1-(4-vinyl-phenylsulfanyl)-ben-
zene (29). Palladium(II) acetate (11 mg, 0.050 mmol) and
BHT (1 crystal) were added to a 25 mL round-bottom flask.
The atmosphere was removed and replaced with N2 and a
solution of 25 (0.18 g, 1.0 mmol), 28 (0.35 g, 1.0 mmol),
and DIEA (0.19 mL, 1.1 mmol) in DMF (5 mL) was then
added via cannula to the round-bottom flask. The reaction
mixture was heated to 858C overnight, cooled and quenched
with water (20 mL) and extracted with ether (20 mL). The
layers were separated and the organic phase was dried over
MgSO4, filtered and the solvent removed in vacuo. The
crude material was purified via flash column chroma-
tography, silica gel (1:1 CH2Cl2/petroleum ether) to yield
0.14 g (39%) of the titled compound. Mp: 88–908C. IR
(KBr) 3425.6, 3023.0, 2924.6, 1628.4, 1593.3, 1517.4,
1393.1, 1331.7, 1290.0, 1243.7, 1106.3, 1044.0, 958.6,
7.7.26. 2-Nitro-4-styrylaniline (26). 4-Iodo-2-nitroaniline
(5.28 g, 20.00 mmol), palladium(II) acetate (0.05 g,
0.20 mmol), styrene (2.8 mL, 24.0 mmol), DIEA (8.7 mL,
50.0 mmol), and acetonitrile (50 mL) were coupled at 808C
according to the general Heck coupling reaction above. The
crude product was purified via flash column chroma-
tography, silica gel (1:1 CH2Cl2/hexanes) to yield 3.30 g,
(69%) of a bright red solid. Mp: 202–2068C dec. IR (KBr)
3466.5, 3338.7, 3177.5, 3024.5, 1639.4, 1596.5, 1554.3,
1519.6, 1468.9, 1410.9, 1346.3, 1272.1, 1223.8, 1191.9,
1175.8, 1093.3, 957.4, 927.3, 825.6, 749.5, 689.9, 625.3,
1
909.9, 814.9, 750.9, 690.0, 566.0, 538.5, 454.2 cm21. H
NMR (400 MHz, CDCl3) d 8.32 (d, J¼2.0 Hz, 1H), 7.54–
7.43 (m, 7H), 7.37–7.33 (m, 2H), 7.30–7.28 (m, 1H), 7.12
(d, J¼16.0 Hz, 1H), 7.01 (d, J¼16.4 Hz, 1H), 6.86 (d,
J¼8.4 Hz, 1H), 6.75 (dd, J¼17.6, 10.8 Hz, 1H), 5.85 (dd,
J¼17.6, 0.4 Hz, 1H), 5.38 (dd, J¼10.8, 0.8 Hz, 1H). 13C
NMR (100 MHz, CDCl3) d 145.8, 139.7, 138.3, 136.8,
136.3, 136.2, 135.4, 131.3, 131.3, 130.7, 129.2, 129.1,
128.8, 128.2, 127.1, 125.9, 123.6, 116.4. HRMS calcd for
C22H17NO2S: 359.0980. Found: 359.0981.
1
553.5, 509.6 cm21. H NMR (400 MHz, CDCl3) d 8.20
(d, J¼2.4 Hz, 1H), 7.58 (dd, J¼8.4, 2.0 Hz, 1H), 7.48–7.46
(m, 2H), 7.34 (td, J¼7.2, 1.6 Hz, 2H), 7.26–7.22 (m, 1H),
6.80 (d, J¼8.4, 1H), 6.12 (br s, 2H). 13C NMR (100 MHz,
CDCl3) d 144.3, 137.4, 133.7, 132.6, 129.2, 128.2, 128.2,
127.5, 126.8, 126.8, 124.5, 119.6. HRMS calcd for
C14H12N2O2: 240.0899. Found: 240.0900.
7.7.30. 2-Ethenyl-5-ethenylphenylnitrobenzene (30). Bis-
(dibenzylideneacetone)palladium (0.081 g, 0.14 mmol), 28
(1.00 g, 2.85 mmol), triphenylarsene (0.086 g, 0.28 mmol),
tributylvinylstannane (0.948 g, 2.99 mmol), BHT (1 crystal)
and THF (10 mL) were reacted according to the general
Stille coupling procedure above. The crude product was
purified via flash column chromatography, silica gel (3:1
hexanes/CH2Cl2) to yield 0.646 g, (90%) of a yellow solid.
Mp: 76–778C. IR (KBr) 3078.1, 3055.3, 3026.2, 2945.1,
2925.1, 1627.1, 1543.6, 1520.6, 1491.2, 1448.2, 1415.7,
1351.6, 1149.6, 1072.5, 968.4, 922.9, 866.0, 833.1, 814.2,
7.7.27. 2-Nitro-4-styrylbenzenediazonium tetrafluoro-
borate (27). Boron trifluoride etherate (2.10 mL,
16.64 mmol) was added to a 100 mL round-bottom flask
and the temperature was reduced to 2308C. 26 (1.00 g,
4.16 mmol) in THF (20 mL) was added dropwise to
the round-bottom flask. tert-Butylnitrite (1.73 mL,
14.56 mmol) in THF (15 mL) was then added dropwise
and the temperature was allowed to rise to 258C for 30 min.
Ether (25 mL) was then added and the orange precipitate
was then collected via a fritted funnel and washed with ether
(20 mL) to yield 1.31 g (94%) of desired product that was
taken directly on to the next step without characterization.
752.8, 690.5, 619.6, 556.1, 511.0 cm21
.
1H NMR
(400 MHz, CDCl3) d 8.03 (d, J¼1.8 Hz, 1H), 7.68 (dd,
J¼8.2, 1.9 Hz, 1H), 7.61 (d, J¼8.2 Hz, 1H), 7.52 (m, 2H),
7.37 (m, 2H), 7.30 (tt, J¼7.3, 2.2 Hz, 1H), 7.19 (d, J¼
16.3 Hz, 1H), 7.15 (dt, J¼17.3, 11.0 Hz, 1H), 7.07 (d, J¼
16.3 Hz, 1H), 5.77 (dd, J¼17.3, 0.9 Hz, 1H), 5.48 (dd, J¼
10.9, 0.8 Hz, 1H). 13C NMR (100 MHz, CDCl3) d 148.7,
138.5, 136.7, 132.5, 132.1, 131.9, 130.9, 129.3, 129.0,
128.9, 127.2, 126.2, 122.4, 119.1. HRMS calcd for
C16H13NO2: 251.0946. Found: 251.0947.
7.7.28. 5-Ethenylphenyl-2-iodonitrobenzene (28). Iodine
(0.75 g, 2.95 mmol), sodium iodide (0.88 g, 5.90 mmol),
and acetonitrile (25 mL) were added to a 250 mL round-
bottom flask equipped with a stir bar. 27 was added in one
portion to the round-bottom flask. The mixture was allowed
to stir until the N2 evolution ceased (15 min). A saturated
solution of sodium thiosulfate (50 mL) and CH2Cl2 (50 mL)
were then added and stirred for 20 min. The layers were
separated and the organic phase was dried over MgSO4,
filtered and the solvent removed in vacuo. The crude
material was purified via flash column chromatography,
silica gel (1:1 CH2Cl2/hexanes) to yield 0.85 g (82%) of a
yellow solid. Mp: 77–808C. IR (KBr) 3057.7, 3025.0,
1633.4, 1545.6, 1524.0, 1466.4, 1353.6, 1329.7, 1109.0,
1013.2, 963.9, 892.7, 818.0, 751.2, 688.0, 553.7,
7.7.31. [2-(4-Iodophenylsulfanyl)ethyl]trimethylsilane
(31).30 To a 250 mL0 round-bottom flask was added
2-(trimethylsilyl)ethyl-4 -bromophenyl sulfide (3.00 g,
10.35 mmol) and THF (30 mL). The solution was cooled
to 2788C and tert-butyllithium (10.5 mL of a 1.7 M
solution in pentane) was added dropwise. The solution
was stirred at 2788C for 20 min. Diiodoethane (2.77 g,
9.82 mmol) in THF (15 mL) was added and the reaction
mixture was allowed to warm to room temperature over
20 min. The reaction was quenched with a saturated solution
of sodium thiosulfate (50 mL) and extracted with ether
(3£30 mL). The layers were separated and the organic
phase was dried over MgSO4, filtered and the solvent
removed in vacuo. The crude product was purified via flash
1
516.7 cm21. H NMR (400 MHz, CDCl3) d 7.96 (d, J¼
8.1 Hz, 1H), 7.51 (m, 2H), 7.37 (m, 3H), 7.31 (dd, J¼7.2,
1.4 Hz, 1H), 7.20 (d, J¼16.3 Hz, 1H), 7.01 (d, J¼16.4 Hz,
1H). 13C NMR (100 MHz, CDCl3) d 153.8, 142.4, 139.5,
136.4, 132.8, 131.2, 129.3, 129.2, 127.3, 125.5, 123.3, 84.1.
HRMS calcd for C14H10INO2: 350.9756. Found: 350.9755.

A. K. Flatt et al. / Tetrahedron 59 (2003) 8555–8570
8569
column chromatography, silica gel (hexanes) to yield 1.94 g
(65%) of a pale yellow liquid. 1H NMR (400 MHz, CDCl3)
d 7.56 (dt, J¼8.6, 2.5 Hz, 2H), 7.01 (dt, J¼8.6, 2.5 Hz, 2H),
2.93–2.89 (m, 2H), 0.94–0.89 (m, 2H), 0.02 (s, 9H).
7.7.35. Trimethyl-(2-{4-[2-(4-styryl-phenyl)-vinyl]-phenyl-
sulfanyl}-ethyl)-silane (35). Palladium(II) acetate (0.023 g,
0.10 mmol), K2CO3 (0.258 g, 1.87 mmol), tetrabutylammo-
nium bromide (0.974 g, 3.02 mmol), 32 (0.541 g,
2.29 mmol), 34 (0.539 g, 2.08 mmol) and DMF (10 mL)
were reacted overnight at 1058C according to the general
Heck coupling procedure above. The crude product was
purified via flash column chromatography, silica gel
(hexanes) to yield 0.754 g (87%) of a pale yellow green
solid. Mp: 240–2508C dec. IR (KBr) 3021.8, 2950.4,
1584.4, 1510.4, 1489.6, 1444.4, 1416.1, 1247.0, 1162.5,
7.7.32. Trimethyl-[2-(4-vinylphenylsulfanyl)ethyl]silane
(32).
Bis(dibenzylideneacetone)palladium
(0.15 g,
0.26 mmol), 31 (1.71 g, 5.10 mmol), triphenylarsene
(0.16 g, 0.51 mmol), tributylvinylstannane (1.71 g,
5.40 mmol), BHT (1 crystal) and THF (15 mL) were
coupled according to the general Stille coupling procedure
above. The crude product was purified via flash column
chromatography, silica gel (hexanes) to yield 0.973 g
(81%) of a pale yellow liquid. IR (KBr) 3068.2, 3007.4,
2952.4, 2916.2, 1627.3, 1594.0, 1490.6, 1419.6, 1397.2,
1250.6, 1161.8, 1092.2, 1010.1, 989.4, 833.0, 755.4, 694.5,
1089.2, 1009.5, 965.9, 823.5, 751.7, 689.9, 545.2 cm21
.
1H NMR (400 MHz, CDCl3) d 7.52–7.46 (m, 6H), 7.42
(d, J¼8.4 Hz, 2H), 7.35 (t, J¼7.6 Hz, 2H), 7.27 (d, J¼
8.4 Hz, 2H), 7.14–7.06 (m, 4H), 2.99–2.94 (m, 2H), 0.95–
0.91 (m, 2H), 0.03 (s, 9H). 13C NMR (100 MHz, CDCl3) d
137.8, 137.2, 137.1, 137.1, 135.3, 129.4, 129.1, 129.0,
128.7, 128.4, 128.2, 128.1, 127.3, 127.3, 127.2, 126.9, 29.9,
17.3, 21.3. HRMS calcd for C27H30SSi: 414.1838. Found:
414.1838.
1
474.7 cm21. H NMR (400 MHz, CDCl3) d 7.31 (d, J¼
8.6 Hz, 2H), 7.24 (d, J¼8.4 Hz, 2H), 6.65 (dd, J¼17.6,
10.09 Hz, 1H), 6.69 (dd, J¼17.5, 0.8 Hz, 1H), 5.20 (dd,
J¼10.9, 0.9 Hz, 1H), 2.96–2.92 (m, 2H), 0.94–0.87 (m,
2H), 0.02 (s, 9H). 13C NMR (100 MHz, CDCl3) d 137.2,
136.6, 135.5, 129.3, 127.0, 113.8, 29.9, 17.3, 21.4. HRMS
calcd for C13H20SSi: 236.1055. Found: 236.1055.
7.7.36. 2-Nitro-1,4-bis-{2-[4-(2-trimethylsilanyl-ethylsul-
fanyl)-phenyl]-vinyl}-benzene (36). Palladium(II) acetate
(0.045 g, 0.20 mmol), K2CO3 (0.498 g, 3.60 mmol), tetra-
butylammonium bromide (1.87 g, 5.80 mmol), 32 (1.04 g,
4.40 mmol), 2,5-dibromonitrobenzene (0.56 g, 2.0 mmol)
and DMF (10 mL) were combined overnight at 908C
according to the general Heck coupling procedure above.
The crude product was purified via flash column chroma-
tography, silica gel (3:1 hexanes/CH2Cl2) to yield 0.54 g
(46%) of a yellow-orange solid. Mp: 114–1208C. IR (KBr)
3022.1, 2950.6, 1621.3, 1589.8, 1519.7, 1493.9, 1404.9,
1349.5, 1248.4, 1186.7, 1165.3, 1090.2, 1012.4, 962.1,
7.7.33. Trimethyl-(2-{4-[2-(2-nitro-4-styryl-phenyl)-
vinyl]-phenylsulfanyl}-ethyl)-silane (33). Palladium(II)
acetate (0.009 g, 0.040 mmol), K2CO3 (0.095 g, 0.69 mmol),
tetrabutylammonium bromide (0.372 g, 1.12 mmol), 28
(0.270 g, 0.77 mmol), 32 (0.218 g, 0.92 mmol) and DMF
(7 mL) were coupled according to the general Heck
coupling procedure above. The crude product was purified
via flash column chromatography, silica gel (1:3 CH2Cl2/
hexanes) to yield 0.259 g (73%) of a yellow solid. IR (KBr)
3424.9, 3024.3, 2950.6, 1621.8, 1589.2, 1521.1, 1347.2,
1248.8, 1090.1, 1012.2, 962.1, 858.8, 824.2, 757.8,
895.3, 859.5, 830.0, 758.5, 726.2, 690.9, 545.0, 505.2 cm21
.
1H NMR (400 MHz, CDCl3) d 8.02 (d, J¼1.6 Hz, 1H), 7.73
(d, J¼ 8.0, 1H), 7.66 (dd, J¼8.4, 1.6 Hz, 1H), 7.53 (d,
J¼16.0 Hz, 1H), 7.45–7.42 (m, 4H), 7.28–7.26 (m, 4H),
7.14 (d, J¼ 16.4 Hz, 1H), 7.06 (d, J¼16.0 Hz, 1H), 7.03 (d,
J¼16.4 Hz, 1H), 3.00–2.96 (m, 4H), 0.96–0.92 (m, 4H),
0.04 (s, 18H). 13C NMR (100 MHz, CDCl3) d 148.7, 138.8,
138.6, 138.0, 134.2, 134.0, 133.3, 131.7, 131.1, 130.1,
128.9, 128.9, 128.4, 127.9, 127.6, 125.6, 122.8, 122.7, 30.1,
29.5, 17.2, 21.6. HRMS calcd for C32H41NO2S2Si2:
591.2117. Found: 591.2114.
1
692.6 cm21. H NMR (400 MHz, CDCl3) d 8.04 (d, J¼
2.0 Hz, 1H), 7.72 (d, J¼8.0 Hz, 1H), 7.68 (dd, J¼8.4, 1.6,
1H), 7.56–7.51 (m, 3H), 7.44 (d, J¼8 Hz, 2H), 7.39–7.36
(m, 3H), 7.32–7.26 (m, 3H), 7.20 (d, J¼16.4, 1H), 7.07 (dd,
J¼16.4, 3.6 Hz, 2H), 3.00–2.96 (m, 2H), 0.96–0.92 (m,
2H), 0.04 (s, 9H). 13C NMR (100 MHz, CDCl3) d 148.7,
138.7, 138.0, 136.8, 134.3, 133.4, 131.8, 131.8, 130.8,
129.3, 129.0, 128.9, 128.4, 127.8, 127.2, 126.3, 122.9,
122.8, 29.6, 17.2, 21.3. HRMS calcd for C27H29NO2SSi:
459.1688. Found: 459.1687.
7.7.34. 4-Ethenylphenylbromobenzene (34). Palladium
(II) acetate (0.22 g, 1.0 mmol), K2CO3 (2.49 g, 18.0 mmol),
tetrabutylammonium bromide (9.35 g, 1.12 mmol), styrene
(2.31 mL, 20.0 mmol), 4-bromoiodobenzene (5.66 g,
20.0 mmol) and DMF (50 mL) were coupled according to
the general Heck coupling procedure above. The crude
product was purified via flash column chromatography,
silica gel (hexanes) to yield 3.11 g (60%) of a white solid.
Mp: 122–1268C. IR (KBr) 3079.2, 3019.9, 1578.6, 1489.5,
1447.3, 1399.2, 1327.8, 1302.0, 1215.2, 1183.2, 1072.4,
Acknowledgements
This work was supported by the Defense Advanced
Research Projects Agency, the Office of Naval Research,
and the National Institute for Standards and Technology.
The National Science Foundation, CHEM 0075728, pro-
vided partial funds for the 400 MHz NMR. We thank Dr
I. Chester at FAR Research Inc. for supplying
trimethylsilylacetylene.
1
1004.6, 966.8, 863.4, 813.0, 749.6, 689.1, 525.9 cm21. H
NMR (400 MHz, CDCl3) d 7.50–7.45 (m, 4H), 7.38–7.33
(m, 4H), 7.26 (tt, J¼7.2, 1.2 Hz, 1H), 7.09 (d, J¼16.4 Hz,
1H), 7.01 (d, J¼16.0 Hz, 1H). 13C NMR (100 MHz, CDCl3)
d 137.4, 136.7, 132.2, 129.8, 129.2, 128, 8.4, 128.3, 127.8,
127.0, 121.7. HRMS calcd for C14H11Br: 258.0044. Found:
258.0044.
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