An efficient synthesis of liquid crystalline gigantocycles combining banana-shaped and rod-like mesogenic units

Article abstract of DOI:10.1002/1521-3765(20021115)8:22<5094::AID-CHEM5094>3.0.CO;2-6

The synthesis of monodisperse gigantocycles with 63, 87, and 147 ring atoms on the gram scale is described. These molecules were assembled from terphenylene derivatives and long, flexible chains which were mainly aliphatic, with terminal alkyne groups. The latter allowed for ring formation through oxidative alkyne dimerization in high yield (80-87%). The combination of a rod-like and a banana-shaped mesogen connected by flexible chains within the backbone of a ring gives rise to nematic and smectic mesophases.

Full text of DOI:10.1002/1521-3765(20021115)8:22<5094::AID-CHEM5094>3.0.CO;2-6

FULL PAPER
An Efficient Synthesis of Liquid Crystalline Gigantocycles Combining
Banana-Shaped and Rod-Like Mesogenic Units
Adelheid Godt,*[a] Stefan Duda,[a] ÷mer ‹nsal,[a] J¸rgen Thiel,[a] Alice H‰rter,[a]
Mark Roos,[a] Carsten Tschierske,[b] and Siegmar Diele[c]
Abstract: The synthesis of monodisperse gigantocycles with 63, 87, and 147 ring
atoms on the gram scale is described. These molecules were assembled from
terphenylene derivatives and long, flexible chains which were mainly aliphatic, with
terminal alkyne groups. The latter allowed for ring formation through oxidative
alkyne dimerization in high yield (80 87%). The combination of a rod-like and a
banana-shaped mesogen connected by flexible chains within the backbone of a ring
gives rise to nematic and smectic mesophases.
Keywords:
liquid crystals ¥ macrocycles
Glaser coupling
¥
phenyl)butadiyne. These units are linked through chains
which are long, flexible, and mainly aliphatic with a different
length in each of the three cycles 9a, b, and 17. The tail-to-tail
attachment of rod-like mesogens through flexible chains
Introduction
Cyclic molecules play an important role as components of
supramolecular systems such as rotaxanes and catenanes,[1]
and as hosts for ions and molecules in host guest com-
plexes.[2] They are also examples of materials that undergo
self-organisation and thus exhibit mesophases.[3 Further-
more, huge cycles are of interest because they are macro-
molecules with a special topology.[8
allowing for easy variation of ring size and addition of
different functionalities, and thus having a broad sphere of
application are therefore highly desirable. Herein we describe
a versatile synthesis for functionalized, monodisperse, huge
cyclic molecules on the gram scale. Our synthetic strategy is
exemplified by the synthesis of the gigantocycles 9 and 17
containing up to 147 ring atoms.
7]
within a ring can result in mesomorphic cyclic compounds.[4
Indeed, the cycles 9a, b, and 17 were found to be thermotropic
liquid crystalline compounds showing nematic and smectic
phases. The cycles 9 and 17 are unique in so far as they
combine mesogenic units of very different shape, that is a
banana-shaped[11] and a rod-like mesogen.
7]
10]
Efficient syntheses
Results and Discussion
Synthesis
Characteristic features of the cycles 9 and 17 are a banana-
shaped moiety carrying inward and outward oriented func-
tionalities. These are a 4-hydroxybenzoate substituted with
two tolane moieties, and the rod-like unit 1,4-bis(4-ethynyl-
The main criterions for the design of the synthesis were the
feasibility of preparing the building blocks on a multi-gram
scale and a cyclization reaction giving high yields. The latter is
imperative for a reaction sequence of broader relevance.
These considerations resulted in the design of the ring
precursors 8a, b, and 16 and the choice of the oxidative
alkyne dimerization as the cyclization reaction.
[a] Dr. A. Godt, S. Duda, Dr. ÷. ‹nsal, J. Thiel, A. H‰rter, M. Roos
Max-Planck-Institut f¸r Polymerforschung
Ackermannweg10, 55128 Mainz (Germany)
E-mail: godt@mpip-mainz.mpg.de
Synthesis of the ring precursors 8a, b and 16: The ring
precursors 8a, b and 16 were assembled from terphenylene
6
2). For the preparation of the chains 5 and 14 the long w-
alkynols 3 and 11 were required as the key building blocks.
Convenient starting compounds for such alkynols are either
w-bromoalkanols or 1-bromoalkanes.
[b] Prof. Dr. C. Tschierske
Martin-Luther-Universit‰t Halle-Wittenberg
Institut f¸r Organische Chemie
Kurt-Mothes-Strasse 2, 06120 Halle (Germany)
[12] and the long, flexible chains 5a, b and 14 (Schemes 1 and
[c] Dr. S. Diele
Martin-Luther-Universit‰t Halle-Wittenberg
Institut f¸r Physikalische Chemie
M¸hlpforte 1, 06108 Halle (Germany)
For the shortest alkynol 11 we used 11-bromoundecanol
which was silylated to give 10 and subsequently converted into
Supporting information for this article is available on the WWW under
http://www.chemeurj.org/ or from the author.
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5094 5106
alkynol 3. This alkyne isomer-
ization reaction (Zipper reac-
tion) yielded the alkynol 3 and
about 30% of alkanes[19] carry-
ing neither a hydroxyl nor an
alkyne functionality. Most of
these alkanes were removed
by column chromatography
and subsequent recrystalliza-
tion. When NaH/diaminopro-
pane[20, 21] was used as the iso-
merization agent, about 50% of
non-functionalized
alkanes
were formed besides the in-
tended product 3. Other condi-
tions such as KH/diaminopro-
pane[22] and NaNH2/diamino-
propane[23] were tested only
once and gave incomplete con-
versions. Experiments to im-
prove the workup procedure
revealed the sensitivity of the
product towards transforma-
tion into an enyne with charac-
1
teristic signals in the H NMR
spectrum at d ˆ 5.08, 4.63, and
1.77.[24] Although this by-prod-
uct was formed only in small
amounts (1 3%, estimated by
1H NMR spectroscopy), we
were not successful in removing
it by chromatography and re-
crystallization from hexane.
This structural impurity was
retained in the products during
the following synthetic steps. To
avoid the formation of this
enyne, careful control of the
temperature during aqueous
workup turned out to be the
crucial factor.
Scheme 1. a) 1,3-Dimethyl-1,3-diazacyclohexan-2-on, THF; b) TsOH, MeOH, THF; c) Li, 1,3-diaminopropane,
KOtBu; d) [Pd(PPh3)2Cl2], CuI, piperidine; e) 1) [Pd(PPh3)2Cl2], CuI, piperidine, 2) HCl, MeOH, diethyl ether;
f) diisopropyl azodicarboxylate, PPh3, THF; g) nBu4NF, THF; h) CuCl, CuCl2, pyridine.
Pd/Cu-catalyzed coupling of
the alkynol 3 or the silylated
alkynol 11 with 1-iodo-4-(trii-
sopropylsilylethynyl)benzene
O-silylated 12-tridecynol 11. For the substitution, we em-
ployed ethynyllithium in 1,3-dimethyl-1,3-diazacyclohexan-2-
on (N,N'-dimethyl-N,N'-propylene urea, DMPU),[13, 14] there-
by avoiding toxic HMPA which is still most often used as a co-
solvent.[15, 16] The rather low yield (57%) of 11 is attributed to
the formation of silylated tetracos-12-yn-1,24-diol which
resulted from disubstitution of the ethyne with the bromoal-
kane.[17]
The corresponding longer alkynol, pentacos-24-ynol (3),
was obtained from 1-bromodocosane. Reaction with the
lithium salt of THP-protected propargyl alcohol gave com-
pound 1 which was deprotected to give pentacos-2-ynol (2).
Isomerization of 2 in a suspension of the lithium salt of 1,3-
diaminopropane and KOtBu in 1,3-diaminopropane[18] gave
(19a) and, in the case of 11, subsequent O-desilylation, gave
the long chains 4a, b with a protected, terminal arylalkyne
moiety. Finally derivatization of 4a, b with 4-iodophenol
using the Mitsunobu reaction[25] gave the chains 5a, b.
For the synthesis of the longest chain 14 we used the
synthetic transformations of the preparation of 5b starting
from 3 in a repeated sequence (Scheme 2). Intermediate 4b
was attached to 2,6-dimethyl-4-iodophenol. The iodo func-
tionality of product 12 was used to extend the molecule with
alkynol 3. Subsequent Mitsunobu reaction with 4-iodophenol
gave 14. 2,6-Dimethyl-4-iodophenol was chosen instead of
4-iodophenol as the linkbetween the two alkynols in order to
increase the solubility of the final long chain. Additionally, the
signal of the aromatic protons of the dimethylphenol moiety
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Scheme 2. a) Diisopropyl azodicarboxylate, PPh3, THF; b) [Pd(PPh3)2Cl2], CuI, piperidine; c) nBu4NF, THF; d) CuCl, CuCl2, pyridine, 1,2-dichloroben-
zene.
1
appears well separated from others in the H NMR spectra
and hence offers the advantage of having an additional NMR
probe within the molecule. We expect to be able to extend the
reaction sequence for even larger chains by repeating alter-
nately the two synthetic steps, Mitsunobu and alkynyl-aryl
coupling. Alternatively, this should be possible using a
divergent-convergent approach comprising of desilylation of
the compounds with terminal hydroxyl functionalities, such as
4b and 13, and subsequent coupling of the products with
compounds carrying an iodo substituent and a silylated
terminal alkyne moiety, such as 12 and 14.
the cycle precursors were obtained in one batch, for example,
8
9 g of 8.
Originally, the synthesis was pursued using trimethylsilyl
(TMS) instead of triisopropylsilyl (TIPS) as the protecting
group for the terminal alkyne moiety of 4, 5, and 7. However,
with this much cheaper protecting group two distinct side
reactions were noted. One side reaction occurred during the
synthesis of compound 19, which is the coupling partner of the
alkynols 3 and 11 in the reaction to obtain 4. Compound 19
was prepared in a two-step process from 1-bromo-4-iodoben-
zene (Scheme 3): First, coupling of 1-bromo-4-iodobenzene
with trialkylsilylethyne gave 18.[26] Secondly, exchange of the
bromo substituent of 18 for an iodo substituent by halogen
metal exchange gave 19. The coupling of 1-bromo-4-iodoben-
zene with trimethylsilylethyne gave 18b contaminated with
The long chains 5 and 14 were coupled with the terpheny-
lene 6 in the presence of Pd/Cu salts to obtain, after
desilylation, the ring precursors 8a, b and 16. Despite the
great number of synthetic transformations, several grams of
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Gigantocycles
5094 5106
assume that piperidine partially deprotonates the phenolic
compounds 6 and 7. The resulting phenolates desilylate the
compound 7(TMS) and the released terminal alkyne moiety
couples with the iodo component 5(TMS) giving 22. Careful
chromatography permitted removal of this by-product, un-
fortunately at the expense of a substantial amount of product.
Although the desilylation that causes the side products is a
rather slow process and can be reduced by short reaction
times (90 min) to an extent that the by-product is not detected
anymore by 1H NMR spectroscopy or FD-MS, the possibility
of desilylation and subsequent chain extension renders this
step unreliable. Through the use of the more stable alkyne
protecting groups TES or TIPS, the ™long chain extension∫
could be completely avoided.
Scheme 3. a) [Pd(PPh3)2Cl2], CuI, piperidine (for 18a) or diethylamine
(for 18b, c); b) 1) BuLi, THF, 2) 1,2-diodoethane or iodine.
4-bromo-4'-(trimethylsilylethynyl)tolane (20b) in amounts of
usually 0.5 3 mol%.[27a] Because 20b has the same reactive
groups as 18b, all compounds derived from 18b, such as 19b,
or 4(TMS) (4 carrying TMS instead of TIPS groups),
contained small amounts of molecules which are extended
by an ethynylenephenylene moiety, as proven by NMR
spectroscopy and field desorption mass spectrometry (FD-
MS).[27b] Exchanging the base and solvent piperidine for
triethylamine in the preparation of 18b did not improve the
situation. All solvents had been dried prior to use. The
amount of this kind of side reaction could be significantly
reduced when triethylsilyl (TES) was used instead of TMS.
Only occasionally traces of chain-extended products (<1%
according to 1H NMR and FD-MS spectra) were found. With
TIPS as the protecting group the by-product 20a was avoided.
Cyclization: The cyclization is most often the bottleneckin
the synthesis of cyclic molecules and, therefore, calls for
special attention. The oxidative alkyne dimerization (Glaser
coupling)[29] can be a very efficient reaction for the formation
of cyclic molecules. Most often it is employed in the formation
of rather stiff rings.[30] However, a few remarkable results have
been reported on very large cycles,[31, 32] also named giganto-
cycles,[7, 31] that are conformationally flexible. Several different
reaction conditions for cyclization through alkyne dimeriza-
37]
tion can be found in the literature.[29 However, very little
[36, 37]
systematic or comparative workhas been done.
A
comparison of the reaction conditions described for different
‡
kinds of alkynes made us assume that Cu /Cu2‡ in pyridine is
‡
well suited for arylethynes, while Cu in the presence of
TMEDA and oxygen is well
suited for aliphatic alkynes.
The same conclusion is suggest-
ed by the kinetic studies of
Hay[36] and Bohlmann.[37]
A
comparison of the cyclization
of 23 and 25 in pyridine with
‡
Cu /Cu2‡ as catalyst and
agent[35] (Scheme 4) showed a
dramatic influence of the sub-
stituent at the terminal ethyne
groups.
A solution of com-
pound 23 or 25 dissolved in
pyridine was slowly added to a
suspension of the copper salts
in pyridine. After complete ad-
The second side reaction when using TMS as the protecting
group for the terminal alkyne moiety occurred upon attach-
ment of the chains 5(TMS) to terphenylene 6. This gave
compound 22 with chains approximately twice as long as the
intended product 7. The presence of 22 and of corresponding
compounds derived from 22 upon further transformations
according to Scheme 1 was proven through FD-MS spectra
dition the reaction mixture was stirred for 1 4 d. In the case
of 23, which has two aryl substituted terminal ethyne groups,
the cyclic monomer 24 was formed almost exclusively as can
be deduced from the size-exclusion chromatogram (Fig-
ure 1a). Cyclic compounds have a smaller hydrodynamic
volume than the corresponding ring precursors. Therefore, the
elution time of the cyclic compound is longer than that of the
corresponding acyclic starting material. Cyclic and non-cyclic
oligomers are expected at shorter elution times due to their
larger hydrodynamic volume. The reaction of 23 was quanti-
‡
which show in addition to a dominant signal of the [M] signal
‡
of 7b(TMS), 8b and 9b, a signal of low intensity at [M‡539] .
Corresponding 1H NMR spectra reveal an additional signal at
6.84 ppm which is assigned to the two protons ortho to the
oxygen atom of the phenol ring of the chain-extending moiety.
From this signal×s intensity, the amount of the by-product was
estimated to be 3 6 mol%. For the formation of 22 we
1
tative. The H NMR spectrum shows no signal for an alkyne
proton. However, applying the same conditions to the
reaction of 25–which has two alkyl substituted terminal
ethyne groups–gave mostly oligomers and polymers (Fig-
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A. Godt et al.
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Figure 2. Representative size exclusion chromatograms of the starting
materials 8a (a) and 16 (b) (
and the purified products 9a (a) and 17 (b) (
), the crude product of cyclization (––),
* * *
), respectively.
cycles 9a, b and 17 consisting of 63, 87, or 147 ring atoms were
isolated by usual column chromatography in 80 87% yield as
monodisperse compounds in amounts of 0.8 2.6 g in one
batch. They are very soluble in THF, CH2Cl2, and CHCl3.
Scheme 4. a) CuCl, CuCl2, pyridine.
Thermal characterization of the cyclic molecules 9 and 17 and
of structurally related compounds: The cycles 9a, b and 17
and structurally related compounds were investigated using
polarizing microscopy and differential scanning calorimetry
(DSC). Microscopy of compound 9b revealed that in the first
heating scan 9b undergoes a crystal crystal transition at
143 1458C. At 1518C it melts into a birefringent fluid phase
with a schlieren texture, as typical for nematic phases (Fig-
ure 3). The transition from the nematic phase to the isotropic
Figure 1. Size exclusion chromatograms of the starting materials 23 (a) or
25 (b) (
) and the crude products of cyclization (––). * denotes the
signal arising from 26.
ure 1b) besides some cyclic monomer 26. A substantial part of
the material was insoluble, probably due to its high molecular
weight. On top of this, the reaction was incomplete as shown
by 1H NMR spectroscopy. The spectra show the characteristic
À ꢀ À
signals of the CH2 C C H moiety, a triplet at 1.93 ppm and a
doublet of a triplets at 2.18 ppm. From this comparative study
it is concluded that under the chosen conditions aryl
substituted alkynes react faster than alkyl subsituted ones.
Due to a fast reaction, the concentration of the aryl alkyne 23
is always kept below the critical concentration for intermo-
lecular reactions. The alkyl alkyne 25, however, accumulates
over the course of the addition due to a comparatively slow
reaction, finally allowing for competing intermolecular reac-
tions.
The efficient cyclization of 23 was very promising for the
preparation of our cyclic target molecules 9a, b and 17.
Indeed, slow addition of the ring precursors 8a, b and 16 to a
suspension of CuCl and CuCl2 in pyridine gave predominantly
the cyclic monomers 9a, b and 17, respectively. The success of
this procedure can be clearly seen from the size-exclusion
chromatograms of the crude products (Figure 2). The giganto-
Figure 3. Optical photomicrograph (crossed polarizers) of the texture of
macrocycle 9b at 1508C.
liquid takes place at 1618C. This phase transition is com-
pletely reversible crystallization can be supercooled and
sets in at 1158C. Second and further heating scans revealed
a crystal-crystal transition at 132 1348C and a crystal-
nematic transition at 1428C. The DSC traces (Figure 4) are
in agreement with these observations. Remarkably, the
enthalpy of the nematic-isotropic transition is very small
(0.2 kJmolÀ1).
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Gigantocycles
5094 5106
mesophase is optically biaxial. It can only be observed in the
cooling cycle, thus being a monotropic mesophase occurring
below the melting point (818C). The other two mesophases
are enantiotropic.
Macrocycle 17 was investigated additionally by means of
X-ray diffraction. The nematic phase is characterised by two
diffuse scatterings, one in the wide-angle region and the other
in the small-angle region, as typical for nematic phases. In the
SmA phase a sharp reflection corresponding to a layer
thickness of d ˆ 7.4 nm (Tˆ 958C) is observed. The d value
increases slightly (up to 7.5 nm at Tˆ 798C) with decreasing
temperature. The molecular length of L ˆ 8.3 nm (measured
at CPK models in the most stretched form) is in good
agreement with the layer thickness d if the fluid state of the
alkyl chains is taken into account. Assuming a maximal
segregation of the aromatic and aliphatic building blocks in
this smectic phase, the arrangement shown in Figure 7 is
proposed. The banana-shaped units and the rod-like units lay
side by side forming aromatic-rich layers separated by layers
of the aliphatic parts of the macrocycles. The 4-ethynyl-2,6-
dimethylphenoxy units, which interrupt the aliphatic parts of
the macrocycle 17 are concentrated at the interfaces between
neighboring layers. It is possible that these units form distinct
sublayers that may additionally stabilise the smectic phase of
17.
Figure 4. DSC of macrocycle 9b with a scan rate of 10 KminÀ1: a) first
heating, b) cooling, c) second heating.
In contrast to 9b, the smaller cycle 9a has a very high
melting point (2018C) and shows only a monotropic nematic
phase with a significantly lower clearing temperature (1338C).
Surprisingly, the extension of the flexible aliphatic ring
segments of 9 enhances the stability of the nematic phase
(compare compounds 9a and b). The stability of nematic
phases is usually reduced or the nematic phase is replaced by
smectic phases with increasing length of terminal aliphatic
chains.[38]
The optical biaxiality of the low temperature mesophase
can result from a reduction of the rotational disorder of the
banana-shaped units around their long axes which would lead
to a biaxial SmA-phase (SmAb)[39] or, alternatively, from a
tilting of the banana-shaped and the rod-like units with
respect to the layer normal (SmC).[40] Moreover, both can
happen simultaneously with the additional possibility of a
polar order of the banana-shaped units, leading to polar
smectic phases (B2-type banana phases).[41] However, the
rapid crystallization of this material and the failure to get
sufficiently well oriented samples by alignment in a magnetic
field inhibited a more detailed investigation of this meso-
phase. Nevertheless, the textural features of this biaxial
mesophase are not typical for B2 phases or SmAb phases,
but more related to those of conventional SmC phases in
which the calamitic cores adapt an in average uniformly tilted
arrangement within the layers.
The largest cycle 17 exhibits a richer polymorphism than
the macrocycles 9 (Figures 5 and 6). On slow cooling from the
isotropic liquid state a nematic phase occurs at 1138C (DH ˆ
4.1 kJmolÀ1; Figure 6a, b), followed by a phase transition at
All three macrocyles 9a, b and 17 contain two shape-
persistent and therefore mesogenic units as part of the ring
backbone: a rod-like and an angular or so called banana-
shaped[11] moiety. At least one of these units must be essential
for the mesomorphic behaviour because the corresponding
hydrogenated (more flexible) macrocycle 28 is a compara-
tively low-melting (Tm ˆ 1078C) non-mesomorphic com-
pound. To get an idea which of these moieties is essential
for mesophase formation, we studied the thermal behaviour
of the non-cyclic compounds 27a, b as representatives
incorporating the rod-like moiety and that of the non-cyclic
compounds 7c, 8a, b and 16 as representatives containing a
banana-shaped moiety. None of these compounds exhibit a
liquid crystalline phase. Because the isotropization temper-
ature of the cycle 9b (TNÀI ˆ 1618C) is higher than the melting
points of all non-cyclic compounds 27a (Tm ˆ 1458C), 27b
(Tm ˆ 1258C), 7c (Tm ˆ 1138C), 8a (Tm ˆ 1328C), 8b (Tm ˆ
Figure 5. DSC of macrocycle 17 with a scan rate of 10 KminÀ1: a) first
heating, b) cooling, c) second heating.
998C (DH ˆ 3.4 kJmolÀ1). The latter phase transition is
characterized by the occurrence of a fan-like texture (Fig-
ure 6c, d), which can be aligned homeotropically by shearing.
These textural features indicate a smectic A-Phase (SmA) in
which the molecules are organized in layers and the meso-
genic units are aligned in average perpendicular to the smectic
layer planes. On further cooling, at 818C (not detected with
DSC), the fans become broken and birefringence occurs in the
homeotropically aligned regions (Figure 6e, f) before the
compound crystallizes at slightly lower temperatures. The
birefringence of this low-temperature phase indicates that this
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Figure 6. Optical photomicrographs (crossed polarizers) of the textures of macrocycle 17: (a, b) nematic phase at 1018C; (c, d) SmA-phase at 908C;
(e, f) optically biaxial smectic phase (most probably SmC) at 818C.
1208C) including the ring precursor 16 (Tm ˆ 1008C) and no
mesophase could be detected for any of these non-cyclic
compounds, the mesophases of the cycle 9b must be induced
or significantly stabilised by the macrocyclic molecular
structure. Accordingly, it is assumed that for the other cyclic
compounds 9a and 17 the cyclic molecular structure is
essential for the formation of the liquid crystalline phases,
too. The appearance of mesophases for the macrocycles but
not for the non-cyclic model compounds is probably largely
due to the reduced conformational flexibility of the rings in
comparison to related open-chain compounds. Furthermore,
the reduced difference in entropy between the isotropic and
the LC state when comparing cyclic with non-cyclic com-
pounds should additionally favor the formation of the liquid
crystalline phases.[7b] With the investigated macrocycles nem-
atic phases are predominant, even for macrocycles with very
long aliphatic segments. Obviously the different shapes of the
two mesogenic segments disturb the organisation of these
units into distinct sublayers and thus favor the nematic phase.
The macrocycle 24, incorporating as a banana-shaped unit
Figure 7. Proposed arrangement of macrocycle 17 in the SmA phase.
the significantly smaller bisphenol A, directly melts into an
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Gigantocycles
5094 5106
The unique combination of a banana-shaped and a rod-like
moiety within a ring gives rise to unexpectedly stable nematic
and smectic liquid crystalline phases. The cyclic molecular
structure thereby seems to be essential for the formation of
the liquid crystalline phases of the molecules under discus-
sion. The covalent fixation of rigid segments with different
shapes, which are highly incompatible with each other and
therefore would not mix as individual molecules, could in the
future lead to novel non-conventional mesophases. Addition-
ally, the reported gigantocycles open the way to the prepa-
ration of liquid crystalline catenanes, a new class of supra-
molecular mesomorphic compounds.[42]
Experimental Section
General methods: All reactions were carried out under an inert atmos-
phere in dried Schlenkflasks. In the case of CC-coupling reactions, the
solutions were degassed through several freeze-pump-thaw cycles prior to
the addition of the catalysts. THF was dried over sodium/benzophenone
and piperidine over CaH2. [Pd(PPh3)2Cl2] was synthesized according to the
literature,[43] however with 2.1 times the amount of methanol. For flash
chromatography, silica gel was used. TLC was carried out on silica gel-
coated aluminium foil (Merck60F 254). The petroleum ether used had a
boiling range of 30 408C. The NMR spectra were recorded on a 300 MHz
instrument at room temperature in CDCl3 as solvent and internal standard.
The assignment of the 13C NMR signals is in accordance with Dept-135
ꢀ
measurements. The only exception is the signal of C CH. This signal does
not appear in the DEPT spectrum, in common with our observations
[44]
ꢀ
ꢀ
of a variety of compounds of the type ArC CH and AlkC CH. The
subscripts a, b, g, d, and e refer to the aromatic rings. The hydroxybenzoate
moiety is named a. The benzene unit closest to the hydroxybenzoate
moiety is named b, the benzene unit connected with Arb by only one ethyne
moiety is named g, the benzene unit connected with Arg by the alkane
chain is named d, and the residual benzene unit is named e. For the
numbering of the positions, the ethyl 4-hydroxybenzoate is considered
as the substituted parent compound. Accordingly, the aromatic rings
of the precursors 4, 5, 12 14 are named and numbered as if these chains
were already attached to the core unit, ethyl 4-hydroxybenzoate. If not
otherwise mentioned, melting points were determined in open capillaries
and are not corrected. The temperatures for crystalline crystalline,
crystalline liquid crystalline, and liquid crystalline isotropic melt tran-
sitions were read at the maximum or minimum of the endothermic or
exothermic peaks of the DSC traces. Terphenylene 6[12] was obtained as
described in the literature.
isotropic liquid at 858C which rapidly crystallizes on cooling.
Only upon very rapid cooling from the isotropic liquid state a
rather fluid birefringent mesophase occurs at 438C, which
immediately crystallizes. The very rapid crystallization did not
allow for deciding unambiguously whether this is a true liquid
crystalline or a disordered crystalline phase and prevents any
further investigation of this phase. In the case of compound
24, the mesophase stabilization provided by macrocyclization
is obviously not sufficient to give rise to a stable liquid
crystalline phase. Hence, the appropriate choice of the
anisometric segments is also of great importance for the
successful design of liquid crystalline macrocycles.
Pentacos-2-yn-1-ol (2): nBuLi (1.6m, 102 mL, 163 mmol) in hexane was
added dropwise (30 min) to a solution of 3-tetrahydropyranyloxyprop-1-
yne (24.0 g, 171 mmol) in THF (230 mL) at À758C (bath temp). After
stirring the reaction mixture for 0.5 h at À738C, DMPU (100 mL) was
added dropwise (20 min), followed by the addition of solid, degassed
1-bromodocosane (50.10 g, 128.3 mmol). The cooling bath was removed
and the reaction mixture was stirred 17.5 h at room temperature. The
resulting suspension was cooled (ice bath) and quenched with water. The
aqueous phase was extracted with diethyl ether. The combined organic
phases were washed with 2n HCl, water and finally with brine, dried
(MgSO4), and concentrated in vacuo. The residue was dissolved in 1,4-
dioxane (400 mL) and methanol (200 mL), and toluenesulfonic acid
monohydrate (2.0 g, 11 mmol) was added. Slowly, a precipitate formed.
After stirring the reaction mixture for 4.5 h at room temperature, NaOH
(2n, 50 mL), and water (500 mL) were added, the precipitate was filtered
off using a B¸chner glass funnel, washed with water and methanol, and
dried (P4O10, 0.01 mbar) to give 2 (43.1 g, 92%). Recrystallization from
ethanol (300 mL) gave 2 (40.3 g, 86%) as a beige colored solid.[45] M.p.
77.0 77.98C; 1H NMR: d ˆ 4.24 (t, 5J ˆ 2.2 Hz, 2H, H-1), 2.19 (tt, 5J ˆ
Conclusion
We have developed an efficient synthesis for monodisperse
cyclic compounds with 63, 78, and 147 ring atoms. The final
key step is the cyclization through oxidative dimerization of
aryl ethyne groups. Although the gigantocycles 9a, b and 17
show some rather special structural features, the reported
synthetic strategy of these compounds gives a useful guideline
for the preparation of gigantocycles with variations in ring
size, building blocks and functional groups.
3
2.2 Hz, J ˆ 7.0 Hz, 2H, H-4), 1.56 (brs, 1H, OH), 1.49 (m, 2H, H-5), 1.4
13
ꢀ
1.2 (m, 38H, CH2), 0.87 (t-shaped, 3H); C NMR: d ˆ 86.7, 78.3 (C C),
51.4 (CH2OH), 31.9 (CH2), 29.7 28.6 (7 signals, CH2), 22.7, 18.7 (CH2), 14.1
Chem. Eur. J. 2002, 8, No. 22
¹ 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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5101

A. Godt et al.
FULL PAPER
(CH3); elemental analysis calcd (%) for C25H48O (364.658): C 82.34, H
13.27; found: C 82.20, H 13.37.
ꢀ
6.6 Hz, 2H, CH2OH), 2.38 (t, J ˆ 7.0 Hz, 2H, CH2C C), 1.55 (m, 4H,
ꢀ
CH2CH2OH, CH2CH2C C), 1.5 1.2 (m, 38H, CH2), 1.10 (apparents, 21H,
Pentacos-24-yn-1-ol (3):[18] A mixture of lithium (2.90 g, 418 mmol) and 1,3-
diaminopropane (200 mL; distilled from CaH2) was heated to 708C until
the blue color had disappeared (ca. 1 h). The reaction mixture was cooled
to room temperature, KOtBu (27.30 g, 243 mmol), and 30 min later solid 2
(25.31 g, 69.41 mmol) was added. The brown reaction mixture was kept at
40 458C for 24 h.[46] The reaction mixture was cooled (ice bath) and
poured onto 5n HCl (ca. 1 L) at such a rate that the temperature of the
acidic solution did not exceed 218C. The brown precipitate was filtered off
(B¸chner glass funnel), suspended in water, filtered off again, washed with
water, and dried (P4O10, 0.01 mbar). In most experiments filtering proceeds
rather slowly, therefore washing was kept to a minimum giving a crude
material full of salts. Column chromatography, first with petroleum ether to
elute the non-polar side products, then with petroleum ether/CH2Cl2 1:1 v/v
to elute undefined side products and finally with petroleum ether/diethyl
ether 1:1 v/v to elute the product 3 (16.8 g).[47] The latter was recrystallized
from hexane to give 3 (15.3 g, 61%) as a colorless solid. The compound was
made detectable by TLC with the aid of the ammonium salt of
8-anilinonaphthalin-1-sulfonic acid.[48] The isolated yields of other experi-
ments varied between 40 and 75%. M.p. 80.5 81.98C (lit.:[49] 76 788C);
1H NMR: d ˆ 3.62 (t, J ˆ 6.6 Hz, 2H, H-1), 2.16 (dt, 4J ˆ 2.6 Hz, 3J ˆ 7.0 Hz,
2H, H-23), 1.92 (t, J ˆ 2.6 Hz, 1H, H-25), 1.53 (m, 4H, H-2, -22), 1.24 (m,
42H, CH2); 13C NMR: d ˆ 84.8 (C-24), 68.0 (C-25),[50] 63.1 (C-1), 32.8,
29.7 28.5 (7 signals), 25.7, and 18.4 (CH2); elemental analysis calcd (%) for
C25H48O (364.658): C 82.34, H 13.27; found: C 82.39, H 13.30.
CH(CH3)2); 13C NMR: d ˆ 131.8, 131.3 (CHd), 124.1, 122.5 (Cd-4, Cd-1),
ꢀ
ꢀ
ꢀ
ꢀ
106.8 (C CSi), 92.5 (CH2C C), 92.0 (C CSi), 80.4 (CH2C C), 63.1
(HOCH2), 32.8, 29.7 28.7 (7 signals), 25.7, 19.5 (CH2), 18.6 (CH3), 11.3
(CH); elemental analysis calcd (%) for C42H72OSi (621.123): C 81.22, H
11.68; found: C 81.24, H 11.72.
4-{25-[4-(2-Triisopropylsilylethynyl)phenyl]pentacos-24-yn-1-yloxy}-1-io-
dobenzene (5b): Diisopropyl azodicarboxylate (5.3 mL, 26.9 mmol) was
added to a cooled (ice bath) solution of alkynol 4b (13.90 g, 22.37 mmol),
4-iodophenol (5.91 g, 26.9 mmol), and PPh3 (7.05 g, 26.9 mmol) in THF
(250 mL). The reaction is slightly exothermic. After 27 h (the reaction
needs less time for completion) at room temperature, the solvent was
removed in vacuo. Flash chromatography (petroleum ether/CH2Cl2 1:1 v/v,
Rf ˆ 0.96) gave 5b (16.3 g). The product was dissolved in CH2Cl2 (40 mL)
and this solution was added to ethanol (300 mL). The precipitate which
formed was isolated and washed with ethanol to give 5b (15.6 g 85%) as a
colorless solid. M.p. 70.8 72.08C; 1H NMR: d ˆ 7.52 (half of AA'XX', 2H,
Hg-2, -6), 7.36, 7.29 (AA'XX', 2H each, Hd), 6.65 (half of AA'XX', 2H, Hg-3,
ꢀ
-5), 3.88 (t, J ˆ 6.6 Hz, 2H, OCH2), 2.38 (t, J ˆ 7.0 Hz, 2H, CH2C C), 1.74
ꢀ
(m, 2H, OCH2CH2), 1.56 (m, 2H, CH2CH2C C), 1.5 1.2 (m, 38H, CH2),
1.10 (apparents, 21H, CH(CH3)2); 13C NMR: d ˆ 159.1 (Cg-4), 138.2 (Cg-2,
-6), 131.8, 131.3 (CHd), 124.1, 122.5 (Cd-1, -4), 117.0 (Cg-3, -5), 106.8
ꢀ
ꢀ
ꢀ
ꢀ
(C CSi), 92.5 (CH2C C), 92.0 (C CSi), 82.4 (Cg-1), 80.4 (CH2-C C), 68.2
(OCH2), 29.7 28.7 (7 signals), 26.0, 19.5 (CH2), 18.7 (CH3), 11.3 (CH);
elemental analysis calcd (%) for C48H75OISi (823.118): C 70.04, H 9.18;
found: C 70.06, H 9.06.
1-Bromo-4-(triisopropylsilylethynyl)benzene (18a): For a better control of
the reaction the following procedure is recommended instead of the
published one.[12] [Pd(PPh3)2Cl2] (101 mg, 0.14 mmol) and CuI (537 mg,
2.82 mmol) were added to a degassed solution of 1-bromo-4-iodobenzene
(40.00 g, 141 mmol) in piperidine (100 mL) and THF (150 mL). The flask
was immersed in an ice bath and triisopropylsilylacetylene (35 mL,
156 mmol) was added within 30 min (the temperature of the reaction
mixture was kept at 10 208C). The flaskwas left in the ice bath and the
reaction mixture and cooling bath were allowed to slowly reach room
temperature (ca. 3 h). The onset of the reaction can be seen due to the
formation of a precipitate. Removing the cooling bath too early results in a
sudden increase of the temperature. If the temperature of the reaction
mixture rises above 308C, a substantial amount of 1,4-bis(triisopropylsily-
lethynyl)benzene is formed. After stirring the reaction mixture overnight at
room temperature, diethyl ether and 2n HCl were added. This is an
exothermic reaction! The organic phase was washed twice with 2n HCl and
the combined aqueous phases were extracted with diethyl ether. The
combined organic phases were dried (MgSO4) and the solvent was removed
in vacuo. Distillation (140 1458C, 0.6 mbar) gave 18a (39 g, 82%) as a
slightly yellow liquid. The compound slowly decomposed with formation of
a precipitate, therefore storage under inert atmosphere in a freezer is
recommended. For analytical data see the reference.[12]
Additional note: Although the accompanying products of this reaction,
Ph3PO and diisopropyl hydrazodicarboxylate, can be removed by two
precipitations from a solution of the reaction product mixture in CH2Cl2 by
mixing with ethanol, column chromatography is necessary to remove a
product that is formed in small amounts and whose structure consists of the
alkynol and (part of) the azo/hydrazo reagent. This side product has a
comparatively small Rf value.
Ethyl 3,5-bis-{4-[2-(4-(25-(4-(2-triisopropylsilylethynyl)phenyl)pentacos-
24-yn-1-yloxy)phenyl)ethinyl]phenyl}-4-hydroxybenzoate
(7b):
[Pd(PPh3)2Cl2] (60 mg, 0.085 mmol) and CuI (33 mg, 0.17 mmol) were
added to a solution of 6 (3.13 g, 8.54 mmol) and 5b (15.50 g, 18.83 mmol) in
piperidine (250 mL). The reaction mixture was stirred for 21 h at room
temperature. It was cooled (ice bath) and poured into cold (ice bath) 5n
HCl (600 mL). The precipitate was filtered off, washed well with water, and
dried (P4O10, vacuum). Flash chromatography [petroleum ether/CH2Cl2 3:1
v/v was used until the first fraction, the residual iodo compound, was eluted
Rf (5b) ˆ 0.7. Then petroleum ether/CH2Cl2 1:1 v/v was used to elute the
product 7b; Rf (7b) ˆ 0.57] gave 5b (1.5 g, 10%) as a colorless solid and 7b
1
(11.0 g, 73%) as a slightly brown solid. M.p. 52.5 54.08C; H NMR: d ˆ
7.99 (s, 2H, Ha), 7.61, 7.53 (AA'XX', 4H each, Hb), 7.46 (half of AA'XX',
4H, Hg-2, -6), 7.36, 7.29 (AA'XX', 4H each, Hd), 6.86 (half of AA'XX', 4H,
Hg-3, -5), 5.76 (s, 1H, OH), 4.36 (q, J ˆ 7.1 Hz, 2H, CO2CH2), 3.96 (t, J ˆ
1-Iodo-4-(triisopropylsilylethynyl)benzene (19a): 1.6m nBuLi in hexane
(63 mL, 101 mmol) was added dropwise (ca. 30 min) to a solution of 18a
(30.0 g, 88.9 mmol) in THF (400 mL) at À788C. After stirring the solution
at À788C for 30 min, iodine (26.7 g, 105 mmol) was added as a solid. The
cooling bath was removed and the reaction mixture was allowed to come to
room temperature. Saturated aqueous Na2S2O3 was then added. The
aqueous phase was extracted with diethyl ether, the organic phase was
washed with saturated aqueous Na2S2O3 and dried (MgSO4). Distillation
(104 1088C, 0.01 mbar) gave iodo compound 19a (22 g, 64%) as a reddish
liquid. The product contained traces of the hydrolysis product (triisoprop-
ylsilylethynyl)benzene. 1H NMR: d ˆ 7.62 (half of AA'XX', 2H, H-2, -6),
ꢀ
6.6 Hz, 4H, ArOCH2), 2.38 (t, J ˆ 7.0 Hz, 4H, CH2C C), 1.77 (m, 4H,
ꢀ
OCH2CH2), 1.58 (m, 4H, CH2CH2C C), 1.38 (t, J ˆ 7.1 Hz, 3H, CH3), 1.5
1.2 (m, 76H, CH2), 1.10 (apparents, 42H, CH(CH3)2); 13C NMR: d ˆ 166.1
(CO2), 159.4 (Cg-4), 153.2 (Ca-4), 135.9 (Cb-1), 133.1 (Cg-2, -6), 132.0 (Cb-3, -5),
131.8 (Cd-2, -6 or Cd-3, -5), 131.6 (Ca-2, -6), 131.3 (Cd-3, -5 or Cd-2, -6), 129.3
(Cb-2, -6), 128.3 (Ca-3, -5), 124.1 (Cd-1 or Cd-4), 123.7 (Cb-4), 123.4 (Ca-1),
ꢀ
122.5 (Cd-4 or Cd-1), 114.9 (Cg-1), 114.6 (Cg-3,-5), 106.8 (C CSi), 92.5
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
(CH2C C), 92.0 (C CSi), 90.6 (C CArg), 87.6 (ArbC C), 80.4 (CH2C C),
68.1 (ArOCH2), 60.9 (CO2CH2), 29.7 28.7 (10 signals), 26.0, and 19.5
(CH2), 18.6 (CHCH32), 14.4 (CH2CH3), 11.3 (SiCH); elemental analysis
calcd (%) for C121H166O5Si2 (1756.826): C 82.72, H 9.52; found: C 82.71,
H 9.51.
7.18 (half of AA'XX', 2H, H-3, -5), 1.11 (apparents, 21H, CH(CH3)2);
13
ꢀ
C NMR: d ˆ 137.3 (CH), 133.5 (CH), 123.0 (C-4), 106.0 (C CSi), 94.1 (C-
ꢀ
1), 92.4 (C CSi), 18.6 (CH3), 11.3 (SiCH).
25-[4-(2-Triisopropylsilylethynyl)phenyl]pentacos-24-yn-1-ol
(4b):
Ethyl 3,5-bis-{4-[2-(4-(25-(4-ethynylphenyl)pentacos-24-yn-1-yloxy)pheny-
l)ethinyl]phenyl}-4-hydroxybenzoate (8b): 1m nBu4NF in THF (12.5 mL,
12.5 mmol) was added to a solution of 7b (10.89 g, 6.20 mmol) in THF
(110 mL) at room temperature. Immediately the solution showed a green
fluorescence. After 2 h of stirring, 2n HCl (13 mL) was added. The solution
turned colorless and a colorless precipitate formed. After addition of
ethanol (80 mL), the precipitate was isolated and washed well with water
and finally with ethanol, to give 8b (8.8 g, 99%) as a beige solid. Thermal
behavior determined by DSC (10 KminÀ1) and polarizing microscopy upon
[Pd(PPh3)2Cl2] (270 mg, 0.38 mmol) and CuI (146 mg, 0.77 mmol) were
added to a solution of pentacos-24-yn-1-ol (3) (13.82 g, 37.90 mmol) and
iodo compound 19a (16.02 g, 41.68 mmol) in piperidine (200 mL). After
21 h at room temperature, the reaction mixture was cooled (ice bath) and
poured into cold (ice bath) 5n HCl (450 mL). The precipitate was filtered
off, washed with water and dried (P4O10, vacuum). Flash chromatography
(CH2Cl2, Rf ˆ 0.5) gave 4b (15.5 g, 66%) as a colorless wax. M.p. 36.5
37.08C; 1H NMR: d ˆ 7.36, 7.29 (AA'XX', 2H each, ArH), 3.61 (t, J ˆ
5102
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Chem. Eur. J. 2002, 8, No. 22

Gigantocycles
5094 5106
first (second) heating scan: endothermic transition at 116 (112) and 123
(AA'XX', 4H each, Hb), 7.06 (half of AA'XX', 4H, Hg-2, -6), 7.06
(apparents, 8H, Hd), 6.81 (half of AA'XX', 4H, Hg-3, -5), 5.78 (s, OH), 4.36
(q, J ˆ 7.1 Hz, 2H, CO2CH2), 3.93 (t, J ˆ 6.6 Hz, 4H, ArOCH2), 2.93 (m,
8H, Arb(CH2)2Arg), 2.61 2.52 (m, 8H, CH2ArdCH2), 1.76 (m, 4H,
OCH2CH2), 1.38 (t, J ˆ 7.1 Hz, 3H, CH3), 1.7 1.2 (m, 92H, CH2);
13C NMR: d ˆ 166.4 (CO2), 157.5 (Cg-4), 153.4 (Ca-4), 141.8, 140.1, 139.7,
134.1, 133.3 (Cb-1, Cb-4, Cg-1, Cd-1, Cd-4), 131.3 (Ca-2, -6), 129.4, 129.20 (Cb-
2, -6, Cg-2, -6), 129.17 (Cb-3, -5), 128.6 (Ca-3, -5), 128.2 (CHd), 123.0 (Ca-1),
114.5 (Cg-3, -5), 68.0 (ArOCH2), 60.7 (CO2CH2), 37.8, 36.7, 35.5, 35.4, 31.5,
31.0 (ArCH2CH2), 29.6 29.3 (4 signals, CH2), 26.0 (CH2), 14.4 (CH2CH3);
elemental analysis calcd (%) for C103H148O5 (1466.312): C 84.37, H 10.17;
found: C 84.41, H 10.29.
(121)8C; with the microscope crystal ripening is observed at 116 1188C.
1
Above 1228C 8b forms an isotropic melt. H NMR: d ˆ 7.98 (s, 2H, Ha),
7.61, 7.51 (AA'XX', 4H each, Hb), 7.46 (half of AA'XX', 4H, Hg-2, -6), 7.38,
7.31 (AA'XX', 4H each, Hd), 6.86 (half of AA'XX', 4H, Hg-3, -5), 5.77 (s,
1H, OH), 4.36 (q, J ˆ 7.1 Hz, 2H, CO2CH2), 3.96 (t, J ˆ 6.5 Hz, 4H,
ꢀ
ꢀ
ArOCH2), 3.10 (s, 2H, C CH), 2.38 (t, J ˆ 7.0 Hz, 4H, CH2C C), 1.77 (m,
ꢀ
4H, OCH2CH2), 1.56 (m, 4H, CH2CH2C C), 1.38 (t, J ˆ 7.1 Hz, 3H, CH3),
1.5 1.2 (m, 76H, CH2); 13C NMR: d ˆ 166.1 (CO2), 159.4 (Cg-4), 153.2 (Ca-
4), 135.9 (Cb-1), 133.1 (Cg-2, -6), 132.0 (Cb-3, -5), 131.9 (Cd-2, -6 or Cd-3, -5),
131.6 (Ca-2, -6), 131.4 (Cd-3, -5 or Cd-2, -6), 129.3 (Cb-2, -6), 128.3 (Ca-3, -5),
124.7 (Cd-1 or Cd-4), 123.6, 123.4 (Ca-1, Cb-4), 121.1 (Cd-4 or Cd-1), 114.9
ꢀ
ꢀ
ꢀ
(Cg-1), 114.6 (Cg-3, -5), 92.8 (CH2C C), 90.6 (C CArg), 87.6 (ArbC C), 83.4
Tridec-12-inyltrimethylsilyl ether (11): Lithium acetylide ethylenediamine
complex (15.7 g, 171 mmol) was added portionwise at À308C to THF
(50 mL). The suspension was cooled to À208C and 1,3-dimethyl-1,3-
diazacyclohexan-2-on (125 mL) was added. At a temperature of À20 to
À108C 11-bromoundecyltrimethylsilyl ether (10) (50.0 g, 155 mmol) was
added dropwise. When the addition was complete, the cooling bath was
removed and the reaction mixture stirred for 24 h at room temperature. To
the cooled (ice bath) reaction mixture saturated aqueous NH4Cl and water
were added and the mixture extracted with diethyl ether. The combined
organic phases were washed with water and dried (MgSO4). Fractional
distillation (90 1058C, 10À2 mbar) using a Bˆsherz distillation column
gave 11 (23.7 g, 57%) as a colorless liquid containing ca. 5% of tridec-12-
yn-1-ol [determined by 1H NMR spectroscopy; characteristic signal: d ˆ
3.58 (t, J ˆ 6 Hz, 2H, HOCH2)]. The distillation fractions at lower
ꢀ
ꢀ
ꢀ
(C CH), 80.2 (CH2C C), 78.3 (C CH), 68.1 (ArOCH2), 60.9 (CO2CH2),
29.7 28.7 (10 signals), 26.0, and 19.5 (CH2), 14.4 (CH3); elemental analysis
calcd (%) for C103H126O5 (1444.136): C 85.67, H 8.79; found: C 85.31, H 8.95.
Gigantocycle 9b: A mixture of CuCl2 (1.20 g, 8.30 mmol) and CuCl (6.90 g,
69.7 mmol) was dried by gently heating (ca. 608C) it under a stream of
argon. After cooling to room temperature, pyridine (1 L) was added. The
suspension was heated to 508C for ca. 30 min to dissolve most of the copper
salts. After cooling to room temperature, solution of 8b (3.00 g, 2.07 mmol)
in pyridine (300 mL) was added to the resulting suspension within 240 h
using a syringe pump. It was necessary to gently heat the solution of 8b to
dissolve all of the starting material. Once in solution, 8b stays dissolved for
a sufficient time. After the addition was complete, the reaction mixture was
stirred for additional 24 h. Most of the solvent was removed (508C bath
temp., 10 mbar) and the residue was dissolved in CH2Cl2 and 2n HCl. The
organic phase was washed with 2n HCl until the aqueous phase stayed
acidic and the color of the organic phase had changed to yellow. The
combined aqueous phases were extracted with CH2Cl2 and the combined
organic phases were dried (MgSO4). The solvent was removed in vacuo.
Flash chromatography (petroleum ether/CH2Cl2 3:2 ! 1:1 v/v) gave macro-
cycle 9b (2.6 g, 87%) as a yellow solid.
temperature
contained
olefinic
material,
most
probably
H2C CH(CH2)9OTMS. 1H NMR: d ˆ 3.46 (t, J ˆ 6.7 Hz, 2H, OCH2),
ˆ
4
2.06 (dt, 3J ˆ 6.9 Hz, J ˆ 2.6 Hz, 2H, CH2C C), 1.81 (t, J ˆ 2.6 Hz, 1H,
ꢀ
ꢀ
ꢀ
C CH), 1.42 (m, 4H, OCH2CH2, CH2CH2C C), 1.4 1.1 (m, 14H, CH2),
0.00 (s, 9H, SiCH3); C NMR: d ˆ 84.3, 68.0 (C C), 62.5 (OCH2), 32.7,
13
ꢀ
29.5 28.4 (7 signals), 25.7, 18.2 (CH2), À0.6 (SiCH3); elemental analysis
calcd (%) for C16H32OSi (268.517): C 71.56, H 12.01; found: C 71.13, H
11.90.
The addition time can be significantly reduced. The addition of a solution of
8b (1.40g, 0.97 mmol) in pyridine (200 mL) to a suspension of CuCl2 (1.11 g,
8.23 mmol) and CuCl (6.44 g, 65.1 mmol) in pyridine (500 mL) within 56 h
gave macrocycle 9b (1.2 g, 83%). Thermal behavior determined by DSC
(10 KminÀ1) and polarizing microscopy upon first (second and third)
heating scan: Tcr-cr ˆ 147 (133)8C, Tcr-n ˆ 151 (142)8C, Tn-i ˆ 1618C;
1H NMR: d ˆ 7.99 (s, 2H, Ha), 7.61, 7.52 (AA'XX', 4H each, Hb), 7.46
(half of AA'XX', 4H, Hg-2, -6), 7.39, 7.30 (AA'XX', 4H each, Hd), 6.86 (half
of AA'XX', 4H, Hg-3, -5), 5.72 (s, 1H, OH), 4.36 (q, J ˆ 7.1 Hz, 2H,
CO2CH2), 3.97 (t, J ˆ 6.5 Hz, 4H, ArOCH2), 2.38 (t, J ˆ 7.0 Hz, 4H,
Additional note: Occasionally the amount of tridec-12-yn-1-ol was much
larger. In these cases, the product was silylated in a manner analogous to
the procedure given for the preparation of 10. The use of tridec-12-yn-1-ol
for coupling with 19a results in a distinctly larger amount of by-products
such as butadiynes (alkyne dimerization product) being produced. This is in
contrast to the smooth reaction of 3 that yielded only traces of butadiyne as
side product.
13-[4-(2-Triisopropylsilylethynyl)phenyl]tridec-12-yn-1-ol
(4a):
CuI
(145 mg, 0.76 mmol) and [PdCl2(PPh3)2] (266 mg, 0.38 mmol) were added
to a solution of 11 (10.19 g, 37.94 mmol) and 19a (17.50 g, 45.53 mmol) in
piperidine (133 mL). After stirring the reaction mixture for 2.5 h at room
temperature, the solvent was removed in vacuo and the residue was
dissolved in diethyl ether (100 mL). 2n HCl (100 mL) was added and the
reaction mixture was stirred overnight. The organic phase was washed with
2n HCl. The combined aqueous phases were extracted with diethyl ether
and the combined organic phases were dried (Na2SO4). The solvent was
removed in vacuo. Flash chromatography (petroleum ether/CH2Cl2 1:1 v/v;
Rf ˆ 0.12) gave alkynol 4a (14.5 g, 85%) as a yellow oil. 1H NMR: d ˆ 7.36,
7.28 (AA'XX', 2H each, ArH), 3.56 (t, J ˆ 6.6 Hz, 2H, CH2OH), 2.56 (s,
ꢀ
ꢀ
CH2C C), 1.77 (m, 4H, OCH2CH2), 1.57 (m, 4H, CH2CH2C C), 1.38 (t,
J ˆ 7.1 Hz, 3H, CH3), 1.5 1.2 (m, 76H, CH2); 13C NMR: d ˆ 166.1 (CO2),
159.4 (Cg-4), 153.2 (Ca-4), 135.9 (Cb-1), 133.1 (Cg-2, -6), 132.3 (Cd-2, -6 or
Cd-3, -5), 132.0 (Cb-3, -5), 131.6 (Cd-3, -5 or Cd-2, -6), 131.5 (Ca-2, -6), 129.3
(Cb-2, -6), 128.3 (Ca-3, -5), 125.2 (Cd-1 or Cd-4), 123.6, 123.4 (Ca-1, Cb-4),
ꢀ
120.6 (Cd-4 or Cd-1), 115.0 (Cg-1), 114.7 (Cg-3, -5), 93.6 (CH2C C), 90.6
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
(C CArg), 87.6 (ArbC C), 82.0 (C C-C C), 80.2 (CH2C C), 75.2 (C C-
ꢀ
C C), 68.1 (ArOCH2), 61.0 (CO2CH2), 29.6 28.7 (9 signals), 25.9, and 19.5
(CH2), 14.4 (CH3); UV/Vis: l (e [106 cm2 molÀ1]) ˆ 265 (496), 281 (582), 297
(790), 312 (1020), 333 (919), 359 nm (4271 106 cm2 molÀ1); emission
(lexcitation ˆ 310 nm) l ˆ 367, 397 nm; elemental analysis calcd (%) for
C103H124O5 (1442.120): C 85.79, H 8.67; found: C 85.86, H 8.68.
ꢀ
1H, OH), 2.37 (t, J ˆ 7.0 Hz, 2H, CH2C C), 1.54 (m, 4H, CH2CH2OH,
ꢀ
CH2CH2C C), 1.5 1.2 (m, 14H, CH2), 1.10 (apparents, 21H, CH(CH3)2);
13
ꢀ
Hydrogenated gigantocycle 28: Pd/C (10%; 3 mg, 3 Â 10À4 mmol) was
added to a solution of macrocycle 9b (324 mg, 0.22 mmol) in THF (20 mL).
Hydrogen was introduced from a balloon by means of a glass tube which
dipped into the suspension. After 3 d at room temperature a second portion
of Pd/C (10%; 3 mg, 3 Â 10À4 mmol) was added and the reaction mixture
was stirred for another 2 d under a layer of hydrogen. The catalyst was
removed by filtration. The solvent was removed and the residue purified by
chromatography (petroleum ether/CH2Cl2 1:1 ! 1:2 v/v) to yield 28
(263 mg, 80%) as a colorless solid. Due to a proton signal at 5.5 ppm the
reaction was believed to be incomplete after 3 d therefore more Pd/C was
added. However, the intensity of this signal increased upon further
reaction. To avoid this side reaction, a shorter reaction time is recom-
mended. Thermal behavior determined by DSC (10 KminÀ1) and polariz-
ing microscopy upon first (second and third) heating scan: melting at 78
(79), crystallization at 80 (86), melting at 106 and 110 (107)8C; upon
cooling: crystallization at 718C; 1H NMR: d ˆ 7.97 (s, 2H, Ha), 7.45, 7.25
C NMR: d ˆ 131.6, 131.2 (CHd), 124.1, 122.4 (Cd-4, Cd-1), 106.8 (C CSi),
ꢀ
ꢀ
ꢀ
92.3 (CH2C C), 91.8 (C CSi), 80.3 (CH2C C), 62.6 (HOCH2), 32.6, 29.5
28.6 (7 signals), 25.7,/19.4 (CH2), 18.5 (CH3), 11.2 (CH); elemental analysis
calcd (%) for C30H48OSi (452.799): C 79.58, H 10.68; found: C 79.59, H
10.60.
4-{13-[4-(2-Triisopropylsilylethynyl)phenyl]tridec-12-yn-1-yloxy}-1-iodo-
benzene (5a): Diisopropyl azodicarboxylate (15.9 mL, 80.7 mmol) was
added to a solution of alkynol 4a (27.62 g, 61.00 mmol), 4-iodophenol
(17.76 g, 80.70 mmol), and PPh3 (21.17 g, 80.70 mmol) in THF (400 mL).
This is an exothermic reaction. After stirring the reaction mixture for 3 h at
room temperature, the solvent was removed in vacuo. Flash chromatog-
raphy (petroleum ether/CH2Cl2 1:1 v/v; Rf ˆ 0.89) gave 5a as a brown oil
which slowly solidified. Recrystallization from ethanol (ca. 400 mL) gave
5a (29.4 g, 73%) as a colorless solid. M.p. 39.1 39.98C; 1H NMR: d ˆ 7.52
(half of AA'XX', 2H, Hg-2, -6), 7.37, 7.30 (AA'XX', 2H each, Hd), 6.65 (half
of AA'XX', 2H, Hg-3, -5), 3.88 (t, J ˆ 6.6 Hz, 2H, OCH2), 2.39 (t, J ˆ 7.0 Hz,
Chem. Eur. J. 2002, 8, No. 22
¹ 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
0947-6539/02/0822-5103 $ 20.00+.50/0
5103

A. Godt et al.
FULL PAPER
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2H, CH2C C), 1.74 (m, 2H, OCH2CH2), 1.59 (m, 2H, CH2CH2C C), 1.5
1.2 (m, 14H, CH2), 1.12 (apparents, 21H, CH(CH3)2); 13C NMR: d ˆ 159.0
(Cg-4), 138.1 (Cg-2, -6), 131.8, 131.3 (CHd), 124.1, 122.5 (Cd-1, -4), 117.0 (Cg-
(CH2C C), 75.2 (C C-C C), 67.9 (ArOCH2), 61.0 (CO2CH2), 29.2 28.6
(7 signals), 25.6, and 19.5 (CH2), 14.4 (CH3); elemental analysis calcd (%)
for C79H76O5 (1105.472): C 85.83, H 6.93; found: C 85.47, H 6.76; FD-MS:
‡
‡
m/z (%): 2210.0 (24) [2M] , 1105.3 (100) [M] , 552.9 (8)[M]2‡
.
ꢀ
ꢀ
ꢀ
3, -5), 106.8 (C CSi), 92.5 (CH2C C), 92.0 (C CSi), 82.4 (Cg-1), 80.4
(CH2C C), 68.1 (OCH2), 29.5 28.7 (7 signals), 26.0, 19.5 (CH2), 18.6
(CH3), 11.3 (CH); elemental analysis calcd (%) for C36H51IOSi (654.794): C
66.04, H 7.85; found: C 66.113, H 7.88.
ꢀ
3,5-Dimethyl-4-{25-[4-(2-triisopropylsilylethynyl)phenyl]pentacos-24-yn-1-
yloxy}-1-iodobenzene (12): Following the procedure given for the prepa-
ration of 5b, compound 12 was prepared, starting from 4b (10.08 g,
16.2 mmol), 2,6-dimethyl-4-iodophenol (4.80 g, 19.3 mmol), PPh3 (5.10 g,
19.4 mmol), and diisopropyl azodicarboxylate (3.84 mL, 19.5 mmol) in
THF (175 mL). Flash chromatography (petroleum ether/CH2Cl2 1:1 v/v;
Rf ˆ 0.95) gave slightly impure 12 (13 g). This material was dissolved in
CH2Cl2 (30 mL) and the solution was added to ethanol (200 mL). The
resulting precipitate was isolated to give 12 (11.4 g, 82%) as a colorless
Ethyl 3,5-bis-{4-[2-(4-(13-(4-(2-triisopropylsilylethynyl)phenyl)tridec-12-
yn-1-yloxy)phenyl)ethinyl]phenyl}-4-hydroxybenzoate (7a): CuI (30 mg,
0.16 mmol) and [PdCl2(PPh3)2] (57 mg, 0.08 mmol) were added to a
degassed solution of terphenylene 6 (3.00 g, 8.19 mmol) and iodo com-
pound 5a (11.79 g, 18.01 mmol) in piperidine (150 mL). After stirring the
reaction mixture for 3 h at room temperature the piperidine was removed
in vacuo and the residue was dissolved in CH2Cl2 and 2n HCl. The organic
phase was washed with 2n HCl and the combined aqueous phases were
extracted with CH2Cl2. The combined organic phases were dried (Na2SO4).
The solvent was removed in vacuo. Flash chromatography (petroleum
ether/CH2Cl2 1:1 v/v; Rf (5a) ˆ 0.92, Rf (7a) ˆ 0.70) gave 7a (9.7 g, 83%) as
a highly viscous, slightly brown oil. 1H NMR: d ˆ 7.99 (s, 2H, Ha), 7.62, 7.53
(AA'XX', 4H each, Hb), 7.47 (half of AA'XX', 4H, Hg-2, -6), 7.38, 7.31
(AA'XX', 4H each, Hd), 6.87 (half of AA'XX', 4H, Hg-3, -5), 5.82 (s, 1H,
OH), 4.37 (q, J ˆ 7.1 Hz, 2H, CO2CH2), 3.95 (t, J ˆ 6.5 Hz, 4H, ArOCH2),
1
solid. M.p. 46.2 46.88C; H NMR: d ˆ 7.37, 7.30 (AA'XX', 2H each, He),
7.32 (s, 2H, Hd-2, -6), 3.70 (t, J ˆ 6.6 Hz, 2H, OCH2), 2.39 (t, J ˆ 7.0 Hz, 2H,
ꢀ
CH2C C), 2.21 (s, 6H, ArCH3), 1.77 (m, 2H, OCH2CH2), 1.57 (m, 2H,
ꢀ
CH2CH2C C), 1.5 1.2 (m, 38H, CH2), 1.12 (apparents, 21H, CH(CH3)2);
13C NMR d ˆ 156.1 (Cd-4), 137.4 (Cd-2, -6), 133.6 (Cd-3, -5), 131.8, 131.3
ꢀ
ꢀ
(CHe), 124.1, 122.5 (Ce-1, Ce-4), 106.8 (C CSi), 92.5 (CH2C C), 92.0
ꢀ
ꢀ
(C CSi), 87.3 (Cd-1), 80.3 (CH2C C), 72.5 (OCH2), 30.3 28.7 (8 signals),
26.1, 19.5 (CH2), 18.6 (CHCH3), 15.9 (ArCH3), 11.3 (SiCH); elemental
analysis calcd (%) for C50H79OISi (851.172): C 70.56, H 9.36; found: C
70.56, H 9.41.
ꢀ
2.4 (t, J ˆ 7.0 Hz, 4H, CH2C C), 1.78 (m, 4H, OCH2CH2), 1.57 (m, 4H,
ꢀ
C CCH2CH2), 1.5 1.2 (m, 28H, CH2), 1.12 (apparents, 42H, CH(CH3)2);
25-{3,5-Dimethyl-4-[25-(4-(2-triisopropylsilylethynyl)phenyl)pentacos-24-
yn-1-yloxy]-1-iodophenyl}pentacos-24-yn-1-ol (13): [Pd(PPh3)2Cl2] (17 mg,
0.02 mmol) and CuI (9 mg, 0.05 mmol) were added to a solution of iodo
compound 12 (2.22 g, 2.60 mmol) and alkynol 3 (0.86 g, 2.36 mmol) in
piperidine (40 mL) at room temperature. After stirring the reaction
mixture at 508C for 19 h, the reaction mixture was cooled (ice bath) and
poured into cold (ice bath) 5n HCl (200 mL). The brown colored
precipitate was filtered off, washed with water and dried (P4O10, vacuum).
Flash chromatography (petroleum ether/CH2Cl2 1:2 v/v; Rf (12) ˆ 0.96, Rf
(13) ˆ 0.51) gave 13 (1.75 g, 68%) as a brownish solid. M.p. 76.5 77.08C;
1H NMR: d ˆ 7.37, 7.30 (AA'XX', 2H each, He), 7.04 (s, 2H, Hd-2, -6), 3.71
(t, J ˆ 6.6 Hz, 2H, ArOCH2), 3.63 (t, J ˆ 6.6 Hz, 2H, HOCH2), 2.39, 2.35 (2
13C NMR: d ˆ 166.1 (CO2), 159.4 (Cg-4), 153.2 (Ca-4), 135.9 (Cb-1), 133.1
(Cg-2, -6), 131.9 (Cb-3, -5), 131.8 (Cd-2, -6 or Cd-3, -5), 131.5 (Ca-2, -6), 131.3
(Cd-3, -5 or Cd-2, -6), 129.2 (Cb-2, -6), 128.3 (Ca-3, -5), 124.1 (Cd-1 or Cd-4),
123.6 (Cb-4), 123.3 (Ca-1), 122.5 (Cd-4 or Cd-1), 114.9 (Cg-1), 114.6 (Cg-3,-5),
ꢀ
ꢀ
ꢀ
ꢀ
106.8 (C CSi), 92.5 (CH2C C), 92.0 (C CSi), 90.6 (C CArg), 87.6
ꢀ
ꢀ
(ArbC C), 80.4 (CH2C C), 68.1 (ArOCH2), 60.9 (CO2CH2), 29.5 28.7
ꢀ
ꢀ
(7 signals, CH2), 26.0 (CH2CH2C C), 19.5 (CH2C C), 18.6 (CHCH3), 14.4
(CH3), 11.3 (SiCH); elemental analysis calcd (%) for C97H118O5Si2
(1420.167): C 82.04, H 8.37; found: C 81.99, H 8.29.
Ethyl 3,5-bis-{4-[2-(4-(13-(4-ethynylphenyl)tridec-12-yn-1-yloxy)phenyl)-
ethinyl]phenyl}-4-hydroxybenzoate (8a): 1m nBu4NF in THF (17.3 mL,
17.3 mmol) was added to a solution of 7a (11.18 g, 7.87 mmol) in THF
(100 mL). After stirring for 2 h, 2n HCL (11.8 mL) was added. After the
addition of ethanol (200 mL) 8a (8.4 g, 96%) was obtained as a colorless
solid. M.p. 132.0 133.78C; 1H NMR: d ˆ 7.99 (s, 2H, Ha), 7.61, 7.53
(AA'XX', 4H each, Hb), 7.48 (half of AA'XX', 4H, Hg-2, -6), 7.40, 7.33
(AA'XX', 4H each, Hd), 6.87 (half of AA'XX', 4H, Hg-3, -5), 5.85 (s, 1H,
OH), 4.36 (q, J ˆ 7.1 Hz, 2H, CO2CH2), 3.94 (t, J ˆ 6.5 Hz, 4H, ArOCH2),
ꢀ
t, J ˆ 7.0 Hz, 2H each, CH2C C), 2.21 (s, 6H, ArCH3), 1.77 (m, 2H,
ꢀ
ArOCH2CH2), 1.57 (m, 6H, CH2CH2C C, HOCH2CH2), 1.5 1.2 (m, 76H,
CH2), 1.11 (apparents, 21H, CH(CH3)2); 13C NMR d ˆ 155.8 (Cd-4), 131.9
(CHd), 131.8, 131.3 (CHe), 130.9 (Cd-3,-5), 124.1, 122.5 (Ce-1, Ce-4), 119.0
ꢀ
ꢀ
ꢀ
ꢀ
(Cd-1), 106.8(C CSi), 92.5 (CH2C CAre), 92.0 (C CSi), 89.0 (CH2C CArd),
80.33, 80.32 (CH2C C), 72.4 (ArOCH2), 63.1 (HOCH2), 32.8 28.7
(12 signals), 26.1, 25.7, 19.5, 19.4 (CH2), 18.6 (CHCH3), 16.1 (ArCH3),
11.3 (SiCH); elemental analysis calcd (%) for C75H126O2Si (1087.917): C
82.80, H 11.67; found: C 82.64, H 11.73.
ꢀ
ꢀ
ꢀ
3.13 (s, 2H, C CH), 2.40 (t, J ˆ 7.0 Hz, 4 H, CH2C C), 1.77 (m, 4H,
ꢀ
OCH2CH2), 1.60 (m, 4H, CH2CH2C C), 1.38 (t, J ˆ 7.1 Hz, 3H, CH3), 1.5
1.2 (m, 28H, CH2); 13C NMR: d ˆ 166.0 (CO2), 159.3 (Cg-4), 153.2 (Ca-4),
135.9 (Cb-1), 133.0 (Cg-2, -6), 131.9 (Cb-3, -5), 131.8 (Cd-2, -6 or Cd-3, -5),
131.5 (Ca-2, -6), 131.4 (Cd-3, -5 or Cd-2, -6), 129.2 (Cb-2, -6), 128.3 (Ca-3, -5),
124.7 (Cd-1 or Cd-4), 123.5, 123.3 (Ca-1, Cb-4), 121.0 (Cd-4 or Cd-1), 114.9
4-{25-[3,5-Dimethyl-4-(25-(4-(2-triisopropylsilylethynyl)phenyl)pentacos-
24-yn-1-yloxy)phenyl]pentacos-24-yn-1-yloxy}-1-iodobenzene (14): Fol-
lowing the procedure given for the preparation of 5b, compound 14 was
obtained starting from 13 (7.18 g, 6.60 mmol), 4-iodophenol (1.75 g,
7.95 mmol), PPh3 (2.10 g, 8.01 mmol), and diisopropyl azodicarboxylate
(1.58 mL, 8.02 mmol) in THF (300 mL). Flash chromatography (petroleum
ether/CH2Cl2 1:2 v/v; Rf ˆ 0.97) gave slightly impure 14. This product was
dissolved in warm CH2Cl2 (30 mL) and the solution was added to ethanol
(250 mL) to precipitate 14 (6.6 g, 78%) as a colorless solid. M.p. 63.9
64.78C; 1H NMR: d ˆ 7.53 (half of AA'XX', 2H, Hg-2, -6), 7.37, 7.30
(AA'XX', 2H each, He), 7.05 (s, 2H, ArHd), 6.66 (half of AA'XX', 2H, Hg-
3, -5), 3.89 (t, J ˆ 6.6 Hz, 2H, ArgOCH2), 3.71 (t, J ˆ 6.6 Hz, 2H, ArdOCH2),
ꢀ
ꢀ
ꢀ
(Cg-1), 114.5 (Cg-3, -5), 92.7 (CH2C C), 90.6 (C CArg), 87.6 (ArbC C), 83.3
ꢀ
ꢀ
ꢀ
(C CH), 80.2 (CH2C C), 78.4 (C CH), 68.0 (ArOCH2), 60.9 (CO2CH2),
29.5 28.6 (7 signals), 26.0, 19.4 (CH2), 14.4 (CH3); FD-MS: m/z (%):
1106.9 (100) [M] , 553.4 (66) [M]2‡. A correct elemental analysis was not
‡
obtained.
Gigantocycle 9a: A suspension of CuCl (8.94 g, 90.3 mmol) and CuCl2
(1.46 g, 10.8 mmol) in pyridine (1.5 L) was prepared as described for the
preparation of 9b. To this suspension was added a solution of 8a (1.00 g,
0.90 mmol) in pyridine (100 mL) at room temperature within 70 h by
means of a syringe pump. When the addition was complete the reaction
mixture was stirred for an additional 24 h. Workup as described for 9b
followed by flash chromatography (petroleum ether/CH2Cl2 1:1 v/v; Rf ˆ
0.47) gave 9a (813 mg, 82%). M.p. 2018C; 1H NMR: d ˆ 8.00 (s, 2H, Ha),
7.61, 7.51 (AA'XX', 4H each, Hb), 7.47 (half of AA'XX', 4H, Hg-2, -6), 7.39,
7.31 (AA'XX', 4H each, Hd), 6.87 (half of AA'XX', 4H, Hg-3, -5), 5.72 (s,
1H, OH), 4.37 (q, J ˆ 7.1 Hz, 2H, CO2CH2), 4.01 (t, J ˆ 6.3 Hz, 4H,
ꢀ
2.39, 2.36 (2t, J ˆ 7.0 Hz, 2H each, CH2C C), 2.21 (s, 6H, ArCH3), 1.75 (m,
ꢀ
4H, OCH2CH2), 1.56 (m, 4H, CH2CH2C C), 1.5 1.2 (m, 76H, CH2), 1.12
(apparents, 21H, CH(CH3)2); 13C NMR d ˆ 159.0 (Cg-4), 155.8 (Cd-4),
138.1 (Cg-2, -6), 132.0 (CHd), 131.8, 131.3 (CHe), 130.9 (Cd-3, -5), 124.1,
ꢀ
122.5 (Ce-1, -4), 119.1 (Cd-1), 117.0 (Cg-3, -5), 106.8 (C CSi), 92.5
ꢀ
ꢀ
ꢀ
(CH2C CAre), 92.0 (C CSi), 89.0 (CH2C CArd), 82.4 (Cg-1), 80.4, 80.3
ꢀ
(CH2C C), 72.4 (ArdOCH2), 68.1 (ArgOCH2), 30.4 28.7 (12 signals), 26.1,
26.0, 19.5, and 19.4 (CH2), 18.7 (CHCH3), 16.1 (ArCH3), 11.3 (SiCH);
elemental analysis calcd (%) for C81H129O2ISi (1289.912): C 75.42, H 10.08;
found: C 75.49, H 10.05.
ꢀ
ArOCH2), 2.38 (t, J ˆ 7.0 Hz, 4H, CH2C C), 1.76 (m, 4H, OCH2CH2), 1.58
ꢀ
(m, 4H, CH2CH2C C), 1.38 (t, J ˆ 7.1 Hz, 3H, CH3), 1.50 1.20 (m, 28H,
CH2); 13C NMR: d ˆ 166.2 (CO2), 159.3 (Cg-4), 153.3 (Ca-4), 135.8 (Cb-1),
133.1 (Cg-2, -6), 132.2 (Cd-2, -6 or Cd-3, -5), 132.0 (Cb-3, -5), 131.5 (Cd-3, -5 or
Cd-2, -6), 131.3 (Ca-2, -6), 129.3 (Cb-2, -6), 128.3 (Ca-3 -5), 125.2 (Cd-1 or Cd-
4), 123.6, 123.3 (Ca-1, Cb-4), 120.6 (Cd-4 or Cd-1), 115.0 (Cg-1), 114.8 (Cg-3, -
Ethyl 3,5-bis-{4-[25-(3,5-dimethyl-4-(25-(4-(2-triisopropylsilylethynyl)phe-
nyl)pentacos-24-yn-1-yloxy)phenyl)pentacos-24-yn-1-yloxy]phenyl}-4-hy-
droxybenzoate (15): [Pd(PPh3)2Cl2] (37 mg, 0.05 mmol) and CuI (20 mg,
0.11 mmol) were added to a solution of terphenylene 6 (0.833 g, 2.27 mmol)
and iodo compound 14 (6.45 g, 5.00 mmol) in piperidine (120 mL). The
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
5), 93.6 (CH2C C), 90.7 (C CArg), 87.7 (ArbC C), 82.0 (C C-C C), 80.2
5104
¹ 2002 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
0947-6539/02/0822-5104 $ 20.00+.50/0
Chem. Eur. J. 2002, 8, No. 22

Gigantocycles
5094 5106
reaction mixture was stirred for 19 h at room temperature. It was cooled
(ice bath) and poured into cold (ice bath) 5n HCl (600 mL). The
precipitate was filtered off, washed with water, and dried (P4O10, vaccum).
Flash chromatography [Petroleum ether/CH2Cl2 2:1 v/v was used until the
first fraction, residual iodo compound 14, was eluted Rf (14) ˆ 0.87, then
petroleum ether/CH2Cl2 1:1 v/v was used to elute the product 15; Rf (15) ˆ
0.63.] gave 15 (4.7 g, 76%) as a brownish solid. M.p. 66.2 66.88C;
1H NMR: d ˆ 8.01 (s, 2H, Ha), 7.63, 7.55 (AA'XX', 4H each, Hb), 7.48 (half
of AA'XX', 4H, Hg-2, -6), 7.38, 7.31 (AA'XX', 4H each, CHe), 7.06 (s, 4H,
ArHd), 6.88 (half of AA'XX', 4H, Hg-3, -5), 5.82 (brs, 1H, OH), 4.38 (q, J ˆ
7.1 Hz, 2H, CO2CH2), 3.96 (t, J ˆ 6.6 Hz, 4H, ArgOCH2), 3.72 (t, J ˆ 6.6 Hz,
Ce-4), 123.6 (Cb-4), 123.4 (Ca-1), 120.6 (Ce-4 or Ce-1), 119.1 (Cd-1), 115.0
ꢀ
ꢀ
(Cg-1), 114.6 (Cg-3, -5), 93.6 (CH2C CAre), 90.6 (C CArg), 89.0
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
(CH2C CArd), 87.6 (ArbC C), 82.0 (C C-C C), 80.4, 80.3 (CH2C C),
ꢀ
ꢀ
75.2 (C C-C C), 72.4 (ArdOCH2), 68.1 (ArgOCH2), 60.9 (CO2CH2), 30.4
28.6 (7 signals), 26.1, 26.0, 19.5, 19.4 (CH2), 16.1 (ArCH3), 14.4 (CH2CH3);
elemental analysis calcd (%) for C169H232O7 (2375.708): C 85.44, H 9.84;
found: C 85.29, H 9.82.
[1] Molecular Catenanes, Rotaxanes and Knots (Eds.: J.-P. Sauvage, C.
Dietrich-Buchecker), Wiley-VCH, Weinheim, 1999.
[2] For example: Macrocyclic Chemistry, B. Dietrich, P. Viout, J.-M. Lehn,
VCH, Weinheim, 1993.
[3] S. Hˆger, V. Enkelmann, K. Bonrad, C. Tschierske, Angew. Chem.
2000, 112, 2356; Angew. Chem. Int. Ed. 2000, 39, 2268; T. Hegmann, B.
Neumann, J. Kain, S. Diele, C. Tschierske, J. Mater. Chem. 2000, 10,
2244.
ꢀ
4H, ArdOCH2), 2.40, 2.37 (2t, J ˆ 7.0 Hz, 4H each, CH2C C), 2.22 (s, 12H,
ꢀ
ArCH3), 1.78 (m, 8H, OCH2CH2), 1.59 (m, 8H, CH2CH2C C), 1.39 (t, J ˆ
7.1 Hz, 3H, CH2CH3), 1.5 1.2 (m, 152H, CH2), 1.13(apparents, 21H,
CH(CH3)2); 13C NMR: d ˆ 166.1 (CO2), 159.4 (Cg-4), 155.8 (Cd-4), 153.2
(Ca-4), 135.9 (Cb-1), 133.1 (Cg-2, -6), 131.9 (Cb-3, -5, CHd), 131.8 (CHe),
131.5 (Ca-2, -6), 131.3 (CHe), 130.9 (Cd-3, -5), 129.2 (Cb-2, -6), 128.3 (Ca-3, -
5), 124.1 (Ce-1 or Ce-4), 123.6 (Cb-4), 123.3 (Ca-1), 122.5 (Ce-4 or Ce-1), 119.1
[4] F. Navarro, Macromol. Symp. 1998, 128, 99.
[5] D. Joachimi, P. R. Ashton, C. Sauer, N. Spencer, C. Tschierske, K. Zab,
Liq. Cryst. 1996, 20, 337.
[6] B. Neumann, D. Joachimi, C. Tschierske, Adv. Mater. 1997, 9, 241.
[7] For example: a) V. Percec, M. Kawasumi, P. L. Rinaldi, V. E. Litman,
Macromolecules 1992, 25, 3851; b) V. Percec, P. J. Turkaly, A. D.
Asandei, Macromolecules 1997, 30, 943.
ꢀ
ꢀ
(Cd-1), 115.0 (Cg-1), 114.5 (Cg-3, -5), 106.8 (C CSi), 92.5 (CH2C CAre),
ꢀ
ꢀ
ꢀ
ꢀ
92.0 (C CSi), 90.6 (C CArg), 89.0 (CH2C CArd), 87.6 (ArbC C), 80.4, 80.3
ꢀ
(CH2C C), 72.4 (ArdOCH2), 68.1 (ArgOCH2), 60.9 (CO2CH2), 30.4 28.7
(12 signals), 26.1, 26.0, 19.5, 19.4 (CH2), 18.6 (CHCH3), 16.1 (ArCH3), 14.4
(CH2CH3), 11.3 (SiCH); elemental analysis calcd (%) for C187H274O7Si2
(2690.414): C 83.48, H 10.27; found: C 83.28, H 10.33.
Ethyl 3,5-bis-{4-[25-(3,5-dimethyl-4-(25-(4-(ethynylphenyl)pentacos-24-
yn-1-yloxy)-phenyl)pentacos-24-yn-1-yloxy]phenyl}-4-hydroxybenzoate (16):
Following the procedure given for the preparation of 8b, ring precursor 16
(3.7 g, 95%) was obtained as a very pale beige colored solid from treatment
of 15 (4.45 g, 1.65 mmol) in THF (60 mL) with 1m nBu4NF in THF (3.3 mL,
3.3 mmol) and workup with 2n HCl (5 mL) and ethanol (120 mL). M.p.
[8] Review on monodisperse giganto- and ultracycles: V. Prautzsch, S.
Ibach, F. Vˆgtle, J. Incl. Phenom. Macrocyclic Chem. 1999, 33, 427; see
also H. Schwierz, F. Vˆgtle, J. Incl. Phenom. Macrocyclic Chem. 2000,
37, 309 and references therein.
[9] Examples of cyclic macromolecules: H. Oike, H. Imaizumi, T. Mouri,
Y. Yoshioka, A. Uchibori, Y. Tezuka, J. Am. Chem. Soc. 2000, 122,
9592; M. Kubo, T. Hayashi, H. Kobayashi, T. Itoh, Macromolecules
1998, 31, 1053; L. Rique-Lurbet, M. Schappacher, A. Deffieux,
Macromolecules 1994, 27, 6318; B. Lepoittevin, M.-A. Dourges, M.
Masure, P. Hemery, K. Baran, H. Cramail, Macromolecules 2000, 33,
8218.
[10] Large Ring Molecules, J. A. Semlyen, Wiley, New York, 1996.
[11] For example:G. Pelzl, S. Diele, W. Weissflog, Adv. Mater. 1999, 11, 707;
J. Thisayukta, Y. Nakayama, J. Watanabe, Liq. Cryst. 2000, 27, 1129; T.
Akutagawa, Y. Matsunaga, K. Yasuhara, Liq. Cryst. 1994, 17, 659.
[12] A. Godt, ÷. ‹nsal, M. Roos, J. Org. Chem. 2000, 65, 2837. For
purification of 6, the column chromatography after the desilylation
step can be substituted by dissolving the crude product in methylene
chloride (ca. 35 mL, 12 g starting material) and dropping this solution
into petroleum ether (ca. 600 mL) to precipitate the product as a
colorless solid (83 87%).
[13] T. Mukhopadhyay, D. Seebach, Helv. Chim. Acta 1982, 65, 385.
[14] See also: S. Poulain, N. Noiret, C. Nugier-Chauvin, H. Patin, Lieb.
Ann./Recueil 1997, 35; C. Cai, A. Vasella, Helv. Chim. Acta 1995, 78,
732.
[15] For example: A. Sharma, S. Chattopadhyay, J. Org. Chem. 1998, 63,
6128; K. Mori, H. Tomioka, Lieb. Ann. Chem. 1992, 1011; P. Dussault,
I. Q. Lee, J. Org. Chem. 1995, 60, 218.
[16] DMSO has been described as a suitable solvent for the reaction of
ethynyllithium with bromoalkanes: W. N. Smith, O. F. Beumel, Jr.,
Synthesis 1974, 441. However, we found that by-products due to the
formation of the dimsyl anion were formed.
[17] This side product was obtained as the residue upon distillation of the
crude product. The formation can be avoided using trimethylsilyl-
ethynyllithium instead of ethynyllithium. The product TMSO-
1
1008C; H NMR: d ˆ 8.00 (s, 2H, Ha), 7.62, 7.54 (AA'XX', 4H each, Hb),
7.47 (half of AA'XX', 4H, Hg-2, -6), 7.39, 7.32 (AA'XX', 4H each, CHe), 7.05
(s, 4H, ArHd), 6.87 (half of AA'XX', 4H, Hg-3, -5), 5.77 (s, 1H, OH), 4.38
(q, J ˆ 7.1 Hz, 2H, CO2CH2), 3.97 (t, J ˆ 6.6 Hz, 4H, ArgOCH2), 3.71 (t, J ˆ
ꢀ
6.6 Hz, 4H, ArdOCH2), 3.12 (s, 2H, C CH), 2.39, 2.36 (2t, J ˆ 7.0 Hz, 4H
ꢀ
each, CH2C C), 2.21 (s, 12H, ArCH3), 1.78 (m, 8H, OCH2CH2), 1.57 (m,
ꢀ
8H, CH2CH2C C), 1.39 (t, J ˆ 7.1 Hz, 3H, CH2CH3), 1.5 1.2 (m, 152H,
CH2); 13C NMR: d ˆ 166.1 (CO2), 159.4 (Cg-4), 155.8 (Cd-4), 153.2 (Ca-4),
135.9 (Cb-1), 133.1 (Cg-2, -6), 132.0 (Cb-3, -5, CHd), 131.9 (CHe), 131.6 (Ca-
2,-6), 131.4 (CHe), 130.9 (Cd-3, -5), 129.3 (Cb-2, -6), 128.3 (Ca-3, -5), 124.7
(Ce-1 or Ce-4), 123.7 (Cb-4), 123.4 (Ca-1), 121.1 (Ce-4 or Ce-1), 119.1 (Cd-1),
ꢀ
ꢀ
115.0 (Cg-1), 114.6 (Cg-3, -5), 92.8 (CH2C CAre), 90.6 (C CArg), 89.0
ꢀ
ꢀ
ꢀ
ꢀ
(CH2C CArd), 87.6 (ArbC C), 83.4 (C CH), 80.4, 80.2 (CH2C C), 78.4
ꢀ
(C CH), 72.4 (ArdOCH2), 68.1 (ArgOCH2), 60.9 (CO2CH2), 30.4 28.7
(11 signals), 26.1, 26.0, 19.5, 19.4 (CH2), 16.1 (ArCH3), 14.4 (CH2CH3);
elemental analysis calcd (%) for C169H234O7 (2377.724): C 85.37, H 9.92;
found: C 85.26, H 9.92.
Gigantocycle 17: A suspension of CuCl (5.00 g, 50.5 mmol) and CuCl2
(678 mg, 5.00 mmol) in pyridine (500 mL) was prepared as described for
the preparation of 9b. To this suspension, a solution of ring precursor 16
(1.20 g, 0.50 mmol) in 1,2-dichlorobenzene (120 mL) was added within
62.4 h by means of a syringe pump. It was necessary to gently heat the
solution of 16 to dissolve all of the starting material. Once in solution, 16
stays dissolved for at least 20 h. After the addition was complete, the
reaction mixture was stirred for additional 3 d. Workup as described for 9b
gave a solution of 16 in 1,2-dichlorobenzene. Most of the 1,2-dichloroben-
zene was distilled off (508C bath temp, 0.05 mbar) and the residue was
dissolved in CH2Cl2 (30 mL). This solution was added dropwise to ethanol
(130 mL). The colorless precipitate was isolated and washed with ethanol.
Flash chromatography (petroleum ether/CH2Cl2 1:1 v/v; Rf ˆ 0.37) gave 16
(961 mg, 80%) as a pale yellow solid. Thermal characterization: see text;
1H NMR d ˆ 8.00 (s, 2H, Ha), 7.62, 7.54 (AA'XX', 4H each, Hb), 7.47 (half
of AA'XX', 4H, Hg-2, -6), 7.41, 7.32 (AA'XX', 4H each, CHe), 7.05 (s, 4H,
ArHd), 6.87 (half of AA'XX', 4H, Hg-3, -5), 5.75 (s, 1H, OH), 4.38 (q, J ˆ
7.1 Hz, 2H, CO2CH2), 3.97 (t, J ˆ 6.5 Hz, 4H, ArgOCH2), 3.71 (t, J ˆ 6.6 Hz,
ꢀ
(CH2)11-C C-TMS is obtained in ca. 80% yield. After removal of
ꢀ
the TMS groups, HO-(CH2)11-C C-H can be used as alkynol 3 for the
ꢀ À ꢀ
coupling with 19, albeit a distinct amount of HO-(CH2)11-C C C C-
(CH2)11-OH will be also formed.
[18] Procedure based on S. R. Abrams, Can. J. Chem. 1984, 62, 1333; S. R.
Abrams, A. C. Shaw, M. Taddei, I. Fleming, Org. Syn. 1987, 66, 127.
[19] Estimated from 1H NMR spectra using the signal of the CH2O group
(d ˆ 3.62) of 3 and that of the CH3 group (d ˆ0.86) of the by-product.
[20] S. R. Macaulay, J. Org. Chem. 1980, 45, 734; S. R. Macaulay, Can. J.
Chem. 1980, 58, 2567.
ꢀ
4H, ArdOCH2), 3.12 (s, 2H,C CH), 2.40, 2.36 (2t, J ˆ 7.0 Hz, 4H each,
ꢀ
CH2C C), 2.21 (s, 12H, ArCH3), 1.76 (m, 8H, OCH2CH2), 1.56 (m, 8H,
ꢀ
CH2CH2C C), 1.39 (t, J ˆ 7.1 Hz, 3H, CH2CH3), 1.5 1.2 (m, 152H, CH2);
13C NMR: d ˆ 166.1 (CO2), 159.4 (Cg-4), 155.8 (Cd-4), 153.2 (Ca-4), 135.9
(Cb-1), 133.1 (Cg-2, -6), 132.3 (CHe), 132.0 (Cb-3, -5, CHd), 131.6 (Ca-2, -6),
131.4 (CHe), 130.9 (Cd-3, -5), 129.3 (Cb-2, -6), 128.3 (Ca-3, -5), 125.2 (Ce-1 or
[21] The reaction of NaH with diaminopropane at 758C gave a brown
turbid solution with silvery balls, probably metallic sodium. The latter
Chem. Eur. J. 2002, 8, No. 22
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5105

A. Godt et al.
FULL PAPER
may explain the reduction of the triple bond. However, it remains a
mystery how sodium could be formed, and what happened to the
hydroxyl functionality. None of these observations have been
mentioned in the numerous papers that we know of reporting on
this method of alkyne isomerization.
V. Enkelmann, Angew. Chem. 1995, 107, 2917; Angew. Chem. Int. Ed.
1995, 34, 2713; S. Hˆger, A.-D. Meckenstock, Chem. Eur. J. 1999, 5,
1686; J. J. Pak, T. J. R. Weakley, M. M. Haley, J. Am. Chem. Soc. 1999,
121, 8182; A. de Meijere, S. I. Kozhushkov, Top. Curr. Chem. 1999,
201, 1; F. Diederich, L. Gobbi, Top. Curr. Chem. 1999, 201, 43; M. M.
Haley, J. J. Pak, S. C. Brand, Top. Curr. Chem. 1999, 201, 81; U. H. F.
Bunz, Top. Curr. Chem. 1999, 201, 131; H. L. Anderson, J. K. M.
Sanders, Angew. Chem. 1990, 102, 1478; Angew. Chem. Int. Ed. 1990,
29, 1400; R. Berscheid, M. Nieger, F. Vˆgtle, Chem. Ber. 1992, 125,
2539; M. Ohkita, K. Ando, T. Suzuki, T. Tsuji, J. Org. Chem. 2000, 65,
4385; A. de Meijere, S. Kozhushkov, T. Haumann, R. Boese, C. Puls,
M. J. Cooney, L. T. Scott, Chem. Eur. J. 1995, 1, 124.
[22] J. C. Lindhoudt, G. L. van Mourik, H. J. J. Pabon, Tetrahedron Lett.
1976, 2565; C. A. Brown, A. Yamashita, J. Chem. Soc. Chem.
Commun. 1976, 659; C. A. Brown, A. Yamashita, J. Am. Chem. Soc.
1975, 97, 891.
[23] H. Hommes, L. Brandsma, Recl. Trav. Chim. Pays-Bas 1977, 96, 160.
[24] d ˆ 5.08 (quint., J ˆ 6.8 Hz, ), 4.63 (m with 5 lines in the intensity of ca.
1:2:2:2:1 with a spacing of ca. 3.2 Hz), 1.77 (t, J ˆ 2.4 Hz). The
approximate relative intensity of these signals is 4:7:7. The concrete
structural formula of this enyne is not yet known to us.
[31] F. M. Menger, S. Brocchini, X. Cheng, Angew. Chem. 1992, 104, 1542;
Angew. Chem. Int. Engl. Ed. 1992, 29, 1400; F. M. Menger, X. Y. Chen,
S. Brocchini, H. P. Hopkins, D. Hamilton, J. Am. Chem. Soc. 1993, 115,
6600. The term ™gigantocycle∫ was introduced for cycles with more
than 50 ring atoms. See also ref. [8].
[32] G. Schill, C. Z¸rcher, H. Fritz, Chem. Ber. 1978, 111, 2901; K. S. Lee, G.
Wegner, Macromol. Chem. Rapid Commun. 1985, 6, 203; A. P.
Patwardhan, D. H. Thompson, Org. Lett. 1999, 1, 241; M. Ladika,
T. E. Fisk, W. Wu, S. D. Jones, J. Am. Chem. Soc. 1994, 116, 12093.
[33] F. Vˆgtle, I. Michel, R. Berscheid, M. Nieger, K. Rissanen, S. Kotila,
K. Airola, N. Armaroli, M. Maestri, V. Balzani, Liebigs Ann. 1996,
1697.
[34] R. E. Martin, T. M‰der, F. Diederich, Angew. Chem. 1999, 38, 817;
A. M. Boldi, F. Diederich, Angew. Chem. 1994, 106, 482; Angew.
Chem. Int. Ed. Engl. 1994, 33, 468.
[35] Analogous to D. O×Krongly, S. R. Denmeade, M. Y. Chiang, R.
Breslow, J. Am. Chem. Soc. 1985, 107, 5544 , rigorous exclusion of
oxygen turned out to not be necessary; solvents were not degassed.
[36] A. S. Hay, J. Org. Chem. 1962, 27, 3320.
[37] F. Bohlmann, H. Schˆnowsky, E. Inhoffen, G. Grau, Chem. Ber. 1964,
97, 794.
[38] D. Demus in Handbook of Liquid Crystals, Vol. 1 (Eds.: D. Demus, J.
Goodby, G. W. Gray, H.-W. Spiess, V. Vill), Wiley-VCH, Weinheim,
1998, p. 133.
[39] T. Hegmann, J. Kain, S. Diele, G. Pelzl and C. Tschierske, Angew.
Chem. 2001, 113, 911; Angew. Chem. Int. Ed. 2001, 40, 887.
[40] A. J. Slaney, K. Takatoh, J. W. Goodby in The Optics of Thermotropic
Liquid Crystals (Eds.: S. Elston, R. Sambles), Taylor & Francis,
London, 1998, p. 307.
[41] T. Niori, F. Sekine, J. Watanabe, T. Furukawa, H. Takezoe, J. Mater.
Chem. 1996, 6, 1231; D. R. Link, G. Natale, R. Shao, J. E. Maclennan,
N. A. Clark, E. Kˆrblova, D. M. Walba, Science 1997, 278, 1924; G.
Pelzl, S. Diele, W. Weissflog, Adv. Mater. 1999, 11, 707.
[42] B. Langer, I. Schnell, A. Godt, H. W. Spiess, unpublished results; ÷.
‹nsal, A. Godt, Chem. Eur. J. 1999, 5, 1728.
[43] R. F. Heck, Palladium Reagents in Organic Syntheses, 1985, Academic
Press, p. 18.
[44] H. Kukula, S. Veit, A. Godt, Eur. J. Org. Chem. 1999, 277.
[45] The 1H NMR spectra of all batches show a triplet at 3.35 ppm of very
low intensity (ca. 1 3%; estimated from a comparison with the
intensity of the 13C satellite of the triplet of CH2O of product 2).
[46] The complete rearrangement was proven by 1H NMR spectroscopy. A
longer reaction time, such as 38 h, does not diminish the yield.
[47] Changing the solvent for chromatography from petroleum ether
directly to petroleum ether/diethyl ether results in extensive tailing of
the product.
[48] Jork, Funk, Fischer, Wimmer, D¸nnschicht-Chromatographie, Vol. 1,
VCH, 1989, p. 191.
[49] S. Okada, H. Matsuda, M. Otsuka, N. Kikuchi, K. Hayamizu, H.
Nakanishi, M. Kato, Bull. Chem. Soc. Jpn. 1994, 67, 455.
[50] Assignment according to 13C-NMR-Spektroskopie, H.-O. Kalinowski,
S. Berger, S. Braun, 1984, Thieme, Stuttgart.
[25] O. Mitsunobu, Synthesis 1981, 1.
[26] Independently of the concise protecting group, the coupling products
18 were accompanied by the disubstitution product 1,4-bis(trialkylsi-
lylethynyl)benzene as can be clearly seen from 1H NMR spectra
[d(ArH) ˆ 7.38 in CDCl3]. For identification, bis(trimethylsilylethy-
nyl)benzene was isolated as the second fraction of
a column
chromatography (SiO2/petroleum ether) of the crude product of the
coupling reaction with trimethylsilylethyne. However, separation of
1,4-bis(trialkylsilylethynyl)benzene from 18 or 19 is not necessary.
This by-product was easily removed from the coupling products 4a, b
as a common chromatographic fraction with the excessive 19.
[27] a) The existence of by-product 20b in samples of 18b was proven
indirectly as described below through the proof of 4-iodo-4'-(trime-
thylsilylethynyl)tolane (21b) as a contaminant in 19b because the
1H NMR signals of 20b are covered by those of 18b. Attempts to
prove 20b as a by-product through mass spectrometry (FD-MS and
EI-MS) failed. The 1H NMR spectrum of compound 19b shows a
somewhat broad singlet of low intensity at 7.43 ppm, see ref. [27c].
The intensity of this singlet relative to the signals of the main
compound 19b varied from batch to batch. This singlet also appeared
in the spectra of the products of the following synthetic steps, namely
4a, b(TMS) and 5a, b(TMS), (that is 4a, b and 5a, b with a TMS
instead of a TIPS protecting group). In the 1H NMR spectra of the
products 7a, b(TMS) and 8a, b (the latter derived from 7a, b(TMS))
this signal appears very close to the signals of the main compound and
can therefore only been seen when it is of sufficient intensity. No other
additional signals of these by-products could be detected in the NMR
spectra. Therefore, and because of the fact that the by-product present
in a sample of 19b reacted with the alkynols 3 or 11 giving again a
product which differs from the main product 4a(TMS) or 4b(TMS)
only by the singlet at 7.43 ppm, the minor component in a sample of
19b must be structurally similar to 19b. An explanation that fits all of
our data is that 19b contained 21b. This compound could have formed
only from the corresponding bromo compound 20b, which conse-
quently must be assumed to be a side product of the coupling reaction
of 1-bromo-4-iodobenzene with trimethylsilylethyne. The formation
of 20b means that (4-bromophenyl)ethyne was formed in situ and
reacted with 18b to give 20b. However, (4-bromophenyl)ethyne was
never detected by 1H NMR spectroscopy in the crude or purified
samples of 18b. This may be due to rapid oxidative dimerization upon
workup as discussed in ref. 44; b) FD-MS spectra of 5(TMS) 7(TMS)
‡
and of 8 and 9 derived from 7(TMS) reveal signals of [M‡100] ; c) the
broadened singlet at 7.43 ppm is attributed to the four protons at the
benzene ring carrying two ethyne substituents. This is in agreement
with the data of ref. [28] and a comparison with a sample of pure 20b
which was obtained through Pd/Cu-catalyzed coupling of 4-bromo-
phenylethyne with 1-iodo-4-(trimethylsilylethynyl)benzene.
[28] R. P. Hsung, C. E. D. Chidsey, L. R. Sita, Organometallics 1995, 14,
4808.
[29] P. Siemens, R. C. Livingston, F. Diederich, Angew. Chem. 2000, 112,
2740; Angew. Chem. Int. Ed. 2000, 39, 2632.
Received: January 14, 2002
Revised: July 1, 2002 [F3799]
[30] For example: Y. Tobe, N. Utsumi, A. Nagano, K. Naemura, Angew.
Chem. 1998, 110, 1347; Angew. Chem. Int. Ed. 1998, 37, 1285; S. Hˆger,
5106
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