Do dibenzo[22-30]crown ethers bind secondary ammonium ions to form pseudorotaxanes?

Article abstract of DOI:10.1246/bcsj.80.1377

In this study, we synthesized dibenzo[22-30]crown ethers and dumbbell-like secondary ammonium salts having stoppers of varying bulk. These crown ethers formed pseudorotaxanes with the ammonium ions in solution and in the gas phase, as evidenced using NMR spectroscopy and MS/MS spectrometry, respectively. The association constants in solution were obtained through regulation of the association and dissociation rates by varying the nature of the stopper groups of the dumbbell-like ammonium ions. The [25]- and [26]crown ether/ isopropylphenyl group, the [27]- and [30]crown ether/tert-butylphenyl group, and the [22]- and [23]crown ether/furyl group were matched pairs. ¹ HNMR spectra of mixtures (CDCI₃/CD₃CN) of the crown ethers and their matched ammonium salts indicated the presence of three sets of signals in solution: those of the crown ether, the ammonium salt, and their pseudorotaxane. Integration of pertinent signals allowed the association constants of pseudorotaxanes to be determined readily. Among the [22-30]crown ethers, the highest value of the association constant was that for the [24]crown ether/dibenzylammoniumion system; the [25-30]crown ether/ammonium ion systems exhibited moderate values of their association constants [K_exp - 35-114 M^-1 when using (ArCH₂)₂NH ₂⁺PF₆^- as the ammonium salt at 27 °C; K_exp = 21 M^-1 when using (ArCH₂) ₂NH₂⁺TsO^- at 27 °C]. The [22]- and [23]crown ethers interacted weakly [K_exp = 6-14 M^-1 when using (ArCH₂)₂NH₂⁺TsO ^- at27°C].

Full text of DOI:10.1246/bcsj.80.1377

Ó 2007 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 80, No. 7, 1377–1382 (2007) 1377
Do Dibenzo[22–30]crown Ethers Bind Secondary
Ammonium Ions to Form Pseudorotaxanes?
ꢀ1
Yuji Tokunaga, Megumi Yoshioka,1 Tatsuya Nakamura,1 Tatsuhiro Goda,1
Ryuji Nakata,2 Suzuka Kakuchi,1 and Youji Shimomura1
1Department of Materials Science and Engineering, Faculty of Engineering, University of Fukui, Fukui 910-8507
2Natural Science Education Laboratory, Faculty of Education and Regional Studies, University of Fukui,
Fukui 910-8507
Received October 10, 2006; E-mail: tokunaga@matse.fukui-u.ac.jp
In this study, we synthesized dibenzo[22–30]crown ethers and dumbbell-like secondary ammonium salts having
stoppers of varying bulk. These crown ethers formed pseudorotaxanes with the ammonium ions in solution and
in the gas phase, as evidenced using NMR spectroscopy and MS/MS spectrometry, respectively. The association con-
stants in solution were obtained through regulation of the association and dissociation rates by varying the nature of
the stopper groups of the dumbbell-like ammonium ions. The [25]- and [26]crown ether/isopropylphenyl group, the
[27]- and [30]crown ether/tert-butylphenyl group, and the [22]- and [23]crown ether/furyl group were matched pairs.
1H NMR spectra of mixtures (CDCl3/CD3CN) of the crown ethers and their matched ammonium salts indicated
the presence of three sets of signals in solution: those of the crown ether, the ammonium salt, and their pseudorotaxane.
Integration of pertinent signals allowed the association constants of pseudorotaxanes to be determined readily. Among
the [22–30]crown ethers, the highest value of the association constant was that for the [24]crown ether/dibenzylammo-
nium ion system; the [25–30]crown ether/ammonium ion systems exhibited moderate values of their association
ꢁ
constants [Kexp ¼ 35{114 Mꢁ1 when using (ArCH2)2NH2þPF6 as the ammonium salt at 27 ꢂC; Kexp ¼ 21 Mꢁ1 when
using (ArCH2)2NH2þTsOꢁ at 27 ꢂC]. The [22]- and [23]crown ethers interacted weakly [Kexp ¼ 6{14 Mꢁ1 when using
(ArCH2)2NH2þTsOꢁ at 27 ꢂC].
Hydrogen bonding was first reported for guiding the self-
assembly of [2]pseudorotaxanes from dibenzo[24]crown-8
(DB24C8) and secondary ammonium ions.1 Since then, these
types of pseudorotaxane have garnered much attention because
of their unique structures and intriguing properties.2 Several
oligorotaxanes and polyrotaxanes3 and dendrimers of rotax-
anes4 have been synthesized using DB24C8/ammonium ion
systems. In addition, the hydrogen-bonding interactions be-
tween secondary ammonium ions and oligo(ethylene glycol)
moieties, which are small units of crown ethers have been uti-
lized to prepare a range of attractive supramolecular structures,
including a supramolecular cryptant5 based on a rotaxane, dou-
ble-stranded rotaxanes,6 an anion-assisted multi-stranded ro-
taxane,7 and a ring–ring pseudorotaxane.8 Furthermore, revers-
ible-recognition [i.e., threading oligo(ethylene glycol) deriva-
tives through a dicationic cyclophane]9 and pseudorotaxanes
formed from modified ammonium ions and crown ethers10 also
have been reported. Despite the well-established hydrogen
bonding that occurs between poly(ethylene glycol) units and
ammonium ions, fundamental crown ethers that possess small
or moderate ring sizes have not been examined sufficiently
or systematically for their ability to form such psudorotax-
anes,11,12 possibly because the synthesis of asymmetric crown
ethers and the measurement of their association constants are
somewhat complex. In contrast, [24]crown-8, which is readily
available, has a cavity size that is amenable to passage of
phenyl units positioned at the termini of common dumbbell-
like compounds, allowing analyses of the stabilities of their
pseudorotaxanes when using NMR spectroscopy; i.e., the
pseudorotaxane and the uncomplexed species are detectable
independently in the NMR spectra of mixtures of the axle-
and wheel-like components.1 The association constants are ob-
tainable readily from integration of the signals of each species,
with the chemical shifts of the signals providing information
regarding the structure of the complex.1,12,13
In this study, we investigated how changing the cavity size
of the crown ether, as opposed to the size of the stopper units
of the guest, alters the association constants for pseudorotax-
ane formation. Furthermore, we determined suitable ‘‘matched
pairs’’ between the cavity size of the host and the stopper size
of the dumbbell-like guest that allowed us to analyze these
pseudorotaxanes’ thermodynamic stabilities using NMR spec-
troscopy (Fig. 1).
Results and Discussion
Synthesis of Crown Ethers. The crown ethers chosen for
this investigation included DB24C8-o 1 as a standard, mono-
meta-fused DB25C8-m 2,14 mono-para-fused DB26C8-p 3,
and DB25C8-o 4 and DB26C8-o 5, which possess one and
two propylene glycol units, respectively. Two large macro-
cycles—DB27C9-o 614 and DB30C10-o 7,15 which contain 27-
and 30-membered rings, respectively—and three small crown
ethers—DB21C7-o 8,15,16 DB22C7-o 9, and DB23C7-o 10—
were also investigated (Fig. 2). The syntheses of crown ethers
Published on the web July 11, 2007; doi:10.1246/bcsj.80.1377

1378 Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007)
Dibenzo[22–30]crown form Pseudorotaxanes
OH
k
O
O
O
O
O
O
O
2
OTs
O
O
slow
or
fast?
OH
DB26C8-p
3
Cs2CO3
OTs
2
O
O
O
m
+
N
11
H2
+
+
OTs
TsO
3
O
N
H2
3
O
O
O
13a
regulation of
stopper size
DB25C8-o
Cs2CO3
4
OH
HO
12
Fig. 1. Illustration of pseudorotaxane formation.
O
O
O
OBn
K2CO3
OH
3
O
O
1)
O
O
O
O
O
13a
OR
OR
2) H2, 10% Pd-C
14a: R = Bn
14b: R = H
O
O
1: DB24C8-o
2: DB25C8-m
3: DB26C8-p
13a, Cs2CO3
DB26C8-o
m
O
O
O
O
5
O
O
O
OTs
TsO
n
O
O
O
2
13a: n = 3
13b: n = 4
DB22C7-o
O
O
9
n
4: m = 2, n = 1, DB25C8-o
5: m = 2, n = 2, DB26C8-o
Cs2CO3
DB23C7-o
OH
HO
10
15
O
O
O
m
O
O
O
O
Scheme 1.
achieved through cyclization reactions of 15 with the ditosy-
lates 13a and 13b, respectively.
O
Formation of Pseudorotaxanes. As an initial experiment,
we performed an NMR spectroscopic titration to monitor the
pseudorotaxane formed from DB25C8-m 2 and the dibenzyl-
ammonium salt 16PF6ꢁ. The rates of association and dissoci-
ation of the pseudorotaxane were fast on the NMR spectro-
scopic timescale at room temperature, as reported previously.17
The 1H NMR spectrum (CDCl3/CD3CN, 1:1) of a 1:1 mixture
of DB25C8-m 2 and 17PF6ꢁ (an ammonium salt that possesses
isopropylphenyl groups at its termini)12 provided evidence for
pseudorotaxane formation. New signals for the benzylic and
aromatic protons of the dumbbell component of the pseudo-
n
6: m = 2, n = 1, DB27C9-o
7: m = 2, n = 2, DB30C10-o
8: m = 1, n = 0, DB21C7-o
O
O
O
O
O
n
O
O
9: n = 3, DB22C7-o
10: n = 4, DB23C7-o
rotaxane 2 17 appeared at 4.37 ppm and at 7.08 and 7.23 ppm,
ꢃ
Fig. 2. Crown ether structures.
respectively. The six new signals at 3.46, 3.58, 3.65, 3.82,
3.93, and 4.19 ppm correspond to the resonances of the aliphat-
ic protons in the heterocyclic ring of the pseudorotaxane. Such
chemical shifting is typical for this type of pseudorotaxane
3–5, 9, and 10 are outlined in Scheme 1. DB26C8-p 3 and
DB25C8-o 4 were synthesized through cyclization reactions
of their two components (ditosylate 11 and hydroquinone for
DB26C8-p 3; diol 12 and ditosylate 13a for DB25C8-o 4). A
stepwise synthesis were undertaken for the construction of
crown ether 5: the reaction of 13a with two molar amounts
of benzyloxyphenol, followed by deprotection afforded the
corresponding bisphenol 14b, which was then alkylated again
with 13a. The syntheses of small crown ethers 9 and 10 were
(Fig. 3).12,17,18 In the same manner, the pseudorotaxanes 3 17
ꢃ
(crown ether: DB26C8-p) and 4 17 (crown ether: DB25C8-o)
were confirmed to exist at room temperature through the use of
1H NMR spectroscopic titration techniques.19
ꢃ
1
We did not observe any new signals in the H NMR spec-
trum of a mixture of DB26C8-o 5 and 17PF6ꢁ at room tempera-

Y. Tokunaga et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007) 1379
+
NH2
+
TsO-
Ha
NH2
O
Hj
Hj
O
X-
2
R
2
20TsO-
-
-
16PF6 : R = H, X = PF6
16TsO-: R = H, X = TsO-
O
-
-
-
17PF6-: R = i-Pr, X = PF6
Hb
Hc
18PF6 : R = t-Bu, X = PF6
H5
O
O
O
18TsO-: R = t-Bu, X = TsO-
H4
+
N
H3
Hd
He
O
H2
Hi
+
NH2
H2
O
O
-
Hf
PF6
2
H1
Hh
-
19PF6
Hg
ꢁ
Fig. 3. 1H NMR spectra (500 MHz, CDCl3–CD3CN (1:1)) of a) 17PF6ꢁ, b) 2, and c) a 1:1 mixture of 2 (10 mM) and 17PF6 (40 mM).
ture. In contrast, the ammonium salt 19PF6ꢁ, which is substi-
tuted with relatively bulkier 3,5-dimethylphenyl groups, pre-
0.18 nm
1
sented one set of pseudorotaxane signals in its H NMR spec-
H
H
trum when mixed with the crown ether 5 at room tempera-
ture.19 In the presence of the largeꢁr crown ether DB27C9-o 6,
the 1H NMR spectrum of 19PF6 displayed time-averaꢁged,
broad signals. Finally, we used the ammonium salt 18PF6 as
H
H
H
H
H
H
H
H
H
H
0.18 nm H
H
H
a dumbbell-like component to form the pseudorotaxanes 6 18
(crown ether: DB27C9-o) and 7 18 (crown ether: DB30C10-
ꢃ
0.52 nm
0.26 nm
ꢃ
o).19 In the 1H NMR spectrum of the mixture of 7 and 18PF6
,
ꢁ
the circumference of the thickest part of the
dumbbell-like axle
some of the signals broadened upon increasing the tempera-
ture, suggesting that the association and dissociation rates were
similar to the NMR timescale at temperatures higher than
room temperature.
total 1.75 nm
total 1.32 nm
Fig. 4. Structures and sizes of 3,5-dimethylphenyl and tert-
butylphenyl stoppers. The dimensions given for each stop-
per are those of measured between the centers of corre-
sponding hydrogen atoms.
Our results were surprising. Of the two stopper units of 18
and 19, the circumference of a tert-butyl stopper is smaller
than that of a 3,5-dimethylphenyl stopper (Fig. 4). In a simpli-

1380 Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007)
Dibenzo[22–30]crown form Pseudorotaxanes
fied view, one would expect the association and dissociation
processes of the ammonium ion 18 and crown ether 6 to be
kinetically faster than those of 19 and 6. In fact, it has been re-
ported that a 3,5-dimethylphenyl group is bulkier than a tert-
butylphenyl group for [24]crown ether-based rotaxane sys-
tems.20 We observed, however, that the rates of association
and dissociation of 18 and 6 were lower than those of 19 and
6. Thus, the relative stopper size is not solely responsible for
this behavior. In terms of the shapes of the stoppers, the tert-
butyl group is somewhat spherical and the 3,5-dimethylphenyl
group is relatively flat. The crown ether components of pseu-
dorotaxanes formed through hydrogen bonding with ammo-
nium ions are often elliptical. Thus, the relationship between
the shapes of the crown ether and the stopper units of the
thread-like ion is probably an important factor that regulates
the rates of association and dissociation.21
Next, we investigated whether the relatively smaller crown
ethers DB22C7-o 9 and DB23C7-o 10 were able to recognize
secondary ammonium ions to form pseudorotaxanes. The di-
furfurylammonium salt 20TsOꢁ was used as a dumbbell to de-
termine the appropriate ring size. The crown ethers 9 and 10
both recognized the ammonium ion 20 within their cavities.
Consequently, new signals that were attributable to the corre-
sponding pseudorotaxane did not appear in the NMR spectra of
a mixture of DB21C7-o 8 and 20TsOꢁ after 1 h at room tem-
perature. That finding is consistent with the previous report
that a minimum of 22 cyclic atoms is required for threading
of a polymethylene chain.22
1:1 complexes
[1 16]+, [7 16]+, and [1 19]+
+
[16]+ and [19]+
Precursor ions
Fragment ions
1:1 complexes
(Precursor ions)
Branching ratiosa
(%)
run
[1 16]+
[DB24C8-o (PhCH2)2NH2]+
1
2.5
[7 16]+
2
4.8
13
[DB30C10-o (PhCH2)2NH2]+
[1 19]+
3
[DB24C8-o (Me2C6H3CH2)2NH2]+
a [fragment ion]/[precursor ion]
Fig. 5. Branching ratios for 1:1 complexes of ammonium
ions and crown ethers.
Table 1. Association Constants between Crown Ethers and
Ammonium Ionsa)
b)
Run Crown ether
Ammonium
salt
Kexp
/Mꢁ1
ꢀG
/kJ molꢁ1
All of the crown ethers appeared to form 1:1 complexes
with the secondary ammonium ions in the gas phase, as dem-
onstrated using electrospray ionization (ESI) mass spectrome-
ꢁ
1
2
3
4
5
6
7
8
9
DB24C8-o 1
DB24C8-o 1
DB25C8-m 2
DB26C8-p 3
DB25C8-o 4
DB26C8-o 5
DB27C9-o 6
DB27C9-o 6
DB30C10-o 7
DB22C7-o 9
DB23C7-o 10
16 PF6
740 ꢅ 70 ꢁ16:5 ꢅ 0:3
16 TsOꢁ
65 ꢅ 2
57 ꢅ 8
35 ꢅ 4
94 ꢅ 8
4 ꢅ 1
ꢁ10:4 ꢅ 0:1
ꢁ10:1 ꢅ 0:4
ꢁ8:6 ꢅ 0:3
ꢁ11:3 ꢅ 0:2
ꢁ3:4 ꢅ 0:3
ꢁ
17 PF6ꢁ
try. In each case, peaks were observed for the crown ether
ꢃ
17 PF6ꢁ
17 PF6ꢁ
19 PF6ꢁ
18 PF6
Naþ adduct, the uncomplexed ammonium ion, and the 1:1
complex formed between the crown ether and the ammonium
ion. Furthermore, we performed ESI-MS/MS experiments to
compare the collision-induced dissociation (CID) mass spectra
of the 1:1 complexes 1 16, 7 16, and 1 19. The complexes
98 ꢅ 14 ꢁ11:6 ꢅ 0:2
18 TsOꢁ
21 ꢅ 1
ꢁ7:6 ꢅ 0:1
ꢁ
ꢃ ꢃ
ꢃ
18 PF6
127 ꢅ 33 ꢁ12:0 ꢅ 0:8
1 19 and 7 16 possessed pseudorotaxane structures in solu-
tion, with the formation of the pseudorotaxane 7 16 being ki-
10
11
20 TsOꢁ
20 TsOꢁ
6 ꢅ 0
ꢁ4:6 ꢅ 0:2
ꢃ
ꢃ
14 ꢅ 1
ꢁ6:6 ꢅ 0:2
ꢃ
netically rapid on the NMR timescale. In contrast, 1 and 19
formed a face-to-face complex in solution. The CID mass
spectra of the ½M ꢁ PF6ꢁꢄþ ions of the three complexes dis-
a) The association constants were obtained by the integrations
1
of pseudorotaxanes and free axles or crowns in the H NMR
spectra of mixtures of corresponding crowns (10 mM) and
ammonium salts (10 mM) at 27 ꢂC. b) Kexp = [pseudorotax-
ane]/[host]uc[guest]uc.
played abundant precursor ions peaks (m=z 646 for 1 16; m=z
ꢃ
734 for 7 16; m=z 702 for 1 19) and small fragment ion peaks
ꢃ
ꢃ
corresponding to the ½M ꢁ PF6ꢁ ꢁ crown etherꢄþ ions (m=z
198 for 16; m=z 254 for 19) and ½M ꢁ PF6ꢁ ꢁ crown ether ꢁ
Hꢄþ ions (m=z 253 for 19).19 Figure 5 presents a cartoon illus-
tration of the CID process and the branching ratios for disso-
ciation of the 1:1 complexes. These ratios indicate that the
constants are not exactly comparable because the counter
ions25 and the dumbbells’ termini26 were not identical; the na-
ture of the counter ion of the ammonium ions has a particularly
high influence on the association constant because of ion pair-
ing effects. To provide some meaningful data, all of the NMR
spectroscopic titrations were performed at the same concentra-
tions and using the ammoniumꢁsalts 16 and 18, which possess
two different counter ions (PF6 and TsOꢁ), as the dumbbell-
shaped components (Runs 1, 2, 7, and 8). The DB24C8/diben-
zylammonium ion system provided the highest association
constant (Runs 1 and 2). It is likely that the [24]crown ether
has a favorable size for hydrogen bonding with the ammonium
ion. In comparison, the association constants of [25]crown
ethers 2 and 4 were dramatically lower (Runs 3 and 5); their
gas-phase dissociation of the complex [1 19]þ was kinetically
ꢃ
faster than those of the [7 16]þ and [1 16]þ complexes; the
results suggest that the kinetic stabilities of the complexes
ꢃ
ꢃ
follow the order [1 16]þ > [7 16]þ > [1 19]þ.
Next, we calculated the association constants (Kexp
ꢃ
ꢃ
ꢃ
23,24
)
the pseudorotaxanes through integration of the signals of the
of
1
three species present in the H NMR spectra and from the ini-
tial concentrations of the dumbbell- and wheel-shaped compo-
nents (Table 1), i.e., when the complexed and uncomplexed
species were detectable in the NMR spectra. These association

Y. Tokunaga et al.
Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007) 1381
1H NMR (500 MHz, CDCl3) ꢁ 1.90 (quint, J ¼ 6:3 Hz, 2H), 3.66–
3.70 (m, 4H), 3.80–3.83 (m, 8H), 3.88–3.93 (m, 4H), 4.12–4.18
(m, 8H), 6.87–6.93 (m, 8H). 13C NMR (125 MHz, CDCl3) ꢁ 30.1,
68.3, 68.8, 69.3, 69.4, 69.8, 71.1, 114.2, 114.4, 121.4, 121.4,
148.9, 149.0. FAB-MS m=z: C25H34O8 462 [Mþ]. Found: C,
64.72; H, 7.55%. Calcd for C25H34O8: C, 64.92; H, 7.41%.
values were similar to (or less than) those of the [27]- and
[30]crown ethers 6 and 7 (Runs 7 and 9), the association con-
stants of which were almost identical, although the favorable
ring size is 24. Ethylene glycol moieties enhance complex for-
mation, compared with those of propylene and butylene glycol
units, because their oxygen atoms are positioned favorably for
hydrogen bonding. In contrast, the association constants of 9
and 10 are quite low. It is likely that the [22]- and [23]crown
ethers have cavities that are too small to accommodate second-
ary ammonium ions (Runs 8 and 9).
1,3-Bis[2-(2-benzyloxyphenoxy)ethoxy]propane (14a).
A
suspension of 2-benzyloxyphenol (3.47 g, 18.2 mmol), ditosylate
13a (3.92 g, 8.30 mmol), and potassium carbonate (5.72 g, 41.5
mmol) in DMF (36 mL) was heated at 90 ꢂC for 5 h. After DMF
was removed, to the residue was added ethyl acetate. The organic
mixture was washed with water and sat. NaCl, dried and evaporat-
ed. Chromatography of the residue on silica gel with ethyl ace-
tate–toluene (1:10) as eluent gave the ether 14a (3.18 g, 72%)
as a solid. IR ꢀmax (KBr) cmꢁ1 3064, 2943, 2889, 1508, 1220.
1H NMR (500 MHz, CDCl3) ꢁ 1.86 (quint, J ¼ 6:3 Hz, 2H), 3.58–
3.62 (m, 4H), 3.75–3.79 (m, 4H), 4.13–4.17 (m, 4H), 5.11 (s, 4H),
6.85–6.96 (m, 8H), 7.25–7.29 (m, 2H), 7.33–7.36 (m, 4H), 7.43–
7.45 (m, 4H). 13C NMR (125 MHz, CDCl3) ꢁ 30.1, 68.3, 68.9,
69.4, 71.4, 115.0, 115.6, 121.6, 121.8, 127.3, 127.7, 128.4, 137.5,
149.0, 149.4. HR-MS(FAB) m=z: Calct for C33H36O6: 528.2512.
Found: 528.2491. Found: C, 73.96; H, 6.85%. Calcd for C33-
Summary
1
Using H NMR spectroscopy and ESI-MS/MS techniques,
we have demonstrated that [22–30]crown ethers bind secon-
dary ammonium ions both in solution and in the gas phase, re-
spectively. Moreover, the kinetics of pseudorotaxanes forma-
tion was modified through regulation of the number of atoms
in the crown ether ring, rather then the size of the stoppers
of the dumbbell-like secondary ammonium ion. We found that
the [25]- and [26]crown ether/isopropylphenyl group, [27]-
and [30]crown ether/tert-butylphenyl group, and [22]- and
[23]crown ether/furyl group were matched pairs. The associa-
tion constants (Kexp) were determined through NMR spectro-
scopic titration of the matched pairs of the wheels and the
axles. The [24]crown ether has the optimal ring size because
larger rings lead to decreased association constants and smaller
crown ethers lead to face-to-face complexation rather than
pseudorotaxane formation. These results will be useful when
constructing corresponding rotaxanes.27,28
H36O6 0.5H2O: C, 73.72; H, 6.94%.
ꢃ
1,3-Bis[2-(2-hydroxyphenoxy)ethoxy]propane (14b). A sus-
pension of the benzyl ether 14a (2.50 g, 4.73 mmol), 10% Pd–C
(0.25 g) in ethanol–CHCl3 (1:1, 40 mL) was stirred under atmo-
sphere of H2 for 6 h. The reaction mixture was filtered, and the fil-
trate was concentrated. The residue was purified by silica gel col-
umn chromarography (toluene:ethyl acetate = 2:1) to give the
diol 14b (1.48 g, 90%) as a colorless oil: IR ꢀmax (CHCl3) cmꢁ1
3684, 3619, 3029, 2895, 1522, 1204. 1H NMR (500 MHz, CDCl3)
ꢁ 1.95 (quint, J ¼ 6:1 Hz, 2H), 3.66–3.71 (m, 4H), 3.73–3.78 (m,
4H), 4.13–4.18 (m, 4H), 6.76–6.84 (m, 4H), 6.90–6.96 (m, 6H).
13C NMR (125 MHz, CDCl3) ꢁ 29.7, 67.9, 69.2, 70.4, 115.7,
115.8, 120.0, 123.2, 146.0, 147.5. HR-MS(FAB) m=z: Calcd for
C19H24O6: 348.1573. Found: 348.1499.
Experimental
General. Infrared spectra were recorded on a Shimadzu FTIR-
1
8600PC. H NMR spectra were taken on JEOL EX-400 and LA-
500 spectrometers using TMS as an internal standard. Mass spec-
tra were recorded on JMS-700T instrument. All reactions were
carried out under a positive atmosphere of dry N2 unless otherwise
indicated. All extracts were dried over MgSO4 and the solvent was
removed by rotary evaporation under reduced pressure. Silica gel
column chromatography was performed on Silica Gel 60N (Kanto
Chemical). Thin-layer chromatography was carried out on a Merk
Kieselgel 60PF254. The melting points were uncorrected.
DB26C8-p (3). A suspension of ditosylate 11 (6.97 g, 10.2
mmol), hydroquinone (1.12 g, 10.2 mmol), and cesium carbonate
(19.9 g, 61.2 mmol) in DMF (200 mL) was stirred at 100 ꢂC for 1 d.
After evaporation of the solvent under reduced pressure, to the re-
sulting mixture was added AcOEt. The mixture was washed with
dilute HCl and H2O, dried and evaporated. The residue upon
evaporation of the mixture was chromatographed (ethyl acetate:
toluene = 1:1) to give the crown ether 3 (0.90 g, 20%) as a vis-
cous oil: IR ꢀmax (CHCl3) cmꢁ1 3030, 2933, 2894, 1521, 1212.
1H NMR (500 MHz, CDCl3) ꢁ 3.59–3.68 (m, 8H), 3.73–3.82 (m,
8H), 4.08–4.17 (m, 8H), 6.87 (s, 4H), 6.88–6.94 (m, 4H).
13C NMR (125 MHz, CDCl3) ꢁ 68.80, 68.83, 69.8, 70.2, 70.90,
70.93, 115.4, 116.6, 121.7, 149.1, 153.2. FAB-MS m=z: C24H32O8
DB26C8-o (5). According to the above method, the bisphenol
14b (1.48 g, 4.25 mmol) was transformed into the crown ether 5
(0.953 g, 47%) as a colorless crystal (hexane:AcOEt = 3:2): mp
103–104ꢂC. IR ꢀmax (KBr) cmꢁ1 3063, 2936, 2878, 1593, 1454,
1261. 1H NMR (500 MHz, CDCl3) ꢁ 1.92 (quint, J ¼ 6:3 Hz, 4H),
3.67–3.71 (m, 8H), 3.81–3.84 (m, 8H), 4.12–4.16 (m, 8H), 6.87–
6.92 (m, 8H). 13C NMR (100 MHz, CDCl3) ꢁ 30.1, 68.7, 68.8, 69.8,
116.6, 121.7, 149.0. FAB-MS m=z: C26H36O8 476 [Mþ]. Found: C,
65.29; H, 7.69%. Calcd for C26H36O8: C, 65.53; H, 7.61%.
DB22C7-o (9). Colorless crystal (56% yield, hexane:AcOEt =
4:1): mp 85.5–86.5 ꢂC. IR ꢀmax (KBr) cmꢁ1 3066, 2963, 2875,
1593, 1224. 1H NMR (500 MHz, CDCl3) ꢁ 1.88 (quint, J ¼ 6:3
Hz, 2H), 3.67–3.72 (m, 4H), 3.79–3.84 (m, 4H), 4.00–4.06 (m,
4H), 4.10–4.20 (m, 8H), 6.85–6.93 (m, 8H). 13C NMR (125 MHz,
CDCl3) ꢁ 30.2, 68.3, 69.0, 69.5, 70.0, 70.4, 114.1, 116.0, 121.3,
122.0, 148.9, 149.6. FAB-MS m=z: C23H30O7 418 [Mþ]. Found:
C, 65.90; H, 6.99%. Calcd for C23H30O7: C, 66.01; H, 7.23%.
DB23C7-o (10). Colorless crystal (43% yield, hexane:AcOEt =
7:1): mp 70.5–71.5 ꢂC. IR ꢀmax (KBr) cmꢁ1 2928, 2845,
1594, 1516, 1505, 1450, 1222. 1H NMR (500 MHz, CDCl3) ꢁ
1.66–1.72 (m, 4H), 3.58–3.64 (m, 4H), 3.77–3.82 (m, 4H), 3.97–
4.02 (m, 4H), 4.11–4.14 (m, 4H), 4.16–4.22 (m, 4H), 6.85–6.97
(m, 8H). 13C NMR (125 MHz, CDCl3) ꢁ 26.3, 69.0, 69.1, 70.0,
70.4, 71.2, 113.9, 116.1, 121.3, 122.0, 148.9, 149.6. FAB-MS m=z:
C24H32O7 432 [Mþ]. Found: C, 66.45; H, 7.26. Calcd for
C24H32O7: C, 66.65; H, 7.46%.
448 [Mþ]. Found: C, 62.20; H, 7.07%. Calcd for C24H32O8
0.8H2O: C, 62.27; H, 7.32%.
DB25C8-o (4). According to the above method, the ditosylate
13a (2.21 g, 4.68 mmol) was transformed into the crown ether 4
(1.00 g, 46%) as a colorless crystal (ethyl acetate:hexane = 1:7):
mp 84–85 ꢂC. IR ꢀmax (KBr) cmꢁ1 3067, 2932, 2870, 1593, 1223.
ꢃ

1382 Bull. Chem. Soc. Jpn. Vol. 80, No. 7 (2007)
Dibenzo[22–30]crown form Pseudorotaxanes
ESI-MS and MS/MS Measurements. MS experiments were
performed on a four-sector type mass spectrometer (JEOL JMS-
700T; JEOL, Tokyo, Japan) connected with an ESI interface. The
ion-accelerating voltages were set to 5 kV for MS-1 and 10 kV
for MS-2, respectively. Unless stated otherwise, the solution for
mass spectrometry contained an equimolar amount (0.5mM) of
a crown ether and ammonium salt in acetonitrile and was sprayed
with a flow rate of 2.5 mL hꢁ1 by using a syringe pump (Kd
ScientificInc., Model 100). ESI-MS was performed at a desolvat-
ing temperature of 180 ꢂC and a capillary voltage of 1.8 kV.
The cation of 1:1 complex as a precursor ion selected on MS-1
was collisionally activated by introducing argon into the collision
cell located between MS-1 and MS-2 at a pressure sufficient to
reduce beam intensity by ca. 10%. By grounding the collision cell,
collision energy of 5 kV was chosen. Product-ion spectra were
acquired in MS-2 by scanning of magnetic sector.
Stoddart, P. A. Tasker, D. J. Williams, Angew. Chem., Int. Ed.
Engl. 1995, 34, 1869.
7
M. C. T. Fyfe, P. T. Glink, S. Menzer, J. F. Stoddart, P. A.
Tasker, A. J. P. White, D. J. Williams, Angew. Chem., Int. Ed.
Engl. 1997, 36, 2068; P. R. Ashton, A. N. Collins, M. C. T. Fyfe,
P. T. Glink, S. Menzer, J. F. Stoddart, D. J. Williams, Angew.
Chem., Int. Ed. Engl. 1997, 36, 59.
8 S.-H. Chiu, A. R. Pease, J. F. Stoddart, A. J. P. White, D. J.
Williams, Angew. Chem., Int. Ed. 2002, 41, 270.
9
4174.
S.-H. Chiu, J. F. Stoddart, J. Am. Chem. Soc. 2002, 124,
10 a) P.-N. Cheng, W.-C. Hung, S.-H. Chiu, Tetrahedron Lett.
2005, 46, 4239. b) S. J. Loeb, J. Tiburcio, S. J. Vella, Org. Lett.
2005, 7, 4923.
11 a) For examples, see: W. S. Bryant, I. A. Guzei, A. L.
Rheingold, J. S. Merola, H. W. Gibson, J. Org. Chem. 1998, 63,
7634. b) S.-H. Chiu, A. R. Pease, J. F. Stoddart, A. J. P. White,
D. J. Williams, Angew. Chem., Int. Ed. 2002, 41, 270.
12 P. A. Ashton, I. Baxter, M. C. T. Fyfe, F. M. Raymo, N.
Spencer, J. F. Stoddart, A. J. P. White, D. J. Williams, J. Am.
Chem. Soc. 1998, 120, 2297.
13 Recently, the rotaxane possessing DB25C8-m and secon-
dary ammonium ion was discussed. J. N. Lowe, D. A. Fulton,
S.-H. Chiu, A. M. Elizarov, S. J. Cantrill, S. J. Rowan, J. F.
Stoddart, J. Org. Chem. 2004, 69, 4390.
14 R. M. Izatt, R. E. Terry, D. P. Nelson, Y. Chan, D. J.
Eatough, J. S. Bradshaw, L. D. Hansen, J. J. Christensen, J. Am.
Chem. Soc. 1976, 98, 7626.
15 C. J. Pedersen, J. Am. Chem. Soc. 1967, 89, 7017.
16 G. Yapar, C. Erk, J. Inclusion Phenom. Macrocyclic Chem.
2002, 43, 299.
17 P. R. Ashton, R. A. Bartsch, S. J. Cantrill, R. E. Hanes, Jr.,
S. K. Hickingbottom, J. N. Lowe, J. A. Preece, J. F. Stoddart, V. S.
Talanov, Z.-H. Wang, Tetrahedron Lett. 1999, 40, 3661.
18 Y. Tachibana, H. Kawasaki, N. Kihara, T. Takata, J. Org.
Chem. 2006, 71, 5093.
This work was supported by a Grant-in-Aid for Scientific
Research (No. 15750116) from Ministry of Education, Culture,
Sports, Science and Technology, Japan. We thank Mr. H.
Sugawara of this University making spectroscopic measure-
ments.
Supporting Information
1H NMR spectra (500 MHz, CDCl3–CD3CN (1:1)) of a 1:1
mixture of 3 and 17PF6ꢁ, 4 and 17PF6ꢁ, 5 and 19PF6ꢁ, 6 and
18PF6ꢁ, 7 and 18PF6ꢁ, 9 and 20TsOꢁ, and 10 and 20TsOꢁ and
ESI-MS/MS spectra of 1:1 complexes 1 16, 7 16, and 1 19 are
ꢃ ꢃ
ꢃ
formatted in PDF file.
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