1276
H. Hopf et al.
LETTER
Table 2 Selected Physical Properties of Analogous LC Perhydor-
azulene, Cyclohexyl, and Biscyclohexyl Derivatives
Further studies on anisotropic molecular parameters and
structure–property correlations in the case of mesomor-
phic 2,6-disubstituted perhydroazulenes as well as a short-
er synthetic route to the crucial intermediate 9 are under
way.
OEt
OEt
F
OEt
F
F
F
F
F
Acknowledgment
Structure
We thank the Alexander von Humboldt Stiftung and the Fonds der
Chemischen Industrie for support of this work and Prof. Dr. S.
Laschat (University of Stuttgart) for DSC and POM measurements
of our mesogenic materials and Prof. H. Finkelmann (University of
Freiburg) for DSC measurements and phase assignments. Analyti-
cally pure compounds were isolated by Fischer Analytics (Bingen)
using various HPLC techniques.
C3H7
C3H7
C3H7
Mesorange
(°C)
Cr = 71,
N = 114, I
Cr = 60, I
Cr = 79, SmB (78),
N = 178
References and Notes
Dea
–6.6
–6.6
0.0760
78
–6.4
(1) Hussain, Z.; Hopf, H.; Pohl, L.; Oeser, Th.; Fischer, A. K.;
Jones, P. G. Eur J. Org. Chem. 2006, 5555.
(2) Krause, G. A.; Landgrebe, K. Synthesis 1984, 885.
(3) Nagai, M.; Lazor, J.; Wilcox, C. S. J. Org. Chem. 1990, 55,
3440.
Dnb
0.0968
293
0.1108
413
g1 [mPas]c
a De = dielectric anisotropy as defined in the text.
(4) Weinhardt, K. K. Tetrahedron Lett. 1984, 25, 1761.
(5) Perhydroazulene-2,6-dione Ethylene Ketal 9
1H NMR (400.14 MHz, CDCl3): d = 3.86 (s, 4 H), 2.30–2.48
(m, 4 H), 1.92–2.04 (m, 2 H), 1.77–1.88 (m, 2 H), 1.51–1.69
(m, 6 H) ppm. 13C NMR (100.62 MHz, CDCl3): d = 219.2,
111.5, 64.3 (+), 64.2 (+), 45.5 (+), 39.0 (–), 36.6 (+), 25.8 (+)
ppm. MS (IE): m/z (%) = 210 (9) [M+], 126 (5), 99 (100), 86
(10), 55 (8); IR (diamond ATR): n = 2990, 2931, 2880, 1731
cm–1. UV (MeCN): lmax = 284 nm.
b Dn = optical anisotropy or birefringence as defined in the text.
c g1 = rotational viscosity, an anisotropic viscosity parameter.
hexyl derivatives as well as three-ring derivatives with
two cyclohexyl rings but with improved nematogenic be-
havior. Because of this combination of properties in only
one molecular entity the new mesomorphic HAZ deriva-
tives represent a real extension of the classes of LC mate-
rials presently known. Dielectrically ‘neutral’ LC
molecules are generally substances with a relatively low
viscosity. Therefore they are used as additives in dielectri-
cally ‘positive’ as well as ‘negative’ multicomponent
nematic mixtures to shorten the response times of LCD. In
contrast to the enantiotropic purely nematic, low viscous,
and low-melting dielectrically ‘neutral’ perhydroazu-
lenes, the concentration of which is not restricted in a
nematic LC mixture, the corresponding low-viscous and
low-melting cyclohexyl derivatives used today, are often
isotropic or monotropic nematic. Thereby they decrease
the clearing point, that is, the upper temperature limit for
technical applications of a LC mixture. In order to com-
pensate for this effect, a high-clearing biscyclohexyl com-
ponent is required to achieve a sufficiently broad nematic
phase again. In contrast to their hydrazulene analogues
such biscyclohexyl derivatives generally possess an addi-
tional smectic phase. As a consequence they show limited
solubility in a nematic matrix and impair the electroopti-
cal properties, mainly the response times at lower temper-
atures. These negative properties restrict the role of both
in a mixture, requiring the addition of more singular com-
ponents. This is one of the reasons why ‘LC composi-
tions’ often consist of more than 15 substances to meet the
physical and electrooptical display specifications. By our
new class of thermally and light-stable, purely nematic,
and relatively low-viscous LC hydrazulenes it may be
possible to reduce this high compound complexity of ac-
tual LC mixtures for flat-screen information technology.
(6) White, R. D.; Wood, J. L. Org. Lett. 2001, 3, 1825.
(7) Liquid Crystalline Derivative 16
1H NMR (300.13 MHz, CDCl3): d = 6.86 (ddd, 1 H, J1 = 0.3
Hz, J2 = 2.4 Hz, J3 = 8.9 Hz), 6.47 (dd, 1 H, J1 = 2.0 Hz,
J2 = 7.6 Hz), 4.08 (q, 2 H, J = 7.0 Hz), 2.96–3.12 (m, 1 H),
2.19–2.38 (m, 2 H), 1.59–1.96 (m, 12 H), 1.43 (t, 3 H, J = 7.0
Hz), 1.23–1.38 (m, 4 H), 0.81–0.99 (m, 4 H) ppm. 13C NMR
(75.47 MHz, CDCl3): d = 149.1 (dd, J1 = 10.3 Hz, J2 = 245.0
Hz), 145.9 (dd, J1 = 3.0 Hz, J2 = 8.2 Hz), 141.5 (dd,
J1 = 15.3 Hz, J2 = 246.5 Hz), 129.1 (dd, J1 = 1.5 Hz,
J2 = 12.3 Hz), 120.9 (+, dd, J1 = 4.6 Hz, J2 = 6.0 Hz), 109.3
(+, d, J = 2.5 Hz), 65.4 (+), 40.8 (+), 39.8 (–), 39.5 (–), 37.9
(+), 37.5 (–), 31.8 (+), 29.2 (+), 21.9 (+), 14.8 (–), 14.4 (–)
ppm. MS (IE): m/z (%) = 337 (22) [M + H+], 336 (100) [M+],
198 (13), 197 (20), 184 (52), 171 (14), 169 (12), 156 (36),
143 (24), 83 (15). IR (diamond ATR): n = 2931, 2889, 2857,
1511, 1473, 1296, 1116, 1081, 805 cm–1. UV (CH2Cl2):
l
max = 229, 268 nm. For mp see Table 1.
(8) (a) Bahadur, B. Liquid Crystals Applications and Uses, Vol.
1; World Scientific: Singapore, 1990. (b) Becker, W. Liquid
Crystal Newsletter 2000, 15, 13. (c) Scheuble, B. S.;
Gehlhaar, T. Liquid Crystal Newsletter 2000, 15, 39.
(d) For an excellent recent review, see: Kirsch, P.; Bremer,
M. Angew. Chem. Int. Ed. 2000, 39, 4216; Angew. Chem.
2000, 112, 4384. (e) Heckmeier, M.; Dunmur, D.;
Stegemeyer, H. Crystals that Flow; Taylor and Francis:
London, 2004, Sect. D.
(9) (a) Pauluth, D.; Tarumi, K. J. Mater. Chem. 2004, 14, 1219.
(b) Iwata, Y.; Naito, H.; Inoue, M.; Ichinose, H.; Klasen-
Memmer, M.; Tarumi, K. Jpn. J. Appl. Phys. 2004, 43 (12B),
L1588.
(10) (a) Klasen, M.; Götz, A. Liquid Crystal Newsletter 1999, 14,
22. (b) Tarumi, K.; Heckmeier, M. Liquid Crystal
Newsletter 2000, 15, 30.
(11) Goulding, M.; Reiffenrath, V.; Hirschmann, H. Liquid
Crystal Newsletter 2001, 16, 33.
Synlett 2011, No. 9, 1273–1276 © Thieme Stuttgart · New York