The azulene ring as a structural element in liquid crystals

Article abstract of DOI:10.1039/a606139g

A new approach to the synthesis of azulene liquid crystals is described based on Hafner's procedure involving reaction of a pyridinium salt with a cyclopentadienide. The preparation of a variety of liquid crystalline materials using this method is described. Variants are reported with single substituents on the azulene ring in the 6-position and doubly substituted in the 2,6-positions. The effect of the azulene ring as a core or dipolar terminal structural element is explored. 6-(5-Alkyl-1,3-dioxan-2-yl)azulenes are shown to exhibit smectic A phases and 2-cyclohexyl-6-(5-tridecyl-1,3-dioxan-2-yl)azulene show smectic A and B phases. Phase characterisation of the materials is recorded together with X-ray measurements on the smectic A phase of one representative compound. Results of dichroism studies on the azulene mesogens are also briefly reviewed.

Full text of DOI:10.1039/a606139g

The azulene ring as a structural element in liquid crystals
ˆ
Sian E. Estdale, Roger Brettle, David A. Dunmur and Charles M. Marson
Department of Chemistry, University of Sheffield, Sheffield, UK S3 7HF
A new approach to the synthesis of azulene liquid crystals is described based on Hafner’s procedure involving reaction of a
pyridinium salt with a cyclopentadienide. The preparation of a variety of liquid crystalline materials using this method is
described. Variants are reported with single substituents on the azulene ring in the 6-position and doubly substituted in the 2, 6-
positions. The effect of the azulene ring as a core or dipolar terminal structural element is explored. 6-(5-Alkyl-1,3-dioxan-2-
yl)azulenes are shown to exhibit smectic A phases and 2-cyclohexyl-6-(5-tridecyl-1,3-dioxan-2-yl)azulene show smectic A and B
phases. Phase characterisation of the materials is recorded together with X-ray measurements on the smectic A phase of one
representative compound. Results of dichroism studies on the azulene mesogens are also briefly reviewed.
The essential structure of a calamitic mesogen incorporates a
rigid core with a flexible terminal chain, and often a polar end
group, and mesophase behaviour is strongly dependent on the
nature of the core. In the search for new mesogenic structures,
the azulene ring system potentially opens up a whole new
Simple alkyl propane-1,3-diols were prepared by reacting
diethyl malonate with the appropriate alkyl halide and then
reducing the ester groups with LiAlH ; 2-(4-alkyloxyphenyl)-
4
propane-1,3-diols were prepared by reacting ethyl 4-alkoxy-
phenylacetates with diethyl oxalate; the product was then
range of liquid crystal types. The azulene ring C
H
is a non-
decarbonylated and reduced with LiAlH .
10 10
4
benzenoid aromatic hydrocarbon with an intrinsic dipole
moment (1.08 D) which is delocalised over the whole ring.1
Azulenes are chromophores: the deep blue colour of the parent
compound arises from the electronic transition from the highest
occupied molecular orbital to the lowest unoccupied antibond-
The products derived from Scheme 1 were a mixture of cis
and trans isomers which were separable by MPLC or HPLC,
and were assigned by the characteristic 1H NMR spectra for
the two CH groups on the dioxan-2-yl ring. For the cis-
2
isomers, the chemical shift difference between the axial and
ing orbital (the 1L band).2 The azulene ring system is planar
equatorial hydrogens is small whereas a large chemical shift
difference is observed for the trans isomers and this character-
istic pattern agrees with previously published results.12
b
and thermodynamically stable, although the 10p electrons
display the reactivity expected of an aromatic system.
Substitution of the ring can alter the wavelength of this
absorption band resulting in different colours for different
azulene derivatives.
Praefcke and Schmidt3 reported the synthesis of substituted
azulenes linked to nematogenic alkylcyclohexanes by an ester
group following the Nozoe procedure.4 We have also used this
route to produce mesogenic azulenes5 with alkylbiphenyls as
the mesogenic moiety. In 1990, a series of patents by Mitsubishi
described the synthesis of a range of 2-substituted,6 6-substi-
tuted7 and 2,6-disubstituted azulenes8–10 using the Nozoe route,
some of which were mesogenic. Only limited data were pre-
sented on the mesophase behaviour of these compounds which
were mostly examined as solutes in a nematic host material.
The mesophase properties of previously reported azulene based
liquid crystals are summarised in Table 1.
Attempts were also made to prepare mesogenic azulenes
with a phenyl ring instead of the dioxan-2-yl ring. Two
homologues 2a,b were prepared by different methods.
Deprotection of 1a with dilute hydrochloric acid gives azulene-
6-carbaldehyde which was reacted with the appropriate
Wadsworth–Emmons reagent to give 6-(4-hexyloxystryryl)-
azulene, which rapidly decomposed. Reduction of the double
bond gave 2a. The C analogue, 2b was prepared by reducing
10
the double bond of the appropriate stilbazole, quaternising the
product with 1-bromobutane and reacting the resulting pyri-
dinium salt with sodium cyclopentadienide.
Synthesis
In order to prepare potentially mesogenic azulenes without
ester linkages, we adopted the Hafner synthesis11 where an N-
alkyl-4-methylpyridinium salt was reacted with sodium cyclo-
pentadienide to give 6-methylazulene (see Schemes 1 and 2).
In a similar way we prepared 6-(diethoxymethyl)azulene 1a
by reaction of sodium cyclopentadienide with 4-(diethoxy-
methyl)pyridinium bromide. Alternatively, reaction with
monosubstituted sodium cyclopentadienides gave a mixture of
1,6- and 2,6-disubstituted azulenes which, in some cases, were
separable by HPLC. Transacetalation of the diethoxymethyl
group with 2-substituted propane-1,3-diols then gave substi-
tuted azulenes, some of which were mesogenic.
Mesophase Behaviour
Of the compounds synthesised, the trans isomers of 1e–k, 1n
and 1p were mesogenic. Table 2 shows the transition tempera-
tures for compounds 1e–k which showed a monotropic smectic
A phase. These trans isomers exhibited two crystal forms (K
1
and K ) which melted at different temperatures. The observed
2
phase sequence is shown in Fig. 1 and illustrates the trends in
melting points of the two crystal forms and the S phase. (For
A
the two metastable crystal states: K corresponds to the melting
1
point on initially heating the crystal from room temperature,
J. Mater. Chem., 1997, 7(3), 391–401
391

Table 1 Transition temperatures and wavelengths of visible absorption of mesogenic azulenes previously reported in the literature
transition tempa/°C
R
R
R
R
l
/nm
K
N
I
ref.
1
2
3
4
max
H
H
H
H
H
H
H
CO Et
CO Et
$
$
$
$
$
$
$
136
$
$
$
$
$
$
$
(110.5)
(121.9)
(115.9)
(89.3)
153.2
$
$
$
$
$
$
$
3
3
3
3
3
5
5
2
2
CO Me CO Me
149
2
2
CO Et
CO Et
480
123.7
104.5
86.1
144
2
2
CO Pr
CO Pr
2
2
CO Et
H
510
2
CO Et
CO Et
(78.6)
(145)
2
2
CO Et
H
146
2
CO Et
CO Et
475
476
$
$
122
118
$
$
(111)
$
$
8
7
2
2
H
H
H
H
H
H
(122.6)
566
$
106.7
$
119.4
$
7
aParentheses indicate a monotropic transition.
˚
and K is the melting point when heating the crystal phase
calculated to be 27 A. Molecular modelling calculations were
then made in an attempt to describe the molecular arrange-
ment. At 0 K, the molecular length was determined from
2
formed on cooling). For compounds where K is lower than
2
the monotropic smectic A transition temperature an enanti-
˚
otropic S phase is observed.
MACROMODEL to be 27.56 A, which is close to the observed
A
The trans isomer of 1n showed a crystal B phase at around
value for the inter-layer spacing of this smectic A phase. An
even closer value is obtained when part of the molecule is
tilted with respect to the smectic layers; this has the effect of
shortening the apparent length of the molecule and calculations
170 °C and was identified by the lancet texture observed on
cooling from the isotropic phase. For compound 1p, where the
2-substituent is an unsubstituted cyclohexyl ring, smectic A
(144 °C) and smectic hexatic B (117°C) phases were observed.
Compound 1q was prepared as it was hoped that the molecular
length could then be extended with a collinear chain on the
cyclohexyl ring; however the cis and trans isomers were insepar-
able by HPLC.
˚
predict a value of 26.9 A at 300 K. However, modelling the
molecule at 357 K, the value for the molecular length decreases
˚
to 23.65 A. The entropy of the system is now greater, and this
manifests itself in thermal agitation of the alkyl chain which is
no longer fully extended. From this result it is possible to rule
Addition of a 2-cyclohexyl substituent (compound 1p)
out a monolayer structure for this S phase, since for the
A
increases the thermal stability of the S phase compared to
temperatures at which the phase is observed, there will be
A
the singly substituted 6-(tridecyl-1,3-dioxan-2-yl)azulene, 1h
some thermal agitation of the alkyl chain, and the measured
molecular length must be less than the calculated value with
a fully extended chain.
which showed a monotropic smectic A phase, such that an
enantiotropic phase is now observed. This molecule incorpor-
ates an aromatic ring with saturated cyclic groups either side
of it, which traditionally has been considered unfavourable for
mesogenic behaviour. Potentially, this molecule opens up a
new series of mesogens and it is expected that the addition of
a terminal alkyl chain on to the cyclohexyl ring will lower the
clearing points and transition temperatures of the observed
mesophases.
In considering how the molecules are arranged within the
layers, the intermolecular interactions must also be considered.
Azulene has a distributed dipole moment and dipolar reson-
ance forms of azulene will contribute to the intermolecular
interactions in the smectic mesophase. It has been reported in
the literature13,14 that only anti-azulenophanes of the type
shown (Fig. 2) can be formed, since this minimises the energy
of both the resonance and electrostatic interactions between
the interacting azulene pairs. For the corresponding syn-
azulenophase these interactions would be repulsive. It is
Small angle X-ray measurements were made for compound
1f, 6-(5-undecyl-1,3-dioxan-2-yl)azulene. From the data
obtained, an average value for the inter-layer spacing was
392
J. Mater. Chem., 1997, 7(3), 391–401

that involves extensive interdigitation of the alkyl chains, which
accounts for both the dipolar interactions of the azulene ring
and the thermal disorder of the alkyl chains.
Linear Dichroism
Since azulene derivatives are coloured, their use as dichroic
materials in liquid crystal devices is of some interest.
Measurement of the linear dichroism of a number of non-
mesogenic and mesogenic compounds dissolved in suitable
nematic host materials have been reported.16 Measurements
were also carried out on three compounds prepared in this
work. From these studies it is possible to determine the degree
of order of the host azulene molecules and the angle made
by the transition moment to the long molecular axis. For
the parent azulene, the transition moment responsible for
the characteristic blue colour is polarized perpendicular to the
axis2 through carbon atoms 2 and 6. Substitution of the
azulene ring and attachment of different terminal groups
change the absorption frequency and the angle of the transition
moment with respect to the molecular axis. Consequently, it
is possible to make azulene liquid crystal mixtures having
different colours and with either positive or negative linear
dichroism. In Table 3 absorption frequencies and dichroic
ratios are summarised for a range of azulene derivatives: a
dichroic ratio of less than one indicates that the optical
absorption perpendicular to the azulene molecular axis is
larger than along the axis.
Conclusions
New 6-substituted azulenes were successfully synthesised by
reacting functionalised N-alkylpyridinium salts with sodium
cyclopentadienide to give mesogenic azulenes where the azu-
lene ring was incorporated as an end group. The preparation
of 6-(diethoxymethyl)azulene 1a and azulene-6-carbaldehyde
was significant as they are functionalised azulenes which may
be reacted further to give new 6-substituted azulene com-
pounds. The development of the transacetalation reaction of
6-(diethoxymethyl)azulene led to a new homologous series of
mesogenic azulenes which exhibited monotropic smectic A
phases in the range 78 to 86 °C. These compounds are the first
reported azulenes to show a smectic phase. In these compounds
it may be argued that the azulene ring has a dual role, and is
behaving both as part of the core and as a polar end group.
Molecular modelling substantiated the claim that the dipolar
interactions of adjacent azulene rings are important in
determining the intermolecular interactions which results in
the observed smectic A layered structure, with the alkyl chains
extensively interdigitated.
Scheme 1
H
O
OH
OH
O
O
N
Attempts to extend the core led to the synthesis of 6-[5-(4-
dodecyloxyphenyl)-1,3-dioxan-2-yl]azulene, 1n. A crystal B
phase was observed in the range 170–190 °C. This contrasts
with related compounds without a phenyl group as part of the
core, which form a smectic A phase approximately 100 °C
lower. It was also possible to prepare potential azulene meso-
gens by hydrogenation of a stilbazole and reacting the quar-
ternised salt with sodium cyclopentadienide. Unfortunately,
the resultant 6-(4-decyloxyphenethyl)azulene, 2b was not
mesogenic, which can be attributed to the separation of the
aromatic rings by a flexible dimethylene linkage. (However,
the intermediate 4-(4∞-decyloxyphenethyl)pyridine was meso-
genic, and exhibited a smectic A phase in the range 159–222°C.)
New 1,6- and 2,6-disubstituted azulenes were synthesised by
the reaction of functionalised N-alkylpyridinum salts with
sodium monosubstituted cyclopentadienides. The synthesis of
N
Na+
–
Br–
O
O
O
O
+
N
Bu
1b
Scheme 2
expected that in the observed mesophase the azulene rings
would adopt a packing arrangement which minimises the
energy of these types of interactions, resulting in an anti-
parallel bilayer structure as illustrated (Fig. 3). A similar type
of alignment is observed in mesogens with strongly polar
2-cyclohexyl-6-(tridecyl-1,3-dioxan-2-yl)azulene 1p gave
a
mesogen which showed a smectic A and a smectic B phase in
groups.15 Our proposed structure for the S phase is a bilayer
the range 95–144 °C. All previously reported azulene mesogens
A
J. Mater. Chem., 1997, 7(3), 391–401
393

Table 2 Mesophase behaviour of azulene liquid crystals
transition temperatures (microscopy)
transition data (DSC)
cis
compound
mp
K
mp/°C
K mp/°C
(S /I)/°C
DH/kJ mol−1
T
/°C
DS J K−1 mol−1
1
2
A
onset
1c
1d
1e
1f
1g
1h
1i
81.4
100.1
—
—
83.6
99.6
—
—
94.5
94.5
76.8
83.9
4350
3350
3440
3150
4210
3290
4000
82
79
79
79
80
77
75
12.3
9.5
96.9
97.8
—
(84.1)
97.5
98.5
78.5
80.0
86.0
88.0
90.0
85.0
9.8
99.7
101.1
102.1
102.8
103.9
84.0
9.0
100.2
102.1
103.4
(83.9)
(79.5)
(78.9)
11.9
1j
1k
9.4
11.5
are linked through ester groups. It is anticipated that substi-
tution of the cyclohexyl ring by an alkyl chain will lead to a
new homologous series with lower clearing points and trans-
ition temperatures.
The linear dichroism of some azulene mesogens was deter-
mined by measuring the order parameter of these compounds
as dyes in liquid crystal hosts. The optical order parameters
were low as a result of the large angle which the transition
moment makes with the molecular axis; in some cases this
angle was close to the magic angle of 54°44∞ at which the
dichroism is zero. As a result of the large angle, it was possible
to vary the sign of the dichroism by varying the substituents
on the azulene ring. However, these compounds are not
suitable for use in guest–host displays despite the high extinc-
tion coefficients.
Fig. 1 Phase diagram of compounds 1c –k: (a) K –I; (1) S –I; (p)
Various aspects of the synthesis and physical properties of
azulene liquid crystals have been explored in this work. It is
evident that the synthesis of azulene is difficult and having
tried a number of routes, the most successful method for this
work involved the reaction of N-alkylpyridinium salts with
sodium cyclopentadienide. However, the development of new
azulene based liquid crystals is restricted by the limited syn-
thetic routes currently available.
1
A
K – S ; (c) K –I
2
A
2
Experimental
Fig. 2 Structures of the azuleneophanes
Reactions sensitive to moisture and air were carried out in
flame-dried glassware under nitrogen or argon using freshly
distilled solvents. Solvents were dried and purified according
to literature methods. Thin-layer chromatography on TLC
aluminium sheets pre-coated with silica gel (Merck 69) F
254
was used to monitor reactions and to establish the purity of
samples. TLC plates were inspected using UV light or devel-
oped with iodine vapour. Oil-free sodium hydride was obtained
by washing with dry light petroleum in an argon atmosphere.
Amberlyst 15 (H+) ion-exchange resin was used in transacetal-
ation reactions. Column chromatography separations were
performed on silica gel (Merck 60) or neutral silica (Merck,
60) as the stationary phase. Loading of the sample was carried
out either as a concentrated solution of the mixture in the
solvent used for the mobile phase, or whenever the mixture
was only sparingly soluble in the eluent, it was supported on
silica gel by dissolving in a solvent, adding silica and evaporat-
ing the slurry to dryness to leave a powder which was poured
on to the top of the column. Organic solutions were dried
over magnesium sulfate unless otherwise stated. Melting points
were determined using either a Reichert-Kofler hot-stage
¨
apparatus or a Zeiss-Labpol microscope equipped with crossed
polarisers and a Linkam hot-stage with integrated temperature
controller, and are uncorrected. Elemental analyses were per-
formed by the University of Sheffield Microanalytical Service.
Low resolution mass spectra were recorded using a Kratos
MS 25 mass spectrometer. High resolution mass spectra was
recorded using a Kratos MS 60 mass spectrometer to give
accurate mass values. 1H and 13C NMR spectra were recorded
Fig. 3 Proposed layer structure of the smectic A phase involving
extensive interdigitation
394
J. Mater. Chem., 1997, 7(3), 391–401

Table 3 Absorption frequencies and dichroic ratios for a range of azulene derivatives
compound
l
/nm
e
/cm2 mol−1
dichroic ratio A /A
ref.
17
max
max
II
)
548
280000
1.0
565
590
340000
440000
1.0
17
17
1.44
480
510
468
720000
630000
560000
1.8a
2.1a
2.4
3
3
5
595
550
565
320000
354000
340000
0.72
0.64
0.50
—
—
—
aExtrapolated from literature values.
using SiMe as an internal standard in stated solvents.
10% K CO solution (75 ml). This was extracted with diethyl
4
2
3
Multiplicities are represented by the following abbreviations:
ether (3×50 ml), dried and reduced to leave a colourless oil.
Purification by vacuum distillation gave unreacted pyridine-4-
carbaldehyde, bp 73–74°C, 0.5 mmHg and 4-(diethoxymethyl)-
pyridine as a colourless oil, bp 75–76 °C, 0.5 mmHg, 19 g, 81%;
s, singlet; d, doublet; t, triplet, q, quartet; m, multiplet; br,
broad signal. Coupling constants, (J) are given in Hz.
4-(Diethoxymethyl)pyridine
d
(250 MHz, CDCl ) 1.25(t, 6H, J 7, 2Me); 3.58[m, 4H,
H
3
2(OCH Me)]; 5.50[s, 1H, pyridine-CH-(OEt) ]; 7.40(d, 2H, J
This compound was prepared by adapting the procedure of
Popp and McEwen,17 but full experimental details are given
below. A 13.5% solution of hydrogen bromide in ethanol was
prepared by cooling ethanol (88 ml) to 0 °C under nitrogen
and adding acetyl bromide (12 ml) dropwise. To a portion
of this solution (52 ml) pyridine-4-carbaldehyde (11.2 g,
105 mmol) was added to give a white precipitate and a yellow
solution which was stirred at 20 °C for 90 h. Dry benzene
(100 ml) was then added and any water formed during the
reaction, removed by azeotropic distillation through a Soxhlet
2
2
6, pyridine); 8.70(d, 2H, J 6, pyridine); d (63 MHz, CDCl )
C
3
15.0(q, 2C, 2Me); 61.2[t, 2C, 2(OCH Me]; 99.8[d, 1C, pyri-
2
dine-CH-(OEt) ]; 121.6(d, 2C, pyridine); 147.6(s, 1C, pyridine);
2
149.9(d, 2C, pyridine); m/z (EI) 181(M+, 90%).
N-Butyl-4-(diethoxymethyl)pyridinium bromide
4-(Diethoxymethyl)pyridine (4 g, 22.0 mmol) was dissolved in
dry ethanol (10 ml) and 1-bromobutane (4.56 g, 33.0 mmol)
added. The mixture was heated at reflux for 16 h. The ethanol
and excess 1-bromobutane were evaporated under reduced
pressure. The resulting yellow oil was left under high vacuum
to remove any remaining solvent to give N-butyl-4-(diethoxy-
extractor containing MgSO , over a period of 24 h. Benzene
4
and ethanol were evaporated under reduced pressure to give
an orange solid which was made alkaline (pH 9) by adding
J. Mater. Chem., 1997, 7(3), 391–401
395

methyl)pyridinium bromide, (6.0 g, 85%),
d
(250 MHz,
2-yl)pyridinium bromide remained contaminated with pro-
H
CDCl ) 0.95[t, 3H, N(CH ) CH ]; 1.25[t, 6H, 2(OCH CH )];
pane-1,3-diol, m/z (+ve FAB MS) C H NO 222 (M+,
3
2 3
3
2
3
13 20
2
1.45[m, 2H, N(CH ) CH Me]; 2.05(m, 2H, NCH CH C H );
100%).
2 2
2
2
2 2 5
2.70(2H, br s, H O); 3.65[q, 4H, 2(OCH CH )]; 5.05(t, 2H,
2
2
3
NCH C H ); 5.70(s, 1H, (OEt) -CH-pyridine); 8.15(d, 2H, pyri-
2 3
7
2
6-(1,3-Dioxan-2-yl)azulene, 1b
dine); 9.60(d, 2H, pyridine); d (63 MHz, CHCl ) 12.7(q, 1C,
C
2
3
C H CH ); 14.2[q, 2C, 2(OCH CH )]; 18.4(t, 1C, CH ); 32.9(t,
Freshly distilled cyclopentadiene (2.19 ml, 33.2 mmol) was
added dropwise to sodium hydride (0.40 g, 16.7 mmol) in THF
(30 ml) at 0 °C over 30 min and then allowed to warm to
20°C. Crude N-butyl-4-(1,3-dioxan-2-yl)pyridinium bromide
(1.9 g, 6.28 mmol), dissolved in THF (10 ml), was then added
to the pink solution giving a colour change to dark orange
and then brown. The mixture was heated at reflux for 3 h.
Water (50 ml) was then added and the mixture extracted
with dichloromethane (4×50 ml): the combined organic layers
were dried and solvent evaporated under reduced pressure.
Purification by column chromatography on silica using
dichloromethane as eluent gave 6-(1,3-dioxan-2-yl)azulene as
dark blue microprisms. Recrystallisation from pentane gave
the pure product, (0.195 g, 15%), mp 110–111°C (Found: C,
78.3; H, 6.6; C H O calculated: C, 78.5; H, 6.6%); d
3
7
3
2
3
2
1C, CH ); 33.0(t, 1C, CH ); 60.2(t, 1C, CH ); 61.5[t, 2C,
2
2
2(OCH CH )]; 91.3(d, 1C, (OEt) -CH-pyridine); 97.4(d, 2C,
2
3
2
2-pyridine); 125.3(d, 2C, 3-pyridine); 156.7(s, 1C, 4-pyridine);
m/z (+ve FAB MS) C H NO 238 (M+, 100%).
14 24
2
6-(Diethoxymethyl)azulene, 1a
Freshly distilled cyclopentadiene (2.42 g, 36.6 mmol) was added
dropwise over 30 min to sodium hydride (0.88 g, 36.6 mmol)
in THF (70 ml) at 0 °C and then allowed to warm to 20 °C.
N-butyl-4-(diethoxymethyl)pyridinium
bromide
(17.5 g,
55.0 mmol) dissolved in THF (50 ml) was then added to the
pinkish solution which went dark red and then brown. The
mixture was heated at reflux for 3 h, a blue spot being indicated
by TLC. THF was evaporated under reduced pressure to leave
a black viscous oil to which silica was added. Purification by
column chromatography using light petroleum (bp 40–60°C)
as eluent gave 6-(diethoxymethyl)azulene as a dark blue oil
14 14
2
H
(250 MHz, CDCl ) 1.45(m, 1H, dioxanyl); 2.25(m, 1H, diox-
3
anyl); 4.00(m, 2H, dioxanyl); 4.30(m, 2H, dioxanyl); 5.50(s,
1H, H-C-azulene); 7.40(d, 2H, J 10, azulene H-C1,3); 7.40(d,
2H, J 4, azulene H-C5,7); 7.90(t, 1H, J 4, azulene H-C2); 8.40(d,
2H, J 10, azulene H-C4); d (60 MHz, CDCl ) 25.7(t, 1C,
(2.72 g, 32%). Further purification using a Kugelrohr appar-
¨
C
3
CH ); 67.6 [t, 2C, (OCH ) ]; 104.3(d, 1C, H-C-azulene);
atus gave 1a (Found: C, 78.0; H, 7.9. C H O calculated: C,
2
2 2
15 18
2
118.1(d, 2C, azulene C1,3); 121.1(d, 2C, azulene C5,7); 135.2(d,
2C, azulene C4,8); 135.9(d, 1C, azulene C2); 140.1(s, 2C, azulene
C3a,8a); 146.0(s, 1C, azulene C6); m/z (EI) 214 (M+, 83%).
78.2, H, 7.9%), d (250 MHz, CDCl ) 1.25(t, 6H, 2Me); 3.6[m,
H
3
4H, 2(OCH CH )]; 5.45[s, 1H, HC(OEt) ]; 7.40(m, 4H, azu-
2
3
2
lene H-C1,3,5,7); 7.90(t, 1H, J 4, azulene H-C2); 8.35 (d, 2H,
azulene H-C4,8); d (60 MHz, CDCL ) 15.2 (q, 1C, Me); 61.8[t,
C
3
2C, (OCH Me) ]; 104.4[d, 1C, H-C(OEt) ]; 118.1(d, 2C, azu-
2
2
2
cis- and trans-6-(5-Pentyl-1,3-dioxan-2-yl)azulene, 1c
lene C1,3); 121.4(d, 2C, azulene C5,7); 135.8(d, 2C, azulene
C4,8); 137.3(s, 1C, azulene C2); 139.9(s, 2C, azulene C3a,8a);
147.3(s, 1C, azulene C6); m/z (EI) 230 (M+, 80%).
Compound 1a (0.35 g, 1.52 mmol) and 2-pentylpropane-1,3-
diol (0.33 g, 2.28 mmol) were stirred together in dry benzene
(10 ml) with an ion exchange resin (catalytic amount) at 100 °C
for 6 h and the reaction was followed by TLC. Purification of
the products was attempted by column chromatography on
silica using hexane–dichloromethane (351) as eluent which
gave the mixture of isomers as blue microprisms (170 mg,
39%). These were shown, by analytical HPLC, to be a mixture
of the cis- and trans-forms in a ratio of 253. Separation was
achieved using reverse phase HPLC to give the pure isomers,
cis-6-(5-pentyl-1,3-dioxan-2-yl)azulene, mp 81.4°C; (M+
Found: 284.1785, C H O requires: 284.17762); d (250 MHz,
4-(1,3-Dioxan-2-yl )pyridine
A 13.5% solution of HBr in propane-1,3-diol was prepared by
cooling propane-1,3-diol (88 ml) to 0 °C under nitrogen and
adding acetyl bromide (12 ml) dropwise. To a portion of this
solution (52 ml) was added pyridine-4-carbaldehyde (11.2 g,
105 mmol) and the solution was stirred at 20 °C for 90 h. Dry
benzene (100 ml) was then added and any water formed during
the reaction, removed by azeotropic distillation through a
19 24
2
H
CD Cl ) 0.9(t, 3H, J 7, Me); 1.35[m, 7H, CH (CH ) Me, C-
Soxhlet extractor containing MgSO , over a period of 24 h.
2
5
2
9
2
2 3
2 2
4
HC H ]; 1.83(m, 2H, CH C H ); 4.10(m, 4H, (OCH ) ]; 5.52(s,
Benzene and ethanol were then evaporated under reduced
2 4
9
1H, H-C-azulene); 7.38(d, 2H, J 4, azulene H-C1,3); 7.38(d, 2H,
J 10, azulene H-C5,7); 7.90(t, 1H, J 4, azulene H-C2); 8.37(d,
2H, J 10, azulene H-C4,8); d (63 MHz, CD Cl ) 14.1(q, 1C,
pressure to give an orange solid which was made alkaline
(pH 9) by adding 10% K CO solution (75 ml). This was
2
3
extracted with diethyl ether (3×50 ml), dried and reduced
to leave a brown oil. Purification by vacuum distillation
gave unreacted pyridine-4-carbaldehyde and a small amount
of product, bp 68–71 °C at 0.6 mmHg (3.62 g, 21%) as a
mixture of 4-(1,3-dioxan-2-yl)pyridine (1.05 g, 6.1% from
C
2 2
Me); 22.7(t, 1C, CH ); 27.3(t, 1C, CH ) 29.6(t, 1C, CH); 32.0(t,
2
2
1C, CH ); 34.4[d, 1C, HC(CH O) ]; 71.0(t, 2C, (CH O) ];
2
2
2
2
2
104.7(d, 1C, H-C-azulene); 118.2(d, 2C, azulene C1,3); 121.2(d,
2C, azulene C5,7); 136.1(d, 2C, azulene C4,8); 137.6(d, 1C,
azulene C2); 140.1(s, 2C, azulene C3a,8a); 146.0(s, 1C, azulene
C6); m/z (EI) 284 (M+, 92%); and trans-6-(5-pentyl-1,3-dioxan-
2-yl) azulene, mp 100.1°C; (M+ Found: 284.1783, C H O
1H NMR) and propane-1,3-diol as
a
colourless oil at
71–100 °C at 0.6 mmHg, d (220 MHz, CDCl ); 1.70(m, 2H,
H
3
2
OCH CH CH O); 4.0(m, 4H, OCH CH CH O); 5.50(s, 1H
19 24 2
2
2
2
2
2
requires: 284.17762); d (250 MHz, CD Cl ) 0.90(t, 3H, J 7,
1,3-dioxan-2-yl-CH-pyridine); 7.70(d, 2H, 2-pyridine); 8.70(d,
2H, 3-pyridine); and signals for propane-1,3-diol; m/z (+CI)
C H NO 165 (M+, 100%).
H
2 2
Me); 1.10(m, 2H, C H CH Me); 1.30[m, 6H, (CH ) C H ];
3
7
2
2 3 2 5
2.20(m, 1H, C-HC H ); 3.58(t, 2H, J 12, OCH ); 4.28(q, 2H,
5
9
2
9
11
2
J 4.5, OCH ); 5.45(s, 1H, H-C-azulene); 7.38(d, 2H, J 4, azulene
2
H-C1,3); 7.38(d, 2H, J 10, azulene H-C5,7); 7.90(t, 1H, J 4,
azulene H-C2); 8.35(d, 2H, J 10, azulene H-C4,8); d (63 MHz,
N-Butyl-4-(1,3-dioxan-2-yl)pyridinium bromide
C
CD Cl ) 14.1(q, 1C, Me); 22.5(t, 1C, CH ); 26.0(t, 1C, CH );
2
2
2
2
2
The crude mixture of 4-(1,3-dioxan-2-yl)pyridine (1.05 g,
6.36 mmol) and 1-bromobutane (4.5 g, 33.0 mmol) was added
to dry ethanol (10 ml) and heated at reflux for 16 h, the
reaction being followed by TLC. The ethanol was evaporated
under reduced pressure but the product N-butyl-4-(1,3-dioxan-
28.2(t, 1C, CH); 32.0(t, 1C, CH ); 34.2[d, 1C, HC(CH O) ];
2
2
72.9[t, 2C, (CH O) ]; 104.3(d, 1C, H-C-azulene); 118.2(d, 2C,
2
2
azulene C1,3); 121.2 (d, 2C, azulene C5,7); 136.0(d, 2C, azulene
C4,8); 137.6(d, 1C, azulene C2); 140.1(s, 2C, azulene C3a,8a);
145.9(s, 1C, azulene C6); m/z (EI) 284 (M+, 100%).
396
J. Mater. Chem., 1997, 7(3), 391–401

The series of homologues were all prepared in a similar
H-C1,3,5,7 and phenyl); 7.95(t, 1H azulene H-C2); 8.45(d, 2H,
azulene H-C4,8); d (63 MHz, CDCl ) 41.1(d, 1C, H-C-Ph);
manner and the reaction conditions are outlined in Table A.
C
2 2
3
Table A
72.6[t, 2C, (OCH ) ]; 104.2(d, 1C, H-C-azulene); 118.3(d, 2C,
azulene C1,3); 121.2(d, 2C, azulene C5,7); 127.6(d, 1C, Ph);
temperature/°C,
cis5trans
ratio
127.7(d, 2C, Ph); 128.9(d, 2C, Ph); 136.0(d, 2C, azulene C4,8);
137.4(s, 1C, Ph) 137.7(d, 1C, azulene C2); 140.2(s, 2C, azulene
C3a,8a); 145.6(s, 1C, azulene C6); m/z (EI) 290 (M+, 85%).
This procedure was used to prepare 1m and 1n (Table C)
by reaction with the appropriate diol.
compound catalyst solvent
time/h
yield (%)
1d
1e
1f
1g
1h
1i
TsOH
—
55/48
22
16
13
23
6
253
255
153
153
153
153
153
153
i-e resin Benzene
i-e resin CH Cl
80/20
50/20
2
2
i-e resin Benzene
i-e resin Benzene
i-e resin Benzene
i-e resin Toluene
i-e resin Toluene
reflux/4
reflux/8
100/8
cis- and trans-6-[5-(4-Hexyloxyphenyl)-1,3-dioxan-2-yl]-
azulene, 1m
26
41
39
1j
1k
reflux/4
100/8
cis-6-[5-Hexyloxyphenyl)-1,3-dioxan-2-yl]azulene, mp 143 °C
(decomp.) and the trans-6-[5-(4-hexyloxyphenyl)-1,3-dioxan-
2-yl]azulene, mp 225°C, d (250 MHz, CD Cl ) 0.89(t, 3H,
All the above compounds gave 1H NMR, 13C NMR and mass
spectra analogous to those for the 6-(5-pentyl-1,3-dioxan-2-
yl)azulene isomers described above.
H
2
2
J
7, Me); 1.40[m, 6H, C H (CH ) Me]; 1.75(m, 2H,
2
4
2 3
CH CH C H ); 3.33(m, 1H, H-C-phenyl); 3.92(t, 2H, J 7,
2
2 4 9
The high resolution mass spectra values for each compound
dioxanyl CH ); 4.02(t, 2H, J 11.5, OCH C H ); 4.32(q, 2H, J
2
2 5 11
are given in Table B.
11.5, dioxanyl CH ); 5.6(s, 1H, H-C-azulene); 6.86(d, 2H, J 8.5,
Table B
2
phenyl); 7.16(d, 2H, J 8.5, phenyl); 7.38(d, 2H, J 4.5, azulene
H-C1,3); 7.42(d, 2H, J 10.5, azulene H-C5,7); 7.9(t, 1H, J 4.5,
molecular
formula
found
found
azulene H-C2); 8.39(d, 2H, J 10.5, azulene H-C4,8); d (63 MHz,
compound
calc.
cis
trans
C
CD Cl ) 14.2(q, 1C, Me); 23.0(t, 1C, CH ); 26.1(t, 1C, CH );
2
2
2
2
1d
1e
1f
1g
1h
1i
C
C
C
C
C
C
C
C
H
20 26
H
O
O
O
O
O
O
O
O
298.1933
354.2559
368.2715
382.2872
396.3028
410.3185
424.3341
438.3498
298.1941
354.2542
368.2719
382.2882
396.3046
410.3178
424.3348
438.3489
298.1926
354.2547
368.2711
382.2862
396.3012
410.3166
424.3346
438.3490
29.6(t, 1C, CH ); 32.0(t, 1C, CH ); 40.7[t, 1C, H-C-(OCH )];
2
2
2
2
2
2
2
2
2
2
2
68.5(t, 1C, OCH ); 73.1[d, 2C, dioxanyl 2(OCH )]; 104.3(d,
24 34
H
2
2
25 36
H
1C, H-C-azulene); 115.1(d, 2C, phenyl); 118.5(d, 2C, azulene
C1,3); 121.6(d, 2C, azulene C5,7); 129.0(d, 2C, phenyl); 129.6(s,
1C, phenyl); 136.2(d, 2C, azulene C4,8); 138.0(d, 1C, azulene
C2); 140.4(s, 2C, azulene C3a,8a); 146.4(s, 1C, phenyl); 158.9(s,
1C, azulene C6); m/z (EI) 390 (M+, 62%).
26 38
H
27 40
H
28 42
H
1j
1k
29 44
H
30 46
cis- and trans-6-(5-Phenyl-1,3-dioxan-2-yl)azulene, 1l
cis- and trans-6-[5-(4-dodecyloxyphenyl)-1,3-dioxan-2-yl]-
azulene, 1n
Compound 1a and 2-phenylpropane-1,3-diol (0.5 g, 3.26 mmol)
were stirred together with the ion-exchange catalyst at 60 °C
in dry THF (5 ml) for 2 h. The reaction was monitored by
TLC; when all the starting material had disappeared the
reaction mixture was filtered to remove the resin and the
product washed through with ethyl acetate. Purification by
column chromatography on silica, using light petroleum
(bp 40–60 °C)–ethyl acetate, 451, as eluent gave a mixture of
the cis- and trans-isomers as dark blue microprisms, 0.532 g,
53%. These were shown, by analytical HPLC to be a mixture
of the cis- and trans-forms in a ratio 152. Separation of the
isomers was achieved by reverse phase chromatography; recrys-
tallisation from diethyl ether–light petroleum gave the pure
isomers; cis-6-(5-phenyl-1,3-dioxan-2-yl)azulene, mp 123 °C
(M+ Found: 290.1302, C H O calculated: 290.1307); d
cis-6-[5-(4-Dodecyloxyphenyl)-1,3-dioxan-2-yl]azulene, mp
127°C (M+ Found: 474.3139, C H O calculated: 474.3134);
32 42
3
d
(250 MHz, CD Cl ) 0.86(t, 3H, J 7, Me); 1.26[m, 18H,
H
2 2
CH (CH ) Me]; 1.75(m, 2H, CH CH C H Me); 2.75(m, 1H,
2
2 9
2
2 9 18
CH-phenyl-OC H ); 3.94(t, 2H, OCH C
H
); 4.38[m, 4H,
12 25
2
2 11 23
2(dioxanyl CH )]; 5.68(s, 1H, dioxanylMCHMazulene); 6.89(d,
2H, J 9, phenyl ); 7.39(m, 4H, azulene H-C1,3,5,7); 7.53(d, 2H,
J 9, phenyl); 7.90(t, 1H, J 4, azulene H-C2); 8.39(d, 2H, J 11,
azulene H-C4,8); d (63 MHz, CD Cl ) 14.25(q, 1C, Me); 23.1(t,
C
2 2
1C, CH ); 26.4(t, 1C, CH ); 29.7[t, 2C, 2(CH )]; 29.8[t, 4C,
2
2
2
4(CH )]; 30.0(t, 1C, CH ); 32.3(t, 1C, CH ); 38.6(t, 1C, diox-
2
2
2
anyl-CH phenyl-OC H ); 68.4(t, 1C, OCH C H ); 72.2[d,
12 25
2 11 23
2C, dioxanyl 2(OCH )]; 104.8(d, 1C, dioxanyl-HC-azulene);
2
114.6(d, 2C, phenyl); 118.5(d, 2C, azulene C1,3); 121.6(d, 2C,
20 18
2
H
(250 MHz, CDCl ) 2.75(m, 1H, dioxanyl); 4.4(m, 4H, diox-
azulene C5,7); 129.7(d, 2C, phenyl); 135.2(s, 1C, phenyl);
136.3(d, 2C, azulene C4,8); 138.0(d, 1C, azulene C2); 140.4(s,
2C, azulene C3a,8a); 146.5(s, 1C, phenyl); 158.3(s, 1C, azulene
C6); m/z (EI) 474 (M+, 100%); and trans-6-[5-(4-dodecyloxy-
3
anyl); 5.79(s, 1H, H-C-azulene); 7.7(m, 2H, phenyl); 7.47(d,
2H, J 11, azulene H-C5,7); 7.35(m, 5H, phenyl and azulene H-
C1,3); 7.9(t, 1H, J 4, azulene H-C2); 8.45(d, 2H, J 11, azulene
H-C4,8); d (63 MHz, 2H acetone) 39.5(d, 1C, H-C-Ph); 72.1[t,
phenyl)-1,3-dioxan-2-yl]azulene, mp 206 °C (crystal S ) (M+
C
6
B
2C, (OCH ) ]; 104.9(d, 1C, H-C-azulene); 118.8(d, 2C, azulene
Found: 474.3123, C H O
calculated: 474.3134);
d
2 2
32 42
3
H
C1,3); 122.2(d, 2C, azulene C5,7); 126.9(d, 1C, Ph); 128.9(d, 2C,
(250 MHz, CD Cl ) 0.88(t, 3H, J 7, Me); 1.30[m, 18H,
2
2
Ph); 129.2(d, 2C, Ph); 136.5(d, 2C, azulene C4,8); 138.1(s, 1C,
Ph); 140.8(d, 1C, azulene C2); 144.3(s, 2C, azulene C3a,8a);
147.4(s, 1C, azulene C6); m/z (EI) 290 (M+, 45%); and trans-
6-(5-phenyl-1,3-dioxan-2-yl)azulene, mp 193 °C (M+ Found:
CH (CH ) Me]; 1.75(m, 2H, CH CH C H Me); 3.34(m, 1H,
2
2 9
2
2 9 18
CH-phenyl-OC H ); 3.94(t, 2H, J 7, OCH C H ); 4.04(t,
12 25
2 11 23
2H, J 11.5, dioxanyl CH ); 4.34(q, H, J 4.5, dioxanyl CH );
2
2
5.68(s, 1H, dioxanyl-CH-azulene); 6.88(d, 2H, J 9, phenyl );
7.17(d, 2H, J 9, phenyl); 7.42(m, 4H, azulene H-C1,3,5,7); 7.92(t,
290.1302,
C
H O calculated: 290.1307);
d
(250 MHz,
H
20 18
2
CDCl ) 3.45(m, 1H, dioxanyl); 4.10(t, 2H, dioxanyl); 4.45(q,
1H, J 4, azulene H-C2); 8.40(d, 2H, J 11, azulene H-C4,8); d
3
C
2H, dioxanyl); 5.65(s, 1H, H-C-azulene); 7.30(m, 9H, azulene
(63 MHz, CD Cl ) 14.24(q, 1C, Me); 23.1(t, 1C, CH ); 26.4(t,
2
2
2
Table C
compound
alkyl chain
OC H
catalyst
solvent
temperature/°C, time/h
yield (%)
cis5trans
1m
1n
i-e resin
THF
60/48
7
154
153
6
13
OC
H
i-e resin
THF
100/8
14
12 25
J. Mater. Chem., 1997, 7(3), 391–401
397

1C, CH ); 26.4(t, 1C, CH ); 29.6[t, 2C, 2(CH )]; 29.7[t, 4C,
CDCl ) 14.1(q, 1C, Me); 21.3(q, 1C, Me); 21.4(q, 1C, Me);
2
2
2
3
22.7(q, 1C, Me); 22.8(t, 1C, CH ); 26.4(t, 1C, CH ); 26.9(t, 1C,
4(CH )]; 30.0(t, 1C, CH ); 32.3(t, 1C, CH ); 40.7(t, 1C, diox-
2
2
2
2
2
anyl-HC phenyl-OC
H
); 68.4(t, 1C, OCH C H ); 73.1(d,
CH ); 28.2(t, 1C, CH ); 29.4(t, 1C, CH ); 29.5(t, 1C, CH );
2
2
2
2
12 25
2 11 23
29.7(t, 4C, CH ); 29.8(t, 1C, CH ); 30.5(d, 1C, CH); 31.9(t, 1C,
2C, dioxanyl 2(OCH )); 104.3(d, 1C, dioxanyl-HC-azulene);
2
2
2
CH ); 34.2(d, 1C, CH); 35.7(t, 1C, CH ); 39.6(d, 1C, CH);
115.1(d, 2C, phenyl); 118.5(d, 2C, azulene C1,3); 121.6(d, 2C,
2
2
42.9[t, 1C, H-C(CH O) ]; 48.2(d, 1C, neomenthyl H-C-azu-
azulene C5,7); 129.0(d, 2C, phenyl); 129.6(s, 1C, phenyl);
136.2(d, 2C, azulene C4,8); 138.0(d, 1C, azulene C2); 140.4(s,
2C, azulene C3a,8a); 146.4(s, 1C, phenyl); 158.9(s, 1C, azulene
C6); m/z (EI) 474 (M+, 100%).
2
2
lene); 72.9[t, 2C, 2(OCH Me)]; 104.6(d, 1C, dioxanyl H-C-
2
azulene); 119.6(d, 2C, azulene C1,3); 121.2(d, 2C, azulene C5,7);
133.7(d, 2C, azulene, C4,8); 139.7(s, 2C, azulene C3a,8a); 144.0(s,
1C, azulene C6); 158.5(s, 1C, azulene C2); m/z (EI) 506 (M+,
18%).
2-(+)-Neomenthyl-6-(diethoxymethyl)azulene
(+)-Neomenthylcyclopentadiene18 (2 g, 9.8 mmol, 1.1 equiv.)
was added to sodium hydride (0.21 g, 8.90 mmol, 1 equiv.) in
dry THF (30 ml) at 20 °C to give a slightly pink solution. After
30 min, when no further reaction was observed, N-butyl-4-
(diethoxymenthyl)pyridinium bromide (5.0 g, 15.0 mmol, 2
equiv.) in THF (20 ml) was added to give a dark brown
solution which was heated at reflux for 16 h. Solvent was
evaporated under reduced pressure and alumina added.
Purification by column chromatography was attempted on
basic alumina using hexane as eluent to give an unidentified
yellow oil and 2-(+)-neomenthyl-6-(diethoxymenthyl)azulene
as a dark blue oil 0.74 g, 22.6% (Found: 368.2706, C H O
1-Cyclohexyl-6-(diethoxymethyl)azulene and 2-cyclohexyl-6-
(diethoxymethyl)azulene
Cyclohexylcyclopentadiene, (1 g, 6.76 mmol) was added to
sodium hydride (0.2 , 8.33 mmol) in THF (30 ml) and heated
gently until the reaction had completed, to give a red solution.
Butyl-4-(diethoxymethyl)pyridine bromide (5.0 g, 15.0 mmol)
was added in THF (25 ml) and heated at reflux for 90 h.
Solvent was evaporated under reduced pressure and neutral
silica added to the dark brown oil. Purification by column
chromatography on neutral silica using light petroleum as
eluent gave a colourless oil identified as N-butyl-(4-ethoxycar-
25 36
2
bonyl-4-ethyl)dihydropyridine, 0.5 ml, 14%, d (250 MHz,
calculated: 368.2715); d (250 MHz, CDCl ) 0.8(t, 6H, 2Me);
H
H
3
CDCl ) 0.81(t, 3H, J 7.5, CH CH ); 0.89(t, 3H, J 7.5,
1.30(m, 18H, neomenthyl); 2.20(m, 1H, neomenthyl H-C-azu-
3
6
2
3
NC H CH ); 1.24(t, 3H,
J
7.5, COOCH CH ); 1.27(m,
lene); 3.60(t, 2H, OCH ); 3.55[m, 4H, 2(OCH Me)]; 7.30(s,
3
3
2
3
2H, NC H CH Me); 1.44(m, 2H, NCH CH C H ); 1.49(q,
2
2
2
4
2
2
2 2 5
2H, azulene H-C1,3); 7.35(d, 2H, azulene H-C5,7); 8.25(d, 2H,
azulene H-C4,8); d (63 MHz, CDCl ) 15.2(q, 2C, Me); 21.3(q,
2H, J 7.5, CH Me); 3.20(t, 2H, J 7, NCH C H ); 4.13(q,
2
2 3 7
2H, J 7, COOCH Me); 4.40(d, 2H, J 8, b-dihydropyridine);
C
3
2
1C, Me); 21.4(q, 1C, Me): 22.8(q, 1C, Me); 26.5(t, 1C, CH );
5.93(d, 2H, J 8, a-dihydropyridine); d (63 MHz, CDCl )
2
C
3
26.9(d, 1C, CH); 30.5(d, 1C, CH); 35.7(t, 1C, CH ); 39.6(d, 1C,
8.5(q, 1C, CH CH ); 13.8(q, 1C, NC H CH ); 14.1(q,
2
2
3
3
2
6
3
CH); 43.0(t, 1C, CH ); 48.2[d, 1C, (+)-neomenthyl H-C-
1C, COOCH CH ); 19.7(t, 1C, NC H CH Me); 32.3(d, 1C,
2
2
3
2
4
azulene]; 61.9[t, 2C, 2(OCH )Me]; 104.5(d, 1C, diethoxy H-
NCH CH C H ); 35.1(t, 1C, CH Me); 46.6(s, 1C, c-dihydro-
2
2
2 2
5
2
C-azulene); 119.6(d, 2C, azulene C1,3); 121.5(d, 2C, azulene
pyridine); 53.1(t, 1C, NCH C H ); 60.4(t, 1C, OCH Me);
2 3
7
2
C5,7); 133.6(d, 2C, azulene C4,8); 139.5(s, 2C, azulene C3a,8a);
145.3(s, 1C, azulene C6); 158.3(s, 1C, azulene C2); m/z (EI) 368
(M+, 50%).
98.4(d, 2C, b-dihydropyridine); 130.2(d, 2C, a-dihydropyridine);
176.5(s, 1C, COOEt), and a mixture of the isomers as a dark-
blue oil, 0.533 g, 25%. Separation of the isomers was achieved
by MPLC to give 1-cyclohexyl-6-(diethoxymethyl)azulene, as
a purple–blue oil, (Found: 312.2103, C H O calculated:
cis- and trans-2-Neomenthyl-6-(5-undecyl-1,3-dioxan-2-yl )-
azulene, 1o
21 28
2
312.2089); d (250 MHz, CD Cl ) 1.30[t, 6H, 2(OCH Me)];
H
2
2
2
1.70(m, 10H, cyclohexyl); 3.25(m, 1H, azulene CH-cyclohexyl);
3.55[m, 4H, 2(OCH Me)]; 5.35[s, 1H, (EtO) CH-azulene];
2-Neomenthyl-6-(diethoxymethyl)azulene (0.6 g, 1.63 mmol)
and 2-undecylpropane-1,3-diol (0.6 g, 2.61 mmol) were heated
to 60 °C together with an ion-exchange resin (catalytic amount)
in dry ethyl acetate (3 ml) for 1 h. The reaction was monitored
by TLC and solvent evaporated under reduced pressure when
starting material had disappeared. Purification was achieved
by column chromatography on neutral silica using light pet-
roleum–diethyl ether, 451, as eluent to give the mixture of
isomers as blue microprisms, 150 mg, 18%. Separation of the
isomers (cis/trans: 1/3) was achieved by HPLC to give cis-2-
neomenthyl-6-(5-undecyl-1,3-dioxan-2-yl)azulene, as a blue oil,
2
2
7.15(d, 2H, azulene H-C5,7); 7.2(d, 1H, azulene H-C3); 7.75(d,
1H, azulene H-C2); 8.15(d, 1H, azulene H-C4); 8.25(d, 1H,
azulene H-C4); d (63 MHz, CD Cl ) 15.4[q, 2C, 2(OCHMe)];
C
2 2
26.8(t, 1C, cyclohexyl); 27.6(t, 2C, cyclohexyl); 35.6(t, 2C,
cyclohexyl); 37.0(d, 1C, azulene CH-cyclohexyl); 62.4[t, 2C,
2(OCH Me)]; 105.1[d, 1C, (EtO) CH-azulene]; 117.3(d, 1C,
2
2
azulene C3); 120.1(d, 1C, azulene C5); 120.8(d, 1C, azulene C7);
132.6(d, 1C, azulene C2); 134.6(s, 1C, azulene C1); 135.1(d, 1C,
azulene C4); 135.8(d, 1C, azulene C8); 137.9(s, 1C, azulene
C3a); 140.6(s, 1C, azulene C8a); 148.0(s, 1C, azulene C6); m/z
(EI) 312 (M+, 100%), and 2-cyclohexyl-6-(diethoxymethyl)-
azulene, as blue microprisms, mp 58–59 °C (Found 312.2074,
C H O calculated: 312.2089); d (250 MHz, CD Cl ) 0.90[t,
d
(250 MHz, CDCl ) 1.30(m, 43H, neomenthyl and C
H
);
H
3
2
11 23
4.05[s, 4H, 2(OCH )]; 5.45(s, 1H, dioxanyl H-C-azulene);
7.20(s, 2H, azulene H-C1,3); 7.25(d, 2H, azulene H-C5,7); 8.25(d,
21 28
2
H
2
2
2H, azulene H-C4,8); d (63 MHz, CDCl ) 14.1(q, 1C, Me);
6H, 2(OCH Me)]; 1.80(m, 10H, cyclohexyl); 2.90(m, 1H, azu-
C
3
2
21.2(q, 1C, Me); 21.4(q, 1C, Me); 22.7(q, 1C, Me); 22.8(t, 1C,
CH ); 26.4 (t, 1C, CH ); 26.9 (t, 1C, CH ); 27.6 (t, 1C, CH );
lene CH-cyclohexyl); 3.65[m, 4H, 2(OCH Me)]; 4.45 [s, 1H,
2
(EtO) CH-azulene]; 7.20(s, 2H, azulene H-C1,3); 7.30(d, 2H,
2
2
2
2
2
28.2 (t, 1C, CH ); 29.4(t, 1C, CH ); 29.7[t, 5C, 5(CH )]; 30.5(d,
azulene H-C5,7); 8.20(d, 2H, azulene H-C4,8); d (63 MHz,
2
2
2
C
1C, CH); 31.9(t, 1C, CH ); 34.4(d, 2C, CH); 35.7(t, 1C, CH );
CD Cl ) 5.2[q, 2C, 2(OCH Me)]; 16.6(t, 1C, cyclohexyl);
2
2
2
2
2
39.6(d, 1C, CH); 42.9[t, 1C, H-C(CH O) ]; 48.2(d, 1C, neo-
16.9(t, 2C, cyclohexyl); 24.5(t, 2C, cyclohexyl); 30.3(d, 1C,
2
2
2
menthyl H-C-azulene); 70.9[t, 2C, 2(OCH Me)]; 104.9(d, 1C,
azulene CH-cyclohexyl); 94.9[t, 2C, 2(OCH Me)]; 106.0[d,
2
1C, (EtO) CH-azulene]; 111.7(d, 2C, azulene C1,3); 123.9(d,
2
dioxanyl H-C-azulene); 119.6(d, 2C, azulene C1,3); 121.2(d, 2C,
azulene C5,7); 133.8(d, 2C, azulene C4,8); 139.7(s, 2C, azulene
C3a,8a); 144.2(s, 1C, azulene C6); 158.5(s, 1C, azulene C2); and
trans-2-neomenthyl-6-(5-undecyl-1,3-dioxan-2-yl)azulene, as
blue microprisms, mp 53–43 °C, d (250 MHz, CDCl ) 1.30(m,
2C, azulene, C5,7); 130.3(d, 2C, azulene C4,8); 130.3(s, 2C,
azulene C3a,8a); 135.9(s, 1C, azulene C6); 151.4(s, 1C, azulene
C2); m/z (EI) 312 (M+, 100%).
H
3
cis- and trans-2-Cyclohexyl-6-(5-tridecyl-1,3-dioxan-2-yl)-
azulene, 1p
42H, neomenthyl and C
H
); 2.20(m, 1H, neomenthyl H-C-
11 23
azulene); 3.60(t, 2H, OCH ); 4.30(q, 2H, OCH ); 5.45(s, 1H,
2
2
dioxanyl H-C-azulene); 7.30(s, 2H, azulene H-C1,3); 7.35(d, 2H,
2-Cyclohexyl-6-(diethoxymethyl)azulene (0.28 g, 0.90 mmol)
azulene H-C5,7); 8.25(d, 2H, azulene H-C4,8); d (63 MHz,
and tridecylpropane-1,3-diol (0.3 g, 1.15 mmol) were dissolved
C
398
J. Mater. Chem., 1997, 7(3), 391–401

in dry benzene (20 ml) and heated at 80 °C with an ion
exchange resin (catalytic amount) for 3 h. Solvent was evapor-
ated under reduced pressure to leave a black product.
Purification was attempted by column chromatography on
neutral silica using light petroleum with 1% diethyl ether as
eluent to give the pure trans-2-cyclohexyl-6-(5-tridecyl-1,3-
dioxan-2-yl)azulene, as blue microprisms (Found: C, 82.73; H,
10.80; C H O calculated: C, 82.79; H, 10.52%); d (250 MHz,
to give colourless crystals of 4-(ethylenedioxy)cyclohexyl tosyl-
ate, 7.2 g, 73%, d (250 MHz, CDCl ) 1.75(m, 8H, cyclohexyl
H
3
CH s); 2.45(s, 3H, Me); 3.90(m, 4H, ketal CH s); 4.60(m, 1H,
2
2
HCOTs); 7.30(d, 2H, phenyl); 7.80(d, 2H, phenyl): m/z (EI)
211 (M+, 25%).
4-(Ethylenedioxy)cyclohexylcyclopentadiene
33 50
2
H
This was prepared by following the literature procedure for
the synthesis of (+)-neomenthylcyclopentadiene by Cesarotti
and Kagan,19 but full experimental details are given below.
Freshly distilled cyclopentadiene (12 ml, 0.177 ) was added
dropwise to sodium hydride (3.4 g, 0.142 ) in THF (25 ml) at
0°C to give a pink solution. When the reaction had completed
this was syringed into a solution of 4-(ethylenedioxy)cyclohexyl
tosylate (11 g, 35.5 mmol) in THF (50 ml) and heated at reflux
for 16 h to leave dark red colour. Water was then added, the
now dark brown solution filtered through a Bu¨chner funnel
and solvent evaporated from the filtrate under reduced pressure
to leave a brown oil. Purification by vacuum distillation
(0.5 mmHg, 140 °C) gave 4-(ethylenedioxy)cyclohexylcyclopen-
tadiene as a yellow oil, 2.5 g, 34%, d (250 MHz, CDCl )
CD Cl ) 0.80(t, 3H, J 7, Me); 1.1(m, 2H, cyclohexyl CH );
2
2
2
1.20(m, 22H, C H C H ); 1.45(m, 6H, cyclohexyl); 1.70(m,
11 22 2
5
4H, cyclohexyl); 2.05(m, 1H, HC-C H ); 2.85(m, 1H, azulene
13 27
CH-cyclohexyl); 3.46(t, 2H, J 11 Hz, OCH ); 4.16(q, 2H, J 5,
2
OCH ); 5.70(s, 1H, dioxanyl HC-azulene); 7.14(s, 2H, azulene
2
H-C1,3); 7.21(d, 2H, J 10.5, azulene H-C5,7); 8.13(d, 2H, J
10.5 Hz), azulene H-C4,8); d (63 MHz, CD Cl ) 14.3(q, 1C,
C
2 2
Me), 23.1(t, 1C, CH ); 26.7(t, 1C, cyclohexyl); 27.1(t, 2C,
2
cyclohexyl); 28.5(t, 1C, CH ); 29.7(t, 1C, CH ); 29.9[t, 8C,
2
2
8(CH )]; 30.1(t, 1C, CH ); 32.3(t, 2C, cyclohexyl); 34.6(d, 1C,
2
2
HC-C H ); 40.5(d, 1C, azulene CH-cyclohexyl); 73.2[t, 2C,
13 27
2(OCH )]; 104.7(d, 1C, dioxanyl HC-azulene); 116.2(d, 2C,
2
azulene C1,3); 121.7(d, 2C, azulene C5,7); 134.1(d, 2C, azulene
C4,8); 140.6(s, 2C, azulene C3a,8a); 144.7(s, 1C, azulene C6);
161.9(s, 1C, azulene C2); m/z (EI) 478 (M+, 100%). MPLC on
silica gave the pure cis-2-cyclohexyl-6-(5-tridecyl-1,3-dioxan-2-
yl)azulene, as purple microprisms, mp 86–87 °C (M+, calcu-
lated: 479.3882, C H O found: 479.3889); d (250 MHz,
H
3
1.75(m, 8H, cyclohexyl CH s); 2.30[m, 1H, cyclopentadienyl-
2
CH(cyclohexyl)]; 2.95(m, 2H, cyclopentadiene; 3.95(m, 4H,
ketal CH s); 6.00–6.50(m, 3H, cyclopentadiene).
2
33 50
2
H
1-[4-(Ethylenedioxy)cyclohexyl]-6-(diethoxymethyl)azulene
and 2-[4-(ethylenedioxy)cyclohexyl]-6-(diethoxymethyl)azulene
CD Cl ) 0.86(t, 3H, J 7, Me); 1.1(m, 2H, cyclohexyl CH );
2
2
2
1.30(m, 22H, C H C H ); 1.50(m, 6H, cyclohexyl); 1.80(m,
11 22 2
5
4H, cyclohexyl); 2.08(m, 1H, HC-C H ); 2.92(m, 1H, azulene
4-(Ethylenedioxy)cyclohexylcyclopentadiene, (1.5 g, 7.28 mmol)
was added to sodium hydride (0.2 g, 8.00 mmol) in THF
(30 ml) and heated gently until the reaction had completed to
give a red solution. A solution of N-butyl-4-(diethoxymethyl)-
pyridinium bromide (5.0 g, 15.0 mmol) in THF (25 ml) was
then added leaving a colourless solution which was heated at
reflux for 48 h; the reaction turning red and then dark brown.
Solvent was evaporated under reduced pressure and neutral
silica added to the dark brown oil. Purification by column
chromatography on neutral silica using light petroleum–
diethyl ether, 352, as eluent gave N-butyl-(4-ethoxycarbonyl-
4-ethyl)dihydropyridine as a colourless oil and a mixture of
the isomers as a dark blue oil. Separation of the isomers was
attempted by HPLC and reverse phase HPLC but led to
decomposition and a small amount of pure 1-[4-(ethylene-
dioxy)cyclohexyl]-6-(diethoxymethyl)azulene as a blue oil,
(M+ Found: 370.2130, C H O calculated: 370.2144); d
13 27
CH-cyclohexyl); 4.09[m, 4H, 2(OCH )]; 5.40(s, 1H, dioxanyl
2
HC-azulene); 7.20(s, 2H, azulene H-C1,3); 7.30(d, 2H, J 10.5,
azulene H-C5,7); 8.20(d, 2H, J 10.5), azulene H-C4,8); d
C
(63 MHz, CD Cl ) 14.3(q, 1C, Me), 23.1(t, 1C, CH ); 26.7(t,
2
2
2
1C, cyclohexyl); 27.1(t, 2C, cyclohexyl); 28.5(t, 1C, CH );
2
29.7(t, 1C, CH ); 29.8[t, 7C, 7(CH )]; 30.0(t, 1C, CH ); 30.2(t,
2
2
2
1C, CH ); 32.3(t, 2C, cyclohexyl); 34.6(d, 1C, HC-C H );
2
13 27
40.4(d, 1C, azulene CH-cyclohexyl); 71.3[t, 2C, 2(OCH )];
2
105.2(d, 1C, dioxanyl HC-azulene); 116.1(d, 2C, azulene C1,3);
121.7(d, 2C, azulene C5,7); 134.1(d, 2C, azulene C4,8); 140.6(s,
2C, azulene C3a,8a); 144.7(s, 1C, azulene C6); 161.9(s, 1C,
azulene C2); m/z (EI) 479 (M+, 100%).
4-(Ethylenedioxy)cyclohexanol
4-(Ethylenedioxy)cyclohexanone (5.0 g, 32 mmol, 1 equiv.) in
dry THF (25 ml) was added dropwise to LiAlH (3.0 g,
23 30
4
H
4
(250 MHz, CD Cl ) 1.2 [t, 6H, J 7, 2(CH )]; 1.85(m, 8H,
79 mmol, 2.2 equiv.) in dry THF (20 ml). When the reaction
2
2
3
cyclohexyl); 3.23(m, 1H, azulene HC-cyclohexyl); 3.60[m, 4H,
2(OCH CH )]; 3.95(s, 4H, O-CH -CH -O); 5.4 [s, 1H, (EtO) -
had ceased, the mixture was heated at reflux for a further 3 h
and allowed to cool. Excess LiAlH was destroyed by the
2
3
2
2
2
4
HC-azulene]; 7.25(m, 3H, azulene H-C3,5,7); 7.81(d, 1H, J 4,
azulene H-C2); 8.24(d, 1H, J 10, azulene H-C4); 8.33(d, 1H, J
careful addition of wet diethyl ether and then water. The white
suspension was then filtered through Celite which was washed
with copious amounts of diethyl ether. The organic portions
were combined, dried and solvent was evaporated under
reduced pressure to leave crude 4-(ethylenedioxy)cyclohexanol
as a yellow oil, 5 g, 99%, d (250 MHz, CDCl ) 1.75(m, 8H
10, azulene H-C8);
d
(63 MHz, CD Cl ) 15.3[q, 2C,
C
2 2
2(OCH Me)]; 32.5(t, 2C, cyclohexyl); 35.6(d, 1C, azulene CH-
2
cyclohexyl); 62.3[t, 2C, 2(OCH Me)]; 64.6(t, 1C, OCH CH -
2
2
2
O); 64.6(t, 1C, O-CH -CH -O); 104.9[d, 1C, (EtO) CH-azu-
2
2
2
H
3
lene]; 108.8(s, 1C, cyclohexyl-C-ketal); 117.2(d, 1C, azulene
C3); 120.2(d, 1C, azulene C5); 120.9(d, 1C, azulene C7); 132.5(d,
1C, azulene C2); 134.7(s, 1C, azulene C1); 135.0(d, 1C, azulene
C4); 135.9(d, 1C, azulene C8); 136.1(s, 1C, azulene C3a); 140.5(s,
1C, azulene C8a); 147.9(s, 1C, azulene C6); m/z (EI) 270 (M+,
50%); and 2-[4-(ethylenedioxy)cyclohexyl]-6-(diethoxymethyl)-
azulene as blue microprisms, mp 53–54 °C (M+ Found:
cyclohexyl CH s); 3.80(m, 1H, HCOH); 4.00(s, 4H, ketal CH s).
2
2
4-(Ethylenedioxy)cyclohexyl tosylate
This was prepared by following the procedure of Winstein
et al.12 but full experimental details are given below. 4-
(Ethylenedioxy)cyclohexanol, (5 g, 31.6 mmol, 1 equiv.) was
dissolved in dry pyridine and tosyl chloride (9.0 g, 47.2 mmol,
1.5 equiv.) added in small portions. The reaction mixture was
stirred vigorously for 30 min and then kept at 0 °C for 16 h.
The crystals which appeared were collected and extracted into
diethyl ether (50 ml). The ethereal portion was then washed
with 2  HCl (30 ml), water (100 ml) and 10% aqueous
potassium carbonate (20 ml). Solvent was evaporated under
reduced pressure to leave a viscous oil. This was left at 0 °C
with seeding until crystals had formed, which were collected
370.2151, C H O calculated: 370.2144);
d
(250 MHz,
H
23 30
4
CD Cl ) 1.20[t, 6H, 2(OCH Me)]; 1.80(m, 8H, cyclohexyl);
2
2
2
2.95(m, 1H, azulene CH-cyclohexyl); 3.58[m, 4H,
2(OCH Me)]; 3.93(s, 4H, O-CH -CH -O); 5.42 [s, 1H,
2
2
2
(EtO) CH-azulene]; 7.22(s, 2H, azulene H-C1,3); 7.32(d, 2H, J
2
10.5, azulene H-C5,7); 8.20(d, 2H, J 10, azulene H-C4,8); d
C
(63 MHz, CD Cl ) 15.4[q, 2C, 2(OCH Me)]; 31.8(t, 2C, cyclo-
2
2
2
hexyl); 35.3(t, 2C, cylcohexyl); 39.1(d, 1C, azulene CH-cyclo-
hexyl); 62.3[t, 2C, 2(OCH Me)]; 64.6(t, 1C, O-CH -CH -O);
2
2
2
J. Mater. Chem., 1997, 7(3), 391–401
399

64.7(t, 1C, O-CH -CH -O); 105.0[d, 1C, (EtO) CH-azulene];
Palladium on charcoal (75 mg) was then added and the vessel
kept under an atmosphere of hydrogen. The mixture was left
stirring at 20 °C until 1 equiv. of hydrogen had been taken up.
The now colourless solution was filtered through Celite to
remove the catalyst and washed with copious amounts of
water. The filtrate was extracted with dichloromethane
(3×60 ml) and the combined organic extracts washed with
aq. K CO (20%) and water. The organic layer was then
2
2
2
108.9(s, 1C, cyclohexyl-C-ketal); 116.2(d, 2C, azulene C1,3);
122.0(d, 2C, azulene C5,7); 134.2(d, 2C, azulene C4,8); 140.5(s,
2C, azulene C3a,8a); 146.3(s, 1C, azulene C6); 160.0(s, 1C,
azulene C2); m/z (EI) 370 (M+, 100%).
Azulene-6-carbaldehyde
2
3
Compound 1a (0.5 g, 2.17 mmol) was dissolved in dichloro-
methane (100 ml) and 2  hydrochloric acid (50 ml) added.
The mixture was stirred and the reaction monitored by TLC.
When all the 6-(diethoxymethyl)azulene had disappeared as
judged by TLC, the mixture was separated and the organic
layer dried and the solvent evaporated under reduced pressure.
Recrystallisation from light petroleum gave azulene-6-carbal-
dehyde as green–turquoise crystals, 0.27 g, 80%, mp 44–45 °C
(M+ Found: 156.0579, C H O calculated: 156.0575); d
dried and solvent evaporated under reduced pressure to
give a slightly yellow oil which crystallised on standing.
Recrystallisation from acetone yielded 4-(4-decyloxyphenethyl)-
pyridine, as colourless crystals, 1.42 g, 94%, mp 44–45 °C; d
H
(250 MHz, CDCl ) 0.90(t, 3H, Me); 1.30 [m, 14H,
3
CH ) (CH ) Me]; 1.75 [m, 2H, CH CH (CH ) Me]; 2.90(m,
2 2
2 7
2
2
2 7
4H, CH CH ); 3.90[t, 2H, CH (CH ) Me]; 6.75(d, 2H,
2
2
2
2 8
phenyl); 7.05(d, 2H, phenyl); 7.10(d, 2H, pyridine); 8.45(d, 2H,
pyridine); d (63 MHz, CDCl ) 14.1 (q, 1C, Me); 22.7(t, 1C,
11
8
2
H
C
3
(250 MHz, CDCl ) 7.50(d, 2H, J 3.5, azulene H-C1,3); 7.70(d,
CH ); 26.1(t, 1C, CH ); 29.3[t, 2C, (CH ) ]; 29.4(t, 2C, 2CH );
3
2
2
2 2
2
2H, J 10, azulene H-C5,7); 8.10(t, 1H, J 3.5, azulene H-C2);
29.6(t, 1C, CH ); 31.9(t, 1C, CH ); 35.7(t, 1C, phenyl-CH -
2
2
2
8.50(d, 2H J 10, azulene H-C4,8); 10.1 (s, 1H, CHO); d
CH ); 37.3(t, 1C, CH -CH -pyridine), 68.0(t, 1C, OCH );
C
(63 MHz, CDCl ) 119.8 (d, 2C, azulene C1,3); 123.7(d, 2C,
3
2
2
2
2
114.5(d, 2C, phenyl); 124.0(d, 2C, pyridine); 129.3(d, 2C,
phenyl); 132.5(s, 1C, phenyl); 149.5(d, 2C, pyridine); 150.8(s,
1C, phenyl); 157.6(s, 1C, pyridine); m/z (EI) 339 (M+, 15%).
azulene C5,7); 135.2 (d, 2C, azulene C4,8); 137.1(s, 1C, azulene
C2); 140.3(s, 2C, azulene C3a,8a); 141.7(s, 1C, azulene C6);
194.6(d, 1C, CHO); m/z (EI) 156 (M+, 100%).
N-Butyl-4-(4-decyloxyphenethyl)pyridinium bromide
6-(4-Hexyloxyphenethyl )azulene, 2a
4-(4-Decyloxyphenethyl)pyridine (2.7 g, 7.96 mmol) was dis-
solved in absolute ethanol (30 ml) and 1-bromobutane (4 g,
29.1 mmol, excess) added. The mixture was heated at reflux
for 50 h and allowed to cool at which pale yellow crystals
appeared in the yellow solution. Excess 1-bromobutane
and ethanol were evaporated under reduced pressure and
drying under high vacuum then gave crude yellow crystals,
found by 1H NMR spectroscopy to be mainly N-butyl-4-(4-
Diethyl 4-(hexyloxybenzyl)phosphonate (1.00 g, 2.96 mmol)
was dissolved in diethyl ether (30 ml) and potassium tert-
butoxide added (0.33 g, 2.96 mmol) to give a yellow precipitate.
When this had dissolved azulene-6-carbaldehyde was added.
The reaction was then kept stirring at 20 °C in the dark and
followed by TLC. After 30 min the aldehyde spot seemed
to have disappeared and an upper green spot appeared.
Purification was attempted by column chromatography on
silica using hexane–CH Cl , 352, as eluent in the dark to give
decyloxyphenethyl)pyridinium bromide, 2.26 g, 60%;
d
H
(250 MHz, CDCl ) 0.80(t, 3H, Me); 0.95(t, 3H, Me); 1.25(m,
2
2
3
a green crystalline product of 6-(4-hexyloxystyryl)azulene,
16H, OC H C H Me, NC H CH Me); 1.75(m, 2H,
2
4 7 14
2
4
2
which rapidly decomposed on standing, mp 225 °C (decomp.),
OCH CH C H ); 2.00(m, 2H, NCH CH C H ); 2.95(t, 2H,
2
2 8 17
2
2 2 4
d
(250 MHz, CDCl ) 0.90 (t, 3H, J 7, Me); 1.40[m, 6H,
phenyl-CH -CH -pyridine); 3.2(t, 2H, phenyl-CH -CH -pyri-
H
3
2
2
2
2
CH (CH ) Me]; 1.80(m, 2H, CH CH C H ); 3.99(t, 2H, J 7,
dine); 3.90(t, 2H, OCH C H ); 4.90(t, 2H, NCH C H );
2
2 3
2
2 4 9
2 9 19
2 3 7
CH C H ); 6.92(d, 2H, J 9, phenyl); 7.18(s, 2H, -CHNCH-);
6.75(d, 2H, phenyl); 7.00(d, 2H, phenyl); 7.80(d, 2H, pyridine);
2 5 11
7.32(d, 2H, J 4, azulene H-C1,3); 7.4(d, 2H, J 11, azulene H-
9.20(d, 2H, pyridine); m/z (EI) C H ON 396 (M+−Br, 50%).
27 42
C5,7); 7.5(d, 2H, J 9, phenyl); 7.8(t, 1H, J 4, azulene H-C2);
8.30(d, 2H, J 11, azulene H-C4,8); m/z (EI) 330 (M+, 100%).
This green product was then taken up into dry THF (30 ml)
and lithium aluminium hydride added carefully (0.2 g,
4.93 mmol); the mixture was heated at reflux for 3 h, then
stirred for 16 h at 20 °C. An upper purple spot was observed
on TLC. The solvent was evaporated under reduced pressure
and then purification was attempted by column chromatogra-
phy on silica, using CH Cl –hexane, 253, as eluent, to give 6-
A less soluble product was isolated after extraction of the
crude yellow crystals with dry acetone, which gave cream
crystals, and these were determined to be pure 4-(4-decyloxy-
phenethyl)pyridinium bromide (Found: C, 65.71; H, 7.99; N,
3.43; Br, 18.89: C H NOBr calculated: C, 65.71; H, 8.15; N,
23 34
3.33; Br, 19.01); d (250 MHz, CDCl ) 0.80(t, 3H, Me); 1.25
H
3
(m, 14H, OC H C H Me); 1.70(m, 2H, OCH CH C H );
2
4 7 14
2
2 8 17
2.90(t, 2H, phenyl-CH -CH -pyridine); 3.15(t, 2H, phenyl-
2
2
CH -CH -pyridine); 3.85(t, 2H, OCH C H ); 6.75(d, 2H,
2
2
2
2
2 9 19
(4-hexyloxyphenethyl)azulene as purple microprisms, which
phenyl); 6.90(d, 2H, phenyl); 7.65(d, 2H, pyridine); 8.70(d, 2H,
were then recrystallised from hexane, 0.10 g, 15%, mp 105 °C;
pyridine); d (63 MHz, CDCl ) 14.1(q, 1C, Me); 22.7(t, 1C,
C
3
d
(250 MHz, CDCl ) 0.9(t, 3H, J 7, Me); 1.3[m, 6H,
CH ); 26.0(t, 1C, CH ); 29.3(t, 1C, CH ); 29.4(t, 2C, 2CH );
H
3
2
2
2
2
(CH ) (CH ) Me]; 1.80(m, 2H, CH CH C H ); 3.0(m, 4H,
29.5(t, 2C, 2CH ); 31.9(t, 1C, CH ); 35.0(t, 1C, phenyl-CH -
2 2
2
2 3
2
2 4 9
2
2
2
CH CH ); 3.90(t, 2H, J 7, CH C H ); 6.7(d, 2H, J 9, phenyl);
CH ); 38.3(t, 1C, CH -CH -pyridine); 68.1(t, 1C, OCH );
2
2 5 11
2
2
2
2
7.05(d, 2H, J 11, azulene H-C5,7); 7.05(d, 2H, J 9, phenyl);
7.30(d, 2H, J 4, azulene H-C1,3); 7.80(t, 1H, J 4, azulene H-
C2); 8.20(d, 2H, J 11, azulene H-C4,8); d (63 MHz, CDCl );
114.8(d, 2C, phenyl CH); 127.2(d, 2C, pyridine); 129.3(d, 2C,
phenyl); 130.0(s, 1C, phenyl); 140.0(d, 2C, pyridine); 158.1(s,
1C, phenyl ); 163.3(s, 1C, pyridine); m/z (EI) C H ON 340
C
3
23 34
14.0 (q, 1C, Me); 22.6(t, 1C, CH ); 25.7(t, 1C, CH ); 29.3(t,
(M+−Br, 100%).
2
2
1C, CH ); 31.6(t, 1C, CH ); 38.0(t, 1C, CH ); 44.6(t, 1C, CH );
2
2
2
2
68.1(t, 2C, CH CH ); 114.5(d, 2C, phenyl); 117.9(d, 2C, azulene
6-(4-Decyloxyphenethyl)azulene, 2b
2
2
C1,3); 124.1(d, 2C, phenyl); 129.4(d, 2C, azulene C5,7); 133.0(s,
1C, phenyl); 135.8(d, 1C, azulene C2); 135.9(d, 2C, azulene
C4,8); 138.9(s, 2C, azulene C3a,8a); 152.5(s, 1C, phenyl); 157.6(s,
1C, azulene C6); m/z (EI) 332 (M+, 15%).
Freshly distilled cyclopentadiene (2.00 g, 30.3 mmol) was added
dropwise over 30 min to sodium hydride (0.75 g, 24.6 mmol)
in THF (70 ml) at 0°C and the mixture was then allowed to
warm to 20 °C. N-Butyl-4-(4-decyloxyphenethyl)pyridinium
bromide (5.36 g, 11.3 mmol) dissolved in dry THF (10 ml) was
then added to the pink solution which turned red, then green,
then blue, and finally brown. The mixture was heated at reflux
for 90 h, a blue spot being indicated by TLC. THF was
4-(4-Decyloxyphenethyl )pyridine
trans-4-Decyloxy-4∞-stilbazole19 (1.5 g, 4.45 mmol) was dis-
solved in glacial acetic acid (100 ml) to give a yellow solution.
400
J. Mater. Chem., 1997, 7(3), 391–401

evaporated under reduced pressure to leave a brown oil. Silica
was added to the brown oil and purification by column
chromatography using light petroleum (bp 40–60 °C) as eluent,
gave a blue product. Recrystallisation from diethyl ether–
methanol gave 6-(4-decyloxyphenethyl)azulene as blue crys-
References
1
2
3
4
M. R. Churchill, in Progress in Inorganic Chemistry, ed.
S. J. Lippard, vol. 11, pp. 58–59.
E. W. Thulstrup, P. L. Case and J. Michl, Chem. Phys., 1974, 6, 410.
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tals, 0.64 g, 15%, mp 100 °C, (Found: C, 86.55, H, 9.38; C H O
28 36
calculated: C, 86.55; H, 9.33%); d (250 MHz, CD Cl ) 0.9(t,
H
2
2
5
R. Brettle, D. A. Dunmur, S. E. Estdale and C. M. Marson,
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3H, J 7, Me); 1.3[m, 14H, (CH ) (CH ) Me]; 1.80(m, 2H,
2 2
2
2 7
CH CH C H ); 3.0(m, 4H, CH CH ); 3.90(t, 2H, J 7,
6
7
8
9
T. Morita, K. Takase and M. Kaneko, Jpn. Pat. 0269439, 1990.
T. Morita, K. Takase and M. Kaneko, Jpn. Pat. 0269436, 1990.
T. Morita, K. Takase and M. Kaneko, Jpn. Pat. 0269438, 1990.
T. Morita, K. Takase and M. Kaneko, Jpn. Pat. 0269437, 1990.
2
2 8 17
2
CH C H ); 6.75(d, 2H, J 9, phenyl); 7.05(d, 2H, J 11, azulene
2 9 19
H-C5,7); 7.05(d, 2H, J 9, phenyl); 7.30(d, 2H, J 4, azulene H-
C1,3); 7.80(t, 1H, J 4, azulene H-C2); 8.25(d, 2H, J 11, azulene
H-C4,8); d (63 MHz, CD Cl ); 14.3 (q, 1C, Me); 23.1(t, 1C,
10 T. Morita, K. Takase and M. Kaneko, Jpn. Pat. 0269441, 1990.
11 K. Hafner, Angew. Chem., 1957, 69, 393.
C
2 2
CH ); 26.5(t, 1C, CH ); 29.8(t, 1C, CH ); 30.0[t, 2C, (CH ) ];
12 E. Bernaert, M. Anteumis and D. Tavernier, Bull. Soc. Chim. Belg.,
1974, 83, 357.
2
2
2
2 2
32.3(t, 1C, CH ); 38.3(t, 1C, CH ); 44.9(t, 1C, CH ); 68.5(t,
2
2
2
2C, CH CH ); 114.8(d, 2C, phenyl); 118.2(d, 2C, azulene C1,3);
13 T. Koenig, K. Rudolf, R. Chadwick, H. Geiselmann, T. Patapoff
and C. E. Klopfenstein, J. Am. Chem. Soc., 1986, 108, 5024.
14 R. Luhowy and P. M. Keehn, J. Am. Chem. Soc., 1977, 99, 3797.
15 K. J. Toyne, T hermotropic liquid crystals, ed. G. W. Gray, Wiley,
Chichester, 1987, p. 41.
2
2
124.5(d, 2C, phenyl); 129.8(d, 2C, azulene C5,7); 133.5(s, 1C,
phenyl); 136.1(d, 1C, azulene C2); 136.3(d, 2C, azulene C4,8);
139.3(s, 2C, azulene C3a,8a); 153.1(s, 1C, phenyl); 158.1(s, 1C,
azulene C6); m/z (EI) 388 (M+, 20%).
16 E. M. Averyanov, V. M. Muratov and V. G. Rumyantsev, Sov.
Phys., 1985, 61, 476.
17 F. Popp and W. McEwen, J. Am. Chem. Soc., 1958, 80, 1181.
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P. Styring, L iq. Cryst., 1988, 3, 385.
We are grateful to Hitachi Limited for financial support, and
to Dr K. Toriyama for discussion. The assistance of Dr G.
Ungar in making X-ray measurements is also gratefully
acknowledged.
Paper 6/06139G; Received 6th September, 1996
J. Mater. Chem., 1997, 7(3), 391–401
401