Carbon networks based on dehydrobenzoannulenes. 4. Synthesis of "star" and "trefoil" graphdiyne substructures via sixfold cross-coupling of hexaiodobenzene

Article abstract of DOI:10.1021/jo010183n

The synthesis and characterization of star- and trefoil-shaped polyethynyl aromatic structures, which represent model substructures of the all-carbon network graphdiyne, are described. Assembly of these macrocycles is accomplished via 6-fold Sonogashira cross-coupling of hexaiodobenzene using Pd[P(o-Tol)₃]₂ and CuI as the catalytic system. The development of these modified Sonogashira conditions is detailed. This work has led to the synthesis of a new family of hexakis(phenylbutadiynyl)benzene derivatives (4a-c), the largest of which is the D_3h-symmetric "trefoil" 2 and is composed of three [18]annulenes fused at a common benzene ring. Attempts at the synthesis of "wheel" 3 are also described. Compound 2 represents the largest fragment of the graphdiyne network to date. UV-vis spectroscopic studies indicate enhanced electron delocalization throughout the extended π-system.

Full text of DOI:10.1021/jo010183n

J . Org. Chem. 2001, 66, 3893-3901
3893
Ca r bon Netw or k s Ba sed on Deh yd r oben zoa n n u len es. 4. Syn th esis
of “Sta r ” a n d “Tr efoil” Gr a p h d iyn e Su bstr u ctu r es via Sixfold
Cr oss-Cou p lin g of Hexa iod oben zen e
W. Brad Wan and Michael M. Haley*
Department of Chemistry and the Materials Science Institute, University of Oregon,
Eugene, Oregon 97403-1253
haley@oregon.uoregon.edu
Received February 16, 2001
The synthesis and characterization of star- and trefoil-shaped polyethynyl aromatic structures,
which represent model substructures of the all-carbon network graphdiyne, are described. Assembly
of these macrocycles is accomplished via 6-fold Sonogashira cross-coupling of hexaiodobenzene using
Pd[P(o-Tol)3]2 and CuI as the catalytic system. The development of these modified Sonogashira
conditions is detailed. This work has led to the synthesis of a new family of hexakis(phenylbuta-
diynyl)benzene derivatives (4a -c), the largest of which is the D3h-symmetric “trefoil” 2 and is
composed of three [18]annulenes fused at a common benzene ring. Attempts at the synthesis of
“wheel” 3 are also described. Compound 2 represents the largest fragment of the graphdiyne network
to date. UV-vis spectroscopic studies indicate enhanced electron delocalization throughout the
extended π-system.
In tr od u ction
In a prior publication, we discussed the synthesis and
properties of several related graphdiyne subunits, most
of which were constructed from tetraiodobenzenes.1b The
next logical step is the preparation of a class of larger,
more complex analogues of HEBs“trefoil” 2 and “wheel”
3, the core of which is “star” molecule 4. In theory,
derivatives of 4 could be readily assembled by affixing 6
equiv of a phenylbutadiyne species to hexaiodobenzene7
via common Pd-catalyzed cross-coupling conditions. In
practice, this required substantial experimentation and
modification of the Sonogashira alkynylation protocol.8
There are several publications describing the prepara-
tion of HEB derivatives.9 For molecules possessing D6h
symmetry,5,9a-c the simplest systems, the synthetic pro-
cedures are specific for certain substrate/coupling partner
combinations. Difficulties often arise (primarily incom-
plete addition) when adapting these conditions to other
reactants.10 In 1992, Vollhardt et al. reported the first
and only published synthesis of hexabutadiynylbenzene
derivatives.11 Using high-temperature Sonogashira con-
ditions, they prepared 5a -c in low to modest yield.
Similar to the monoalkyne counterparts, Vollhardt and
As part of our ongoing work toward the synthesis and
study of nonnatural carbon networks,1 we have focused
on the preparation of increasingly larger fragments of
graphdiyne (1).2 Such molecules fall under the category
of electron-rich, reactive hydrocarbons with high C:H
ratios and can serve as precursors or mimics of carbon
allotropes (e.g., graphdiyne).3 Furthermore, their ex-
tended π-conjugation may give rise to interesting materi-
als properties such as high third-order nonlinear optical
(NLO) susceptibility and novel discotic liquid crystalline
behavior.2,4 Hexaethynylbenzene (HEB)5 would be the
ideal monomer for graphdiyne; however, the high reac-
tivity of this molecule results in random cross-linking and
incomplete cross-coupling, eliminating it as a viable
network scaffold. Instability problems also complicate
and often prevent extensive synthetic studies with the
molecule. Only computational chemistry has allowed
insight into the interesting electronic and magnetic
properties of HEB.6
(1) (a) Haley, M. M.; Pak, J . J .; Brand, S. C. Angew. Chem., Int. Ed.
Engl. 1997, 36, 836-838. (b) Wan, W. B.; Pak, J . J .; Brand, S. C.; Haley,
M. M. Chem. Eur. J . 2000, 6, 2044-2052. (c) Haley, M. M.; Wan, W.
B. In Advances in Strained and Interesting Organic Molecules; Halton,
B., Ed.; J AI Press: Greenwich, 2000; Vol. 8, pp 1-41.
(6) (a) Fowler, P. W.; Steiner, E.; Zanasi, R.; Cadioli, B. Mol. Phys.
1999, 96, 1099-1108. (b) Marguet, S.; Germain, A.; Millie, P. Chem.
Phys. 1996, 208, 351-373.
(7) Mattern, D. L.; Chen, X. J . Org. Chem. 1991, 56, 5903-5907.
(8) Sonogashira, K. In Metal-Catalyzed Cross-Coupling Reactions;
Stang, P. J ., Diederich, F., Eds.; VCH: Weinheim, 1997; Chapter 5.
(9) (a) Whitesides, G. M.; Neenan, T. X. J . Org. Chem. 1988, 53,
2489-2496. (b) Heck, R. F.; Nesbitt, S.; Tao, W. J . Org. Chem. 1990,
55, 63-69. (c) Praefcke, K.; Kohne, B.; Singer, D. Angew. Chem., Int.
Ed. Engl. 1990, 29, 177-179. (d) Anthony, J . E.; Khan, S. I.; Rubin,
Y. Tetrahedron Lett. 1997, 38, 3499-3502. (e) Tobe, Y.; Kubota, K.;
Naemura, K. J . Org. Chem. 1997, 62, 3430-3431. (f) Tovar, J . D.; J ux,
N.; J arrosson, T.; Khan, S. I.; Rubin, Y. J . Org. Chem. 1997, 62, 3432-
3433.
(2) (a) Baughman, R. H.; Eckhardt, H.; Kerte´sz, M. J . J . Chem. Phys.
1987, 87, 6687-6699. (b) Narita, N.; Nagagi, S.; Suzuki, S.; Nakao, K.
Phys. Rev. B 1998, 58, 11009-11014.
(3) Inter alia: (a) Balaban, A. T.; Rentia, C. C.; Ciupitu, E. Rev.
Roum. Chim. 1968, 13, 231-247. (b) Diederich, F. Nature 1994, 369,
199-207. (c) Bunz, U. H. F.; Rubin, Y.; Tobe, Y. Chem. Soc. Rev. 1999,
28, 107-119. (d) Berresheim, A. J .; Mu¨ller, M.; Mu¨llen, K. Chem. Rev.
1999, 99, 1747-1786.
(4) (a) Kumar, S.; Varshney, S. K. Angew. Chem., Int. Ed. 2000, 39,
3140-3142. (b) Collings, P. J .; Hird, M. In Introduction to Liquid
Crystals - Chemistry and Physics; Taylor and Francis: Bristol, PA,
1997; Chapter 4. (c) Ebert, M.; J ungbauer, D. A.; Kleppinger, R.;
Wendorff, J . H.; Kohne, B.; Praefcke, K. Liq. Cryst. 1989, 4, 53-67.
(5) Diercks, R.; Armstrong, J . C.; Boese, R.; Vollhardt, K. P. C.
Angew. Chem., Int. Ed. Engl. 1986, 36, 268-269.
(10) Representative examples include: (a) Mongin, M.; Hoyler, N.;
Gossauer, A. Eur. J . Org. Chem. 2000, 1193-1197. (b) Kayser, B.;
Altman, J .; Beck, W. Chem. Eur. J . 1999, 5, 754-758.
(11) Boese, R.; Green, J . R.; Mittendorf, J .; Mohler, D. L.; Vollhardt,
K. P. C. Angew. Chem., Int. Ed. Engl. 1992, 31, 1643-1645.
10.1021/jo010183n CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/03/2001

3894 J . Org. Chem., Vol. 66, No. 11, 2001
Wan and Haley
Sch em e 1a
a
Key: (a) Me3SiCtCCtCH, PdCl2(PPh3)2, CuI, Et3N; (b)
K2CO3, MeOH, THF, Et2O; (c) C6I6, Pd[P(o-Tol)3]2, CuI, Et3N,
NMP.
species are generated in situ under Sonogashira condi-
tions.1,13 In this manner the concentration of the unstable
diyne at any given time is low, and thus this reactive
species has the opportunity to cross-couple to the halo-
arene substrate before decomposition. The in situ protio-
desilylation/alkynylation approach is quite effective for
the construction of graphdiyne fragments containing
butadiyne linkages,1 as well as for the assembly of a wide
variety of dehydrobenzoannulenes.13 Consequently, we
hoped that this technique could be applied to the prepa-
ration of hexabutadiynylbenzene derivatives such as 4a -
c, and thus 2 and 3.
Resu lts a n d Discu ssion
Syn th esis of Sta r -Sh a p ed Su bu n its. Coupling part-
ners 6a -c were quickly assembled via Sonogashira
coupling of (trimethylsilyl)butadiyne12 with the requisite
iodobenzenes (Scheme 1). The initial target was do-
decayne 4a , which could be constructed by reacting 6a
with C6I6 via the aforementioned in situ desilylation/
alkynylation procedure. Despite numerous attempts, the
results were less than satisfactory. The majority of
material recovered was a mixture of 4-fold- and 5-fold-
coupled products with no evidence of the formation of 4a .
In addition, a significant amount of crystalline material
was obtained, which upon further inspection proved to
be pure, stable crystals of diyne 7a . This result was
surprising given the reported instability problems of
other phenylbutadiyne derivatives.1,12,13 At this point we
cannot offer a logical explanation for the stability of 7a ,
especially considering the fact that both 7b and 7c were
found to be considerably less stable. Despite numerous
perturbations of various reaction conditions (reaction
times, temperature, pressure, solvent(s), choice of amine,
catalyst loading, etc.), complete addition was never
(12) Brandsma, L. Preparative Acetylenic Chemistry; Elsevier: Am-
sterdam, 1971. The first edition contained the preparation of 1-phenyl-
1,3-butadiyne, but stated that the molecule proved to be very unstable.
This procedure was deleted from the second edition (1988). (b) Other
groups have reported similar problems using free phenylbutadiynes
in synthesis: Godt, A. J . Org. Chem. 1997, 62, 7471-7474. (c) Use of
tin butadiynes: Bunz, U. H. F.; Enkelmann, V. Organometallics 1994,
13, 3823-3833.
(13) (a) Haley, M. M.; Pak, J . J .; Brand, S. C. Top. Curr. Chem. 1999,
201, 81-130. (b) Haley, M. M.; Bell, M. L.; English, J . J .; J ohnson, C.
A.; Weakley, T. J . R. J . Am. Chem. Soc. 1997, 119, 2956-2957. (c)
Wan, W. B.; Kimball, D. B.; Haley, M. M. Tetrahedron Lett. 1998, 39,
6795-6798. (d) Pak, J . J .; Weakley, T. J . R.; Haley, M. M. J . Am. Chem.
Soc. 1999, 121, 8182-8192. (e) Sarkar, A.; Haley, M. M. J . Chem. Soc.,
Chem. Commun. 2000, 1733-1734. (f) Bell, M. L.; Chiechi, R. C.;
English, J . J .; J ohnson, C. A.; Kimball, D. B.; Matzger, A. J .; Wan, W.
B.; Weakley, T. J . R.; Haley, M. M. Tetrahedron, in press.
co-workers were limited specifically to these three sys-
tems, purportedly due to the instability of other butadiyne
species. In particular, they were unable to obtain phenyl-
butadiyne derivatives such as 4a -c, which are essential
for the preparation of 2 and/or 3.12 Previously we have
relied on a method in which reactive phenylbutadiyne

Carbon Networks Based on Dehydrobenzoannulenes. 4
J . Org. Chem., Vol. 66, No. 11, 2001 3895
Sch em e 2
Sixfold cross-coupling using Pd[P(o-Tol)3]2 and stable
butadiyne 7a furnished 4a in 42% yield (Scheme 1). The
structure was confirmed by NMR spectroscopy, matrix-
assisted laser desorption time-of-flight (MALDI-TOF)
mass spectrometry, and X-ray crystallography. The crys-
tal structure (see Supporting Information) confirmed the
correct connectivity; however, poor diffraction of the
crystals precluded accurate structural details save that
the molecule is highly disordered with respect to the
orientation of the phenyl rings and the tert-butyl sub-
stituents.
While this new catalytic system was effective for the
formation of 4a , the reaction conditions needed to be
modified for the coupling of more reactive species, such
as 7b,c. Unfortunately, Pd[P(o-Tol)3]2 proved to be un-
stable or ineffective under the basic conditions (KOH and
K2CO3) required for the in situ deprotection. It was
therefore necessary to abandon the in situ method and
readdress ways to generate and/or manipulate free
diynes. As mentioned previously, phenylbutadiyne de-
rivatives have historically been too reactive to isolate,
with 7a being a rare exception. Inspired by the robust
nature of 7a , we reinvestigated the stability of our di-
acetylene moieties and determined that several phenyl-
butadiyne derivatives are in fact moderately stable. If
handled carefully (dilute solution, minimal exposure to
oxygen), it is possible to manipulate these highly reactive
species for short periods of time. As expected, there is a
direct correlation between phenylbutadiyne stability and
product yield (tBu . nDec > OMe). The general proce-
dure used to achieve the 6-fold Sonogashira coupling is
as follows: the trimethylsilyl protecting group of butadiyne
species 6a -c was removed upon treatment with metha-
nolic K2CO3. Upon careful workup, the deprotected
material (10 equiv) was concentrated, Et3N was added,
and the mixture was deoxygenated thoroughly with
bubbling nitrogen. The deprotected butadiyne solution
was then added to a deoxygenated N-methylpyrrolidinone
(NMP) suspension of C6I6 and catalysts (3% Pd[P(o-Tol)3]2
and ca. 10% CuI per iodine).17 The reaction mixture was
stirred overnight at 60 °C under a dry N2 atmosphere.
After routine workup and purification, model systems
4a -c were isolated in low to moderate yields. Although
optimization of the reaction conditions is still ongoing,
these results were encouraging enough to proceed with
the assembly of 2 and 3.
achieved, even after abandoning the in situ approach. In
the past we have relied heavily upon PdCl2(PPh3)2 as the
catalyst in our cross-coupling reactions. The fact that
predominantly unreacted phenylbutadiyne was recovered
consistently, however, indicated that the catalyst was
insufficiently active under these reaction conditions and
that other options needed to be explored.
One particular catalyst that has garnered considerable
attention in recent literature is Pd[P(o-Tol)3]2.14 This
highly coordinatively unsaturated Pd species is more
commonly employed in Heck reactions and Stille cou-
plings and is rather unorthodox for use in Sonogashira
couplings. The catalyst is typically generated in situ by
the addition of Pd(dba)2 and P(o-Tol)3 to the reaction
mixture; however, Hartwig et al. recently reported a
method to synthesize and isolate the Pd[P(o-Tol)3]2
catalyst as stable yellow crystals.14a The bulk of the work
in this report was carried out with the preformed version
of the catalyst.
A simplified coupling cycle, based on one proposed by
Hartwig, is shown in Scheme 2.14b The most significant
difference between PdCl2(PPh3)2 and Pd[P(o-Tol)3]2 is the
cone angle of the phosphine ligands (PPh3 ) 145°, P(o-
Tol)3 ) 195°).15 To accommodate the bulkier P(o-Tol)3
ligands, the palladium-phosphorus bond must be elon-
gated and therefore is weakened. As a result, the larger
phosphine is much more labile and readily dissociates
to create a highly coordinatively unsaturated species that
is more reactive than PdCl2(PPh3)2. More importantly,
this species is much less sterically hindered, having only
one remaining ligand. Therefore, it should be much easier
for an iodoarene to undergo oxidative addition to the
active palladium species, transmetalation to introduce
the alkyne moiety, and reductive elimination to generate
the desired product.16
Syn th esis of Tr efoil-Sh a p ed Su bu n its. Construc-
tion of macrocycles 2 and 3 required the preparation of
the necessary phenylbutadiyne derivatives, i.e., triyne 8
and tetrayne 9, respectively (Scheme 3). Solubilizing
alkyl groups were engineered into 8 and 9 to combat
anticipated solubility problems. Treatment of 4-tert-
butylaniline with 1 equiv of (BnEt3N)‚ICl2 gave iodo-
aniline 10 as a viscous red oil in 90% yield.18 Conversion
of the amino group to a diethyltriazene furnished 11 in
92% yield.19 Pd-catalyzed alkynylation of triazene 11 with
(triisopropylsilyl)acetylene afforded 12, which was con-
verted to the corresponding iodoarene upon treatment
with iodomethane at 120 °C.19 Cross-coupling of 13 with
excess (trimethylsilyl)butadiyne produced triyne 8a in
(14) (a) Paul, F.; Patt, J .; Hartwig, J . F. Organometallics 1995, 14,
3030-3039. (b) Hartwig, J . F.; Paul, F. J . Am. Chem. Soc. 1995, 117,
5373-5374. (c) Hartwig, J . F.; Paul, F.; Richards, S.; Baranano, D. J .
Am. Chem. Soc. 1996, 118, 3626-3633. (d) Wagaw, S.; Rennels, R. A.;
Buchwald, S. L. J . Am. Chem. Soc. 1997, 119, 8451-8458. (e) Farina,
V.; Krishnan, B. J . Am. Chem. Soc. 1991, 113, 9585-9595.
(15) Tolman, C. A. Chem. Rev. 1977, 77, 313-348.
(16) The use of the bulky, electron-rich phosphine P(t-Bu)3 in
Sonogashira reactions was recently reported. (a) Hundertmark, T.;
Littke, A. F.; Buchwald, S. L.; Fu, G. C. Org. Lett. 2000, 2, 1729-
1731. (b) Bo¨hm, V. P. W.; Herrmann, W. A. Eur. J . Org. Chem. 2000,
3679-3681.
(17) Allow catalysts to stir with C6I6 for ca. 30 min prior to addition
of acetylene. NMP was used as solvent (50 mL per mmol C6I6).
(18) Kajigaeshi, S.; Kakinami, T.; Yamasaki, H.; Fujisaki, S.;
Okamoto, T. Bull. Chem. Soc. J pn. 1988, 61, 600-603.
(19) Moore, J . S.; Weinstein, E. J .; Wu, Z. Tetrahedron Lett. 1991,
32, 2465-2466.

3896 J . Org. Chem., Vol. 66, No. 11, 2001
Wan and Haley
Sch em e 3a
Sch em e 5a
a
Key: (a) K2CO3, MeOH, THF; (b) C6I6, Pd[P(o-Tol)3]2, CuI,
Et3N, NMP; (c) Bu4NF, EtOH, THF; (d) CuCl, Cu(OAc)2‚H2O,
pyridine.
tions. Workup and removal of the solvent produced after
purification a poorly soluble, amorphous powder. MALDI-
TOF MS suggested the formation of the desired product
(2a ), but owing to poor solubility in common organic
solvents, indisputable characterization by other spectro-
scopic techniques was not possible.
In contrast, attempts to couple 7b to C6I6 using the
same procedure failed to produce the pure n-decyl
precursor 18b. Despite various separation techniques, the
desired product was consistently contaminated with
5-fold material in which the sixth iodine was displaced
with a hydrogen atom, as indicated by MALDI-TOF MS
and 1H NMR spectroscopy. Unfortunately, it was not
possible to estimate the ratio of 5-fold to 6-fold material
from the available information. The resulting mixture
was subjected to cyclization as described above. The
desired product 2b, which was much more soluble than
its tert-butyl counterpart 2a , was isolated in 6% overall
yield as an amorphous yellow solid. The identity of the
product was confirmed by 1H NMR spectroscopy and
MALDI-TOF mass spectrometry.
a
Key: (a) (BnEt3N)‚ICl2, CH2Cl2, CaCO3, MeOH; (b) [i] NaNO2,
HCl, H2O, CH3CN, THF, Et2O; [ii] Et2NH, K2CO3, H2O, CH3CN;
(c) i-Pr3SiCtCH, PdCl2(PPh3)2, CuI, Et3N; (d) MeI, 120 °C; (e)
Me3SiCtCCtCH, PdCl2(PPh3)2, CuI, Et3N.
Sch em e 4a
Attem p ted Syn th esis of Wh eel-Sh a p ed Su bu n its.
The ultimate example in this series would be the syn-
thesis of 3; however, after numerous attempts, results
have been inconclusive (Scheme 5). Coupling phenyl-
butadiyne derivative 9b to C6I6 using the newly devel-
oped reaction conditions resulted in the isolation of a
material (19) that was found (MALDI-TOF MS) to have
a molecular weight of 3507 amu (theoretical 3829 amu).
This is too large to be 5-fold material (3330 amu), but
presently we are unable to justify the fragmentation
a
Key: (a) K2CO3, MeOH, THF; (b) C6I6, Pd[P(o-Tol)3]2, CuI,
Et3N, NMP; (c) Bu4NF, EtOH, THF; (d) CuCl, Cu(OAc)2‚H2O,
pyridine.
90% yield. Tetrayne 9a , which is structurally similar, is
assembled by following virtually the same pathway (14
f 17) in approximately 40% overall yield, with the
exception of using 2 equiv of the appropriate reagents in
steps a and c (Scheme 3). The corresponding n-decyl
counterparts (triyne 8b and tetrayne 9b) were prepared
by using the same strategy.1b
It seemed reasonable that the desilylation of 8a , owing
to its structural similarity to 7a , should furnish a
phenylbutadiyne derivative of similar stability. Treat-
ment of triyne 8a with K2CO3 in methanol selectively
removed the more labile trimethylsilyl protecting group.
The deprotected triyne was successfully coupled to C6I6
as described above to give 18a as yellow needles in ca.
30% yield (Scheme 4). Although the crystals were unsuit-
able for X-ray crystallography, the correct structure was
positively confirmed by 1H and 13C NMR spectroscopy and
by mass spectrometry (FAB and MALDI-TOF). Precursor
18a was treated with Bu4NF to remove the triisopropyl-
silyl protecting groups, dissolved in pyridine, and added
slowly via syringe pump to a suspension of CuCl and
Cu(OAc)2 in pyridine under pseudo-high dilution condi-
1
pattern. The H NMR spectrum showed two singlets in
the aromatic region, as well as two discrete -Sii-Pr3
resonances. This may be because of an unexpected
shielding effect, or perhaps the material is simply an
impure mixture of 5-fold and 6-fold material (similar to
18b). Molecular modeling supports both of these argu-
ments.20 The six arms of 19 are perpendicular to the
central benzene ring; thus, the -Sii-Pr3 groups are held
close to the shielding zone of this arene. In addition, the
steric bulk offered by the many -Sii-Pr3 units might
prevent the transmetalation needed to introduce the
sixth arm. Regardless, protiodesilylation and copper-
mediated cyclization of this material furnished an amor-
phous orange-yellow powder. Analysis by MALDI-TOF
MS gave a peak at 2304 amu (theoretical 1940 amu).
Similar to 2a , the poor solubility of this material pre-
cluded acquisition of meaningful NMR data. At this point,
(20) PM3 calculations were performed on an SGI workstation using
Spartan software (Version 5.0).

Carbon Networks Based on Dehydrobenzoannulenes. 4
J . Org. Chem., Vol. 66, No. 11, 2001 3897
it is unlikely that 3b will be prepared via this route; we
are currently investigating alternative synthetic path-
ways for 3.
Sp ectr oscop ic a n d P h ysica l P r op er ties. The mate-
rial properties of the molecules presented in this report
will likely arise from the extended π-conjugation and
enhanced electron delocalization of these star-shaped
systems. The amount of delocalization can be qualita-
tively observed by comparing the electronic absorption
spectra of several similar substructures. In 1995, Kondo
et al. reported the UV-vis spectra and the third-order
NLO properties of a series of phenylethynyl-substituted
benzene systems (20-22).21 The trend of λmax was 300,
315, and 350 nm, respectively. These results demon-
strated a correlation between the number of chromo-
phores per molecule and the absorbance frequency, and
also length of conjugation. Their results established that
third-order NLO susceptibility, ø(3), increases with con-
jugation length. In addition, this class of molecules
exhibits a third-order response comparable to that of
other organic third-order NLO compounds, including
π-conjugated polymers, organic photoconductors, and
organic charge-transfer conducting complexes.22
F igu r e 1. Electronic absorption spectra of molecules 2b, 4a ,
4c, and 18a .
and 18 will generate third-order NLO responses equal
to, if not greater than, that of 22.
Upon closure of 18b to generate 2b, a strong batho-
chromic shift (25-30 nm) is observed in the UV-vis
spectrum (Figure 1). Closure of the three [18]annulene
rings locks the entire macrocycle into planarity, which
enhances delocalization in the extended π-system and
should further enhance the NLO response. The absorp-
tion pattern is altered slightly by intensification of the
second peak, now λmax (442 nm), and by appearance of a
third peak at 423 nm. Interestingly, the UV-vis pattern
of 2b more closely resembles structures 4a -c and 18a
than previous graphdiyne subunits (e.g., 23-24) as the
characteristic pattern associated with the dodecadehydro-
[18]annulene core (Figure 2) is no longer discernible.1b
Molecules 4a -c can be viewed as elongated derivatives
of 22 with superior π-conjugation lengths where the
active chromophore is 1,4-bis(phenylbutadiynyl)benzene.
As a result, the UV-vis absorbances occur at consider-
ably longer wavelengths (Figure 1). The spectra for 4a ,
4b (not shown), and 18a are virtually identical, possess-
ing a characteristic pattern with λmax at ca. 385 nm and
a second peak of slightly lower intensity at ca. 415 nm.
The spectrum of 4c shows a similar pattern, but both
peaks are slightly red-shifted (ca. 11-13 nm), which is
the expected effect of the electron-donating methoxy
group. On the basis of these results, it is very likely that
the hexakis(phenylbutadiynyl)benzene structures 4a -c
Consistent with our previous studies of graphdiyne
substructures1 and other planar dehydrobenzoannu-
lenes,13c,f the benzene proton resonances of 2b are shifted
downfield (∆δ ≈ 0.15-0.35 ppm) relative to its acyclic
precursor, indicating the presence of a weak diatropic
ring current in the [18]annulene rings. Comparison of
these resonances with those on the “bay” arenes of 24
reveals only a very slight downfield shift (0.02-0.04 ppm)
and thus may be another indicator of the enhanced
delocalization observed in the UV-vis spectra.
DSC analysis of the polyynes showed the molecules to
be extremely reactive, displaying irreversible exotherms
prior to melting (150-250 °C). The reactions occurred
over a 20-40 °C range in all cases, which is indicative of
(21) Kondo, K.; Yasuda, S.; Tohoru, S.; Miya, M. J . Chem. Soc.,
Chem. Commun. 1995, 55-56.
(22) Inter alia: (a) Molecular Nonlinear Optics - Materials, Physics
and Devices; Zyss, J ., Ed.; Academic Press: San Diego, CA, 1994. (b)
Kanis, D. R.; Ratner, M. A.; Marks, T. J . Chem. Rev. 1994, 94, 195-
242. (c) Nonlinear Optics of Organic Molecules and Polymers; Nalwa,
H. S., Miyata, S., Eds.; CRC Press: New York, 1997. (d) Wolff, J . J .;
Wortmann, R. In Advances in Physical Chemistry; Bethell, D., Ed.;
Academic Press: London, UK, 1999; Vol. 32, pp 121-217.

3898 J . Org. Chem., Vol. 66, No. 11, 2001
Wan and Haley
station (MALDI-TOF) with 2,5-dihydroxybenzoic acid as ma-
trix (calibrated with C60 and C70). DSC analyses were per-
formed using a TA Instruments DSC 2920 Modulated DSC.
Elemental analyses were performed by Robertson Microlit
Laboratories, Inc. Melting points were determined on
a
Meltemp II apparatus and are uncorrected. CH2Cl2 and Et3N
were distilled from CaH2 under a nitrogen atmosphere prior
to use. THF and Et2O were distilled from sodium and benzo-
phenone under a nitrogen atmosphere prior to use. All other
chemicals were of reagent quality and used as obtained from
manufacturers. Reactions were carried out in an inert atmo-
sphere (dry nitrogen or argon) when necessary. Column
chromatography was performed on Whatman reagent grade
silica gel (230-400 mesh). Preparative radial thin-layer chro-
matography was performed on a Chromatotron using silica gel
(60 PF254) plates (1-4 mm). Precoated silica gel plates (EM
Separations Technology, 60 PF254, 200 × 50 × 0.20 mm) were
used for analytical thin-layer chromatography.
Gen er a l Acetylen e Cou p lin g P r oced u r e A. A suspension
consisting of iodoarene (1 equiv), PdCl2(PPh3)2 (0.03 equiv),
and CuI (0.06 equiv) in Et3N was deoxygenated by bubbling
nitrogen or by the method of freeze-pump-thaw. The termi-
nal acetylene (1.5 equiv per iodine) was added in three portions
at 1 h intervals with stirring at 60 °C under nitrogen. Upon
completion, the reaction mixture was concentrated in vacuo,
suspended in CH2Cl2, and filtered through a bed of silica gel.
The filtrate was concentrated, and the desired product was
purified by column chromatography on silica gel or by Chro-
matotron.
Gen er a l Sixfold Cou p lin g P r oced u r e B. The appropriate
(trimethylsilyl)butadiyne (10 equiv relative to C6I6) was dis-
solved in a solution of THF, Et2O, and MeOH (6:3:1 v:v, 25
mL per mmol). K2CO3 (2 equiv) was added, and the reaction
was stirred vigorously for 1 h. Upon completion, the depro-
tected material was extracted into hexanes, washed with water
and brine, and dried (MgSO4). The solution was filtered and
concentrated under reduced pressure to approximately 10%
of the original volume. Distilled Et3N (2 mL) was added, and
the mixture was deoxygenated thoroughly by nitrogen bub-
bling for 10 min. In a separate flask were placed C6I6 (1 equiv),
Pd[P(o-Tol)3]2 (15 mol %), CuI (50 mol %), and NMP (50 mL
per mmol C6I6), and the mixture was deoxygenated for 30 min.
The deprotected butadiyne solution was added to a C6I6/
catalyst mixture, and the reaction was stirred overnight at
60 °C under nitrogen. Upon completion, the reaction mixture
was diluted with CH2Cl2 and washed with a 10% HCl solution.
The organic layer was washed with water, dried (MgSO4),
filtered, and concentrated under vacuum. The residue was
preabsorbed onto silica gel and was purified by column
chromatography.
Gen er a l Ar yl Dieth yltr ia zen e F or m a tion P r oced u r e
C. The arylamine (1 equiv) was dissolved in a solution of Et2O,
THF, and CH3CN (7:6:1 v:v, 7 mL per mmol). A solution of
HCl (4.5 M, 9 equiv) was added, and the reaction mixture was
cooled to -5 °C. A solution of NaNO2 (3.4 equiv) in CH3CN
and H2O (2:3 v:v, 2 M) was added dropwise, and the reaction
was stirred for 1.5 h at -5 to 0 °C. The mixture was poured
into a chilled solution of K2CO3 (5 equiv) and Et2NH (5 equiv)
in CH3CN and H2O (2:1 v:v, 10 mL per mmol arylamine). After
stirring for 1.5 h, the mixture was extracted twice with ether.
The combined ether layers were washed twice with brine, dried
(MgSO4), filtered, and concentrated by rotary evaporation. The
crude product was purified by column chromatography on
silica gel or by Chromatotron.
Gen er a l Ma cr ocycliza tion P r oced u r e D. The silyl-
protected macrocycle precursor was dissolved in THF (25 mL
per mmol) and EtOH (10-20 drops). A solution of Bu4NF was
added (1 M in THF, 2.1 equiv) with stirring at room temper-
ature. The reaction was monitored by TLC. Upon completion,
the mixture was diluted with Et2O, washed three times with
water and twice with brine, and dried (MgSO4). After filtration
through a short pad of silica gel and removal of the solvent,
the resulting product was dissolved in a small volume of
pyridine and was used immediately in the next step.
F igu r e 2. Electronic absorption spectra of molecules 2b, 23,
and 24.
random polymerization. The residues were insoluble
black materials that could not be adequately analyzed.
No others transitions that might suggest liquid crystal
behavior were observed, although such behavior might
be induced by preparing derivatives of 2 and 4 with
different substitution patterns or functional groups (i.e.,
R ) long alkoxy or carboalkoxy linkages).8d,23
Con clu sion
In summary, we have demonstrated that the catalyst
Pd[P(o-Tol)3]2 is particularly effective for the construction
of sterically hindered systems such as 6-fold Sonogashira
cross-coupling reactions. In conjunction with this catalyst,
we have developed a method of preparing hexakis-
(phenylbutadiynyl)benzene derivatives such as 4a -c,
which have been unobtainable by conventional routes.
Using this method we were able to prepare 2a ,b, which
are the largest graphdiyne fragments to date. Unfortu-
nately, the synthesis of 3 was elusive, presumably
because 18 represents the upper limit of bulky append-
ages which can be successfully introduced by this tech-
nique. Evidence presented suggests that 2 and 4 will
exhibit a strong third-order NLO response. Derivatives
of 4 with various functional groups might optimize this
response as well as induce liquid crystalline behavior.
We are currently exploring the NLO properties of all
graphdiyne substructures, as well as alternate syntheses
of 3.
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. 1H and 13C NMR spectra were
recorded using a Varian Unity Inova 300 (1H, 299.95 MHz;
13C, 75.43 MHz) spectrometer. Chemical shifts (δ) are ex-
pressed in ppm downfield from tetramethylsilane using the
residual nondeuterated solvent as internal standard (CDCl3
1H, 7.26 ppm; 13C, 77.0 ppm; CD2Cl2 1H, 5.34 ppm; 13C, 54.0
ppm). Coupling constants are expressed in hertz. IR spectra
were recorded using a Nicolet Magna-FTIR 550 spectrometer.
UV-vis spectra were recorded in CH2Cl2 using a Hewlett-
Packard 8453 spectrophotometer. Mass spectra were recorded
using a Kratos MS50 spectrometer (EI, CI, FAB) or a PerSep-
tive Biosystems Voyager-DE STR Biospectrometry Work-
(23) Zhang, D.; Tessier, C. A.; Youngs, W. J . Chem. Mater. 1999,
11, 3050-3057.

Carbon Networks Based on Dehydrobenzoannulenes. 4
J . Org. Chem., Vol. 66, No. 11, 2001 3899
The deprotected precursor was added over 16-20 h via
syringe pump to a suspension of CuCl and Cu(OAc)2‚H2O (20
equiv of each per coupling) in pyridine (250 mL per mmol of
R,ω-polyyne) at 60 °C. Upon completion, the mixture was
concentrated in vacuo and diluted with CH2Cl2. The organic
layer was subsequently washed with 10% HCl solution and
repeatedly with water. The organic layer was dried (MgSO4),
filtered, evaporated, and purified by column chromatography
or preparative TLC.
(67 mg, 84%) as light orange needles: mp 67-69 °C; 1H NMR
(CDCl3) δ 7.41 (d, J ) 8.4 Hz, 2H), 7.34 (d, J ) 8.4 Hz, 2H),
2.46 (s, 1H), 1.30 (s, 9H); 13C NMR (CDCl3) δ 152.95, 132.48,
125.43, 117.77, 75.52, 70.90, 68.23, 67.65, 34.84, 30.98; IR
(KBr) υ 3296, 2964, 2904, 2870, 2212, 1502, 1458 cm-1; MS
(CI pos) m/z (%) 182.1 (M+, 73), 167.1 (100) 139.0 (22); C14H14
(182.26). Anal. Calcd: C 92.26, H 7.74. Found: C 92.12, H 7.78.
Su bu n it 4a . tert-Butyldiyne 6a (76 mg, 0.30 mmol) was
reacted with C6I6 (25 mg, 0.03 mmol) as described in general
procedure B. Column chromatography on silica gel (20%
CH2Cl2 in petroleum ether) followed by recrystallization from
CH2Cl2 gave 4a as yellow needles (15 mg, 42%): mp 174 °C
(dec); 1H NMR (CDCl3) δ 7.53 (d, J ) 8.4 Hz, 12H), 7.35 (d, J
) 8.4 Hz, 12H), 1.32 (s, 54H); 13C NMR (CDCl3) δ 153.12,
132.55, 128.99, 125.47, 118.37, 86.74, 85.17, 76.91, 73.70,
34.96, 31.08; IR (KBr) υ 2954, 2916, 2848, 2206, 1697, 1600,
1462 cm-1; UV/vis (CH2Cl2) λmax (ꢀ) 321 (37 200), 385 (132 900),
412 (116 800) nm; MS (FAB pos) m/z (%) 1159.1 (M+, 100),
926 (98), 866 (55), 766 (49), 690 (43); MS (MALDI-TOF) C90H79
(1159.58) m/z 1160.15.
4-n -Decyliod oben zen e. 4-n-Decylaniline (500 mg, 2.14
mmol) was dissolved in glacial AcOH (35 mL). In a separate
container, NaNO2 (85 mg, 1.23 mmol) was suspended in
chilled, concentrated H2SO4 (1 mL). The NaNO2 solution was
added slowly to the reaction mixture and was allowed to stir
for 2 h. The reaction was poured into a quench solution
consisting of KI (1.55 g, 9.34 mmol) and I2 (320 mg, 1.26 mmol)
in H2O (3 mL), and the resulting mixture was stirred for 2 h.
Crushed ice and a 15% NaOH solution were added until the
mixture was basic to litmus paper. The mixture was extracted
into EtOAc and washed with a 5% NaHSO3 solution, H2O, and
brine. The organics were dried (MgSO4), filtered, and concen-
trated under vacuum. Purification by chromatotron (4 mm
plate, hexanes) gave the desired product (485 mg, 66%) as an
orange oil: 1H NMR (CDCl3) δ 7.59 (d, J ) 8.2 Hz, 2H), 7.16
(d, J ) 8.2 Hz, 2H), 2.55 (t, J ) 7.7 Hz, 2H), 1.65-1.52 (m,
2H), 1.38-1.20 (m, 14H), 0.90 (t, J ) 6.6 Hz, 3H); 13C NMR
(CDCl3) δ 142.47, 137.17, 130.51, 90.49, 35.42, 31.88, 31.28,
29.60, 29.56, 29.45, 29.32, 29.18, 22.68, 14.13; IR (neat) υ 2954,
2924, 2854, 1485, 1466, 1007 cm-1; MS (CI pos) m/z (%) 344.1
Su bu n it 4b. n-Decyldiyne 6b (100 mg, 0.3 mmol) was
reacted with C6I6 (25 mg, 0.03 mmol) as described in general
procedure B. Purification by preparative TLC (10% CH2Cl2 in
hexanes) gave 4b (6.5 mg, 13% yield) as an amorphous yellow
solid: mp 164 °C (dec); 1H NMR (CDCl3) δ 7.50 (d, J ) 8.0 Hz,
12H), 7.14 (d, J ) 8.0 Hz, 12H), 2.61 (t, J ) 7.8 Hz, 12H),
1.65-1.52 (m, 12H), 1.38-1.20 (m, 84H), 0.88 (br t, 18H); 13
C
NMR (CDCl3) δ 145.11, 132.70, 128.96, 128.58, 118.52, 86.76,
85.13, 76.80, 73.72, 36.05, 31.89, 31.14, 29.59, 29.55, 29.46,
29.31, 29.24, 22.67, 14.11; IR (CH2Cl2) υ 2924, 2852, 2204,
1465, 1427 cm-1; UV/vis (CH2Cl2) λmax (ꢀ) 320 (39 600), 386
(115 700), 413 (100 600) nm; MS (MALDI-TOF) C126H150
(1664.54) 1662.11.
(M+, 55), 260 (70), 245 (100), 216.9 (41), 91 (63); C16H25
I
(344.27). Anal. Calcd: C 55.82, H 7.32. Found: C 55.92, H 7.23.
1-t er t -Bu t yl-4-(4-t r im e t h ylsilyl-1,3-b u t a d iyn yl)b e n -
zen e (6a ). 4-tert-Butyliodobenzene (998 mg, 3.84 mmol) was
reacted with trimethylsilylbutadiyne (705 mg, 5.77 mmol) as
described in general procedure A. Purification by column
chromatography on silica gel (hexanes) followed by recrystal-
lization from hexanes gave 6a (928 mg, 95%) as pale yellow
Su bu n it 4c. Methoxydiyne 6c (500 mg, 2.0 mmol) was
reacted to C6I6 (166 mg, 0.2 mmol) as described in general
procedure B. Purification by preparative TLC (50% CH2Cl2 in
hexanes) gave 4c (20 mg, 10%) as an amorphous yellow solid:
mp 207 °C (dec); 1H NMR (CDCl3) δ 7.53 (d, J ) 8.9 Hz, 12H),
6.86 (d, J ) 8.9 Hz, 12H), 3.83 (s, 18H); 13C NMR (CD2Cl2) δ
161.66, 135.09, 129.34, 114.86, 113.42, 87.68, 85.51, 77.22,
73.10, 55.99; IR (CH2Cl2) υ 2960 (methoxy CH), 2924, 2852,
2198, 1602, 1511, 1423, 1295, 1255 (C-O-C asym), 1172 (C-
O-C sym) cm-1; UV/vis (CH2Cl2) λmax (ꢀ) 398 (103 300), 424
(91 800) nm; MS (MALDI-TOF) C72H42O6 (1003.10) m/e 1004.67.
Anal. Calcd: C 86.21, H 4.22. Found: C 86.07, H 4.30.
4-ter t-Bu tyl-2-iod oa n ilin e (10). 4-tert-Butylaniline (2.0 g,
13.4 mmol) was dissolved in CH2Cl2 (200 mL) and MeOH (100
mL). To this were added (BnEt3N)‚ICl2 (5.46 g, 14.0 mmol)
and CaCO3 (2.68 g, 26.8 mmol). The suspension was stirred
at room temperature for 3 h. The reaction mixture was filtered
through a bed of Celite and was concentrated in vacuo to
approximately 1/3 volume. The residual mixture was washed
with a 5% NaHSO3 solution, a saturated NaHCO3 solution,
water, and brine. The organic layer was dried (MgSO4),
filtered, and concentrated to give an orange oil. Purification
by column chromatography (5% EtOAc in hexanes) furnished
10 (3.33 g, 90%) as a viscous red oil: 1H NMR (CDCl3) δ 7.64
(d, J ) 1.8 Hz, 1H), 7.18 (dd, J ) 8.4, 1.8 Hz, 1H), 6.71 (d, J
) 8.4 Hz, 1H), 3.97 (br s, 2H), 1.27 (s, 9H); 13C NMR (CDCl3)
δ 144.24, 143.18, 135.58, 126.49, 114.44, 84.48, 33.78, 31.37;
IR (neat) υ 3460, 3367, 2962, 2904, 2867, 1616, 1498, 1265
cm-1; MS (CI pos) m/z (%) 275 (M+, 52), 260 (100), 133.1 (18);
1
needles: mp 87-89.5 °C; H NMR (CDCl3) δ 7.43 (d, J ) 8.4
Hz, 2H), 7.34 (d, J ) 8.4 Hz 2H), 1.30 (s, 9H) 0.23 (s, 9H); 13
C
NMR (CDCl3) δ 152.81, 132.46, 125.46, 118.22, 90.11, 88.00,
76.59; 73.49, 34.91, 31.06, -0.37; IR (KBr) υ 2958, 2902, 2868,
2206, 2104, 1502, 1461, 1407, 1250, 846 cm-1; MS (CI Pos)
m/z (%) 254.1 (M+, 60), 239.1 (100); C17H22Si (254.44). Anal.
Calcd: C 80.25, H 8.72. Found: C 80.25, H 8.72.
1-n -Decyl-4-(4-t r im et h ylsilyl-1,3-b u t a d iyn yl)b en zen e
(6b). 4-n-Decyliodobenzene (348 mg, 1.01 mmol) was reacted
with trimethylsilylbutadiyne (185 mg, 1.51 mmol) as described
in general procedure A. Purification by chromatotron (2 mm
plate, petroleum ether) gave 6b (342 mg, 99%) as a viscous,
dark orange oil: 1H NMR (CDCl3) δ 7.40 (d, J ) 8.1 Hz, 2H),
7.12 (d, J ) 8.1 Hz, 2H), 2.59 (t, J ) 8.1 Hz, 2H), 1.65-1.52
(m, 2H), 1.38-1.20 (m, 14H), 0.90 (br t, 3H), 0.24 (s, 9H); 13C
NMR (CD2Cl2) δ 145.76, 133.11, 129.19, 118.68, 90.82, 88.28,
77.52, 73.83, 36.47, 32.46, 31.74, 30.15, 30.11, 29.99, 29.88,
29.77, 23.24, 14.43, -0.18; IR (neat) υ 2961, 2919, 2850, 2208,
2108, 1507, 1464, 1253, 847 cm-1; MS (CI pos) m/z (%) 338.2
(M+, 100), 323.2 (65), 244.1 (57), 229 (64), 73 (63); C23H34Si
(338.60).
4-(4-Tr im eth ylsilyl-1,3-bu ta d iyn yl)a n isole (6c). 4-Iodo-
anisole (500 mg, 2.14 mmol) was coupled with trimethyl-
silylbutadiyne (275 mg, 2.25 mmol) as described in general
procedure A. Purification by column chromatography (2%
CH2Cl2 in petroleum ether) gave 6c (426 mg, 87%) as a dark
oil: 1H NMR (CDCl3) δ 7.43 (d, J ) 8.5 Hz, 2H), 6.83 (d, J )
8.5 Hz, 2H), 3.80 (s, 3H), 0.23 (s, 9H); 13C NMR (CD2Cl2) δ
161.24, 134.88, 114.75, 113.48, 90.51, 88.50, 77.46, 73.39,
-0.11; IR (neat) υ 3005, 2960 (methoxy CH), 2898, 2839, 2202,
2102, 1605, 1567, 1510, 1463, 1300, 1252 (C-O-C asym), 1172
(C-O-C sym) cm-1; MS (CI pos) m/z (%) 228.1 (M+, 85), 213
(89), 108.1 (100), 92 (30), 77(19); C14H16OSi (228.36).
C
10H14IN (275.13). Anal. Calcd: C 43.65, H 5.13, N 5.09.
Found: C 43.91, H 5.02, N 5.18.
N,N-Dieth yl-N′-(4-ter t-bu tyl-2-iodoph en yl)tr iazen e (11).
Iodoaniline 10 (3.33 g, 12.1 mmol) was subjected to general
procedure C. Purification by column chromatography on silica
gel (5% CH2Cl2 in petroleum ether) gave 11 (4.01 g, 92%) as
an orange oil: 1H NMR (CDCl3) δ 7.88 (d, J ) 1.8 Hz, 1H),
7.33 (m, 2H), 3.80 (q, J ) 6.9 Hz, 4H), 1.35 (t, J ) 7.0 Hz,
4H), 1.34 (s, 9H); 13C NMR (CDCl3) δ 149.64, 148.00, 135.70,
125.79, 116.82, 96.59, 48.85, 42.12, 34.19, 31.25, 14.57, 11.07;
IR (neat) υ 3066, 2966, 2933, 2904, 2870, 1589, 1540, 1463,
1380, 1340, 1257, 1236, 1207, 1105 cm-1; MS (CI pos) m/z (%)
359 (M+, 50), 287 (40), 259 (100), 132.1 (20), 117.1 (39), 72.1
1-(1,3-Bu t a d iyn yl)-4-ter t-b u t ylb en zen e (7a ). The tri-
methylsilyl protecting group was removed from 6a (150 mg,
0.44 mmol) as described in the first step of general procedure
B. Purification by column chromatography (petroleum ether)
followed by recrystallization (petroleum ether) furnished 7a

3900 J . Org. Chem., Vol. 66, No. 11, 2001
Wan and Haley
(21); C14H22IN3 (359.25). Anal. Calcd: C 46.81, H 6.17, N 11.70.
Found: C 46.51, H 6.02, N 11.48.
400.8 (62), 385.8 (100), 259 (13), 132.1 (12); C14H21N3I2 (485.15).
Anal. Calcd: C 34.66, H 4.36, N 8.66. Found: C 34.77, H 4.16,
N 8.39.
N,N-Dieth yl-N′-[4-ter t-bu tyl-2-(tr iisopr opylsilyleth yn yl)-
p h en yl]tr ia zen e (12). Iodotriazene 11 (705 mg, 1.96 mmol)
was reacted with triisopropylsilylacetylene (0.66 mL, 2.94
mmol) as described in general procedure A. Purification by
column chromatography (5% CH2Cl2 in petroleum ether) gave
12 (756 mg, 93% yield) as an orange oil: 1H NMR (CDCl3) δ
7.46 (d, J ) 2.1 Hz, 1H), 7.35 (d, J ) 8.7 Hz, 1H), 7.18 (dd, J
) 8.7, 2.1 Hz, 1H), 3.78 (q, J ) 6.9 Hz, 4H), 1.31 (s, 9H), 1.26
(br t, 6H triplet), 1.14 (s, 21H); 13C NMR (CDCl3) δ 150.28,
147.37, 130.37, 126.33, 117.76, 116.38, 106.10, 93.09, 49.73,
41.35, 34.25, 31.25, 18.76, 14.32, 11.46, 11.43; IR (neat) υ 2960,
2943, 2866, 2152, 1464, 1387, 1238, 1092 cm-1; MS (CI pos)
m/z (%) 413.3 (M+, 4), 359 (51), 287 (43), 259 (100), 117.1 (39),
72.1 (22); C25H43N3Si (413.71). Anal. Calcd: C 72.58, H 10.48,
N 10.16. Found: C 72.81, H 10.23, N 10.01.
N,N-Dieth yl-N′-[2,6-bis(tr iisopr opylsilyleth yn yl)-4-ter t-
bu t ylp h en yl]t r ia zen e (16). Diiodotriazene 15 (2.0 g, 4.12
mmol) was reacted with triisopropylsilylacetylene (2.77 mL,
12.12 mmol) as described in general procedure A. Purification
by column chromatography (2% EtOAc in petroleum ether)
gave 16 (1.93 g, 75%) as a pale orange solid: mp 89.5-90.5
1
°C; H NMR (CDCl3) δ 7.42 (s, 2H), 3.76 (q, J ) 6.9 Hz, 4H),
1.30 (s, 9H), 1.26 (br t, 6H), 1.10 (s, 42H); 13C NMR (CDCl3) δ
152.95, 146.81, 131.25, 116.37, 105.43, 92.75, 48.51, 40.73,
34.12, 31.13, 18.68, 14.31, 11.34, 11.15; IR (KBr) υ 2943, 2893,
2866, 2146, 1464, 1394, 1238, 1009 cm-1; MS (CI pos) m/z (%)
593.4 (M+, 43), 550.4 (24), 521.3 (57), 484.9 (59), 451.3 (78),
412.9 (60), 384.8 (100), 271.2 (56), 131.1 (56); C36H63N3Si2
(594.08). Anal. Calcd: C 72.78, H 10.69, N 7.07. Found: C
72.51, H 10.46, N 6.95.
4-ter t-Bu t yl-1-iod o-2-[(t r iisop r op ylsilyl)et h yn yl]b en -
zen e (13). Triazene 12 (750 mg, 1.81 mmol) was reacted with
freshly distilled CH3I (8 mL) in a sealed reaction vessel at 120
°C for 24 h. The reaction was cooled, diluted with hexanes,
and filtered through a bed of Celite and silica gel. Removal of
the solvent by rotary evaporation gave 13 (657 mg, 82% yield)
as a dark brown oil in sufficiently pure form: 1H NMR (CDCl3)
δ 7.75 (d, J ) 8.4 Hz, 1H), 7.49 (d, J ) 2.1 Hz, 1H), 7.03 (dd,
J ) 8.4, 2.1 Hz, 1H), 1.30 (s, 9H), 1.19 (s, 21H); 13C NMR
(CDCl3) δ 151.03, 138.29, 130.23, 129.56, 127.13, 108.47, 97.22,
94.37, 34.48, 31.01, 18.75, 11.37; IR (neat) υ 2960, 2943, 2866,
2158, 1461, 1382, 1014 cm-1; MS (CI pos) m/z (%) 440.1 (M+,
14), 397 (100), 369 (14), 355 (14), 327 (16), 259 (13); C21H33ISi
(440.48). Anal. Calcd: C 57.26, H 7.55. Found: C 57.17, H 7.35.
1,3-Bis(t r iisop r op ylsilylet h yn yl)-5-ter t-b u t yl-2-iod o-
ben zen e (17). Triazene 16 (1.90 g, 3.2 mmol) was treated with
CH3I (25 mL) in a sealed reaction vessel at 120 °C for 24 h.
The reaction was cooled, diluted with hexanes, and filtered
through a bed of Celite and silica gel. Purification by column
chromatography (hexanes) gave 17 (1.56 g, 78% yield) as a
pale yellow oil: 1H NMR (CDCl3) δ 7.39 (s, 2H), 1.30 (s, 9H),
1.17 (s, 21H); 13C NMR (CDCl3) δ 150.74, 130.80, 129.84,
108.73, 103.91, 94.67, 34.42, 30.90, 18.74, 11.35; IR (neat) υ
2958, 2943, 2866, 2150, 1464, 1390, 989 cm-1; MS (CI pos) m/z
(%) 620.1 (M+, 72), 577.1 (93), 451.2 (100), 430.9 (50); C32H53
-
ISi2 (620.84). Anal. Calcd: C 61.91, H 8.60. Found: C 62.22,
H 8.55.
1,3-Bis(tr iisop r op ylsilyl)eth yn yl-5-ter t-bu tyl-2-[4-(tr i-
m eth ylsilyl)-1,3-bu ta d iyn yl]ben zen e (9a ). Iodoarene 17
(1.50 g, 2.4 mmol) was reacted with trimethylsilylbutadiyne
(445 mg, 3.65 mmol) as described in general procedure A.
Purification by column chromatography on silica gel (petro-
leum ether) followed by recrystallization from petroleum ether
(slow evaporation) gave 9a (1.34 g, 90%) as orange needles:
mp 121-123 °C; 1H NMR (CDCl3) δ 7.39 (s, 2H), 1.29 (s, 9H),
1.16 (s, 12H), 0.21 (s, 9H); 13C NMR (CDCl3) δ 151.63, 128.96,
127.45, 124.78, 104.64, 95.51, 91.69, 88.61, 81.43, 74.24, 34.75,
30.87, 18.72, 11.36, -0.45; IR (KBr) υ 2960, 2943, 2893, 2866,
2204, 2152, 2102, 1581, 1538, 1464, 1400, 1251, 999 cm-1; MS
(CI pos) m/z (%) 614.2 (M+, 100), 571.2 (28), 529.1 (42), 487.1
(32), 73 (34); C39H62Si3 (615.17).
r,ω-P olyyn e 18a . Triyne 8a (400 mg, 0.92 mmol) was
reacted with C6I6 (75 mg, 0.09 mmol) as described in general
procedure B. Purification by column chromatography (10%
CH2Cl2 in petroleum ether), followed by slow evaporation from
petroleum ether, produced 18a (60 mg, 30%) as yellow
needles: mp 252 °C (dec); 1H NMR (CDCl3) δ 7.46 (d, J ) 8.4
Hz, 6H), 7.44 (d, J ) 2.1 Hz, 6H), 7.23 (dd, J ) 8.4, 2.1 Hz,
6H), 1.29 (s, 54H), 1.09 (s, 126 H); 13C NMR (CDCl3) δ 152.37,
133.14, 129.11 (2C), 126.78, 125.26, 121.76, 104.82, 95.66,
85.43, 85.27, 77.52, 77.27, 34.83, 30.96, 18.71, 11.31; IR
(CH2Cl2) υ 2958, 2943, 2864, 2204, 2156, 1461 cm-1; UV/vis
(CH2Cl2) λmax (ꢀ) 383 (117 100), 415 (93 100) nm; MS (FAB)
m/z (%) 2240.4 (M+, 73), 1881.1 (100); (MALDI-TOF) 2264.72
(M+ + Na), 1913.54 (M+ - 2 × TIPSA); C156H198Si6 (MW
2241.75).
Su bu n it 2a . Precursor 18a (56 mg, 0.025 mmol) was
deprotected and cyclized as described in general procedure D.
Purification by preparative TLC (5% CH2Cl2 in hexanes) gave
2a (6 mg, 20%) as an amorphous yellow solid that was
extremely difficult to redissolve: MS (MALDI-TOF) m/z (%)
1320.8 (M+ + Na), 1298.0 (M+). C102H72 (MW 1297.66).
r,ω-P olyyn e 18b. Triyne 8b (500 mg, 0.96 mmol) was
reacted with C6I6 (80.3 mg, 0.096 mmol) as described in general
procedure B. After workup, the residue was preabsorbed on
silica gel and was purified by flash chromatography. Elution
(petroleum ether) gave the homodimer of 8b; further elution
(2% CH2Cl2 in petroleum ether) gave 18b (50 mg) contami-
nated with partially coupled material: 1H NMR (CDCl3) δ )
7.52 (s, Ar-H of 5-fold material), 7.46-7.41 (m), 7.30-7.25
(m), 7.08-6.99 (m), 1.17-1.09 (4 s); MS (MALDI-TOF) m/z (%)
4-t er t -Bu t yl-2-[(t r iisop r op ylsilyl)e t h yn yl]-1-[4-(t r i-
m eth ylsilyl)-1,3-bu ta d iyn yl]ben zen e (8a ). Iodoarene 13
(600 mg, 3.81 mmol) was reacted with trimethylsilylbutadiyne
(252 mg, 2.06 mmol) as described in general procedure A.
Purification by column chromatography on silica gel (petro-
leum ether) gave 8a (535 mg, 90% yield) as a pale yellow
1
solid: mp 61-63 °C; H NMR (CDCl3) δ 7.46 (d, J ) 1.8 Hz,
1H), 7.40 (d, J ) 8.1 Hz, 1H), 7.28 (dd, J ) 8.1, 1.8 Hz, 1H),
1.31 (s, 9H), 1.19 (s, 21H), 0.23 (s, 9H); 13C NMR (CDCl3) δ
152.27, 132.44, 129.05, 127.20, 125.42, 121.64, 104.99, 95.16,
90.82, 88.26, 77.28, 75.50, 34.80, 30.93, 18.71, 11.34, -0.41;
IR (KBr) υ 2960, 2866, 2204, 2156, 2102, 1464, 1252 cm-1; MS
(CI pos) m/z (%) 434.2 (M+, 23), 397 (100), 349.1 (32), 307.1
(27), 287 (25), 259 (59) 229 (18), 117.1 (23), 83.9 (25); C28H42Si2
(434.80).
4-ter t-Bu tyl-2,6-d iiod oa n ilin e (14). 4-tert-Butylaniline
(2.0 g, 13.4 mmol) was dissolved in CH2Cl2 (200 mL) and
MeOH (100 mL). To this were added (BnEt3N)‚ICl2 (10.9 g,
28.0 mmol) and CaCO3 (5.4 g, 54 mmol). The suspension was
stirred at 40 °C overnight. The reaction mixture was filtered
through a bed of Celite and was concentrated in vacuo to
approximately 1/3 volume. The residual mixture was washed
with a 5% NaHSO3 solution, a saturated NaHCO3 solution,
water, and brine. The organic layer was dried (MgSO4),
filtered, and concentrated to give an orange oil. Purification
by column chromatography on silica gel (5% EtOAc in petro-
leum ether) first gave monoiodoaniline 10 (1.22 g, 28%), then
diiodoaniline 14 (4.62 g, 72%) as a viscous red oil: 1H NMR
(CDCl3) δ 7.62 (s, 2H), 4.47 (br s, 2H), 1.24 (s, 9H); 13C NMR
(CDCl3) δ 144.52, 143.66, 136.44, 81.74, 33.66, 31.28; IR (neat)
υ 3464, 3363, 2955, 2867, 1613, 1457 cm-1; MS (CI pos) m/z
(%) 400.8 (M+, 67), 385.8 (100), 259 (10), 132.1 (12); C10H13NI2
(401.03).
N ,N -D ie t h y l-N ′-(2,6-d iio d o -4-t er t -b u t y lp h e n y l)t r i-
a zen e (15). 4-tert-Butyl-2,6-diiodoaniline 14 (4.49 g, 11.2
mmol) was subjected to general procedure C. Purification by
chromatography over silica gel (5% EtOAc in hexanes) followed
by slow evaporation gave 15 (4.78 g, 88%) as a light orange
semisolid: 1H NMR (CDCl3) δ 7.81 (s, 2H), 3.79 (q, J ) 6.9
Hz, 4H), 1.37 (br t, 6H), 1.28 (s, 9H); 13C NMR (CDCl3) δ
151.15, 149.82, 136.74, 90.94, 49.10, 41.69, 34.08, 31.17, 14.92,
11.35; IR (neat) υ 2964, 2933, 2906, 2870, 1576, 1514, 1465,
1255, 1203, 1107 cm-1; MS (CI pos) m/z (%) 484.9 (M+, 10),

Carbon Networks Based on Dehydrobenzoannulenes. 4
J . Org. Chem., Vol. 66, No. 11, 2001 3901
2703.6 (M+ - i-Pr), 2602.4 (M+ - Si-i-Pr3), 2215.8 (5-fold
product with H, - 2(i-Pr)). C192H270Si6 (2746.71).
Camille and Henry Dreyfus Foundation (Teacher-
Scholar Award 1998-2003 to M.M.H.), and the U.S.
Department of Education (GAANN Fellowship to
W.B.W.). We thank Dr. Timothy Weakley for assistance
in obtaining the X-ray crystal structure of 4a and Prof.
Brian Matthews for use of the MALDI-TOF mass
spectrometer.
Su bu n it 2b. An impure mixture of 18b (50 mg) was
deprotected and cyclized as described in general procedure D.
Purification by preparative TLC (5% CH2Cl2 in hexanes) gave
2b (11 mg, 6% yield based on C6I6) as an amorphous yellow
solid: 1H NMR (CD2Cl2) δ 7.80 (d, J ) 8.1 Hz, 12H), 7.58 (d,
J ) 1.2 Hz, 12H), 7.36 (dd, J ) 8.1, 1.2 Hz, 12H), 2.71 (t, J )
7.8 Hz, 12H), 1.65-1.58 (m, 12H), 1.38-1.20 (m, 84H), 0.88
(br t, 18H); IR (CH2Cl2) υ 2923, 2850, 2194, 1592, 1464, 1420
cm-1; UV/vis (CH2Cl2) λmax (ꢀ) 411 (118 200), 423 (95 000), 442
(124 500) nm; MS (MALDI-TOF) C138H144 (1802.62): m/z
1802.7 (M+).
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra for compounds 2b, 4a -c, 6b,c, 8a , 9a 14, and 18a ,b
described in the Experimental Section; low-grade X-ray crystal
structure of 4a . This information is available free of charge
via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. This research was supported by
the National Science Foundation (CHE-9704171), the
J O010183N