Synthesis of a novel tweezers-type host aiming at chiral discrimination by circular dichroism spectroscopy

Article abstract of DOI:10.1039/a909468g

In order to develop a methodology for chiral discrimination by utilizing complexation-induced circular dichroism (ICD) in host-guest systems, the novel tweezers-type host 1 was synthesized. From UV-VIS and fluorescence emission studies, it was confirmed t

Full text of DOI:10.1039/a909468g

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Synthesis of a novel tweezers-type host aiming at chiral
discrimination by circular dichroism spectroscopy†
Shigeyuki Yagi,* Hirokazu Kitayama and Toru Takagishi*
1
Department of Applied Materials Science, College of Engineering,
Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
Received (in Cambridge, UK) 30th November 1999, Accepted 3rd February 2000
In order to develop a methodology for chiral discrimination by utilizing complexation-induced circular dichroism
(ICD) in host–guest systems, the novel tweezers-type host 1 was synthesized. From UV-VIS and fluorescence
emission studies, it was confirmed that the host 1 formed a 1:1 complex with optically active N,NЈ-dimethyl-
trans-1,2-diaminocyclohexane 16, and the CD spectrum was induced as the concentration of the complex
increased. The sign of the Cotton effect induced by (S,S)-16 was opposite to that induced by (R,R)-16, indicating
that enantioselective formation of the atropisomer of 1 upon complexation leads to determination of the chirality
of the guest by CD. On the other hand, the ICD of 1 upon complexation with the chiral monoamine 17 implied
that the axial chirality of 1 was not induced until the host complexed two molecules of 17.
as a target guest, because it is a simple, C2 symmetric mole-
Introduction
cule suitable for preliminary investigation of the chiral
discrimination property of the host 1. In addition, 1,2-
diaminocyclohexane derivatives are widely used as chiral
auxiliaries in asymmetric synthesis12 and as building
blocks of the chiral host13 for enantioselective molecular
recognition.
The read-out of chemical information by synthetic host
molecules is one of the final goals in molecular recognition
chemistry.1 In particular, discrimination of chirality is very
important for the analytical application to pharmacology and
chemical industries,2–8 because almost all the biologically
important molecules possess one or more stereogenic centers in
their skeletons, for example amino acids and carbohydrates,
and because so many chiral ligands have been used in asym-
metric syntheses of drugs and natural products.9 In analyses
of chirality of molecules with their absorption in the near-UV
and/or visible regions, circular dichroism (CD) spectroscopy is
often a powerful tool to obtain structural information such as
absolute configurations of optically active compounds as
demonstrated by Nakanishi and Harada.10 Even when guest
molecules do not possess a chromophore, utilization of
complexation-induced CD (ICD) in chromogenic hosts makes
detection of chirality of guests possible.4–8
In this regard, we designed the novel tweezers-type
diarylbutadiyne host 1.11 As shown in Fig. 1, the host 1 exists
in the racemic state of two atropisomers, (R)-1 and (S)-1.
These isomers interconvert in the absence of guest mole-
cules due to the free rotation along the diyne axis. The axial
chirality is expected to be induced by complexation with
chiral guests through diastereomeric host–guest interactions.
In particular difunctionalized molecules, which bind comple-
mentarily to the cleft formed by the recognition sites (–CONH2)
in 1 through hydrogen bonds, are good candidates for the
guest. Here we report the synthesis of host 1 and chiral dis-
crimination by the CD spectroscopic technique. We selected
opticallyactiveN,NЈ-dimethyl-trans-1,2-diaminocyclohexane16
Results and discussion
The synthesis of host 1 is described in Scheme 1. The synthetic
strategy is as follows: first, the butadiyne unit and pyreno side
arms are independently prepared, and then, these are united to
afford the precursor of the host, 14, which is converted into 1 by
hydrolysis followed by amidation. The pyreno side arms are
necessary to effectively induce the axial chirality of the host
through the steric interaction between two pyrene rings. In
addition, they should serve as fluorescent indicators to detect
the host–guest complexation behavior and to monitor the
complexation-induced conformational change of the host by
the excimer formation.14 Thus, the combination of UV-VIS,
fluorescence emission and CD spectroscopies should make
analysis of the chiral discrimination mechanism in the 1–guest
system more precise. The octyl groups in the pyrene moieties
were introduced to increase solubility in the solvent employed
here.
Construction of the diyne unit began with 2-amino-5-
methylbenzoic acid, which was esterified with butan-1-ol (to
give compound 3), followed by bromination to afford the
compound 4. Diazotization followed by iodination by the
Sandmeyer reaction with KI yielded the benzoate 5.15
A
masked acetylene was introduced by the Pd-catalyzed cross-
coupling reaction16 with 3-methylbut-1-yn-3-ol to afford
compound 6 which was converted into the ethynylbenzoate 7
by demasking with NaH.17 The Glaser-type oxidative coup-
ling of the compound 7 afforded the diyne unit 8.18 The total
yield from 2-amino-5-methylbenzoic acid to the diyne 8 was
32%.
The precursor of the side arm units 13 was prepared in 5
steps from 1,6-dibromopyrene. Introduction of an octynyl
group by the Pd-catalyzed cross-coupling reaction followed by
hydrogenation afforded 1-bromo-6-(1-octyl)pyrene 10, which
was converted to the ethynylpyrene 12 by a similar conversion
† 1H NMR spectra for compounds 3, 4, 5, 7 and 13 are available as
supplementary data from BLDSC (SUPPL. NO. 57693, pp. 6) or the
RSC Library. See Instructions for Authors available via the RSC web
page (http://www.rsc.org/authors).
DOI: 10.1039/a909468g
J. Chem. Soc., Perkin Trans. 1, 2000, 925–932
This journal is © The Royal Society of Chemistry 2000
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Fig. 1 The structure of host 1 and its atropisomers. The absolute configuration, (R) or (S), is described based on chirality of the diyne skeleton.
Scheme 1 Reagents and conditions: (a) butan-1-ol, cat. H2SO4, reflux, 13 h, 3 (87%); (b) Br2, CCl4, rt, 3 h, 4 (97%); (c) NaNO2, HCl, H2O below 5 ЊC,
1 h, then KI, rt, 30 min, 5 (71%); (d) 3-methylbut-1-yn-3-ol, PdCl2(PPh3)2, CuI, NEt3, reflux, 15 h, 6 (79%); (e) NaH, toluene, reflux, 40 min, 7 (80%);
(f) Cu(OAc)2, CH3CN, 60 ЊC, 2 h, 8 (84%); (g) oct-1-yne, PdCl2(PPh3)2, CuI, morpholine, 100 ЊC, 10 h, 9 (58%); (h) H2, Pd–C, AcOEt, rt, 21 h, 10
(94%); (i) 3-methylbut-1-yn-3-ol, PdCl2(PPh3)2, CuI, morpholine, 100 ЊC, 14 h, 11 (75%); (j) NaH, toluene, reflux, 40 min 12 (95%); (k) n-BuLi in
hexane, dry THF, 0 ЊC, and then, n-Bu3SnCl, rt, 12 h, 13, not purified; (l) PdCl2(PPh3)2, toluene, 14 (55%); (m) NaOH, THF–EtOH–H2O, rt, 10 h, 15
(98%); (n) NH3aq, EDCؒHCl, THF–H2O, rt, 15 h, 1 (63%); (o) 1-butylamine, 2-chloro-1-methylpyridinium iodide, NEt3, CH2Cl2, reflux, 24 h, 2 (27%).
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Fig. 3 Fluorescence emission spectra of 1 (broken line, a) and 1ؒ(S,S)-
16 (solid line, b) in CHCl3 at 298 K. [1] = 6.0 × 10Ϫ6 M. [(S,S)-16] =
3.0 × 10Ϫ2 M. The excitation wavelength is 381 nm.
298 K. The absorption from 330 to 470 nm, which is due to the
π–π* transition of the π conjugation system from the pyrene to
the benzamide moiety, successively changed as the concentration
of the guest increased, showing isosbestic points at 357, 375, and
432 nm. The spectral changes exhibited a saturation behavior as
shown in Fig. 2b, and the Job’s plot for the 1ؒ(S,S)-16 system
indicated that the stoichiometry of the complexation is 1:1.
The binding constant of 1ؒ(S,S)-16 complex was obtained as
Kabs = 4750 MϪ1 (sd 470) by computer-assisted least-squares
analysis of the absorbance changes as a function of guest
concentrations. On the other hand, no spectral change was
observed when (S,S)-16 was added to a solution of the host
2, indicating that the bulkiness of the butyl groups in 2 sig-
nificantly hinders the complexation with the guest.
Fig. 2 (a) UV-VIS spectra of host 1 in the presence of varying concen-
trations of (S,S)-16 in CHCl3 at 298 K. [1] = 3.01 × 10Ϫ5 M. [(S,S)-
16] = 0, 1.51 × 10Ϫ4, 3.75 × 10Ϫ4, 6.69 × 10Ϫ4, 1.03 × 10Ϫ3, 1.48 × 10Ϫ3
,
2.88 × 10Ϫ3, 5.01 × 10Ϫ3, 7.79 × 10Ϫ3, 1.12 × 10Ϫ2, 1.52 × 10Ϫ2 M. (b)
The plot of UV-VIS titration for complexation of 1 and (S,S)-16
monitored at 400 nm. The solid line is a theoretical curve generated by
the least-squares calculation.
The complexation behavior was also monitored by fluor-
escence emission spectroscopy. The emission spectra of the host
1 and 1ؒ(S,S)-16 complex are shown in Fig. 3. The fluorescence
excitation spectrum at 492 nm corresponded well with the
absorption spectrum, indicating that the fluorescence emission
originates from the chromophoric system containing the pyrene
moiety. The original spectrum of the host 1 (a) successively
changed to the spectrum (b) upon addition of the guest. The
analysis of the increases of the emission intensity upon addi-
tion of the guest afforded the binding constant Kem = 5860 MϪ1
(sd 840), which is similar to the value of Kabs although the
standard deviation is somewhat large. This result indicates that
the changes of the emission spectra also originate from the
host–guest complexation. The fluorescence spectroscopic study
affords more information about the conformational change of
the host 1. The decay of the fluorescence emission of 1 at 492
nm exhibited a biphasic profile. The lifetimes of the emission
are 3.9 ns ( 0.1 ns, 34.6%) and 12.0 ns ( 0.1 ns, 65.4%), each of
which should originate from either the pyrene monomer emis-
sion or the excimer emission. As the excimer emission is usually
observed at the longer wavelength than the monomer emission,
the fluorescence emission of 1 at 492 nm is assigned to the
excimer. Thus, the increase of the emission intensity at 492 nm
as seen in Fig. 3 indicates the complexation-induced conform-
ational change of the host 1, where the two pyrene moieties
come in contact so as to form the excimer.
used for compound 5 into 7. Reaction of the acetylide of 12
with n-Bu3SnCl afforded compound 13.‡
The diyne 8 and the pyreno side arms 13, were connected by
the Stille-type coupling reaction employing PdCl2(PPh3)2 as a
catalyst19 to yield the precursor of the host, 14, in 55% yield.
Subsequent hydrolysis afforded the dicarboxylic acid 15 in 98%
yield, and the amidation employing NH3 and 1-ethyl-3-(3-
dimethylaminopropyl)carbodiimide (EDC) finally afforded
host 1 in 63% yield from 15. The host 2, which possesses butyl
groups on the amide nitrogens, was also prepared in 27% yield
by condensation of 15 with 1-butylamine, where 2-chloro-1-
methylpyridinium iodide was employed as a carboxy group
activating reagent. The structures of 1 and 2 were confirmed by
1H NMR, IR and FAB mass spectra and elemental analysis.
The preliminary Corey–Pauling–Koltun (CPK) modeling
study for complexation of the host 1 with the diaminocyclo-
hexane 16 indicated that the cleft formed by two amide groups
of 1 was complementary towards the two amino groups of 16
through hydrogen bonds between the amide protons of 1 and
the amino nitrogens of 16. Unfortunately, monitoring the com-
plexation behavior of the host 1 with the guest by 1H NMR was
not successful: the amide protons were not observed probably
due to rapid proton exchanges, and complexation-induced
chemical shift changes for the other protons of 1 on complex-
ation with 16 were less than 0.1 ppm. Therefore, the complex-
ation was monitored using UV-VIS and fluorescence emission
spectroscopies. In Fig. 2 are shown UV-VIS spectral changes
of the host 1 upon addition of the guest (S,S)-16 in CHCl3 at
The chiral discrimination property of the host 1 for the chiral
guest 16 was investigated by CD spectra. In Fig. 4 are shown
CD spectra of 1ؒ(S,S)-16 and 1ؒ(R,R)-16 complexes in CHCl3
at 298 K. The alternative signs of the Cotton effect were
observed for each complex in the host’s absorption band,
although the CD spectrum of the host 1 was silent. The spectra
of the two complexes are symmetrical along the horizontal axis.
In a CD titration experiment, the intensity successively
increased as the concentration of the guest increased: the CD
emergence paralleled the increase of the concentration of the
‡ Compound 13 could not be purified due to low stability. Production
of 13 was confirmed by 1H NMR of the crude sample, where the signal
of the acetylenic proton of 12 disappeared and generation of new
resonance peaks assigned to the butyl groups of the n-Bu3Sn group was
observed.
J. Chem. Soc., Perkin Trans. 1, 2000, 925–932
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Fig. 6 CD spectral changes at 440 nm in the presence of varying
concentrations of 17 in CHCl3 at 298 K. [1] = 3.0 × 10Ϫ5 M.
Fig. 4 Circular dichroism spectra of host 1 (4.0 × 10Ϫ5 M) in the
presence of (S,S)-16 (solid line, a) and (R,R)-16 (broken line, b) in
CHCl3 at 298 K. [16] = 4.0 × 10Ϫ2 M.
complex. Taking into consideration that the stoichiometry of
the complexation is 1:1 as confirmed in the UV-VIS study,
these results strongly indicate that the ICD was induced by the
enantioselective formation of the atropisomer of the host 1
complementary to the chirality of the guest.
observed in the 1ؒ16 system. As shown in Fig. 6, the ICD was
silent over the wide range of the guest concentration (up to ca.
0.1 M), whereas it was induced in the higher concentration of
the guest (>0.2 M). Taking into consideration that the increases
of the fluorescence emission intensity of the host 1 were
observed in the presence of the lower concentrations of 17
(<0.1 M, data not shown),§ one can see that the host 1 forms a
complex with one molecule of 17 and then with another
molecule of 17 to give a 1:2 complex. The CD titration profile
implies that cooperative chiral induction of the host by stepwise
binding of the guests occurs. A possible mechanism is proposed
in Fig. 7a. In this mechanism, the guest binds to one recogni-
tion site, where the aryl group with the other recognition site
could freely rotate along the diyne axis, leading to interconver-
Determination of the absolute configuration of 1 upon
complexation with 16 was examined by the CD exciton chir-
ality method.10 In the case of the 1ؒ(S,S)-16 complex, the
positive first Cotton effect and the negative second one were
observed in the low energy absorption of 1 (see Fig. 2), indi-
cating the emergence of positive chirality. Supposing that the
electric transition moment of the low energy absorption of 1
is in a similar direction to that of the pyrene’s transverse axis
transition, the manner of the exciton coupling can be illus-
trated as shown in Fig. 5. Thus, the (S)-form of 1 affords
positive chirality and the (R)-form affords negative chirality.
Therefore, the absolute configuration of 1 in the 1ؒ(S,S)-16
complex can be assigned to the (S)-form. In a similar way, it
can be determined that (R)-1 is induced by complexation with
(R,R)-16.
As a referential study, chiral discrimination of the mono-
amine 17 by the host 1 was also examined. The ICD profile
upon complexation with guest 17 was quite different from that
§ The fluorescence emission spectral changes of 1 on complexation with
17 exhibited a complicated behavior, so that binding constants for both
of 1:1 and 1:2 complexation could not be obtained.
Fig. 5 The directions of the low energy transitions of the pyrene moieties in 1. The octyl groups in the pyrene rings are omitted for clarity. The
exciton coupling manner in each atropisomer is also shown at the bottom as a projection from the wide arrow in the upper figure. The signs of plus
and minus mean positive and negative chirality, respectively.
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Fig. 7 Proposed mechanisms for complexation of 1 (a) with monoamine 17 and (b) with 1,2-diamine 16.
sion between two atropisomers of 1. When the second guest
Experimental
1H and 13C NMR spectra were obtained at 270 and 67.8 MHz,
binds to the 1:1 complex to form the 1:2 complex, the
two guests behave as extrinsic chiral auxiliaries to induce axial
chirality of 1. On the other hand, the two amino groups in 16
would tightly fix the recognition sites of the host, i.e. prevent
the rotation of the diyne, leading to effective chiral induction of
the diyne skeleton of 1 (Fig. 7b).
1
respectively, on a JEOL JNM–GX spectrometer. In H NMR
measurements, TMS (0 ppm) was used as an internal standard,
and in 13C NMR the signal of 13CDCl3 (77.0 ppm) was
employed as an internal standard. IR spectra were taken
for KBr disks of solid samples and a CCl4 solution of liquid
samples, and recorded on a Horiba FT-200 spectrometer. Mass
spectra were obtained by EI and FAB techniques on Shimadzu
RF-5000 and Finnigan mat TSQ-70 spectrometers, respectively.
For FAB-mass spectra, 3-nitrobenzyl alcohol was used as a
matrix. Elemental analyses were carried out using a Yanaco
CHN-CORDER MT3 recorder. UV-VIS absorption and fluor-
escence emission spectra were recorded on a Jasco V-550 spec-
trometer and Shimadzu RF-5000 spectrometer, respectively.
Fluorescent lifetimes of the emission of 1 were obtained by
time-correlated, single-photon counting methodology using a
Horiba NAES-550 nanosecond fluorophotometer. The sample
concentration was 6 × 10Ϫ6 M and the excitation wavelength
Conclusion
In conclusion, we achieved the synthesis of the novel tweezers-
type host molecule 1. It was confirmed by UV-VIS, fluorescence
emission, and CD spectroscopies that the host 1 is able to effect-
ively bind the optically active 1,2-diamine such as the guest 16
in its cleft and discriminate the absolute configuration of
the guest through the complexation-induced enantioselective
formation of the atropisomer. The result obtained here
implies that wider utilization of the host–guest chemistry
towards chemosensory systems would develop a novel analytical
methodology.
J. Chem. Soc., Perkin Trans. 1, 2000, 925–932
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was 381 nm. CD spectra were obtained on a Jasco J-720W
spectropolarimeter.
J = 3.2 Hz, 1H); 13C NMR (CCl4) δ 13.72, 19.26, 20.53, 30.54,
65.99, 96.31, 128.64, 132.13, 135.17, 139.78, 140.89, 167.69;
IR (KBr) 2961, 2929, 1717, 1361, 1219 cmϪ1; EI MS m/z 340
([M Ϫ C4H8]ϩ, 100%), 342 ([M Ϫ C4H8]ϩ ϩ 2, 99), 396 (Mϩ,
25), 398 (Mϩ ϩ 2, 23).
2-Amino-5-methylbenzoic acid and (S)-1-phenylethylamine
17 were purchased from Nacalai Tesque, Inc. 1,6-Dibromo-
pyrene20 and optically active 1621 were prepared according to
the reported procedures. Chloroform used in spectroscopic
measurements was of spectroscopic grade and purchased from
Aldrich, and contained amylene as a stabilizer. 1H NMR spectra
for compounds 3, 4, 5, 7 and 13 are available as supplementary
data.†
Butyl 3-bromo-2-(3-hydroxy-3-methylbut-1-ynyl)-5-methyl-
benzoate, 6
A mixture of 5 (8.21 g, 20.7 mmol), PdCl2(PPh3)2 (295 mg,
0.420 mmol) and CuI (40.0 mg, 0.210 mmol) in NEt3 (70 mL)
was stirred for 10 min at 0 ЊC under an Ar atmosphere, and to
the mixture was added 3-methylbut-1-yn-3-ol (1.77 g, 21.0
mmol). The reaction mixture was stirred at reflux for 15 h. After
cooling, the solvent was removed on a rotary evaporator. The
residue was purified by silica gel column chromatography
(CH2Cl2–hexane, 2:1,v/v, as eluent) to afford 6 as a colorless
Butyl 2-amino-5-methylbenzoate, 3
To a stirred mixture of 2-amino-5-methyl benzoic acid (7.47 g,
49.4 mmol) and butan-1-ol (120 mL) was added dropwise
sulfuric acid (4 mL) at 0 ЊC, and the mixture was heated at
reflux for 13 h with removal of water. After cooling, the solvent
was removed by distillation, and the residue was dissolved
in CH2Cl2. The organic was washed with saturated aqueous
NaHCO3, water (×3), and saturated brine, and dried over
anhydrous MgSO4. The solvent was removed on a rotary evap-
orator, and purification of the residue by silica gel column
chromatography (CH2Cl2–hexane, 1:2, v/v, as eluent) afforded 3
1
syrup (5.80 g, 16.4 mmol, 79%): H NMR (CDCl3) δ 0.95 (t,
J = 7.3 Hz, 3H), 1.45 (sext, J = 7.3 Hz, 2H), 1.65 (s, 6H), 1.73
(quint, J = 7.3 Hz, 2H), 2.34 (s, 3H), 3.13 (br s), 4.31 (t, J = 7.3
Hz, 2H), 7.57 (m, 2H); 13C NMR (CDCl3) δ 13.68, 19.19, 20.91,
30.62, 31.10, 65.47, 65.57, 79.39, 103.59, 121.58, 127.81, 129.45,
134.26, 136.02, 138.97, 165.79; IR (CCl4) 3500, 2978, 2962,
1718, 1362, 1218 cmϪ1; FAB MS m/z 335 ([M Ϫ OH]ϩ), 337
([M Ϫ OH]ϩ ϩ 2). Anal. Calcd for C17H21O3Br: C, 57.79; H,
5.99. Found: C, 57.63; H, 5.92%.
1
as a colorless oil (8.95 g, 43.2 mmol, 87%): H NMR (CDCl3)
δ 0.98 (t, J = 7.3 Hz, 3H), 1.47 (sext, J = 7.3 Hz, 2H), 1.75
(quint, J = 7.3 Hz, 2H), 2.23 (s, 3H), 4.27 (t, J = 7.3 Hz, 2H),
5.55 (br s, 2H), 6.58 (d, J = 7.9 Hz, 1H), 7.08 (dd, J = 1.8 and 7.9
Hz, 1H), 7.65 (d, J = 1.8 Hz, 1H); 13C NMR (CDCl3) δ 13.78,
19.34, 20.29, 30.86, 64.15, 111.05, 116.85, 125.36, 130.80,
135.09, 148.29, 168.26; IR (CCl4) 3510, 3381, 2962, 1693, 1289,
1251, 1203 cmϪ1; EI MS m/z 133 ([M Ϫ C4H10O]ϩ, 100%), 207
(Mϩ, 21).
Butyl 3-bromo-2-ethynyl-5-methylbenzoate, 7
A mixture of 6 (5.57 g, 15.8 mmol) and NaH (63.0 mg, 60 wt%
oil dispersion, 1.58 mmol) in dry toluene (50 mL) was heated at
reflux with stirring for 40 min under an Ar atmosphere. After
cooling, the solvent was removed on a rotary evaporator. The
residue was dissolved in CH2Cl2, washed with saturated aque-
ous NaHCO3, water (×3), and saturated brine, and dried over
anhydrous MgSO4. After removal of the solvent, purification of
the residue by silica gel column chromatography (CHCl3–
hexane, 1:1, v/v, as eluent) afforded 7 as a colorless oil (3.73 g,
12.6 mmol, 80%): 1H NMR (CDCl3) δ 0.97 (t, J = 7.3 Hz, 3H),
1.47 (sext, J = 7.3 Hz, 2H), 1.75 (quint, J = 7.3 Hz, 2H), 2.36 (s,
3H), 3.63 (s, 1H), 4.34 (t, J = 7.3 Hz, 2H), 7.60 (m, 2H); 13C
NMR (CDCl3) δ 13.64, 19.20, 20.93, 30.52, 65.49, 80.06, 86.63,
120.71, 127.91, 129.47, 135.37, 136.06, 139.78, 165.69; IR
(CCl4) 2953, 1717, 1507, 1437, 1361, 1219 cmϪ1; EI MS m/z 238
([M Ϫ C4H8]ϩ, 100%), 240 ([M Ϫ C4H8]ϩ ϩ 2, 98), 294 (Mϩ, 5),
296 (Mϩ ϩ 2, 5).
Butyl 2-amino-3-bromo-5-methylbenzoate, 4
To a stirred solution of 3 (6.90 g, 33.3 mmol) in CCl4 (120 mL)
was added dropwise a solution of Br2 (5.32 g, 33.3 mmol) in
CCl4 (30 mL) over 2 h at Ϫ5 ЊC on an ice–salt bath. The mixture
was stirred at rt for 3 h, and then, the solvent was removed on a
rotary evaporator. The residue was dissolved in CH2Cl2, washed
with saturated aqueous NaHCO3, water (×3), and saturated
brine, and dried over anhydrous MgSO4. After removal of the
solvent, purification of the residue by silica gel column chrom-
atography (CH2Cl2–hexane, 1:3, v/v, as eluent) afforded 4 as a
colorless oil (9.20 g, 32.2 mmol, 97%): 1H NMR (CDCl3) δ 0.98
(t, J = 7.3 Hz, 3H), 1.48 (sext, J = 7.3 Hz, 2H), 1.75 (quint,
J = 7.3 Hz, 2H), 2.23 (s, 3H), 4.28 (t, J = 7.3 Hz, 2H), 5.51 (br s,
2H), 7.42 (d, J = 1.2 Hz, 1H), 7.65 (d, J = 1.2 Hz, 1H); 13C
NMR (CDCl3) δ 13.78, 19.32, 20.04, 30.80, 64.64, 110.65,
112.08, 125.77, 130.64, 137.94, 145.35, 167.67; IR (CCl4) 3500,
2961, 2929, 1717, 1361, 1219 cmϪ1; EI MS m/z 211 ([M Ϫ
C4H10O]ϩ, 100%), 215 ([M Ϫ C4H10O]ϩ ϩ 2, 100), 285 (Mϩ, 27),
287 (Mϩ ϩ 2, 24).
1,4-Bis(1-bromo-3-n-butoxycarbonyl-5-methyl-2-phenyl)-
butadiyne 8
A mixture of 6 (3.68 g, 12.5 mmol) and Cu(OAc)2ؒH2O (9.68 g,
48.5 mmol) in acetonitrile (80 mL) was stirred for 2 h at 60 ЊC.
After cooling, the solvent was removed on a rotary evaporator.
The residue was dispersed in CH2Cl2 (100 mL), and the
insoluble matter was removed by filtration. The filtrate was
washed with water (×2) and dried over anhydrous MgSO4. The
solvent was removed by evaporation, and purification of the
residue by silica gel column chromatography (CH2Cl2–hexane,
1:1, v/v, as eluent) afforded 8 as a white solid (3.08 g, 5.24
Butyl 3-bromo-2-iodo-5-methylbenzoate, 5
To a stirred mixture of 4 (10.5 g, 36.7 mmol), concentrated HCl
(70 mL) and water (70 mL) was added dropwise a solution of
NaNO2 (2.76 g, 40.0 mmol) in water (40 mL) over 1 h below
5 ЊC in an ice–salt bath. Then a solution of KI (60.9 g, 367
mmol) in water (50 mL) was added, and the mixture was stirred
at rt for an additional 30 min. After neutralization with satur-
ated aqueous NaHCO3, the organic mixture was extracted with
CH2Cl2 (×3), and the organic phases were combined and dried
over anhydrous MgSO4. After removal of the solvent on a
rotary evaporator, purification by silica gel column chromato-
graphy (hexane as eluent) afforded 5 as a colorless oil (10.3 g,
25.9 mmol, 71%): 1H NMR (CDCl3) δ 0.97 (t, J = 7.3 Hz, 3H),
1.48 (sext, J = 7.3 Hz, 2H), 1.76 (quint, J = 7.3 Hz, 2H), 2.30 (s,
3H), 4.34 (t, J = 7.3 Hz, 2H), 7.25 (d, J = 3.2 Hz, 1H), 7.57 (d,
1
mmol, 84%): mp 135–137 ЊC; H NMR (CDCl3) δ 0.95 (t,
J = 7.3 Hz, 6H), 1.51 (sext, J = 7.3 Hz, 4H), 1.81 (quint, J = 7.3
Hz, 4H), 2.39 (s, 6H), 4.36 (t, J = 7.3 Hz, 4H), 7.61 (d, J = 1.8
Hz, 2H), 7.70 (d, J = 1.8 Hz, 2H); 13C NMR (CDCl3) δ 13.80,
19.36, 21.14, 30.60, 65.85, 80.87, 82.85, 120.79, 128.60, 130.19,
135.59, 136.40, 140.26, 165.63; IR (KBr) 2955, 2930, 2870,
1727, 1594, 1449, 1288, 1268, 1200, 1103 cmϪ1; FAB MS m/z
587 ([M ϩ H]ϩ), 589 ([M ϩ H]ϩ ϩ 2), 591 ([M ϩ H]ϩ ϩ 4).
Anal. Calcd for C28H28O4Br2: C, 57.15; H, 4.80. Found: C,
57.52; H, 4.86%.
930
J. Chem. Soc., Perkin Trans. 1, 2000, 925–932

View Article Online
1-Bromo-6-(oct-1-ynyl)pyrene, 9
mixture of 1,6-dibromopyrene (5.16 g, 14.3 mmol),
washed with saturated aqueous NaHCO3, water (×3), and sat-
urated brine, and dried over anhydrous MgSO4. After filtration,
the solvent was removed on a rotary evaporator. Purification of
the residue by silica gel column chromatography (hexane, as
eluent) afforded 12 as a pale yellow solid (332 mg, 0.981 mmol,
A
PdCl2(PPh3)2 (134 mg, 0.191 mmol) and CuI (18.2 mg, 0.0956
mmol) in morpholine (130 mL) was stirred for 10 min at 0 ЊC,
and then oct-1-yne (1.05 g, 9.55 mmol) was added. The mixture
was stirred for 10 h at 100 ЊC. After cooling, the solvent was
removed on a rotary evaporator, and the residue was purified by
silica gel column chromatography (hexane as eluent) to afford 9
1
95%): mp 85–87 ЊC; H NMR (CDCl3) δ 0.88 (t, J = 7.3 Hz,
3H), 1.28 (m, 8H), 1.48 (quint, J = 7.3 Hz, 2H), 1.85 (quint,
J = 7.3 Hz, 2H), 3.28 (t, J = 7.3 Hz, 2H), 3.61 (s, 1H), 7.89 (d,
J = 7.9 Hz, 1H), 8.04–8.16 (m, 5H), 8.31 (d, J = 9.2 Hz, 1H),
8.53 (d, J = 9.2 Hz, 1H); 13C NMR (CDCl3) δ 14.14, 22.71,
29.34, 29.59, 29.87, 31.93, 32.11, 33.71, 82.45, 116.21, 124.03,
124.39, 124.59, 124.68, 125.61, 126.88, 127.73, 128.72, 128.76,
129.55, 130.11, 131.47, 132.88, 138.32; IR (KBr) 2956, 2924,
2850, 1468, 1133 cmϪ1; FAB MS m/z 338 (Mϩ). Anal. Calcd for
C26H26: C, 92.26; H, 7.74. Found: C, 92.40; H, 7.81%.
1
as a yellow viscous syrup (2.16 g, 8.29 mmol, 58%): H NMR
(CDCl3) δ 0.95 (t, J = 7.3 Hz, 3H), 1.39 (m, 4H), 1.60 (quint,
J = 7.3 Hz, 2H), 1.77 (quint, J = 7.3 Hz, 2H), 2.65 (t, J = 7.3 Hz,
2H), 7.90–8.05 (m, 5H), 8.17 (d, J = 7.9 Hz, 1H), 8.33 (d, J = 9.2
Hz, 1H), 8.51 (d, J = 9.2 Hz, 1H); 13C NMR (CDCl3) δ 14.14,
20.00, 22.67, 28.82, 28.96, 31.47, 79.48, 97.06, 119.80, 120.21,
123.83, 124.94, 125.71, 125.97, 126.17, 127.55, 128.74, 129.73,
130.17, 130.25, 130.34, 130.52, 130.62, 131.79; IR (KBr) 2929,
2313, 1361, 1218 cmϪ1; EI MS m/z 237 ([M Ϫ C5H12Br]ϩ,
100%), 388 (Mϩ, 16), 390 (Mϩ ϩ 2, 16). Anal. Calcd for
C24H21Br: C, 74.02; H, 5.44. Found: C, 73.78; H, 5.52%.
1-(2-Tributylstannylethyn-1-yl)-6-octylpyrene, 13 and 1,4-
bis[1-butoxycarbonyl-5-methyl-3-(6-octylpyren-1-ylethynyl)-2-
phenyl]butadiyne, 14
To a stirred solution of 12 (873 mg, 2.58 mmol) in dry THF (15
mL) was added dropwise a hexane solution of n-BuLi (1.57 M,
1.97 mL, 3.09 mmol) at 0 ЊC under an Ar atmosphere. Then,
tributyltin chloride (924 mg, 2.84 mmol) was added, and the
mixture was stirred at rt for 12 h. The solvent was removed on a
rotary evaporator, and the residue was dissolved in ether. The
organic was washed with saturated KFaq (×3), water and satur-
ated brine, and then dried over anhydrous Na2SO4. The solvent
was removed on a rotary evaporator to afford a crude product
of 13 as a pale yellow solid (1.62 g, containing small amounts
of unreacted n-BuSnCl), which was used in the next step with-
out purification. A solution of the crude product of 13 (1.62 g)
in dry toluene (40 mL) was added into a mixture of 8 (450 mg,
0.765 mmol) and PdCl2(PPh3)2 (11.1 mg, 0.0158 mmol), and the
mixture was stirred at 50 ЊC for 24 h under an Ar atmosphere.
After cooling, the solvent was removed on a rotary evaporator
and the residue was dissolved in CH2Cl2. The organic was
washed with saturated KFaq (×3), water and saturated brine,
and then dried over anhydrous MgSO4. After evaporation,
purification by silica gel column chromatography (CH2Cl2–
hexane, 1:1, v/v, as eluent) followed by recrystallization from
benzene–hexane afforded 14 as a yellow crystal (467 mg, 0.423
1-Bromo-6-octylpyrene, 10
Compound 9 (1.53 g, 3.93 mmol) was hydrogenated on Pd–
carbon (153 mg, 5% Pd) in ethyl acetate (80 mL) over 21 h at rt.
The catalyst was removed by filtration, and the filtrate was
evaporated. The residue was purified by silica gel column
chromatography (hexane as eluent) to afford 10 as a pale yellow
solid (1.45 g, 3.69 mmol, 94%): mp 71–74 ЊC; 1H NMR (CDCl3)
δ 0.87 (t, J = 7.3 Hz, 3H), 1.28 (m, 8H), 1.48 (quint, J = 7.3 Hz,
2H), 1.82 (quint, J = 7.3 Hz, 2H), 3.33 (t, J = 7.3 Hz, 2H), 7.90
(d, J = 7.9 Hz, 2H), 7.99 (d, J = 7.9 Hz, 2H), 8.04 (d, J = 9.2 Hz,
2H), 8.12 (d, J = 9.2 Hz, 2H), 8.14 (d, J = 7.9 Hz, 1H), 8.20 (d,
J = 7.9 Hz, 2H), 8.29 (d, J = 9.2 Hz, 1H), 8.37 (d, J = 9.2 Hz,
1H); 13C NMR (CDCl3) δ 14.13, 22.71, 29.34, 29.57, 29.87,
31.93, 32.03, 33.77, 97.79, 99.25, 100.74, 102.82, 110.10, 123.87,
125.06, 125.16, 125.40, 126.82, 127.95, 129.20, 130.00, 131.73,
135.81, 138.32; IR (KBr) 2954, 2921, 2860, 1468, 1082 cmϪ1; EI
MS m/z 293 ([M Ϫ C7H15]ϩ, 100%), 295 ([M Ϫ C7H15]ϩ ϩ 2,
100), 392 (Mϩ, 36), 394 (Mϩ ϩ 2, 38). Anal. Calcd for C24H25Br:
C, 73.27; H, 6.40. Found: C, 73.21; H, 6.30%.
1-(3-Hydroxy-3-methylbut-1-ynyl)-6-octylpyrene, 11
1
mmol, 55% based on 8): mp 144–148 ЊC; H NMR (CDCl3)
A mixture of 10 (1.44 g, 3.66 mmol), PdCl2(PPh3)2 (77.1 mg,
0.110 mmol) and CuI (10.5 mg, 0.0551 mmol) in morpholine
(90 mL) was stirred for 10 min at 0 ЊC, and then 3-methylbut-1-
yn-3-ol (0.920 g, 11.0 mmol) was added. The mixture was
stirred at 100 ЊC for 14 h. After cooling, the solvent was
removed by evaporation, and the residue was purified by
silica gel column chromatography (CH2Cl2–hexane, 1:1, v/v, as
eluent). Further purification by recrystallization from hexane
afforded 11 as a yellow crystal (1.10 g, 2.75 mmol, 75%): mp
δ 0.87–0.99 (m, 12H), 1.31–1.57 (m, 24H), 1.78–1.90 (m, 8H),
2.52 (s, 6H), 3.25 (t, J = 7.3 Hz, 4H), 4.37 (t, J = 7.3 Hz, 4H),
7.35 (d, J = 7.9 Hz, 2H), 7.51–7.56 (m, 4H), 8.69–7.94 (m, 12H),
8.42 (d, J = 9.2 Hz, 2H); 13C NMR (CDCl3) δ 13.82, 14.16,
19.44, 21.40, 22.75, 29.44, 29.67, 29.99, 30.70, 31.99, 32.15,
33.67, 65.73, 82.12, 83.38, 92.90, 94.96, 97.06, 116.25, 121.22,
123.22, 123.64, 124.09, 124.61, 125.28, 126.45, 127.10, 128.31,
128.90, 129.14, 129.47, 129.79, 130.52, 130.86, 131.87, 134.50,
135.63, 137.35, 138.77, 166.16; IR (KBr) 2925, 2852, 2202,
1716, 1593, 1196 cmϪ1; FAB MS m/z 1103 ([M ϩ H]ϩ). Anal.
Calcd for C80H78O4: C, 87.08; H, 7.12. Found: C, 87.07; H,
7.04%.
1
106–107 ЊC; H NMR (CDCl3) δ 0.87 (t, J = 7.3 Hz, 3H), 1.27
(m, 8H), 1.46 (quint, J = 7.3 Hz, 2H), 1.79 (s, 6H), 1.82 (quint,
J = 7.3 Hz, 2H), 2.33 (br s, 1H), 3.28 (t, J = 7.3 Hz, 2H), 7.83 (d,
J = 7.9 Hz, 1H), 7.97–8.10 (m, 5H), 8.24 (d, J = 9.2 Hz, 1H),
8.41 (d, J = 9.2 Hz, 1H); 13C NMR (CDCl3) δ 14.14, 22.71,
29.34, 29.57, 29.89, 31.81, 31.93, 32.05, 33.69, 33.81, 66.09,
81.50, 99.33, 116.87, 124.03, 124.25, 124.39, 124.70, 124.80,
125.46, 126.88, 127.59, 128.50, 128.70, 129.57, 131.08, 132.26,
138.10; IR (KBr) 3389, 2935, 2923, 2853, 1558, 1467, 1260,
1150 cmϪ1; FAB MS m/z 397 ([M ϩ H]ϩ). Anal. Calcd for
C29H32O: C, 87.83; H, 8.13. Found: C, 87.77; H, 8.18%.
1,4-Bis[1-carboxy-5-methyl-3-(6-octylpyren-1-ylethynyl)-2-
phenyl]butadiyne, 15
To a stirred solution of 14 (84.0 mg, 0.0761 mmol) in THF (3.6
mL) was added NaOH (91.0 mg, 2.28 mmol) dissolved in
EtOH–H2O (2:1,v/v, 1.5 mL). The mixture was stirred at rt for
10 h. The solvent was removed by evaporation and the residue
was dissolved in water. The aqueous solution was acidified with
1 M HCl to pH 4 to afford a precipitate, which was collected by
filtration. The solid was dried in vacuo, washed with a small
amount of hexane and dried again in vacuo over silica gel
to afford 15 as a yellow solid (74.0 mg, 0.0746 mmol, 98%).
Compound 15 exhibited low solubility in any solvents, and the
structural confirmation was carried out by IR and FAB mass
spectra and elemental analysis: mp 190–193 ЊC; IR (KBr) 3103,
1-Ethynyl-6-octylpyrene, 12
A mixture of 11 (409 mg, 1.03 mmol) and NaH (8.12 mg,
60 wt% oil dispersion, 0.203 mmol) in dry toluene (40 mL) was
heated at reflux with stirring for 40 min under an Ar atmos-
phere. After cooling, the solvent was removed by evaporation,
and the residue was dissolved in ether, and the organic was
J. Chem. Soc., Perkin Trans. 1, 2000, 925–932
931

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A. J. M. Huxley, C. P. McCoy, J. T. Rademacher and T. E.
3039, 2923, 2852, 2170, 1697, 1593, 1464, 1439, 1257, 1200
cmϪ1; FAB MS m/z 990 (Mϩ). Anal. Calcd for C72H62O4: C,
87.24; H, 6.30. Found: C, 87.30; H, 6.54%.
Rice, Chem. Rev., 1997, 97, 1515; (d) Y. Kubo, Synlett, 1999, 161;
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2 T. Nishi, A. Ikega, T. Matsuda and S. Shinkai, J. Chem. Soc., Chem.
Commun., 1991, 339.
3 Y. Kubo, S. Maeda, S. Tokita and M. Kubo, Nature (London), 1996,
382, 522.
1,4-Bis[1-aminocarbonyl-5-methyl-3-(6-octylpyren-1-ylethynyl)-
2-phenyl]butadiyne, 1
A mixture of 15 (100 mg, 0.101 mmol), EDCؒHCl (143 mg, 1.01
mmol) and NH3aq (30 wt%, 15 mL) in THF–H2O (2:1, v/v, 45
mL) was stirred at rt for 15 h. The solvent was removed by
evaporation and the residue was purified by silica gel column
chromatography (CHCl3–MeOH, 5:4, v/v as eluent). The
product was dissolved in CHCl3 (5 mL) and the insoluble resi-
due was removed by filtration. The filtrate was evaporated, and
the residue was dissolved in a small amount of CHCl3. The
solution was poured into MeOH (20 mL) to afford a precipi-
tate, which was washed with hexane and dried in vacuo to yield
1 as a yellow solid (63.4 mg, 0.0641 mmol, 63%): mp 209–
213 ЊC; 1H NMR (270 MHz, CDCl3–CD3OD, 5:1, v/v) δ 0.93 (t,
J = 7.3 Hz, 6H), 1.23–1.58 (m, 20H), 1.89 (m, 4H), 2.50 (s, 6H),
3.14 (t, J = 7.3 Hz, 4H), 6.92 (d, J = 7.9 Hz, 2H), 7.08 (d, J = 7.9
Hz, 2H), 7.29 (d, J = 7.9 Hz, 2H), 7.41–7.90 (m, 12H), 8.38 (m,
2H); IR (KBr) 3466, 2924, 2850, 2170, 1626, 1603, 1568, 1385
cmϪ1; FAB MS m/z 989 ([M ϩ H]ϩ). Anal. Calcd for C72H64-
N2O2: C, 87.41; H, 6.52; N, 2.83. Found: C, 87.53; H, 6.61; N,
2.68%.
4 (a) Y. Aoyama, Y. Tanaka, H. Toi and H. Ogoshi, J. Am. Chem. Soc.,
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Chem., Int. Ed., 1998, 37, 2096.
8 X. Huang, B. H. Rickman, B. Borhan, N. Berova and K. Nakanishi,
J. Am. Chem. Soc., 1998, 120, 6185.
9 J. Seyden-Penne, Chiral Auxiliaries and Ligands in Asymmetric
Synthesis, Wiley, Toronto, 1995.
10 (a) K. Nakanishi and N. Harada, Circular Dichroic Spectroscopy-
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11 For examples of tweezers-type hosts so far reported, see (a) C.-W.
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12 (a) K. Onuma, T. Ito and A. Nakamura, Chem. Lett., 1979, 905;
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13 S. S. Yoon and W. C. Still, J. Am. Chem. Soc., 1993, 115, 823.
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16 J. Tsuji, Palladium Reagents and Catalysts. Innovation in Organic
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1,4-Bis[1-(butylaminocarbonyl)-5-methyl-3-(6-octylpyren-1-
ylethynyl)2-phenyl]butadiyne, 2
A mixture of 15 (71.0 mg, 0.0716 mmol), n-butylamine (52.3
mg, 0.716 mmol), 2-chloro-1-methylpyridinium iodide (40.4
mg, 0.169 mmol) and NEt3 (0.02 mL) in dry CH2Cl2 (8 mL) was
stirred at reflux for 24 h. After cooling, the solvent was removed
by evaporation and the residue was dissolved in CH2Cl2. The
organic was washed with saturated NaHCO3, water and satur-
ated brine and dried over anhydrous MgSO4. The solvent was
removed and the residue was purified by preparative thin-layer
chromatography (silica gel, CH2Cl2–hexane, 5:3, v/v as eluent)
to afford 2 as a yellow solid (21.0 mg, 0.0191 mmol, 27%): mp
155–157 ЊC; 1H NMR (270 MHz, CDCl3) δ 0.88 (t, J = 7.3 Hz,
6H), 0.98 (t, J = 7.3 Hz, 6H), 1.28–1.53 (m, 24H), 1.73 (m, 4H),
1.87 (m, 4H), 2.56 (s, 6H), 3.35 (t, J = 7.3 Hz, 4H), 3.76 (t,
J = 7.3 Hz, 4H), 7.63 (s, 2H), 7.76 (s, 2H), 7.92 (d, J = 7.9 Hz,
2H), 8.09 (d, J = 9.2 Hz, 2H), 8.14 (d, J = 9.2 Hz, 2H), 8.19 (d,
J = 7.9 Hz, 2H), 8.26–8.32 (m, 4H), 8.36 (d, J = 9.2 Hz, 2H),
8.98 (d, J = 9.2 Hz, 2H); IR (KBr) 3423, 2962, 2925, 2852, 2214,
1765, 1701, 1404, 1261, 1095, 1024 cmϪ1; FAB MS m/z 1101
([M ϩ H]ϩ). Anal. Calcd for C80H80N2O2: C, 87.23; H, 7.32; N,
2.54. Found: C, 87.30; H, 7.32; N, 2.34%.
Acknowledgements
This work was financially supported by the Shorai Foundation
for Science and Technology.
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J. Chem. Soc., Perkin Trans. 1, 2000, 925–932