Liquid crystal control of bimolecular thermal reactions. Highly regioselective pericycloaddition of fumarates to 2,6-dialkoxyanthracenes in liquid-crystalline media

Article abstract of DOI:10.1021/ja960282w

The ability of liquid crystalline solvent phases to control the stereochemical course of bimolecular thermal reactions of 2,6-dialkoxyanthracenes with a series of fumarates conducted at 130-180°C has been examined, primarily with respect to the structural compatibility of the solutes with the solvent mesogens. For the case of the model thermal [4 + 2] cycloadditions of 2,6-bis(decyloxy)anthracene to bis(trans-4-cyclohexylcyclohexyl) and cholesteryl trans-4-cyclohexylcyclohexyl fumarates at 130-150°C, cholesteryl 2,4-dichlorobenzoate (CDCB) and bis(4-pentyloxyphenyl) trans-1,4-cyclohexanedicarboxylate (BPCD) serve well as cholesteric and smectic liquid crystalline solvents and result in the preferential formation of syn-isomers with an extremely high level of regioselection (syn/anti ≥ 20/1). In contrast, the isotropic solvents with closely related structures give isomer ratios of only ≥ 3/1. Structural similarities between the solutes and the solvent mesogens appear to play a key and influential role in controlling the stereochemical course of the reaction. The temperature dependence for the isomer distribution affords an estimate of the differences of solvation enthalpy and entropy between syn and anti transition states in the anisotropic media.

Full text of DOI:10.1021/ja960282w

5346
J. Am. Chem. Soc. 1996, 118, 5346-5352
Liquid Crystal Control of Bimolecular Thermal Reactions.
Highly Regioselective Pericycloaddition of Fumarates to
2,6-Dialkoxyanthracenes in Liquid-Crystalline Media
Hisao Kansui, Shingo Hiraoka, and Takehisa Kunieda*
Contribution from the Faculty of Pharmaceutical Sciences, Kumamoto UniVersity,
5-1 Oe-honmachi, Kumamoto 862, Japan
ReceiVed January 26, 1996X
Abstract: The ability of liquid crystalline solvent phases to control the stereochemical course of bimolecular thermal
reactions of 2,6-dialkoxyanthracenes with a series of fumarates conducted at 130-180 °C has been examined, primarily
with respect to the structural compatibility of the solutes with the solvent mesogens. For the case of the model
thermal [4 + 2] cycloadditions of 2,6-bis(decyloxy)anthracene to bis (trans-4-cyclohexylcyclohexyl) and cholesteryl
trans-4-cyclohexylcyclohexyl fumarates at 130-150 °C, cholesteryl 2,4-dichlorobenzoate(CDCB) and bis(4-
pentyloxyphenyl) trans-1,4-cyclohexanedicarboxylate(BPCD) serve well as cholesteric and smectic liquid crystalline
solvents and result in the preferential formation of syn-isomers with an extremely high level of regioselection (syn/
anti g 20/1). In contrast, the isotropic solvents with closely related structures give isomer ratios of only g3/1.
Structural similarities between the solutes and the solvent mesogens appear to play a key and influential role in
controlling the stereochemical course of the reaction. The temperature dependence for the isomer distribution affords
an estimate of the differences of solvation enthalpy and entropy between syn and anti transition states in the anisotropic
media.
There is considerable interest in the properties of anisotropic
which possess a high rigidity of ordering have proved to be
sufficiently effective to influence the course of uni- and
bimolecular photochemical reactions, primarily by controlling
the orientation of reactant molecules.10 The ability of liquid
crystal phases to control reactivity is recognized to depend on
a number of factors, including the shape of the reactant
molecules, flexibility, polarizability, and mesophase type of the
medium. The weak anisotropic constraints attributable to liquid
crystalline alignments, however, have not been sufficiently
strong to effectively control thermochemical reactions, when
these are conducted at elevated temperatures, except for a few
well documented exceptions.11 Poorly ordered orientation of
environments such as crystalline solids,1 liquid crystals,2 mi-
celles,3 monolayers4 and host-guest assemblies5 which can
affect on the chemical behavior of included solute molecules.
Thermotropic liquid crystals,2,6 for which mesomorphic proper-
ties are maintained over a wide temperature range, have high
potential as unique reaction solvents, because their rigidity of
molecular ordering and fluidity make them suitable for solute
diffusion. The potential effect of thermotropic liquid crystals
on stereochemical control of a variety of photochemical7 and
thermal reactions8 has been reported subsequent to the pioneer-
ing study by Nerbonne and Weiss.9 Smectic solvent phases
X Abstract published in AdVance ACS Abstracts, May 15, 1996.
(1) For recent reviews, see: (a) Adachi, L; Berkovitch-Yellin, Z.;
Weissbuch, I.; Mil, J.; Shimon, L. J. W.; Lahav, M.; Leiserowitz, L.
Angew.Chem. Int. Ed. Engl, 1987, 26, 1171. (b) Rao, C. N. R. Chemical
Approaches in the Synthesis of Inorganic Materials; John Wiley & Sons:
New York, 1993. (c) Toda, F. Synlett 1993, 5, 303. (d) Toda, F. J. Synth.
Org. Chem. Jpn. 1994, 52, 923.
(7) (a) Aviv, G.; Sagiv, J.; Yogev, A. Mol. Cryst. Liq. Cryst. 1976, 36,
349. (b) Nerbonne, J. M.; Weiss, R. G. J. Am. Chem. Soc. 1979, 101, 402.
(c) Kunieda, T.; Takahashi, T.; Hirobe, M. Tetrahedron Lett. 1983, 24,
5107. (d) Ramesh, V.; Weiss, R. G. Mol. Cryst. Liq. Cryst. 1986, 135, 13.
(e) Ramesh, V.; Weiss, R. G. J. O. Chem. 1986, 51, 2535. (f) Nagamatsu,
T.; Kawano, C.; Orita, Y.; Kunieda, T. Tetrahedron Lett. 1987, 28, 3263.
(8) (a) Sergeev, G. B.; Battyuk, V. A.; Shibatina, T. I. Kinet. Katal. 1983,
24, 538. (b) Batyuk, V. A.; Shabatina, T. I.; Sergeev, G. B. Mol. Cryst.
Liq. Cryst. 1989, 166, 105. (c) Batyuk, V. A.; Boronina, T. N; Chudinov,
G. E. I.; Sergeev, G. B. Liq. Cryst. 1989, 4, 181. (d) De Maria, P.; Mariani,
P.; Rustichelli, F.; Samori, B. Mol. Cryst. Liq. Cryst. 1984, 116, 115. (e)
De Maria, P.; Lodi, A.; Samori, B.; Rustichelli, F.; Torquati, G. J. Am.
Chem. Soc. 1984, 106, 653. (f) Samori, B.; Fiocco, L. J. Am. Chem. Soc.
1982, 104, 2634. (g) Melone, S.; Mosini, V.; Nicoletti, R.; Samori, B.;
Torquati, G. Mol. Cryst. Liq. Cryst. 1983, 98, 399. (h) Samori, B.; De Maria,
P.; Mariani, P.; Rustichelli, F.; Zani, P. Tetrahedron 1987, 43, 1409. (i) De
Maria, P.; Samori, B.; Tampieri, A.; Zani, P. Bull. Chem. Soc. Jpn. 1988,
61, 1773. (j) Albertini, G.; Mariani, P.; Rustichelli, F.; Samori, B. Mol.
Cryst. Liq. Cryst. 1988, 163, 163. (k) Kansui, H; Kunieda, T. Tetrahedron
Lett. 1995, 33, 5899.
(2) For recent reviews, see: (a) Ramamurthy, V. Tetrahedron 1986, 42,
5753. (b) Scheffer, J. Tetrahedron 1987, 43, 7. (c) Kreysig, D.; Stumpe, J.
Selected Topics in Liquid Crystal Research; Koswing, H. D., Ed.;
Akademine-Verlag: Berlin, 1990; Chapter 4. (d) Kunieda, T. J. Synth. Org.
Chem. Jpn. 1990, 48, 509. (e) Leigh, W. J. Liquid Crystals. Applications
and Uses; Bahadur, B., Ed.; World Scientific: Singapore, 1991; Chapter
27. (f) Weiss, R. G. Photochemistry in Organized and Constrained Media;
Ramamurthy, V., Ed..; VCH Publishers: New York, 1991; Chapter 14.
(3) For recent reviews, see: (a) Degiorgio, V.; Corti, M. Physics of
Amphiphiles: Micelles, Vesicles and Microemulsions; North-Holland:
Amsterdam, 1985. (b) Hoffmann, H.; Ebert, G. Angew. Chem., Int. Ed.
Engl. 1988, 27, 902. (c) Aoki, S. J. Synth. Org. Chem. Jpn. 1994, 52, 423.
(4) For recent reviews, see: (a) Roberts, G. G. AdV. Phys. 1985, 34,
475. (b) Israelachvili, J. N. Intermolecular and Surface Forces. With
Applications to Colloidal and Biological Systems; Academic Press: London,
1985. (c) Ulman, A. An Introduction To Ultrathin Organic Films: From
Langmuir-Blodgett To Self-Assembly; Academic Press: Boston, 1991.
(5) For recent reviews, see: (a) Lehn, J. M. Science 1985, 227, 849. (b)
Rebek, J., Jr. Angew. Chem., Int. Ed. Engl. 1990, 29, 245. (c) Lehn, J. M.
1990, 29, 1304.
(9) (a) Nerbonne, J. M.; Weiss, R. G. J. Am. Chem. Soc. 1978, 100,
2571. (b) Nerbonne, J. M.; Weiss, R. G. J. Am. Chem. Soc. 1978, 100,
5953.
(10) (a) Kelker, H.; Hatz, R. Handbook of Liquid Crystals; Verlag
Chemie: Weinheim, 1980. (b) Liquid Crystals. The Fourth State of Matter;
Saeva, F. D., Ed.; Marcel Dekker: New York, 1979. (c) Maitlis, P. M.
Angew. Chem., Int. Ed. Engl. 1991, 30, 375.
(6) For recent reviews, see: (a) Bauer, S.; Fischer, H.; Ringsdorf, H.
Angew. Chem., Int. Ed. Engl. 1993, 32, 1589. (b) Kusabayashi, S. Kikan
Kagaku Sosetsu 1994, 22, 2. (c) Paleos, C. M.; Tsiourvas, D. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1696.
(11) (a) Samori, B.; Fiocco, L. J. Am. Chem. Soc. 1982, 104, 2634. (b)
Maria, P. D.; Lodi, A.; Samori, B.; Rustichelli, F.; Torquati, G. J. Am.
Chem. Soc. 1984, 106, 653. (c) Leigh, W. J.; Mitchell, D. S. J. Am. Chem.
Soc. 1988, 110, 1311.
S0002-7863(96)00282-X CCC: $12.00 © 1996 American Chemical Society

Liquid Crystal Control of Thermal Reactions
J. Am. Chem. Soc., Vol. 118, No. 23, 1996 5347
solutes in the transition state might be primarily responsible
for the inability of such anisotropic media to regulate thermo-
chemical reactivities. Using this as a hypothesis, we recently
reported the promising use of liquid crystal dienophiles which
served as stereochmical controllers of uncatalyzed Diels-Alder
reactions of 2,6-dialkoxyanthracenes and fumarates.12 This
cycloaddition proceeded with a reasonable level of regioselec-
tivity even at 150 °C. At these conditions, the liquid crystalline
fumarates were ordered and aligned during the reaction and,
thus, could be utilized as both dienophiles and as anisotropic
media. In a preliminary report,13 we showed that the molecular
ordering inherent in cholesteric liquid crystalline solvent phases
was effective enough to regulate such intermolecular pericy-
cloadditions (at 130 °C) with significantly high regioselectivity
in favor of syn-adducts. This was true for cases where the
dienophiles were carefully modified, based on structural similar-
ity to the mesogens.14
Figure 1. Liquid crystalline range (°C) (C, cholesteric phase; Sm,
This paper describes the results of an extension of these
studies on the ability of liquid crystalline media, including
smectic phases, to facilitate the predominant formation of syn-
isomers (3) in the model pericyclic reactions of 2,6-dialkoxy-
anthracenes (2) with a series of fumarates (1). The reactions
were carried out at 130 to 150 °C. These studies help to clarify
the relationship between the effectiveness of the liquid crystal
in controlling this type of thermal reaction as well as structural
requirements for both reactants and solvent mesogens. The
variation in the syn(3)/anti(4) isomer ratio was further examined
as a function of temperature of the reaction medium of
cholesteric and smectic liquid crystals as well as for the closely
related isotropic model solvents. This provides information on
the effect of the liquid crystalline solvent phase on isomer
distribution as this relates to differences in activation parameters
between the transition states leading to syn(3) and anti(4)-
isomers. It is noteworthy that a kinetic treatment of a thermal
reaction conducted in liquid crystalline media has been reported
by Leigh and Mitchell.15
smectic phase; N, nematic phase.
Modification of Reactants. The reactants were modified
with emphasis on the structural similarities to the mesomorphic
solvents CDCB and BPCD, since solutes of a size and shape
similar to those of the mesogens would be expected to be rigidly
incorporated into an ordered matrix and to show reactivities
specific to the solvents. A series of fumarates (1a-c) bearing
cholesteryl or trans-4-cyclohexylcyclohexyl (trans-CC) moieties
as ester groups were primarily explored as dienophiles. The
trans-CC moiety represents a partial structure of a cholesterol
skeleton with good affinity for CDCB and is stereochemically
similar to BPCD. Additional ester moieties including cis-CC,
straight-chain alkyl, and aryl groups were also examined as seen
in 1d-l. As the enophile counterparts, the 2,6-dialkoxyan-
thracenes with varying chain length such as 2,6-bis(decyloxy),
2,6-bis(methoxyethxy), and 2,6-dibutoxy derivatives were used.
Assignment of syn- and anti-Cycloadducts. When an
equimolar mixture of 2,6-dibutoxy- and 2,6-bis(decyloxy)-
anthracenes and a series of fumarates was heated in isotropic
mesitylene solution at 150 °C (for 48 h), syn (3), and anti (4)
cycloadducts were obtained in 80-90% yield in a ratio of 2:1.
The identities of the syn- and anti-structures, except for the
aryl esters (1e-h),18, 19 were established on the basis of their
NMR signals assignable to the aromatic protons, Ha (Hd) and
Hc (Hf), which appeared at δ 6.74-6.90 and δ 7.03-7.20. The
assignment was further confirmed by saponification to the syn-
and anti-cycloadduct dicarboxylic acids (R1 ) R2 ) H) which
were readily distinguishable from one another by their NMR
spectra.18 ,19 The syn/anti ratio was determined by NMR (400M
Hz) and /or HPLC (LiCrosorb Si60)-analysis of the product
mixture.
Pericycloadditions in Cholesteric Solvent (at 130 °C). A
preliminary study showed that CDCB was the anisotropic
solvent of choice for the highly regioselective cycloadditions
of the fumarates including cholesteryl and trans-4-cyclohexy-
lcyclohexyl esters to 2,6-dibutoxy- and 2,6-bis(decyloxy)-
anthracenes.19 Thus, equimolar samples of dienophile (1) and
diene (2) were heated in 30-fold equimolar amounts of the
cholesteric CDCB solvent at 130 °C under argon. These
concentrations of the solutes (6.67 mol%) were sufficiently low
to maintain the mesomorphic reaction phases during the reaction
period, as evidenced by differential scanning calorimetric (DSC)
analysis and polarizing thermal microscopy of the doped
mixtures. Table 1 shows some typical depressions of the DSC-
Results
Mesomorphic Solvents Employed. Cholesteryl esters, cho-
lesteryl 2,4-dichlorobenzoate (CDCB) and cholesteryl hydro-
cinnamate (CHC), were obtained commercially, and smectic
compounds, bis(4-pentyloxyphenyl)trans-1,4-cyclohexanedicar-
boxylate (BPCD)16 and trans-1,4-cyclohexylenyl bis(4-penty-
loxybenzoate) (CBPB),17 were prepared by standard proce-
dures.16 The phase-transition temperatures for these derivatives,
based on differential thermal analysis, are shown in Figure 1.
The mesogenic esters, CDCB and BPCD, have a relatively broad
temperature range of cholesteric and smectic mesomorphic
states, respectively, at around 150 °C, at which temperature the
probe pericycloadditions proceed smoothly. Thus, for the
cycloadditions examined at 130 to 180 °C, CDCB and the
structurally related CHC served as cholesteric and isotropic
solvents. The smectic liquid crystal BPCD was used as an
anisotropic (Sm A) solvent for the reactions conducted in the
temperature range 150-180 °C, and the structually similar
“inverse ester”, CBPB, served as the isotropic phase solvent
for control experiments.
(12) Yamaguchi, T.; Yoshida, T.; Nagamatsu, T.; Kunieda, T. Tetrahe-
dron Lett. 1991, 32, 1729.
(13) Hiraoka, S.; Yoshida, T.; Kansui, H.; Kunieda, T. Tetrahedron Lett.
1992, 33, 4341.
(14) Weiss, R. G. Tetrahedron 1988, 44, 3413.
(15) Leigh, W. J.; Mitchell, D. S. J. Am. Chem. Soc. 1992, 114, 5005.
(16) Neubert, M. E.; Ferrato, J. P.; Carpenter, R. E. Mol. Cryst. Liq.
Cryst. 1979, 53, 229.
(17) (a) Dewar, M. J. S.; Goldberg, R. S. J. Am. Chem. Soc. 1970, 92,
1582. (b) Owen, L. N.; Robions, P. A. J. Chem. Soc. 1949, 320.
(18) Hagishita, S.; Kuriyama, K. Tetrahedron 1972, 28, 1435.
(19) Petti, M. A.; Shepodd, T. J.; Barrans, R. E.; Dougherty, D. A. J.
Am. Chem. Soc. 1988, 110, 6825.

5348 J. Am. Chem. Soc., Vol. 118, No. 23, 1996
Kansui et al.
Table 1. Anisotropic Range of Neat and Reactant-Doped Liquid
Crystals
liquid-crystalline
range (°C)a
CDCBb + none
130.0-213.0
128.4-206.3
126.2-196.4
101.0-193.1
100.2-192.7
CDCB + 6.70 mol% [1a + 2 (R ) decyl)]
CDCB + 6.70 mol% [1c + 2 (R ) decyl)]
BPCDc + none
BPCD + 6.70 mol% [1c + 2 (R ) decyl)]
a Measured by differential scanning calorimeter. b CDCB: cholesteryl
2,4-dichlorobenzoate. c BPCD: bis(p-pentyloxyphenyl) trans-1,4-cy-
clohexanedicarboxylate.
Figure 2. Fumaric acid esters primarily explored as dienophiles.
Scheme 1
relative isomer yields to shift toward equal values, as would be
expected for a homogeneous reaction mechanisms. The product
ratios thus obtained were kinetic product ratios and not
thermodynamic equilibrium ratios, since no isomerization of
either adduct was apparent when pure samples of syn- and anti-
adducts were heated at 130-180 °C for extended periods of
time.
Discussion
In liquid crystalline solvents, solute molecules are probably
incorporated in an optimum packing arrangement, based on
steric and electronic factors. Product distribution would be
expected to be regulated considerably when the reactants are
designed to be accommodated efficiently in a liquid crystalline
matrix, since the reaction should proceed through the pathway
in favor of the least disruption of local solvent order at the
transition states. Such an effect woud be expected to be
generally greater in tightly ordered smectic solvents than in
cholesterics and nematics.
detected phase-transition temperatures for reaction mixtures
doped with reactants.
Cholesteryl trans-4-cyclohexylcyclohexyl (trans-CC) (1a)
and cholesteryl p-phenylphenyl fumarates (1e) reacted with 2,6-
bis(decyloxy)anthracene (2) in CDCB solvent at 130 °C to give
surprisingly high syn/anti ratios of 19:1 and 15.9:1, respectively,
while the reactions conducted in the isotropic media such as
CHC and mesitylene resulted in significantly lower levels of
diastereoselection. As seen in Table 2, the syn/anti ratios are
highly dependent on the structures of the reactants. The
cholesteric reactions with cholesteryl and trans-CC fumarates
generally proceed with significantly higher stereoselectivities
than those in the isotropic media, reflecting the unique effect
of the molecular ordering of cholesteric solvent on regioselec-
tivity. Long chain esters such as dioctyl and bis(1-pentylhexyl)
fumarates (1j, k) were not so effective for regiocontrol of the
cycloadditions.
Cycloadditions in Smectic Solvent (at 150 °C). The
pericyclic reactions of diene and dienophile were conducted at
150 °C in the smectic BPCD solvent and the closely related
CBPB, used as isotropic media under analogous conditions as
above. In the reaction with 2,6-bis(decyloxy)anthracene in the
smectic solvent, cholesteryl (trans-4-cyclohexylcyclohexyl) and
bis(trans-4-cyclohexylcyclohexyl)fumarates (1a and b) were
sufficiently effective dienophiles to allow a high level of
diastereoselectivity, with syn/anti ratios of 16.9:1 and 15.1:1,
respectively. In contrast, the isotropic reactions in CBPB gave
syn/anti ratios of only g2.5:1. Table 3 includes some other
examples which favorably reflect the potential effect of smectic
solvent phases on regioselective control of thermal cycloaddi-
tions.
In this study, the dienophiles were modified primarily based
on structural similarities to the mesogenic solvents in such a
way that they would be expected to be tightly oriented with
their long molecular axes and molecular planes parallel to those
of liquid crystalline solvents. The fumarates bearing cholesteryl
and trans-CC moieties whose shapes are somewhat similar to
those of the mesogens and the anthracene derivatives with
sufficiently long alkoxy groups would be expected to disturb
the solvent order least by rigid incorporation into the liquid
crystalline CDCB and BPCD solvent matrixs. This appears to
be true as evidenced by the small depressions of the phase-
transition temperatures upon addition to the mesomorphic
solvents (Table 1).
The results clearly indicate that the observed effects are,as
expected, highly dependent on solute structures and that the
molecular order in both cholesteric and smectic liquid crystalline
solvent phases is capable of efficiently distinguishing between
syn- and anti-transition states, particularly when cholesteryl and
trans-CC fumarates reacted with 2,6-bis(decyloxy)anthracene
which might be structurally compatible with the mesogens. It
is noteworthy that extremely high efficiencies of 13-19:1 (at
130 °C in cholesteric CDCB solvent) and 15-17:1 (at 150 °C
in smectic BPCD solvent) were attained for the liquid crystalline
phases, in contrast to the 2-3:1 ratios observed in the isotropic
model solvents with closely related structures. The smectic
phase reaction of 2,6-bis(decyloxy)anthracene with bis(trans-
4-cyclohexylcyclohexyl) fumarate in BPCD gave the highest
selectivity of 24:1 at 140 °C. The trans-substitution mode of
the cyclohexyl moiety is essential for effective control and the
reactions of cis-CC ester with 2,6-dialkoxyanthracene in either
cholesteric or smectic solvent resulted in much lower selectivity
(syn- to anti-ratios of 2-3:1), which is comparable to those
observed for isotropic media. Efficiencies of the other esters
Temperature Dependence of syn to anti Ratios. The syn/
anti adduct ratios were highly temperature dependent between
130 and 180 °C in the cholesteric phase of CDCB and between
140 and 170 °C for the case of the smectic phase of BPCD.
The reactions were performed in the isotropic phase of CHC
and CBPB. Data relative to the cycloaddtion of 1c to 2 (R )
decyl) are summarized in Table 4. For the reactions in the liquid
crystal solvents, increasing the reaction temperature caused the

Liquid Crystal Control of Thermal Reactions
J. Am. Chem. Soc., Vol. 118, No. 23, 1996 5349
Figure 5. The syn to anti ratio dependence as a function of
temperature, obtained from the reaction of 1c and 2 (R ) decyl) in (i)
cholesteric CDCB and (ii) isotropic CHC solvents in the molar ratio
of 1:1:30 between 130 and 180 °C.
Figure 3. A plot of the syn (3)/anti (4) ratio as a function of
concentrations of the solutes for thermal cycloaddition of 1c to 2 (R )
decyl) in CDCB at 130 °C.
Figure 6. The syn to anti ratio dependence as a function of
temperature, obtained from the reaction of 1c and 2 (R ) decyl) in (i)
smectic BPCD and (ii) isotropic CBPB solvents in the molar ratio of
1:1:30 (between 140 and 170 °C).
Figure 4. Relative orientation of the solutes.
examined were intermediate between those of trans-CC and cis-
CC moieties.
As seen in Figure 3, the anisotropic rigidity of the local
solvent order appears to play an important role in controlling
the stereochemical course of the reaction, resulting in a high
level of diastereoselection. When less than a 25-fold molar
excess of the anisotropic solvent over the reactant diene or
dienophile was used, a sharp decrease in diastereoselectivity
was observed. This may be the result of either phase separation
into solute-rich phases of lower order (probably isotropic) or
the formation of a new less ordered mesomorphic phases, which
has been extensively discussed by Leigh and co-workers.20
Stereochemical control of bimolecular Diels-Alder reactions
are greatly affected by anisotropic solvents, when the structures
of reactants are similar to those of the mesogens, which allow
them to be firmly accommodated in the liquid crystalline solvent
lattice. Thus, the predominant formation of syn-adducts can
be rationalized by the syn-transition states (s-t and s-c) close to
the preferred dipolar orientations as is depicted in Figure 4 in
which both diene and dienophile are oriented with their long
molecular axes parallel to those of the mesogenic solvent
molecules, in spite of relatively small differences in steric shapes
between syn- and anti-orientation.
(∆∆Hq
) and entropy (∆∆Sqsyn-anti), of the transition
syn-anti
states leading to syn and anti cycloadducts are given by the
shapes and intercepts of the plots (eq 1).
ln (syn/anti) ) -∆∆Hqsyn-anti/RT + ∆∆Sqsyn-anti/R (1)
As seen in Table 5, the liquid crystalline phases stabilize the
syn-transition states by 13-19 kcal/mol, relative to the anti-
reactive complexes. Large negative entropy differences greatly
favor the formation of syn-adducts and the rather small enthalpy
associated with bulk liquid crystalline order in mesophases. The
result presented here provide a spectacular example of liquid
crystal control, compared to the lower effects reported by Leigh
and co-worker15 for a related case of cycloadditions.
Conclusions
Regioselective control of bimolecular pericyclic reactions
conducted in liquid crystalline media depends primarily on
structural similarities between the solutes and the mesogenic
solvent molecules. Thus, the thermal cycloadditions of an-
thracenes and fumaric acid derivatives designed on the basis of
structural compatibilities with the solvent mesogens proceed in
either cholesteric or smectic liquid crystals with an extremely
high level of diastereoselection. This study demonstrates the
potential of thermotropic liquid crystalline media in controlling
stereochemical courses of thermochemical reactions conducted
at elevated temperatures. Studies of the temperature dependence
of the isomeric syn- and anti-ratios afford estimates of the
Figure 5 shows a semilogarithmic plot of inverse temperature
vs the ratio of syn- and anti-cycloadducts obtained in cholesteric
CDCB and isotropic CHC solvents. Similar plots were obtained
from the cycloadditions conducted in smectic BPCD and
model isotropic solvents (Figure 6). Differences in enthalpy
(20) (a) Fahie, B. J.; Mitchell, D. S.; Leigh, W. J. Can. J. Chem. 1989,
67, 148. (b) Fahie, B. J.; Mitchell, D. S.; Workentin, M. S.; Leigh, W. J. J.
Am. Chem. Soc. 1989, 111, 2916.

5350 J. Am. Chem. Soc., Vol. 118, No. 23, 1996
Kansui et al.
Table 2. Isomer Ratios from Thermal Cycloadditions of 1 to 2 in Cholesteric (CDCB) and Isotropic Solvents (CHC, Mesitylene)a
fumarates (1)
syn(3)/anti(4) ratiob
CHC(i)c (mesitylene)
anthracenes (2)
R1
R2
R3
CDCB(c)c
cholesteryl
cholesteryl
cholesteryl
cholesteryl
trans-CC
trans-CC
trans-CC
cis-CC
cholesteryl
trans-CC
cholesteryl
cholesteryl
trans-CC
trans-CC
cyclohexyl
octyl
trans-CCd
trans-CC
cis-CC
(1a)
(1a)
(1b)
(1b)
(1c)
(1c)
(1c)
(1d)
(1e)
(1f)
(1g)
(1g)
(1h)
(1h)
(1i)
Dec
Bu
Dec
Bu
Dec
Bu
MeOEt
Dec
Dec
Dec
Dec
Bu
Dec
Bu
Dec
Dec
Dec
19.0
7.3
4.3
4.0
13.3
7.3
6.2
1.0
15.9
9.5
8.1
11.5
8.1
7.3
2.3
1.7
2.0
2.8 (1.7)
3.2 (1.3)
1.8 (1.4)
1.6 (1.2)
3.2 (1.3)
2.6 (1.3)
2.2 (1.4)
cis-CC
trans-CC
trans-CC
trans-CC
cis-CC
p-Ph-Ph
p-Ph-Ph
p-MeO-Ph
p-MeO-Ph
p-MeO-Ph
p-MeO-Ph
cyclohexyl
octyl
2.8 (1.6)
2.5 (1.6)
3.3 (1.9)
3.0 (1.9)
2.4 (1.7)
3.0 (1.5)
(1j)
(1k)
1-pentylhexyl
1-pentylhexyl
a The mixture of 1 and 2 in the solvent (CDCB, CHC, and mesitylene) in a molar ratio of 1:1:30 was heated at 130 °C for 48 h. b Determined
by 1H-NMR (400 MHz). c CDCB (c): cholesteryl 2,4-dichlorobenzoate (cholesteric); CHC (i): cholesteryl hydrocinnamate (isotropic). d CC:
4-cyclohexylcyclohexyl.
Table 3. Isomer Ratios from Thermal Cycloadditions of 1 to 2 in Smectic (BPCD) and Isotropic Solvents (CBPB)a
fumarates (1)
syn(3)/anti(4)b
BPCD(s)c
anthracenes (2)
R1
R2
R3
CBPB(i)d
cholesteryl
trans-CCe
[trans-CC
trans-CC
cis-CC
cis-CC
trans-CC
trans-CC
trans-CC
trans-CC
trans-CC
trans-CC
cis-CC
cis-CC
p-Ph-Ph
(1a)
(1c)
(1c)
(1c)
(1d)
(1d)
(1f)
(1l)
Dec
Dec
Dec
Bu
Dec
Bu
16.9
15.1
24.0
6.3
1.0
1.0
2.2
1.8
2.4]f
1.8
1.0
1.0
1.8
1.8
Dec
Dec
7.5
5.7
c-C6H11C3H6
1
a The reaction was performed in a molar ratio of 1:2:BPCD or CBPB of 1:1:30 at 150 °C for 48 h. b Determined by H-NMR (400 MHz).
c BPCD (s): bis(p-pentyloxyphenyl) trans-1,4-cyclohexanedicarboxylate. d CBPB (i): trans-1,4-cyclohexylene bis(p-pentyloxybenzoate). e CC:
4-cyclohexylcyclohexyl. f Performed at 140 °C.
Table 4. Isomer Ratios from Thermal Cycloaddition of
Bis(trans-4-cyclohexylcyclohexyl) Fumarate (1c) to
differences of the solvation enthalpy and entropy of the transition
complexes leading to syn- and anti-cycloadducts in the liquid
crystalline solvents. Clearly, more studies will be required in
order to develop a complete understanding of the nature of liquid
crystal control of thermochemical reactions.21
2,6-Bis(decyloxy)anthracene (2) in Choleteric, Smectic and Isotropic
Solvents as a Function of Temperaturea
syn(3)/anti(4)b
solvent (phase)
reaction
temp (°C)
CDCB(c)c
CHC(i)d
BPCD(s)e
CBPB(i)f
Experimental Section
130
140
150
160
170
180
13.3
10.1
7.4
3.2
2.8
2.5
2.4
General Methods. Melting points and phase-transition temperatures
were determined on a Yanaco micro melting point apparatus equipped
with a polarizing microscope and/or RICO-differential scanning
calorimeter (DSC) and are corrected. 1H NMR spectra were recorded
on JNX-GX400(400M Hz) in CDCl3 with TMS as an internal standard.
High resolution mass spectra (HRMS) were determined on a JEOL
JMS-DX303HF high resolution mass spectrometer. Thermochemical
reactions were carried out in an insulated silicon oil bath which was
regulated at constant temperature (1.0 °C by mercury thermoregulator
and transistor relay.
24.0
15.1
9.3
2.4
2.4
2.3
2.3
4.6
4.7
2.6
2.2
a The mixture of 1c and 2 in the solvent in a molar ratio of 1:1:30
was heated for 48 h. b Determined by H-NMR (400 MHz). c CDCB
1
(c): cholesteryl 2,4-dichlorobenzoate (cholesteric). d CHC (i): choles-
teryl hydrocinnamate (isotropic). e BPCD (s): bis(p-pentyloxyphenyl)
trans-1,4-cyclohexanedicarboxylate. f CBPB (i): trans-1,4-cyclohexy-
lene bis(p-pentyloxybenzoate).
Cholesteryl 2,4-dichlorobenzoate (CDCB) and cholesteryl hydro-
cinnamate (CHC) were purchased from Aldrich and Tokyo Kasei and
were purified by recrystallization from hexane and CH2Cl2.
DSC: 1H NMR δ 6.97 (4H, ddd, J ) 9.2, 2.2, 3.3 Hz), 6.86 (4H, ddd,
J ) 9.2, 2.2, 3.3 Hz), 3.92 (4H, t, J ) 6.6 Hz), 2.50-2.63 (2H, m),
2.17-2.35 (4H, m), 1.71-1.84 (4H, m), 1.55-1.70 (4H, m), 1.26-
1.50 (8H, m), 0.93 (6H, t, J ) 6.9 Hz); HRMS (FAB) Calcd for
C30H40O6: 496.2825. Found: 496.2811. Anal. Calcd for C30H40O6:
C, 72.55; H, 8.12. Found: C, 72.53; H, 8.10.
Bis(4-pentyloxyphenyl)
trans-1,4-Cyclohexanedicarboxylate
(BPCD). To a solution of trans-1,4-cyclohexanedicarbonyl chloride
(5.1 g, 30 mmol) in THF (150 mL) were added 4-pentyloxyphenol
(10.8 g, 60 mmol), triethylamine (6.1 g, 60 mmol), and 4-dimethyl-
aminopyridine (1.1 g, 9 mmol), and the mixture was stirred at 50 °C
for 8 h. Evaporation of the solvent followed by chromatography on
silica gel (CH2Cl2-hexane ) 8:1) gave the smectogen as colorless
crystals (12.8 g, 89%), which exhibited smectic temperature range of
101 f SmB f 105 f SmA f 173 f N f 193 °C as determined by
trans-1,4-Cyclohexylene Bis(4-pentyloxybenzoate) (CBPB).
A
mixture of 4-pentyloxybenzoyl chloride (23 mmol) prepared in situ,
trans-1,4-cyclohexanediol (1.3 g, 11.3 mmol), and 4-dimethylaminopy-
ridine (0.14 g, 1.1 mmol) in dry pyridine (40 mL) was stirred at 80 °C
for 10 h to give the smectogen as colorless crystals (5.3 g, 94%), which
(21) Dondoni, A.; Medici, A.; Colonna, S.; Gottarelli, G.; Samori, B.
Mol. Cryst. Liq. Cryst. 1979, 55, 47.

Liquid Crystal Control of Thermal Reactions
J. Am. Chem. Soc., Vol. 118, No. 23, 1996 5351
Table 5. Activation Parameters for Diels-Alder Reaction of
Bis(trans-4-cyclohexylcyclohexyl) Fumarate (1c) with
2,6-Bis(decyloxy)anthracene (2) in Liquid Crystalline and Isotropic
Solvents
trans-4-Cyclohexylcyclohexyl p-Phenylphenyl Fumarate (1f).
Yield: 79.5%; mp 171 °C (from hexane-CCl4); H NMR δ 7.19-
1
7.62 (9H, m), 7.02 (2H, s), 4.79 (1H, m), 2.07 (2H, d, J ) 11.4 Hz),
1.56-1.82 (6H, m) 1.35-1.43 (2H, m), 0.92-1.26 (8H, m). Anal.
Calcd for C28H32O4: C, 77.75; H, 7.46. Found: C, 77.88; H, 7.40.
Cholesteryl p-Methoxyphenyl Fumarate (1 g). Yield: 78.2%; mp
129 f C f 240 °C (from hexane-CCl4); [R]26D -11.3° (c 1.0, CHCl
3). 1H NMR δ 7.05 (2H, dm, J ) 10.3 Hz), 7.02(2H, s), 6.90 (2H,
dm, J ) 10.3 Hz), 5.40-5.43 (1H, m), 4.71-4.79 (1H, m), 3.80 (3H,
s), 0.68-2.4 (43H, m). Anal. Calcd for C38H54O5: C, 79.59; H, 9.52.
Found: C, 79.83; H, 9.68.
trans-4-Cyclohexylcyclohexyl p-Methoxyphenyl Fumarate (1h).
Yield: 60.8%; mp 107 °C (from hexane-CCl4); 1H NMR δ 7.05 (2H,
dd, J ) 8.1, 2.2 Hz), 7.014(1H, s), 7.008(1H, s), 6.91 (2H, dd, J )
8.1, 2.2 Hz), 4.66-4.82 (1H, m), 3.81 (3H, s), 2.02-2.08 (2H, m),
1.57-1.82 (7H, m), 1.32-1.41 (2H, m), 1.07-1.25 (7H, m), 0.94-
1.01 (2H, m). Anal. Calcd for C23H30O5: C, 71.42; H, 7.76. Found:
C, 71.18; H, 7.79.
∆∆Hq
syn-anti
(kcal/mol)
medium
phase
∆∆Sqsyn-anti (eu)
CDCBa
CHCb
cholesteric
isotropic
smectic
-26 ( 1
-4 ( 1
-38 ( 2
-6 ( 1
-13 ( 1
-3 ( 1
-19 ( 1
-3 ( 1
BPCDc
CBPBd
isotropic
a CDCB: cholesteryl 2,4-dichlorobenzoate. b CHC: cholesteryl hy-
drocinnamate. c BPCD: bis(p-pentyloxyphenyl) trans-1,4-cyclohex-
anedicarboxylate. d CBPB: trans-1,4-cyclohexylene bis(p-pentyloxy-
benzoate).
showed smectic temperature range of 99 f SmB f 123 f SmA f
124 f N f 143 °C as determined by DSC: 1H NMR δ 7.99 (4H,
ddd, J ) 8.8, 1.8, 2.9 Hz), 6.92 (4H, ddd, J ) 8.8, 1.8, 2.9 Hz), 5.01-
5.22 (2H, m), 4.01 (4H, t, J ) 6.6 Hz), 2.13-2.15 (4H, m), 1.66-1.86
(8H, m), 1.33-1.48 (8H, m), 0.94 (6H, t, J ) 6.9 Hz); HRMS (FAB)
Calcd for C30H40O6: 496.2825. Found: 496.2788. Anal. Calcd for
C30H40O6: C, 72.55; H, 8.12. Found: C, 72.54; H, 8.05.
Fumaric Acid Esters (1). A series of unsymmetrical and sym-
metrical esters were prepared from the corresponding fumaric acid
monoester and fumaryl dichoride, respectively, by standard procedures
and typical compounds are given as follows.
Dicyclohexyl Fumarate (1i). Yield: 89.5%; mp 37 °C (from
hexane); 1H NMR δ 6.82 (2H, s), 4.72-4.88 (2H, m), 1.24-1.89 (20H,
m). Anal. Calcd for C16H24O4: C, 68.54; H, 8.65. Found: C, 68.33;
H, 8.61.
1
Dioctyl Fumarate (1j). Yield: 75.0%; H NMR δ 6.82 (2H, s),
4.17 (4H, t, J ) 6.7 Hz), 0.87-1.76(30H, m); HRMS (EI) Calcd for
C20H36O4: 340.2614. Found: 340.2610.
Bis(1-pentylhexyl) Fumarate (1k). Yield: 68.3%; 1H NMR δ 6.72
(2H, s), 4.88-5.03 (2H, m), 0.78-1.79(44H, m); HRMS (CI) Calcd
for C26H48O4: 424.3552. Found: 424.3548.
trans-4-Cyclohexylcyclohexyl (Cyclohexylpropyl) Fumarate (1l).
Yield: 70.8%; mp 55 °C (from EtOH); 1H NMR δ 6.82 (2H, s), 4.72-
4.88 (2H, m), 4.18 (2H, t, J ) 3.3 Hz), 2.23-2.28 (2H, m), 1.65-1.82
(14H, m), 1.36-1.42 (2H, m), 1.06-1.25 (13H, m), 0.86-0.99 (4H,
m). Anal. Calcd for C25H40O4: C, 74.22; H, 9.97. Found: C, 73.97;
H, 10.12.
2,6-Dialkoxyanthracenes (2). Compounds (2) were obtained by
alkylation of 2,6-dihydroxyanthracene (mp 297 °C, 78%)19 prepared
by reacting anthraflavic acid with an excess of the corresponding alkyl
bromide (8.0 equiv) in the presence of Cs2CO3 (3.0 equiv) in boiling
acetone for 10 h.
2,6-Dibutoxyanthracene. Yield: 81.0%; mp 202 °C (from CCl4);
1H NMR δ 8.15 (2H, s), 7.80 (2H, d, J ) 9.9 Hz), 7.14 (2H, d, J ) 2.2
Hz), 7.13 (2H, dd, J ) 2.2, 9.9 Hz), 4.09 (4H, t, J ) 6.6 Hz), 1.84
(4H, tt, J ) 6.6, 7.7 Hz), 1.55 (4H, tt, J ) 7.3, 7.7 Hz), 1.01 (6H, t, J
) 7.3 Hz); HRMS (EI) calcd for C22H26O2: 322.1933. Found:
322.1915. Anal. Calcd for C22H26O2: C, 81.95; H, 8.18. Found: C,
82.23; H, 7.90.
2,6-Bis(decyloxy)anthracene. Yield: 75.3%; mp 141 °C (from
hexane); 1H NMR δ 8.16 (2H, s), 7.82 (2H, d, J ) 8.8 Hz), 7.15 (2H,
d, J ) 2.6 Hz), 7.14 (2H, dd, J ) 2.6, 8.8 Hz), 4.09 (4H, t, J ) 6.6
Hz), 1.87 (4H, tt, J ) 6.6, 7.0 Hz), 1.28-1.57 (28H, m), 0.89 (6H, t,
J ) 7.0 Hz); HRMS (EI) calcd for C22H26O2: 490.3811. Found:
490.3821. Anal. Calcd for C22H26O2:C, 83.21; H, 10.27. Found: C,
83.00; H, 10.52.
2,6-Bis(methoxyethoxy)anthracene. Yield: 63.4%; mp 195 °C
(from hexane); 1H NMR δ 8.17 (2H, s), 7.83 (2H, d, J ) 9.1 Hz), 7.20
(2H, dd, J ) 2.2, 9.1 Hz), 7.16 (2H, d, J ) 2.2 Hz), 4.26 (4H, dd, J )
4.7, 5.6 Hz), 3.84 (4H, dd, J ) 4.7, 5.6 Hz), 3.49 (6H, s); HRMS (EI)
calcd for C20H22O4: 326.1518. Found: 326.1491. Anal. Calcd for
C20H22O4: C, 73.59; H, 6.79. Found: C, 73.32; H, 6.70.
Cycloaddition in Liquid Crystalline Solvents. General Proce-
dure. A degassed mixture of 2,6-dialkoxyanthracene (0.3 mmol) and
the fumarate (0.3 mmol) in cholesteric (CDCB) or smectic (CBPB)
solvent (9 mmol) was stirred under argon gas at 130 or 150 °C for 48
h, retaining the liquid crystalline phases during the period of reaction.
A large portion of the liquid crystalline solvents were removed from
the reaction mixture by chromatography on silica gel with CH2Cl2-
hexane (1:2) as eluent, and the cycloadducts were obtained as a
diastereomeric mixture in 60-70% yields.
Monocholesteryl Fumarate. The mixture of cholesterol (50 g,
129.3 mmol) and sodium hydride (3.1 g) in dioxane (300 mL) was
treated with fumaryl chroride (19.8 g, 129.3 mmol) at 80 °C for 10 h.
Hydrolysis (H2O) followed by chromatography on silica gel gave the
liquid crystalline monoester as colorless crystals (36.2 g, 57.7%), mp
207 f C f 254 °C (from hexane-CH2Cl2): [R]27 -19.6° (c 1.0,
D
CHCl3); 1H NMR δ 10.5 (1H, br), 6.93 (1H, d, J ) 5.8 Hz), 6.83 (1H,
d, J ) 5.8 Hz), 5.40-5.41 (1H, m), 4.69-4.77 (1H, m), 0.68-2.39
(44H, m). Anal. Calcd for C31H48O4: C, 76.86; H, 9.92. Found: C,
76.92; H, 10.08.
Mono-trans-4-cyclohexylcyclohexyl Fumarate. Analogous treat-
ment fumaryl dichloride with trans-4-cyclohexylcyclohexanol (mp 174
°C) which was purely isolated from commercial material by chroma-
tography on silica gel (Kiesel gel 60 (70-230 mesh, Merch)) gave the
monoester as colorless crystals (1.62 g, 76.2%): mp 174 °C (from
1
hexane); H NMR δ 8.35 (1H, br), 6.90 (2H, dd, J ) 13.2, 12.6 Hz),
4.67-4.82 (1H, m), 2.01-2.05 (2H, m), 1.63-1.81 (7H, m), 1.32-
1.41 (2H, m), 1.06-1.25 (7H, m), 0.91-0.99 (2H, m). Anal. Calcd
for C16H24O4: C, 68.55; H, 8.63. Found: C, 68.51; H, 8.70.
Cholesteryl trans-4-Cyclohexylcyclohexyl Fumarate (1a). Yield:
67.2%; mp 185 f Cf 258 °C (from hexane); [R]27 -6.24° (c 1.0,
D
1
CHCl ); H NMR δ 7.26 (2H, s), 6.81 (2H, s), 5.39 (1H, d, J ) 3.7
3
Hz), 4.69-4.77 (2H, m), 0.68-2.37 (61H, m). Anal. Calcd for
C43H68O4: C, 79.58; H, 10.56. Found: C, 79.81; H, 10.81.
Cholesteryl cis-4-Cyclohexylcyclohexyl Fumarate (1b). Yield:
1
58.0%; mp 107 °C (from hexane); [R]27 -10.2° (c 1.0, CHCl ); H
D
3
NMR δ 6.83 (2H, d, J ) 5.1 Hz), 5.40 (1H, d, J ) 3.7 Hz), 5.08-5.13
(1H, m), 4.71-4.74 (1H, m), 2.38 (2H, d, J ) 7.3 Hz), 0.86-2.03
(60H, m), 0.68 (3H, m). Anal. Calcd for C43H68O4: C, 79.58; H, 10.56.
Found: C, 79.79; H, 10.73.
Bis(trans-4-cyclohexylcyclohexyl) Fumarate (1c). Yield: 97.8%;
1
mp 170 °C (from hexane-CH2Cl2); H NMR δ 6.81 (2H, s), 4.72-
4.77 (2H, m), 2.01-2.05 (2H, m), 1.59-1.80 (14H, m), 0.95-1.35
(22H, m). Anal. Calcd for C28H44O4: C, 75.62; H, 9.99. Found: C,
75.34; H, 10.13.
Bis(cis-4-cyclohexylcyclohexyl) Fumarate (1d). Yield: 92.9%; mp
1
104 °C (from hexane-CH2Cl2); H NMR δ 6.84 (2H, s), 5.09-5.13
(2H, m), 1.90-1.94 (2H, m), 1.50-1.74 (14H, m), 1.31-1.41 (4H,
m), 1.08-1.26(10H, m), 0.95-0.99(4H, m). Anal. Calcd for
C28H44O4: C, 75.62; H, 9.99. Found: C, 75.35; H, 10.21.
Cholesteryl p-Phenylphenyl Fumarate (1e). Yield: 70.7%; mp
1
174 f C f 269 °C (from CCl4); [R]25 -15.3° (c 1.0, CHCl ); H
D
3
NMR δ 7.56-7.61 (4H, m), 7.42-7.45 (2H, m), 7.33-7.45 (1H, m),
7.20-7.25 (2H, m), 7.06 (2H, s), 5.41-5.42 (1H, m), 4.75-4.78 (1H,
m), 0.68-2.41 (43H, m). Anal. Calcd for C43H56O4: C, 81.13; H,
8.81. Found: C, 81.02; H, 8.95.
The syn/anti-isomer ratios were obtained on the basis of the resolved
peaks of the aromatic protons in the 1H NMR spectra of the
cycloadducts. This ratio was further confirmed by saponification of
the cycloadducts with KOH (at 80 °C for 4 h in EtOH) to the

5352 J. Am. Chem. Soc., Vol. 118, No. 23, 1996
Kansui et al.
dicarboxylic acids. Diasteroselectivity was further measured using on
a LiCrosorb Si60 Column (1.0% ethyl acetate/hexane). Clear-cut
separation of syn- and anti-cycloadducts was performed by careful
chromatography on silica gel. Typical cycloadducts are given below.
Bis(trans-4-cyclohexylcyclohexyl) 2,6-Bis(decyloxy)-9,10-dihydro-
9,10-ethanoanthracene-11,12-dicarboxylates. syn-Adduct: mp 125
anti-Adduct: mp 137 °C; 1H NMR δ 7.03-7.09 (2H, m), 6.90 (2H,
J ) 1.8 Hz), 6.55-6.62 (2H, m), 5.32 (1H, d, J ) 5.5 Hz), 4.55-4.60
(2H, m), 4.47-4.53 (2H, m), 3.85-3.88 (2H, m), 3.37-3.41 (2H, m),
0.68-2.36 (101H, m). Anal. Calcd for C77H118O6: C, 81.14; H, 10.44,
Found: C, 81.23; H, 10.54.
2,6-Bis(decyloxy)-9,10-dihydro-9,10-ethanoanthracene-11,12-di-
carboxylic Acid. syn-Adduct: 1H NMR δ 7.14 (2H, d, J ) 8.1 Hz),
6.84 (2H, d, J ) 2.2 Hz), 6.60 (2H, dd, J ) 2.2, 8.1 Hz), 4.30 (2H, s),
3.88 (4H, t, J ) 7.0 Hz), 3.31 (2H, s), 1.72 (4H, t, J ) 7.0 Hz), 1.18-
1.52 (28H, m), 0.88 (6H, t, J ) 7.0 Hz).
1
°C; H NMR δ 7.19 (2H, d, J ) 8.1 Hz), 6.76 (2H, d, J ) 2.2 Hz),
6.55 (2H, dd, J ) 8.1, 2.2 Hz), 4.52-4.61 (2H, m), 4.41-4.58 (2H,
m), 3.88 (2H, t, J ) 12.5 Hz), 3.86 (2H, t, J ) 12.6 Hz), 3.35-3.38
(2H, m), 0.82-2.20 (78H, m). Anal. Calcd for C62H94O6: C, 79.61;
H, 10.13, Found: C, 79.39; H, 10.11.
anti-Adduct: 1H NMR δ 7.17 (2H, d, J ) 8.0 Hz), 6.84 (2H, d, J
) 2.2 Hz), 6.56 (2H, dd, J ) 2.2, 8.0 Hz), 4.30 (2H, s), 3.88 (4H, t,
J ) 7.0 Hz), 3.31 (2H, s), 1.72 (4H, t, J ) 7.0 Hz), 1.18-1.52 (28H,
m), 0.88 (6H, t, J ) 7.0 Hz).
1
anti-Adduct: mp 121 °C; H NMR δ 7.05 (2H, d, J ) 8.1 Hz),
6.89 (2H, d, J ) 2.2 Hz), 6.58 (2H, dd, J ) 8.1, 2.2 Hz), 4.52-4.61
(2H, m), 4.41-4.58 (2H, m), 3.88 (2H, t, J ) 12.5 Hz), 3.86 (2H, t, J
) 12.6 Hz), 3.35-3.38 (2H, m), 0.82-2.20(78H, m). Anal. Calcd
for C62H94O6: C, 79.61; H, 10.13, Found: C, 79.37; H, 10.24.
Cholesteryl (trans-4-Cyclohexylcyclohexyl) 2,6-Bis(decyloxy)-
9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylates.
syn-Adduct: mp 140 °C; 1H NMR δ 7.19 (2H, d, J ) 8.1 Hz), 6.74-
6.79 (2H, m), 6.55-6.62 (2H, m), 5.32 (1H, d, J ) 5.5 Hz), 4.55-
4.60 (2H, m), 4.47-4.53 (2H, m), 3.85-3.88 (2H, m), 3.37-3.41 (2H,
m), 0.68-2.36 (101H, m). Anal. Calcd for C77H118O6: C, 81.14; H,
10.44, Found: C, 81.37; H, 10.71.
Supporting Information Available: Table 1s of chemical
shifts assignable to Ha (Hd), Hb (He), and Hc (Hf) protons for
1
all the cycloadducts described here and H NMR spectra of
typical syn- and anti-cycloadducts (3 and 4) (R1 ) R2 ) trans-
CC, R3 ) decyl) (2 pages). See any current masthead page for
ordering information.
JA960282W