Thermotropic liquid crystals from planar chiral compounds: [2.2]Paracyclophane as a mesogen core

Article abstract of DOI:10.1002/1522-2675(200202)85:2<431::AID-HLCA431>3.0.CO;2-H

New thermotropic mesomorphic compounds containing a [2.2]paracyclophane (PC) unit were synthesized and investigated (Scheme). Carboxylic acids were selected as the starting PC building blocks. The influence of structural features on the stability of the m

Full text of DOI:10.1002/1522-2675(200202)85:2<431::AID-HLCA431>3.0.CO;2-H

Helvetica Chimica Acta Vol. 85 (2002)
431
Thermotropic Liquid Crystals from Planar Chiral Compounds:
[2.2]Paracyclophane as a Mesogen Core
by Valeria I. Rozenberg* and Elena L. Popova
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova 28,
117813 Moscow, Russia (e-mail: lera@ineos.ac.ru)
and Henning Hopf*
Department of Organic Chemistry, Technical University of Braunschweig, Hagenring 30,
D-38106 Braunschweig (e-mail: H.Hopf@tu-bs.de)
New thermotropic mesomorphic compounds containing a [2.2]paracyclophane (PC) unit were synthesized
and investigated (Scheme). Carboxylic acids were selected as the starting PC building blocks. The influence of
structural features on the stability of the mesomorphic phases was studied (Figs. 1 and 2): for this purpose, the
structures of the PC-carboxylate unit and the organic fragment of the aryl-ester moiety were varied
systematically. Esters derived from PC-monocarboxylic acid did not exhibit liquid-crystalline (LC) properties,
while diaryl PC-dicarboxylates favored mesomorphism. Dicarboxylate substituents arranged in the para-
position provided LC phases in a broad temperature range and considerably increased the mesomorphic
interval in comparison with that of the structurally related pseudo-para PC derivatives.
Introduction. Unique physical properties, providing wide application in electro-
optic devices and particularly the recent discovery of new mesophases, such as
antiferroelectric, ferrielectric, and twist-grain boundary phases, have put chiral liquid-
crystalline (LC) materials in the centre of liquid-crystal research [1][2]. Historically, up
to now, most chiral LC compounds contain molecules incorporating a centre of
chirality. More recently, compounds with planar and axial chirality are beginning to
attract the growing interest of researchers dealing with LC materials. The unique
geometry of this type of compounds provides a rigid interaction between the origin of
the symmetry-breaking chirality and the mesogenic unit, thus resulting in a definite
fixation of the source of chirality in a LC matrix.
In principle, planar chirality could drastically change the physical properties of the
resultant LC material: 1) In terms of molecular structure, a rigid steric coupling
between the transverse dipole, chiral centre, and the mesogen rod should maximize the
local ferroelectric polarization [3], allowing consideration of the above compounds as
possible chiral dopants for ferroelectric compositions, which are able to confer a high
value of spontaneous polarization (Ps) to the achiral host [4]. 2) Electro-optical effects
exhibited by LC materials such as electroclinic effects or nonlinear optical (NLO)
properties are expected to be larger for compounds with rigid interaction between the
chiral and optical portions of the molecule [5].
However, the bulkiness of the structural units necessary to realize an axis or a plane
of chirality significantly disturbs the desired rigid rod-like shape of the molecule, thus
creating a serious obstacle to achieving stable mesomorphic properties. So far, only a

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few examples of optically active compounds with planar or axial chirality exhibiting LC
behaviour have been reported. These include cyclohexylideneethanone derivatives [6],
compounds containing a chiral biphenyl core [7], allene derivatives [8], and liquid
crystals derived from butadiene(tricarbonyl)iron complexes [9]. Also the first 1,3-
unsymmetrically disubstituted optically active LC ferrocene derivative was recently
reported [10]1). In all the above cases, the investigated compounds had to be prepared
by multistage synthesis leading to low overall yields, or compounds were obtained
which are chemically or photochemically unstable. Moreover, only a narrow temper-
ature interval of smectic phases was observed in most cases2). This is probably the
reason for lack of systematic studies of physical properties of compounds with planar
and axial chirality as well as of their practical application. The ease of functionalization,
optical resolution (introduction of even one substituent into the aromatic ring or the
molecular bridges produces planar chirality of the PC molecule), and high stability of
[2.2]paracyclophane (ˆtricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene; PC) de-
rivatives towards light, oxidation, and high temperatures [12] make them unique
candidates in this study.
In the present study, we want to assess the mesogenic potential of the PC unit, as
well as to establish the characteristic features of PC-containing compounds concerning
mesomorphism. In particular, a search of the structural features that provide increased
stability of the mesomorphic behaviour of the PC derivatives was performed. Towards
this end, the structures of a) the PC unit and b) of the organic fragment (substituent)
were varied systematically.
Results and Discussion. Synthesis. Three starting building blocks are commonly
used to construct LC compounds: aldehydes, phenols, and carboxylic acids, and they
have often been employed to build-up imino and ester groups, respectively. Schiff bases
derived from aldehydes are less important for practical applications because of their
tendency to hydrolyze. The phenolic [2.2]paracyclophanol is quite unreactive;
however, with aromatic acid chlorides it reacts to give esters that have significantly
higher melting points than their benzene analogues (with benzene unit instead of PC).
On the other hand, PC-carboxylic acids provide esters that melt approximately at the
same temperatures as structurally related benzene derivatives, and they are readily
available. Therefore, carboxylic acids of PC were chosen as the most appropriate
building blocks to construct LC compounds.
The general approach used in the synthesis of the investigated PC derivatives was to
construct separately a phenolic part and to attach this subsequently as an ester moiety
to the PC-carboxylic acid structural block (Scheme). Standard esterification conditions
(pyridine) were used for the reaction of PC-carbonyl chlorides with aromatic phenols.
To study the influence of the structure of the aryl-ester moieties on mesogenic
1
)
Two examples of optically active ferrocene-containing LC compounds have been reported previously [11].
However, in these cases, chirality was introduced into the peripheral side chain by means of an asymmetric
C-atom.
Exceptions are allene derivatives for which smectic C phases were observed over a broad temperature
range [8]. However, these compounds possess moderate thermal stability only, which largely depends on
the substitution pattern at the allene moiety.
2
)

Helvetica Chimica Acta Vol. 85 (2002)
433
Scheme
behaviour, three types of phenols were tested to construct disubstituted PC derivatives
(Scheme).
Mesogenic Properties. a) Monosubstituted PC Derivatives Ia,b. The investigated
monosubstituted PC derivatives Ia and Ib reveal no mesomorphic behaviour. They melt
directly into an isotropic liquid; also, no LC phases were detected on cooling of the
samples from the isotropic melt compounds crystallized directly from the liquid

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Helvetica Chimica Acta Vol. 85 (2002)
phase. The lack of LC properties could be probably explained by the unfavourable
molecular shape (L-shape) and repulsive interactions introduced by the PC core.
b) Disubstituted Pseudo-para-PC Derivatives IIa k. In our search for mesogenic
structures derived from [2.2]paracyclophane, we next turned to disubstituted com-
pounds that could provide a more elongated molecular shape, compared to that of
monosubstituted derivatives, thus favoring mesomorphism. We furthermore consid-
ered it useful to compare the mesomorphic behaviour of PC derivatives with that of the
corresponding compounds containing a ferrocene unit, which can be viewed as the most
closely related analogue of PC, both systems possessing a double-layered structure.
Although we do not consider ferrocene derivatives to be promising candidates in
our study of LC compounds with planar chirality (rather complex resolution
techniques, relatively narrow interval of LC phases exhibited in most cases), the main
construction principles elaborated for ferrocenomesogens [13] appear to be useful for
the investigation of the LC behaviour of PC derivatives. However, the structure/
mesogenic property relationship determined for ferrocene-containing LC compounds
cannot be applied to PC derivatives automatically since the mesomorphic behaviour
could be significantly influenced by the structural peculiarities of each of these
molecules.
Historically, the ferrocene 1,1'-diesters bis(4'-alkoxy-[1,1'-biphenyl]-4-yl) ferro-
cene-1,1'-dicarboxylates were reported as the first mesogenic ferrocene derivatives
[14]. X-Ray diffraction studies indicated that these compounds adopt a −transoid×
conformation (−S× shape) in the crystalline and mesomorphic states [15], which
approximately corresponds to the pseudo-para substitution pattern in paracyclophanes.
The structurally related PC analogues IIa g were hence synthesized (Fig. 1).
Mesomorphic behaviour was investigated by means of differential scanning
calorimetry (DSC) and polarized microscopy (PM). Compounds were investigated
at various scanning rates (see Exper. Part), and coincident results were obtained in all
cases. Phase-transition temperatures of the investigated PC derivatives are presented in
Fig. 1. Only three ferrocene derivatives from the reported series [14] (n ˆ 4 11) show
mesomorphic behaviour (Fig. 1): the compounds with n ˆ 5 and 6 exhibit a monotropic
smectic C (SmC) phase in a narrow temperature interval, while the compound with n ˆ
11 gives rise to a monotropic smectic A (SmA) phase. In contrast, all structurally
related PC derivatives exhibit a stable enantiotropic nematic phase over a relatively
broad temperature range, which can be easily identified by the appearance of the
nematic droplets immediately below the clearing point that consolidate on cooling to
display the characteristic marbled texture. The temperature interval of the nematic
phase is nearly independent of the alkyl chain length. This observation is of interest
since usually the nematic stability decreases as the paraffinic chain becomes longer.
Long-chain derivatives with n > 6 also exhibit a short monotropic SmA phase. Within
the cooling temperature regimes (5 and 108/min) used, it separates in the form of grains,
and crystallization takes place parallel with its formation. However, when samples are
kept at temperatures 5 108 higher than Tcryst for 30 min, a typical focal conic texture
with homeotropic domains develops.
To further investigate the importance of structural features on the liquid-crystalline
behaviour, we examined the influence of the nature of the organic aryl-ester moiety on
the mesomorphic tendency. PC Derivatives IIh and IIi with the ester moieties R2 and IIj

Helvetica Chimica Acta Vol. 85 (2002)
435
Fig. 1. Phase-transition temperatures of PC derivatives IIa k, compared with those of structurally related
ferrocene analogues. The data for ferrocene derivatives are from [14][16] for the compounds containing the
corresponding ester moieties R1, R2 or R3. H ˆ Heating cycle, C ˆ cooling cycle. )*, no reported data.
crystal,
nematic phase,
smectic A phase,
smectic C phase.

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and IIk with R3 were synthesized for this purpose. The organic fragments R2 and R3
have similar chemical compositions but differ in orientation of the interior ester
linkages. Paracyclophanecarboxylates containing the ester moiety R2 exhibit an
enantiotropic nematic phase in a narrow temperature interval (structurally related
ferrocene analogous were nonmesogenic [16]). PC-Containing compounds containing
the ester moiety R3 exhibit a broad interval of SmA phase (ferrocene analogues also
exhibited a tendency to form smectic phases; however, these were detected only over a
narrow temperature interval [16]). Benzene derivatives containing substituents of type
R2 and R3 revealed the same mesogenic tendencies with respect to the mesophase type
[17][18] as those observed for the investigated cyclophane-containing compounds: as
suggested in [18] both structural (unfavourable −bent× shape of fragment R2) and
electronic factors can explain the different mesogenic tendency of the derivatives with
fragments R2 and R3.
c) Disubstituted para-PC Derivatives IIIa d. To study the influence of the
substituent position on the mesophase behaviour of paracyclophane derivatives,
compounds containing the same type of substituents (R1, R2 or R3) in para-position of
the cyclophane moiety were synthesized, and the mesomorphic behaviour was
compared with that of pseudo-para-PC analogues, as well as with the structurally
related ferrocenomesogenes [19][20].
As in the case of pseudo-para-substituted paracyclophane derivatives, compounds
with the ester moiety R3 reveal superior mesogenic properties in the investigated series
and a pronounced tendency to form smectic phases (Fig. 2).
Broad intervals of the SmA phase, exhibiting a typical focal-conic texture with
homeotropic domains under PM are observed for IIId. Compounds containing R1 show
a nematic phase, as well as SmA phase in the case of the long-chain derivative IIIb (n ˆ
14). PC Derivatives with the ester moiety of type R2 display only nematic behaviour.
Thus, the LC tendency of para-substituted PC derivatives depending on the nature of
the substituents remains unchanged, compared with the pseudo-para-substituted
structures.
However, in contrast to the structurally related pseudo-para analogues, para-
substituted PC derivatives exhibit a considerable lowering of the melting point and
increased mesomorphic ranges (this relates to all three types of ester moieties R1, R2
and R3). Thus, the para-disubstituted PC structure is a stronger mesomorphic promoter
than the one containing the substituents in pseudo-para position (for identical ester
moieties). Therefore, for the investigated paracyclophane-containing compounds,
mesomorphic strength follows the series: para- > pseudo-para- > mono-substitution.
The above tendencies are similar to the data obtained for the ferrocene framework
[13]. Thus, in spite of the fact that PC derivatives show superior mesogenic properties
compared to the ferrocene-containing compounds, the main principles elaborated for
the construction of LC double-layered molecules are comparable. It is hence likely that
rigid organic moieties exhibiting similar molecular shapes will behave analogously as
well.
Conclusions. The results presented demonstrate that, by careful combination of
structural factors, [2.2]paracyclophane derivatives that exhibit stable mesomorphic
behaviour over a wide temperature range can be produced, and different types of

Helvetica Chimica Acta Vol. 85 (2002)
437
Fig. 2. Phase-transition temperatures of PC derivatives IIIa d, compared with those of structurally related
ferrocene analogous. The data for ferrocene derivatives are from [19][20] for the compounds containing the
corresponding ester moieties R1 or R2. H ˆ heating cycle, C ˆ cooling cycle. )*, no reported data; )**, phase
transition resolved by polarized microscopy only. Identification of the mesophases, see Fig. 1.
mesophases can be generated. The mesomorphic properties depend on both the
structure of the initial cyclophane block and the nature of the organic substituents and
their position. Due to their unfavourable molecular shape, the investigated mono-
substituted paracyclophane derivatives do not reveal LC behaviour, while disubstitu-
tion favors mesomorphism. para-Substitution in the PC unit provides mesophases over
a broad temperature range and considerably increased mesomorphic intervals in
comparison with structurally related pseudo-para-PC derivatives. Thus, appropriately
substituted paracyclophanes can serve as a valuable framework for the design of novel
LC compounds with planar chirality.
This work was supported by the Fonds der Chemischen Industrie.

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Experimental Part
1. General. Pyridine was distilled over KOH prior to use. Other reagents were purchased from Aldrich and
were used without purification. All reactions were carried out under N2. Column chromatography (CC): silica
gel 60, 70 230 mesh (Merck, Darmstadt). Transition temp. (onset point of endotherm or exotherm) and
enthalpies were determined with a differential scanning calorimeter Rheometric Scientific DSC SP; all
compounds were studied at various scanning rates (5 and 108 minÀ1) under N2. Optical studies were conducted
by means of the Olympus BX-50 system microscope equipped with a Linkam LTS-350 variable-temp. stage. IR
Spectra: Nicolet 320-FT-IR spectrometer; in cmÀ1 1H- and 13C-NMR Spectra: Bruker DRX-400 (400.13 and
.
100.6 MHz, for 1H and 13C, resp.); CDCl3 as solvent; d in ppm rel. to SiMe4 as internal standard, J in Hz. MS:
Finnigan MAT8430 , EI (70 eV); in m/z (rel. %). Elemental analyses were performed in the Analytical
Laboratory of the Department of Pharmaceutical Chemistry, Technical University Braunschweig.
2. [2.2]Paracyclophanecarboxylic Acids. [2.2]Paracyclophane-4-carboxylic Acid ( ˆ Tricyclo[8.2.2.24,7]-
hexadeca-4,6,10,12,13,15-hexaene-5-carboxylic Acid) was synthesized according to [21].
[2.2]Paracyclophane-4,16-dicarboxylic Acid (ˆ Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-
dicarboxylic Acid) [22] was obtained from 4,16-dibromo[2.2]paracyclophane [23] by lithiation followed by
carboxylation under the same conditions as described for the preparation of [2.2]paracyclophane-pseudo-o-
dicarboxylic acid [24]. This provided [2.2]paracyclophane-4,16-dicarboxylic acid in 77% yield.
[2.2]Paracyclophane-4,7-dicarboxylic Acid ( ˆ Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,15-di-
carboxylic Acid). Dimethyl [2.2]paracyclophane-4,7-dicarboxylate [25] (3 g, 9.26 mmol) in MeOH/H2O 1 :1
(400 ml) was treated with an excess of K2CO3. The mixture was boiled overnight, concentrated to ca. 100 ml, and
acidified with conc. HCl soln. The precipitate was filtered off, thoroughly washed with H2O, and dried: 2.44 g
(89%). M.p. >2508 (dec.). IR (KBr): 2924s, 2894m, 2854m, 1686s, 1414s, 1282s. 1H-NMR ((D6)DMSO): 2.81
3.00 (m, 4 H, CH2CH2); 3.13 3.20 (m, 2 H, CH2CH2); 3.91 3.99 ( m, 2 H, CH2CH2); 6.45 6.55 (m, 4 arom. H);
‡
7.13 ( s, 2 arom. H); 12.89 (br. s, 2 COOH). MS: 296 (20, M ), 148 (4), 104 (100), 78 (16). Anal. calc. for
C18H16O4: C 72.96, H 5.44; found: C 72.90, H 5.61.
3. Phenolic Biphenyl and Benzene Derivatives. 4'-(Alkyloxy)-[1,1'-biphenyl]-4-ols (R1OH). The mixture of
equimolar amounts of [1,1'-biphenyl]-4,4'-diol and alkyl bromide, excess of K2CO3, and a catalytic amount of
NaI were stirred in 1-methylpyrrolidin-2-one (NMP) overnight at 708. The mixture was poured into H2O and the
precipitate filtered off, thoroughly washed with H2O, and dried. CC (silica gel, CH2Cl2) gave the desired
phenolic derivatives in 65 75% yield.
4-Hydroxyphenyl 4-(Alkyloxy)benzoates (R2OH). The 4-(alkyloxy)benzoic acids [26] were converted to
the corresponding acid chlorides with SOCl2. These were reacted with hydroquinone in pyridine [27]. The final
phenolic derivatives were purified by CC (silica gel, CH2Cl2).
4'-(Alkyloxy)-[1,1'-biphenyl]-4-yl 4-Hydroxybenzoate (ROH) or 4-(Alkyloxy)phenyl 4-Hydroxybenzoate
(R3OH). The 4-hydroxybenzoic acid (its OH function protected as the methyl carbonate [27]) was converted to
the corresponding acid chloride with oxalyl chloride. The acid chloride was treated with 4'-(alkyloxy)-[1,1'-
biphenyl]-4-ol (or 4-(alkyloxy)phenol for the preparation of disubstituted PC derivatives) in pyridine as
described in [27]. Subsequent removal of the protecting group was accomplished by stirring with aq. ammonia in
EtOH [28] to give the desired phenolic derivatives, which were recrystallized from EtOH.
4. PC Esters Ia,b, IIa k, and IIIa d: General Procedure. The PC-dicarboxylic acid (0.4 mmol) (or the PC-
monocarboxylic acid for the preparation of mono-substituted Ia,b) was converted with SOCl2 (3 ml) to the
corresponding acid chloride by boiling in CHCl3 (15 ml) for 4 h. After evaporation, the residue was dried under
reduced pressure. The acid chloride and the aromatic phenolic derivative (0.75 mmol) in pyridine were boiled
for 6 h under N2. Then the mixture was cooled and poured into dil. HCl soln. The precipitate was filtered off,
thoroughly washed with H2O, and dried. The product was dissolved in CH2Cl2 and the soln. was passed through a
short silica gel plug. The solvent was evaporated and the residue recrystallized from MeOH/CH2Cl2 2 :1 .
4-{{[4'-(Octyloxy)[1,1'-biphenyl]-4-yl]oxy}carbonyl}phenyl [2.2]Paracyclophane-4-carboxylate (ˆ4-{{[4'-
Octyloxy)[1,1'-biphenyl]-4-yl]oxy}carbonyl}phenyl Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5-car-
boxylate; Ia): Yield 0.21 g (81%). M.p. 160 1628. 1H-NMR (CDCl3): 0.90 (t, Me); 1.24 1.54 (m, 1 0 H,
5 CH2); 1.76 1.85 (m, 2 H, CH2); 2.89 2.94 (m, 1H, C H2CH2 (PC)); 3.03 3.29 (m, 6 H, CH2CH2 (PC)); 4.01
(t, CH2O); 4.14 4.21 (m, 1H, C H2CH2 (PC)); 6.51 6.66 ( m, 5 arom. H (PC)); 6.78 (dd, 3J ˆ 7.8, 4J ˆ 1.9,
1arom. H (PC)); 6.99 ( d, J ˆ 8.7, 2 arom. H); 7.28 (d, J ˆ 8.7, 2 arom. H); 7.38 (d, 4J ˆ 1.9, 1 arom. H (PC)); 7.42
(d, J ˆ 8.7, 2 arom. H); 7.52 (d, J ˆ 8.7, 2 arom. H); 7.61( d, J ˆ 8.7, 2 arom. H); 8.35 (d, J ˆ 8.7, 2 arom. H).
‡
MS: 652 (70, M ), 235 (100), 131 (86), 104 (32). Anal. calc. for C44H44O5: C 80.95, H 6.79; found: C 81.08,
H 6.87.

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4-{{[4'-(Dodecyloxy)[1,1'-biphenyl]-4-yl]oxy}carbonyl}phenyl [2.2]Para-cyclophane-4-carboxylate (ˆ4-
{{[4'-(Dodecyloxy)[1,1'-biphenyl]-4-yl]oxy}carbonyl}phenyl Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hex-
aene-5-carboxylate; Ib): Yield 0.22 g (78%). M.p. 146 1478. 1H-NMR (CDCl3): 0.89 (t, Me); 1.23 1.54
(m, 1 8 H, 9 CH); 1.75 1.85 (m, 2 H, CH2); 2.88 2.93 (m, 1H, C H2CH2 (PC)); 3.03 3.29 (m, 6 H, CH2CH2
2
(PC)); 4.00 (t, CH2O); 4.14 4.21 (m, 1H, C H2CH2 (PC)); 6.51 6.66 ( m, 5 arom. H (PC)); 6.77 (dd, 3J ˆ 7.8,
4J ˆ 1.9, 1 arom. H (PC)); 6.98 (d, J ˆ 8.7, 2 arom. H); 7.28 (d, J ˆ 8.7, 2 arom. H); 7.38 (d, 4J ˆ 1.9, 1 arom. H
(PC)); 7.41( d, J ˆ 8.7, 2 arom. H); 7.52 (d, J ˆ 8.7, 2 arom. H); 7.61( d, J ˆ 8.7, 2 arom. H); 8.34 (d, J ˆ 8.7,
‡
2 arom. H). MS: 708 (68, M ), 235 (100), 131 (78), 104 (28). Anal. calc. for C48H52O5: C 81.32, H 7.39; found:
C 81.61, H 7.45.
Bis[4'-(pentyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(pentyloxy)[1,1'-
biphenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIa): Yield 0.25 g
‡
(81%). 1H-NMR: Table. MS: 772 (34, M ), 185 (91), 131 (100). Anal. calc. for C52H52O6: C 80.80, H 6.78;
found: C 80.81, H 6.61.
Table. 1H-NMR Data of PC Derivatives IIa k and IIIa d. Data in italics are coincident for all members of the noted series.
Protons of the aliphatic chain
(OCH2 ------ CH2 ------ (CH2)k ------ CH3)2
Bridge CH2CH2
Protons of the
aromatic ring
of PC moiety
Aromatic protons
(t, 4 H)
(m, 4 H)
(m, 4k H)
(t, 6 H)
IIa 4.02
1.35 1.53
0.95
.53
0.92
.30
1
b
c
d
e
f
4.011
4.02
4.01
4.02
4.011
4.011
7.00 (d, J ˆ 8.7, 4 H)
7.30 (d, J ˆ 8.6, 4 H)
7.54 (d, J ˆ 8.7, 4 H)
7.64 (d, J ˆ 8.6, 4 H)
1.27 1.53
1.23 1.53
1.23 1.53
0.92
0.91
0.91
2.96 3.08 (m, 2 H) 6.69 (d, 3J, 2 H)
3.23 3.32 (m, 4 H) 6.92 (dd, 3J, 4J, 2 H)
4.17 4.26 (m, 2 H) 7.43 (d, 4J, 2 H)
1.78 1.86
.53
.53
0.90
0.89
.23
.23
1
1
g
2.96 3.08 (m, 2 H) 6.67 (d, 3J, 2 H)
6.99 (d, J ˆ 8.9, 4 H)
IIh 4.05
1.78 1.88
1.75 1.84
1.78 1.86
1.79 1.88
1.75 1.85
1.24 1.53
1.23 1.53
0.89
0.89
3.23 3.32 (m, 4 H) 6.89 (dd, 3J, 4J, 2 H) 7.32 (s, 8 H)
i
4.06
4.15 4.24 (m, 2 H) 7.40 (d, 4J, 2 H)
8.17 (d, J ˆ 8.9, 4 H)
6.95 (d, J ˆ 9.0, 4 H)
7.14 (d, J ˆ 9.0, 4 H)
7.40 (d, J ˆ 8.7, 4 H)
8.33 (d, J ˆ 8.7, 4 H)
2.98 3.09 (m, 2 H) 6.70 (d, 3J, 2 H)
3.24 3.33 (m, 4 H) 6.91 (dd, 3J, 4J, 2 H)
4.15 4.24 (m, 2 H) 7.43 (d, 4J, 2 H)
IIj
k
3.97
2.94 3.05 (m, 2 H)
3.14 3.24 (m, 2 H) 7.48 (s, 2 H)
7.00 (d, J ˆ 8.7, 4 H)
7.32 (d, J ˆ 8.6, 4 H)
IIIa
b
1.32 1.53
1.24 1.53
0.92
0.89
4.02
4.06
3.97
3.26 3.36 (m, 2 H) 6.63 6.72 (m, 4 H) 7.54 (d, J ˆ 8.7, 4 H)
4.15 4.25 (m, 2 H)
7.65 (d, J ˆ 8.6, 4 H)
2.93 3.04 (m, 2 H)
6.99 (d, J ˆ 8.9, 4 H)
7.34 (s, 8 H)
8.17 (d, J ˆ 8.9, 4 H)
3.11 3.22 (m, 2 H) 7.48 (s, 2 H)
3.24 3.38 (m, 2 H) 6.63 6.70 (m, 4 H)
4.13 4.23 (m, 2 H)
c
1.24 1.53
1.24 1.53
0.89
0.89
2.95 3.07 (m, 2 H)
3.12 3.23 (m, 2 H) 7.46 (s, 2 H)
6.95 (d, J ˆ 9.0, 4 H)
7.14 (d, J ˆ 9.0, 4 H)
d
3.27 3.39 (m, 2 H) 6.61 6.70 ( m, 4 H) 7.43 (d, J ˆ 8.7, 4 H)
4.14 4.24 (m, 2 H)
8.34 (d, J ˆ 8.7, 4 H)
Bis[4'-(hexyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(hexyloxy)[1,1'-bi-
phenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIb): Yield 0.26 g (81%).
‡
1H-NMR: Table. MS: 801(10, M ), 531(90), 131(100). Anal. calc. for C 54H56O6: C 80.97, H 7.05; found: C 80.67,
H 7.00.
Bis[4'-(heptyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(heptyloxy)[1,1'-
biphenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIc): Yield 0.26 g
‡
(78%). 1H-NMR: Table. MS: 829 (12, M ), 545 (100), 131 (66). Anal. calc. for C56H60O6: C 81.13, H 7.29;
found: C 81.16, H 7.30.

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Helvetica Chimica Acta Vol. 85 (2002)
Bis[4'-(octyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(octyloxy)[1,1'-bi-
phenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IId): Yield 0.28 g (81%).
‡
1H-NMR: Table. MS: 857 (8, M ), 559 (100), 131 (66). Anal. calc. for C58H64O6: C 81.27, H 7.53; found: C 81.20,
H 7.59.
Bis[4'-(nonyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(nonyloxy)[1,1'-
biphenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIe): Yield 0.29 g
‡
(82%). 1H-NMR: Table. MS: 885 (5, M ), 185 (74), 131 (100). Anal. calc. for C60H68O6: C 81.41, H 7.74;
found: C 81.37, H 7.89.
Bis[4'-(decyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(decyloxy)[1,1'-bi-
phenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIf): Yield 0.30 g (82%).
‡
1H-NMR: Table. MS: 913 (2, M ), 587 (94), 131 (100). Anal. calc. for C62H72O6: C 81.54, H 7.95; found: C 81.67,
H 7.91.
Bis[4'-(undecyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis[4'-(undecy-
loxy)[1,1'-biphenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIg): Yield
‡
0.32 g (85%). 1H-NMR: Table. MS: 941(10, M ), 601 (100), 131 (58). Anal. calc. for C64H76O6: C 81.66,
H 8.14; found: C 81.50, H 8.27.
Bis{4-{[4-(decyloxy)benzoyl]oxy}phenyl} [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis{4-{[4-(decyloxy)-
benzoyl]oxy}phenyl} Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIh): Yield 0.29 g
‡
(72%). 1H-NMR: Table. MS: 1001 (8, M ), 631(54), 261(100). Anal. calc. for C 64H72O10: C 76.77, H 7.25;
found: C 76.69, H 7.33.
Bis{4-{[4-(tetradecyloxy)benzoyl]oxy}phenyl} [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis{4-{[4-(tetra-
decyloxy)benzoyl]oxy}phenyl} Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIi):
‡
Yield 0.35 g (79%). 1H-NMR: Table. MS: 1112 (10, M ), 690 (60), 317 (100). Anal. calc. for C72H88O10
:
C 77.67, H 7.97; found: C 77.30, H 7.82.
Bis{4-{[4-(decyloxy)phenoxy]carbonyl}phenyl} [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis{4-{[4-(de-
cyloxy)phenoxy]carbonyl}phenyl} Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxylate; IIj):
‡
Yield 0.34 g (85%). 1H-NMR: Table. MS: 1001 (5, M ), 631 (28), 121 (100). Anal. calc. for C64H72O10: C 76.77,
H 7.25; found: C 76.81, H 7.32.
Bis{4-{[4-(tetradecyloxy)phenoxy]carbonyl}phenyl} [2.2]Paracyclophane-4,16-dicarboxylate (ˆ Bis{4-{[4-
(tetradecyloxy)phenoxy]carbonyl}phenyl} Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,11-dicarboxy-
‡
late; IIk): Yield 0.36 g (81%). 1H-NMR: Table. MS: 1112 (10, M ), 687 (100), 121 (78). Anal. calc. for
C72H88O10: C 77.67, H 7.97; found: C 77.43, H 8.01.
Bis[4'-(hexyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,7-dicarboxylate (ˆ Bis[4'-(hexyloxy)[1,1'-bi-
phenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,15-dicarboxylate; IIIa): Yield 0.28 g (87%).
‡
1H-NMR: Table. MS: 800 (10, M ), 531 (100), 186 (28). Anal. calc. for C54H56O6: C 80.97, H 7.05; found: C 80.95,
H 6.75.
Bis[4'-(tetradecyloxy)[1,1'-biphenyl]-4-yl] [2.2]Paracyclophane-4,7-dicarboxylate (ˆ Bis[4'-(tetradecy-
loxy)[1,1'-biphenyl]-4-yl] Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,15-dicarboxylate; IIIb): Yield
‡
0.34 g (83%). 1H-NMR: Table. MS: 1025 (8, M ), 643 (100), 186 (48). Anal. calc. for C70H88O6: C 82.00, H 8.65;
found: C 82.17, H 8.69.
Bis{4-{[4-(tetradecyloxy)benzoyl]oxy}phenyl} [2.2]Paracyclophane-4,7-dicarboxylate (ˆ Bis{4-{[4-(tetrade-
cyloxy)benzoyl]oxy}phenyl} Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,15-dicarboxylate; IIIc):
‡
Yield 0.34 g (76%). 1H-NMR: Table. MS: 1113 (5, M ), 573 (50), 121 (100). Anal. calc. for C72H88O10
:
C 77.67, H 7.97; found: C 77.70, H 7.99.
Bis{4-{[4-(tetradecyloxy)phenoxy]carbonyl}phenyl} [2.2]Paracyclophane-4,7-dicarboxylate (ˆ Bis{4-{[4-
(tetradecyloxy)phenoxy]carbonyl}phenyl} Tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaene-5,15-dicarboxy-
‡
late; IIId): Yield 0.32 g (72%). 1H-NMR: Table. MS: 1113 (3, M ), 317 (100). Anal. calc. for C72H88O10
:
C 77.67, H 7.97; found: C 77.63, H 7.92.
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Received July 13, 2001