Columnar Propeller-Like 1,3,5-Triphenylbenzenes: Probing the Effect of Chlorine on the Suzuki Cross-Coupling and Liquid Crystalline Properties

Article abstract of DOI:10.1002/ejoc.201901827

Suzuki cross-couplings either between chlorinated N-methyliminodiacetic acid (MIDA)-protected aryl boronates and 1,3,5-tribromobenzene or between chlorinated aryl bromides and phenyltrisboronic species to star-shaped 1,3,5-triphenylbenzenes with different substitution patterns and chloro substituents at the outer phenyl rings were studied. The chlorinated precursors required for the respective reaction were synthesized and characterized. Depending on the used coupling reaction target triphenylbenzenes were isolated in yields between 42 % and 88 %. Their mesomorphic properties were influenced by the substitution pattern and number of peripheral chlorine atoms. Triphenylbenzene with 3,5-alkoxy substitution and H in para-position self-assembled into either columnar hexagonal (Col_h) mesophases or a soft crystal. While threefold chloro substitution in meta-position of the outer phenyl rings led to stable room temperature Col_ho phases, triphenylbenzenes with threefold para-chloro or 3,5-dichloro substitution were non-mesomorphic. Based on X-ray diffraction data a helical packing model for the observed phases similar to that of related alkoxy-substituted triphenylbenzenes was proposed.

Full text of DOI:10.1002/ejoc.201901827

A Journal of
Accepted Article
Title: Columnar Propeller-like 1,3,5-Triphenylbenzenes: Probing the
Effect of Chlorine on the Suzuki Cross Coupling and Liquid
Crystalline Properties
Authors: Marco André Grunwald, Tobias Wöhrle, Robert Forschner,
Angelika Baro, and Sabine Laschat
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10.1002/ejoc.201901827
European Journal of Organic Chemistry
Columnar Propeller-like 1,3,5-Triphenylbenzenes: Probing the Effect of
Chlorine on the Suzuki Cross Coupling and Liquid Crystalline Properties
Marco André Grunwald,[a] Tobias Wöhrle,[a] Robert Forschner,[a] Angelika Baro,[a] and Sabine
Laschat*[a]
Abstract: Suzuki cross couplings either between chlorinated N-methyliminodiacetic acid
(MIDA)-protected aryl boronates and 1,3,5-tribromobenzene or between chlorinated aryl
bromides and phenyltrisboronic species to star-shaped 1,3,5-triphenylbenzenes with different
substitution patterns and chloro substituents at the outer phenyl rings were studied. The
chlorinated precursors required for the respective reaction were synthesized and characterized.
Depending on the used coupling reaction target triphenylbenzenes were isolated in yields
between 42% and 88%. Their mesomorphic properties were influenced by the substitution
pattern and number of peripheral chlorine atoms. Triphenylbenzene with 3,5-alkoxy
substitution and H in para-position self-assembled into either columnar hexagonal (Colh)
mesophases or a soft crystal. While threefold chloro substitution in meta-position of the outer
phenyl rings led to stable room temperature Colho phases, triphenylbenzenes with threefold
para-chloro or 3,5-dichloro substitution were non-mesomorphic. Based on X-ray diffraction
data a helical packing model for the observed phases similar to that of related alkoxy-
substituted triphenylbenzenes was proposed.
Keywords: cross coupling  triphenylbenzenes  liquid crystals  MIDA-boronates 
mesophases
Key Topic: Cross Coupling
[a] M.Sc. M. A. Grunwald, Dr. T. Wöhrle, M.Sc. R. Forschner, Dr. A. Baro, Prof. S. Laschat
Institut für Organische Chemie, Universität Stuttgart,
Pfaffenwaldring 55, D-70569 Stuttgart, Germany
E-mail: sabine.laschat@oc.uni-stuttgart.de
https://www.ioc.uni-stuttgart.de/en/research/ak-laschat/
 Supporting information and ORCID from the authors for this article are available on the
iD WWW under
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Introduction
The archetypal discotic liquid crystal contains a central rigid aromatic or heteroaromatic core
surrounded by peripheral flexible chains, which self-assembles into columnar mesophases due
to  interactions of the core, while the chains stabilize the columnar phase through van der
Waals interactions and suppress crystallization due to their flexibility.[1,2] These self-
assembled structures are interesting because their 1D charge carrier mobility and self-healing
of defects make them suitable for molecular electronics applications.[3,4] However, long
alkoxy side chains can cause synthetic challenges (e.g., purification and solubility) and
furthermore, limit applications by clearing points close to the thermal decomposition
temperature.[5,6] Thus, discotic liquid crystals where peripheral alkoxy chains have been
replaced by some surrogate would be highly attractive. In a groundbreaking work Ros and
Torroba demonstrated that small aromatic and heterocyclic compounds 1–3 devoid of any
alkoxy groups, but carrying polarizable chlorine atoms form stable columnar mesophases
(Scheme 1).[7,8] In addition, a beneficial effect of chloro (or fluoro) substituents on the
mesomorphic properties and a decrease of phase transition temperatures were independently
reported for bent core liquid crystals by Twieg[9,10] and for ionic liquid crystals by Binne-
mans.[11]
Scheme 1. Selected liquid crystalline pseudoazulenes (1, 2) and indene derivative 3.[7,8]
Star-shaped 1,3,5-triphenylbenzenes such as 4 (Scheme 2) belong to the class of shape-
persistent hekates which are able to form columnar mesophases.[12–15] Space-filling between
the three arms are achieved either by helical twisting along the columnar axis, or by
incorporation of bulky guest molecules covalently or non-covalently bound to the star, giving
rise to unique self-assembled structures.[5,16–20]
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Scheme 2.
In previous work on tris(trialkoxyphenyl)benzenes 4 the methoxy group was reported to serve
as a minimalistic alkoxy unit at the outer phenyl rings, resulting in decreased clearing
temperature while keeping the stable columnar mesophase.[5] Motivated by this observation
we surmised that omission or successive replacement of alkoxy side chains by chloro
substituents might affect the phase behaviour in a similar fashion. Furthermore, the relevance
of van der Waals interactions vs. halogen bonding and dipolar interactions on the self-
assembly and the resulting phase transitions temperatures could be elucidated. To study the
effects in more detail, convenient synthetic access to (poly)chlorinated triphenylbenzenes 5 is
required. In contrast to the plethora of well-explored Suzuki-Miyaura cross coupling of aryl
halides with aryl boron species,[21–25] the use of di- and poly-chlorinated reactants has been
mostly devoted to access polychlorinated biphenyl (PCB) derivatives for ecotoxicity and
analytical property studies.[26–33] In order to get access to triphenylbenzenes 5 we followed
two synthetic strategies involving a cross coupling as key step (Scheme 3). Compound 5 is
derived either from Suzuki-Miyaura cross coupling between aryl boronic species 6 (e.g., N-
methyliminodiacetic acid (MIDA) boronates[34–39]) and 1,3,5-tribromobenzene 7 (route A) or
alternatively, by the connection of aryl bromides 8 and 1,3,5-phenyltrisboronic species 9 (e.g.,
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pinacole boronate) (route B). The results towards the synthesis of compounds 5 and study of
their mesomorphic properties are reported below.
Scheme 3. Retrosynthetic pathways to star-shaped triphenylbenzenes 5.
Results and Discussion
Synthesis of Star-Shaped Triphenylbenzene Derivatives
The synthesis of precursor MIDA-protected aryl boronates 6 for Suzuki-Miyaura cross
coupling[40,41] according to route A and aryl bromides 8 is depicted in Scheme 4. Williamson
etherification of 5-bromo-3-hydroxyphenol 11a[42] with bromododecane in the presence of
K2CO3 gave aryl bromide 8a in 63% yield (Scheme 4).[43] Subsequent treatment with n-BuLi
in THF at –78 °C, triisopropyl borate and finally N-methyliminodiacetic acid (MIDA) accord-
ing to literature procedures[37,44] yielded boronate 6a in 63%. Dakin oxidation of 5-bromo-3-
chloro-2-hydroxybenzaldehyde 12[36] gave bromide 11c quantitatively, which was etherified
with bromododecane to yield bromide 8c. Conversion of 8c under the conditions described
above for 8a afforded MIDA boronate 6c in 28% overall yield. Williamson etherification of
4-bromo-2,6-dichlorophenol 11d[27] with bromododecane yielded aryl bromide 8d in 98%. Its
conversion into MIDA boronate 6d proceeded in 81% without any event.
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European Journal of Organic Chemistry
Scheme 4. Synthesis of precursors 6 and 8 (numbering for NMR assignment; for details see
also the Supporting Information).
The preparation of the para-chloro-substituted aryl bromide 8b commenced with a nucleo-
philic displacement of 3-bromo-2-chloro-1,3-difluorobenzene 10 using NaOMe in dimethyl-
acetamide. Demethylation of the resulting 5-bromo-2-chloro-1,3-dimethoxybenzene with
BBr3 and subsequent Williamson etherification afforded bromide 8b in 90% over 2 steps.
We next studied the Suzuki-Miyaura coupling reaction following route A (Scheme 5).[37,45]
Treatment of aryl MIDA boronate 6a (3 equivalents) with 1 M NaOH in THF at room
temperature for 15 min removed the MIDA group. To the resulting free boronic acid were
immediately added 1,3,5-tribromobenzene 7 (1 equivalent) in the presence of Pd(PPh3)4
(6 mol%) and K2CO3 (4.5 equivalents) in DMF / H2O, and the reaction mixture was stirred at
90 °C for 24 h. After workup and chromatographic purification, the desired star-shaped
compound 5a was isolated in 75% yield. Under these reaction conditions chlorinated MIDA
boronates 6c,d were coupled with 7 to the corresponding triarylbenzenes 5c,d which were
isolated in 57 and 42% yield, respectively (Scheme 5). Owing to decrease of yield we were
worried that the chloro substituent might interfere with Pd-catalyzed cross coupling, because
the Suzuki-Miyaura reaction was planned as a key step in both routes A and B. While the
higher bonding dissociation enthalpy of the C–Cl bond as compared to the C–Br bond should
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favor participation of the latter in the oxidative addition step of the Suzuki-Miyaura
reaction,[21–25,46–49] examples of competitive participation of C–Cl bonds are known.[46–49] In
the presence of suitable catalysts the reactivity of aryl chlorides was not only increased,[50–52]
but in some cases it even exceeded that of the corresponding aryl bromides.[46–49] Therefore,
to improve the yield and prevent multiple borylation of star-shaped compound 5d, the Suzuki-
Miyaura coupling reaction via route B was studied (Scheme 5).
Scheme 5. Synthesis of the 1,3,5triphenylbenzenes 5 (numbering for NMR assignment).
Commercially available 1,3,5-tris(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzene 9 was
reacted with 3,5-dichlorinated aryl bromide 8d in the presence of 6.5 mol% of Pd(PPh3)4
under otherwise identical conditions to provide the desired triarylbenzene 5d in 88% yield.
Analogously, the Suzuki-Miyaura cross coupling between borolane 9 and aryl bromide 8b
yielded 76% of the star-shaped triphenylbenzene derivative 5b, which is complementary to
compound 5a, i.e. carrying a chloro substituent rather than a H atom in the para-position
(Scheme 5). When comparing both routes, route B apparently is favoured against route A.
Obviously, when central borolane core 9 has fully reacted to the desired triphenylbenzene 5b
or 5d additional coupling reactions are unlikely.
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Mesomorphic properties of MIDA-boronates and triphenylbenzenes
Mesomorphic properties of triphenylbenzenes 5 as well as the MIDA-boronates 6 were
investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM)
and X-ray diffraction (WAXS, SAXS). The DSC results are summarized in Table 1 (for DSC
traces see Figures S3 and S4) and visualised in Figure 1.
During examination of precursors 6 by DSC and POM we noticed liquid crystalline behaviour
for MIDA boronate 6a,c,d which is in line with previous studies.[44]
Table 1. Phase transition temperatures [°C] and enthalpies H [kJ mol–1] of MIDA-boronates
6 and triphenylbenzenes 5 upon second heating (H) and cooling (C) (rate 5 K min–1).[a]
Phase
Compound Phase
Phase
Colh
Colh
Colh
Colh
SmA
SmA
Colho
Colho
–
T (H)
T (H)
119 (0.86)
118 (0.84)
141 (0.5)
140 (0.4)
198 (2.1)
197 (2.0)
49 (33.2)
40 (35.0)
–
Cr[b]
75
I
I
I
I
I
I
I
I
I
I
I
I
I
I
H
C
6a
Cr[b]
75
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr[e]
97 (39.1)
78 (2.1)
164 (10.9)
112 (6.2)
20 (59.7)
16 (68.3)
115 (50.0)
110 (47.9)
17 (16.8)
6 (25.9)
38 (18.6)
–78
H
6c
6d
5a
5b
5c
5d
C
H[c]
C[c]
H
C
H
–
–
C
Colho
Colho
–
89 (14.3)[d]
94 (16.8)[d]
–
H
C
H[f]
C[f]
–
–
[a] Without additional Cr–Cr transitions. The onset points of the heat flow peaks were used
for the determination of the corresponding transition temperature. Phases observed: Cr
crystalline; SmA smectic A; Colh columnar hexagonal; I isotropic; X unknown phase. [b]
Determined by POM. [c] First cycle. [d] Peak temperatures: 95 °C (H) and 91 °C (C). [e]
Glass transition (supercooled). [f] Heating/cooling rate 10 K min–1.
The DSC results for MIDA boronate 6c exhibit that one chloro substituent in the meta-
position led to a higher melting temperature of 97 °C, but lowered the mesophase-to-isotropic
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liquid transition to 141 °C in the heating scan relative to the transition temperatures of [3,4-
bis(dodecyloxy)phenyl]-MIDA boronate 13[44] (Figure 1, Table 1). Upon cooling the clearing
temperature is maintained while supercooling for the mesophase–Cr transition to 78 °C and
two further Cr–Cr transitions at 66 °C and 60 °C were observed. The chloro substituent seems
to decrease the crystallization temperature in a similar fashion as compared to flexible alkoxy
chains. Boronate 6d carrying lateral chlorine atoms in 3,5-position revealed increased melting
and clearing transitions upon heating (Table 1). In the cooling cycle the melting transition is
shifted to lower temperature and this supercooling is accompanied by glassy solidification of
the sample, which could already be seen under the POM due to the absence of crystallization.
These observations further strengthen the previous assumption that chlorine would counteract
crystallization. For [3,5-bis(dodecyloxy)phenyl]-MIDA-boronate 6a, a melting transition at
75 C° and a clearing temperature lower than that of the 3,4-disubstituted 13 were observed
(119 °C vs 169 °C) (Figure 1).
250
Cr
Colh
200
150
100
50
34
SmA
85
44
44
72
29
0
13
6a
6c
6d
4a
5a
5c
Figure 1. Mesophase widths of liquid crystalline MIDA-boronates 6 and star-shaped
triphenylbenzenes 5 obtained by DSC upon second heating (heating rate 5 K min–1). Data for
[3,4-bis(dodecyloxy)phenyl]-MIDA boronate 13 and 4a were taken from the literature.[5,44]
Under the POM, similar textures were found for mono-chlorinated 6c and 3,5-dialkoxy-
substituted boronate 6a (Figure 2a), which most likely hinted to Colh phases.[53] In contrast,
dichlorinated boronate 6d formed maltese cross textures indicating a SmA phase (Figure
2b).[53]
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Figure 2. Textures as seen between crossed polarizers. a) Focal conic texture of boronate 6a
with homeotropic areas at 118 °C (heating rate 2 K min–1), b) maltese crosses of boronate 6d
at 206 °C (heating rate 5 K min–1), c) uncharacteristic texture of 5a at 40 °C and d) pseudo-
focal conic texture with large areas of homeotropic alignment of triphenylbenzene derivative
5c at 80 °C (cooling rate 5 K min–1).
To further determine the phase geometry of the liquid crystalline boronates 6a,c,d, XRD
experiments were conducted (for characteristic diffraction profile see Supporting Informa-
tion). In the wide-angle X-ray scattering (WAXS) profile of 6a a diffuse halo at 4.8 Å in the
wide-angle region and a sharp (10) reflection in the small-angle regime are visible (Figure
S5a). Boronate 6c behaved similarly showing only the (10) reflection together with a broad
halo at 4.8 Å. Due to the lack of higher order reflections the phase geometry could not be
determined. Therefore, based on the characteristic textures and comparison with similar
derivatives,[44] Colh phases were assumed as well. In the case of boronate 6d, the WAXS
profile displayed a sharp (10) reflection and a diffuse halo (Figure S6a). Decreasing layer
distances with increasing temperatures (Figure S6b) as well as the texture confirmed the
proposed SmA phase.[54–56] Because of a similar structure and layer thickness as compared to
known MIDA-boronates,[44] a bilayer packing (SmAd) was suggested. However, due to
decreasing transition temperatures (and enthalpies) with increasing number of heating and
cooling cycles (Figure S3c), it could be assumed that the sample starts to decompose nearly
above its clearing point.
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Next, the triphenylbenzenes 5 were investigated. As can be seen from Table 1, only
derivatives 5a and 5c showed liquid crystallinity. Triphenylbenzenes 5b and 5d were devoid
of mesomorphism. The DSC curve of 3,5-dialkoxy-substituted derivative 5a showed melting
and clearing transitions at 20 °C and 49 °C upon heating and slightly supercooled transitions
at 16 °C and 40 °C upon cooling (Figure S4a). Under the POM, uncharacteristic focal conic-
like textures were observed (Figure 2c). Despite the relatively narrow phase width, the phase
behaviour of 5a contradicts the assumption that six-fold alkoxy-substituted hekates (e.g. 4a)
could not form any mesophases.[5,57,58] However, it becomes evident that phase formation is
associated with the (increasing) number of alkoxy substituents, but also with a suitable
substitution pattern (symmetry) on the outer phenyl rings. The small-angle X-ray scattering
profile of the mesophase of 5a revealed a set of reflections in the ratio 1 : 1/√3 : 1/√7 : 1/√9
indexed as (10), (11), (21), and (30) which are characteristic of a Colh phase with p6mm
symmetry (Figure 3b).[2,59]
Figure 3. a) WAXS profile and diffraction pattern (inset) and b) SAXS diffraction profile of
triphenylbenzene 5a at 40 °C.
In the WAXS a sharp (10) reflection as well as a broad halo at 4.5 Å and a – reflex at
4.0 Å are visible (Figure 3a). Moreover, triphenylbenzene 5a showed a helical orientation in
the WAXS diffraction pattern (Figure 4c), which resembled the helical stacking model
proposed for derivatives 4b and 4c.[5] Data evaluation using the HELIX[60] program resulted
in an azimuthal rotation angle φ = 60°, pitch p = 8.1 Å, repeat of three pitches C = 24.2 Å, –
 distance between two molecules d = 4.0 Å. The lattice parameter a of 5a (26.6 Å) is smaller
than the values of 4b (28.4 Å) and 4c (31.8 Å),[5] since the backfolding and interdigitation of
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the remaining alkoxy chains must be much stronger to fill the large void space due to the loss
of a substituent. The hexagonal packing becomes denser and the lattice parameter decreases.
Alternatively, a helical soft crystal or conformationally disordered (CONDIS) crystal phase[61]
might be proposed based on the high clearing enthalpy, the rather high hysteresis, the number
of very small reflections on the halo of the XRD pattern together with the uncharacteristic
texture.[62–64] However, the fact that compound 5a could be sheared under the POM agreed
with the assignment of a hexagonal columnar phase Colho with helical order along the
columnar axis. In addition, it should be noted that the high clearing enthalpies (in comparison
with the corresponding melting enthalpies) have previously been observed for related
triphenylbenzenes with Colho phases (see DSC curves in the Supporting Information of ref.[5]
as well as chlorinated heterocycles[7]).
Figure 4. a) WAXS pattern of 4c upon heating at 90 °C, b) a simulated WAXS pattern of 4c
(HELIX[60] program, φ = 60°, d = 4.3 Å) (both taken from the literature)[5] and c) WAXS
pattern of 5a upon heating at 40 °C.
In contrast to non-mesomorphic 3,4-disubstituted compound 4a (Scheme 2) which melts at
64 °C,[5] the 5-chloro-3,4-dialkoxy-substituted analogue 5c showed melting and clearing
transitions at 17 °C and 89 °C, respectively, upon heating and a slightly supercooled melting
transition at 6 °C upon cooling (Table 1). Homeotropic areas with pseudo-focal conic defects
visible under the POM (Figure 2d) indicated a columnar phase.[65] Obviously, a chloro
substituent in meta-position is sufficient for mesomorphism. However, the spherical chlorine
atom fills less space than a flexible alkoxy chain and seems to inhibit crystallization and thus
solid state packing. In the SAXS diffraction profile of 5c three characteristic reflections in the
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ratio 1 : 1/√3 : 1/√7 indexed as (10), (11) and (21) were detected, which are in agreement with
a Colh phase (Figure S8b). In contrast to its methoxy-substituted analogue 4b,
triphenylbenzene 5c did not show a helical orientation in the WAXS pattern. However, based
on a related molecular structure to 4b,c as well as phase behaviour a helical stacking model
seems likely. The lattice parameter of 5c (a = 29.3 Å) ranged between 4b (28.4 Å) and 4c
(31.8 Å),[5] which suggests that the chloro substituent might take more space than the
methoxy substituent. The necessary backfolding and interdigitation processes are
correspondingly lower.
Triphenylbenzenes 5b and 5d showed only melting transitions at 115 °C and 38 °C,
respectively, in the heating cycle (Table 1). Additionally, in the case of 3,5-dichloro-4-
dodecyloxy-substituted triphenylbenzene 5d, a cold crystallization was observed. In the
cooling cycle, 5d solidified like glass, however, upon reheating the sample crystallized. Upon
further heating, the sample returned to the isotropic liquid when reaching the melting point.
This phenomenon was already described by Illers for amorphous polymers.[66,67] The number
of chloro substituents in 5d seems to suppress completely the crystallization or self-assembly
into a liquid crystalline phase in general. The three alkoxy chains in the molecule can hardly
fill the empty space and thus, packing is no longer favoured. The increased inhibition of
crystallization and the low melting point could also be explained by this effect.
The strikingly different behaviour of triphenylbenzenes 5 might be rationalized as follows.
Introduction of one chloro substituent in the 3-position while maintaining an unsymmetric
substitution pattern around the central aromatic core decreased the melting transition and
stabilized the columnar phase in 5c as compared to non-mesogenic 4a. In contrast,
introduction of a polarizable chlorine atom in the 4-position kept the overall C3-symmetry but
led to a much higher melting point as compared to 5c, indicating strong intermolecular dipolar
and halogen interactions and this preventing mesophase formation for 5b in contrast to non-
chlorinated counterpart 5a. In the case of 5d, the presence of an additional chloro substituent
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decreased the melting transition. However, the 3,5-dichloro substitution maintains
C3-symmetry and the presence of two polar substituents leads to strong intermolecular
interactions suppressing mesophase formation. Furthermore, only three alkoxy chains seem to
be insufficient to fill the space and thus disfavouring both crystalline and mesophase packing.
These results show that mesomorphism in such star-shaped molecules is based on a delicate
balance of intermolecular interactions involving the aromatic core and its – stacking and
helical twisting of the propeller-shaped core in order to fill the void space as well as
symmetry and number of polar or polarizable groups in the periphery. Our observations are in
good agreement with detailed structure-property relationships disclosed by Ros on
halogenated indenes and pseudoazulenes.[7]
Conclusion
A convenient access to chloro-substituted triphenylbenzene hekates was established using
Suzuki-Miyaura cross coupling as the key step. If tris(tridodecyloxyphenyl)benzene 4c[5] is
considered as a benchmark columnar mesogen, removal of one dodecyloxy chain from each
phenyl unit resulted in loss of mesomorphism for 4a.[5] If the missing third dodecyloxy chain
was replaced by a methoxy group as in 4b, both melting and clearing points decreased, while
the Colho mesophase was maintained.[5] This effect was even more pronounced, if the missing
dodecyloxy chain was replaced by chloro, resulting in star-shaped compound 5c with a room
temperature Colho phase. When only two dodecyloxy chains in the 3,5-position were left as in
5a, again both melting and clearing points decreased considerably and 5a arranged in a Colho
phase or soft crystal albeit with small phase width. Accordingly, the meta-position seems to
play a greater role in mesophase stabilization than the para-position. Furthermore, if at least
one chloro substituent was involved, tendency to crystallization was, depending on the
substitution pattern, significantly reduced. The mesophase was also completely destabilized
by onefold para- or twofold meta-chloro-substituted phenyl rings. In agreement with previous
work by Twieg and Binnemans our results reveal that chloro substituents indeed lower phase
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transitions, however, with regard to the replacement of alkoxy side chains there is no easy
rule of thumb available and thus, further work on other discotics is required.
Experimental Section
General. All chemicals were used as purchased. Anhydrous solvents were distilled and dried
under nitrogen atmosphere, solvents for chromatography were distilled prior to use. 5-
Bromobenzene-1,2-diol (11a),[42] 4-bromo-2,6-dichlorophenol (11d),[27] and 5-bromo-3-chlo-
ro-2-hydroxybenzaldehyde (12)[36] were synthesized following the literature. NMR spectra
were recorded on Bruker Avance 400, 500 or 700 MHz instruments. All chemical shifts ()
are given in ppm and are referenced to CDCl3 with tetramethylsilane as an internal standard
unless otherwise stated. IR spectra were recorded on a Bruker Vektor 22 or ALPHA
instrument equipped with a MKII Golden Gate Single Reflection Diamond ATR. MS and
HRMS were measured on a Bruker micro-TOF-Q spectrometer with electrospray ionisation
(ESI) or atmospheric pressure chemical ionization (APCI), or on a Finnigan Varian MAT95
spectrometer with electron ionisation (EI). GC-MS was performed on an Agilent Technolo-
gies 6890N Network GC system equipped with an Agilent 5973 Network Mass Selective
Detector. An Olympus BX50 combined with a Linkam TP93 central controller was used for
polarizing optical microscopy (POM). Differential scanning calorimetry (DSC) was carried
out on a Mettler Toledo DSC822e and X-ray diffraction (XRD) measurements on a Bruker
AXS Nanostar C with ceramic tube generator (1500 W) and cross-coupled Goebel mirrors
(monochromatic CuK,α1 radiation, 1.5405 Å). Diffraction patterns were measured with a
Bruker HI-STAR detector and were calibrated using a diffraction pattern of silver behenate at
room temperature. The diffraction patterns were analyzed with Datasqueeze and Origin.
5-Bromo-2-chlorobenzene-1,3-diol (11b): To a solution of 5-bromo-2-chloro-1,3-dimeth-
oxybenzene (503 mg, 2.00 mmol) in dry CH2Cl2 (30 mL) under nitrogen atmosphere at
–78 °C a 1 M solution of boron tribromide in CH2Cl2 (4.6 mL, 4.60 mmol) was added slowly.
14
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After warming to room temperature, the reaction mixture was stirred for 17 h. Additional
BBr3 (in total 15.4 mL, 15.4 mmol) was added over 14 d because of incomplete conversion
(TLC control). The reaction was terminated by addition of ice-cold H2O (25 mL). After phase
separation, the aqueous phase was extracted with Et2O (5 × 25 mL). The combined organic
layers were dried (MgSO4), and the solvent was removed under reduced pressure. The residue
was dried under reduced pressure for 2 d to give 11b (463 mg, 2.07 mmol, quant., purity
1
>95%) as white needles, which were used without further purification. H NMR (400 MHz,
[D6]DMSO): δ=6.59 (s, 2H; 2×2-H), 10.42 ppm (s, 2H; 2×OH); 13C NMR (101 MHz,
[D6]DMSO): δ=107.4 (C-4), 110.2 (C-2), 119.3 (C-1), 155.7 ppm (C-3); MS (GC-MS):
m/z = 224 [M].
5-Bromo-3-chlorobenzene-1,2-diol (11c): To a suspension of 5-bromo-3-chloro-2-hydroxy-
benzaldehyde 12[36] (2.50 g, 10.6 mmol) in aqueous NaOH (0.45 g, 11.2 mmol, 1.3 M) H2O2
(1.2 mL, 11.2 mmol, 9.8 M in H2O) was added, and the suspension was stirred for 1 h at room
temperature. The mixture was then poured into H2O (30 mL), acidified with conc. H2SO4 and
extracted with CH2Cl2 (600 mL). The organic layer was washed with brine (250 mL), and the
solvent was removed under reduced pressure. The brown and oily residue was used without
further purification and characterization.
1-Bromo-3,5-bis(dodecyloxy)benzene (8a): In analogy to ref.,[43] a solution of 5-bromo-3-
hydroxyphenol 11a (1.20 g, 6.35 mmol) in DMF (50 mL) was degassed for 20 min by a
constant nitrogen flow. K2CO3 (5.30 g, 38.1 mmol) and bromododecane (3.4 mL, 14.0 mmol)
were added, and the suspension was stirred at 80 °C overnight under a nitrogen atmosphere.
The mixture was then poured into an aqueous solution of NaOH (150 mL, 1 M), and the
aqueous layer was extracted with Et2O (200 mL). The organic layer was washed with water
(100 mL), dried (MgSO4), and the solvent was removed under reduced pressure. The residue
was purified by chromatography on SiO2 with hexanes to give 8a (2.10 g, 3.99 mmol, 63%,
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1
purity >95%) as a white solid. M.p. 32.2 °C; Rf=0.6 (hexanes/EtOAc 50:1); H NMR (400
MHz, CDCl3): δ=0.83–0.93 (m, 6H; 3×CH3), 1.18–1.51 (m, 36H; 18×CH2), 1.68–1.82 (m,
4H; 2×OCH2CH2), 3.83–3.93 (m, 4H; 2×OCH2), 6.36 (t, J = 2.2 Hz, 1H; 2-H), 6.63 ppm (d, J
13
= 2.2 Hz, 2H; 4-H, 6-H); C NMR (101 MHz, CDCl3): δ=14.1 (CH3), 22.7, 26.9, 29.1, 29.4,
29.58, 29.61, 29.66, 29.68, 31.9 (CH2), 68.3 (OCH2), 100.5 (C-2), 110.2 (C-4, C-6), 122.8 (C-
5), 160.7 ppm (C-1, C-3). The spectroscopic data are in accordance with the literature.[43]
5-Bromo-2-chloro-1,3-bis(dodecyloxy)benzene (8b): According to ref.,[68,69] a suspension of
11b (450 mg, 2.01 mmol) and K2CO3 (2.02 g, 14.6 mmol) in dry DMF (20 mL) was degassed
for 20 min by a constant nitrogen flow prior to addition of bromododecane (1.2 mL, 5.00
mmol). The reaction mixture was stirred for 3 d at 80 °C. After cooling to room temperature,
the mixture was poured into H2O (30 mL), and the aqueous layer was extracted with Et2O
(3 × 75 mL), hexanes (75 mL) and CH2Cl2 (100 mL). The combined organic layers were dried
(MgSO4), the solvent was removed under reduced pressure and the crude product was purified
by chromatography on SiO2 with hexanes/CH2Cl2 (20:1) to give 8b (1.01 g, 1.81 mmol, 90%,
1
purity >95%) as a white solid. M.p. 65.8 °C; Rf=0.55 (hexanes/CH2Cl2 10:1); H NMR (400
MHz, CDCl3): δ=0.88 (t, J = 6.9 Hz, 6H; 2×CH3), 1.21–1.40 (m, 32H; 2×CH2), 1.42–1.51 (m,
4H; 2×OCH2CH2CH2), 1.82 (quin., J = 14.8 Hz, 6.7 Hz, 4H; 2×OCH2CH2), 3.98 (t,
J = 6.6 Hz, 4H; 2×OCH2), 6.70 ppm (s, 2H; 2×2-H); 13C NMR (101 MHz, CDCl3): δ=14.1
(CH3), 22.7, 25.9, 29.0, 29.3, 29.4, 29.55, 29.59, 29.65, 29.67, 31.9 (CH2), 69.6 (OCH2),
109.3 (C-2), 111.0 (C-4), 120.1 (C-1), 156.2 ppm (C-3); FT-IR (ATR): ν̃=2958 (m), 2943
(m), 2917 (vs), 2870 (m), 2846 (s), 1583 (s), 1557 (m), 1462 (s), 1419 (s), 1390 (s), 1308 (w),
1230 (s), 1199 (w), 1110 (vs), 1062 (s), 1030 (w), 936 (w), 908 (w), 853 (m), 811 (m), 798
(m), 767 (w), 725 (m), 694 (m), 634 (m), 571 (m), 543 (w) cm–1; MS (EI): m/z = 560.3 [M]+;
HRMS (EI): m/z calcd for C30H52BrClO2: 560.2820 [M]+; found: 560.2825; elemental analysis
calcd (%) for C30H52BrClO2: C 64.33, H 9.36; found: C 64.63, H 9.26.
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5-Bromo-1-chloro-2,3-bis(dodecyloxy)benzene (8c): A suspension of 11c (2.37 g, 10.6
mmol), K2CO3 (8.80 g, 64.0 mmol) and 1-bromododecane (6.40 mL, 26.5 mmol) in MeCN
(40 mL) was stirred for 17 h at 90 °C . The reaction mixture was poured into H2O (200 mL)
and extracted with Et2O (2 × 150 mL). The combined organic layers were washed with aque-
ous NaOH (100 mL, 1 M), dried (MgSO4), and the solvent was removed under reduced pres-
sure. The crude product was purified by chromatography on SiO2 with hexanes and subse-
quent crystallization from pentane at –30 °C to give 8c (2.02 g, 3.60 mmol, 34%, purity
1
>95%) as a white solid. M.p. 39.9 °C; H NMR (400 MHz, CDCl3): δ=0.84–0.93 (m, 6H;
2×CH3), 1.20–1.54 (m, 36H; 18×CH2), 1.71–1.86 (m, 4H; 2×OCH2CH2), 3.89–4.02 (m, 4H;
13
2×OCH2), 6.90 (d, J = 2.2 Hz, 1H; 6-H), 7.10 ppm (d, J = 2.2 Hz, 1H; 4-H); C NMR (101
MHz, CDCl3): δ=14.1 (CH3), 22.7, 25.97, 26.04, 29.1, 29.33, 29.38, 29.5, 29.61, 29.62, 29.67,
29.69, 29.71, 30.2, 31.9 (CH2), 69.2 (m-OCH2), 73.6 (p-OCH2), 115.3, 115.6 (C-4, C-6),
124.1 (C-5), 129.3 (C-3), 144.4 (C-2), 153.9 ppm (C-1); FT-IR (ATR): ν̃=2921 (vs), 2852 (s),
1575 (s), 1463 (s), 1405 (s), 1384 (s), 1289 (w), 1259 (s), 1222 (s), 1187 (w), 1099 (w), 1034
(s), 907 (w), 829 (s), 761 (w), 721 (w), 579 (w) cm–1; MS (ESI): m/z = 999, 685, 625, 583
[M+Na]+; HRMS (ESI): m/z calcd for C30H52BrClO2Na: 583.2712 [M(81Br)+Na]+, 581.2731
[M(79Br)+Na]+; found: 583.2681 [M(81Br)+Na]+, 581.2684 [M(79Br)+Na]+.
5-Bromo-1,3-dichloro-2-(dodecyloxy)benzene (8d): To a suspension of 11d[27] (5.82 g, 24.1
mmol) and K2CO3 (17.3 g, 125 mmol) in MeCN (160 mL), degassed for 15 min by a constant
nitrogen flow, was added bromododecane (5.8 mL, 24.1 mmol), and the reaction mixture was
heated at reflux for 16 h. After cooling to room temperature, the solvent was removed under
reduced pressure. The residue was taken up in CH2Cl2 (100 mL) and filtered through Celite®.
The filtrate was concentrated under reduced pressure to give 8d (9.64 g, 23.5 mmol, 98%,
1
purity >95%) as white needles. M.p. 29.4 °C; H NMR (500 MHz, CDCl3): δ=0.88 (t, J =
6.9 Hz, 3H; CH2CH3), 1.21–1.42 (m, 16H; 8×CH2), 1.43–1.58 (m, 2H; OCH2CH2CH2), 1.74–
13
1.88 (m, 2H; OCH2CH2), 3.99 (t, J = 6.6 Hz, 2H; OCH2), 7.43 ppm (s, 2H; 4-H); C NMR
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(126 MHz, CDCl3): δ=14.1 (CH2CH3), 22.7 (CH3), 25.8, 29.36, 29.39, 29.57, 29.61, 29.64,
29.66, 30.0, 31.9 (CH2), 74.0 (OCH2), 116.0 (C-5), 130.5 (C-3), 131.5 (C-4), 151.3 ppm (C-
2); FT-IR (ATR): ν̃=2922 (vs), 2853 (s), 1567 (w), 1550 (m), 1451 (vs), 1379 (s), 1255 (s),
1192 (w), 1124 (w), 985 (w), 855 (m), 805 (s), 750 (m), 684 (w), 569 (w), 424 (w) cm–1; MS
(EI): m/z = 242 [M–C12H25], 410 [M]; elemental analysis calcd (%) for C18H27BrCl2O: C
52.70, H 6.63; found: C 53.41 H 6.64.
General Procedure for the Preparation of MIDA-Boronates 6: Analogous to ref.,[37,70] to a
solution of the appropriate bromobenzene 8a,c,d (1.0 equiv.) in dry THF under nitrogen
atmosphere at –78 °C a 1.6 M solution of n-BuLi in hexane (1.7 equiv.) was slowly added,
and the mixture was stirred for a further 30 min at –78 °C. Triisopropylborate (1.7 equiv.) was
added, and the reaction mixture was warmed to room temperature over 30 min. A hot 0.5 M
solution of MIDA in DMSO (3.0 equiv.) was added, and the reaction mixture was stirred for 2
h at 125 °C. After cooling to room temperature, the mixture was poured into H2O (200 mL)
and Et2O (50 mL) was added. The aqueous layer was extracted with CH2Cl2 (100 mL). The
combined organic layers were washed with brine (100 mL) and dried (MgSO4). The solvent
was removed under reduced pressure, and the residue was purified by chromatography on
SiO2 with hexanes/EtOAc (1:1) and EtOAc.
[3,5-Bis(dodecyloxy)phenyl]-MIDA-boronate (6a): From 8a (1.20 g, 2.28 mmol), n-BuLi
(2.3 mL, 3.65 mmol), triisopropylborate (0.9 mL, 3.88 mmol), and MIDA (15.0 mL, 7.50
mmol) in dry THF (20 mL), white solid (860 mg, 1.43 mmol, 63%, purity >95%); Rf=0.1
1
(hexanes/EtOAc 1:1). M.p. 75.0 °C; H NMR (500 MHz, CDCl3): δ=0.83–0.92 (m, 6H;
2×CH3), 1.17–1.47 (m, 36H; 18×CH2), 1.70–1.80 (m, 4H; 2×OCH2CH2), 2.58 (s, 3H; NCH3),
3.78 (d, J = 16.5 Hz, 2H; 2×a-H), 3.89–3.95 (m, 4H; 2×OCH2), 4.00 (d, J = 16.5 Hz, 2H; 2×a-
H), 6.48 (t, J = 2.2 Hz, 1H; 4-H), 6.60 ppm (d, J = 2.2 Hz, 2H; 2×2-H); 13C NMR (126 MHz,
CDCl3): δ=14.1 (CH3), 22.7, 26.1, 29.36, 29.45, 29.60, 29.63, 29.65, 29.69, 31.9 (CH2), 47.5
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(NCH3), 61.8 (C-a), 68.1 (OCH2), 102.6 (C-4), 110.2 (C-2), 160.6 (C-3), 167.7 ppm (O=C);
FT-IR (ATR): ν̃=2999 (w), 2920 (s), 2851 (s), 1765 (s), 1584 (w), 1466 (w), 1455 (w), 1423
(w), 1384 (w), 1337 (s), 1287 (s), 1250 (w), 1161 (vs), 1126 (s), 1009 (s), 953 (w), 908 (w),
890 (w), 870 (w), 836 (s), 773 (w), 730 (w), 702 (w), 666 (w), 647 (w), 625 (w), 595 (w), 555
(w), 504 (w) cm–1; MS (ESI): m/z = 624 [M+Na]+, 602 [M+H]+; HRMS (ESI): m/z calcd for
C35H60BNO6Na: 624.4412 [M+Na]+; found: 624.4432 [M+Na]+; elemental analysis calcd (%)
for C35H60BNO6: C 69.87, H 10.05, N 2.33; found: C 69.94, H 9.79, N 2.23.
[3-Chloro-4,5-bis(dodecyloxy)phenyl]-MIDA-boronate (6c): From 8c (1.00 g, 1.79 mmol),
n-BuLi (1.8 mL, 2.86 mmol), triisopropylborate (0.7 mL, 3.03 mmol), and MIDA (10.0 mL,
5.00 mmol) in dry THF (15 mL), white solid (930 mg, 1.46 mmol, 82%, purity >95%); Rf=0.1
1
(hexanes/EtOAc 1:1). M.p. 97.2 °C; H NMR (500 MHz, CDCl3): δ=0.84–0.92 (m, 6H;
2×CH3), 1.20–1.39 (m, 32H; 16×CH2), 1.42–1.54 (m, 4H; 2×OCH2CH2CH2), 1.73–1.84 (m,
4H; 2×OCH2CH2), 2.60 (s, 3H; NCH3), 3.76–3.82 (m, 2H; 2×a-H), 3.92–3.99 (m, 4H; 2×a-H,
3-OCH2), 3.99–4.04 (m, 2H; 4-OCH2), 6.92 (d, J = 1.6 Hz, 1H; 2-H), 7.05 ppm (d, J = 1.6 Hz,
13
1H; 6-H); C NMR (126 MHz, CDCl3): δ=14.1 (CH3), 22.7, 26.0, 26.2, 29.38, 29.40, 29.44,
29.5, 29.64, 29.68, 29.72, 30.2, 31.9 (CH2), 47.5 (NCH3), 61.8 (C-a), 69.3 (C-3-OCH2), 73.5
(C-4-OCH3), 115.3 (C-2), 125.5 (C-6), 129.0 (C-5), 146.4 (C-4), 153.7 (C-3), 167.1 ppm
(O=C); FT-IR (ATR): ν̃=3013 (w), 2953 (w), 2914 (s), 2847 (s), 1780 (s), 1747 (s), 1620 (w),
1587 (s), 1553 (w), 1490 (w), 1467 (w), 1390 (w), 1381 (w), 1344 (w), 1290 (s), 1245 (w),
1218 (w), 1164 (w), 1152 (w), 1095 (w), 1055 (s), 1031 (vs), 1003 (s), 950 (s), 911 (w), 881
(w), 857 (s), 752 (w), 718 (w), 677 (w), 608 (w), 506 (w) cm–1; MS (ESI) m/z = 658 [M+Na]+,
636 [M+H]+, 561; HRMS (ESI): m/z calcd for C35H59BClNO6: 658.4022 [M+Na]+; found:
685.4020 [M+Na]+; elemental analysis calcd (%) for C35H59BClNO6: C 66.09, H 9.35, N
2.20; found: C 65.92, H 9.45, N 1.99.
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[3,5-Dichloro-4-(dodecyloxy)phenyl]-MIDA-boronate (6d): From 8d (555 mg, 1.35
mmol), n-BuLi (0.87 mL, 2.16 mmol, 2.5 M in hexane), triisopropylborate (0.6 mL,
2.60 mmol), and MIDA (10.0 mL, 2.80 mmol, 0.28 M in DMSO) in dry THF (30 mL), white
solid (531 mg, 1.09 mmol, 81%, purity >99%); Rf=0.2 (hexanes/EtOAc 2:1). M.p. 164.1 °C;
1H NMR (700 MHz, CDCl3): δ=0.88 (t, J = 7.0 Hz, 3H; CH2CH3), 1.22–1.41 (m, 16H;
8 × CH2), 1.47–1.52 (m, 2H; OCH2CH2CH2), 1.75–1.88 (m, 2H; OCH2CH2), 2.59–2.68 (m,
3H; NCH3), 3.80–3.87 (m, 2H; 2×a-H), 3.98–4.04 (m, 2H; OCH2), 4.04–4.22 (m, 2H; 2×a-H),
13
7.43 ppm (s, 2H; 2×2-H); C NMR (176 MHz, CDCl3): δ=14.1 (CH3), 22.7 (CH2CH3), 25.8,
29.36, 29.42, 29.60, 29.63, 29.64, 29.67, 30.1, 31.9 (CH2), 48.0 (NCH3), 62.1 (C-a), 73.9
(OCH2), 130.0 (C-3), 132.7 (C-2), 152.9 (C-4), 167.9 ppm (C=O); FT-IR (ATR): ν̃=3514 (w),
3012 (w), 2922 (s), 2853 (m), 2159 (w), 2047 (w), 2015 (w), 1982 (w), 1765 (vs), 1584 (w),
1537 (w), 1461 (m), 1369 (m), 1337 (m), 1261 (vs), 1217 (vs), 1151 (w), 1087 (m), 1050 (vs),
1022 (vs), 1008 (s), 965 (m), 946 (m), 907 (m), 894 (m), 858 (s), 827 (w), 796 (s), 735 (m),
668 (w), 624 (w), 584 (w), 543 (w), 502 (w), 459 (w) cm–1; MS (APCI): m/z = 486.20
[M+H]+; HRMS (APCI): m/z calcd for C23H34BCl2NO5: 486.1980 [M+H]+; found: 486.1984
[M+H]+; elemental analysis calcd (%) for C23H34BCl2NO5: C 56.81, H 7.05, N 2.88; found: C
57.03, H 6.97, N 2.83.
General Procedure for the Suzuki Coupling (Route A): Analogous to ref.,[37,68,69] to a
solution of the appropriate MIDA-boronate 6 (3.8 equiv.) in THF (10 mL) a 1 M aqueous
NaOH solution (11.8 equiv.) was added, and the mixture was stirred for 15 min at room
temperature. The mixture was neutralized with a saturated NH4Cl solution, extracted with
CH2Cl2 (100 mL), and the solvent was removed under reduced pressure to give a crude
mixture of the respective boronic acid and boroxine, which was dissolved in DMF or DME
and degassed for 45 min by a constant nitrogen flow. Subsequently, K2CO3 (4.5 equiv.), 7
(1.0 equiv.), Pd(PPh3)4 and degassed H2O (5.0 mL) were added, and the reaction mixture was
stirred for 24 h at 90 °C under a nitrogen atmosphere. After cooling to room temperature, the
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mixture was poured into H2O (200 mL), extracted with CH2Cl2 (200 mL). The organic layer
was concentrated under reduced pressure and the residue was purified by chromatography on
SiO2.
General procedure for the Suzuki coupling (Route B): Analogous to ref.,[68,69] a suspension
of 9 (1.0 equiv.), bromobenzene 8b or 8d (4.1 equiv.), K2CO3 (3.8 equiv.) and Pd(PPh3)4 in
degassed DME (16 mL) / H2O (4.0 mL) was stirred for 24 h at 95 °C under a nitrogen atmos-
phere. After cooling to room temperature, the mixture was poured into H2O (120 mL) and
extracted with CH2Cl2 (4 × 60 mL). The combined organic layers were washed with brine
(80 mL), dried (MgSO4), and the solvent was removed under reduced pressure. The residue
was purified by chromatography on SiO2.
1,3,5-Tris[3',5ꞌ-di(dodecyloxy)phenyl]benzene (5a): According to Route A: from 6a (780
mg, 1.30 mmol), NaOH (4.0 mL, 4.00 mmol) in dry THF (10 mL); K2CO3 (212 mg,
1.53 mmol), 7 (107 mg, 340 µmol), Pd(PPh3)4 (5.00 mg, 4.33 µmol) in DMF (20 mL), H2O
(5.0 mL); purification by chromatography on SiO2 with hexanes/EtOAc (80:1), followed by
crystallization from pentane at –30 °C, white solid (360 mg, 255 µmol, 75%, purity >95%);
1
Rf=0.5 (hexanes/EtOAc 20:1). M.p. 20.0 °C; H NMR (500 MHz, CDCl3): δ=0.84–0.91 (m,
18H; 6×CH3), 1.20–1.42 (m, 96H; 48×CH2), 1.42–1.52 (m, 12H; 6×OCH2CH2CH2), 1.80 (p, J
= 6.7 Hz, 12H; 6×OCH2CH2), 4.00 (t, J = 6.7 Hz, 12H; 6×OCH2), 6.49 (t, J = 2.2 Hz, 3H;
13
3×4'-H), 6.78 (d, J = 2.2 Hz, 6H; 6×2'-H), 7.72 ppm (s, 3H; 3×2-H); C NMR (126 MHz,
CDCl3): δ=14.1 (CH3), 22.7, 26.1, 29.34, 29.36, 29.43, 29.60, 29.62, 29.64, 29.68, 31.9
(CH2), 68.2 (OCH2), 100.4 (C-2ʹ), 106.1 (C-2'), 125.4 (C-2), 142.3 (C-1), 143.2 (C-1'), 160.6
ppm (C-3'); FT-IR (ATR): ν̃=2921 (vs), 2853 (s), 1585 (s), 1466 (w), 1433 (w), 1408 (w),
1384 (w), 1339 (w), 1324 (w), 1259 (w), 1159 (s), 1055 (w), 993 (w), 892 (w), 848 (w), 832
(w), 704 (w), 620 (w), 591 (w) cm–1; MS (MALDI-TOF): m/z calcd for C96H162O6: 1411.24
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[M]+; found: 1408.4 [M]+; elemental analysis calcd (%) for C96H162O6: C 81.64, H 11.56;
found: C 81.57, H 11.77.
1,3,5-Tris[4ꞌ-chloro-3',5ꞌ-di(dodecyloxy)phenyl]benzene (5b): According to Route B: from
8b (500 mg, 893 µmol), K2CO3 (252 mg, 1.83 µmol), 9 (101 mg, 221 µmol), Pd(PPh3)4
(18.8 mg, 15.4 µmol) in DME (20 mL), H2O (3.5 mL); purification by chromatography on
SiO2 with hexanes/CH2Cl2 (gradient 15:1 to 8:1), white solid (255 mg, 168 µmol, 76%, purity
1
>95%). M.p. 17.4 °C; Rf=0.19 (hexanes/CH2Cl2 10:1); H NMR (700 MHz, CDCl3): δ=0.87
(t, J = 7.1 Hz, 18H; 6×CH2CH3), 1.18–1.43 (m, 96H; 48×CH2), 1.49 (p, J = 7.5 Hz, 12H;
6×OCH2CH2CH2), 1.85 (quin., J = 6.8 Hz, 12H; 6×OCH2CH2), 4.08 (t, J = 6.6 Hz, 12H;
6×OCH2), 6.80 (s, 6H; 6×2'-H), 7.63 ppm (s, 3H; 3×2-H); 13C NMR (126 MHz, CDCl3):
δ=14.1, 22.7, 26.0, 29.2, 29.4, 29.57, 29.60, 29.64, 29.7, 31.9 (CH2), 69.6 (OCH2), 105.2 (C-
2ꞌ), 111.8 (C-4ꞌ), 125.6 (C-2), 140.2 (C-1), 142.6 (C-1ꞌ), 156.1 ppm (C-3ꞌ); FT-IR (ATR):
ν̃=2921 (vs), 2853 (s), 1572 (s), 1465 (m), 1415 (s), 1404 (m), 1379 (m), 1334 (m), 1246 (m),
1230 (m), 1196 (w), 1114 (vs), 1061 (m), 990 (w), 901 (w), 831 (m), 712 (w), 684 (w), 632
(w) cm–1; MS (APCI): m/z = 1516.13 [M+H]+; HRMS (APCI): m/z calcd for C96H159Cl3O6:
1516.1282 [M+H]+; found: 1516.1269 [M+H]+; elemental analysis calcd (%) for
C96H159Cl3O6: C 76.08, H 10.57; found: C 75.87, H 10.30.
1,3,5-Tris[5'-chloro-3',4ꞌ-di(dodecyloxy)phenyl]benzene (5c): According to Route A: from
6c (820 mg, 1.29 mmol), NaOH (4.0 mL, 4.00 mmol) in dry THF (10 mL); K2CO3 (220 mg,
1.58 mmol), 7 (110 mg, 350 µmol), Pd(PPh3)4 (4.00 mg, 3.46 µmol) in DMF (20 mL), H2O
(5.0 mL); purification by chromatography on SiO2 with hexanes/EtOAc (80:1), white solid
(302 mg, 200 µmol, 57%, purity >95%); Rf=0.5 (hexanes/EtOAc 50:1). M.p. 115.0 °C;
1H NMR (500 MHz, CDCl3): δ=0.83–0.92 (m, 18H; 6×CH3), 1.19–1.43 (m, 96H; 48×CH2),
1.43–1.58 (m, 12H; 6×OCH2CH2CH2), 1.77–1.89 (m, 12H; 6×OCH2CH2), 4.02–4.09 (m,
12H; 6×OCH2), 7.03 (d, J = 2.1 Hz, 3H; 3×2'-H), 7.24 (d, J = 2.1 Hz, 3H; 3×6'-H), 7.58 ppm
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13
(s, 3H; 3×2-H); C NMR (126 MHz, CDCl3): δ=14.1 (CH3), 22.7, 26.1, 26.2, 29.37, 29.39,
29.42, 29.5, 29.64, 29.67, 29.69, 29.73, 30.3, 31.93, 31.95 (CH2), 69.3, 73.7 (OCH2), 111.3
(C-2'), 120.7 (C-6'), 125.0 (C-2), 128.9 (C-5'), 137.0 (C-1'), 141.4 (C-1), 144.8 (C-4'), 153.7
ppm (C-3'); FT-IR (ATR): ν̃=2921 (vs), 2852 (s), 1593 (w), 1562 (w), 1489 (s), 1467 (s),
1380 (w), 1303 (w), 1272 (w), 1239 (w), 1168 (w), 1127 (w), 1092 (w), 1039 (w), 958 (w),
916 (w), 862 (w), 830 (w), 721 (w), 677 (w), 593 (w) cm–1; MS (MALDI-TOF): m/z calcd for
C96H159Cl3O6: 1513.12 [M]+; found: 1508.3 [M]+; elemental analysis calcd (%) for
C96H159Cl3O6: C 76.08, H 10.57; found: C 76.01, H 10.68.
1,3,5-Tris(3ꞌ,5ꞌ-dichloro-4ꞌ-dodecyloxyphenyl)benzene (5d): According to Route A: from
6d (405 mg, 833 µmol), NaOH (2.7 mL, 2.70 mmol) in dry THF (9 mL); K2CO3 (143 mg,
1.03 mmol), 7 (57.0 mg, 181 µmol), Pd(PPh3)4 (13.0 mg, 11.3 µmol) in DME (15 mL), H2O
(4.0 mL); purification by chromatography on SiO2 with hexanes/CH2Cl2 (gradient 200:1 to
20:1), white solid (81.0 mg, 76.0 µmol, 42%, purity >82%). According to Route B: from 8d
(397 mg, 968 µmol), K2CO3 (122 mg, 883 µmol), 9 (107 mg, 235 µmol), Pd(PPh3)4 (18.0 mg,
15.6 µmol) in DME (16 mL), H2O (4.0 mL); purification by chromatography on SiO2 with
hexanes/CH2Cl2 (gradient 200:1 to 20:1), white solid (220 mg, 206 µmol, 88%, purity >95%).
1
Rf=0.24 (hexanes/CH2Cl2 100:1); M.p. 38.0 °C; H NMR (500 MHz, CDCl3): δ=0.88 (t, J =
6.9 Hz, 9H; 3×CH2CH3), 1.21–1.44 (m, 48H; 24×CH2), 1.51–1.58 (m, 6H; 3×OCH2CH2CH2),
1.82–1.95 (m, 6H; 3×OCH2CH2), 4.08 (t, J = 6.6 Hz, 6H; 3×OCH2), 7.57 (s, 6H; 2ꞌ-H), 7.60
ppm (s, 3H; 2-H); 13C NMR (126 MHz, CDCl3): δ=14.1 (CH3), 22.7 (3×CH2CH3), 25.9,
29.37, 29.44, 29.61, 29.64, 29.66, 29.68, 30.1, 31.9 (CH2), 74.1 (OCH2), 125.1 (C-2), 127.5
(C-2ꞌ), 130.1 (C-1ꞌ), 137.4 (C-1), 140.1 (C-3ꞌ), 151.5 ppm (C-4ꞌ); FT-IR (ATR): ν̃=2921 (vs),
2852 (s), 2173 (w), 2074 (w), 1747 (w), 1597 (w), 1548 (m), 1479 (s), 1464 (vs), 1434 (s),
1380 (m), 1363 (s), 1270 (vs), 1235 (m), 1208 (w), 1077 (m), 1032 (w), 984 (m), 911 (w),
856 (s), 803 (vs), 722 (m), 665 (w), 626 (m), 580 (w), 514 (w), 459 (w) cm–1; MS (APCI): m/z
= 1065.46 [M+H]+; HRMS (APCI): m/z calcd for C60H84Cl6O3: 1065.46 [M+H]+; found:
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1065.46 [M+H]+; elemental analysis calcd (%) for C60H84Cl6O3: C 67.60, H 7.94; found: C
67.64, H 8.06.
Acknowledgement
Generous financial support by the Ministerium für Wissenschaft, Forschung und Kunst des
Landes Baden-Württemberg, the Fonds der Chemischen Industrie, the Bundesministerium für
Bildung und Forschung (shared instrumentation grant 01 RI05177) and the Carl-Schneider-
Stiftung Aalen (shared instrumentation grant) are gratefully acknowledged.
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Graphical Abstract
200 μm
Two variants A and B of the Suzuki-Miyaura cross coupling allow the synthesis of
(poly)chlorinated shaped-persistent hekates 1. Method B was found to be superior to A
improving the yields up to 88%. Liquid crystalline properties of some hekates were observed.
28
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