Liquid crystals in the series of 2,4,6-tristyryl-1,3,5-triazines

Article abstract of DOI:10.1016/j.tet.2004.06.031

Alkaline condensation reactions of 2,4,6-trimethyl-1,3,5-triazine (1) and substituted benzaldehydes (2a-n) yield 2,4,6-tristyryl-1,3,5-triazines (3a-n). A sufficient number and length of the alkoxy chains at the benzene rings provide liquid crystalline ph

Full text of DOI:10.1016/j.tet.2004.06.031

Tetrahedron 60 (2004) 6765–6775
Liquid crystals in the series of 2,4,6-tristyryl-1,3,5-triazines
Hans Christof Holst,a Tadeusz Pakulab and Herbert Meiera
,
*
aInstitute of Organic Chemistry, University of Mainz, Duesbergweg 10-14, D-55099 Mainz, Germany
bMax Planck-Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
Received 2 April 2004; revised 8 June 2004; accepted 8 June 2004
Abstract—Alkaline condensation reactions of 2,4,6-trimethyl-1,3,5-triazine (1) and substituted benzaldehydes (2a–n) yield 2,4,6-tristyryl-
1,3,5-triazines (3a–n). A sufficient number and length of the alkoxy chains at the benzene rings provide liquid crystalline phases Colhd. A
special structure was found for compound 3i with 9 hexyloxy chains; it exists in the solid state in a helical columnar arrangement, which is
transformed by heating to a hexagonal columnar mesophase. Irradiation of the mesophases of 3i–3m leads to partial cyclodimerization
reactions, which cause different textures and lower the clearing points. The border line between the irradiated and the unirradiated zones is
preserved in the solid and the liquid crystalline temperature range but also over a surprisingly long period in the molten state. A detailed study
of this imaging technique was performed for the LC phase of 3i.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
triphenyl derivatives,4 some dendritic compounds whose
arms consist of tolane units,5,6 a tris(phenylethynyl)
compound,7 and systems with oligo(1,4-phenylenevinylene)
[OPV] arms.8
Star-shaped stilbenoid compounds with a 1,3,5-triazine core
and peripheral alkoxy groups represent octupolar structures
with interesting non-linear optical properties (NLO); more-
over, they can form liquid crystalline columnar phases
provided that they contain a large enough fraction of
long flexible side chains. The hyperpolarizabilities b of
2,4,6-triphenyl-1,3,5-triazines have been reported
recently.1–3 The b0 values, extrapolated to infinite wave-
length and related to 4-nitroaniline as standard gave a
value brel
2. Results and discussion
2.1. Preparation of alkoxy substituted 2,4,6-tristyryl-
1,3,5-triazines
The methyl groups in 2,4,6-trimethyl-1,3,5-triazine (1)
b0ð2; 4; 6-triphenyl-1; 3; 5-triazineÞ £ molecular massð4-nitroanilineÞ
b0ð4-nitroanilineÞ £ molecular massð2; 4; 6-triphenyl-1; 3; 5-triazineÞ
brel
¼
which at most was slightly better than the standard value
1.0 for 4-nitroaniline.1–3 An extension of the conjugation
by 2,4,6-tris(4-diethylaminophenylethynyl) substituents
improved considerably the results.1,2
undergo in an alkaline medium [CH3OH/KOH or THF/
KOC(CH3)3] threefold condensation reactions with sub-
stituted benzaldehydes (2a–n). The aldehydes 2j and 2n are
not described in the literature; they were prepared from
3,4,5-trihydroxybenzoic acid ethyl ester by threefold
O-alkylation, reduction to the corresponding benzyl alcohol
and oxidation with DDQ.
We tried now to combine the extension of the conjugated
arms with the capability of forming liquid crystalline phases
and attached alkoxy substituted styryl groups in 2,4,6-
position to the 1,3,5-triazine ring. Mesophases of star-
shaped triazine systems were found in the past for some
The highly stereoselective condensation reaction affords
(E,E,E)-2,4,6-tristyryl-1,3,5-triazines (3a–n) in good yields
1
(Scheme 1). The H and 13C NMR spectra of the purified
products do not contain any hints for Z configurations; the
detection limit is about 3%. A thermal isomerization in the
neat state or in solution can be excluded for temperatures
below 150 8C.
Keywords: Columnar arrangement; Condensation; Cyclodimerization;
Helical arrangement; Imaging technique; Liquid crystals.
*
Corresponding author. Tel.: þ49-6131-3922605; fax: þ49-6131-
3925396; e-mail address: hmeier@mail.uni-mainz.de
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.06.031

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H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
Scheme 1. Preparation of (E,E,E)-2,4,6-tristyryl-1,3,5-triazines.
2.2. Formation of LC phases
Three further side chains, introduced in 3h, lead already to a
mesophase between 75 and 82 8C (second heating curve).
The texture obtained by polarizing microscopy reveals a
liquid crystalline phase. This result encouraged us to study
the compounds 3i–n which contain 9 side chains, each.
Table 1 summarizes the DSC measurements.
2,4,6-Tristyryl-1,3,5-triazines can be regarded as disc-like
molecules, which can exhibit a regular aggregation by p
stacking and by the interaction of additionally present side
chains. The compounds 3a–g bear three alkoxy chains;
irrespective of the chain length, this number of side chains
proved to be not sufficient for the formation of thermotropic
liquid crystals. Accordingly, the yellow crystals of 3a–g
exhibit sharp melting points at 228, 99, 109, 96, 85, 76 and
63 8C, respectively. A slight exception was only found for
3d which showed in the heating curve of the differential
scanning calorimetry (DSC) an endothermic peak at 96 8C
with a shoulder at 94 8C. Obviously, a further (crystalline)
phase exists in this 2 degrees broad temperature interval.
This behavior, observed in the first heating curve (rate:
10 8C/min), can be repeated in the second heating curve
after a delay of about 5 days at room temperature.
Figure 1 shows, as an example, the thermo-mechanical
characteristics of the 3l sample. The DSC diagrams indicate
two transitions and the temperature dependences of
components of the complex shear modulus reveal related
changes of mechanical properties. The solid state
(G0.108 Pa) at low temperatures is transformed at the low
temperature transition to a considerable softer phase
(G0<105 Pa) and the material melts at the other transition
becoming liquid-like with viscosity dependent on the side
chain length and temperature (in this example h<5 Pa s just
above the transition). The two transitions have been
Table 1. DSC measurements of the phase transitions KYLCYI (crystalYliquid crystalYmelt) of the compounds 3i–n: H second heating curve, C first
cooling curve, rate: 10 8C per min
Compound
Process
H/C
Phase transitions
3
KYLC
Temperature [8C]
LCYI
Temperature [8C]
DH
DH
Onset
Maximum
kJ mol21
Onset
Maximum
kJ mol21
3i
H
C
H
C
H
C
H
C
H
C
H
63.4
49.5
32.2
68.4
47.6
42.6
8.6
25.3
2.3
109.5
110.8
86.3
101.3
79.0
88.4
88.1
87.8
76.8
79.1
36.5
112.0
108.8
101.8
96.4
90.1
84.2
90.1
86.9
80.3
77.9
45.3
7.8
27.6
8.8
26.6
8.5
27.4
12.0
29.9
14.3
212.8
8.0
3ja
3k
3l
256.6
210.4
2.6
5.2
40.0/48.8
33.0/43.4
223.2
233.7
8.7
1.7
44.9/50.3
29.6/42.3
21.7
218.6
37.4
242.5
127.5
269.7
3mb
3nc
a
The phase transition LC!K is extremely slow. The second heating curve was measured after 1 week.
b
c
The processes K!LC and LC!K are characterized by double peaks; the phase in between is highly viscous and seems to have a plastic crystalline status.
The enthalpy for the formation of the LC phase, which has a low viscosity is very high.
The phase transition I!LC in 3n, which has branched sidechains, is extremely slow; a crystallization could not be observed in the DSC.

H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
6767
exhibit a minimum for the decyloxy substituted compound
3k. Figure 3 shows the temperature intervals in which the
mesophases of 3i–m exist. Extension of the length of the
OCnH2nþ1 chains (n¼6, 8, 10, 12, 16) permits the regulation
of the width of the LC phase. The maximum width is
reached with DT<113 8C for 3k (n¼10).
X-ray scattering studies of 3i–m revealed some structural
details of the phases separated by the above transitions.
Examples of the X-ray intensity distributions recorded at
various states of the 3j sample are shown in Figure 4. The
intensity profiles differ remarkably not only when recorded
at different temperatures but they are also very sensitive to
thermal history. Especially, the states at low temperatures
considered as crystalline (Fig. 4(a) and (d)) were dependent
on the annealing and cooling conditions. The intermediate
state (Fig. 4(b))—the mesophase—was in all samples
recognized as a hexagonal columnar phase Colhd. A special
technique was used to measure the columns in a
macroscopic orientation.9 The oriented samples were
obtained by extrusion at temperatures of the mesophase.
An example of the 2D X-ray scattering pattern of such a
structure is shown in Figure 5(a). The pattern exhibits
small angle equatorial reflections indicating well oriented
hexagonally ordered columns and a diffuse meridional halo
superimposed on the less intense isotropic amorphous halo.
Figure 5(b) shows the equatorial intensity distributions
for various samples. For the 3i sample, an assignment of
reflections is given in Table 2, as an example. Variation of
relative reflection intensities in various samples results from
the variation of the columnar core/shell volume fractions
with the length of the side chains.10
Figure 1. An example of the thermo-mechanical characteristics for the 3l
sample: (a) the DSC traces recorded during cooling (C) and second heating
(H) with the rate of 10 8C/min and (b) the temperature dependencies of the
real (G0) and imaginary (G00) components of the complex shear modulus
recorded in the dynamic mechanical test with the frequency of 10 rad/s
under cooling with the rate of 2 8C/min.
observed for all samples with the 9 side chains. Polarizing
optical microscopy observations revealed textures
suggesting liquid crystalline states below the transitions at
higher temperatures. Figure 2 shows the DSC thermograms
recorded for samples with various side chain lengths
indicating a behavior very sensitive to this structural
parameter. Increasing length of the alkoxy side chains
leads to a steady decrease of the temperatures for the phase
transiton LC!I, whereas the temperatures for K!LC
The reflections in the small angle area prove the hexagonal
columnar arrangement, since the values of a, b, and c in the
diffractogram correspond to the expected ratio:
p
sðaÞ : sðbÞ : sðcÞ ¼ 0:43 : 0:74 : 0:85 < 1 : 3 : 2
ð1Þ
The calculated values (Eq. (2)) and the observed values for
21 (Fig. 5) agree very well. The length a of the elementary
cell amounts to 2.72 nm.
s
4
3a2
s2 ¼
ðh2 þ k2 þ hkÞ
ð2Þ
Table 3 contains the parameters d of 3i–m. They represent
the distance of the columns in the hexagonal arrangement
and are compared to the hypothetic diameters D of the discs,
which are valid for all-anti conformations of the alkoxy
chains. The increasing difference D¼D2d with increasing
numbers n can be rationalized by an increasing interdigi-
tation of the chains of neighboring columns and/or by an
increasing deviation of the chains from the all-anti
conformation.
In the optically isotropic state at high temperatures, a small
angle halo (Fig. 4(c)) indicates an ordering over distances
comparable to the molecular sizes. This can be attributed to
the molecular excluded volume effect, which is detectable
due to the electron density contrast between the aromatic
center and the aliphatic periphery of the molecules. In this
state, the molecules can be regarded as multiarm stars for
which this kind of ordering has been detected even for much
Figure 2. DSC thermograms for the series of samples 3i–m recorded
during the second heating run with the rate of 10 8C/min.

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H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
Figure 3. Temperature intervals in which the LC phases of 3i–3m (n¼6, 8, 10, 12, 16) exist; the phase transition temperatures (P and O) represent the peak
maxima in the DSC (second heating run with a rate of 10 8C min21).
longer side chains.11 The position of the maximum of this
small angle halo is dependent on the side chain length and
reflects the correlation distance between the molecular
centers. In the case of a three dimensional disorder (no
preaggregation of the molecules into short columnar stacks),
this correlation distance should scale with the molecular
two-dimensionally packed columns the intercolumnar
distances should scale as M1/2, if the intermolecular distance
along the columns remains constant. In Figure 6, the
correlation distances for the isotropic phase and for the
mesophase are compared with the respective dependencies
(dashed lines). These scalings are nearly fulfilled which
further confirms the validity of the assignments made.
mass of the molecules as M .
1/3 11 In contrast to that, for the
Figure 4. An example of the diffracted X-ray intensity distributions
recorded at various states of the 3j sample: (a) as drawn filament at room
temperature (crystalline state), (b) at T¼50 8C—mesophase, (c) isotropic
melt at 110 8C and (d) an ordered state at room temperature after slow
cooling through the mesophase.
Figure 5. A characteristic scattering 2D pattern for an oriented filament in
the mesophase (A) and corresponding equatorial X-ray intensity distri-
butions for the series of samples 3i–m (B). The insert in B illustrates the
unit cell of a hexagonal lattice assumed for the lateral packing of columns.

H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
Table 2. X-ray diffraction pattern shown in Figure 5 for 3i; measurement at
77 8C
6769
Reflection
Miller index
s 21 [nm]
h
k
l
Calcd
Found
a
b
c
d
1
1
2
2
0
1
0
1
0
0
0
0
2.36
1.36
1.18
0.89
2.33
1.35
1.18
0.89
Table 3. Diameter D of the disc-like molecules 3i–3m (sidechains in all-
anti conformation) and distance d of the columns in the LC phases
˚
D [A]
˚
d [A]
˚
D2d [A]
Compound
n
Temperature [8C]
3i
3j
3k
3l
3m
6
8
10
12
16
77
77
27
27
57
33.0
38.1
43.2
48.3
58.5
27.2
30.2
32.2
34.6
39.8
5.8
7.9
10.9
13.7
18.7
It has been observed that annealing or slow cooling through
the mesophase of the macroscopically oriented samples
resulted in longer range correlations in the structures formed
at low temperatures, considered as the crystalline state
(Fig. 4(d)). These correlations were manifested in small
angle reflections appearing at these temperatures in some
cases only in addition to the hexagonal columnar order as in
the example in Figure 4(d). Moreover, these correlation
distances were observed to be side chain length dependent
as seen in Figure 6.
Special arrangements of the discotic molecules were found
in the solid states of 3i and 3m samples. Figure 7 shows
the 2D patterns of X-ray diffraction recorded at the room
temperature for these systems. In both cases, a helical
arrangement is conjectured, however, a detailed modeling is
necessary to make such conclusions. Especially, in the case
of 3i, the scattering pattern exhibits several characteristic
features of diffraction on helical structures: the layered
distribution of intensities, the reflections aligned in an
Figure 7. Examples of scattering patterns recorded for highly ordered
crystalline states of the samples (a) 3i and (b) 3m.
X-pattern and lack of meridional reflections up to the 11th
layer. This allows extraction of some parameters of the
structure. The layer spacing gives the helical pitch
P¼3.97 nm and the meridional reflection of the 11th layer
line indicates 11 molecules per pitch with the intermolecular
separation d¼0.36 nm. The X-like distribution of reflections
seems to indicate pairs of columns forming a helix. The
structure of 3m is much less complicated. The columns
remain here hexagonally ordered and each second molecule
seems to be in identical position. The intermolecular
distance along the columns is considerably larger
(d¼0.42 nm).
All experience with the studied compounds indicates a very
high sensitivity of intermolecular organization to the details
of molecular architecture. In addition to the results already
reported, two effects are shown in Figure 8. The DSC traces
indicate drastic changes of transition temperatures and
enthalpies as a result of variation of some intramolecular
details. In Figure 8(a) the effect of the number of side chains
and in Figure 8(b) the effect of the side chain architecture is
documented.
In the second case, both the total molecular mass and the
molecular mass of the side chains are kept constant;
nevertheless, the slightly different skeleton of bonds causes
Figure 6. Molecular mass dependencies of the correlation distances
detected for various states. The dashed lines represent suggested scaling
dependencies.

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H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
right lower part, which was covered and did not absorb light,
the original LC phase was preserved. Figure 9(e) demon-
strates the new texture (left upper part) and the unirradiated
crystals (right lower part) at 25 8C (birefringence). Warming
to 95 8C led to the picture (9f). The original LC phase is
again formed (Tcl¼112 8C), whereas the new texture has
disappeared. The border line between the two textures
persists during many heating and cooling processes. The
breakdown of the LC phase can be already provoked by the
photochemical transformation of a few percent trans isomer
to the cis configuration. In the case of 3i, however, we found
predominantly the formation of a cyclodimer with one four-
membered ring and four trans configured styryl units.12 We
assume that the diffusion of such a dimer in the LC phase or
even in the molten state is so slow that the border line
between the irradiated and the unirradiated zone is kept
intact for many days.
The analogous irradiation experiments, performed with
3j–m, gave the corresponding results. However, one has to
realize that 3k and 3l form light-sensitive mesophases
already at room temperature. Therefore from a technical
point of view, it seems to be more appropriate to warm and
‘write’ with a laser beam in the Colhd phase of 3i and to
‘read’ it at ambient temperatures, where the daylight
including its UV portion is inactive.
Figure 8. Effects of molecular architecture on the thermodynamic behavior
detected by means of the DSC: (a) effect of the number of side chains and
(b) effect of the side chain architecture.
3. Conclusions
Alkaline condensation reactions of 2,4,6-trimethyl-1,3,5-
triazine (1) and substituted benzaldehydes (2a–n) yield
2,4,6-tristyryl-1,3,5-triazines (3a–n). At least two, but
better three long flexible alkoxy chains, attached to each
of the terminal benzene rings, are necessary to provide
liquid crystalline properties. The Colhd mesophases of 3i–m
were characterized by DSC, polarized mircoscopy and
X-ray diffraction. A special structure was found for
compound 3i with 9 hexyloxy chains; it exists in the solid
state in a helical columnar arrangement, which is trans-
formed to disordered hexagonal columns in the mesophase.
Irradiation (l¼366 nm) of the mesophases of 3i–m
provokes partial cyclodimerization reactions, which cause
lower clearing points and different textures. Diffusion
processes of the dimer are so ineffective that the border
line between the original LC phase and the photoconverted
LC phase is preserved—even in the molten state. Thus, the
compounds 3i–m seem to be suitable for an optical data
storage in LC materials. A report on the NLO properties of
3a–n shall be given later.
a variation of the temperature of isotropization by nearly
40 8C.
2.3. Light absorption and photochemistry
Tristyryltriazine 3i shows a long-wavelength absorption in
CH2Cl2 with a maximum at 366.5^1 nm. The intense band
(log 1¼4.90) corresponds to an intramolecular charge
transfer from one of the three donor moieties to the central
1,3,5-triazine ring as acceptor. Apart from a positive
solvatochromic effect, the UV/vis spectrum is affected by
a protonating medium. Continuous addition of trifluoro-
acetic acid to a solution of 3i in CHCl3 provokes a
bathochromic shift till the maximum reaches the lmax value
of 449 nm. Protonation of the 1,3,5-triazine ring enhances
the push–pull effect. 2,4,6-Tris{(E)-2-[(4-dimethylamino)-
phenyl]ethenyl}-1,3,5-triazine8 shows first a similar effect;
the yellow solution in CHCl3 (lmax¼427 nm) turns violet on
protonation (lmax¼549 nm) but then a subsequent protona-
tion of the amino groups causes a hypsochromic effect
to yield a colorless solution (lmax¼365 nm). The weak
basicity of the alkoxy groups in 3i is obviously not capable
of reverting the red-shift.
4. Experimental
4.1. General remarks
On monochromatic irradiation with l¼366 nm, 3i proved to
be photostable in the solid state. However, as soon as an
enhanced mobility of the molecules was achieved in the LC
phase, a photoreaction started. Figure 9 shows the changes
in the LC phase. The irradiation at 95 8C in the left upper
part led to the disappearance of the texture (a!b!c). On
cooling from 95 to 70 8C a texture reappeared (c!d);
however, it was different from the original texture. In the
Melting points of 3a–3g were measured on a Buchi melting
point apparatus and are uncorrected. The DSC measure-
ments of 3d and 3h–3n were obtained by means of a DSC 7
¨
Perkin–Elmer apparatus. H and 13C NMR spectra were
recorded with a Bruker ARX400 or Avance-600. The mass
spectra were obtained on a Finnigan MAT95 with the field
desorption technique (FD). The UV/vis spectra were
1

H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
6771
Figure 9. Irradiation (l¼366 nm) of a thin film of the Colhd phase of 3i under the polarizing microscope: (a) texture of the unirradiated mesophase measured at
95 8C (left upper part); (b) beginning change of the mesophase by irradiation at 95 8C (left upper part), covered (right lower part); (c) isothermal transformation
of the mesophase to the isotropic melt by irradiation at 95 8C (left upper part), covered (right lower part); (d) texture obtained by cooling to 70 8C (left upper
part), covered (right lower part); (e) texture of the new mesophase at 25 8C (left upper part), unirradiated crystals at 25 8C, birefringence (right lower part);
(f) transformation of the new mesophase to the isotropic melt at 95 8C (left upper part), original mesophase, which still exists at 95 8C (right lower part). The
green color is due to the used interference filter (l¼546 nm), which excludes unwanted light, which can be absorbed by the LC film; the black color represents
in the left upper parts of c and f non-birefringent molten states and in the right lower parts of b, c and d covered regions, which are protected from light.
recorded with a Zeiss MCS 320/340. A set-up of Jenapol
Zeiss, a Linkam TMS 93 and a Soft Imaging System CC-12
served for the polarizing microscopy. Rheometric Scientific
ARES systems was used to determine the dynamic
mechanical behavior. The X-ray studies were performed
using two instruments: a u–u diffractometer (Siemens) and
a set-up with pinhole collimation of the X-ray beam and a
two-dimensional detector (Bruker) with 1024£1024 pixels.
In order to obtain macroscopically oriented samples, the
materials studied have been extruded using a simple mini-
extruder.9 All samples have been deformed at temperatures
within the mesophase to the draw ration l¼8 which gave the

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H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
filaments of the diameter of about 0.7 mm. The 2D patterns
have been recorded with vertical orientations of filaments.
The results of intensity distributions are presented as
functions of the scattering vector (s¼2 sin u/l, where u is
the scattering angle).
(OCH2), 105.3 (C-2, C-6), 137.6 (C-1), 139.0 (C-4), 153.2
(C-3, C-5); FD MS: m/z (%)¼493 (100, MþHþ)]. The
oxidation of the benzyl alcohol (8.34 g, 16.95 mmol) was
performed with DDQ (4.54 g, 20.0 mmol) in 80 mL dry
1,4-dioxane. After having stirred over night at room
temperature, the reaction mixture was filtered and the
solvent evaporated. The distillation yielded 6.12 g (74%) of
the colorless compound 2j (bp 220 8C at 0.02 torr). 1H NMR
(CDCl3): d¼0.86 (t, 9H, CH3), 1.26 (m, 24H, CH2), 1.46
(m, 6H, CH2), 1.73 (m, 2H, CH2), 1.80 (m, 4H, CH2), 4.01
(t, 4H, OCH2), 4.03 (t, 2H, OCH2), 7.06 (s, 2H, 2-H, 6-H),
9.80 (s, 1H, CHO); 13C NMR (CDCl3): d¼14.1 (CH3) 22.6,
26.0, 29.2, 29.3, 29.4, 30.3, 31.8, 31.9 (CH2), 69.2 (OCH2),
73.6 (OCH2), 107.8 (C-2, C-6), 131.4 (C-1), 143.8 (C-4),
153.5 (C-3, C-5), 191.3 (CHO); FD MS: m/z (%)¼490 (100)
[Mþ]. Anal. calcd for C31H54O4 (490.8): C, 75.87; H, 11.09.
Found: C, 75.71; H, 11.17.
4.2. General procedure for the preparation of the 2,4,6-
tristyryl-1,3,5-triazines 3a–n
Variant A. To 2,4,6-trimethyl-1,3,5-triazine (1)13
[123.2 mg, 1.00 mmol] in 20 mL 10% methanolic KOH,
the corresponding aldehyde 2 (3.00–4.00 mmol) dissolved
in 20 mL methanol was added. After a few minutes of
stirring at room temperature, the reaction mixture was
refluxed, till the TLC control (SiO2, diethyl ether) showed,
that the reaction has come to the end. The precipitate formed
at 5 8C was filtered off and washed with cold methanol.
Column chromatography (SiO2, petroleum/ethyl acetate)
and/or recrystallization yielded the analytically pure
product. The variant A was used for the preparations of
3a–3f.
4.2.2. 3,4,5-Tris(3,7-dimethyloctyloxy)benzaldehyde
(2n). Ethyl 3,4,5-trihydroxybenzoate (4.0 g, 20.2 mmol)
was treated with racemic 1-bromo-3,7-dimethyloctane
(15.0 g, 67.8 mmol) in 100 mL acetone in the presence of
K2CO3 (13.8 g, 100 mmol), KI (33 mg, 0.20 mmol) and a
drop of Aliquat 366. After 5 days refluxing and vigorous
stirring, the mixture was filtered and the solvent evaporated.
The raw material of ethyl 3,4,5-tris(3,7-dimethyloctyl-
oxy)benzoate (11.2 g, 90%) was filtered over SiO2 (as
described above), spectroscopically characterized and used
for the next step without further purification. [1H NMR
(CDCl3): d¼0.84 (d, 18H, terminal CH3), 0.89 (d, 3H, CH3),
0.92 (d, 6H, CH3), 1.10–1.95 (m, 30H, CH2 and CH), 1.36
(t, 3H, CH3, ethoxy), 4.02 (m, 6H, OCH2), 4.33 (q, 2H,
OCH2, ethoxy), 7.24 (s, 2H, 2-H, 6-H); 13C NMR (CDCl3):
d¼14.4 (CH3, ethoxy), 19.6 (CH3), 22.6, 22.7 (terminal
CH3), 24.7 (CH2), 28.0, 28.0, 29.6, 29.8 (CH), 36.3, 37.3,
37.5, 39.2, 39.3 (CH2, partly superimposed), 61.0 (OCH2,
ethoxy), 67.4, 71.7 (OCH2), 107.8 (C-2, C-6), 125.0 (C-1),
142.2 (C-4), 152.8 (C-3, C-5), 166.5 (CO); FD MS: m/z
(%)¼619 (100, Mþ)]. The reduction of 10.50 g
(16.96 mmol) ester with 342 mg (9.0 mmol) LiAlH4 in dry
ether, as described above, yielded 9.50 g (97%) of 3,4,5-
tris(3,7-dimethyloctyloxy)benzyl alcohol. The colorless oil
was spectroscopically characterized and then used for the
following step. [1H NMR (CDCl3): d¼0.84 (d, 18H,
terminal CH3), 0.89 (d, 3H, CH3), 0.91 (d, 6H, CH3),
1.10–1.90 (m, 30H, CH2 and CH), 3.98 (m, 6H, OCH2),
4.57 (s, 2H, CH2OH), 6.54 (s, 2H, 2-H), 6-H); 13C NMR
(CDCl3): d¼19.6 (CH3), 22.6, 22.7 (terminal CH3), 24.7
(CH2), 28.0, 28.0, 29.7, 29.8 (CH), 36.4, 37.3, 37.5, 39.3,
39.4 (CH2, partly superimposed), 65.7 (CH2OH), 67.4, 71.6
(OCH2), 105.2 (C-2, C-6), 136.0 (C-1), 137.5 (C-4), 153.3
(C-3, C-5); FD MS: m/z (%)¼577 (100, Mþ)]. The
oxidation was performed as described above for 2j; 9.00 g
(15.6 mmol) of the alcohol and 3.90 g (17.2 mmol) DDQ in
80 mL dry 1,4-dioxane yielded 7.80 g (87%) of the colorless
oil 2n. (Further purification is possible by a filtration over
SiO2 (12£8 cm) using CH2Cl2 as solvent). 1H NMR
(CDCl3): d¼0.84 (d, 6H, terminal CH3), 0.85 (d, 12H,
terminal CH3), 0.90 (d, 3H, CH3), 0.93 (d, 6H, CH3), 1.10–
1.90 (m, 30H, CH2 and CH), 4.04 (m, 6H, OCH2), 7.07 (s,
2H, 2-H, 6-H), 9.82 (s, 1H, CHO); 13C NMR (CDCl3):
d¼19.6 (CH3), 22.6, 22.7 (terminal CH3), 24.7 (CH2), 28.0,
28.0, 29.6, 29.8 (CH), 36.2, 37.3, 37.4, 39.2, 39.3 (CH2,
Variant B. Instead of KOH/methanol, KOC(CH3)3/THF was
used. The ratio of 1 and 2 was the same as for variant A. In
the majority of cases, the product formation was already
complete at room temperature. The work-up was performed
as described above. The variant B was applied for the
preparations of 3g–3n.
Aldehyde 2a is commercially available, the aldehydes 2b,14
2c,15 2d,16 2e,16 2f,16 2g,14 2h,17 2i,18 2k,18 2l19 and 2m20
were prepared according to the literature.
4.2.1. 3,4,5-Trioctyloxybenzaldehyde (2j). Ethyl 3,4,5-
trihydroxybenzoate (5.0 g, 25.3 mmol) was treated with
1-bromooctane (16.2 g, 83.8 mmol) in 100 mL acetone in
the presence of K2CO3 (13.8 g, 100.0 mmol) and KI (33 mg,
0.20 mmol). After 5 days refluxing and stirring, the mixture
was filtered and the solvent evaporated. Column chroma-
tography (12£8 cm SiO2, toluene) yielded 11.9 g (88%) of
ethyl 3,4,5-trioctyloxybenzoate, a colorless oil which was
spectroscopically characterized and then directly used for
the next step. [1H NMR (CDCl3): d¼0.87 (t, 9H, CH3), 1.27
(m, 24H, CH2), 1.36 (t, 3H, CH3, ethoxy), 1.46 (m, 6H,
CH2), 1.73 (m, 2H, CH2), 1.80 (m, 4H, CH2), 4.00 (m, 6H,
OCH2), 4.33 (q, 2H, OCH2, ethoxy), 6.88 (s, 2H, 2-H, 6-H);
13C NMR (CDCl3): d¼14.1 (CH3), 14.4 (CH3, ethoxy),
22.6, 26.1, 29.2, 29.3, 29.4, 30.3, 31.8, 31.9 (CH2, partly
superimposed), 69.2 (OCH2), 73.4 (OCH2), 108.0 (C-2,
C-6), 125.0 (C-1), 142.3 (C-4), 152.8 (C-3, C-5), 166.4
(CO); FD MS: m/z (%)¼535 (100, MþHþ)]. The ester
(11.8 g, 22.09 mmol) was reduced with LiAlH4 (0.460 g,
12.1 mmol) in 50 mL dry diethyl ether. After 1 h refluxing
and destruction of the excess LiAlH4 with water/10%
H2SO4, 3,4,5-trioctyloxybenzyl alcohol (8.50 g, 78%) was
isolated as a colorless wax (mp 50 8C). After the spectro-
scopic characterization, it was used for the following step
without further purification. [1H NMR (CDCl3): d¼0.87 (t,
9H, CH3), 1.26 (m, 24H, CH2), 1.45 (m, 6H, CH2), 1.76 (m,
6H, CH2), 3.91 (t, 2H, OCH2), 3.95 (t, 4H, OCH2), 4.56 (s,
2H, CH2OH), 6.53 (s, 2H, 2-H, 6-H); 13C NMR (CDCl3):
d¼14.1 (CH3), 22.6, 26.1, 29.3, 29.4, 29.5, 30.3, 31.8 (CH2,
partly superimposed), 65.6 (CH2OH), 69.1 (OCH2), 73.4

H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
6773
partly superimposed), 67.1, 71.8 (OCH2), 107.8 (C-2, C-6),
131.4 (C-1), 143.7 (C-4), 153.5 (C-3, C-5), 191.3 (CHO);
FD MS: m/z (%)¼575 (100) [Mþ]. Anal. calcd for
C37H66O4 (574.9): C, 77.30; H 11.57. Found: C, 77.15; H,
11.71.
(m, 6H, CH2), 1.79 (m, 6H, CH2), 3.99 (t, 6H, OCH2), 6.92
(AA0, 6H, m-H), 7.00 (d, 3J¼16.0 Hz, 3H, a-H), 7.61 (MM0,
6H, o-H), 8.20 (d, 3J¼16.0 Hz, 3H, b-H); 13C NMR
(CDCl3): d¼14.1 (CH3), 22.6, 26.0, 29.1, 29.2, 31.8
(CH2), 68.1 (OCH2), 114.8 (m-CH), 123.9 (a-CH), 128.1
(i-Cq), 129.7 (o-CH), 141.1 (b-CH), 160.7 (p-CqO), 171.3
(C-2); FD MS: m/z (%)¼730 (100) [Mþ]. Anal. cacd for
C48H63N3O3 (730.0): C, 78.97; H, 8.70; N, 5.76. Found: C,
78.67; H, 8.84; N, 5.68.
4.2.3. 2,4,6-Tris[(E)-2-(4-methoxyphenyl)ethenyl]-1,3,5-
triazine (3a). Yield 94%, yellow needles, mp 228 8C. UV
1
(CH2Cl2): lmax¼356 nm, log 1¼5.04. H NMR (CDCl3):
0
3
d¼3.85 (s, 9H, OCH3), 6.94 (AA , 6H, m-H), 7.01 (d, J¼
15.8 Hz, 3H, a-H), 7.62 (MM0, 6H, o-H), 8.21 (d, 3J¼
15.8 Hz, 3H, b-H); 13C NMR (CDCl3): d¼55.4 (OCH3),
114.4 (m-CH), 124.3 (a-CH), 128.5 (i-Cq), 129.7 (o-CH),
141.0 (b-CH), 161.1 (p-CqO), 171.4 (C-2); FD MS: m/z
(%)¼477 (100) [Mþ]. Anal. calcd for C30H27N3O3 (477.6):
C, 75.45; H, 5.70; N, 8.80. Found: C, 75.31; H, 5.88; N,
8.72.
4.2.8. 2,4,6-Tris[(E)-2-(4-octyloxyphenyl)ethenyl]-1,3,5-
triazine (3f). Yield 61%, yellow powder, mp 76 8C. UV
1
(CH2Cl2): lmax¼362 nm, log 1¼5.03. H NMR (CDCl3):
d¼0.87 (t, 9H, CH3), 1.28 (m, 24H, CH2), 1.45 (m, 6H,
CH2), 1.79 (m, 6H, CH2), 3.99 (t, 6H, OCH2), 6.92 (AA0,
0
3
6H, m-H), 7.00 (d, J¼16.1 Hz, 3H, b-H), 7.61 (MM , 6H,
o-H), 8.20 (d, J¼16.1 Hz, 3H, b-H); 13C NMR (CDCl3):
3
d¼14.1 (CH3), 22.6, 26.0, 29.2, 29.2, 29.3, 31.8 (CH2), 68.1
(OCH2), 114.8 (m-CH), 123.9 (a-CH), 128.1 (i-Cq), 129.7
(o-CH), 141.1 (b-CH), 160.7 (p-CqO), 171.3 (C-2); FD MS:
m/z (%)¼772 (100) [Mþ]. Anal. calcd for C51H69N3O3
(772.1): C, 79.33; H, 9.01; N, 5.44. Found: C, 79.22; H,
9.17; N, 5.57.
4.2.4. 2,4,6-Tris[(E)-2-(4-propoxyphenyl)ethenyl]-1,3,5-
triazine (3b). Yield 86%, yellow powder, mp 99 8C. UV
1
(CH2Cl2): lmax¼360 nm, log 1¼5.04. H NMR (CDCl3):
d¼1.04 (t, 9H, CH3), 1.82 (m, 6H, CH2), 3.96 (t, 6H,
0
3
OCH2), 6.92 (AA , 6H, m-H), 7.00 (d, J¼16.0 Hz, 3H,
a-H), 7.61 (MM0, 6H, o-H), 8.21 (d, 3J¼16.0 Hz, 3H, b-H);
13C NMR (CDCl3): d¼10.5 (CH3), 22.6 (CH2), 69.7
(OCH2), 115.0 (m-CH), 124.1 (a-CH), 128.3 (i-Cq), 129.7
(o-CH), 141.1 (b-CH), 160.7 (p-CqO), 171.4 (C-2); FD MS:
m/z (%)¼562 (100) [Mþ]. Anal. calcd for C36H39N3O3
(561.7): C, 76.98; H, 7.00; N, 7.48. Found: C, 76.83; H,
7.18; N, 7.62.
4.2.9. 2,4,6-Tris[(E)-2-(4-dodecyloxyphenyl)ethenyl]-
1,3,5-triazine (3g). Yield 86%, yellow solid, mp 63 8C.
UV (CH2Cl2): lmax¼362 nm, log 1¼5.03. 1H NMR
(CDCl3): d¼0.86 (t, 9H, CH3), 1.25 (m, 54H, CH2), 1.45
(m, 6H, CH2), 1.79 (m, 6H, CH2), 3.99 (t, 6H, OCH2), 6.92
(AA0, 6H, m-H), 7.00 (d, 3J¼16.0 Hz, 3H, a-H), 7.61 (MM0,
6H, o-H), 8.21 (d, 3J¼16.0 Hz, 3H, b-H); 13C NMR
(CDCl3): d¼14.1 (CH3), 22.6–31.9 (CH2, partly super-
imposed), 69.2 (OCH2), 114.9 (m-CH), 123.9 (a-CH), 128.1
(i-Cq), 129.7 (o-CH), 141.1 (b-CH), 160.7 (p-CqO), 171.3
(C-2); FD MS: m/z (%)¼940 (100) [Mþ], 1882 (69)
[M2þHþ]. Anal. calcd for C63H93N3O3 (940.4): C, 80.46;
H, 9.97; N, 4.47. Found: C, 80.19; H, 10.26; N, 4.51.
4.2.5. 2,4,6-Tris[(E)-2-(4-pentyloxyphenyl)ethenyl]-
1,3,5-triazine (3c). Yield 80%, yellow needles, mp
109 8C. UV (CH2Cl2): lmax¼360 nm, log 1¼5.03. 1H
NMR (CDCl3): d¼0.93 (t, 9H, CH3), 1.41 (m, 12H, CH2),
1.80 (m, 6H, CH2), 3.99 (t, 6H, OCH2), 6.920 (AA0, 6H,
m-H), 7.00 (d, 3J¼15.8 Hz, 3H, a-H), 7.60 (MM , 6H, o-H),
8.20 (d, 3J¼15.8 Hz, 3H, b-H); 13C NMR (CDCl3): d¼14.0
(CH3), 22.4, 28.2, 28.9 (CH2), 68.1 (OCH2), 114.8 (m-CH),
123.9 (a-CH), 128.1 (i-Cq), 129.7 (o-CH), 141.1 (b-CH),
160.7 (p-CqO), 171.3 (C-2); FD MS: m/z (%)¼646 (98)
[Mþ], 647 (100) [MþHþ]. Anal. calcd for C42H51N3O3
(645.9): C, 78.10; H, 7.96; N, 6.51. Found: C, 77.78; H,
8.24; N, 6.52.
4.2.10. 2,4,6-Tris[(E)-2-(3,4-dioctyloxyphenyl)ethenyl]-
1,3,5-triazine (3h). Yield 82%, green-yellow powder, Tcl
1
82 8C. UV (CH2Cl2): lmax¼376 nm, log 1¼4.99. H NMR
(DCl3): d¼0.87 (m, 18H, CH3), 1.29 (m, 48H, CH2), 1.47
(m, 12H, CH2), 1.83 (m, 12H, CH2), 4.03 (2t, 12H, OCH2),
6.88 (d, J¼8.2 Hz, phenyl-H), 6.98 (d, J¼16.0 Hz, 3H,
3
3
a-H), 7.19 (dd, 3J¼8.2 Hz, 4J¼2.0 Hz, 3H, phenyl-H), 7.23
4
3
4.2.6. 2,4,6-Tris[(E)-2-(4-hexyloxyphenyl)ethenyl]-1,3,5-
triazine (3d). Yield 55%, yellow powder, mp 96 8C. UV
(d, J¼2.0 Hz, 3H, phenyl-H), 8.18 (d, J¼16.0 Hz, 3H,
b-H); 13C NMR (CDCl3): d¼14.1 (CH3), 22.6, 26.0, 29.2,
29.3, 29.4, 31.8 (CH2, partly superimposed), 69.1 (OCH2),
69.1 (OCH2), 112.0 (m-CH), 113.0 (o-CH), 122.6 (o0-CH),
124.0 (a-CH), 128.4 (i-Cq), 141.4 (b-CH), 149.2 (m0-CqO),
151.0 (p-CqO), 171.2 (C-2); FD MS: m/z (%)¼1156 (100)
[Mþ]. Anal. calcd for C75H117N3O6 (1156.8): C, 77.87; H,
10.19; N, 3.63. Found: C, 77.72; H, 1031; N, 3.55.
1
(CH2Cl2): lmax¼361 nm, log 1¼5.02. H NMR (CDCl3):
d¼0.90 (t, 9H, CH3), 1.34 (m, 12H, CH2), 1.46 (m, 6H,
CH2), 1.79 (m, 6H, CH2), 3.99 (t, 6H, OCH2), 6.92 (AA0,
0
3
6H, m-H), 7.00 (d, J¼15.7 Hz, 3H, a-H), 7.61 (MM , 6H,
o-H), 8.20 (d, J¼15.7 Hz, 3H, b-H); 13C NMR (CDCl3):
3
d¼14.0 (CH3), 22.6, 25.7, 29.2, 31.6 (CH2), 68.2 (OCH2),
114.9 (m-CH), 124.1 (a-CH), 128.3 (i-Cq), 129.7 (o-CH),
141.1 (b-CH), 160.7 (p-CqO), 171.4 (C-2); FD MS: m/z
(%)¼688 (100) [Mþ]. Anal. calcd for C45H57N3O3 (687.9):
C, 78.56, H, 8.35, N, 6.11. Found: C, 78.33; H, 8.61; N,
5.88.
4.2.11. 2,4,6-Tris[(E)-2-(3,4,5-trihexyloxyphenyl)ethenyl]-
1,3,5-triazine (3i). Yield 79%, yellow wax, Tcl¼112 8C.
The analytical and spectroscopic data were published
earlier.8
4.2.7. 2,4,6-Tris[(E)-2-(4-heptyloxyphenyl)ethenyl]-
1,3,5-triazine (3e). Yield 64%, yellow powder, mp 85 8C.
UV (CH2Cl2): lmax¼360 nm, log 1¼5.01. 1H NMR
(CDCl3): d¼0.88 (t, 9H, CH3), 1.30 (m, 18H, CH2), 1.45
4.2.12. 2,4,6-Tris[(E)-2-(3,4,5-trioctyloxyphenyl)ethenyl]-
1,3,5-triazine (3j). Yield 87%, yellow wax, Tcl¼102 8C.
UV (CH2Cl2): lmax¼365 nm, log 1¼4.90. 1H NMR
(CDCl3): d¼0.87 (m, 27H, CH3), 1.28 (m, 82H, CH2),

6774
H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
1.48 (m, 18H, CH2), 1.74 (m, 2H, CH2), 1.82 (m, 4H, CH2),
3.99 (t, 6H, OCH2), 4.01 (t, 12H, OCH2), 6.88 (s, 6H, o-H),
22.6, 22.7 (CH3), 24.7 (CH2), 28.0, 29.6, 29.8 (CH, partly
superimposed), 36.4, 37.3, 37.5, 39.2, 39.3 (CH2, partly
superimposed), 67.4 (OCH2), 71.8 (OCH2), 106.5 (o-CH),
125.1 (a-CH), 130.5 (i-Cq), 140.1 (p-CqO), 141.8 (b-CH),
153.3 (m-CqO), 171.2 (C-2); FD MS: m/z (%)¼1794 (100)
[Mþ]. Anal. calcd for C117H201N3O9 (1793.9): C, 78.34; H,
12.29; N, 2.34. Found: C, 77.91; H, 11.95; N, 2.26.
3
3
7.00 (d, J¼15.7 Hz, 3H, a-H); 8.15 (d, J¼15.7 Hz, 3H,
b-H); 13C NMR (CDCl3): d¼14.1 (CH3), 22.7, 26.1, 29.3,
29.4, 29.5, 30.3, 31.8, 31.9 (CH2, partly superimposed), 69.1
(OCH2), 73.6 (OCH2), 106.6 (o-CH), 125.1 (a-CH), 130.5
(i-Cq), 140.1 (p-CqO), 141.8 (b-CH), 153.3 (m-CqO), 171.2
(C-2); FD MS: m/z (%)¼1541 (100) [Mþ]. Anal. calcd for
C99H165N3O9 (1541.4): C, 77.14; H, 10.79; N, 2.73. Found:
C, 77.01; H, 10.95; N, 2.62.
4.3. Irradiation of the LC phases
The Colhd phase of 3i was irradiated (l¼366 nm) on a glass
plate at 95 8C and observed with polarizing microscopy. The
change of the texture was accompanied by a continuous
4.2.13. 2,4,6-Tris[(E)-2-(3,4,5-tridecyloxyphenyl)-
ethenyl]-1,3,5-triazine (3k). Yield 69%, yellow wax,
1
1
Tcl¼90 8C. UV (CH2Cl2): lmax¼365 nm, log 1¼4.89. H
lowering of the temperature for the isotropization. The H
NMR (CDCl3): d¼0.86 (m, 27H, CH3), 1.26 (m, 108H,
CH2), 1.48 (m, 18H, CH2), 1.74 (m, 2H, CH2), 1.81 (m, 4H,
CH2), 3.99 (t, 6H, OCH2), 4.01 (t, 12H, OCH2), 6.88 (s, 6H,
NMR spectra of the irradiated probe, dissolved in CDCl3,
revealed the formation of a small amount of (E,E,Z)
configuration and the formation of0 a dimer which contains
one four-membered ring (AA0MM spin pattern at d¼4.87
and 5.27 which is assigned to a head-to-tail anti photo-
cyclodimerization).21 The irradiation of the Colhd phases of
3j–3m gives similar results, however, one has to take into
account that the normal or undercooled LC phases of these
compounds can exist at room temperature, so that they are
sensitive toward daylight.22
3
3
o-H); 7.00 (d, J¼15.7 Hz, 3H, a-H), 8.14 (d, J¼15.7 Hz,
3H, b-H); 13C NMR (CDCl3): d¼14.1 (CH3), 22.7, 26.1,
29.4, 29.6, 29.7, 30.3, 31.9 (CH2, partly superimposed), 69.1
(OCH2), 73.6 (OCH2), 106.6 (o-CH), 125.1 (a-CH), 130.5
(i-Cq), 140.1 (p-CqO), 141.8 (b-CH), 153.3 (m-CqO), 171.2
(C-2); FD MS: m/z (%)¼1795 (100) [MþHþ]. Anal. calcd
for C117H201N3O9 (1793.9): C, 78.34; H, 12.29; N, 2.34.
Found: C, 78.11; H, 12.56; N, 2.12.
4.2.14. 2,4,6-Tris[(E)-2-(3,4,5-tridodecyloxyphenyl)-
ethenyl]-1,3,5-triazine (3l). Yield 82%, yellow wax,
Acknowledgements
1
Tcl¼90 8C. UV (CH2Cl2): lmax¼366 nm, log 1¼4.90. H
We are grateful to the Deutsche Forschungsgemeinschaft
and the Fonds der chemischen Industrie for financial
support.
NMR (CDCl3): d¼0.86 (m, 27H, CH3), 1.25 (m, 144H,
CH2), 1.48 (m, 18H, CH2), 1.74 (m, 6H, CH2), 1.82 (m,
12H, CH2), 3.99 (t, 6H, OCH2), 4.01 (t, 12H, OCH2), 6.88
3
3
(s, 6H, o-H), 7.00 (d, J¼15.7 Hz, 3H, a-H), 8.15 (d, J¼
15.7 Hz, 3H, b-H); 13C NMR (CDCl3): d¼14.1 (CH3), 22.7,
26.1, 29.4, 29.6, 29.7, 30.4, 31.9 (CH2, partly super-
imposed), 69.2 (OCH2), 73.6 (OCH2), 106.6 (o-CH), 125.1
(a-CH), 130.5 (i-Cq), 140.1 (p-CqO), 141.8 (b-CH), 153.3
(m-CqO), 171.1 (C-2); FD MS: m/z (%)¼2047 (100) [Mþ].
Anal. calcd for C135H237N3O9 (2046.4): C, 79.24; H, 11.67;
N, 2.05. Found: C, 79.23; H, 11.55; N, 2.08.
References and notes
1. Wolff, J. J.; Siegler, F.; Matschiner, R.; Wortmann, R. Angew.
Chem. 2000, 112, 1494. (b) Wolff, J. J.; Siegler, F.;
Matschiner, R.; Wortmann, R. Angew. Chem. Int. Ed. 2000,
39, 1436.
¨
2. Wortmann, R.; Glania, C.; Kramer, P.; Matschiner, R.; Wolff,
¨ ¨
J. J.; Kraft, S.; Treptow, B.; Barbu, E.; Langle, D.; Gorlitz, G.
4.2.15. 2,4,6-Tris[(E)-2-(3,4,5,-trihexadecyloxyphenyl)-
ethenyl]-1,3,5-triazine (3m). Yield 89%, yellow wax,
Chem. Eur. J. 1997, 3, 1765.
1
Tcl¼80 8C. UV (CH2Cl2): lmax¼367 nm, log 1¼4.90. H
3. Ray, P. C.; Das, P. K. Chem. Phys. Lett. 1995, 244, 153.
4. Kim, K. Pohang University of Science and Technology,
Korea. Private communication.
NMR (CDCl3): d¼0.85 (m, 27H, CH3), 1.24 (m, 216H,
CH2), 1.48 (m, 18H, CH2), 1.75 (m, 6H, CH2), 1.82 (m,
12H, CH2), 3.99 (t, 6H, OCH2), 4.01 (t, 12H, OCH2), 6.88
5. Lee, C.-H.; Yamamoto, T. Bull. Chem. Soc. Jpn 2002, 615.
6. Lee, C.-H.; Yamamoto, T. Tetrahedron Lett. 2001, 42, 3993.
7. Pieterse, K.; Lauritsen, A.; Schenning, A. P. H. J.; Vekemans,
J. A. J. M.; Meijer, E. W. Chem. Eur. J. 2003, 5597.
8. Meier, H.; Holst, H. C.; Oehlhof, A. Eur. J. Org. Chem. 2003,
4173.
3
3
(s, 6H, o-H), 7.01 (d, J¼15.7 Hz, 3H, a-H), 8.15 (d, J¼
15.7 Hz, 3H, b-H); 13C NMR (CDCl3): d¼14.1 (CH3), 22.7,
26.1, 29.4, 29.6, 29.7, 30.3, 31.9 (CH2, partly super-
imposed), 69.1 (OCH2), 73.6 (OCH2), 106.6 (o-CH), 125.1
(a-CH), 130.5 (i-Cq), 140.1 (p-CqO), 141.8 (b-CH), 153.3
(m-CqO), 171.2 (C-2); FD MS: m/z (%)¼2552 (100) [Mþ].
Anal. calcd for C171H309N3O9 (2551.3): C, 80.50; H, 12.21;
N, 1.65. Found: C, 80.27; H, 12.48; N, 1.38.
9. Fischbach, I.; Pakula, T.; Minkin, P.; Fechtenkotter, A.;
Mu¨llen, K.; Spiess, H. W.; Saalwachter, K. J. Phys. Chem. B
2002, 106, 6408.
10. Pakula, T. Unpublished modelling results.
11. Pakula, T.; Vlassopoulos, D.; Fytas, G.; Roovers, J. Macro-
4.2.16. 2,4,6-Tris{(E)-2[3,4,5-tris(3,7-dimethyloctyl)-
phenyl]ethenyl}-1,3,5-triazine (3n). Yield 85%, yellow
wax, Tcl¼45 8C. UV (CH2Cl2): lmax¼366 nm, log 1¼4.77.
1H NMR (CDCl3): d¼0.85 (m, 54H, CH3), 0.94 (m, 27H,
CH3), 1.10–1.95 (m, 90H, CH2 and CH), 4.04 (m, 18H,
molecules 1998, 31, 8931.
12. A calculation of the AA0MM0 spin pattern of the protons at the
four-membered ring led to the assignment of a head-to-tail
dimer, in which the two heads as well as the two tails adopt a
trans position to each other. The original trans arrangement of
head and tail in 3i is preserved in the cycloadduct. A detailed
3
OCH2), 6.90 (s, 6H, o-H), 7.03 (d, J¼15.7 Hz, 3H, a-H),
8.17 (d, 3J¼15.7 Hz, 3H, b-H); 13C NMR (CDCl3): d¼19.6,

H. C. Holst et al. / Tetrahedron 60 (2004) 6765–6775
6775
description of the photodimerization shall be published
elsewhere.
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22. In the absence of a topochemically controlled reaction in the
crystalline state, the enhanced molecular mobility in the LC
phases is a precondition for the photodimerization.
17. Strzelecka, H.; Jallabert, C.; Veber, M.; Davidson, P.; Levelut,
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