Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

Article abstract of DOI:10.3762/bjoc.5.63

Based on 5-(4-hydroxyphenyl)-2-octylpyrimidine 8, 5-phenylpyrimidine derivatives 3-9 with different spacer chain lengths (C₂ up to C ₆) and different terminal polar groups (Br, Cl, N₃, OH, CN) were synthesized by etherific

Full text of DOI:10.3762/bjoc.5.63

Influence of spacer chain lengths and polar terminal
groups on the mesomorphic properties of tethered
5-phenylpyrimidines
Gundula F. Starkulla1, Elisabeth Kapatsina1, Angelika Baro1,
Frank Giesselmann2, Stefan Tussetschläger1, Martin Kaller1
and Sabine Laschat*1
Full Research Paper
Open Access
Address:
Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
1Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring
55, 70569 Stuttgart, Germany and 2Institut für Physikalische Chemie,
Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
doi:10.3762/bjoc.5.63
Received: 31 July 2009
Accepted: 19 October 2009
Published: 09 November 2009
Email:
Sabine Laschat* - sabine.laschat@oc.uni-stuttgart.de
Guest Editor: S. Laschat
* Corresponding author
© 2009 Starkulla et al; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
calamitic; liquid crystals; 5-phenylpyrimidines
Abstract
Based on 5-(4-hydroxyphenyl)-2-octylpyrimidine 8, 5-phenylpyrimidine derivatives 3–7, 9 with different spacer chain lengths (C2
up to C6) and different terminal polar groups (Br, Cl, N3, OH, CN) were synthesized by etherification and nucleophilic substitution.
The mesomorphic behaviour of these compounds was investigated by differential scanning calorimetry (DSC), polarizing optical
microscopy (POM) and X-ray diffraction (WAXS and SAXS) and revealed smectic A mesophases for bromides, chlorides and
azides 3, 4 and 6. For these compounds a maximum phase width was observed for the C5 spacer regardless of the terminal group,
whereas the hydroxy- and cyano-substituted derivatives 5 and 7, respectively, were non mesomorphic and showed only melting
transitions.
Introduction
A tremendous amount of work has been done on calamitic
liquid crystals, which has led to applications in the field of LC
displays [1]. Among the large family of various calamitic meso-
gens 2-alkoxy-5-phenylpyrimidines 1 are prominent members
due to the fact that the two nitrogen atoms increase the polarity
of the rigid rod core structure (Scheme 1) as exemplified by the
Scheme 1: Comparison of mesomorphic properties of 1a and 2a.
derivative 1a which displays a SmA phase between 45 °C and
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
71 °C, while the corresponding biphenyl derivative 2a with the octylpyrimidine 8 using K2CO3 in MeCN under reflux for 12 h
same terminal alkyl chains does not have any liquid crys- to yield 39%. The synthesis of series 4 with chloride as terminal
tallinity [1].
group proceeded in a similar way by using 1,ω-dichloroalkanes
giving 4a–e in 31–70% yield. Upon deprotonation of 8 under
Whereas three regioisomeric phenylpyrimidines are possible, the conditions described above, followed by treatment with
i.e. 4-, 5-, and 2-phenylpyrimidine, only the latter two are suit- 5-bromopentanol or 6-bromohexanol, the hydroxy compounds
able for liquid crystals. Furthermore 5- and 2-phenyl- 5d and 5e were isolated in 76% and 80% yield, respectively. To
pyrimidines differ in their overall conformation. According to obtain the azides 6, bromides 3a–e were treated with NaN3 in
ab initio calculation by Barone [2], 2-phenylpyrimidine is DMF at 100 °C for 24 h and the products 6a–e were isolated in
almost planar, whereas 5-phenylpyrimidine has a twisted 74% up to quantitative yield (Scheme 4). In a similar manner,
conformation with a dihedral angle of 43.1° [3]. The different the cyanides 7 were prepared from the bromides 3. Treatment of
conformations together with differences of the polarisation and the bromides 3c–e with KCN in EtOH/H2O at 110 °C for 12 h
dipole moment between 2- and 5-phenylpyrimidines also lead to leads to the cyanides 7c–e in 72 to 97% yield.
different mesomorphic properties as was shown by Lemieux for
phenylpyrimidines tethered to terminal trisiloxanes [4,5] and by Since the yields of 3b were limited due to side reactions like
Tschierske for dimeric phenylpyrimidines tethered to elimination, the respective cyanide 7b was prepared by depro-
oligoethyleneglycol units [6].
tonation of hydroxy derivative 8 with NaH in DMF for 40 min
at 0 °C followed by addition of 1-bromo-3-propionitrile at room
We recently reported the synthesis of 1,1′-biisoquinolines temperature. After 12 h, the cyanide 7b was obtained in 33%
tethered to calamitic subunits [7]. During these studies we yield.
discovered that the 5-phenylpyrimidine building block 3e
already displayed a SmA mesophase. We thus wondered Mesomorphic properties: Mesomorphic properties of com-
whether variation of the spacer chain lengths and terminal pounds 3–10 were investigated by differential scanning calori-
group X (Scheme 2) might have significant influence on the metry (DSC), polarizing optical microscopy (POM) and X-ray
mesomorphism. The results of this study are discussed below. diffraction (WAXS and SAXS). The DSC results for bromides
3 are summarized in Table 1.
Results and Discussion
Syntheses: In order to obtain different series 3–7 the known Whereas compounds 3a,c,e with even chain lengths of the
5-(4-hydroxyphenyl)-2-octylpyrimidine 8 [7-12] was used as spacer displayed monotropic SmA phases, compounds 3b,d
starting material (Scheme 3).
with odd chain lengths displayed enantiotropic SmA phases. A
typical DSC curve of derivative 3d with a pentyloxy spacer is
Compound 8 was deprotonated with KOH in DMSO at room shown in Figure 1.
temperature for 10 min followed by addition of 1,ω-dibromo-
alkane. After 4 h, the reaction mixtures were purified and the On the third heating a melting transition at 40 °C into the SmA
desired bromides 3b–e were isolated in 23 up to 60% yield. phase and a clearing transition at 57 °C could be observed.
When 1,3-dibromopropane was used, 27% of the elimination Subsequent cooling revealed an isotropic to SmA transition at
product 9 was isolated as byproduct. For comparison the corre- 60 °C and a crystallization peak at 24 °C. The SmA to crystal-
sponding 4-allyloxy-4′-octylbiphenyl 11 was prepared in 49% line transition tends to strong supercooling in the order of 10–30
yield by allylation of 4-hydroxy-4′-octylbiphenyl. Compound K (Table 1, Figure 1).
3a was obtained by etherification of 5-(4-hydroxyphenyl)-2-
Scheme 2: Variation of spacer lengths and terminal group at 5-phenylpyrimidine.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
Scheme 3: Synthesis of compounds 3–5, 9 and 11.
POM observation of 3a–e revealed fan-shaped textures typical smectic A phase and a clearing transition at 66 °C upon a
of SmA phases. An illustrative example is depicted in Figure 2. second heating. Upon the second cooling run an isotropic to
The assignment of the SmA mesophases was further confirmed SmA transition at 64 °C and a crystallization peak at 42 °C were
by XRD experiments (see the Supporting Information).
observed.
It should be noted that the allyloxy-substituted byproduct 9 POM investigation displayed fan-shaped and focal conic
showed a smectic mesophase between 50 °C and 67 °C as well. textures, as exemplified in Figure 4. XRD experiments proved
In contrast, the corresponding 4-allyloxy-4′-octylbiphenyl 11 the smectic phase.
showed only isotropic melting at 92 °C. The DSC results of
chlorides 4 are summarized in Table 2.
In contrast to the bromides 3 and chlorides 4, the hydroxy and
azide derivatives 5a,b and 7b–e were non mesomorphic and
All members 4a–e showed enantiotropic SmA phases. For com- showed only melting transitions at 76 °C and 75 °C for com-
pounds 4a,c,e with even numbered spacer lengths smaller meso- pounds 5a,b and at 77 °C, 86 °C, 67 °C and 68 °C for the azides
phase widths were observed as compared to compounds 4b,d 7b–e, respectively (upon heating or cooling) in the DSC curve.
with odd numbered spacer lengths. Furthermore an odd–even Presumably, the higher polarity of the terminal hydroxy group
effect of both melting and clearing points was found. A typical with respect to the azido group, together with hydrogen
DSC curve which is shown in Figure 3 for chloride 4e with bonding, inhibits mesophase formation. Next the azides 6 were
hexyloxy spacer, revealed a melting transition at 59 °C to the investigated by DSC (Table 3).
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
Scheme 4: Synthesis of compounds 6 and 7.
Table 1: Phase transition temperatures [°C] and enthalpies [kJ/mol] of compounds 3.a
3
a
n
Cr1
T
ΔH
Cr2
T
ΔH
SmA
T
ΔH
I
2
•
•
•
•
•
•
•
•
•
•
52
29
46
35
66
49
40
24
64
35
3.9
−25.8
13.0
•
-
-
-
-
-
-
-
-
-
63
-
32.2
-
•
•
•
-
•
•
•
-
•
-
-
−5.6
1.9
−3.2
-
•
•
•
•
•
•
•
•
•
•
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
-
-
-
-
-
-
-
-
-
56
52
52
-
b
c
d
e
3
4
5
6
-
−13.9
31.1
-
-
−24.1
17.6
-
63
57
60
-
−5.0
5.1
−5.3
-
-
−16.7
36.3
-
-
−23.9
-
58
−5.5
aCr crystalline; SmA smectic A; I isotropic; • phase was observed; - phase was not observed. Heating and cooling rate: 10 K/min.
Whereas compound 6a with an ethoxy spacer was non meso- halides (n = 2, 5, 6) have a lower tendency to supercooling.
morphic, enantiotropic SmA phases were detected for all other Whereas for azides 6 the broadest mesophase was observed for
chain lengths 6b–e. Compound 6d showed an additional crystal C5 spacer (6d), for chlorides 4 derivatives 4b and 4d with C3
to crystal transition. A typical DSC curve of derivative 6c is and C5 spacer displayed similar mesophase width. For bro-
shown in Figure 5. POM revealed fan-shaped and focal conic mides 3 again the derivative 3d with C5 spacer showed the
texture, see for example Figure 6. Figure 7 and Figure 8 reveal broadest mesophase.
that due to substantial supercooling for all spacer chain lengths
and terminal groups the mesophases are smaller during the
heating cycle as compared to the cooling cycle. The broadest
mesophase was observed for the azide derivative 6d with ΔT =
27 °C upon heating and ΔT = 45 °C upon cooling. In compar-
ison to the compounds with an azide as terminal group the
From the X-ray data, the following model (Figure 9) of the
layer structure is proposed. The d values obtained from the
X-ray experiments fit with the molecular lengths derived from
simple molecular modelling (Chem3D) [13]. For example, the
XRD pattern of the azide derivative 6c results in a layer dis-
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
Figure 1: DSC curve of compound 3d (heating/cooling rate 10 K/min).
tance of 25.5 Å, whereas the calculated length of the molecule
for the most elongated conformation is 26 Å, which is clear
evidence for the presence of monolayers. This leads to the
assumption that the molecules might be aligned antiparallel
within each smectic layer (Figure 9). Packing the molecules in
this array prevents close contacts between the polar regions of
the rigid core and the terminal groups. The observed maximum
phase width for the C5 spacer regardless of the terminal group
suggests that for this chain length space filling is optimal and
the terminal group X can be accommodated well between the
alkyl chains. This model might also explain why the meso-
phase is lost with strongly polar or hydrogen bonding terminal
groups such as cyanides and hydroxy derivatives.
Conclusion
Figure 2: Fan-shaped texture of 3e under crossed polarizers upon
cooling from the isotropic liquid (magnification 200×): at 55 °C (cooling
rate 5 K/min): smectic A phase.
It has been shown that 5-phenylpyrimidine derivatives with
terminal chloro-, bromo-, azido-, hydroxy- and cyano groups
Table 2: Phase transition temperatures [°C] and enthalpies [kJ/mol] of compounds 4.a
4
a
n
Cr
T
ΔH
SmA
T
ΔH
I
2
•
•
•
•
•
•
•
•
•
•
50
25
37
23
63
46
42
27
55
42
21.6
−18.7
11.9
•
•
•
•
•
•
•
•
•
•
55
53
53
58
67
70
56
62
59
64
1.4
−1.5
3.9
•
•
•
•
•
•
•
•
•
•
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
b
c
d
e
3
4
5
6
−11.8
21.9
−4.2
2.7
−23.5
15.7
−4.9
5.0
−17.0
20.8
−4.8
4.7
−25.3
−4.5
aCr crystalline; SmA smectic A; I isotropic; • phase was observed; - phase was not observed. Heating and cooling rate: 10 K/min for 4a–d, 5 K/min for
4e.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
Figure 3: DSC curve of compound 4e (heating/cooling rate 5 K/min).
separated by an alkoxy spacer chain from the aromatic core
were easily synthesised by nucleophilic substitution. Depending
on the terminal group and the tether lengths the formation of
smectic A mesophases was observed for the chloro-, bromo-
and azido derivatives. Surprisingly, the strong latent dipole
moment of hydroxy and cyano derivatives and the ability of
hydroxy derivatives to form hydrogen bonds seems to
completely suppress the formation of mesophases. Furthermore,
the polar pyrimidine ring seems to play an important role in
promoting liquid crystalline properties.
Experimental
General
Melting points were measured on a Mettler Toledo DSC822 and
are uncorrected. NMR spectra were recorded on a Bruker
Avance 300 and Avance 500 spectrometer. FT-IR spectra were
recorded on a Bruker Vektor22 spectrometer with MKII Golden
Figure 4: Fan-shaped texture of compound 4d at 45 °C upon cooling
from the isotropic liquid (cooling rate 1 K/min) (magnification 200×).
Table 3: Phase transition temperatures [°C] and enthalpies [kJ/mol] of compounds 6.a
6
a
n
Cr1
T
ΔH
Cr2
T
ΔH SmA
T
ΔH
I
2
•
•
•
•
•
•
•
•
•
•
48
44
45
34
42
28
7
30.6
−31.4
11.9
-
-
-
-
-
-
•
•
-
•
-
-
-
-
-
•
•
•
•
•
•
•
•
-
-
-
•
•
•
•
•
•
•
•
•
•
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
2. heating
2. cooling
-
-
b
c
d
e
3
4
5
6
-
-
49
47
60
63
55
57
53
58
1.1
−13.7
25.3
-
-
−2.9
5.0
-
-
-
−17.8
0.9
-
−5.3
3.4
28
11
-
17.2
−16.0
-
1
−0.6
−4.7
6.1
41
20
26.5
−22.2
25
−0.5
−5.9
aCr crystalline; SmA smectic A; I isotropic; • phase was observed; - phase was not observed. Heating and cooling rate: 10 K/min.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
Figure 5: DSC curve of compound 6c (heating/cooling rate 10 K/min).
Gate Single Reflection Diamant ATR system. Mass spectra
were recorded on a Finnigan MAT 95 and a Varian MAT 711
apparatus. X-Ray powder experiments were performed on a
Bruker Nanostar; software: SAXS 4.1.26. The samples were
kept in Hilgenberg glass capillaries of 0.7 mm outside diameter
in a temperature-controlled heating stage (±1 °C). A monochro-
matic Cu-Kα1 beam (λ = 1.5405 Å) was obtained using a
ceramic tube generator (1500 W) with cross-coupled Göbel-
mirrors as the monochromator. The diffraction patterns were
recorded on a real-time 2D-detector (HI-STAR, Bruker). The
calibration of the patterns occurred with the powder pattern of
Ag-Behenate. Differential scanning calorimetry (DSC) was
performed using a Mettler Toledo DSC822, and polarizing
optical microscopy (POM) using an Olympus BX50 polarizing
microscope combined with a Linkam LTS350 hot stage and a
Linkam TP93 central processor. Flash chromatography was
Figure 6: Fan-shaped texture of compound 6e at 45 °C upon cooling
from the isotropic liquid (cooling rate 10 K/min) (magnification 200×).
Figure 7: Comparison of the mesophase range ΔT for the different spacer lengths of compounds 3, 4 and 6: mesophase range upon heating (heating
rate 10 K/min).
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
Figure 8: Comparison of the mesophase range ΔT for the different spacer lengths of compounds 3, 4 and 6: mesophase range upon cooling (cooling
rate 10 K/min).
performed using Kieselgel 60, 40–63 μm (Fluka). All solvents
were dried, and reactions were performed in dried glassware.
The used petroleum ether (PE) had a boiling range of 30–75 °C.
General procedure 1
To a solution of 5-(4-hydroxyphenyl)-2-octylpyrimidine 8
(852 mg, 3.00 mmol) in 4 mL DMSO was added powdered
KOH (504 mg, 9.00 mmol). After stirring for 10 min at room
temperature, the α,ω-dihaloalkane (or α-bromo-ω-alkanol
respectively) (3.00 mmol) was added. Stirring was continued
for 4 h followed by quenching with 20 mL H2O and 100 mL
CH2Cl2. The organic layer was dried (Na2SO4) and the solvents
were evaporated. Finally the crude product was purified by
flash chromatography.
General procedure 2
A solution of bromide 3 (0.50 mmol) and NaN3 (81.0 mg,
1.25 mmol) in 15 mL DMF was stirred at 100 °C for 24 h. After
cooling to room temperature, the reaction mixture was treated
with 20 mL H2O and extracted with CH2Cl2 (3 × 30 mL). The
combined organic layers were dried (Na2SO4), the solvent was
evaporated and the crude product purified by flash chromato-
graphy.
General procedure 3
A solution of bromide 3 (0.50 mmol) and KCN (35.8 mg,
0.55 mmol) in 4 mL EtOH/H2O (3:1, v/v) was stirred at 110 °C
for 12 h. After cooling to room temperature, 10 mL CH2Cl2
were added and the aqueous layer was extracted with CH2Cl2
(3 × 10 mL). The combined organic layers were washed with
1 N NaOH (1 × 10 mL) and dried (Na2SO4). Finally the solvent
was evaporated and the crude product purified by flash chroma-
Figure 9: Proposed model for the layer structure.
tography.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
5-[4-(6-Bromohexyloxy)phenyl]-2-
octylpyrimidine (3e)
5-[4-(6-Hydroxyhexyloxy)phenyl]-2-
octylpyrimidine (5e)
Prepared according to general procedure (1). Experiment: Prepared according to general procedure (1). Experiment:
284 mg (1.00 mmol) 5-(4-hydroxyphenyl)-2-octylpyrimidine 8, 568 mg (2.00 mmol) 5-(4-hydroxyphenyl)-2-octylpyrimidine 8,
160 μL (245 mg, 1.00 mmol) 1,6-dibromohexane, 168 mg 270 μL (362 mg, 2.00 mmol) 6-bromohexane-1-ol, 336 mg
(3.00 mmol) KOH. Flash chromatography (PE/EtOAc, 4:1, v/v; (6.00 mmol) KOH. Flash chromatography (PE/EtOAc, 1:1, v/v;
Rf = 0.86: PE/EtOAc, 1:1, v/v) gave 268 mg (0.60 mmol, 60%) Rf = 0.29) gave 615 mg (1.60 mmol, 80%) of 5e as a colourless
of 3e as a colourless crystalline solid. DSC: Cr 35 °C [−23.9 kJ/ crystalline solid. Mp: 75 °C. 1H NMR (300 MHz, CDCl3): δ =
mol] (SmA 58 °C [−5.5 kJ/mol]) I. 1H NMR (300 MHz, 0.85–0.90 (m, 3H, CH3), 1.24–1.68 (m, 16H, CH2), 1.79–1.90
CDCl3): δ = 0.88 (t, 3H J = 6.9 Hz, CH3), 1.21–1.45 (m, 10H, (m, 4H, CH2), 2.96–3.01 (m, 2H, 2-CH2), 3.68 (t, 2H, J =
CH2), 1.49–1.58 (m, 4H, CH2), 1.79–1.98 (m, 6H, CH2), 6.5 Hz, CH2OH), 4.01 (t, 2H, J = 6.5 Hz, OCH2), 6.99–7.04 (m,
2.96–3.01 (m, 2H, 2-CH2), 3.44 (t, 2H, J = 6.6 Hz, CH2Br), 2H, 3′-H, 5′-H), 7.46–7.51 (m, 2H, 2′-H, 6′-H), 8.83 (s, 2H,
4.02 (t, 2H, J = 6.4 Hz, OCH2), 6.99–7.03 (m, 2H, 3′-H, 5′-H), 4-H, 6-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (CH3),
7.46–7.50 (m, 2H, 2′-H, 6′-H), 8.83 (s, 2H, 4-H, 6-H) ppm. 22.7, 25.6, 25.9, 28.9, 29.2, 29.5, 31.9, 32.7 (CH2), 39.2
13C NMR (125 MHz, CDCl3): δ = 14.1 (CH3), 22.7, 25.3, 27.9, (2-CH2), 62.8 (CH2OH), 68.0 (OCH2), 115.3 (C-3′, C-5′), 127.9
28.9, 29.0, 29.2, 29.4, 31.9, 32.7, 33.8 (CH2), 39.2 (2-CH2), (C-2′, C-6′), 126.6, 130.8 (C-1’, C-5), 154.5 (C-4, C-6), 159.7
67.9 (OCH2), 115.2 (C-3′, C-5′), 128.0 (C-2′, C-6′), 126.7, (C-4′), 169.6 (C-2) ppm. FT-IR (ATR): = 3303 (m, br), 2917
130.8 (C-1′, C-5), 154.8 (C-4, C-6), 159.9 (C-4′), 169.5 (C-2) (s), 2848 (m), 1606 (m), 1586 (m), 1536 (m), 1516 (m), 1466
ppm. FT-IR (ATR): = 2916 (m), 2848 (m), 1586 (m), 1536 (m), 1445 (s), 1377 (m), 1291 (m), 1288 (m), 1248 (s), 1181
(m), 1515 (m), 1445 (s), 1247 (s), 1180 (m), 1116 (m), 1011 (m), 1118 (m), 1060 (m), 1007 (m), 994 (m), 918 (m), 838 (s),
(m), 994 (m), 838 (s), 651 (m), 608 (m) cm−1. MS (EI, 70eV): 707 (m), 652 (m) cm−1. MS (EI, 70eV): m/z (%) = 384.3 (100)
m/z (%) = 446.1 (100) [M]+, 361.0 (20) [M−C6H13]+, 348.0 [M]+, 299.2 (36), 286.2 (94). HRMS (ESI): m/z [M+H]+ calcd.
(78) [M + H−C7H15], 199.0 (10) 186.0 (28). C24H35BrN2O for C24H37N2O2: 385.2850; found: 385.2856. C24H36N2O2
(447.45): calcd. C 64.42, H 7.88, N 6.26, Br 17.86; found C (384.55): calcd. C 74.96, H 9.44, N 7.28; found C 75.05, H
64.46, H 7.88, N 6.14, Br 17.61.
9.27, N 7.26.
5-[4-(6-Chlorohexyloxy)phenyl]-2-
5-[4-(6-Azidohexyloxy)phenyl]-2-
octylpyrimidine (4e)
octylpyrimidine (6e)
Prepared according to general procedure (1). Experiment: Prepared according to general procedure (2). Experiment:
85.0 mg (0.30 mmol) 5-(4-hydroxyphenyl)-2-octylpyrimidine 8, 224 mg (0.50 mmol)) bromide 3e, 81.0 mg (1.25 mmol) NaN3.
45.0 μL (47.0 mg, 0.30 mmol) 1,6-dichlorohexane, 50.0 mg Flash chromatography (PE/EtOAc, 2:1, v/v; Rf = 0.56) gave
(0.90 mmol) KOH. Flash chromatography (PE/EtOAc, 5:1, v/v; 205 mg (0.50 mmol, quant.) of 6e as a colourless crystalline
Rf = 0.40: PE/EtOAc, 3:1, v/v) gave 74.0 mg (0.18 mmol, 60%) solid. DSC: Cr1 20 °C [−22.2 kJ/mol] Cr2 25 °C [−0.5 kJ/mol]
of 4e as a colourless crystalline solid. DSC: Cr 42 °C [−25.3 kJ/ SmA 58 °C [−5.9 kJ/mol] I. 1H NMR (300 MHz, CDCl3): δ =
mol] SmA 64 °C [−4.5 kJ/mol] I. 1H NMR (300 MHz, CDCl3): 0.85–0.90 (m, 3H, CH3), 1.24–1.58 (m, 14H, CH2), 1.60–1.71
δ = 0.85–0.90 (m, 3H, CH3), 1.23–1.44 (m, 10H, CH2), (m, 2 H, CH2), 1.78–1.91 (m, 4H, CH2), 2.97–3.01 (m, 2H,
1.50–1.55 (m, 4H, CH2), 1.78–1.90 (m, 6H, CH2), 2.96–3.01 2-CH2), 3.30 (t, 2H, J = 6.8 Hz, CH2N3), 4.02 (t, 2H, J = 6.4
(m, 2H, 2-CH2), 3.56 (t, 2H, J = 6.7 Hz, CH2Cl), 4.01 (t, 2H, J Hz, OCH2), 7.00–7.04 (m, 2H, 3′-H, 5′-H), 7.47–7.51 (m, 2H,
= 6.4 Hz, OCH2), 6.99–7.04 (m, 2H, 3′-H, 5′-H), 7.46–7.51 (m, 2′-H, 6′-H), 8.83 (s, 2H, 4-H, 6-H) ppm. 13C NMR (75 MHz,
2H, 2′-H, 6′-H), 8.83 (s, 2H, 4-H, 6-H) ppm. 13C NMR CDCl3): δ = 14.1 (CH3), 22.7, 25.7, 26.5, 28.8, 28.9, 29.1, 29.2,
(75 MHz, CDCl3): δ = 14.1 (CH3), 22.7, 25.4, 26.6, 28.8, 29.1, 29.5, 31.9 (CH2), 39.2 (2-CH2), 51.4 (CH2N3), 67.9 (OCH2),
29.2, 29.4, 31.9, 32.5 (CH2), 39.2 (2-CH2), 45.0 (CH2Cl), 67.9 115.3 (C-3′, C-5′), 127.9 (C-2′, C-6′), 126.7, 130.8 (C-1’, C-5),
(OCH2), 115.3 (C-3′, C-5′), 127.9 (C-2′, C-6′), 126.7, 130.8 154.5 (C-4, C-6), 159.6 (C-4′), 169.6 (C-2) ppm. FT-IR (ATR):
(C-1′, C-5), 154.5 (C-4, C-6), 159.6 (C-4′), 169.6 (C-2) ppm.
= 2921 (s), 2847 (m), 2091 (s), 1605 (m), 1587 (m), 1467
FT-IR (ATR): = 2917 (m), 2849 (m), 1587 (m), 1516 (m), (m), 1446 (s), 1287 (m), 1246 (s), 1182 (m), 1032 (m), 993 (m),
1446 (s), 1392 (m), 1287 (m), 1246 (s), 1181 (m), 1116 (m), 836 (s), 654 (m) cm−1. MS (ESI): m/z = 432.3 [M + Na]+, 410.3
1029 (m), 994 (m), 941 (m), 838 (m), 721 (m) cm−1. MS (ESI): [M + H]+. C24H35N5O (409.58): calcd. C 70.38, H 8.61, N
m/z = 403.3 [M + H]+, 367.3 [M–Cl]+. C24H35ClN2O (403.00): 17.10; found C 70.51, H 8.55, N 17.05.
calcd. C 71.53, H 8.75, N 6.95, Cl 8.80; found C 71.38, H 8.63,
N 6.81, Cl 8.93.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 63.
5-[4-(6-Cyanohexyloxy)phenyl]-2-
octylpyrimidine (7e)
3. Barone, V.; Commisso, L.; Lelj, F.; Russo, N. Tetrahedron 1985, 41,
1915–1918. doi:10.1016/S0040-4020(01)96554-8
4. Li, L.; Jones, C. D.; Magolan, J.; Lemieux, R. P. J. Mater. Chem. 2007,
17, 2313–2318. doi:10.1039/b700972k
Prepared according to general procedure (3). Experiment:
224 mg (0.50 mmol) bromide 3e, 36.0 mg (0.55 mmol) KCN.
Flash chromatography (PE/EtOAc, 4:1, v/v; Rf = 0.23) gave
142 mg (0.36 mmol, 72%) of 7e as a colourless crystalline
solid. Mp: 68 °C. 1H NMR (500 MHz, CDCl3): δ = 0.88 (t, 3H
J = 6.9 Hz, CH3), 1.20–1.45 (m, 10H, CH2), 1.51–1.60 (m, 4H,
CH2), 1.68–1.90 (m, 6H, CH2), 2.37 (t, 2H, J = 7.3 Hz,
CH2CN), 2.96–3.01 (m, 2H, 2-CH2), 4.02 (t, 2H, J = 6.3 Hz,
OCH2), 6.99–7.03 (m, 2H, 3′-H, 5′-H), 7.46–7.51 (m, 2H, 2′-H,
6′-H), 8.81 (s, 2H, 4-H, 6-H) ppm. 13C NMR (125 MHz,
CDCl3): δ = 14.1 (CH3), 17.1, 22.7, 25.3, 25.4, 28.4, 28.9, 29.2,
29.5, 31.9 (CH2), 39.2 (2-CH2), 67.9 (OCH2), 115.4 (C-3′,
C-5′), 119.7 (CN), 128.0 (C-2′, C-6′), 126.9, 130.8 (C-1’, C-5),
154.5 (C-4, C-6), 159.6 (C-4′), 169.7 (C-2) ppm. FT-IR (ATR):
= 3035 (w), 2950 (m), 2920 (m), 2852 (m), 1608 (m) 1588
(m), 1541 (m), 1518 (m), 1440 (s), 1397 (m), 1245 (s), 1188 (s),
1048 (m), 996 (m), 836 (s), 738 (m), 706 (m), 652 (m), 556 (m)
cm−1. MS (EI, 70eV): m/z (%) = 393.2 (72) [M]+, 350.2 (8),
308.2 (28), 395.2 (100), 185.1 (11). HRMS (ESI): m/z [M+H]+
calcd. for C25H36N3O: 394.2853; found: 394.2854. C25H35N3O
(393.56): calcd. C 76.29, H 8.96, N 10.68; found C 76.15, H
8.93, N 10.51.
5. Roberts, J. C.; Kapernaum, N.; Giesselmann, F.; Lemieux, R. P.
J. Am. Chem. Soc. 2008, 130, 13842–13843. doi:10.1021/ja805672q
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Tschierske, C. J. Mater. Chem. 2003, 13, 778–784.
doi:10.1039/b210271d
7. Kapatsina, E.; Lordon, M.; Baro, A.; Laschat, S. Synthesis 2008,
2551–2560. doi:10.1055/s-2008-1067184
8. Lloyd, D.; Reichardt, C.; Struthers, M. Liebigs Ann. Chem. 1986,
1368–1379. doi:10.1002/jlac.198619860807
9. Dox, A. W. Org. Synth. 1941, 1, 5–6.
10.Hooley, R. J.; Rebek, J. Org. Lett. 2007, 9, 1179–1182.
doi:10.1021/ol062782s
11.Sugita, S.-I.; Toda, S.; Yoshiyasu, T.; Teraji, T.; Murayama, A.
Mol. Cryst. Liq. Cryst. 1994, 239, 113–122.
doi:10.1080/10587259408047176
12.Sugita, S.-I.; Takeno, H.; Teraji, T. Mol. Cryst. Liq. Cryst. 1991, 206,
139–146. doi:10.1080/00268949108037726
13.Chem3D Pro 2008 software was used for molecular modelling.
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permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
Supporting Information
Supporting information includes experimental and
spectroscopic data for compounds 4a–d, 5d, 6a–d, 7a–d, 9,
11 and X-ray diffraction data.
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
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Supporting Information File 1
Analytical data of compounds 4a–d, 5d, 6a–d, 7a–d, 9, 11.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-5-63-S1.pdf]
The definitive version of this article is the electronic one
which can be found at:
doi:10.3762/bjoc.5.63
Acknowledgments
Generous financial support by the Deutsche Forschungsge-
meinschaft, the Ministerium für Wissenschaft, Forschung und
Kunst des Landes Baden-Württemberg (Landesgraduierten
fellowship for Elisabeth Kapatsina), the Bundesministerium für
Bildung und Forschung and the Fonds der Chemischen Indus-
trie is gratefully acknowledged.
References
1. Goodby, J. W. In Handbook of Liquid Crystals; Demus, D.;
Goodby, J. W.; Gray, G. W.; Spiess, H.-W.; Vill, V., Eds.; Wiley-VCH:
Weinheim, Germany, 1998; Vol. 2A, pp 411–440.
2. Adamo, C.; Barone, V. J. Chem. Phys. 1998, 108, 664–675.
doi:10.1063/1.475428
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