Convergent synthetic routes to orthogonally fused conjugated oligomers directed toward molecular scale electronic device applications

Article abstract of DOI:10.1021/jo960897b

This paper describes the synthetic organic phase of a project directed toward the construction of molecular scale electronic devices. Outlined is a convergent synthetic route to orthogonally fused conjugated organic oligomers. The final systems are to have a potentially conducting chain fused perpendicularly to a second potentially conducting chain via a a bonded network. One of the core segments synthesized is based on a spirobithiophene moiety with a central silicon atom. It is formed by a zirconium-promoted bis(bicyclization) of a tetrapropargylsilane. The second core is a 9,9′-spirobifluorene system. Terminal halide groups provide the linkage points for further extension of the chains via Pd-catalyzed or Pd/Cu-catalyzed cross coupling methods. All four branching arms are affixed to the core in a single operation, thus making the syntheses highly convergent. In the cases of the larger functionalized systems, alkyl substituents on the thiophenes afford soluble materials. In order to prepare the molecules with > 50 A lengths, an iterative divergent/convergent approach had to be utilized for the construction of oligo(thiophene-ethynylene) branching arms. Organopalladium-catalyzed procedures are used extensively for the syntheses of the orthogonally fused compounds.

Full text of DOI:10.1021/jo960897b

6906
J . Org. Chem. 1996, 61, 6906-6921
Con ver gen t Syn th etic Rou tes to Or th ogon a lly F u sed Con ju ga ted
Oligom er s Dir ected tow a r d Molecu la r Sca le Electr on ic Device
Ap p lica tion s
Ruilian Wu, J effry S. Schumm, Darren L. Pearson, and J ames M. Tour*
Department of Chemistry and Biochemistry, University of South Carolina,
Columbia, South Carolina 29208
Received May 15, 1996X
This paper describes the synthetic organic phase of a project directed toward the construction of
molecular scale electronic devices. Outlined is a convergent synthetic route to orthogonally fused
conjugated organic oligomers. The final systems are to have a potentially conducting chain fused
perpendicularly to a second potentially conducting chain via a σ bonded network. One of the core
segments synthesized is based on a spirobithiophene moiety with a central silicon atom. It is formed
by a zirconium-promoted bis(bicyclization) of a tetrapropargylsilane. The second core is a 9,9′-
spirobifluorene system. Terminal halide groups provide the linkage points for further extension
of the chains via Pd-catalyzed or Pd/Cu-catalyzed cross coupling methods. All four branching arms
are affixed to the core in a single operation, thus making the syntheses highly convergent. In the
cases of the larger functionalized systems, alkyl substituents on the thiophenes afford soluble
materials. In order to prepare the molecules with >50 Å lengths, an iterative divergent/convergent
approach had to be utilized for the construction of oligo(thiophene-ethynylene) branching arms.
Organopalladium-catalyzed procedures are used extensively for the syntheses of the orthogonally
fused compounds.
Since the time of the first room-filling computers, there
has been a tremendous drive to compress the size of
computing instruments. In order to bring this desire to
its extreme, it was conceived that one may be able to
construct single molecules that could each function as a
self-contained electronic device,1 specifically, molecular
scale electronic devices.2 The slow step in existing
computational architectures is often the time it takes for
an electron to travel between any two points. By moving
to very small dimensions, for example, to the molecular
scale, the transmit time would be minimized, hence the
computational system could possibly operate at a far
greater speed than is presently attainable from conven-
tional patterned architectural arrays. There is another
technical advantage that might be gained from molecular
scale devices. Present computational systems utilize
approximately 1010 silicon-based devices. If devices were
to be based upon single molecules, using routine chemical
syntheses, one could prepare over 1023 devices in a single
reaction flask. Though the task of addressing large
arrays of ordered molecular scale devices is presently
unattainable, the potential is exciting.
We recently demonstrated the transport of electrons
through single linear conjugated molecules.1cc,3 Linear
molecules can be considered two-terminal systems or
single molecular wires. The testing of actual molecular
devices, for example transistors where three terminals
are required, remains to be demonstrated due to the
problem of addressing more than two terminals on a
molecular-sized structure. However, we show here that
the synthetic organic protocol exists for the preparation
of the requisite molecular device architectures. The
flexible syntheses of two spiro core systems and the
X Abstract published in Advance ACS Abstracts, September 15, 1996.
(1) For some recent background work on molecular scale electronics,
see: (a) Molecular Electronics: Science and Technology; Aviram, A.,
Ed.; Confer. Proc. No. 262, American Institute of Physics: New York,
1992. (b) Molecular Electronic Devices II; Carter, F. L., Ed.; Marcel
Dekker: New York, 1987. (c) Miller, J . S. Adv. Mater. 1990, 2, 378,
495, 601. (d) Molecular and Biomolecular Electronics; Birge, R. R., Ed.;
Advances in Chemistry Series 240, American Chemical Society, 1991.
(e) Nanostructure Physics and Fabrication; Reed, M. A., Kirk, W. P.,
Eds.; Academic Press: New York, 1989. (f) Nanostructures and
Mesoscopic Systems; Kirk, W. P., Reed, M. A., Eds.; Academic: New
York, 1992. For some background references to molecular wires and
devices, see: (g) Waldeck, D. H.; Beratan, D. N. Science 1993, 261,
576. (h) Grosshenny, V.; Harriman, A.; Ziessel R. Angew. Chem., Int.
Ed. Engl. 1995, 34, 1100. (i) Langler, L.; Stockman, L; Heremans, J .
P.; Bayor, V.; Olk, C. H.; Van Haesendonck, C.; Bruynseraede, Y; Issi,
J .-P. Synth. Met. 1995, 70, 1393. (j) Pascual, J . I.; Me´ndez, J .; Go´mez-
Herrero, J .; Baro´, A. M.; Garcia, N.; Landman, U.; Luedtker, W. D.;
Bogachek, E. N.; Cheng, H.-P. Science 1995, 267, 1793. (k) Purcell, S.
T.; Garcia, N.; Binh, V. T.; J ones, L., II; Tour, J . M. J . Am. Chem. Soc.
1994, 116, 11985. (l) Martin, C. R. Science 1994, 266, 1961. (m) Seth,
J .; Palaniappan, V.; J ohnson, T. E.; Prathapan, S.; Lindsey, J . S.;
Bocian, D. F. J . Am. Chem. Soc. 1994, 116, 10578. (n) Gust, D. Nature
1994, 372, 133. (o) Wu, C.; Bein, T. Science 1994, 266, 1013. (p)
Wagener, R. W.; Lindsey, J . S. J . Am. Chem. Soc. 1994, 116, 9759. (q)
Sailor, M. J .; Curtis, C. L. Adv. Mater. 1994, 6, 688. (r) J orgensen, M.;
Bechgaard, K. J . Org. Chem. 1994, 59, 5877. (s) Brigelletti, F.;
Flamigni, L; Balzani, V.; Collin, J .; Sauvage, J .; Sour, A.; Constable,
E. C.; Thompson, A. M. W. C. J . Am. Chem. Soc. 1994, 116, 7692. (t)
Wu, C.; Bein, T. Science 1994, 264, 1757. (u) Moerner, W. E. Science
1994, 265, 46. (v) Curtis, C. L.; Ritchie, J . E.; Sailor, M. J . Science
1993, 262, 2014. (w) Murphy, C. J .; Arkin, M. R.; J enkins, Y.; Ghatlia,
N. D.; Bossmann, S. H.; Turro, N. J .; Barton, J . K. Science 1993, 262,
1025. (x) O’Neil, M. P.; Niemczyk, M. P.; Svec, W. A.; Gosztola, D.;
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E.; Aviram. A. J . Am. Chem. Soc. 1990, 112, 4206. (bb) Tour, J . M.;
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9529-9534. (cc) J ones, L., II; Pearson, D. L.; Lamba, J . J . S.; Tour, J .
M.; Whitesides, G. M.; Muller C. J .; Reed, M. A. Polym. Prepr. (Am.
Chem. Soc., Div. Polym. Chem.) 1995, 36(1), 564. (dd) Schumm, J . S.;
Pearson, D. L.; Tour, J . M. Angew. Chem., Int. Ed. Engl. 1994, 33,
1360. (ee) Schumm, J . S.; J ones, L., II; Pearson, D. L.; Hara, R.; Tour,
J . M. Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1994, 35(2),
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1994, 27, 2348. (gg) Tour, J . M.; Wu, R.; Schumm. J . S. J . Am. Chem.
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Chem. Soc. 1990, 112, 5662.
(2) One of the troublesome issues in the area of molecular electronics
is simply the definition of “molecular electronics”, since some authors
refer to it as any molecular-based system such as a film or a liquid
crystalline array. Other authors, including us, have preferred to reserve
the term “molecular electronics” for single molecule tasks, such as
single molecule-based transistors. Due to this confusion, we have
chosen here to follow the Petty et al. (Introduction to Molecular
Electronics, Petty, M. C.; Bryce, M. R.; Bloor, D. Eds.; Oxford Univ.
Press: New York, 1995) terminology by using two subcategories,
namely “molecular materials for electronics” for bulk applications and
“molecular scale electronics” for single molecule applications.
(3) Bumm, L. A.; Arnold, J . J .; Cygan, M. T.; Dunbar, T. D.; Burgin,
T. P.; J ones, L., II, Allara, D. L.; Tour, J . M.; Weiss, P. S. Science 1996,
271, 1705.
S0022-3263(96)00897-3 CCC: $12.00 © 1996 American Chemical Society

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6907
convergent attachment of the branching arms are out-
lined. The macromolecules, in one case over 50 Å long,
are of precise length and constitution; there is no random
distribution of chain lengths. Hence, the feasibility of
molecular scale electronic devices may soon be experi-
mentally realized.
Aviram, of the IBM Corporation, suggested that mol-
ecules ∼50 Å long that contain a proconducting (non-
doped or nonoxidized system, hence insulating) chain
that is fixed at a 90° angle via a nonconjugated σ bonded
network to a conducting (doped or oxidized system) chain
should exhibit properties that would make them suitable
for interconnection into future molecular scale electronic
devices. These devices may be useful for the memory,
logic, and amplification computing systems.4 1, in un-
doped form, is an example of a proconducting/σ/conduct-
ing molecule. Addressing is proposed by considering a
between the two arms prior to attainment of the thresh-
old potential across the spiro bridge.5-7 Secondly, all four
conducting chains originating from the central segment
must be identical in length so that the two arms are
degenerate; only distinguishable once in a device.4 These
requirements, along with the need to have no network
polymers formed, prohibit the use of any random poly-
merization methods.
Our initial approach to these systems involved the
synthesis of the key spiro core 2 from which we planned
selective attachment of the four branching chains to the
target molecule 1.1hh A retrosynthetic analysis is shown
in eq 1. Though substitutions on pentaerythrityl tetra-
halides involve reactions on a neopentyl system, exhaus-
six-probe assembly; a probe at each of the four ends, a
probe above the central spiro core moiety, and a probe
below the central spiro moiety. Instrument-induced
electron removal (doping) from the top branch would
permit conduction in the top segment while leaving the
bottom segment unchanged, thus insulating (state 1). At
a certain threshold potential (perturbation) across the
spiro bridge, an electron would tunnel from the lower
chain to upper the chain, via the spiro core, to produce a
doped (conducting) lower chain and a neutral (insulating)
upper chain (state 2).4-6 Thus the two states would be
attainable based on the electrical potential across the
spiro bridge, therefore creating a device. In a previous
study, we demonstrated that we could, electrochemically,
observe the stepwise formation of the mono(radical
cation), bis(radical cation), radical-cation(dication), and
bis(dication) in some of these orthogonally-fused mol-
ecules.7 These results are in accord with the prerequisite
to have no cross-communication between the two arms
under unperturbed conditions, thus supporting the pro-
posal that these types of molecules may permit two
independent states to exist.5,6
tive substitution has been accomplished using oxygen,
nitrogen, and sulfur nucleophiles.8 Formation of 3 using
1-metallo-2-(trimethylsilyl)acetylenes 5 and pentaeryth-
rityl systems 4 (Y ) Br, I, OTs) proved to be unattainable
under numerous coupling procedures (M ) MgBr, Li,
ZnCl, CuBr, Na with and without Pd and Ni catalysis)
in several solvents (THF, diglyme, TMEDA, HMPA, and
DMSO).9 In some cases, we obtained the cyclopropyl
systems 6 and/or 7. Our second proposed route to the
spiro tetraalkyne involved the formation of a tertiary
alcohol, from which we hoped to make the desired
tetraalkyne 3. After investigating numerous reaction
conditions,10 the allenediyne 8 was the only product that
we could obtain cleanly (eq 2).
From the synthetic standpoint, several aspects are
challenging. First, there must be a spiro-fused junction
separating two potentially conducting chains with a
tetrahedral bonding atom at the center to maintain the
90° angle via a σ bonded network. The 90° angle is
essential to minimize the chances of cross-communication
(4) Aviram, A. J . Am. Chem. Soc. 1988, 110, 5687.
(5) For theoretical studies on electron transfer through σ-bridged
compounds, see: (a) McConnell, H. M. J . Chem. Phys. 1961, 35, 508.
(b) Larsson, S.; Volosov, A. J . Chem. Phys. 1986, 85, 2548. (c) J oachim,
C. Chem. Phys. 1987, 116, 339. (d) Reimers, J . R.; Hush, N. S. Chem.
Phys. 1989, 134, 323. (e) Aviram, A.; Ratner, M. A. Chem. Phys. Lett.
1974, 29, 277.
(6) For electron transfer studies on related spiro-fused cores, see:
(a) Krummel, G.; Huber, W.; Mullen, K. Angew. Chem., Int. Ed. Engl.
1987, 26, 1290. (b) Maslak, P.; Augustine, M. P.; Burkey, J . D. J . Am.
Chem. Soc. 1990, 112, 5359. (c) Stein, C. A.; Taube, H. J . Am. Chem.
Soc. 1981, 103, 693. (d) Stein, C. A.; Lewis, N. A.; Seitz, G.; Baker, A.
D. Inorg. Chem. 1983, 22, 1124.
In an effort to bypass these difficulties while maintain-
ing the required σ bonded tetrahedral spiro junction, we
turned our attention to the use of silicon as the central
(8) Padias, A. B.; Hall, H. K., J r.; Tomalia, D. A.; McConnell, J . R.
J . Org. Chem. 1987, 52, 5305. (b) Fujihara, H.; Imaoka, K.; Furukawa,
N. J . Chem. Soc., Perkin Trans. 1 1986, 465.
(7) (a) Diers, J . R.; DeArmond, M. K.; Guay, J .; Diaz, A. Wu, R.;
Schumm, J . S.; Tour, J . M. Chem. Mater. 1994, 6, 327. (b) Guay, J .;
Diaz, A.; Wu, R.; Tour, J . M. J . Am. Chem. Soc. 1993, 115, 1869.
(9) Subsequent to our utilization of this silicon-based approach, a
route to tetrapropargylmethane was disclosed. See: Bunz, U.; Voll-
hardt, K. P. C.; Ho, J . S. Angew. Chem., Int. Ed. Engl. 1992, 31, 1648.

6908 J . Org. Chem., Vol. 61, No. 20, 1996
Wu et al.
Sch em e 1
atom. Since the primary nature of the central bonding
unit is to maintain orthogonality of the two chains
thereby limiting electronic migration between the chains,
silicon should respond much like the initially proposed
carbon analog.4 Our subsequent studies in solution
confirmed this point of interchain isolation.7 Accordingly,
treatment of SiCl4 with the silyl protected propargyl
Grignard reagent, cleanly afforded the tetraalkyne 10.
Treatment of 10 with Negishi’s reagent (n-Bu2ZrCp2),11
generated in situ from zirconocene dichloride and n-
butyllithium, and quenching with 3 N hydrochloric acid
afforded tetraalkene 1112 (Scheme 1). When the zircona-
cycle intermediate was quenched with sulfur monochlo-
ride, the desired spiro bithiophene core 12 was formed.13
The trimethylsilyl-containing core 12 was converted to
the tetrabromide 13 or the tetraiodide 14 under electro-
philic substitution conditions. We eventually chose to use
13 rather than 14 for the subsequent coupling reactions
due to its greater solubility. Additionally, the parent core
system 15 could be obtained by treatment with HI
(Scheme 1). Remarkably, in all of these substitutions,
no attack on the pseudo allylic central silicon atom was
observed.
Likewise, we synthesized another key core segment
based on a poly(p-phenylene)14 conducting unit which fits
the general electronic architectural requirements.1hh
Conversion of 2-aminobiphenyl to the corresponding
iodide under Sandmeyer conditions15 followed by lithium-
halogen exchange and quenching with fluorenone af-
forded the alcohol 16. Acid treatment to generate the
spiro system16 followed by reaction with bromine and
FeCl3 gave the tetrabromo core 17 in excellent yield (eq
3). Bromination occurred only at the positions para to
the second ring in the chain as one would expect by
(10) For the formation of (1-(trimethylsilyl)propargyl)magnesium
bromide, see: Hillard, R. L., III.; Parnell, C. A.; Vollhardt, K. P. C.
Tetrahedron 1983, 39, 905. For the formation of (3-(trimethylsilyl)-
propargyl)aluminum reagents, see: Sondheimer, F.; Amiel, Y.; Gaoni,
Y. J . Am. Chem. Soc. 1962, 84, 270.
(11) (a) Negishi, E. Holmes, S. J .; Tour, J . M.; Miller, J . A.;
Cederbaum, F. E.; Swanson, D. R.; Takahashi, T. J . Am. Chem. Soc.
1989, 111, 3336. (b) Buchwald, S. L.; Nielsen, R. B. Chem. Rev. 1988,
88, 1047.
(12) After our initial use of this bicyclization strategy, a synthesis
of 11 was reported using this protocol. See: Horn, T.; Mu¨llen, K.
Macromolecules 1993, 26, 3472.
(13) (a) Fagan, P. J .; Nugent, W. A. J . Am. Chem. Soc. 1988, 110,
2310. (b) Fagan, P. J .; Nugent, W. A.; Calabrese, J . C. J . Am. Chem.
Soc. 1994, 116, 1880.
(14) For a discussion of polyphenylene, see: (a) Elsenbaumer, R.
L.; Shacklette, L. W. in Handbook of Conducting Polymers, Skotheim,
T. A., Ed.; Dekker: New York, 1986. (b) Tour, J . M. Adv. Mater. 1994,
6, 190.
resonance stabilization of the ionic intermediate. It is
imperative that the bromination take place at the para-
(15) Heaney, H.; Millar, I. T. Org. Synth. 1960, 40, 105.
(16) Clarkson, R. G.; Gomberg, M. J . Am. Chem. Soc. 1930, 52, 2881.

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6909
position since a 4-substituted moiety is essential to afford
a semiconducting or conducting system.14
With the core units in hand, methods for selectively
and equally extending the chains in all four directions
were attempted. Coupling 13 with metalothiophenes
using transition metal catalysis17 could allow for the
selective introduction of all four branching chains in a
single operation. Accordingly, the organometallic re-
agents 19a -c were prepared as described in eq 4.18
trimethylsilyl substituents, for solubility, at the other
end. The synthesis of an appropriately functionalized
terthiophene is shown in eq 7.21 Though 27 could be
formed in high yield, it underwent significant decomposi-
Treatment of 13 with the zinc reagent 19a in the
presence of Pd(PPh3)4 provided the desired product 20
in 11% yield along with much of the homocoupled
bithiophene byproduct.17a,b However, treatment of 13
with the stannane 19b in the presence of catalytic Pd-
(PPh3)4 afforded 20 in 41% yield (eq 5).17c,d When 13 was
treated with the boronic acid 19c under standard aque-
tion on chromatographic purification. Even more frus-
trating was the coupling between 27 and the core 13; red
precipitates, possibly containing the desired product,
were afforded which were insoluble; therefore purification
and analysis were not possible.
ous Suzuki coupling conditions,19 the spiro core was
destroyed; the dimethyl-substituted trimer 21 was af-
forded. Anhydrous conditions for the boron-containing
coupling reactions,20 such as Pd(OAc)2, PPh3, and NEt3
In light of the solubility problems, we turned our
attention to the synthesis of oligo(3-alkylthiophene)s.
Initially, we chose to have a 3-methyl group on every
thiophene unit (eq 8).
in DMF at 100 °C and Pd(PPh3)4 and NEt3 in DME at 80
°C were screened; however, only starting material was
recovered. Additionally, when toluyl organometallic
reagents 22a -c (prepared from the p-bromotoluene by
lithium-halogen exchange followed by transmetalation)
were used for the coupling reaction with 13 under the
same conditions, the yields of 23 were generally less than
20% (eq 6).
In an effort to now extend the length of the branching
units, bromination of the spiro trimer 20 with bromine
in dichloromethane was attempted; however, insoluble
material was obtained which retarded purification and
analysis. Therefore, in order to make the spiro oligomers
with longer branching arms, it was necessary to make
the 2,5-oligothiophenes with stannanes at one end and
(17) (a) Negishi, E.; Baba, S. J . Chem. Soc., Chem. Commun. 1976,
596. (b) Negishi, E.; Takahashi, T.; Baba, S.; Van Horn, D. E.; Okukado,
N. J . Am. Chem. Soc. 1987, 109, 2393. (c) Stille, J . K. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 508. (d) Stille, J . K. Pure Appl. Chem. 1985,
57, 1771.
Though we could cleanly prepare the dimer 31, the
trimer 33 underwent significant amounts of desilylation
to afford 34, and the two trimeric products were insepa-
rable. It was found that the protodesilylation occurred
during the purification by chromatography on silica gel.
(18) Roncali, J . Chem. Rev. 1992, 92, 711.
(19) (a) Miyaura, N.; Yanagi, T.; Suzuki, A. Synth. Commun. 1981,
11, 513. (b) Siddiqui, M. A.; Snieckus, V. Tetrahedron Lett. 1988, 29,
5463. (c) Gronowitz, S.; Lawitz, K. Chem. Scripta 1984, 24, 5.
(20) (a) Moriya, T.; Miyaura, N.; Suzuki. A. Synlett 1994, 149, 304.
(b) Brown, H. C.; Vara Prasad, J . V. N. J . Am. Chem. Soc. 1986, 108,
2049. (c) Miyaura, N.; Ishiyama, T.; Sasaki, H.; Ishikawa, M.; Satoh,
M.; Suzuki, A. J . Am. Chem. Soc. 1989, 111, 314.
(21) For some routes to trimethylsilyl-terminated thiophene oligo-
mers, see: Tour, J . M.; Wu, R. Macromolecules 1992, 25, 1901.

6910 J . Org. Chem., Vol. 61, No. 20, 1996
Wu et al.
Sch em e 2
Even with triethylamine-washed silica gel, the protode-
silylation could not be prevented. Using a triethylsilyl
group instead of a trimethylsilyl moiety through the
above sequence also resulted in protodesilylation of the
trimer. The carbocationic character at the 3-position was
sufficiently stabilized in the trimer (not the monomer or
dimer) by both the â-silicon and R-methyl to allow for
this rapid protodesilylation. tert-Butyldimethylsilyl chlo-
ride (TBDMSCl) was also used for the preparation of
trimer; however, the yield for the formation of the
TBDMS-protected monomer, in the lithium-halogen
exchange step, was only 26%. As a result of these
difficulties, we chose to keep the terminal thiophene unit
nonalkylated which served to prevent the desilylation (eq
9).22
readily showed M+ data in 3-nitrobenzyl alcohol (NBA)
and o-nitrophenyl octyl ether (ONPOE) matrices. This
is an indication of the ease of oxidation of the oligomer
which was confirmed in cyclic voltammetry studies on
41 that showed two redox processes with anodic peak
potentials (Epa) at 0.68 and 1.05 V.7,25
In an effort to make the final orthogonally fused
oligomers with the g50 Å lengths originally proposed by
Aviram,4 we sought several methods to make soluble
hexameric oligothiophenes that were appropriately func-
tionalized. After numerous unsuccessful routes had been
attempted, we finally succeeded in preparing the target
alkyl-substituted hexathiophene (Scheme 2). The cou-
pling of 47 (prepared in situ from 46) to spiro core 13
was attempted; however, the low overall efficiency of the
synthesis of 47, the low yields of the coupling to the spiro
core, and the difficulties in final separation curtailed this
approach to the desired macromolecular spiro-fused
systems.
We then altered our approach to the branching chains
by using an iterative divergent/convergent approach to
make tetra(thiophene-ethynylene) oligomers.1ff The tet-
rameric arms were prepared as described in Scheme 3.
Using this iterative strategy, the branching arms could
be prepared far more efficiently than in our oligothio-
phene approaches. Unfortunately, in an effort to obtain
the desired spiro target 58, reaction of 57 with the spiro
core 13 using Pd/Cu catalysis gave us a repeatedly low
yields (<10%) of the desired product. Significant decom-
position of the core seemed to occur under the basic
conditions needed for the couplings. The low yields
precluded proper analytical confirmation of the structure;
therefore, we turned our attention to the preparation of
the larger fused systems using the spirobifluorene 17.
In preparing orthogonally fused systems based on 17,
we found that cross coupling reactions were useful for
These trimers possess several desired features, namely
(1) a terminal tributylstannyl substituent for attachment
to the core units, (2) alkyl groups for maintaining the
solubility, and (3) a terminal trimethylsilyl group for
solubility enhancement and future chemoselective modi-
fication of the final orthogonal oligomers to permit
adhesion to nanolithographic probes via attachment of
molecular alligator clips (i.e. thiols for attachment to gold
probes).1bb,cc,3
Treatment of the core 13 with excess trimer stannane
40a in the presence of Pd(PPh3)4 afforded the target
orthogonal thiophene system 41 (eq 10). 41 is ap-
proximately 34 Å long as determined by molecular
(23) Oligomer lengths were simulated using standard molecular
modeling procedures. All calculations were performed on a Power
Macintosh 8100/80 AV using Personal CAChe version 3.7 for both
structure drawing and minimization. The CAChe mechanics applica-
tion implements a standard MM2 force field. All energy calculations
were minimized over a large number of iterations to convergence at
local minima nearest in energy to the starting compounds’ energies.
(24) Fenselau, C.; Cotter, R. J . Chem. Rev. 1987, 87, 501.
(25) Recorded with a 1 mm Pt disc working electrode and SCE
double junction reference electrode at a scan rate of 50 mV/s at 10-4
M in dichloromethane using 0.1 M tetrabutylammonium tetrafluo-
roborate as the electrolyte.
modeling using MM2 force field calculations.23 41 is quite
soluble in THF, CH2Cl2, and CHCl3. Interestingly, while
most fast atom bombardment mass spectra (FAB/MS)
resemble chemical ionization spectra in providing pri-
marily even-electron cations or anions (i.e., M + H),24 41
(22) Chan, T. H.; Fleming, I. Synthesis 1979, 761.

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6911
Sch em e 3
the attachment of p-toluyl (22a ) and p-(trimethylsilyl)-
phenyl units to afford 59 and 60 in 70% and 40% yields,
respectively (eq 11).
61 showed M+ data in 3-nitrobenzyl alcohol (NBA) and
o-nitrophenyl octyl ether (ONPOE) matrices.24
In order to enhance the coupling efficiency of the
spirobifluorene core with terminal alkynes, the tetra-
iodospirobifluorene core 62 was prepared. 62 was then
coupled with 2-ethynylthiophene to afford, in excellent
Since p-oligophenylenes are highly insoluble,14 the
synthesis of the larger oligomeric versions based on the
spirobifluorene core would necessitate use of 3-alkyl-
thiophenes as the branching chain units. Alkylated
phenylenes would not be useful since they have inferior
conductivities due to the severe out-of-plane distortions
of the consecutive aryl units.14b Thus 40b was coupled
to the core 17 using Pd(PPh3)4 to afford 61 in 60% yield.
61 is approximately 38 Å long.23 The butyl groups permit
61 to remain quite soluble in THF. Analogous to the
observed FAB/MS behavior for 41 described previously,

6912 J . Org. Chem., Vol. 61, No. 20, 1996
Wu et al.
solvent was removed by distillation through a Vigreux column.
The residue was distilled at 72-74 °C/25 mmHg to afford 7.17
g (75%) of the title product.
yield, 63 (eq 12). We then affixed the larger branching
chains 57 to the core 62 to afford the final target 64 in
78% yield. 64 is 59 Å long.23
Method B: To propargyl alcohol (28.0 g, 29.0 mL, 0.50 mol)
in THF (1 L) was added n-butyllithium (584 mL, 1.05 mol,
1.8 M in hexanes) dropwise by a dropping funnel while
maintaining the internal temperature below -60 °C, and
stirring was continued at this temperature for 0.5 h. Tri-
methylchlorosilane (114 g, 133 mL, 1.05 mol) was added
dropwise by dropping funnel, and the mixture was allowed to
warm to room temperature and stirred for 0.5 h. Hydrochloric
acid (3 N, 600 mL) was added, and the solution was stirred
vigorously for 1 h to deprotect the alcohol. The mixture was
then poured into water and extracted with ether (3 × 100 mL).
The combined organic phase was washed with sodium bicar-
bonate and brine and then dried over sodium sulfate. The
solvent was removed by distillation through a Vigreux column
until the volume was about 700 mL. The flask was cooled to
-78 °C, and n-butyllithium (306 mL, 550 mmol) was added
dropwise by a dropping funnel. The mixture was stirred at
this temperature for 0.5 h, and p-toluenesulfonyl chloride
(104.8 g, 550 mmol) in THF (300 mL) was added dropwise by
a dropping funnel. The mixture was allowed to warm to room
temperature for 1 h and then poured into water and extracted
with ether (3 × 100 mL). The combined organic phase was
washed with brine and dried over sodium sulfate. The solvent
was removed by rotary evaporation. The residue was added
to lithium bromide (87.0 g, 1 mol) in acetone (1 L) at room
temperature and stirred overnight. The solution was poured
into water and extracted with ether (3 × 100 mL), and the
combined organic phase was washed with brine and dried over
sodium sulfate. The solvent was distilled through a Vigreux
column. The residue was distilled at 62.5-64.5 °C/15 mmHg
to afford 55.88 g (59%) of the title product as a colorless liquid.
FTIR (neat) 2960, 2908, 2185, 1412, 1250, 1205, 1040, 850,
These synthetic approaches demonstrated the power
of modern synthetic methods for the preparation of
precisely defined orthogonally fused macromolecular
systems that may be suitable for incorporation into future
molecular scale devices. The convergent approach, where
the core was first synthesized, then the branching arms
were all affixed in a single operation, provided a facile
method for the construction. In order to reach a macro-
molecule with >50 Å length, we had to use an iterative
approach to oligo(thiophene-ethynylene)s which were
used for the branching chains.
Exp er im en ta l Section
Gen er a l. Unless otherwise noted, all operations were
carried out under a dry, oxygen-free nitrogen atmosphere.
Capillary GC analyses were obtained using an Alltech Model
932525 (25 m × 0.25 mm, 0.2 µm film of AT-1 stationary
phase) capillary GC column. 3-Bromothiophene was pur-
chased from Lancaster Synthesis Ltd. and used without
purification. Alkyllithium reagents were obtained from Ald-
rich Chemical Co. Inc. or FMC. Reagent grade diethyl ether
and tetrahydrofuran (THF) were distilled under nitrogen from
sodium benzophenone ketyl. Reagent grade benzene and
dichloromethane were distilled over calcium hydride. Bulk
grade hexane was distilled prior to use. Gravity column
chromatography, silica gel plugs, and flash chromatography
were carried out using silica gel (230-400 mesh from EM
Science). Thin layer chromatography was performed using
glass plates precoated with silica gel 60 F254 with a layer
thickness of 0.25 mm purchased from EM Science. The Pd/
Cu couplings were carried out in a manner analogous to that
described by Suffert.26 The 2-halogenation of 3-alkylthio-
phenes was carried out according to the procedure of Uhlen-
broek and Reinecke.27 The terminal alkynes larger than the
monomer stage were oxidatively unstable, and they were used
immediately after their preparation. Unless otherwise noted,
all compounds were >97% pure as judged by NMR, GC, or
combustion analysis.
760, 705, 640, 620 cm-1
(s, 2 H), 0.15 (s, 9 H).
.
1H NMR (300 MHz, CDCl3) δ 3.88
Tetr a k is(3′-(tr im eth ysilyl)-2′-p r op yn yl)sila n e (10).1hh
To magnesium turnings (0.26 g, 10.5 mmol) and ether (10 mL)
in a 100 mL round bottom flask equipped with a reflux
condenser and magnetic stirring bar was added 3-bromo-1-
(trimethylsilyl)propyne (1.3 g, 7.0 mmol) in ether (6 mL). The
mixture began to reflux within 1 or 2 min and an ice bath was
used to maintain a mild reflux. When the initially vigorous
reaction had subsided, the solution was left to stir at room
temperature for 1 h. The Grignard reagent was then trans-
ferred via cannula to a 100 mL round bottom flask and was
cooled to -78 °C. To this solution was slowly added silicon
tetrachloride (0.17 g, 0.12 mL, 1.0 mmol). The mixture was
allowed to warm to room temperature for 2 h. Water was
carefully added to quench the reaction. The aqueous layer was
extracted with ether, and the combined ether layers were
washed with brine and then dried over anhydrous sodium
sulfate. The solvent was removed by rotary evaporation.
Distillation (200 °C/0.1 mmHg, Kugelrohr) afforded 0.87 g
(90%) of the title compound as a light yellow waxy solid. FTIR
3-Br om o-1-(tr im eth ylsilyl)p r op yn e (9).1hh Method A:
Diisopropylamine (6.1 g, 8.4 mL, 60 mmol) was added over 15
min to a solution of n-butyllithium (23 mL, 60 mmol, 2.6 M in
hexanes) in ether (65 mL) at -78 °C. The obtained solution
was cooled to -80 °C to -90 °C, and propargyl bromide (5.9
g, 3.8 mL, 50 mmol) was added dropwise over 5 min while
keeping the temperature between -75 °C and -80 °C. After
an additional 5 min at -80 °C, chlorotrimethylsilane was
added between -80 and -90 °C. Subsequently, a mixture of
dry HMPA (7.5 mL) and ether (7.5 mL) was added dropwise
with vigorous stirring while carefully keeping the temperature
within this range. After this addition, the cooling bath was
occasionally removed and the temperature was allowed to rise
gradually over 30 min to -40 °C and then to 10 °C. The white
suspension was then poured into 3 N aqueous hydrochloric
acid (500 mL), and the product was extracted with ether. The
combined organic phase was washed with sodium bicarbonate
and brine. After drying over anhydrous sodium sulfate, the
(neat) 2987, 2187, 1251, 845 cm-1
.
1H NMR (300 MHz, CDCl3)
δ 1.93 (s, 8 H), 0.12 (s, 36 H). 13C NMR (20 MHz, CDCl3) δ
102.16 (4 C, alkyne), 84.95 (4 C, alkyne), 2.81 (4 C, CH2), 0.14
(12 C, SiCH3). MS [M+ - CH3] 457, [M+ - TMS] 399, [M+
-
TMSCCCH2] 361. HRMS calcd for C24H44Si5 472.2289,
found: 472.2271.
Com p ou n d 11.12 To a solution of zirconocene dichloride
(0.307 g, 1.05 mmol) in THF (3.5 mL) was added n-butyl-
lithium in hexane (0.75 mL, 2.1 mmol, 2.8 M in hexanes) at
-78 °C. The mixture was stirred for 1 h, and 10 (0.24 g, 0.5
(26) Suffert, J .; Ziessel, R. Tetrahedron Lett. 1991, 32, 757.
(27) (a) Uhlenbroek, J . H.; Bijloo, J . D. Rec. Trav. Chim. 1960, 79,
1181. (b) Reinecke, M. G.; Adickes, H. W.; Pyrn, C. J . Org. Chem. 1971,
36, 2690.

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6913
mmol) in THF (1.5 mL) was added. The reaction mixture was
allowed to warm to room temperature and was stirred for 10
h. The mixture was quenched with 3 N hydrochloric acid and
extracted with ether. The ether extracts were washed with
aqueous sodium bicarbonate and brine and dried over sodium
sulfate. The residue was purified by column chromatography
(silicon gel, hexane) to provide 0.132 g (55%) of the title
compound as a colorless liquid. 1H NMR (300 MHz, CDCl3) δ
5.90 (s, 4 H), 1.81 (d, 8 H, J ) 1.8 Hz), 0.11 (s, 36 H). 13C
NMR (20 MHz, CDCl3) δ 159.44, 122.83, 20.64, -0.29. HRMS
calcd for C24H48Si 476.2602, found 476.2612.
throughout the addition. The resulting brown solution was
stirred for 45 min at 0 °C and then poured into potassium
iodide (4.9 g, 30 mmol) in water (50 mL). The solution was
stirred overnight, and the solution was extracted with ether
(4×). The combined organic layers were washed with 3 N
hydrochloric acid (3 × 10 mL), aqueous sodium bicarbonate,
and brine. After drying over magnesium sulfate, the solvent
was removed in vacuo to afford 3.57 g (85%) of the title
compound as a dark purple liquid. FTIR (neat) 3055.7, 1578.4,
1460.0, 1426.6, 1016.7, 1004.1, 746.9 cm-1
.
1H NMR (300
Sp ir ot et r a k is(t r im et h ylsilyl)b it h iop h en e 12.1hh To a
solution of zirconocene dichloride (0.387 g, 1.15 mmol) in THF
(4.5 mL) was slowly added at -78 °C n-butyllithium (0.89 mL,
2.3 mmol, 2.8 M in hexanes). The mixture was stirred for 1
h, and 10 (0.25 g, 0.52 mmol) in THF (2 mL) was added. The
reaction mixture was allowed to warm to room temperature
and was stirred at this temperature for 1 h. Sulfur monochlo-
ride (0.15 g, 0.088 mL, 1.15 mmol) in hexane (2 mL) was added
dropwise from an addition funnel at 0 °C. The solution was
stirred for 15 min at room temperature before the reaction
was quenched with 3 N hydrochloric acid and extracted with
ether. The combined ether extracts were washed with satu-
rated sodium bicarbonate and dried over sodium sulfate. The
solvent was removed by rotary evaporation. The residue was
purified by column chromatography (silica gel, hexane) to
provide 0.110 g (41%) of the title compound as colorless crystals
MHz, CDCl3) δ 7.95 (dd, J ) 8.1, 1.2 Hz, 1 H), 7.34 (m, 7 H),
7.03 (tt, J ) 7.3, 1.9 Hz, 1 H). 13C NMR (20 MHz, CDCl3) δ
146.3, 143.9, 139.3, 129.9, 129.1, 128.6, 128.0, 127.8, 127.5,
98.6. HRMS calcd for C12H9I 279.9749, found 279.9739.
9-(2′-Bip h en yl)-9-flu or en ol (16).16 To a solution of 2-iodo-
biphenyl (4.93 g, 17.6 mmol) in ether (20 mL) was added at
-78 °C tert-butyllithium (22.8 mL, 38.7 mmol, 1.7 M in
pentane) over 30 min. The resulting slurry was stirred at -78
°C for 1 h, and 9-fluorenone (3.17 g, 17.6 mmol) was added in
ether (15 mL) over 10 min. The solution was warmed to room
temperature for 30 min and poured into water. The aqueous
layer was extracted with ether (3 × 15 mL), and the combined
organic layers were washed with brine and dried over mag-
nesium sulfate. The crude product was recrystallized from
ethanol to afford 5.06 g (86%) of the title product as a white
(dec 198 °C). FTIR (KBr) 2984, 1395, 1252, 1131, 837 cm-1
.
solid. FTIR (KBr) 3590, 3063, 3023, 1450, 1344, 1160 cm-1
.
1H NMR (300 MHz, CDCl3) δ 2.13 (s, 8 H), 0.32 (s, 36 H). 13C
NMR (75 MHz, CDCl3) δ 152.62, 136.81, 15.59, -0.24. HRMS
calcd for C24H44S2Si5 536.1731, found 536.1739.
1H NMR (300 MHz, CDCl3) δ 8.45 (d, J ) 8.0 Hz, 1 H), 7.51
(td, J ) 7.4, 1.5 Hz, 1 H), 7.2-7.1 (m, 1 H), 6.88 (dd, J ) 7.5,
1.4 Hz, 1 H), 6.80 (td, J ) 7.5, 1.3 Hz 1 H), 6.58 (br t, J ) 7.9
Hz, 2 H), 5.98 (dd J ) 8.1, 1.1 Hz, 2 H), 2.2 (s, 1 H).
Sp ir otetr a br om obith iop h en e 13.1hh To a solution of 12
(0.412 g, 0.767 mmol) in carbon tetrachloride (5.0 mL) was
slowly added bromine (0.488 g, 0.156 mL, 3.07 mmol) at 0 °C.
The mixture was allowed to warm to room temperature and
stirred for 40 min before quenching with water. The aqueous
layer was extracted with dichloromethane (4 × 10 mL), and
organic extracts were washed with brine and dried over sodium
sulfate. The solvent was removed by rotary evaporation, and
the product was recrystallized from dichloromethane to provide
0.382 g (88%) of the title compound as colorless crystals. FTIR
9,9′-Sp ir obiflu or en e.16 To a solution of 9-(2′-biphenyl)-9-
fluorenol (11.8 g, 35.3 mmol) in refluxing acetic acid was added
concentrated hydrochloric acid (0.1 mL) and the solution
heated to reflux for 20 min. The solution was cooled to room
temperature, and water (50 mL) was added. The resulting
white solid was filtered and washed with water and dried in
vacuo. No further purification was required to afford 10.9 g
(98%) of the title compound as a white solid. FTIR (KBr)
.
3038.2, 3011.0, 1654.2, 1560.1, 1447.6, 749.3 cm-1 1H NMR
(500 MHz, CDCl3) δ 7.82 (d, J ) 7.7 Hz, 4 H), 7.34 (t, J ) 7.5
Hz, 4 H), 7.08 (t, J ) 7.5 Hz, 4 H), 6.71 (d, J ) 7.6 Hz, 4 H).
(KBr) 1548, 1383, 1309, 1139, 965, 872 cm-1
.
1H NMR (300
MHz, CDCl3) δ 2.08 (s, 8 H). 13C NMR (75 MHz, CDCl3) δ
143.71, 106.06, 16.49. HRMS calcd for C12H8Br4S2Si 561.6550,
found 561.6567. Anal. Calcd for C12H8Br4S2Si: C, 25.55; H,
1.43, found: C, 25.43, 25.35; H, 1.41, 1.45.
2,2′,7,7′-Tetr a br om o-9,9′-sp ir obiflu or en e (17).1hh To a
solution of 9,9′-spirobifluorene (0.316 g, 1.0 mmol) in chloro-
form (1.5 mL) at 0 °C were added ferric chloride (8 mg, 0.05
mmol) and bromine (0.4 mL, 4.1 mmol). The solution was
warmed to room temperature and stirred for 3 h. The
resulting slurry was poured into water and washed with
saturated sodium thiosulfate until the red color disappeared.
The aqueous layer was extracted with dichloromethane (2×),
and the combined organic layers were dried over magnesium
sulfate to afford 0.63 g (100%) of the title product as a white
solid. FTIR (KBr) 3051.6, 1594.7, 1570.8, 1450.1, 1396.2,
Sp ir otetr a iod obith iop h en e 14. To a solution of 12 (0.167
g, 0.31 mmol) in carbon tetrachloride (3.0 mL) was slowly
added iodine monochloride (0.201 g, 0.062 mL, 1.24 mmol) by
syringe at 0 °C. The mixture was stirred at this temperature
for 0.5 h, poured into aqueous sodium thiosulfate solution, and
extracted with dichloromethane. The combined organic ex-
tracts were dried over anhydrous sodium sulfate, and the
solvent was removed at reduced pressure to provide 0.193 g
(83%) of the title product. FTIR (KBr) 3394, 1654, 1384, 1144,
1016, 671, 540 cm-1 1H NMR (300 MHz, CDCl3) δ 2.01 (8 H).
.
13C NMR was not attainable due to the limited solubility.
LRMS calcd for C12H8I4S2Si 752, found 752.
1249.3, 1059.7, 950.6 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.67
Sp ir obith iop h en e 15. To a solution of 12 (0.079 g, 0.147
mmol) in benzene (4.00 mL) was added hydriodic acid (0.038
g, 0.08 mL, 0.294 mmol, 48.8% in water) dropwise at room
temperature, and the mixture was stirred at room temperature
for 1.5 h. Saturated sodium bicarbonate was added, and the
mixture was extracted with ether. The organic extracts were
washed with brine and dried over sodium sulfate. The solvent
was removed by rotary evaporation. The residue was purified
by preparative TLC to provide 0.030 g (82%) of the title product
as colorless crystals. FTIR (KBr) 3105, 2885, 1397, 1348, 1165,
(d, J ) 8.4 Hz, 4 H), 7.5 (dd, J ) 8.2, 1.8 Hz, 4 H), 6.8 (d, J )
1.5 Hz, 4 H). 13C NMR (75 MHz, CD2Cl2) δ 149.3, 140.2, 132.1,
127.7, 122.4, 122.3, 65.7. HRMS calcd for C25H12Br4 631.7632,
found 631.7630. Anal. Calcd for C25H12Br4: C, 47.51; H, 1.91,
found: C, 47.01; H, 1.97. The position of the bromide was
confirmed by a single crystal X-ray structure of the title
compound. 2D-NMR with a 500 MHz probe was not sufficient
to provide the connectivity of the system due to the unusually
long relaxation time of the central carbon atom. The relax-
ation time could not be sufficiently increased even with
chromium acetoacetonate. Cooling of the sample to shorten
the relaxation time caused precipitation, hence, insufficient
signal.
1127, 813 cm-1
.
1H NMR (300 MHz, CDCl3) δ 6.90 (s, 4 H),
2.10 (s, 8 H). 13C NMR (20 MHz, CDCl3) δ 143.45, 118.45,
14.14. Anal. Calcd for C12H12S2Si: C, 58.00; H, 4.87. Found:
C, 57.57; H, 4.92.
2-Iod obip h en yl.15 To a solution of 2-aminobiphenyl (2.53
g, 15.0 mmol) in concentrated hydrochloric acid (3 mL) and
water (15 mL) at 0 °C was added sodium nitrite (1.17 g, 17.0
mmol) in water (5 mL). The temperature was held at 0 °C
2-Br om o-5-(tr im eth ylsilyl)th iop h en e (18).21 To a solu-
tion of n-butyllithium (7.41 mL, 12 mmol, 1.62 M in hexanes)
in THF (10.0 mL) was added dropwise at -78 °C diisopropyl-

6914 J . Org. Chem., Vol. 61, No. 20, 1996
Wu et al.
amine (1.42 g, 1.96 mL, 14 mmol). The mixture was warmed
to 0 °C for 5 min and then recooled to -78 °C. 2-Bro-
mothiophene (1.63 g, 0.97 mL, 10 mmol) was added, and the
solution was warmed to 0 °C for 5 min. After recooling to -78
°C, chlorotrimethylsilane (1.30 g, 1.52 mL, 12 mmol) was added
in one portion, and the solution was allowed to warm to room
temperature for 30 min. The mixture was poured into water
with a few drops of 3 N hydrochloric acid to remove the
emulsion, and the aqueous layer was extracted with ether. The
organic extracts were washed with sodium bicarbonate and
brine. After drying over sodium sulfate, the solvent was
removed by rotary evaporation. Vacuum distillation (70 °C/2
mmHg) afforded 1.8 g (77%) of the title product as a colorless
liquid. FTIR (neat) 2957, 1406, 1288, 1251, 1204, 1068, 1001,
MHz, CDCl3) δ 7.29 (d, J ) 3.51 Hz, 4 H), 7.18 (d, J ) 3.51
Hz, 4 H), 2.33, (s, 8 H), 0.35 (s, 36 H). 13C NMR (75 MHz,
CDCl3) δ 142.54, 140.87, 139.51, 134.40, 128.31, 125.10, 16.71,
0.00. Anal. Calcd for C40H52S6Si5: C, 55.50; H, 6.05. Found:
C, 55.09, 54.99; H, 6.03, 6.04. HRMS calcd for C40H52S6Si5
864.1219, found 864.1240.
Com p ou n d 23. To a solution of 4-bromotoluene (1.368 g,
0.984 mL, 8.0 mmol) in anhydrous ether (15 mL) was slowly
added tert-butyllithium (9.41 mL, 16 mmol, 1.7 M in pentane)
by syringe pump (0.20 mL/min) at -78 °C. The solution was
stirred at -78 °C for 1 h and was added via cannula to a
solution of anhydrous zinc chloride (1.53 g, 11.2 mmol) in THF
(10 mL). The mixture was stirred at room temperature for 1
h. To a solution of 13 (0.282 g, 0.5 mmol) in THF (2.5 mL)
956, 841, 796, 756, 697, 648 cm-1
.
1H NMR (300 MHz, CDCl3)
was added
a solution of tetrakis(triphenylphosphine)pal-
δ 7.06 (d, J ) 3.49 Hz, 1 H), 6.97 (d, J ) 3.49 Hz, 1 H), 0.28
(s, 9 H). 13C NMR (20 MHz, CDCl3) δ 143.05, 134.31, 131.11,
116.72, -0.20.
ladium(0), formed in situ by stirring Pd2dba3CHCl3 (0.015 g,
0.014 mmol) and triphenylphosphine (0.026 g, 0.10 mmol) in
THF (2.5 mL). To this solution was added the zinc reagent
by cannula, and the mixture was stirred at room temperature
for 1 h followed by warming at 60 °C (bath temperature)
overnight. The solution was poured onto water and was
extracted with dichloromethane. The combined organic ex-
tracts were washed with brine and dried over sodium sulfate,
and the solvent was removed in vacuo. The residue was
dissolved in dichloromethane and filtered through a silica gel
plug, and the solvent was removed in vacuo. The residue was
then dissolved in carbon tetrachloride and was purified by
chromatography (silica gel, hexane, 1:20 dichloromethane:
hexane, 1:10 dichloromethane:hexane, 1:5 dichloromethane:
hexane) to provide 57 mg (18%) of the title compound as white
crystals. FTIR (KBr) 2918, 1504, 1387, 1262, 1138, 1011, 813,
2-(Tr ibu tylstan n yl)-5-(tr im eth ylsilyl)th ioph en e (19b).21
To a solution of tert-butyllithium (20.0 mL, 33.6 mmol, 1.68
M in pentane) in ether (18.0 mL) was added slowly at -78 °C
2-bromo-5-(trimethylsilyl)thiophene (18) (3.95 g, 16.8 mmol),
and the resulting mixture was stirred at -78 °C for 1 h. To
this mixture was added slowly tributyltin chloride (5.47 g, 4.56
mL, 16.8 mmol), and the solution was allowed to warm to room
temperature for 2 h before pouring into water with a few drops
of 3 N hydrochloric acid to remove the emulsion. The aqueous
layer was extracted with ether. The organic extracts were
washed with sodium bicarbonate and brine and dried over
sodium sulfate. The solvent was removed by rotary evapora-
tion, and the crude material was filtered through a silica plug
(hexane) to provide 5.84 g (78%) of the title product as a
colorless liquid which was used with no further purification.
FTIR (neat) 2957, 2928, 1485, 1464, 1406, 1377, 1249, 1214,
758, 579 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.50 (d, J ) 8.2
Hz, 8 H), 7.17 (d, J ) 8.0 Hz, 8 H), 2.35 (s, 12 H), 2.26 (s, 8 H).
13C NMR (20 MHz, CDCl3) δ 140.03, 136.69, 132.23, 129.31,
127.40, 21.16, 15.91.
1200, 1082, 992, 840, 800, 757, 704 cm-1
.
1H NMR (300 MHz,
CDCl3) δ 7.46 (d, J ) 3.1 Hz, 1 H), 7.32 (d, J ) 3.1 Hz, 1 H),
1.60 (q, J ) 8.0 Hz, 6 H), 1.47-1.17 (m, 12 H), 0.96 (t, J ) 7.3
Hz, 9 H), 0.39 (s, 1 H). 13C NMR (20 MHz, CDCl3) δ 145.71,
142.07, 136.18, 134.77, 29.05, 27.33, 13.65, 10.93, 0.21.
2-(Tr im eth ylsilyl)-5-th ien ylbor on ic a cid (19c).21 To a
solution of tert-butyllithium (3.53 mL, 6.0 mmol, 1.7 M in
pentane) in ether (3.0 mL) was added 2-bromo-5-(trimethyl-
silyl)thiophene (18) (0.706 g, 3.0 mmol) in ether (3.0 mL) at
-78 °C. The mixture was stirred at -78 °C for 1 h and
transferred via cannula to a solution of triisopropyl borate
(1.128 g, 1.38 mL, 6.0 mmol) in THF (2.0 mL) at -78 °C. The
mixture was allowed to warm to room temperature and stirred
for 10 min. Hydrochloric acid (5%, 2.0 mL) was added, and
the aqueous layer was extracted with ether. The organic
extracts were washed with 1 N sodium hydroxide (4 × 10 mL).
The sodium hydroxide solution was washed with ether, and
the aqueous solution was then acidified with 3 N hydrochloric
acid and then extracted with ether. The combined organic
extracts were dried over magnesium sulfate. The solvent was
removed under reduced pressure to provide 0.422 g (70%) of
the title product as a off-white thick liquid which was used
directly for the next reaction. FTIR (neat) 3354, 2957, 1506,
2,2′-Bith iop h en e (24).21 To magnesium turnings (0.912 g,
37.5 mmol) in ether (15.0 mL) was added about 0.5 mL of
2-bromothiophene (4.076 g, 2.42 mL, 25 mmol). An exothermic
reaction occurred within a few minutes, and the remaining
bromide was added dropwise with an ice bath used occasionally
to maintain a mild reflux. After the addition, the resulting
mixture was heated to reflux for 30 min and cooled to room
temperature. To a solution of 2-bromothiophene (3.26 g, 1.94
mL, 20 mmol) and [1,3-bis(diphenylphosphino)propane]-
nickel(II) chloride (15 mg) in ether (10.0 mL) was added
dropwise via cannula the above Grignard reagent at 0 °C. The
resulting mixture was heated to reflux for 4 h and poured into
water with a few drops of 3 N hydrochloric acid to destroy the
emulsion. The aqueous layer was extracted with ether, and
the organic extracts were washed with sodium bicarbonate and
brine and dried over sodium sulfate. The solvent was removed
by rotary evaporation, and the residue was purified by column
chromatography (silica gel, hexane) to afford 3.32 g (99.8%)
of the title product as a colorless liquid. FTIR (neat) 3064,
1794, 1649, 1500, 1416, 1238, 1208, 1078, 1051, 856, 817, 704
cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.20 (dd, J ) 5.1, 1.2 Hz,
2 H), 7.17 (dd, J ) 3.6, 1.2 Hz, 2 H), 7.01 (dd, J ) 5.1, 3.6 Hz,
2 H).
1344, 1250, 1119, 1072, 987, 841, 756, 715, 636 cm-1
.
1H NMR
2-Br om o-5-(2′-th ien yl)th iop h en e (25).28 A flame-dried
flask was charged with 2,2′-bithiophene (24) (1.66 g, 10.0
mmol), N-bromosuccinimide (1.78 g, 10.0 mmol), chloroform
(20.0 mL), and acetic acid (20.0 mL). The mixture was stirred
at room temperature under N2 overnight and then washed
several times with aqueous sodium bicarbonate and brine. The
aqueous layer was extracted with ether, and the organic
extracts were dried over sodium sulfate. The solvent was
removed by rotary evaporation, and the residue was purified
by column chromatography (silica gel, hexane) to provide 1.62
g (66%) of the title product as a light-blue liquid along with
0.43 g (13%) of dibromide and 0.177 g of the starting material.
FTIR (neat) 3084, 1737, 1504, 1443, 1418, 1241, 1200, 1051,
(CDCl3, 300 MHz) δ 8.04 (d, J ) 3.3 Hz, 2 H), 7.40 (d, J ) 3.3
Hz, 2 H), 0.37 (s, 9 H).
Com p ou n d 20.1hh A flame-dried flask was sequentially
charged with 13 (0.282 g, 0.5 mmol), 2-(tributylstannyl)-5-
(trimethylsilyl)thiophene (19b) (1.78 g, 4.0 mmol), tetrakis-
(triphenylphosphine)palladium(0) (0.115 g, 0.10 mmol), and
toluene (9.0 mL). The mixture was stirred at room tempera-
ture for 1 h and heated to 100 °C for 20 h. The resulting
solution was poured into water with a few drops of 3 N
hydrochloric acid to remove the emulsion, and the organic layer
was separated. The aqueous layer was extracted with ether,
and the combined organic extracts were washed with sodium
bicarbonate and brine and dried over magnesium sulfate. The
crude material was filtered through alumina to remove the
palladium residue and then was purified by column chroma-
tography (silica gel, hexane) to provide 0.177 g (41%) of the
title product as yellow-green crystals. FTIR (KBr) 2955, 1431,
970, 882, 838, 789, 696 cm-1
.
1H NMR (CDCl3, 300 MHz) δ
7.21 (dd, J ) 5.1, 1.2 Hz, 1 H), 7.09 (dd, J ) 3.6, 1.2 Hz, 1 H),
(28) Nakayama, J .; Konishi, T.; Murabayashi, S.; Hoshino, M.
Heterocycles 1987, 26, 1793.
1249, 1208, 1130, 1076, 983, 841, 799, 757 cm-1
.
1H NMR (300

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6915
6.99 (dd, J ) 5.1, 3.6 Hz, 1 H), 6.95 (d, J ) 3.8 Hz, 1 H), 6.90
(d, J ) 3.8 Hz, 1 H).
1 H), 2.34 (s, 3 H), 0.32 (s, 9 H). 13C NMR (20 MHz, CDCl3) δ
144.60, 132.66, 131.83, 129.10, 16.43, -0.03.
5-(Tr im eth ylsilyl)-2,2′:5′,2′′-ter th iop h en e (26). A flame-
dried flask was charged with 2-(tributylstannyl)-5-(trimeth-
ylsilyl)thiophene (19b) (4.41 g, 9.9 mmol), 2-bromo-5-(2′-
thienyl)thiophene (25) (1.66 g, 6.6 mmol), tetrakis(triphen-
ylphosphine)palladium(0) (0.38 g, 0.33 mmol), and toluene
(30.0 mL). The mixture was heated to 100 °C (oil temp)
overnight under N2 and poured into water with a few drops of
3 N hydrochloric acid to destroy the emulsion. The aqueous
layer was extracted with ether, and the organic extracts were
washed with sodium bicarbonate and brine and then dried over
sodium sulfate. The solvent was removed by rotary evapora-
tion, and the residue was purified by column chromatography
(silica gel, hexane) to provide 1.78 g (84%) of the title product
as bright-yellow crystals. FTIR (KBr) 1426, 1253, 1076, 994,
2-(T r i m e t h y ls i ly l)-3-m e t h y l-5-(t r i b u t y ls t a n n y l)-
th iop h en e (30).21 To a solution of diisopropylamine (0.511
g, 0.71 mL, 5.05 mmol) in THF (5.0 mL) was added dropwise
n-butyllithium (2.38 mL, 5.05 mmol, 2.12 M in hexanes) at
-78 °C. The mixture was warmed to 0 °C for 10 min and
recooled to -78 °C, and 29 (0.86 g, 5.05 mmol) in THF (5.0
mL) was added dropwise via cannula. The mixture was stirred
at this temperature for 30 min, tributyltin chloride (1.64 g,
1.37 mL, 5.05 mmol) was added dropwise, and the mixture
was allowed to warm to room temperature for 2 h and then
poured into water. The aqueous layer was extracted with
ether, and the organic extracts were washed with brine and
dried over sodium sulfate. The solvent was removed by rotary
evaporation, and the residue was purified by column chroma-
tography (silica gel washed with 10% triethylamine in hexane,
hexane eluent) to provide 1.97 g (85%) of the title product as
a colorless liquid. FTIR (neat) 2957, 1464, 1376, 1316, 1250,
835, 794, 754, 684, 468 cm-1
.
1H NMR (CDCl3, 300 MHz) δ
7.21 (d, J ) 3.5 Hz, 1 H), 7.20 (dd, J ) 5.1, 1.2 Hz, 1 H), 7.16
(dd, J ) 3.6, 1.2 Hz, 1 H), 7.12 (d, J ) 3.5 Hz, 1 H), 7.07 (d, J
) 0.5 Hz, 2 H), 7.00 (dd, J ) 5.1, 3.6 Hz, 1 H), 0.32 (s, 9 H).
1053, 839, 754 cm-1 1H NMR (300 MHz, CDCl3) δ 7.04 (s, 1
.
H), 2.39 (s, 3 H), 1.58 (m, 6 H), 1.36 (m, 6 H), 1.10 (m, 6 H),
0.90 (t, 9 H), 0.35 (s, 9 H). 13C NMR (20 MHz, CDCl3) δ 145.45,
141.10, 140.23, 138.76, 28.99, 27.29, 16.12, 13.63, 10.86, 0.11.
5-(Tr im eth ylsilyl)-5′′-(tr im eth ylsta n n yl)-2,2′:5′,2′′-ter -
th iop h en e (27). To a solution of diisopropylamine (0.304 g,
0.42 mL, 3.0 mmol) in THF (2.0 mL) was added n-butyllithium
(1.34 mL, 3.0 mmol, 2.24 M in hexanes) dropwise at -78 °C.
The mixture was allowed to warm to 0 °C for 10 min and
recooled to -78 °C. To the above solution was added dropwise
26 (0.641 g, 2.0 mmol) in THF (2.0 mL) via cannula. The
resulting mixture was stirred at this temperature for 2 h, and
trimethyltin chloride (0.73 g, 3.66 mmol) in THF (2.0 mL) was
added dropwise via cannula. The solution was allowed to
warm to room temperature for 1 h and poured into brine. The
aqueous layer was extracted with ether, and the organic
extracts were dried over sodium sulfate. The solvent was
removed by rotary evaporation to provide quantitatively the
title product as deep-green crystals. NMR analysis of the
crude product indicated that virtually pure product was
formed. The compound darkened during workup and decom-
posed to starting material when it was purified by column
chromatography (silica gel, hexane). FTIR (KBr) 1249, 1200,
3′,4-Dim eth yl-5-(tr im eth ylsilyl)-2,2′-bith iop h en e (31).21
A flame-dried flask was charged with 30 (1.89 g, 4.11 mmol),
28 (0.728 g, 4.11 mmol), bis(triphenylphosphine)palladium(II)
chloride (0.144 g, 0.20 mmol), triphenylphosphine (0.052 g, 0.20
mmol), and toluene (20.0 mL). The mixture was stirred at
room temperature for 4 h, warmed to 100 °C for 4 h, and then
poured into saturated ammonium chloride. The aqueous layer
was extracted with ether, and the organic extracts were
washed with brine and dried over sodium sulfate. The solvent
was removed by rotary evaporation, and the residue was
purified by column chromatography (silica gel, hexane) to
provide 0.727 g (66%) of the title product as a light-green
liquid. FTIR (neat) 2955, 1401, 1250, 1057, 839, 755, 705 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.09 (d, J ) 5.1 Hz, 1 H), 7.00
(s, 1 H), 6.85 (d, J ) 5.1 Hz, 1 H), 2.38 (s, 3 H), 2.32 (s, 3 H),
0.34 (s, 9 H).
985, 9432, 910, 841, 794, 538, 476 cm-1 1H NMR (300 MHz,
.
2-(Tr ib u t ylst a n n yl)-3,4′-d im et h yl-5′-(t r im et h ylsilyl)-
2,2′-bith iop h en e (32).21 To a solution of diisopropylamine
(0.536 g, 0.74 mL, 5.3 mmol) in THF (4.0 mL) was added
dropwise n-butyllithium (2.5 mL, 5.3 mmol, 2.12 M in hexanes)
at -78 °C. The mixture was warmed to 0 °C for 10 min and
was recooled to -78 °C, 31 (1.42 g, 5.3 mmol) in THF (4.0 mL)
was added dropwise via cannula, and the mixture was stirred
at this temperature for 0.5 h. Tributyltin chloride (1.73 g, 1.44
mL, 5.3 mmol) was added dropwise, and the mixture was
allowed to warm to room temperature for 2 h. The mixture
was poured into water, and the aqueous layer was extracted
with ether. The organic extracts were washed with brine and
dried over sodium sulfate. The solvent was removed by rotary
evaporation, and the residue was filtered through a silica plug
washed with 10% triethylamine using hexane to provide 2.72
g (93%) of the title product as a light-green liquid. FTIR (neat)
CDCl3) δ 7.26 (d, J ) 3.4 Hz, 1 H), 7.20 (d, J ) 3.4 Hz, 1 H),
7.07 (d, J ) 3.4 Hz, 1 H), 7.05 (d, J ) 1.8 Hz, 2 H), 0.37 (s, 9
H), 0.31 (s, 9 H). 13C NMR (20 MHz, CDCl3) δ 142.63, 142.22,
139.82, 136.39, 135.95, 135.89 (2 C), 134.74, 124.85, 124.79,
124.37, 124.15, -0.14, -8.25.
2-Br om o-3-m eth ylth iop h en e (28).21 To a solution of
3-methylthiophene (7.20 g, 7.07 mL, 73.3 mmol) in dioxane
(36.0 mL) was added dropwise with magnetic stirring bromine
(11.72 g, 3.76 mL, 73.3 mmol) in dioxane (72.0 mL) at room
temperature. The mixture was stirred at this temperature for
4 h and poured into water. The aqueous layer was extracted
with ether, and the organic extracts were washed with 1 N
sodium hydroxide and brine and dried over sodium sulfate.
The solvent was removed by distillation, and the residue was
distilled at 66-69 °C (17 mmHg) to provide 10.3 g (79%) of
the title product as a colorless liquid. FTIR (neat) 2922, 1546,
2956, 1464, 1250, 1059, 839 cm-1 1H NMR (300 MHz, CDCl3)
.
1407, 1230, 991, 923, 827, 700 cm-1
.
1H NMR (300 MHz,
δ 6.99 (s, 1 H), 6.88 (s, 1 H), 2.39 (s, 3 H), 2.31 (s, 3 H), 1.53
CDCl3) δ 7.18 (d, J ) 5.5 Hz, 1 H), 6.80 (d, J ) 5.5 Hz, 1 H),
2.25 (s, 3 H). 13C NMR (20 MHz, CDCl3) δ 136.91, 129.02,
124.83, 109.13, 14.91.
(m, 6 H), 1.32 (m, 6 H), 1.07 (t, 6 H), 0.88 (t, 9 H), 0.33 (s, 9
H).
2-Iod o-5-(tr im eth ylsilyl)th iop h en e (35).21 To a solution
of 2-bromo-5-(trimethylsilyl)thiophene (18) (17.96 g, 76.4
mmol) in ether (100 mL) at -78 °C was added dropwise
n-butyllithium (30.81 mL, 76.4 mmol, 2.48 M in hexanes). The
mixture was stirred at -78 °C for 1 h, iodine (19.39 g, 76.4
mmol) in ether (100 mL) was added dropwise, and the mixture
was allowed to warm to room temperature. The solution was
poured into water and extracted with ether. The organic
extracts were washed with brine and dried over sodium
sulfate. The solvent was removed by rotary evaporation to
provide 20.91 g (97%) of the title product as a pale-red liquid
that was virtually pure by spectroscopic analysis and used
without purification. FTIR (neat) 2956, 1397, 1250, 1202,
2-(Tr im eth ylsilyl)-3-m eth ylth iop h en e (29).21 To a solu-
tion of 2-bromo-3-methylthiophene (28) (3.54 g, 20 mmol) in
ether (50.0 mL) was added dropwise n-butyllithium (9.4 mL,
20 mmol, 2.12 M in hexanes) at -78 °C. The mixture was
stirred at this temperature for 20 min, chlorotrimethylsilane
(3.26 g, 3.8 mL, 30 mmol) was added dropwise, and the
resulting mixture was allowed to warm to room temperature
and then poured into water. The aqueous layer was extracted
with ether and the organic extracts were washed with brine
and dried over sodium sulfate. The solvent was removed by
rotary evaporation, and the residue was purified by column
chromatography (silica gel, hexane) to provide 3.29 g (96%)
the title compound as a colorless liquid. FTIR (neat) 2957,
1067, 991, 841, 796, 756 cm-1 1H NMR (300 MHz, CDCl3) δ
.
1392, 1251, 1099, 1028, 839, 756, 714 cm-1
.
1H NMR (300
7.24 (d, J ) 3.40 Hz, 1 H), 6.90 (d, J ) 3.44 Hz, 1 H) 0.28 (s,
MHz, CDCl3) δ 7.42 (d, J ) 4.6 Hz, 1 H), 6.97 (d, J ) 4.6 Hz,
9 H).

6916 J . Org. Chem., Vol. 61, No. 20, 1996
Wu et al.
3-Bu tylth iop h en e.1gg To magnesium turnings (1.82 g, 75
mmol) in ether (20.0 mL) was added dropwise 1-bromobutane
(10.3 g, 75 mmol) in ether (20.0 mL) at room temperature, and
an ice bath was used occasionally to maintain a mild reflux.
The mixture was stirred at room temperature for 1 h and
transferred via cannula to a solution of 3-bromothiophene (8.15
g, 50 mmol) and [1,3-bis(diphenylphosphino)propane]nickel(II)
chloride (30 mg, 0.055 mmol) in ether (20.0 mL) at 0 °C. The
mixture was then allowed to warm to room temperature and
stirred overnight before being poured into water with a few
drops of 3 N hydrochloric acid. The aqueous layer was
extracted with ether, and the organic extracts were washed
with brine and dried over magnesium sulfate. The solvent was
removed by rotary evaporation, and the residue was purified
by column chromatography (silica gel, hexane) to provide 5.93
g (85%) of the title product as a colorless liquid. FTIR (neat)
mixture was allowed to warm to room temperature and stirred
overnight before being poured into water with a few drops of
3 N hydrochloric acid. The aqueous layer was extracted with
ether, and the organic extracts were washed with brine and
dried over magnesium sulfate. The solvent was removed by
rotary evaporation, and the residue was purified by column
chromatography (silica gel, hexane) to provide 1.89 g (64%) of
the title product as a colorless liquid which was estimated to
be ca. 80% pure. FTIR (neat) 2956, 1444, 1250, 1069, 991,
840, 756 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.15 (m, 3 H),
6.91 (d, J ) 5.17 Hz, 1 H), 2.75 (t, J ) 7.79 Hz, 2 H), 1.61 (p,
J ) 7.40 Hz, 2 H), 1.37 (sext, J ) 7.43 Hz, 2 H), 0.91 (t, J )
7.30 Hz, 3 H).
5-Iod o-3-m e t h yl-2-(5′-(t r im e t h ylsilyl)t h ie n yl)t h io-
p h en e (38a ).21 To a solution of diisopropylamine (0.401 g,
0.56 mL, 3.96 mmol) in THF (5.0 mL) was added dropwise
n-butyllithium (1.60 mL, 3.96 mmol, 2.48 M in hexanes) at
-78 °C. The mixture was warmed to 0 °C for 5 min and then
recooled to -78 °C. 3-Methyl-2-(5′-(trimethylsilyl)thienyl)-
thiophene (37a ) (1.00 g, 3.96 mmol) in THF (50 mL) was added
dropwise, and the solution stirred at -78 °C for 1 h. Iodine
(1.01 g, 3.96 mmol) in THF (5.0 mL) was added dropwise, and
the solution was allowed to warm to room temperature for 30
min. The mixture was poured into water, and the aqueous
layer was extracted with ether. The organic extracts were
washed with brine and dried over sodium sulfate. The solvent
was removed by rotary evaporation, and the residue was
virtually pure by spectroscopic analysis and used without
purification. 1H NMR (300 MHz, CDCl3) δ 7.14 (d, J ) 3.47
Hz, 1 H), 7.11 (d, J ) 3.42 Hz, 1 H), 7.01 (s, 1 H), 2.34 (s, 3 H),
0.32 (s, 9 H).
2929, 2859, 1466, 1079, 857, 834, 768 cm-1
.
1H NMR (300
MHz, CDCl3) δ 7.23 (m, 1 H), 6.91 (m, 2 H), 2.62 (t, J ) 7.62
Hz, 2 H), 1.60 (p, J ) 7.58 Hz, 2 H), 1.32 (sext, J ) 7.38 Hz,
2 H), 0.92 (t, J ) 7.32 Hz, 3 H).
2-Iod o-3-m eth ylth iop h en e (36a ).21 To a solution of 3-me-
thylthiophene (9.8 g, 100 mmol) in benzene (20.0 mL) were
added (alternately, in small portion) mercuric oxide (20 g, 92.5
mmol, yellow) and iodine (26 g, 102.5 mmol) at 0 °C. The
mixture was stirred at room temperature for 0.5 h, and the
precipitate was filtered and washed with ether. The filtrate
and washings were washed with aqueous sodium thiosulfate
and dried over sodium sulfate. The solvent was removed by
rotary evaporation to provide 21.15 g (94%) of the title product
as a pale-red liquid which that virtually pure without further
purification. FTIR (neat) 2918, 1396, 1227, 967, 916, 825, 703
cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.33 (d, J ) 5.4 Hz, 1 H),
6.74 (d, J ) 5.4 Hz, 1 H), 2.21 (s, 3 H).
2-(5′-(Tr im et h ylsilyl)t h ien yl)-3-m et h yl-5-(t r im et h yl-
sta n n yl)th iop h en e. To a solution of diisopropylamine (0.494
g, 0.68 mL, 4.88 mmol) in THF (5.0 mL) was added dropwise
n-butyllithium (4.03 mL, 4.88 mmol, 1.21 M in hexanes) at
-78 °C. The mixture was warmed to 0 °C for 10 min and then
recooled to -78 °C. 2-(5′-(Trimethylsilyl)thienyl)-3-methylthio-
phene (37a ) (0.822 g, 3.26 mmol) in THF (3.0 mL) was added
dropwise via cannula. The mixture was stirred at this
temperature for 2 h, and trimethyltin chloride (0.97 g, 4.88
mmol) in THF (3.0 mL) was added via cannula. The mixture
was warmed to room temperature for 0.5 h and poured into
water. The aqueous layer was extracted with ether, and the
organic extracts were washed with brine and dried over sodium
sulfate. The solvent was removed by rotary evaporation to
provide 1.35 g (100%) of the title product as a thick yellow oil.
FTIR (neat) 2956, 1440, 1250, 1192, 1072, 991, 907, 840, 771
3-Bu tyl-2-iod oth iop h en e (36b).1gg To a solution of 3-bu-
tylthiophene (5.89 g, 42 mmol) in benzene (10.0 mL) was
alternately added mercuric oxide (8.41 g, 38.9 mmol, yellow)
and iodine (10.93 g, 43.1 mmol) in small portions at 0 °C. The
mixture was stirred at room temperature overnight before
filtration. The filtrate was poured into water, the aqueous
layer was extracted with ether, and the organic extracts were
washed with brine and dried over magnesium sulfate. The
solvent was removed by rotary evaporation, and the residue
was purified by column chromatography (silica gel, hexane)
to provide 8.06 g (72%) of the title product as a colorless liquid.
FTIR (neat) 2929, 2857, 2361, 1464, 1398, 966, 829, 715 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.36 (d, J ) 5.51 Hz, 1 H), 6.73
(d, J ) 5.46 Hz, 1 H), 2.48 (t, J ) 7.63 Hz, 2 H), 1.54 (p, J )
7.70 Hz, 2 H), 1.35 (sext, J ) 7.29 Hz, 2 H), 0.93 (t, J ) 7.21
Hz, 2 H).
cm-1
.
1H NMR (300 Hz, CDCl3) δ 7.16 (s, 2 H), 6.94 (s, 1 H),
2.40 (s, 3 H), 0.35 (s, 9 H), 0.32 (s, 9 H).
3-Meth yl-2-(5′-(tr im eth ylsilyl)th ien yl)th ioph en e (37a).21
To magnesium turnings (0.93 g, 38.3 mmol) in ether (15.0 mL)
was added dropwise 2-iodo-3-methylthiophene (36a ) (5.71 g,
25.5 mmol) at 0 °C. The mixture was stirred for 2 h at room
temperature and was transferred to a solution of 2-bromo-5-
(trimethylsilyl)thiophene (18) (3.95 g, 17.0 mmol), and (1,3-
bis(diphenylphosphino)propane)nickel(II) chloride (0.461 g,
0.85 mmol) in ether (10.0 mL) at 0 °C and then heated to reflux
overnight. The mixture was poured into water and filtered
through Celite. The aqueous layer was extracted with ether,
and the organic extracts were washed brine and dried over
magnesium sulfate. The solvent was removed by rotary
evaporation, and the residue was purified by column chroma-
tography (silica gel, hexane) to provide 3.46 g (81%) of the title
product as a yellow liquid. FTIR (neat) 2955, 1443, 1250, 1071,
3′,3′′-Dim e t h yl-5-(t r im e t h ylsilyl)-2,2′:5′,2′′-t e r t h io-
p h en e (39a ).21 Method A: A flame-dried flask was charged
with 2-(5′-(trimethylsilyl)thienyl)-3-methyl-5-(trimethylstan-
nyl)thiophene (2.13 g, 5.13 mmol), 2-iodo-3-methylthiophene
(36a ) (1.72 g, 7.68 mmol), bis(triphenylphosphine)palladium(II)
chloride (0.072 g, 0.103 mmol), and DMF (10.0 mL), and the
mixture was stirred at room temperature for 40 h and then
poured into water. The aqueous layer was extracted with
ether, and the organic extracts were washed with brine and
dried over magnesium sulfate. The solvent was removed by
rotary evaporation, and the residue was purified by column
chromatography (silica gel, hexane) to provide 0.631 g (35%)
of the title product as a thick light-green liquid.
Method B: To a solution of diisopropylamine (1.11 g, 1.54
mL, 11.0 mmol) in THF (10.0 mL) was added dropwise
n-butyllithium (9.09 mL, 11.0 mmol, 1.21 M in hexanes) at
-78 °C. The mixture was warmed to 0 °C for 10 min and then
recooled to -78 °C. To this solution was added dropwise 2-(5′-
(trimethylsilyl)thienyl)-3-methylthiophene (37a ) (2.78 g, 11.0
mmol) in THF (10.0 mL), and the mixture was stirred at this
temperature for 2 h. Iodine (2.79 g, 11.0 mmol) in THF (20.0
mL) was added dropwise, and the mixture was stirred at this
temperature for 30 min and poured into water. The aqueous
layer was extracted with ether, and the organic extracts were
washed with brine and dried over sodium sulfate. The solvent
was removed by rotary evaporation, and the residue, crude
38a , was used directly for next reaction. To a solution of 38a ,
990, 840, 756, 707 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.17
(ABq, J ) 3.4 Hz, ∆ν ) 5.4 Hz, 2 H), 7.11 (d, J ) 5.1 Hz, 1 H),
6.86 (d, J ) 5.1 Hz, 1 H), 2.39 (s, 3 H), 0.33 (s, 9 H).
2-(5′-(Tr im eth ylsilyl)th ien yl)-3-bu tylth ioph en e (37b).1gg
To magnesium turnings (0.547 g, 22.5 mmol) in ether (15.0
mL) was added dropwise 3-butyl-2-iodothiophene (36b) (4.03
g, 15 mmol) at room temperature while an ice bath was used
occasionally to maintain a mild reflux. The mixture was
stirred at room temperature for 2 h and transferred via
cannula to a solution of 2-bromo-5-(trimethylsilyl)thiophene
(18) (2.35 g, 10.0 mmol) and [1,3-bis(diphenylphosphino)-
propane]nickel(II) chloride (0.271 g, 0.5 mmol) at 0 °C. The

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6917
[1,3-bis(diphenylphosphino)propane]nickel(II) chloride (0.271
g, 0.5 mmol) in ether (10.0 mL) was added dropwise by syringe
at 0 °C one-half of a solution of 2-(3-methylthienyl)magnesium
iodide, made from 2-iodo-3-methylthiophene (36a ) (3.36 g, 15.0
mmol) and magnesium (0.547 g, 22.5 mmol) in ether (10.0 mL).
The mixture was stirred at room temperature overnight and
then poured into water. The aqueous layer was extracted with
ether, and the organic extracts were washed with brine and
dried over magnesium sulfate. The solvent was removed by
rotary evaporation, and the residue was purified by column
chromatography on silica gel (hexane) to provide 1.35 g (75%)
of the title product as a thick light-green liquid along with
1.48 g of recovered starting material. FTIR (neat) 2954, 1448,
n-butyllithium (1.71 mL, 2.8 mmol, 1.64 M in hexanes) at -78
°C. The solution was warmed to 0 °C for 5 min and recooled
to -78 °C. 3′,3′′-Dibutyl-5-(trimethylsilyl)-2,2′:5′,2′′-terthiophene
(39b) in THF (2.0 mL) was added dropwise to the above
solution via cannula, and the mixture was stirred at -78 °C
for 1 h before the addition of tributyltin chloride (0.911 g, 2.8
mmol). The mixture was allowed to warm to room tempera-
ture for 20 min and poured into water. The aqueous layer
was extracted with ether, and the organic extracts were
washed with brine and dried over sodium sulfate. The solvent
was removed under reduced pressure to afford 1.90 g (94%) of
the title product as a thick light-yellow liquid which was used
without further purification. FTIR (neat) 2956, 1464, 1250,
1250, 1075, 991, 840, 756, 707 cm-1
.
1H NMR (300 MHz,
991, 840 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.16 (s, 2 H),
CDCl3) δ 7.18 (ABq, J ) 3.46 Hz, ∆ν ) 7.30 Hz, 2 H), 7.11 (d,
J ) 5.13 Hz, 1 H), 6.91 (s, 1 H), 6.86 (d, J ) 5.13 Hz, 1 H),
2.40 (s, 3 H), 2.39 (s, 3 H), 0.33 (s, 9 H).
6.93 (s, 2 H), 2.77-2.72 (m, 4 H), 1.63-1.51 (m, 10 H), 1.41-
1.22 (m, 10 H), 1.19-1.06 (m, 6 H), 0.95-0.87 (m, 15 H), 0.32
(s, 9 H).
3′,3′′-D ib u t y l-5-(t r im e t h y ls ily l)-2,2′:5′,2′′-t e r t h io -
p h en e (39b).1gg To a solution of diisopropylamine (0.65 g, 0.90
mL, 6.42 mmol) in THF (6.0 mL) was added dropwise n-
butyllithium (3.9 mL, 6.42 mmol, 2.5 M in hexanes) at -78
°C. The mixture was warmed to 0 °C for 10 min and recooled
to -78 °C. To this solution was added dropwise 2-(5′-
(trimethylsilyl)thienyl)-3-butylthiophene (37b) (1.89 g, 6.42
mmol) in THF (6.0 mL), and the mixture was stirred at -78
°C for 2 h before slowly adding iodine (1.63 g, 6.42 mmol) in
THF (10.0 mL). The mixture was allowed to warm to room
temperature and stirred for 30 min before being poured into
water. The aqueous layer was extracted with ether, and the
organic extracts were washed with brine and dried over
magnesium sulfate. The solvent was removed by rotary
evaporation, and the residue 38b was used directly for the next
reaction. 3-Butyl-2-thienylmagnesium iodide [made from
3-butyl-2-iodothiophene (36b) (2.56 g, 9.63 mmol) and mag-
nesium (0.35 g, 14.4 mmol) in ether (10.0 mL)] was transferred
into the solution of 38b and (1,3-bis(diphenylphosphino)-
propane)nickel(II) chloride (4 mg, 0.007 mmol) in ether (5.0
mL) at 0 °C. The mixture was allowed to warm to room
temperature and was stirred overnight. The mixture was
poured into water and filtered through Celite, and the aqueous
layer was extracted with ether. The organic extracts were
washed with brine and dried over magnesium sulfate, and the
solvent was removed by rotary evaporation. The residue was
purified by column chromatography on silica gel (hexane) to
provide 1.22 g (44%) of the title product as a light-green thick
liquid in ca. 90% purity. FTIR (neat) 2956, 1458, 1250, 991,
2-(Tr im eth ylsta n n yl)-4,4′-d im eth yl-5′′-(tr im eth ylsilyl)-
5,2′:5′,2′′-ter th iop h en e. To a solution of diisopropylamine
(0.653 g, 0.90 mL, 6.65 mmol) in THF (10.0 mL) was added
dropwise n-butyllithium (5.5 mL, 6.65 mmol, 1.21 M in
hexanes) at -78 °C. The mixture was warmed to 0 °C for 10
min and then recooled to -78 °C. 3′,3′′-Dimethyl-5-(trimeth-
ylsilyl)-2,2′:5′,2′′-terthiophene (39a ) (2.25 g, 6.65 mmol) in THF
(6.0 mL) was added dropwise via cannula. The mixture was
stirred at this temperature for 2 h, and trimethyltin chloride
(1.33 g, 6.65 mmol) in THF (6.0 mL) was added via cannula.
The mixture was warmed to room temperature for 0.5 h and
poured into water. The aqueous layer was extracted with
ether, and the organic extracts were washed with brine and
dried over sodium sulfate. The solvent was removed under
reduced pressure to provide 3.09 g (96%) of the title product
as a thick dark-yellow oil. FTIR (neat) 2955, 1429, 1250, 1074,
991, 840, 757 cm-1
.
1H NMR (300 Hz, CDCl3) δ 7.17 (ABq, J
) 3.6 Hz, ∆ν ) 6.9 Hz, 2 H), 6.93 (s, 1 H), 6.90 (s, 1 H), 2.40
(s, 3 H), 2.39 (s, 3 H), 0.36 (s, 9 H), 0.32 (s, 9 H).
Sp ir oh ep ta m er Com p ou n d 41.1gg A flame-dried flask
was charged with 13 (0.054 g, 0.1 mmol), 3,4′-dimethyl-5-
(tributylstannyl)-5′′-(trimethylsilyl)-2,2′:5′,2′′-terthiophene (40a)-
(0.57 g, 0.90 mmol), tetrakis(triphenylphosphine)palladium(0)
(0.0093g, 0.008 mmol), and toluene (1.00 mL). The mixture
was heated at 40 °C for 2 h, then 60 °C for 2 h, and then at
100 °C (bath temp) overnight. The solvent was removed by
rotary evaporation and the residue was washed with ethanol
and then hexane to provide 140 mg (86%) of the title product
as dark red crystals. Mp: 260 °C dec UV (CHCl3) λmax 456
nm, ꢀmax 2.94 × 104, tailing edge 545 nm. FTIR (KBr) 2950,
840, 756 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.17 (s, 2 H),
1132, 991, 839 cm-1
.
1H NMR (500 MHz, CDCl3) δ 7.19 (1/2
7.13 (d, J ) 5.2 Hz, 1 H), 6.93 (s, 1 H), 6.90 (d, J ) 5.2 Hz, 1
H), 2.74 (two overlapping t, J ) 7.5 Hz, 4 H), 1.62 (two
overlapping p, J ) 8.5 Hz, 4 H), 1.39 (two overlapping sext,
appearing as br sept, J ) 7.5 Hz, 6 H), 0.93 (t, J ) 7.35 Hz, 3
H), 0.92 (t, J ) 7.29 Hz, 3 H), 0.33 (s, 9 H).
ABq, J ) 2.5 Hz, 4 H), 7.15 (1/2 ABq, J ) 2.5 Hz, 4 H), 6.99 (s,
4 H), 6.93 (s, 4 H), 2.40 (s, 12 H), 2.37 (s, 12 H), 2.33 (s, 8 H),
0.31 (s, 36 H). 13C NMR (125 MHz, CDCl3) δ 141.94, 141.22,
140.61, 134.82, 134.80, 134.60, 134.58, 134.25, 131.34, 130.78,
129.60, 128.64, 128.44, 126.77, 17.08, 16.12, 16.00, 0.31. FAB/
MS (NBA) calcd relative isotopic intensities for C80H84S14Si5
(M+): 1632 (64%), 1633 (80%), 1634 (100%), 1635 (83%), 1636
(83%), 1637 (40%), 1638 (23%). Found: 1632 (77%), 1633
(96%), 1634 (100%), 1635 (94%), 1636 (79%), 1637 (56%), 1638
(45%).
3,4′-Dim et h yl-5-(t r ib u t ylst a n n yl)-5′′-(t r im et h ylsilyl)-
2,2′:5′,2′′-ter th iop h en e (40a ).21 To a solution of diisopropyl-
amine (0.65 g, 0.90 mL, 6.43 mmol) in THF (10.0 mL) was
added dropwise at -78 °C n-butyllithium (3.92 mL, 6.43 mmol,
1.64 M in hexanes). The mixture was warmed to 0 °C for 10
min and then recooled to -78 °C. 3′,3′′-Dimethyl-5-(trimeth-
ylsilyl)-2,2′:5′,2′′-terthiophene (39a ) (2.24 g, 6.43 mmol) in THF
(6.0 mL) was added dropwise via cannula. The mixture was
stirred at -78 °C for 2 h, and tributyltin chloride (2.09 g, 1.74
mL, 6.65 mmol) was added dropwise. The mixture was
warmed to room temperature for 0.5 h and poured into water.
The aqueous layer was extracted with ether, and the organic
extracts were washed with brine and dried over sodium
sulfate. The solvent was removed by reduced pressure to
provide 3.98 g (97%) of the title product as a thick dark-yellow
oil which is >95% pure by spectroscopic analysis. FTIR (neat)
2-(5′-(Tr im et h ylsilyl)t h ien yl)-3-b u t yl-5-(t r ib u t ylst a n -
n yl)th iop h en e (42). To a solution of diisopropylamine (0.697
g, 0.965 mL, 6.89 mmol) in THF (5.0 mL) was added n-
butyllithium (4.10 mL, 5.74 mmol, 1.4 M in hexanes) dropwise
at -78 °C. The mixture was warmed to 0 °C for 5 min and
recooled to -78 °C. 37b (1.69 g, 5.74 mmol) in THF (5.0 mL)
was added dropwise via cannula, and the mixture was stirred
at -78 °C for 1 h. Tributyltin chloride (1.87 g, 1.56 mL, 5.74
mmol) was added, and the mixture was allowed to warm to
room temperature for 30 min and then poured into water. The
aqueous solution was extracted with ether, and the combined
organic extracts were washed with brine and dried over
magnesium sulfate. The solvent was removed under reduced
pressure to provide 3.18 g (95%) of the title product as a thick
light-yellow liquid which was virtually pure and was used
without further purification. FTIR (neat) 2956, 1464, 1414,
2956, 1459, 1250, 1073, 992, 840, 756 cm-1
.
1H NMR (300 Hz,
CDCl3) δ 7.17 (ABq, J ) 3.0 Hz, ∆ν ) 6.0 Hz, 2 H), 6.91 (s, 1
H), 6.89 (s, 1 H), 2.41 (s, 3 H), 2.39 (s, 3 H), 1.55 (m, 6 H), 1.34
(sext, J ) 7.28 Hz, 6 H), 1.09 (m, 6 H), 0.89 (t, J ) 7.28 Hz, 9
H), 0.32 (s, 9 H).
2-(Tr ibu tylsta n n yl)-4,4′-d ibu tyl-5′′-(tr im eth ylsilyl)-5,2′:
5′,2′′-t er t h iop h en e (40b ).1gg To a solution of diisopropyl-
amine (1.22 g, 2.8 mmol) in THF (3.0 mL) was added dropwise
1377, 1250, 1206, 1072, 991, 840, 800, 756 cm-1
.
1H NMR
(CDCl3, 300 MHz) δ 7.14 (ABq, J ) 3.45 Hz, ∆ν ) 4.96 Hz, 2

6918 J . Org. Chem., Vol. 61, No. 20, 1996
Wu et al.
H), 6.93 (s, 1 H), 2.77 (t, J ) 7.84 Hz, 2 H), 1.70-1.50 (m, 2
H), 1.32 (sext, J ) 7.28 Hz, 2 H), 1.09 (t, J ) 8.08 Hz, 2 H),
0.89 (t, J ) 7.27 Hz, 3 H), 0.31 (s, 9 H).
C6D6) δ 141.75, 140.65, 140.56, 140.53, 140.41, 137.19, 136.27,
135.46, 135.34, 135.27, 134.98, 128.33, 128.01, 127.68, 127.52,
127.42, 126.94, 128.84, 126.79, 126.66, 126.14, 126.09, 125.50,
124.34, 32.95, 32.92, 32.84, 29.71, 29.58, 29.42, 23.09, 23.05,
23.01, 14.24, 14.18 (2 C), -0.04.
3-Eth yl-2-iod o-5,2′-bith iop h en e (43). To 38b (4.97 g,
11.85 mmol) was added acetonitrile (35 mL), water (1 mL),
and p-tolunenesulfonic acid (0.370 g, 2.37 mmol). The solution
was heated to reflux for 4 h and poured into water, and the
aqueous phase was extracted with ether. The combined
organic phase was washed with brine and dried over magne-
sium sulfate. The solvent was removed by rotary evaporation,
and gravity column chromatography (silica gel, hexane) af-
forded 2.63 g (64%) of the title compound which was ca. 85%
3-Eth ylth iop h en e (48).1ff
To magnesium turnings (10.96
g, 450 mmol) in ether (150 mL) was added dropwise 1-bromo-
ethane (59.42 g, 40 mL, 545 mmol) at room temperature, and
an ice bath was used occassionaly to maintain a mild reflux.
The mixture was stirred at room temperature for 1 h and
transferred via cannula to a solution of 3-bromothiophene
(49.60 g, 304 mmol) and (1,3-bis(diphenylphosphino)propane)-
nickel(II) chloride (0.18 g, 0.34 mmol) in ether (150 mL) at
-78 °C. The mixture was then slowly allowed to warm to room
temperature. This solution was then stirred overnight before
being poured into water with a few drops of 3 N hydrochloric
acid. The aqueous layer was extracted with ether, and the
organic extracts were washed with brine and dried over
magnesium sulfate. The solvent was removed, and the residue
was purified by flash chromatography (silica gel, hexane) to
afford 30.39 g (89%) of the title compound as a light brown
liquid. FTIR (neat) 2965, 2931, 1461, 1410, 1317, 857, 769
1
pure as judged by H NMR analysis. However, the material
was used for the next step at that level of purity. 1H NMR
(CDCl3, 300 MHz) δ 7.29 (dd, J ) 2.77 Hz, 1 H), 7.0 (m, 3 H),
2.68 (t, J ) 7.70 Hz, 2 H), 1.55 (pent, J ) 7.44 Hz, 2 H), 1.37
(sext, J ) 7.30 Hz, 2 H), 0.89 (t, J ) 7.29 Hz, 3 H).
3′,4′′-Di-n -b u t yl-5-(t r im et h ylsilyl)-2,2′:5′,2′′:5′′:2′′′-q u a -
ter th iop h en e (44). A round bottom flask was charged with
42 (3.18 g, 5.45 mmol), 43 (2.11 g, 6.06 mmol), copper(I) iodide
(0.023 g, 0.123 mmol), and tetrakis(triphenylphosphine)-
palladium(0) (0.094 g, 0.082 mmol). The mixture was then
degassed in vacuo followed by introducing nitrogen and DMF
(5.0 mL). The mixture was stirred at room temperature
overnight and then heated to 75-80 °C (oil temp) overnight.
The solution was poured into saturated ammonium chloride.
The aqueous solution was extracted with ether, and the
combined organic extracts were washed with brine and dried
over magnesium sulfate. The solvent was removed by rotary
evaporation, and the residue was purified by gravity chroma-
tography (silica gel, hexane) to provide 1.74 g (62%) of the title
product as a light-yellow liquid. FTIR (neat) 3068, 2955, 2858,
cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.23 (m, 1 H), 6.93 (m, 2
H), 2.65 (q, J ) 7.55 Hz, 2 H), 1.24 (t, J ) 7.56 Hz, 3 H). 13C
NMR (100 MHz, CDCl3) δ 144.68, 128.02, 125.18, 119.21,
23.45, 14.74.
3-Eth yl-2-iod oth iop h en e (49).1ff To a solution of 3-eth-
ylthiophene (48) (20.19 g, 180 mmol) in benzene (100 mL) at
0 °C was added mercuric oxide (38.98 g, 180 mmol). Iodine
(50.27 g, 198 mmol) in benzene (300 mL) and dichloromethane
(50 mL) was added dropwise to the solution at 0 °C. The
mixture was stirred at room temperature overnight before
filtration through Celite. The filtered solution was poured into
water, the aqueous layer was extracted with ether, and the
organic extracts were washed with brine and dried over
magnesium sulfate. The solvent was removed by rotary
evaporation. The residue was purified by flash chromatogra-
phy (silica gel, hexane) to afford 36.01 g (84%) of the title
product as a faint yellow liquid. FTIR (neat) 3102, 2966, 2930,
1507, 1458, 1378, 1250, 1207, 1076, 991, 840, 756, 692 cm-1
.
1H NMR (CDCl3, 300 MHz) δ 7.28 (d, J ) 5.10 Hz, 1 H), 7.16
(s, 2 H), 7.11 (d, J ) 3.41 Hz, 1 H), 7.05 (dd, J ) 5.14, 3.57 Hz,
1 H), 6.98 (d, J ) 1.05 Hz, 2 H), 2.73 (overlapping t, J ) 7.70
Hz, 4 H), 1.65 (m, 4 H), 1.40 (m, 4 H), 0.96-0.87 (overlapping
t, J ) 7.30 Hz, 6 H), 0.33 (s, 9 H).
3′,4′′,4′′′′-Tr i-n -b u t yl-2-(t r im et h ylsilyl)-2,2′:5′,2′′:5′′,2′′′:
5′′′,2′′′′:5′′′′,2′′′′′-sexith iop h en e (46). To a solution of diiso-
propylamine (0.410 g, 0.60 mL, 4.06 mmol) in THF (5.0 mL)
was added dropwise n-butyllithium (1.35 mL, 3.38 mmol, 2.5
M in hexanes) at -78 °C. The mixture was warmed to 0 °C
for 5 min and recooled to -78 °C. Tetramer 44 (1.74 g, 3.38
mmol) in THF (10.0 mL) was added dropwise via cannula. The
mixture was warmed to 0 °C for 5 min and recooled to -78
°C, and tributyltin chloride (1.10 g, 0.92 mL, 3.38 mmol) was
added in one portion. The mixture was allowed to warm to
room temperature for 10 min and poured into water. The
aqueous solution was extracted with ether, and the combined
organic extracts were washed with brine and dried over
magnesium sulfate. The solvent was removed under reduced
pressure, and the crude product 45 was used directly for the
next reaction. The crude 45 (assumed to be 3.38 mmol), 43
(1.30 g, ca. 3.72 mmol), tetrakis(triphenylphosphine)pal-
ladium(0) (0.059 g, 0.051 mmol), and copper(I) iodide (0.015
g, 0.077 mmol) were mixed in DMF (3.0 mL, sparged with N2)
under N2 at room temperature. The mixture was stirred at
room temperature overnight and then heated to 75-80 °C (oil
temp) overnight and poured into water. The mixture was
filtered through Celite, and the aqueous solution was extracted
with ether. The combined organic extracts were washed with
brine and dried over magnesium sulfate. The solvent was
removed by rotary evaporation, and the residue was purified
by gravity chromatography (silica gel, hexane) to provide 1.09
g (44% from 44) of the title product as a thick light-red liquid.
FTIR (neat) 3066, 2955, 2858, 1503, 1456, 1378, 1250, 1214,
2873, 1459, 1399, 963, 893, 826, 717, 632 cm-1
.
1H NMR (300
MHz, CDCl3) δ 7.37 (d, J ) 5.44 Hz, 1 H), 6.76 (d, J ) 5.47
Hz, 1 H), 2.56 (q, J ) 7.58 Hz, 2 H), 1.17 (t, J ) 7.58 Hz, 3 H).
13C NMR (100 MHz, CDCl3) δ 148.38, 130.54, 127.57, 73.63,
25.69, 14.61. HRMS calcd for C6H7IS 237.9313, found 237.9306.
3-Eth yl-2-((tr im eth ylsilyl)eth yn yl)th iop h en e (50).1ff To
a solution of 49 (14.79 g, 63 mmol) in THF (50 mL) were added
diisopropylamine (9.56 g, 13.2 mL, 94.5 mmol), (trimethylsilyl)-
acetylene (6.81 g, 9.8 mL, 69.3 mmol), bis(triphenylphosphine)-
palladium(II) chloride (2.23 g, 3.15 mmol), and copper(I) iodide
(0.30 g, 1.57 mmol) (the two catalysts were degassed in vacuo
for 30 min immediately before use). The reaction was stirred
overnight before being poured into water. The aqueous layer
was extracted with dichloromethane, and the organic extracts
were washed with brine. The dichloromethane layers were
dried over magnesium sulfate. The solvent was removed by
rotary evaportation, and the residue was purified by gravity
chromatography (silica gel, hexane) to provide 12.71 g (97%)
of the title product as an orange-brown liquid. UV (dichlo-
romethane) λmax 278 nm. FTIR (neat) 2965, 2144, 1526, 1461,
1420, 1321, 1250, 1184, 1084, 1056, 903, 843, 759, 724, 670,
650 cm-1 1H NMR (300 MHz, CDCl3) δ 7.11 (d, J ) 5.15 Hz,
.
1 H), 6.83 (d, J ) 5.15 Hz,1 H), 2.70 (q, J ) 7.60 Hz, 2 H),
1.21 (t, J ) 7.60 Hz, 3 H), 0.23 (s, 9 H). 13C NMR (125 MHz,
CDCl3) δ 150.31, 127.94, 126.44, 118.33, 101.16, 97.87, 23.25,
14.87, 0.44. HRMS calcd for C11H16SSi 208.0742, found
208.0743.
3-E t h yl-5-iod o-2-((t r im et h ylsilyl)et h yn yl)t h iop h en e
(51).1ff To a solution of diisopropylamine (12.14 g, 17 mL, 120
mmol) in ether (100 mL) at -78 °C was added dropwise
n-butyllithium (74 mL, 110 mmol, 1.49 M in hexanes). The
mixture was warmed to 0 °C for 30 min and then recooled to
-78 °C. 50 (11.49 g, 55 mmol) in ether (50 mL) at room
temperature was then added dropwise, and the solution was
warmed from -78 °C to 0 °C for 10 min. Next, the solution
was recooled to -78 °C. While at -78 °C, iodine (30.52 g, 120
mmol) in ether (150 mL) was added via cannula, and the
1077, 990, 838, 794, 756, 692 cm-1
.
1H NMR (300 MHz, C6D6)
δ 7.27 (d, J ) 3.45 Hz, 1 H), 7.07 (d, J ) 3.45 Hz, 1 H), 7.06
(s, 1 H), 7.05 (dd, J ) 3.58, 1.16 Hz, 1 H), 7.03 (s, 1 H), 6.98 (s,
1 H), 6.96 (ABq, J ) 3.79 Hz, ∆ν ) 6.56 Hz, 2 H), 6.83 (dd, J
) 5.18, 1.18 Hz, 1 H), 6.72 (dd, J ) 5.18, 3.56 Hz, 1 H), 2.72
(t, J ) 7.81 Hz, 2 H), 2.67 (t, J ) 7.81 Hz, 2 H), 2.62 (t, J )
7.81 Hz, 2 H), 1.60-1.40 (m, 6 H), 1.29 (overlap pent, J ) 7.40
Hz, 6 H), 0.85 (t, J ) 7.46 Hz, 3 H), 0.84 (t, J ) 7.28 Hz, 3 H),
0.82 (t, J ) 7.47 Hz, 3 H), 0.25 (s, 9 H). 13C NMR (75 MHz,

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6919
solution was allowed to warm up to room temperature
overnight. The mixture was quenched with water, and the
aqueous layer was extracted with ether. The organic extracts
were washed with brine and aqueous sodium thiosulfate. The
ether layers were dried over magnesium sulfate. The solvent
was removed by rotary evaportation, and the residue was
purified by flash chromatography (silica gel, hexane) to provide
17.20 g (93%) of the title product as a yellow liquid that
darkened upon standing. FTIR (neat) 2965, 2141, 1526, 1460,
P r otod esilyla ted Dim er 55.1ff To a solution of 53 (7.41
g, 21.6 mmol) in methanol (20 mL) was added potassium
carbonate (9.17 g, 66.3 mmol). The solution was allowed to
stir for 5 h before being poured into water. The aqueous layer
was extracted with dichloromethane, and the organic extracts
were washed with brine. The combined organic layers were
dried over magnesium sulfate. The solvent was removed by
rotary evaporation. No further purification was necessary to
afford 5.84 g (100%) of the title compound as a brown liquid.
FTIR (neat) 3298, 3103, 2968, 2933, 2874, 2193, 2097, 1459,
1411, 1250, 1191, 1056, 950, 843, 759, 685 cm-1 1H NMR (300
.
MHz, CDCl3) δ 6.98 (s, 1 H), 2.65 (q, J ) 7.56 Hz, 2 H), 1.17
(t, J ) 7.60 Hz, 3 H), 0.22 (s, 9 H). 13C NMR (100 MHz, CDCl3)
δ 151.40, 137.48, 124.07, 102.82, 95.92, 73.96, 22.59, 14.37,
-0.06. HRMS calcd for C11H15ISSi 333.9708, found 333.9697.
3-Eth yl-2-eth yn ylth iop h en e (52).1ff To a solution of 50
(12.50 g, 60 mmol) in methanol (60 mL) was added potassium
carbonate (24.89 g, 180 mmol). The solution was allowed to
stir for 4.5 h before being poured into water. The aqueous
layer was extracted with dichloromethane, and the organic
extracts were washed with brine. The combined organic layers
were dried over magnesium sulfate. The solvent was removed
by rotary evaporation. No further purification was necessary
to afford 8.17 g (99%) of the title compound as a light brown
liquid. FTIR (neat) 3299, 3105, 2968, 2934, 2100, 1528, 1460,
1061, 902, 836 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.20 (d, J
) 5.17 Hz, 1 H), 7.01 (s, 1 H), 6.90 (d, J ) 5.17 Hz, 1 H), 3.48
(s, 1 H), 2.75 (q, J ) 7.60 Hz, 2 H), 2.69 (q, J ) 7.59 Hz, 2 H),
1.25 (t, J ) 7.62 Hz, 3 H), 1.22 (t, J ) 7.64 Hz, 3 H). 13C NMR
(100 MHz, CDCl3) δ 150.24, 149.86, 131.97, 127.86, 126.97,
123.51, 118.24, 117.20, 88.09, 86.53, 84.31, 76.14, 22.99, 22.79,
14.67, 14.48.
Tetr a m er 56.1ff To a solution of 54 (0.90 g, 1.92 mmol) in
THF (5 mL) was added 55 (0.69 g, 2.55 mmol), diisopropyl-
amine (0.30 g, 0.42 mL, 3.0 mmol), bis(triphenylphosphine)-
palladium(II) chloride (0.05 g, 0.07 mmol), and copper iodide
(0.01 g, 0.04 mmol) (the two catalysts were degassed in vacuo
for 30 min immediately before use). The reaction was allowed
to stir for 1 d. The reaction was quenched with water, and
the aqueous layer was extracted with dichloromethane. The
organic extracts were washed with brine. The organic layers
were dried over magnesium sulfate. The solvent was removed
by rotary evaportaion, and the residue was purified by gravity
chromatography (silica gel, hexane) to provide 1.02 g (87%) of
the title product as a fluorescent yellow liquid which darkened
upon exposure to the air. UV (dichloromethane) λmax 404 nm.
FTIR (neat) 2967, 2873, 2185, 2140, 1459, 1250, 1190, 1062,
1418, 1157, 1056, 903, 837, 728, 659 cm-1
.
1H NMR (300 MHz,
CDCl3) δ 7.14 (d, J ) 5.16 Hz, 1 H), 6.86 (d, J ) 5.17 Hz, 1 H),
3.42 (s, 1 H), 2.72 (q, J ) 7.60 Hz, 2 H), 1.21 (t, J ) 7.61 Hz,
3 H). 13C NMR (100 MHz, CDCl3) δ 150.33, 127.59, 126.32,
116.65, 83.26, 76.64, 22.74, 14.60. LRMS calcd for C8H8S 136,
found 136.
Dim er 53.1ff To a solution of 51 (3.35 g, 10 mmol) in THF
(15 mL) were added diisopropylamine (1.51 g, 2.1 mL, 15
mmol), 52 (1.28 g, 9.54 mmol), bis(triphenylphosphine)palla-
dium(II) chloride (0.35 g, 0.50 mmol), and copper iodide (0.05
g, 0.28 mmol) (the two catalysts were degassed in vacuo for
30 min immediately before use). The reaction was allowed to
stir for 2 d before being poured into water. The aqueous layer
was extracted with dichloromethane, and the organic extracts
were washed with brine. The dichloromethane layers were
dried over magnesium sulfate. The solvent was removed by
rotary evaporation, and the residue was purified by gravity
chromatography (silica gel, hexane) to provide 2.95 g (90%) of
the title compound as a medium yellow liquid. UV (dichlo-
romethane) λmax 348 nm. FTIR (neat) 3103, 2967, 2193, 2141,
1519, 1461, 1412, 1322, 1249, 1195, 1061, 903, 857, 760, 735,
902, 845, 760 cm-1 1H NMR (300 MHz, CDCl3) δ 7.21 (d, J )
.
5.17 Hz, 1 H), 7.05 (s, 1 H), 7.04 (s, 1 H), 7.01 (s, 1 H), 6.90 (d,
J ) 5.16 Hz, 1 H), 2.69 (10 line m, 8 H), 1.24 (t, J ) 7.64 Hz,
6 H), 1.21 (t , J ) 7.71 Hz, 6 H), 0.25 (s, 9 H). 13C NMR (75
MHz, CDCl3) δ 149.92, 149.85, 149.63, 149.61, 132.56, 132.40,
132.25, 127.89, 127.02, 124.00, 123.44, 122.58, 120.06, 119.39,
118.91, 117.28, 102.68, 96.66, 89.72, 89.44, 88.29, 87.19, 86.71,
86.03, 23.04, 22.88, 22.74, 14.73, 14.58, 14.34, 14.21, -0.04.
HRMS calcd for C35H34S4Si 610.1313, found 610.1303.
P r otod esilyla ted Tetr a m er 57.1ff To a solution of 56 (4.47
g, 7.3 mmol) in methanol (5 mL) and dichloromethane (5 mL)
was added potassium carbonate (3.05 g, 21.9 mmol). The
solution was allowed to stir for 6 h before being poured into
water. The aqueous layer was extracted with dichloromethane,
and the organic extracts were washed with brine. The
combined organic layers were dried over magnesium sulfate.
The solvent was removed by rotary evaporation. No further
purification was necessary to afford 3.92 g (100%) of the title
compound as a yellow-brown liquid which had to be used
immediately due to its instability in air. FTIR (neat) 3298,
633 cm-1 1H NMR (300 MHz, CDCl3) δ 7.19 (d, J ) 5.16 Hz,
.
1 H), 6.98 (s, 1 H), 6.89 (d, J ) 5.17 Hz, 1 H), 2.74 (q, J ) 7.60
Hz, 2 H), 2.65 (q, J ) 7.59 Hz, 2 H), 1.23 (t, J ) 7.62 Hz, 3 H),
1.21 (t, J ) 7.67 Hz, 3 H), 0.24 (s, 9 H). 13C NMR (75 MHz,
CDCl3) δ 149.86, 149.78, 132.03, 127.87, 126.92, 123.07, 119.55,
117.30, 102.33, 96.75, 88.32, 86.49, 23.01, 22.88, 14.72, 14.35,
-0.03. HRMS calcd for C19H22S2Si 342.0932, found 342.0929.
Iod in a ted Dim er 54.1ff To a solution of diisopropylamine
(0.16 g, 0.22 mL, 1.6 mmol) in THF (2.5 mL) at -78 °C was
added dropwise n-butyllithium (0.94 mL, 1.5 mmol, 1.6 M in
hexanes). The solution was warmed to 0 °C for 10 min and
then recooled to -78 °C. 53 (0.34 g, 1.0 mmol) in THF (5 mL)
was then added dropwise, and the solution was stirred at -78
°C for 10 min. While still at -78 °C, iodine (0.41 g, 1.6 mmol)
in THF (2.5 mL) was added via cannula and the solution was
allowed to stir at -78 °C for 2 h. The mixture was quenched
with water at -78 °C, and the aqueous layer was extracted
with ether. The organic extracts were washed with brine and
aqueous sodium thiosulfate. The ether layers were dried over
magnesium sulfate. The solvent was removed by rotary
evaporation, and the residue was purified by gravity column
chromatography (silica gel, hexane) to provide 0.39 g (84%) of
the title product as a yellow liquid which darkened upon
exposure to air. FTIR (neat) 2966, 2141, 1518, 1460, 1408,
2967, 2932, 2182, 2097, 1459, 1189, 1061, 902, 843 cm-1
.
1H
NMR (300 MHz, CDCl3) δ 7.20 (d, J ) 5.17 Hz, 1 H), 7.05 (s,
1 H), 7.03 (s, 1 H), 7.02 (s, 1 H), 6.89 (d, J ) 5.16 Hz, 1 H),
3.48 (s, 1 H), 2.71 (9 line m, 8H), 1.24 (t, J ) 7.61 Hz, 3 H),
1.24 (t, J ) 7.57 Hz, 6 H), 1.21 (t, J ) 7.62 Hz, 3 H). 13C NMR
(100 MHz, CDCl3) δ 150.30, 149.85, 149.68, 149.63, 132.53,
132.33, 127.86, 126.97, 123.96, 123.49, 123.00, 119.21, 118.83,
118.69, 117.22, 89.38, 89.32, 88.22, 87.12, 86.68, 86.00, 84.51,
76.02, 22.97, 22.75, 14.65, 14.49, 14.48, 14.44.
1-Br om o-4-(tr im eth ylsilyl)ben zen e.29 To a solution of
1,4-dibromobenzene (12.7 g, 50.0 mmol) in ether (100 mL) was
added at -78 °C n-butyllithium (20.04 mL, 50.1 mmol, 2.5 M
in hexanes) over 20 min. The solution was stirred for 1 h at
-78 °C, and chlorotrimethylsilane (6.98 mL, 55.0 mmol) was
added over 10 min. The solution was warmed to room
temperature for 30 min and poured into water. The aqueous
layer was extracted with ether (3 × 10 mL), and the combined
organic layers were washed with brine and dried over mag-
nesium sulfate. No further purification was needed to afford
9.8 g (86%) of the the title compound as a clear colorless oil.
FTIR (neat) 2956, 1574, 1479, 1376, 1251, 1106, 1067, 1012,
1383, 1321, 1249, 1196, 1058, 987, 950, 843, 759, 696 cm-1
.
1H NMR (300 MHz, CDCl3) δ 7.03 (s, 1 H), 6.98 (s, 1 H), 2.69
(q, J ) 7.59 Hz, 2 H), 2.65 (q, J ) 7.59 Hz, 2 H), 1.20 (t, J )
7.60 Hz, 6 H), 0.24 (s, 9 H). 13C NMR (100 MHz, CDCl3) δ
151.17, 149.83, 137.76, 132.30, 123.42, 122.52, 119.99, 102.61,
96.63, 90.01, 85.05, 74.88, 22.84, 22.74, 14.60, 14.30, -0.05.
HRMS calcd for C19H21IS2Si 467.9899, found 467.9895.
(29) Stephens, E. B.; Kinsey, K. E.; Davis, J . F.; Tour, J . M.
Macromolecules 1993, 26, 3519.

6920 J . Org. Chem., Vol. 61, No. 20, 1996
841 cm-1
Wu et al.
.
1H NMR (300 MHz, CDCl3) δ 7.47 (d, J ) 8.3 Hz,
solid. UV (CHCl3) λmax 418 nm, tailing edge 495 nm. FTIR
-1
2 H), 7.36 (d, J ) 8.3 Hz, 2 H), 0.24 (s, 9 H).
(thin film) 2955, 2927, 1458, 1250, 990 cm
.
1H NMR (500
MHz, CDCl3) δ 7.86 (d, J ) 7.9 Hz, 4 H), 7.65 (dd, J ) 8.1, 1.6
Hz, 4 H), 7.14 (1/2 ABq, J ) 3.4 Hz, 4 H), 7.13 (1/2 ABq, J ) 3.4
Hz, 4 H), 6.98 (s, 4 H), 6.95 (d, J ) 1.4 Hz, 4 H), 6.89 (s, 4 H),
2.71 (t, J ) 7.7 Hz, 8 H), 2.67 (t, J ) 8.1 Hz, 8 H), 1.65-1.52
(m, 16 H), 1.36 (sext, J ) 7.7 Hz, 16 H), 0.91 (t, J ) 7.5 Hz, 12
H), 0.87 (t, J ) 7.4 Hz, 12 H), 0.31 (s, 36 H). 13C NMR (125
MHz, CDCl3) δ 149.9, 141.8, 141.6, 141.2, 140.8, 140.0, 134.8,
134.47, 134.45, 131.0, 130.7, 128.8, 127.3, 126.9, 126.2, 121.4,
121.1, 66.4, 33.2, 33.1, 29.8, 29.5, 23.2, 23.1, 14.39, 14.38, 0.4.
FAB/MS in (ONPOE) calcd relative isotopic intensities for
2,2′,7,7′-Tet r a k is(4′′-m et h ylp h en yl)-9,9′-sp ir ob iflu or -
en e (59). To a solution of 4-bromotoluene (1.97 mL, 16 mmol)
in ether (30 mL) was added at -78 °C tert-butyllithium (19.8
mL, 33.6 mmol, 1.7 M in pentane). The solution was stirred
at -78 °C for 1 h and transferred by use of a cannula into
annhydrous zinc chloride (3.05 g, 22.4 mmol) in THF (20 mL)
at room temperature. The resulting slurry was stirred for 1
h at room temperature and then transferred via cannula into
tetrakis(triphenylphosphine)palladium(0) (made from tris-
(dibenzylideneacetone)bispalladium(0) chloroform complex (0.03
g, 0.03 mmol) and triphenylphosphine (0.052 g, 0.2 mmol) in
THF) and 2,2′,7,7′-tetrabromo-9,9′-spirobifluorene (17) (0.632
g, 1.0 mmol) in THF (10 mL). The solution was heated to 55
°C for 16 h and cooled to room temperature. The solution was
poured into water, and the aqueous layer was extracted with
chloroform (3 × 5 mL). The combined organic layers were
washed with 3 N hydrochloric acid and water and dried over
magnesium sulfate. The solvent was removed, the resulting
black solid was dissolved in dichloromethane (10 mL) and
filtered through a plug of silica gel, and the solvent was
removed once again. The resulting solid was rinsed with
hexane (3 × 5 mL) and the hexane decanted. The solid was
purified by flash chromatography (silica gel, 2:1 chloroform:
hexane) to yield 0.47 g (70%) of the title compound as a white
C
117H136S12Si4 (M+): 2037 (51%), 2038 (83%), 2039 (100%),
2040 (89%), 2041 (67%), 2042 (43%), 2043 (25%), 2044 (13%),
2045 (6%). Found: 2037 (61%), 2038 (88%), 2039 (100%), 2040
(93%), 2041 (72%), 2042 (50%), 2043 (34%), 2044 (21%), 2045
(11%). Anal. Calcd for C117H136S12Si4: C, 68.96; H, 6.68.
Found: C, 68.14; H, 6.86.
2,2′,7,7′-Tetr a iod o-9,9′-sp ir obiflu or en e (62). To a solu-
tion of 9,9′-spirobifluorene (0.32 g, 1.0 mmol) in acetic acid (5
mL) and water (0.2 mL) at 80 °C were added concentrated
sulfuric acid (0.06 mL), iodic acid (0.28 g, 1.6 mmol), and iodine
(0.81 g, 3.2 mmol). The solution was stirred at 80 °C for 3 h,
and the resulting solid was filtered and washed with ethanol:
benzene (3:1) to afford 0.69 g (84%) of the title compound as a
white solid. FTIR (KBr) 3448, 1448, 1391, 1122, 1004, 809
cm-1 1H NMR (300 MHz, CDCl3) δ 7.71 (dd, J ) 8.1, 1.6 Hz,
.
4 H), 7.53 (d, J ) 8.1 Hz, 4 H), 6.98 (d, J ) 1.4 Hz, 4 H).
solid. FTIR (KBr) 3020, 2917, 1517, 1464, 1246, 1018, 806
-1
cm
.
1H NMR (300 MHz, CDCl3) δ 7.89 (d, J ) 7.9 Hz, 4 H),
7.60 (d, J ) 7.9 Hz, 4 H), 7.32 (d, J ) 8.1 Hz, 8 H), 7.09 (d, J
) 8.0 Hz, 8 H), 6.97 (s, 4 H), 2.28 (s, 12 H). HRMS calcd for
C53H40 676.3130, found 676.3134.
1-(Tr im eth ylsilyl)-2-(2′-th ien yl)a cetylen e. To a solution
of 2-bromothiophene (1.63 g, 0.97 mL, 10 mmol) in THF (10
mL) were added diisopropylamine (1.14 g, 1.58 mL, 11.2
mmol), (trimethylsilyl)acetylene (1.17 g, 1.69 mL, 12 mmol),
bis(triphenylphosphino)palladium(II) chloride (0.250 g, 0.36
mmol), and copper iodide (0.028 g, 0.15 mmol). The reaction
was stirred overnight before being poured into water. The
aqueous layer was extracted with dichloromethane, and the
organic extracts were washed with brine. The dichloromethane
layers were dried over sodium sulfate. The solvent was
removed by rotary evaporation, and the residue was purified
by plug filtration through silica gel (hexane) to provide 1.71 g
(95%) of the title product as a medium brown liquid. FTIR
(neat) 2959, 2147, 1514, 1421, 1250, 1164, 1140, 1076, 845,
2,2′,7,7′-Tetr a k is(4′′-(tr im eth ylsilyl)p h en yl)-9,9′-sp ir o-
biflu or en e (60).1hh To a solution of 1-bromo-4-(trimethylsi-
lyl)benzene (1.88 g, 8.2 mmol) in ether (15 mL) was added at
-78 °C tert-butyllithium (10.1 mL, 17.2 mmol, 1.7 M in
pentane). The solution was stirred at -78 °C for 1 h and
transfered via cannula into anhydrous zinc chloride (1.56 g,
11.5 mmol) in THF (10 mL) at room temperature. The
resulting slurry was stirred for 1 h at room temperature and
then transfered via cannula into tetrakis(triphenylphosphine)-
palladium(0) (made from tris(dibenzylideneacetone)bispal-
ladium(0) chloroform complex (15 mg, 0.014 mmol) and tri-
phenylphosphine (26 mg, 0.1 mmol) in THF) and 2,2′,7,7′-tet-
rabromo-9,9′-spirobifluorene (17) (0.312 g, 0.5 mmol) in THF
(5 mL). The solution was heated to 55 °C for 16 h and cooled
to room temperature. The solution was poured into water, and
the aqueous layer was extracted with chloroform (3 × 5 mL).
The combined organic layers rinsed with 3 N hydrochloric acid,
aqueous sodium bicarbonate, and brine and dried over mag-
nesium sulfate. The solvent was removed, and the resulting
black solid was dissolved in dichloromethane (10 mL) and
filtered through a plug of silica gel, and the solvent was
removed once again. The resulting solid was rinsed with
hexane (3 × 5 mL) and the hexane decanted off to afford 0.18
760, 700, 642 cm-1 1H NMR (300 MHz, CDCl3) δ 7.21 (d, J )
.
4.37 Hz, 2 H), 6.93 (app t, J ) 4.41 Hz, 1 H), 0.23 (s, 9 H).
2-Eth yn ylth iop h en e. To 1-(trimethylsilyl)-2-(2′-thienyl)-
acetylene (36.0 g, 200 mmol) in methanol (100 mL) was added
potassium carbonate (55.3 g, 400 mmol). The reaction was
stirred at room temperature for 30 min. The reaction was
poured into water, and the aqueous layer was extracted with
ether. The organic layer was dried over magnesium sulfate,
and the solvent was removed by distillation. The product was
distilled with a short path condensor to afford 21.4 g (98%) of
the title compound as a clear colorless oil. FTIR (neat) 3294,
3108, 2957, 2106, 1419, 1228, 1040, 853 cm-1 1H NMR (300
.
MHz, CDCl3) δ 7.27-7.26 (m, 2 H), 6.96 (ABq, J ) 5.2, 5.2
Hz, 1 H), 3.32 (s, 1 H), 0.05 (s, 9 H).
g (40%) of the title compound as a white solid. FTIR (KBr)
-1
2954, 1598, 1464, 1385, 1248, 1112, 850, 808 cm
.
1H NMR
(300 MHz, CDCl3) δ 7.91 (d, J ) 8.0 Hz, 4 H), 7.61 (d, J ) 7.9
Hz, 4 H), 7.45 (1/2ABq, J ) 8.3 Hz, 8 H), 7.40 (1/2ABq, J ) 8.8
Hz, 8 H), 6.98 (s, 4 H), 0.20 (s, 36 H). 13C NMR (125 MHz,
CDCl3) δ 150.2, 141.8, 141.5, 141.2, 139.6, 134.1, 127.4, 126.9,
123.5, 120.8, 66.6, -0.7. HRMS calcd for C61H64Si4 908.4085,
found 908.4102.
2,2′,7,7′-Tet r a k is(4,4′-d ib u t yl-5′′-(t r im et h ylsilyl)-5,2′:
5′,2′′-ter th iop h en e)-9,9′-sp ir obiflu or en e (61).1hh To a solu-
tion of 2,2′,7,7′-tetrabromo-9,9′-spirobifluorene (17) (0.063 g,
0.1 mmol) and 2-(tri-n-butylstannyl)-4,4′-di-n-butyl-5′′-(tri-
methylsilyl)-5,2′:5′,2′′-terthiophene (40b) (0.65 g, 0.9 mmol) in
toluene (1 mL) under a nitrogen atmosphere was added
tetrakis(triphenylphosphine)palladium(0) (9.3 mg, 0.008 mmol).
The reaction was heated to 100 °C for 2.5 days and then cooled
to room temperature. The reaction was poured into water,
and the aqueous layer was extracted with dichloromethane
(3 × 10 mL). The organic layer was dried over magnesium
sulfate, and the product was purified by flash chromatography
(silica gel, 9:1 hexane:dichloromethane) and dried in vacuo to
afford 0.123 g (60%) of the title compound as a bright orange
2,2′,7,7′-Tet r a k is(1′′-(2′′′-t h ien yl)et h yn yl)-9,9′-sp ir ob i-
flu or en e (63). To an oven-dried flask containing bis(diben-
zylideneacetone)bispalladium(0) (11.4 mg, 0.02 mmol), tri-
phenylphosphine (26.2 mg, 0.1 mmol), copper(I) iodide (7.6 mg,
0.04 mmol), 62 (82 mg, 0.1 mmol), and 2-ethynylthiophene
(0.43 g, 4.0 mmol) in THF (1 mL) was added diisopropylamine
(1 mL). The reaction was heated to 60 °C for 48 h and poured
into water. The organic layer was extracted with dichlo-
romethane (3 × 10 mL), and the organic layer was dried over
magnesium sulfate. The crude sample was purified by flash
chromatography (silica gel, 3:1 hexane:dichloromethane) to
yield 72.1 mg (97%) of the title compound as a brown solid.
FTIR (KBr) 2925, 2198, 1465, 1414, 1218 cm-1 1H NMR (300
.
MHz, CDCl3) δ 7.81 (d, J ) 8.0 Hz, 4 H), 7.55 (dd, J ) 7.9, 1.4
Hz, 4 H), 7.21 (dd, J ) 5.1, 1.1 Hz, 4 H), 7.15 (dd, J ) 3.6, 1.1
Hz, 4 H), 6.93 (dd, J ) 5.1, 3.7 Hz, 4 H). 13C NMR (75 MHz,
CDCl3) δ 148.2, 141.2, 131.9, 131.7, 127.4, 127.1, 123.1, 122.8,
120.5, 96.1, 93.1, 83.6, 65.2. HRMS calcd for C49H24S4 740.0761,
found 740.0766.

Orthogonally Fused Conjugated Oligomers
J . Org. Chem., Vol. 61, No. 20, 1996 6921
Com p ou n d 64. 62 (0.12 g, 0.15 mmol) was added to a
solution of 57 (0.38 g, 4.0 mmol) in THF (1 mL). Diisopropyl-
amine (0.10 g, 1 mL, 7.14 mmol), bis(triphenylphosphino)-
palladium(II) chloride (0.03 g, 0.04 mmol), and copper iodide
(0.01 g, 0.05 mmol) (both metal catalysts were degassed in a
vacuum chamber for 2 h immediately before the addition) were
then added. The reaction was allowed to stir at room tem-
perature for 2 d. The reaction was then quenched with water,
and the organic layer was extracted with dichloromethane
(3×). The combined organic extracts were washed with brine.
The organic phase was dried over magnesium sulfate. The
solvent was removed by rotary evaporation, and the residue
was purified by flash chromatography on silica gel. The eluent
was initially hexane and then increased to 9:1 hexane-
dichloromethane and finally to 7:3 hexane-dichloromethane
to provide the title product (0.29 g, 78%) as a red-orange solid.
UV (dichloromethane) λmax 422 nm. FTIR (neat) 2969, 2934,
124.34, 123.78, 123.24, 123.14, 120.98, 120.29, 119.80, 119.31,
117.66, 97.17, 90.15, 89.83, 88.67, 87.54, 87.07, 86.74, 83.39,
65.62, 23.39, 23.28, 15.06, 14.91, 14.88. Anal. Calcd for
C153H112S16: C, 74.59; H, 4.58. Found: C, 74.46; H, 4.69.
Ack n ow led gm en t. Initial phases of this work were
supported by the Office of Naval Research and the
National Science Foundation. The present work is
supported by the Advanced Research Projects Agency.
We thank Farchan Laboratories for a gift of (trimeth-
ylsilyl)acetylene, FMC Corporation for a gift of alkyl-
lithium reagents, and Molecular Design Ltd. for the use
of their synthetic data base.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra for
compounds 10-12, 14, 23, 26, 27, 39a , 39b, 40a , 40b, 41-
46, 49-57, 59, 60, 62, and 63 (30 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
2875, 2248, 2188, 1461, 907, 734 cm-1
.
1H NMR (300 MHz,
CDCl3) δ 7.82 (d, J ) 7.92 Hz, 4 H), 7.54 (d, J ) 7.85 Hz, 4 H),
7.20 (d, J ) 5.12 Hz, 4 H), 7.04 (s, 4 H), 7.03 (s, 4 H), 7.01 (s,
4 H), 6.90 (d, J ) 5.17 Hz, 4 H), 6.89 (s, 4 H), 2.70 (overlapping
q, J ) 7.6 Hz, 32 H), 1.22 (overlapping t, J ) 7.6 Hz, 48 H).
13C NMR (125 MHz, CDCl3) δ 150.24, 150.00, 149.94, 149.46,
148.51, 141.63, 132.93, 132.63, 132.32, 128.27, 127.37, 127.17,
J O960897B