Counterion effects on the mesomorphic properties of chiral imidazolium and pyridinium ionic liquids

Article abstract of DOI:10.1002/ejoc.200900730

Novel calamitic N-methylimidazolium and pyridinium salts with modified citronellyl side-chains and various counterions 3-14 have been synthesised by utilising the commercially available (R)-citronellol (15) as the starting material. Differential scanning

Full text of DOI:10.1002/ejoc.200900730

FULL PAPER
DOI: 10.1002/ejoc.200900730
Counterion Effects on the Mesomorphic Properties of Chiral Imidazolium and
Pyridinium Ionic Liquids
Gilles Kohnen,[a] Martin Tosoni,[a] Stefan Tussetschläger,[a] Angelika Baro,[a] and
Sabine Laschat*[a]
Keywords: Anions / Counterion effects / Ionic liquids / Mesophases / Ion exchange
Novel calamitic N-methylimidazolium and pyridinium salts
with modified citronellyl side-chains and various counterions
3–14 have been synthesised by utilising the commercially
available (R)-citronellol (15) as the starting material.
Differential scanning calorimetry (DSC), polarising optical
microscopy (POM) and temperature-dependent X-ray dif-
fraction studies revealed smectic A (SmA) mesophases for all
the series. 1H NMR studies of the N-methylimidazolium salts
have shown that there is a correlation between the meso-
phase dependence on the counterion and the counterion-
dependent chemical shifts of the acidic 2-H proton.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
length R and the counterion X. Of particular interest are
the effects of the counterion on the mesomorphic properties
because from a limited literature precedence a significant
influence regarding mesophase type and stability was antici-
pated.[5] The results are reported below.
Introduction
Ionic liquids have received increasing interest over the
last decade due to their promising applications, which range
from green designer solvents to electrolytes for solar cells
and electrodeposition.[1] Of particular interest are chiral
ionic liquids, which can be used as solvents, ligands or or-
ganocatalysts in asymmetric synthesis.[2] Another useful
feature of many ionic liquids is their ability to form me-
sophases, that is, liquid crystalline phases, a phenomenon
that was first described by Seddon and Bruce and their co-
workers[3] and later explored by many other groups.[4,5] In
contrast, chiral ionic liquid crystals have rarely been investi-
gated,[2a,4a,6–8] which is somewhat surprising because these
systems should be highly valuable as chiral ordered reaction
media for stoichiometric and catalytic processes.[9] We have
recently shown that citronellyl-derived imidazolium and Scheme 1.
pyridinium ionic liquids 1 and 2, respectively, display smec-
tic phases (Scheme 1).[7] However, the mesophases were
monotropic and covered only a small temperature range. In
addition, variation of the citronellyl side-chain, and thus
systematic analysis of the structure/property relationships,
was not easy. Therefore we decided to study two series of
chiral imidazolium and pyridinium salts 3–8 and 9–14,
respectively (Scheme 2), which can be synthesised from a
common precursor derived from the commercially available
(R)-citronellol (15) with easy modification of both the chain
[a] Institut für Organische Chemie, Universität Stuttgart,
Pfaffenwaldring 55, 70569 Stuttgart, Germany
Fax: +49-711-68564285
E-mail: sabine.laschat@oc.uni-stuttgart.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900730.
Scheme 2.
Eur. J. Org. Chem. 2009, 5601–5609
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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G. Kohnen, M. Tosoni, S. Tussetschläger, A. Baro, S. Laschat
FULL PAPER
Results and Discussion
Following the procedure of Mori and co-workers,[10] (R)-
citronellol (15) was converted into the corresponding tosyl-
ate 16, which was treated with various alkylmagnesium bro-
mides in the presence of 2 mol-% of LiCl and 1 mol-% of
CuCl[11] in THF at –78 °C for 12 h to give after hydrolytic
work-up the heterocoupling products 17 in 70–77% yields
(Scheme 3 and Tables S1 and S2 of the Supporting Infor-
mation). Compounds 17 were submitted to ozonolysis in
CH2Cl2/MeOH at –78 °C followed by reductive work-up
[12]
with NaBH4
to give the alcohols 18 in 68–80% yields.
Subsequent treatment with PBr3 yielded the bromides 19 in
71–93% yields, which were converted into the N-methylimi-
dazolium bromides 4d–8d and pyridinium bromides 10d–
14d by heating 19 with N-methylimidazole or pyridine in
hexane at 60 °C for 2–3 d. Whereas the N-methylimid-
azolium bromides 3a–f were formed within 2 d and were
isolated in good yields (77–93%), the corresponding pyrid-
inium bromides 9a–d required 3 d for complete conversion Scheme 3. Synthesis of N-methylimidazolium (3–8) and pyridinium
derivatives 9–14 starting from (R)-citronellol (15).
and only moderate yields (36–56%) were obtained. It was
also found that the pyridinium bromides 9a–d showed
poorer thermal stability upon prolonged storage or repeti-
tive DSC heating/cooling cycles. Presumably compounds
9a–d are prone to N-dealkylation, a phenomenon that has
recently been described for other pyridinium ionic liquid 9 were investigated by differential scanning calorimetry and
crystals (Figure 1).[5c]
polarising optical microscopy. First, the effect of chain
The mesomorphic properties of compounds 3, 4, 8 and
To obtain the ionic liquids 4d–8d and 10d–14d with dif- length was studied. As shown in Table 1, N-methylimid-
ferent counterions, compounds 3d and 9d were treated with azolium bromides 3a–f displayed enantiotropic mesophases
potassium salts in acetone at room temperature to give the irrespective of the chain length. For example, upon a second
corresponding ionic liquids 4d–8d and 10d–14d in almost heating, compound 3d with a nonyl chain showed a melting
quantitative yields.
transition at 9 °C and a clearing transition at 167 °C.
Figure 1. DSC of compound 9d (after storage for 1 year); heating/cooling rate: 5 Kmin–1. In the first heating cycle the broad peak after
the clearing point was presumably caused by partial decomposition.
Table 1. Phase transition temperatures and enthalpies (∆H) of N-methylimidazolium bromides 3a–f.[a]
3
R
Cr
T [°C]
∆H [kJmol–1]
SmA
T [°C]
∆H [kJmol–1]
I
a
b
c
d
e
f
C6H13
C7H15
C8H17
C9H19
C10H21
C12H25
7
17
1
9
20
30
6.40
18.3
10.5
12.0
13.7
17.5
+
+
+
+
+
+
102
153
144
167
159
177
0.63
1.21
1.23
0.92
0.52
0.92
+
+
+
+
+
+
+
+
+
+
+
[a] The following phases were observed during the second heating: crystalline, smectic A, isotropic; heating rate: 10 Kmin–1.
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Mesomorphic Properties of Chiral Ionic Liquids
An odd/even effect was observed for the clearing points
Similar trends were found for the corresponding pyrid-
of the series 3a–e. POM revealed textures that are not char- inium bromides 9a–d (Table 2). Enantiotropic mesomor-
acteristic of the expected smectic phase[13] (see Figure S1 phism was found for all the derivatives 9a–d with melting
of the Supporting Information) and thus X-ray diffraction points between –27 (for 9a with a C6 chain) and –1 °C (for
(XRD) experiments were undertaken.
9d with a C9 chain) and clearing points between 127 and
X-ray diffraction (XRD) studies of an aligned sample of 184 °C for 9a and 9d, respectively. Thus, the mesophase
compound 3d revealed a diffraction pattern (Figure 2) typi- widths increased significantly for a certain chain length
cal of smectic mesophases with a strong fundamental dif- whenS and SAXS data for 9d (Figure 4) confirmed a SmA
fraction peak (001), a small second-order peak (002) and phase with a layer spacing of 32.7 Å at 55 °C, whereas the
diffuse scattering from the alkyl chains. On the basis of the molecular length of 9d is about 22.8 Å, as calculated for
diffraction patterns of 3d, a SmA mesophase was proposed the stretched molecule by molecular modelling (Chem3D
because the first-order peak is parallel to the magnetic field Ultra®). This means that the layer dimensions are only
and the wide-angle scattering is perpendicular to the (001) slightly influenced by the different head groups. The two-
reflection.
dimensional diffraction pattern of the WAXS section of
compound 9d is shown in Figure 5.
Figure 2. X-ray diffraction pattern of 3d at 80 °C in the SmA phase;
left side: SAXS; right side: WAXS section.
Figure 4. X-ray diffraction pattern of 9d at 70 °C in the SmA phase;
left side: SAXS; right side: WAXS section.
The two-dimensional diffraction pattern of the WAXS
section of compound 3d is shown in Figure 3. The (001)
peak was fitted with a Gaussian distribution to obtain the
exact layer spacing (d001) of the SmA phase of 3d, which is
32.5 Å at 80 °C, whereas the calculated molecular length of
3d is about 23.6 Å, determined for the stretched molecule
by molecular modelling using Chem3D Ultra®.
Figure 5. 2D diffraction pattern (WAXS) of compound 9d at 70 °C.
Next, the counterion effects were studied. For easier
comparison, N-methylimidazolium salts 3d–8d and pyrid-
inium salts 9d–14d with a C9 chain were submitted to DSC
Figure 3. 2D diffraction pattern (WAXS) of compound 3d at 80 °C. and POM. With the exception of the crystalline derivative
Table 2. Phase transition temperatures and enthalpies (∆H) for pyridinium bromides 9a–d.[a,b]
9
R
Cr
T [°C]
∆H [kJmol–1]
SmA
T [°C]
∆H [kJmol–1]
I
a
b
c
C6H13
C7H15
C8H17
C9H19
+
+
+
+
–27
–8
–1
1.36
6.06
7.43
9.00
+
+
+
+
127
184
184
173
0.66
0.84
0.88
0.68
+
+
+
+
d
–1
[a] The following phases were observed during the second heating: crystalline, smectic A, isotropic; heating rate: 10 Kmin–1. [b] Phase
sequence for 9d: Cr1 –18 (3.21) Cr2 –1 (9.00) SmA 173 (0.68) I; heating rate: 5 Kmin–1.
Eur. J. Org. Chem. 2009, 5601–5609
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G. Kohnen, M. Tosoni, S. Tussetschläger, A. Baro, S. Laschat
FULL PAPER
13d, all the examined compounds showed mesomorphic be-
As shown in Table 3, mesophase stability was observed
haviour. As a typical example the enantiotropic DSC traces to decrease in the order Br– Ͼ OAc– Ͼ I– Ͼ BF4– Ͼ
SCN– Ͼ PF6 for the N-methylimidazolium salts 3d–8d. A
similar trend was observed for the pyridinium salts 9d–12d
and 14d except for the iodide and tetrafluoroborate salts
10d and 12d, respectively, which are in reverse order com-
pared with the N-methylimidazolium salts 4d and 6d:
Br– Ͼ OAc– Ͼ BF4– Ͼ I– Ͼ SCN–.
–
of derivative 7d are shown in Figure 6.
Again the clearing temperatures for the pyridinium salts
were higher than those of the N-methylimidazolium salts,
but also the melting points were higher. For N-methylimid-
azolium iodide 4d WAXS and SAXS measurements re-
vealed a layer distance of 33.1 Å at 20 °C (the calculated
molecular length of 23.6 Å for 4d is of course similar to that
for 3d). Thus, the exchange of bromide by iodide resulted in
only a small increase in the layer distance, which indicates
that the anions are well buried among the cationic head
groups that form the double sheet.
Figure 6. DSC investigation of 7d; heating/cooling rate: 5 Kmin–1.
Upon cooling from the isotropic melts to the smectic me-
sophases, focal conical textures, which are typical of SmA
phases,[13] were observed for the derivatives 7d and 11d
(Figure 7). The other derivatives, for which no focal conical
textures could be observed, presumably display spontane-
ous homeotropic alignment during cooling from the iso-
tropic melts to the smectic mesophases, resulting in homeo-
tropic textures. This is also a characteristic of SmA meso-
phases.
From the X-ray diffraction data a packing model can be
proposed (Figure 8) with interdigitating double layers. For
compounds 3d, 4d and 9d the ratio of the smectic layer dis-
tance obtained from the X-ray diffraction study and the
calculated molecular length (LXRD/Lcalc) is 1.4 irrespective
of the counterion or head group. This result is in good
agreement with previous work on ionic liquid crystals.[14]
Note also that no experimental evidence for chiral nematic
(N*) or chiral smectic C (SmC*) phases were found for
compounds 3–14. Thus, the stereogenic centre seems to
have no influence on the phase behaviour, except for op-
erating as a “stopper” for layer interdigitation.
1
With regard to the H NMR spectra of the N-methyl-
imidazolium salts 3d–8d it was found that the anion has a
remarkable influence on the chemical shift of the most
acidic proton 2-H (Figure 9). In comparison with the bro-
mide 3d (δ = 10.49 ppm), upfield shifts were observed for
all the other counterions (up to δ = 8.52 ppm for 7d). Thus,
the chemical shifts of the nonyl-substituted derivatives 3d–
8d were observed to decrease in the following order:
Figure 7. Focal conical textures of the imidazole derivative 7d (left)
and the pyridinium derivative 11d (right) under crossed polarisers
at 60 and 80 °C, respectively, upon cooling from the isotropic phase
(cooling rate: 1 Kmin–1, magnification 200ϫ).
–
Br– Ͼ OAc– Ͼ I– Ͼ BF4– Ͼ SCN– Ͼ PF6
Table 3. Phase transition temperatures and enthalpies (∆H) of the N-methylimidazolium (3d–8d) and pyridinium salts 9d–14d.[a]
Salt
Anion
Cr1
T [°C]
∆H
Cr2
T [°C]
∆H
SmA
T [°C]
∆H
I
[kJmol–1]
[kJmol–1]
[kJmol–1]
3d
Br
I
SCN
BF4
PF6
OAc
Br[b]
I
SCN
BF4
PF6
OAc
–
–
–
–
–
–
–
+
+
+
+
–
–
–
–
–
–
–
–
–
–
–
+
+
+
+
+
+
+
+
+
+
+
+
9
6
8
5
53
4
–1
41
21
1
80
0
12.0
12.9
13.0
11.8
30.6
14.4
9.0
22.8
15.3
11.3
16.1
16.2
+
+
+
+
+
+
+
+
+
+
–
167
147
116
127
93
153
173
171
135
140
126
162
0.92
0.97
0.83
0.75
0.72
1.12
0.68
1.46
0.82
0.88
9.76
2.97
+
+
+
+
+
+
+
+
+
+
+
+
4d
5d
6d
[b]
7d
8d
–
–
9d
–18
–6
2
–19
63
–
3.21
3.28
1.81
1.18
3.67
–
10d
11d
12d
13d
14d
[c]
+
[a] +: the corresponding phase was observed; –: the corresponding phase was not observed during the second heating: Cr1: crystalline 1,
Cr2: crystalline 2, SmA: smectic A, I: isotropic; heating rate: 10 Kmin–1. [b] Heating rate: 5 Kmin–1. [c] Compound 13d displayed no
mesomorphic properties; Cr1 63 Cr2 80 Cr3 126 I.
5604
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Eur. J. Org. Chem. 2009, 5601–5609

Mesomorphic Properties of Chiral Ionic Liquids
In addition, when mixtures of the bromide salt 3d with
increasing ratios of the hexafluorophosphate 8d were inves-
1
tigated by H NMR spectroscopy, the chemical shift of 2-
H showed a linear dependence on the hexafluorophosphate
concentration (Figure 10). Thus, the chemical shift of 2-H
in the N-methylimidazolium salts serves as a sensitive probe
for the anions and mixtures thereof.
Figure 10. 1H NMR chemical shifts of 2-H of mixtures of N-meth-
ylimidazolium salts 3d and 8d as a function of molar fraction.
Figure 8. Proposed model of the SmA phase of compounds 3d and
9d with a partially interdigitated double layer. LXRD is the smectic
layer distance obtained from X-ray diffraction experiments and
Lcalc is the molecular length calculated from molecular modelling
using Chem3D Ultra®.
Conclusions
Two series of chiral N-methylimidazolium and pyrid-
inium salts have been prepared that display smectic A me-
sophases, the phase stabilities of which are strongly influ-
enced by the counterion rather than the chain lengths of
the salts. The mesophase dependence on the counterion
correlates well with the counterion-dependent chemical
shifts of the acidic proton 2-H of the N-methylimidazolium
salts. These experimental results may be regarded as a hint
of the importance of contact ion-pairs on the self-assembly
and physical properties of ionic liquid crystals. Note that
chiral N-methylimidazolium salt 3d can be used as a dopant
to induce chiral nematic phases in a nematic host phase of
4Ј-pentyl-4-cyanobiphenyl, however, a more detailed inves-
tigation is required, which is currently in progress in our
laboratory.
Figure 9. 1H NMR chemical shifts of 2-H of various N-methyl-
imidazolium salts 3d–8d.
Owing to the delocalised positive charge the N-methyl-
imidazolium ion can be considered to be a large soft cation.
With increasing transfer of electron density from the anion
to the cation, the bond strengths of the acidic C2–H bond is
weakened to a lesser extent and thus the signals are shifted
Experimental Section
General: Melting points were determined with a Büchi SMP 20
apparatus and are uncorrected. NMR spectra were recorded with
a Bruker Avance 300 or Avance 500 (1H: 300 or 500 MHz; 13C: 75
upfield. Note that Shah and Maginn carried out Monte or 125 MHz) spectrometer with TMS as the internal standard. Sig-
nal assignments are based on DEPT and COSY experiments. IR
spectra were recorded with a Bruker Vector 22 FTIR spectrometer
with a MKII Golden Gate Single Reflection Diamant ATR system.
Mass spectra were obtained with a Varian MAT 711 spectrometer
using EI at 70 eV and with a Bruker Daltonics micrOTOF-Q spec-
trometer using ESI. Chromatography was performed on silica gel
60 (230–400 mesh, Macherey–Nagel). Differential scanning calo-
rimetry was performed with a Mettler-Toledo DSC822e instrument
(heating rates were 2, 5 or 10 Kmin–1). Polarising optical micro-
scopy was carried out with an Olympus BX50 polarising micro-
scope combined with a Linkam TP93 central processor. X-ray ex-
Carlo simulations on N-butyl-N-methylimidazolium hexa-
fluorophosphate, which clearly revealed a preferred inter-
action of the anion with 2-H.[15]
When mixtures of N-methylimidazolium salts 3d–8d with
the same cation, that is, the same alkyl chain length but
1
different anions, were studied by H NMR spectroscopy,
only a single set of signals was observed particularly with
respect to 2-H. Presumably on the NMR timescale rapid
anion exchange results in an average value for the chemical
shift of 2-H.
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G. Kohnen, M. Tosoni, S. Tussetschläger, A. Baro, S. Laschat
FULL PAPER
periments were performed with a Bruker AXS Nanostar C dif-
fractometer employing Ni-filtered Cu-Kα radiation (λ = 1.5418 Å).
Commercial reagents were used without further purification. All
reactions were carried out using standard Schlenk techniques un-
less otherwise noted.
CH3), 22.7 (C-14), 27.0–33.0 (C-2, C-3, C-4, C-6, C-7, C-8, C-9,
C-10, C-11, C-12, C-13), 37.0 (C-5), 63.4 (C-1) ppm. FTIR (ATR):
ν = 3326 (br), 2954 (s), 2921 (s), 2852 (s), 1464 (m), 1377 (m), 1057
˜
(br), 898 (w), 721 (m) cm–1. MS (EI, 70 eV): m/z (%) = 242.1 (2)
[M]+, 224.2 (46), 196.2 (100), 181.2 (18), 126.1 (20), 111.1 (22), 97.1
(42), 84.1 (42), 69.1 (96). HMRS (EI): calcd. for C16H34O 242.2610;
found 242.2574 [M]+.
(R)-3Ј,7Ј-Dimethyloct-6Ј-enyl p-toluenesulfonate (16) was prepared
according to a literature procedure.[10b] The following derivatives
are known: 17a–19a,[12] 17c,[16] 17e,[17] 17f,[18] 18c,e[19] and 18f.[20]
General Procedure for the Bromination of Alcohols 18: PBr3 (90 µL,
0.96 mmol) was added dropwise to a solution of alcohol 18
(1.75 mmol) in Et2O (15 mL) at room temp. After stirring for 12 h
the mixture was hydrolysed with ice-cooled H2O (15 mL), the layers
were separated and the organic layer was washed with satd.
NaHCO3 (50 mL), brine (50 mL) and H2O (2ϫ50 mL), dried with
MgSO4 and the solvents evaporated. The crude product was puri-
fied by column chromatography on SiO2 (hexanes/EtOAc = 20:1).
General Procedure for the Reaction of Tosylate 16 with Cuprates: 1-
Bromoalkene (47.0 mmol) in THF (80 mL) was added dropwise to
a suspension of Mg turnings (1.42 g, 58.3 mmol) in THF (10 mL)
so that a steady reflux of the mixture was maintained. Then the
mixture was heated at reflux for a further 30 min, cooled to room
temp. and then added dropwise to a cooled solution of tosylate 16
(4.10 g, 13.2 mmol) in THF (30 mL) at –78 °C. Then a solution of
LiCl (33.4 g, 0.79 mmol) and CuCl2 (56.6 g, 0.42 mmol) in THF
(10 mL) was added dropwise and the resulting mixture was stirred
for 5 h at –78 °C, warmed to room temp. overnight and hydrolysed
with satd. NH4Cl (100 mL). The layers were separated, the aqueous
layer was extracted with hexanes (2ϫ200 mL) and the combined
organic layers were washed with H2O (2ϫ100 mL) and brine
(100 mL) and concentrated. The crude products were purified by
distillation under reduced pressure (for 17a–c) or by column
chromatography on SiO2 (hexanes) (for 17d–f).
(4S)-4-Methyl-1-pentadecyl Bromide (19d): From 18d (3.00 g,
13.1 mmol) a colourless oil (3.26 g, 13.4 mmol, 88%) was obtained.
1
[α]2D2 = –4.4 (c = 1.00, CHCl3). H NMR (300 MHz, CDCl3): δ =
0.87 (d, J = 6.5 Hz, 3 H, 4-CH3), 0.88 (t, J = 6.8 Hz, 3 H, 15-H)
1.05–1.50 (m, 23 H, 3-H, 4-H, 5-H, 6-H, 7-H, 8-H, 9-H, 10-H, 11-
H, 12-H, 13-H, 14-H), 1.72–1.95 (m, 2 H, 2-H), 3.39 (t, J = 6.9 Hz,
2 H, 1-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (C-15), 19.6
(4-CH3), 22.7 (C-14), 26.9–34.3 (C-1, C-2, C-3, C-4, C-6, C-7, C-
8, C-9, C-10, C-11, C-12, C-13), 35.5 (C-3), 36.9 (C-5) ppm. FTIR
(ATR): ν = 2956 (s), 2921 (s), 2852 (s), 1462 (m), 1377 (m), 1256
˜
(6S)-2,6-Dimethyl-2-heptadecene (17d): From 16 (35.0 g, 113 mmol)
a colourless oil (21.0 g, 78.9 mmol, 70%) was obtained. [α]2D2 = –4.1
(c = 1.00, CHCl3). H NMR (300 MHz, CDCl3): δ = 0.85 (d, J =
6.5 Hz, 3 H, 6-CH3), 0.88 (t, J = 6.7 Hz, 3 H, 17-H) 1.02–1.46 (m,
23 H, 5-H, 6-H, 7-H, 8-H, 9-H, 10-H, 11-H, 12-H, 13-H, 14-H, 15-
H, 16-H), 1.59–1.61 (m, 3 H, 1-H), 1.67–1.69 (m, 3 H, 2-CH3),
(w), 1206 (w), 721 (m), 644 (w) cm–1. MS (EI): m/z (%) = 306.2 (4),
304.2 (5) [M]+, 151.0 (98), 149.0 (100) [C5H10Br]+, 113.1 (5), 99.1
(10), 85.1 (28), 71.1 (50.0), 69.1 (76). HMRS (EI): calcd. for
C16H33Br 304.1766, 306.1745; found 304.1763, 306.1760 [M]+.
1
General Procedure for the Preparation of N-Methylimidazolium Bro-
1.88–2.05 (m, 2 H, 4-H), 5.06–5.13 (m, 1 H, 3-H) ppm. 13C NMR mides 3: A solution of bromide 19 (0.71 mmol) and 1-methylimid-
(75 MHz, CDCl3): δ = 14.1 (C-17), 17.6 (2-CH3), 19.6 (6-CH3), azole (58.0 mg, 0.71 mmol) in hexanes (2 mL) was heated at reflux
22.7 (C-16), 25.6–32.5 (C-1, C-4, C-6, C-8, C-9, C-10, C-11, C-
for 48 h. After cooling to room temp., the solvent was removed in
12, C-13, C-14, C-15), 37.0–37.2 (C-5, C-7), 125.1 (C-3), 130.9 (C- vacuo and the crude product was washed with Et2O (2ϫ1 mL)
2) ppm. FTIR (ATR): ν = 2957 (s), 2921 (s), 2853 (s), 1459 (m),
under sonification, diluted in MeCN (2 mL), washed with n-hexane
˜
1377 (m), 984 (w), 828 (w), 721 (m) cm–1. MS (EI, 70 eV): m/z (%) (2ϫ2 mL) and dried in vacuo for 2 d at 90 °C.
= 266.3 (29) [M]+, 126.1 (40), 111.2 (56), 97.1 (40), 83.1 (32), 69.1
(4ЈS)-1Ј-Methyl-3Ј-(4Ј-methylpentadecyl)imidazolium Bromide (3d):
(100). HMRS (EI): calcd. for C19H38 266.2974; found 266.2969
From 19d (2.97 g, 9.73 mmol) a colourless waxy solid (3.47 g,
[M]+.
8.94 mmol, 92%) was obtained. [α]2D2 = –1.3 (c = 1.00, CHCl3). H
1
General Procedure for the Ozonolysis of Alkenes 17: Ozone was
bubbled through a cooled solution of alkene 17 (4.46 mmol) in
CH2Cl2 (10 mL) and MeOH (10 mL) at –42 °C until the blue col-
our remained. Excess of ozone was removed by bubbling N2
through the solution. Then NaBH4 (228 mg, 6.03 mmol) was added
in small portions, the mixture was warmed to 0 °C and stirring was
continued for 5 h. After hydrolysis with satd. NH4Cl (25 mL), the
solvent was evaporated and the colourless precipitate was removed
by filtration. The aqueous layer was extracted with Et2O
NMR (300 MHz, CDCl3): δ = 0.86 (d, J = 6.7 Hz, 3 H, 4Ј-CH3),
0.88 (t, J = 6.9 Hz, 3 H, 15Ј-H), 1.01–1.50 (m, 23 H, 3Ј-H, 4Ј-H,
5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H, 14Ј-H),
1.79–2.04 (m, 2 H, 2Ј-H), 4.15 (s, 3 H, N-CH3), 4.31 (t, J = 7.4 Hz,
2 H, 1Ј-H), 7.35 (t, J = 1.7 Hz, 1 H, 4-H), 7.53 (t, J = 1.7 Hz, 1 H,
5-H), 10.49 (br. s, 2-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1
(C-15Ј), 19.3 (4Ј-CH3), 22.6 (C-14Ј), 27.0–33.4 (C-3Ј, C-4Ј, C-6Ј, C-
7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8–37.1 (C-5Ј, N-
CH3), 50.4 (C-1Ј), 121.8 (C-4), 123.8 (C-5), 137.2 (C-2) ppm. FTIR
(2ϫ25 mL) and the combined organic layers were washed with (ATR): ν = 3139 (w), 3069 (w), 2955 (s), 2921 (s), 2852 (s), 1630
˜
H2O (50 mL) and brine (50 mL) and dried with MgSO4 and con- (w), 1572 (s), 1464 (s), 1378 (m), 1168 (vs), 842 (w), 751 (m), 648
centrated. The crude product was purified by column chromatog-
raphy on SiO2 (hexanes/EtOAc = 10:1) to yield the product 18 and
the starting material 17, which was resubmitted to ozonolysis. For
each compound 18 three subsequent ozonolysis cycles were carried
out.
(w), 620 (s) cm–1. C20H39BrN2 (387.44): calcd. C 62.00, H 10.15, N
7.23, Br 20.62; found C 61.97, H 10.16, N 7.23, Br 20.67. MS (ESI,
+ve): m/z = 307.3 [M]+, 151.0, 123.1, 109.1, 95.1, 83.1. MS (ESI, –
ve): m/z = 467.1 [MBr2]–. HRMS (ESI): calcd. for [C20H39N2]+
307.3108; found 307.3110 [M]+.
(4S)-4-Methyl-1-pentadecanol (18d): From 17d (7.50 g, 28.1 mmol) General Procedure for the Preparation of Pyridinium Bromides 9: A
a colourless oil (5.11 g, 21.1 mmol, 75%) was obtained. [α]2D2 = –1.8
(c = 1.00, CHCl3). H NMR (300 MHz, CDCl3): δ = 0.87 (d, J = 0.71 mmol) in hexanes (2 mL) was heated at reflux for 3 d. After
solution of bromide 19 (0.65 mmol) and pyridine (56.6 mg,
1
6.5 Hz, 3 H, 4-CH3), 0.88 (t, J = 6.8 Hz, 3 H, 15-H) 1.06–1.48 (m,
cooling to room temp. the solvent was removed in vacuo and the
23 H, 3-H, 4-H, 5-H, 6-H, 7-H, 8-H, 9-H, 10-H, 11-H, 12-H, 13- crude product was washed with Et2O (2ϫ2 mL) under son-
H, 14-H), 1.54–1.69 (m, 2 H, 2-H), 3.62 (t, J = 6.7 Hz, 2 H, 1-
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (C-15), 19.7 (4-
ification, diluted in MeCN (2 mL), washed with n-hexane
(2ϫ2 mL) and dried in vacuo for 3 d at 120 °C.
5606
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5601–5609

Mesomorphic Properties of Chiral Ionic Liquids
(4ЈS)-(4Ј-Methylpentadecyl)pyridinium Bromide (9d): From 19d
(3.00 g, 9.82 mmol) a colourless waxy solid (2.10 g, 5.47 mmol,
56%) was obtained. [α]2D2 = +18.8 (c = 1.00, CHCl3). 1H NMR
calcd. C 51.21, H 7.98, N 8.53, S 6.51; found C 51.28, H 8.00, N
8.49, S 6.50. MS (ESI, +ve): m/z = 307.3 [M]+, 151.1, 123.1, 109.1,
95.1, 83.1 83.1. MS (ESI, –ve): m/z = 423.2 [M(SCN)2]–. HMRS
(300 MHz, CDCl3): δ = 0.85 (d, J = 6.6 Hz, 3 H, 4Ј-CH3), 0.88 (t, (ESI): calcd. for [C20H39N2]+ 307.3108; found 307.3111 [M]+.
J = 6.8 Hz, 3 H, 15Ј-H), 1.05–1.49 (m, 23 H, 3Ј-H, 4Ј-H, 5Ј-H, 6Ј-
(4ЈS)-1Ј-Methyl-3Ј-(4Ј-methylpentadecyl)imidazolium
Tetrafluo-
H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H, 14Ј-H), 1.99–2.27
(m, 2 H, 2Ј-H), 5.07 (t, J = 7.3 Hz, 2 H, 1Ј-H), 8.11–8.15 (m, 2 H,
3-H, 5-H), 8.49–8.51 (m, 1 H, 4-H), 9.44–9.46 (m, 2 H, 2-H, 6-
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (C-15’), 19.3 (4Ј-
CH3), 22.7 (C-14Ј), 27.0–33.2 (C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј,
C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8 (C-5Ј), 62.5 (C-1Ј), 128.4 (C-3, C-
roborate (6d): From 3d (130 mg, 0.34 mmol) a red waxy solid
(131 mg, 0.33 mmol, 98%) was obtained. [α]2D2 = +12.9 (c = 1.00,
1
CHCl3). H NMR (500 MHz, CDCl3): δ = 0.86 (d, J = 6.6 Hz, 3
H, 4Ј-CH3), 0.88 (t, J = 7.1 Hz, 3 H, 15Ј-H) 1.02–1.46 (m, 23 H,
3Ј-H, 4Ј-H, 5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-
H, 14Ј-H), 1.78–1.96 (m, 2 H, 2Ј-H), 4.01 (s, 3 H, N-CH3), 4.23 (t,
J = 7.1 Hz, 2 H, 1Ј-H), 7.39 (t, J = 1.7 Hz, 1 H, 4-H), 7.52 (t, J =
1.7 Hz, 1 H, 5-H), 9.49 (br. s, 1 H, 2-H) ppm. 13C NMR (125 MHz,
CDCl3): δ = 14.1 (C-15Ј), 19.3 (4Ј-CH3), 22.7 (C-14Ј), 27.0–33.4
(C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј),
36.5–36.8 (C-5Ј, N-CH3), 50.4 (C-1Ј), 122.0 (C-4), 123.8 (C-5),
5), 144.9 (C-4), 145.2 (C-2, C-6) ppm. FTIR (ATR): ν = 3081 (w),
˜
2956 (s), 2922 (s), 2853 (s), 2361 (w), 1572 (s), 1465 (s), 1378 (m),
1170 (vs), 847 (w), 747 (m), 624 (s) cm–1. C21H38BrN (384.44):
calcd. C 65.61, H 9.96, N 3.64, Br 20.78; found C 65.64, H 9.93,
N 3.64, Br 20.77. MS (ESI, +): m/z = 304.3 [M]+, 148.1, 132.1,
120.1, 106.1, 80.0. HMRS (ESI, +ve): calcd. for C21H38N+
304.2999; found 304.2999 [M]+. HRMS (ESI, –ve): calcd. for Br–
78.9183, 80.9163; found 78.9178, 80.9155 [Br–].
136.8 (C-2) ppm. FTIR (ATR): ν = 3158 (w), 3117 (w), 2956 (s),
˜
2921 (s), 2852 (s), 1627 (w), 1574 (s), 1465 (s), 1378 (m), 1169 (vs),
1055 (vs), 847 (w), 751 (m), 648 (w), 623 (s) cm–1. C20H39BF4N2
(394.34): calcd. C 60.92, H 9.97, N 7.10; found C 60.95, H 10.03,
N 7.04. MS (ESI, +ve): m/z = 307.3 [M]+, 151.1, 123.1, 109.1, 95.1,
83.1. MS (ESI, –ve): m/z = 481.3 [M(BF4)2]–, 87.0 [BF4]–. HMRS
(ESI): calcd. for [C20H39N2]+ 307.3108; found 307.3114 [M]+.
General Procedure for the Anion Exchange of (4ЈS)-1-Methyl-3-(4Ј-
methylpentadecyl)imidazolium Bromide (3d): KX (0.30 mmol, X =
I, SCN, BF4, PF6, OAc) was added to a solution of (4ЈS)-1-methyl-
3-(4Ј-methylpentadecyl)imidazolium
bromide
(3d;
117 mg,
0.30 mmol) in acetone (2 mL) and the mixture was stirred over-
night at room temp. The colourless precipitate was removed by
filtration and the filtrate was concentrated in vacuo. The solid resi-
due was diluted in CHCl3 (2 mL) and the remaining precipitate was
removed by filtration. After concentration of the filtrate in vacuo,
the resulting solid was dried in vacuo for 2 d at 80 °C.
(4ЈS)-1Ј-Methyl-3Ј-(4Ј-methylpentadecyl)imidazolium Hexafluoro-
phosphate (7d): From 3d (79.6 mg, 0.20 mmol) a grey waxy solid
(91.8 mg, 0.20 mmol, 99%) was obtained. [α]2D2 = –22.1 (c = 1.00,
1
CHCl3). H NMR (500 MHz, CDCl3): δ = 0.86 (d, J = 6.6 Hz, 3
H, 4Ј-CH3), 0.88 (t, J = 6.8 Hz, 3 H, 15’-H) 1.02–1.46 (m, 23 H,
3Ј-H, 4Ј-H, 5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-
H, 14Ј-H), 1.78–1.96 (m, 2 H, 2Ј-H), 3.91 (s, 3 H, N-CH3), 4.12 (t,
J = 7.1 Hz, 2 H, 1Ј-H), 7.25 (br. s, 1 H, 4-H), 7.29 (br. s, 1 H, 5-
H), 8.52 (br. s, 1 H, 2-H) ppm. 13C NMR (125 MHz, CDCl3): δ =
14.1 (C-15Ј), 19.2 (4Ј-CH3), 22.6 (C-14Ј), 27.0–33.4 (C-3Ј, C-4Ј, C-
6Ј, C-7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.2–36.8 (C-5Ј,
N-CH3), 50.5 (C-1Ј), 122.0 (C-4), 123.7 (C-5), 136.0 (C-2) ppm.
(4ЈS)-1Ј-Methyl-3Ј-(4Ј-methylpentadecyl)imidazolium Iodide (4d):
From 3d (117 mg, 0.30 mmol) an orange waxy solid (130 mg,
0.30 mmol, 98%) was obtained. [α]2D2 = +7.1 (c = 1.00, CHCl3). 1H
NMR (500 MHz, CDCl3): δ = 0.87 (d, J = 6.6 Hz, 3 H, 4Ј-CH3),
0.88 (t, J = 6.8 Hz, 3 H, 15Ј-H) 1.02–1.46 (m, 23 H, 3Ј-H, 4Ј-H,
5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H, 14Ј-H),
1.81–1.99 (m, 2 H, 2Ј-H), 4.15 (s, 3 H, N-CH3), 4.31 (t, J = 7.47 Hz,
2 H, 1Ј-H), 7.47 (t, J = 1.7 Hz, 1 H, 4-H), 7.65 (t, J = 1.7 Hz, 1 H,
5-H), 10.04 (br. s, 1 H, 2-H) ppm. 13C NMR (125 MHz, CDCl3):
δ = 14.1 (C-15Ј), 19.4 (4Ј-CH3), 22.6 (C-14Ј), 27.0–33.4 (C-3Ј, C-
4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8–37.1
(C-5Ј, N-CH3), 50.5 (C-1Ј), 122.1 (C-4), 123.9 (C-5), 136.8 (C-
FTIR (ATR): ν = 3180 (w), 3132 (w), 2957, 2916 (s), 2849 (s), 1573
˜
(s), 1468 (m), 1321 (w), 1171 (vs), 817 (vs), 755 (m), 661 (s), 624
(vs), 554 (vs) cm–1. C20H39F6N2P (452.50): calcd. C 53.09, H 8.69,
N 6.19; found C 53.04, H 8.70, N 6.25. MS (ESI, +ve): m/z = 307.3
[M]+, 151.1, 123.1, 109.1, 95.1, 83.1. MS (ESI, –ve): m/z = 597.2
[M(PF6)2]–, 144.9 [PF6]–. HMRS (ESI): calcd. for [C20H39N2]+
307.3108; found 307.3106 [M]+.
2) ppm. FTIR (ATR): ν = 3102 (w) 2955 (s), 2922 (s), 2852 (s), 1464
˜
(m), 1378 (m), 1047 (br), 831 (w), 741 (m), 621 (s) cm–1. C20H39IN2
(434.44): calcd. C 55.29, H 9.05, N 6.45; found C 55.32, H 9.06, N
6.53. MS (ESI, +ve): m/z = 307.3 [M]+, 151.1, 123.1, 109.1, 95.1,
83.1. MS (ESI, –ve): m/z = 561.0 [MI2]–, 126.9 [I]–. HMRS (ESI):
calcd. for [C20H39N2]+ 307.3108; found 307.3115 [M]+.
(4ЈS)-1Ј-Methyl-3Ј-(4Ј-methylpentadecyl)imidazolium Acetate (8d):
From 3d (93.4 mg, 0.24 mmol) a colourless waxy solid (87.5 mg,
0.23 mmol, 97%) was obtained. [α]2D2 = –21.8 (c = 1.00, CHCl3).
1H NMR (500 MHz, CDCl3): δ = 0.86 (d, J = 6.7 Hz, 3 H, 4Ј-
CH3), 0.88 (t, J = 6.9 Hz, 3 H, 15’-H) 1.02–1.46 (m, 23 H, 3Ј-H,
4Ј-H, 5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H,
14Ј-H), 1.78–1.96 (m, 2 H, 2Ј-H), 4.14 (s, 3 H, N-CH3), 4.30 (t, J
= 7.4 Hz, 2 H, 1Ј-H), 7.42 (t, J = 1.65 Hz, 1 H, 4-H), 7.63 (t, J =
1.7 Hz, 1 H, 5-H), 10.44 (br. s, 1 H, 2-H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 14.1 (C-15Ј), 19.4 (4Ј-CH3), 22.7 (C-14Ј),
27.0–33.4 (C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј,
C-13Ј), 36.7–36.8 (C-5Ј, N-CH3), 50.4 (C-1Ј), 121.8 (C-4), 123.7 (C-
(4ЈS)-1Ј-Methyl-3Ј-(4Ј-methylpentadecyl)imidazolium Thiocyanate
(5d): From 3d (114 mg, 0.29 mmol) a yellow waxy solid (106 mg,
0.27 mmol, 97%) was obtained. [α]2D2 = –15.8 (c = 1.00, CHCl3).
1H NMR (500 MHz, CDCl3): δ = 0.86 (d, J = 6.7 Hz, 3 H, 4Ј-
CH3), 0.88 (t, J = 6.9 Hz, 3 H, 15Ј-H) 1.02–1.46 (m, 23 H, 3Ј-H,
4Ј-H, 5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H,
14Ј-H), 1.78–1.96 (m, 2 H, 2Ј-H), 4.12 (s, 3 H, N-CH3), 4.29 (t, J
= 7.4 Hz, 2 H, 1Ј-H), 7.37 (t, J = 1.7 Hz, 1 H, 4-H), 7.63 (t, J =
1.7 Hz, 1 H, 5-H), 9.46 (br. s, 1 H, 2-H) ppm. 13C NMR (125 MHz,
CDCl3): δ = 14.1 (C-15Ј), 19.3 (4Ј-CH3), 22.7 (C-14Ј), 27.0–33.4
(C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј),
36.8–36.9 (C-5Ј, N-CH3), 50.8 (C-1Ј), 122.0 (C-4), 123.7 (C-5),
5), 137.6 (C-2) ppm. FTIR (ATR): ν = 3150 (w), 3090 (w), 2956
˜
(s), 2921 (s), 2852 (s), 1573 (s), 1464 (s), 1377 (m), 1168 (vs), 1046
(br), 849 (w), 746 (m), 621 (s) cm–1. C22H42N2O (350.58): calcd. C
75.37, H 12.08, N 7.99; found C 75.33, H 12.20, N 8.02. MS (ESI,
+ve): m/z = 307.3 [M]+, 151.1, 123.1, 109.1, 95.1, 83.1. HMRS
(ESI): calcd. for [C20H39N2]+ 307.3108; found 307.3119 [M]+.
137.2 (C-2) ppm. FTIR (ATR): ν = 3149 (w), 3102 (w), 2956 (s),
˜
2922 (s), 2852 (s), 2050 (s), 1636 (w), 1573 (m), 1465 (s), 1378 (m),
General Procedure for the Anion Exchange of (4ЈS)-(4Ј-Methylpen-
tadecyl)pyridinium Bromide (9d): KX (0.55 mmol, X = I, SCN, BF4,
1169 (vs), 842 (w), 721 (w), 623 (s) cm–1. C21H39N3S (365.62):
Eur. J. Org. Chem. 2009, 5601–5609
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5607

G. Kohnen, M. Tosoni, S. Tussetschläger, A. Baro, S. Laschat
FULL PAPER
PF6, OAc) was added to a solution of (4ЈS)-(4Ј-methylpentadecyl)- (4ЈS)-(4Ј-Methylpentadecyl)pyridinium Hexafluorophosphate (13d):
pyridinium bromide (9d; 211 mg, 0.55 mmol) in acetone (2 mL) From 9d (209 mg, 0.52 mmol) grey waxy solid (233 mg,
a
and the mixture was stirred overnight at room temp. The colourless
precipitate was removed by filtration and the filtrate was concen-
trated in vacuo. The solid residue was diluted in CHCl3 (2 mL) and
the remaining precipitate was removed by filtration. After concen-
tration of the filtrate in vacuo, the resulting solid was dried in vacuo
for 2 d at 80 °C.
0.52 mmol, 96%) was obtained. [α]2D2 = –56.4 (c = 1.00, CHCl3).
1H NMR (300 MHz, CDCl3): δ = 0.86 (d, J = 6.6 Hz, 3 H, 4Ј-
CH3), 0.88 (t, J = 6.7 Hz, 3 H, 15’-H) 1.05–1.49 (m, 23 H, 3Ј-H,
4Ј-H, 5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H,
14Ј-H), 1.99–2.27 (m, 2 H, 2Ј-H), 4.60 (t, J = 7.6 Hz, 2 H, 1Ј-H),
8.04–8.06 (m, 2 H, 3-H, 5-H), 8.46–8.49 (m, 1 H, 4-H), 8.70–8.73
(m, 2 H, 2-H, 6-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1
(C-15’), 19.2 (4Ј-CH3), 22.7 (C-14Ј), 27.0–33.3 (C-3Ј, C-4Ј, C-6Ј, C-
7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8 (C-5Ј), 62.9 (C-1Ј),
128.6 (C-3, C-5), 144.1 (C-4), 145.5 (C-2, C-6) ppm. FTIR (ATR):
(4ЈS)-(4Ј-Methylpentadecyl)pyridinium Iodide (10d): From 9d
(211 mg, 0.55 mmol) a yellow waxy solid (230 mg, 0.53 mmol,
97%) was obtained. [α]2D2 = +10.9 (c = 1.00, CHCl3). 1H NMR
(300 MHz, CDCl3): δ = 0.86 (d, J = 6.5 Hz, 3 H, 4Ј-CH3), 0.88 (t,
J = 6.8 Hz, 3 H, 15’-H), 1.01–1.50 (m, 23 H, 3Ј-H, 4Ј-H, 5Ј-H, 6Ј-
H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H, 14Ј-H), 1.92–2.24
(m, 2 H, 2Ј-H), 4.95 (t, J = 7.6 Hz, 2 H, 1Ј-H), 8.16–8.21 (m, 2 H,
3-H, 5-H), 8.55–8.61 (m, 1 H, 4-H), 9.39–9.41 (m, 2 H, 2-H, 6-
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (C-15’), 19.4 (4Ј-
CH3), 22.7 (C-14Ј), 27.0–33.1 (C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј,
C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8 (C-5Ј), 62.5 (C-1Ј), 128.6 (C-3, C-
ν = 3179 (w), 2957 (s), 2916 (s), 2849 (s), 2181 (br), 1978 (br), 1573
˜
(s), 1468 (vs), 1381 (w), 1167 (vs), 843 (s), 818 (vs), 755 (s), 661 (s),
624 (s), 555 (vs) cm–1. C21H38F6NP (449.50): calcd. C 56.11, H
8.52, N 3.12; found C 56.24, H 8.52, N 3.07. MS (ESI, +ve): m/z
= 304.3 [M]+, 148.1, 132.1, 120.1, 80.0. MS (ESI, –ve): m/z = 145.9
[PF6]–. HMRS (ESI): calcd. for [C21H38N]+ 304.2999; found
304.3006 [M]+.
5), 144.9 (C-4), 145.4 (C-2, C-6) ppm. FTIR (ATR): ν = 3107 (w),
˜
(4ЈS)-(4Ј-Methylpentadecyl)pyridinium Acetate (14d): From 9d
(151 mg, 0.40 mmol) a pale-yellow waxy solid (138 mg, 0.38 mmol,
95%) was obtained. [α]2D2 = +4.4 (c = 1.00, CHCl3). 1H NMR
(300 MHz, CDCl3): δ = 0.86 (d, J = 6.6 Hz, 3 H, 4Ј-CH3), 0.88 (t,
J = 6.8 Hz, 3 H, 15’-H) 1.05–1.49 (m, 23 H, 3Ј-H, 4Ј-H, 5Ј-H, 6Ј-
H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H, 14Ј-H), 1.99–2.27
(m, 2 H, 2Ј-H), 4.98 (t, J = 7.3 Hz, 2 H, 1Ј-H), 8.12–8.15 (m, 2 H,
3-H, 5-H), 8.49–8.52 (m, 1 H, 4-H), 9.43–9.46 (m, 2 H, 2-H, 6-
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (C-15’), 19.3 (4Ј-
CH3), 22.7 (C-14Ј), 27.0–33.2 (C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј,
C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8 (C-5Ј), 63.0 (C-1Ј), 128.4 (C-3, C-
2955 (s), 2921 (s), 2852 (s), 1570 (s), 1464 (vs), 1378 (m), 1165 (vs),
838 (s), 745 (s), 621 (s) cm–1. MS (ESI, +ve): m/z = 304.3 [M]+,
148.1, 120.1, 106.1, 80.0. C21H38IN (431.44): calcd. C 58.46, H
8.88, N 3.25; found C 58.51, H 8.89, N 3.19. MS (ESI, –ve): m/z
= 126.9 [I]–. HMRS (ESI): calcd. for [C21H38N]+ 304.2999; found
304.3002 [M]+.
(4ЈS)-(4Ј-Methylpentadecyl)pyridinium Thiocyanate (11d): From 9d
(175 mg, 0.45 mmol) a colourless waxy solid (160 mg, 0.44 mmol,
98%) was obtained. [α]2D2 = –5.2 (c = 1.00, CHCl3). 1H NMR
(500 MHz, CDCl3): δ = 0.87 (d, J = 6.6 Hz, 3 H, 4Ј-CH3), 0.88 (t,
J = 6.8 Hz, 3 H, 15’-H) 1.03–1.47 (m, 23 H, 3Ј-H, 4Ј-H, 5Ј-H, 6Ј-
H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H, 14Ј-H), 1.99–2.27
(m, 2 H, 2Ј-H), 4.82 (t, J = 7.6 Hz, 2 H, 1Ј-H), 8.16–8.20 (m, 2 H,
3-H, 5-H), 8.54–8.56 (m, 1 H, 4-H), 9.05–9.08 (m, 2 H, 2-H, 6-
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1 (C-15’), 19.3 (4Ј-
CH3), 22.7 (C-14Ј), 27.0–33.3 (C-3Ј, C-4Ј, C-6Ј, C-7Ј, C-8Ј, C-9Ј,
C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.8 (C-5Ј), 63.0 (C-1Ј), 128.7 (C-3, C-
5), 145.0 (C-4), 145.1 (C-2, C-6) ppm. FTIR (ATR): ν = 3080 (w),
˜
2956 (s), 2922 (s), 2852 (s), 1572 (s), 1463 (s), 1377 (m), 1167 (vs),
930 (w), 833 (br), 746 (br), 648 (s), 620 (vs), 555 (s) cm–1.
C23H41NO (347.58): calcd. C 79.48, H 11.89, N 4.03; found C
79.47, H 11.94, N 4.06. MS (ESI, +ve): m/z = 304.3 [M]+, 148.1,
132.1, 120.1, 106.1, 80.0. HMRS (ESI): calcd. for [C21H38N]+
304.2999; found 304.3008 [M]+.
5), 144.7 (C-4), 145.4 (C-2, C-6) ppm. FTIR (ATR): ν = 3384 (w),
˜
Supporting Information (see also the footnote on the first page of
this article): Yields of compounds 3, 4–14 and 17–19, POM texture
of 3d, spectroscopic and analytical data for compounds 17a–c,e,f,
18a–c,e,f, 19a–c,e,f, 3a–c,e,f and 9a–c and X-ray diffraction pat-
terns of compounds 3d, 4d, 7d, 9d and 10d.
3093 (w), 2956 (s), 2922 (s), 2852 (s), 2190 (br), 2048 (s), 1573 (s),
1465 (s), 1378 (w), 1168 (vs), 844 (w), 621 (s) cm–1. C22H38N2S
(362.62): calcd. C 72.87, H 10.56, N 7.73, S 8.84; found C 72.90,
H 10.57, N 7.68, S 8.83. MS (ESI, +ve): m/z = 304.3 [M]+,
148.1, 132.1, 120.2, 106.1, 93.1, 80.1. HMRS (ESI): calcd. for
[C21H38N]+ 304.2999; found 304.3002 [M]+.
Acknowledgments
(4ЈS)-(4Ј-Methylpentadecyl)pyridinium Tetrafluoroborate (12d):
From 9d (157 mg, 0.41 mmol) a pale-brown waxy solid (159 mg,
0.40 mmol, 99%) was obtained. [α]2D2 = –12.0 (c = 1.00, CHCl3).
1H NMR (300 MHz, CDCl3): δ = 0.85 (d, J = 6.5 Hz, 3 H, 4Ј-
CH3), 0.88 (t, J = 6.8 Hz, 3 H, 15’-H) 1.00–1.48 (m, 23 H, 3Ј-H,
4Ј-H, 5Ј-H, 6Ј-H, 7Ј-H, 8Ј-H, 9Ј-H, 10Ј-H, 11Ј-H, 12Ј-H, 13Ј-H,
14Ј-H), 1.92–2.19 (m, 2 H, 2Ј-H), 4.75 (t, J = 7.5 Hz, 2 H, 1Ј-H),
8.01–8.11 (m, 2 H, 3-H, 5-H), 8.47–8.52 (m, 1 H, 4-H), 9.02–9.04
(m, 2 H, 2-H, 6-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.1
Generous financial support from the Deutsche Forschungsgemein-
schaft (DFG), the Fonds der Chemischen Industrie, the Bundesmi-
nisterium für Bildung und Forschung, the Ministerium für Wissen-
schaft, Forschung und Kunst des Landes Baden Württemberg is
gratefully acknowledged. We would like to thank the referees for
valuable suggestions.
(C-15’), 19.3 (4Ј-CH3), 22.7 (C-14Ј), 27.0–33.2 (C-3Ј, C-4Ј, C-6Ј, C- [1] a) P. Dominguez de Maria, Angew. Chem. 2008, 120, 7066–
7075; Angew. Chem. Int. Ed. 2008, 47, 6960–6968; b) Z. Fei,
T. J. Geldbach, D. Zhao, P. J. Dyson, Chem. Eur. J. 2006, 12,
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Wiley-VCH, Weinheim, 2003; e) P. Wasserscheid, W. Keim, An-
gew. Chem. 2000, 112, 3926–3945; Angew. Chem. Int. Ed. 2000,
39, 3772–3789; f) T. Welton, Chem. Rev. 1999, 99, 2071–2083.
[2] a) A. Winkel, P. V. G. Reddy, R. Wilhelm, Synthesis 2008, 999–
1016; b) X. Chen, X. Li, A. Hu, F. Wang, Tetrahedron: Asym-
metry 2008, 19, 1–14; c) G. Imperato, B. König, C. Chiappe,
7Ј, C-8Ј, C-9Ј, C-10Ј, C-11Ј, C-12Ј, C-13Ј), 36.7 (C-5Ј), 62.8 (C-1Ј),
128.5 (C-3, C-5), 144.7 (C-4), 145.4 (C-2, C-6) ppm. FTIR (ATR):
ν = 3119 (w), 2956 (s), 2922 (s), 2852 (s), 2178 (br), 1966 (br), 1573
˜
(s), 1465 (s), 1381 (w), 1170 (vs), 1054 (vs), 847 (w), 752 (s), 650
(w), 624 (s), 622 (s) cm–1. C21H38BF4N (391.34): calcd. C 64.95, H
9.79, N 3.58; found C 64.88, H 9.83, N 3.60. MS (ESI, +ve): m/z
= 304.3 [M]+, 148.1, 132.1, 120.1, 106.1, 93.1, 80.0. MS (ESI, –ve):
m/z = 87.0 [BF4]–. HMRS (ESI): calcd. for [C21H38N]+ 304.2999;
found 304.3002 [M]+.
5608
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 5601–5609

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Received: July 1, 2009
Published Online: September 23, 2009
Eur. J. Org. Chem. 2009, 5601–5609
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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