Synthesis of large [2]rotaxanes. the relationship between the size of the blocking group and the stability of the rotaxane

Article abstract of DOI:10.1021/jo302800t

[2]Rotaxanes with large macrocyclic phenanthrolines were prepared by the template method, and the stability of the rotaxanes was examined. Compared to the tris(biphenyl)methyl group, the tris(4-cyclohexylbiphenyl)methyl group was a larger blocking group, and the rate of the dissociation of the components decreased significantly when the thermal stability of a rotaxane with a 41-memebered ring was examined. We also succeeded in the synthesis of larger rotaxanes by the oxidative dimerization of alkynes with these bulky blocking groups, utilizing the catalytic activity of the macrocyclic phenanthroline-Cu complex.

Full text of DOI:10.1021/jo302800t

Article
pubs.acs.org/joc
Synthesis of Large [2]Rotaxanes. The Relationship between the Size
of the Blocking Group and the Stability of the Rotaxane
Shinichi Saito,*,† Eiko Takahashi,† Kouta Wakatsuki,† Kazuhiko Inoue,† Tomoko Orikasa,† Kenta Sakai,†
Ryu Yamasaki,† Yuichiro Mutoh,† and Takeshi Kasama‡
†Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku, Tokyo 162-8601, Japan
‡Instrumental Analysis Research Center for Life Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo
113-8510, Japan
S
* Supporting Information
ABSTRACT: [2]Rotaxanes with large macrocyclic phenanthrolines were prepared by
the template method, and the stability of the rotaxanes was examined. Compared to the
tris(biphenyl)methyl group, the tris(4-cyclohexylbiphenyl)methyl group was a larger
blocking group, and the rate of the dissociation of the components decreased
significantly when the thermal stability of a rotaxane with a 41-memebered ring was
examined. We also succeeded in the synthesis of larger rotaxanes by the oxidative
dimerization of alkynes with these bulky blocking groups, utilizing the catalytic activity of
the macrocyclic phenanthroline−Cu complex.
INTRODUCTION
■
Interlocked compounds such as rotaxanes and catenanes are
synthetically challenging molecules, and various synthetic
methods have been reported to date.1 The template method
is an efficient approach for the synthesis of interlocked
compounds, and this method has been applied for the synthesis
of various interlocked structures.2 In many examples, the
products were isolated in good to high yields, making this
method very attractive for the synthesis of complex interlocked
compounds.
A [2]rotaxane consists of a dumbbell-shaped component and
a ring component. The dissociation of the two components is
suppressed when high activation energy is required for the
dissociation (deslipping) of the components. Therefore, a bulky
“dumbbell” is required for the synthesis of a stable rotaxane3
when no attractive interaction exists between the components.
The relationship between the size of the components and the
Figure 1. Stability of [2]rotaxanes (1a−c) with various ring sizes (ref
4m).
stability of the rotaxanes has been studied by several groups.4
For example, the spatial demand of dendrimers has been
examined by observing the stability of the rotaxanes with
blocking groups derived from dendrimers.4i We recently
reported the synthesis of rotaxanes which consisted of a large
ring component (macrocyclic phenanthroline) and a large
blocking group (tris(biphenyl)methyl group) by the template
method and examined the stability of the rotaxanes (Figure
1).4m While a rotaxane with a 33-membered phenanthroline
ring (1a) was stable at 60 °C in CDCl3, the dissociation of the
components was observed when a rotaxane with 37-membered
ring (1b) was heated to 60 °C. The attempted isolation of a
rotaxane with a larger ring (1c, a 41-membered ring) failed.
These results prompted us to design and study the stability of
rotaxanes with larger blocking groups. In this study, we report
the synthesis and the stability of large [2]rotaxanes.
Received: December 25, 2012
© XXXX American Chemical Society
A
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treatment of the aryllithium, which was prepared by the
treatment of 2b with n-BuLi and ethyl carbonate, and the crude
product was used for the next reaction without purification.
Tris(4-cyclohexylbiphenyl)methane (4b) was synthesized in
46% yield from 2b. Alcohols with large blocking groups (5a,b)
were synthesized by the reaction of lithiated triarylmethanes
with 1-chloro-6-(methoxymethoxy)hexane and the removal of
the methoxymethyl group. The alcohols were converted to the
iodides (6a,b) by PPh3-I2-imidazole in high yields.
[2]Rotaxanes with large rings and dumbbells were prepared
by template method.4m,5 Thus, the tetrahedral Cu complexes
were prepared in situ from 7,4m 8,5 and [Cu(CH3CN)4]PF6.
The complexes reacted with iodide 6, and the copper ion was
removed from the phenanthroline ligand by the treatment of
the crude product with an excess of KCN. The results were
summarized in Table 1.
RESULTS AND DISCUSSION
■
Synthesis of Large [2]Rotaxanes. The introduction of a
substituent to the biphenyl group is a simple and efficient
method for the synthesis of a larger blocking group than
tris(biphenyl)methyl group. We designed and synthesized alkyl
iodides with the tris(4-ethylbiphenyl)methyl group and tris(4-
cyclohexylbiphenyl)methyl group as the precursors for the
dumbbell-shaped moiety of the rotaxanes. The procedures we
previously developed4m for similar compounds were applied for
the synthesis of these compounds (Scheme 1).
Scheme 1
The rotaxane was synthesized in good yield when 7a, 8, and
6a were used as the substrates (entry 1). These results are in
accordance with our previous results,4m where the tris-
(biphenyl)methyl group, which is a smaller group, turned out
to be a suitable blocking group for the synthesis of a stable
rotaxane composed of 7a. Even with a larger phenanthroline
derivative (7b), the corresponding rotaxane was isolated in 64%
yield (entry 2): the dissociation of the rotaxanes was not
observed during the purification of the products.6 The result
indicated the increased stability7 of the rotaxane by using a
larger blocking group, tris(4-ethylbiphenyl)methyl group, since
a rotaxane composed of 7b and an axle with a smaller blocking
group (tris(biphenyl)methyl group) turned out to be labile, and
the dissociation of the components (deslipping reaction) was
observed at 60 °C.4m Though we expected that a stable
rotaxane would be isolated when this large blocking group was
used to synthesize rotaxanes with a 41-memebered macrocycle
(7c), the corresponding rotaxane was not detected, and instead,
we isolated the coupling product (11a) and 7c in high yields
(entry 3).
Expecting a higher stability of the corresponding rotaxanes,
we carried out the synthesis of rotaxanes with a very large
blocking group, tris(4-cyclohexylbiphenyl)methyl group, by the
reaction of 7a−c, 8, and 6b. As expected, the corresponding
rotaxanes were prepared in good yields when smaller
macrocyclic phenanthroline complexes such as 7a or 7b were
used as the starting materials (entries 4 and 5). Disappointingly,
the attempted synthesis of a larger rotaxane, which was
composed of 7c, failed (entry 6). The result indicated that the
size of the ring of 7c was too large, and even a very bulky
blocking group (tris(4-cyclohexylbiphenyl)methyl group) could
pass through the ring with very low energy barrier.8
Thermal Stability of Large [2]Rotaxanes. Since we
isolated some larger rotaxanes that did not dissociate during
standard purification, we were interested in the thermal stability
of these compounds at elevated temperature. Solutions of
rotaxanes in 1,1,2,2-tetrachloroethane-d2 were heated to 70−
140 °C. The deslipping reaction was monitored by NMR.5 The
kinetic paremeters were determined, and the results are
summarized in Table 2.
Triarylmethanes were synthesized from 4-substituted bi-
phenyls. Thus, 4-ethylbiphenyl was brominated, and the
product was treated with Mg and ethyl carbonate to give
tris(4-ethylbiphenyl)methanol (3a) in good yield. The alcohol
was reduced by formic acid to yield tris(4-ethylbiphenyl)-
methane (4a) in 83% yield. Tris(4-cyclohexylbiphenyl)methane
(4b) was prepared from 4-cyclohexylbiphenyl. The reaction of
the Grignard reagent prepared from 2b with ethyl carbonate
did not proceed efficiently, and the yield of the product was
low. The triarylmethanol was prepared in a better yield by the
We have already reported4m that the dissociation of the
components (deslipping reaction) was observed at 60 °C for
1b, and the estimated half-life of the rotaxane at 130 °C was
less than 0.5 h (entry 1). We expected that the rotaxanes
(10a,b,d,e) would be stable because a bulkier blocking group
was introduced and the deslipping reaction would not proceed
easily. The progress of the deslipping reaction, however, was
B
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Table 1. Template Synthesis of [2]Rotaxanes with Various Blocking Groups and Rings
entry
7
6
rotaxane 10
yield (%)
11
yield (%)
recovery of 7 (%)
1
2
3
4
5
6
7a
7b
7c
7a
7b
7c
6a (R=Et)
10a
10b
10c
10d
10e
10f
60
64
0
11a
11a
11a
11b
11b
11b
21
17
78
18
19
63
38
28
91
36
31
88
6a
6a
6b (R=Cy)
51
54
0
6b
6b
observed at elevated temperature. For example, very slow
dissociation of 10a, which is composed of a larger blocking
group (tris(4-ethylbiphenyl)methyl group), was observed at
130 °C, and 20% of 10a dissociated after heating a solution of
10a for 10 days (entry 2). The progress of the deslipping
reaction was faster when the rotaxane was composed of a larger
ring (1b) and the estimated half-life of 10b at 130 °C was 1.1 h
(entry 3). Compound 10d turned out to be very stable, and the
dissociation did not proceeded when a solution of 10d was
heated at 130 °C for 10 days (entry 4). Though a rotaxane with
a larger blocking group (10e) was more stable compared to
10b, the dissociation slowly proceeded at 130 °C (entry 5). It is
noteworthy that even a rotaxane with a very bulky blocking
group (tris(4-cyclohexylbiphenyl)methyl group) still dissoci-
ated when a 37-membered ring (1b) was used as the ring
component of the rotaxane. The observed high entropic
contribution in these reactions is in accordance with our
previous results.4m Though it is difficult to explain the
nanthroline−Cu Complexes. Based on the results of the
deslipping reactions, we expected that rotaxanes composed of
7a,b as the ring component and tris(4-cyclohexylbiphenyl)-
methyl group as the blocking group would be synthesized as
stable compounds. Leigh et al.10 and our group11 recently
developed a conceptually new and efficient method for the
synthesis of rotaxanes and catenanes.12 The catalytic activity of
the macrocyclic metal complex was utilized for the coupling
reactions of substrates with bulky substituents, and the
rotaxanes were isolated in good to high yields. For example,
the oxidative dimerization reaction of alkynes was mediated by
macrocyclic phenanthroline−Cu complexes, providing an
efficient method for the synthesis of [2]rotaxanes.11a We
applied this methodology for the synthesis of larger [2]-
rotaxanes with new dumbbell moieties. We prepared an
arylalkyne (13) with tris(4-cyclohexylbiphenyl)methyl group
as the blocking group by the reaction of 6a and 12 (Scheme 2).
The reactions of 13 with macrocyclic phenanthroline−Cu
complexes (14a,b)11 were carried out in the presence of I2 as
the oxidant and K2CO3 as the base (Scheme 3). The rotaxane
(15a) was isolated in 82% yield when a smaller macrocyclic
phenanthroline−Cu complex (14a) was reacted with a small
excess of 13. We also succeeded in the synthesis of the rotaxane
(15b) when we carried out the reaction of 13 with a larger
difference of the kinetic parameters (ΔH⧧ and ΔS⧧) observed
in these reactions, it has already been reported that these
parameters are strongly affected by changing the structure of
the rotaxane.4j
Synthesis of Large [2]Rotaxanes using the Oxidative
Dimerization Reaction Mediated by Macrocyclic Phe-
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Table 2. Dissociation of [2]Rotaxanes
a
entry
cmpd
R
n
ΔH‡ (kJ/mol)
ΔS‡ (J/(mol·K))
−144
ΔG‡ (403 K) (kJ/mol)
t1/2 (403 K) (h)
b
1
1b
H
6
6
8
6
8
65.0
123
<0.5
c
2
3
4
5
10a
10b
10d
10e
Et
Et
Cy
Cy
80.9
64.8
−119
−212
129
150
1.1
d
35
a
b
c
Estimated by kinetic parameters. Values from ref 4m. This reaction was carried out in CDCl3. Ca. 20% of the substrate dissociated after heating
d
for 10 days (240 h). The dissociation of the substrate was not observed after heating for 10 days (240 h).
conformation, especially when the ring is large (and flexible),
Scheme 2
and the bond-forming reaction may not proceed inside the ring.
In this case, the formation of the rotaxane would not be
observed, and the coupling reaction would proceed without
threading of the axle component.
CONCLUSION
■
We synthesized a series of rotaxanes by template method and
studied the relationship between the size of the blocking group
and the stability of the rotaxane. The structures of some
rotaxanes with a large ring component (37-membered ring)
were stabilized by introducing bulkier blocking groups such as
tris(4-cyclohexylbiphenyl)methyl group. Further application of
these large blocking groups to the synthesis of interlocked
compounds is ongoing.
copper complex (14b). As expected, the rotaxanes (15a,b)
were stable and the deslipping reaction did not proceed when
the compounds were treated at rt or at elevated temperature
(40 °C). The observed lower yield of 15b might be due to the
progress of the deslipping reaction13 during the synthesis of
15b, since the reaction was carried out at 130 °C. Alternatively,
the efficiency of the threading reaction might have decreased
due to the increased flexibility of the macrocyclic ring. Thus,
the macrocyclic compound might adopt bent (folded)
EXPERIMENTAL SECTION
■
Commercially available reagents were purchased and used without
further purification unless otherwise noted. 4-Cyclohexylbiphenyl14
was prepared by the cobalt-catalyzed reaction15 of bromocyclohexane
with the corresponding Grignard reagent ([1,1′-biphenyl]-4-ylmagne-
sium bromide). Macrocyclic phenanthrolines (7a−c)4m and macro-
D
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Scheme 3
cyclic phenanthroline−Cu complexes (14a,b)11 were prepared as
reported. Chemical shifts were reported in δ relative to chloroform
4-Bromo-4′-cyclohexylbiphenyl (2b). The procedure reported
for the synthesis of 2a was generally followed to synthesize 2b. The
crude product was purified by recrystallization from hexane to afford
2b as colorless powder. Compound 2b (28.0 g) was isolated in 78%
yield from 1b (27 g, 114 mmol). 2b: mp 157−158 °C; 1H NMR (500
MHz, CDCl3) δ 7.53 (d, J = 8.5 Hz, 2H), 7.48 (d, J = 8.0 Hz, 2H),
7.44 (d, J = 8.5 Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 2.56−2.52 (m, 1H),
1.92−1.85 (m, 4H), 1.78−1.75 (m, 1H), 1.49−1.37 (m, 4H), 1.31−
1.24 (m, 1H); 13C NMR (126 MHz, CDCl3) δ 147.7, 140.1, 137.4,
131.8, 128.6, 127.4, 126.8, 121.1, 44.2, 34.4, 26.9, 26.1; IR (KBr) 3060,
2921, 2849, 2665, 1902, 1606, 1481, 1447, 1388, 1138, 1121, 1076,
1000, 893, 811, 779, 743, 645, 553, 503 cm−1. Anal. Calcd for
C18H19Br: C, 68.58; H, 6.07. Found: C, 68.76; H, 6.14.
1
(7.24 ppm for H NMR and 77.0 ppm for 13C NMR) or dimethyl
1
sulfoxide (2.49 ppm for H NMR and 39.7 ppm for 13C NMR).
4-Ethylbiphenyl. To a stirred solution of 4-acetylbiphenyl16 (45.3
g, 230 mmol) and 3 mL of concd H2SO4 in EtOH (240 mL) was
added 5% Pd/C (4.53 g) under argon atmosphere. The mixture was
stirred vigorously and heated at 60 °C for 2 days under hydrogen (1
atm). The mixture was filtered, and the solvent was evaporated to give
colorless oil, which was purified by distillation (110 °C, 1.1 mmHg):
yield 30.5 g (73%).
4-Bromo-4′-ethylbiphenyl (2a).17 A solution of bromine (9.0
mL, 176 mmol) in chloroform (90 mL) was added to the mixture of 4-
ethylbiphenyl (30.5 g, 167 mmol) in chloroform (140 mL) at rt. The
mixture was stirred in the dark for 24 h at rt. The solution was poured
into 2 M NaOH aq and stirred for 1 h. The mixture was diluted with
dichloromethane, washed with water, dried over MgSO4, and
concentrated in vacuo. The resulting colorless solid was recrystallized
from ethanol to afford 2a: yield 29.8 g (68%).
Tris(4′-cyclohexyl[1,1′-biphenyl]-4-yl)methanol (3b) and
Tris(4′-cyclohexyl[1,1′-biphenyl]-4-yl)methane (4b). To a sol-
ution of 2b (11.4 g, 36 mmol) in anhydrous THF (90 mL) was added
n-BuLi (1.6 M in hexane, 23 mL, 36 mmol) dropwise over 30 min at
−78 °C under Ar. The reaction mixture was stirred for 1 h. To the
mixture was added dimethyl carbonate (1.0 mL, 12 mmol) at −78 °C.
The resulting mixture was stirred overnight, while the temperature of
the mixture was allowed to reach to rt. The solution was quenched
with MeOH (50 mL), and the solvent was removed by evaporation to
afford crude tris(4′-cyclohexyl[1,1′-biphenyl]-4-yl)methanol (11.2 g)
as a yellow solid, which was employed for the next reaction without
purification. This compound could be purified by recrystallization
(CH2Cl2−hexane).
Tris(4′-ethyl[1,1′-biphenyl]-4-yl)methanol (3a). In a three-
necked flask equipped with a condenser, dropping funnel, and
magnetic stirrer were placed magnesium turnings (0.76 g, 45 mmol)
anhydrous THF (4 mL) under Ar. 4-Bromo-4′-ethylbiphenyl (2a, 7.86
g, 30 mmol) in anhydrous THF (18 mL) was added dropwise over 30
min (exothermic). The mixture was refluxed for 30 min. Methyl
carbonate (0.76 mL, 9.0 mmol) was added slowly at 0 °C, and the
mixture was refluxed for 1 h. The mixture was cooled to rt, neutralized
with 10% HCl, and extracted with dichloromethane. The combined
organic layer was washed with water and dried over MgSO4. A yellow
solid was obtained after removal of the solvent by evaporation. The
solid was purified by silica gel column chromatography (Hex/CH2Cl2
1
3b: mp 204−205 °C; H NMR (300 MHz, CDCl3) δ 7.54 (d, J =
8.8 Hz, 6H), 7.51 (d, J = 8.4 Hz, 6H), 7.38 (d, J = 8.4 Hz, 6H), 7.25
(d, J = 8.4 Hz, 6H), 2.52 (t, J = 11.2 Hz, 6H), 1.91−1.73 (m, 15H),
1.48−1.22 (m, 15H)); 13C NMR (125 MHz, CDCl3) δ 147.2, 145.5,
140.0, 138.0, 128.3, 127.2, 126.9, 126.5, 81.7, 44.2, 34.4, 26.9, 26.3; IR
(KBr) 3563, 3440, 3023, 2923, 2854, 1913, 1612, 1496, 1450, 1396,
1319, 1188, 1157, 1002, 918, 818, 779, 540 cm−1. Anal. Calcd for
C55H58O: C, 89.87; H, 7.95. Found: C, 89.75; H, 8.09.
1
= 3:1): yield 3.09 g (54%); mp 182−183 °C; H NMR (600 MHz,
CDCl3) δ 7.54 (d, J = 8.4 Hz, 6 H), 7.51 (d, J = 8.4 Hz, 6 H), 7.40 (d,
J = 8.4 Hz, 6 H), 7.25 (d, J = 8.4 Hz, 6 H), 2.83 (s, 1 H), 2.67 (q, J =
7.6 Hz, 6 H), 1.26 (t, J = 7.5 Hz, 9 H); 13C NMR (75 MHz, CDCl3)
145.5, δ 143.5, 140.1, 138.0, 128.3 (overlap), 127.0, 126.5, 81.7, 28.5,
15.6; IR (KBr) 3447, 3024, 2963, 2929, 2871, 1906, 1559, 1496, 1454,
1395, 1329, 1266, 1190, 1157, 1117, 1005, 911, 849, 819, 789, 698,
591, 522 cm−1. Anal. Calcd for C43H40O: C, 90.17; H, 7.04. Found: C,
90.19; H, 7.01.
A mixture of crude tris(4′-cyclohexyl[1,1′-biphenyl]-4-yl)methanol
(11.2 g), toluene (58 mL), and formic acid (25 mL) was refluxed for
12 h. The mixture was worked up as described for 4a. The residue was
recrystallized from CH2Cl2−hexane to afford 4b (4.0 g, 46% yield/two
steps) as a colorless amorphous solid.
4b: 1H NMR (500 MHz, CDCl3) δ 7.52 (t, J = 7.0 Hz, 12H), 7.27−
7.22 (m, 12H), 5.62 (s, 1H), 2.55−2.51 (m, 3H), 1.92−1.84 (m, 12H),
1.77−1.74 (m, 3H), 1.49−1.36 (m, 12H), 1.30−1.23 (m, 3H); 13C
NMR (126 MHz, CDCl3) δ 147.1, 142.6, 139.2, 138.3, 129.8, 127.2,
126.91, 126.89, 55.9, 44.2, 34.4, 26.9, 26.2; IR (KBr) 3422, 3023, 2923,
2849, 1905, 1496, 1447, 1398, 1261, 1108, 1005, 828, 812, 794, 776,
565, 535, 440, 409 cm−1. Anal. Calcd for C55H58: C, 91.87; H, 8.13.
Found: C, 91.63; H, 8.17.
Tris(4′-ethyl[1,1′-biphenyl]-4-yl)methane (4a). A mixture of 3a
(1.36 g, 2.38 mmol), toluene (10 mL), and formic acid (5 mL) was
refluxed for 12 h. The mixture was evaporated, and the residue was
dissolved in CH2Cl2 (80 mL). The mixture was neutralized with
K2CO3, dried over MgSO4, and concentrated. The crude product was
purified by recrystallization from Hex/CHCl3 to afford 4a as a
colorless powder: yield 1.10 g (83%); mp 155−157 °C; 1H NMR (600
MHz, CDCl3) δ 7.52 (d, J = 7.6 Hz, 6 H), 7.50 (d, J = 7.6 Hz, 6 H),
7.24 (d, J = 7.8 Hz, 6 H), 7.23 (d, J = 7.8 Hz, 6 H), 5.62 (s, 1 H), 2.67
(q, J = 7.6 Hz, 6 H), 1.26 (t, J = 7.8 Hz, 9 H); 13C NMR (75 MHz,
CDCl3) δ145.5, 143.3, 142.7, 139.2, 138.2, 129.8, 128.3, 126.9, 55.9,
28.5, 15.5; IR (KBr) 3447, 3022, 2962, 2928, 2869, 1908, 1792, 1700,
1653, 1607, 1577, 1559, 1496, 1452, 1398, 1374, 1310, 1271, 1193,
1117, 1059, 1030, 1005, 965, 868, 836 cm−1. Anal. Calcd for C43H40:
C, 92.76; H, 7.24. Found: C, 93.05; H, 7.29.
Preparation of 5a,b from 4a,b. Representative Procedure.
7,7,7-Tris(4′-ethyl[1,1′-biphenyl]-4-yl)heptan-1-ol (5a). n-BuLi (1.6
M solution in hexane, 1.25 mL, 2.0 mmol) was slowly added to the
solution of tris(4-ethylbiphenyl)methane (0.56 g, 1 mmol) in 4.5 mL
of dry THF with stirring at room temperature. The color of the
solution turned to blue. 1-Chloro-6-(methoxymethoxy)hexane18
(0.18g, 1 mmol) was added to the blue solution at room temperature,
and the mixture was stirred for 12 h. MeOH (9 mL) and concd HCl
E
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(0.9 mL) were added to the mixture, and the mixture was heated at 60
°C for 1.5 h. Water was added, and the mixture was extracted with
CH2Cl2. The combined organic layer was dried over MgSO4, and the
solvent was evaporated. The residue was purified by silica gel column
chromatography using hexane−AcOEt (4/1 (v/v)) as the eluent.
Compound 5a was isolated as a colorless amorphous solid (0.44 g,
7.64 (s, 2H), 7.46 (d, J = 8.0 Hz, 12H), 7.45 (d, J = 8.4 Hz, 12H), 7.31
(d, J = 8.4 Hz, 12H), 7.19 (d, J = 8.0 Hz, 12H), 7.10 (t, J = 8.0 Hz,
1H), 7.03 (d, J = 7.2 Hz, 4H), 6.89 (d, J = 7.2 Hz, 4H), 6.70 (s, 1H),
6.46 (d, J = 8.0 Hz, 2H), 3.90−3.86 (m, 8H), 3.73 (t, J = 7.2 Hz, 4H),
2.64 (q, J = 7.6 Hz, 12H), 2.60−2.54 (m, 4H), 1.68−1.62 (m, 12H),
1.42−1.18 (m, 34H); 13C NMR (125 MHz, CDCl3) δ 160.5, 160.4,
160.3, 156.48, 156.2, 146.3, 143.1, 138.3, 138.0, 136.6, 132.4, 131.8,
129.8, 129.6, 129.0, 128.2, 127.4, 126.8, 126.2, 125.5, 125.4, 119.3,
114.8, 114.7, 106.8, 101.5, 68.0, 67.8, 56.0, 40.4, 31.6, 30.4, 29.7, 26.6,
29.5, 29.0, 28.5, 26.1, 25.9, 25.8, 25.6, 22.6, 15.5, 14.1; IR (KBr) 3432,
3023, 2931, 2861, 1905, 1604, 1489, 1419, 1396, 1304, 1250, 1173,
1149, 1119, 1011, 818, 741, 617 cm−1; HR-MS (FAB-MS) calcd for
C164H159N4O6 ([M + H]+) 2280.2260, found 2280.2260. Anal. Calcd
for C164H158N4O6: C, 86.35; H, 6.98; N, 2.46. Found: C, 86.28; H,
6.98; N, 2.31.
1
67%): H NMR (400 MHz, CDCl3) δ 7.51 (d, J = 8.0 Hz, 6H), 7.49
(d, J = 8.1 Hz, 6 H), 7.36 (d, J = 8.4 Hz, 6H), 7.24 (d, J = 8.0 Hz, 6H),
3.58 (q, J = 14 Hz, 2H), 2.67 (m, 8H), 1.49 (q, J = 15 Hz, 2H); 1.40−
1.20 (m, 15H); 13C NMR (100 MHz, CDCl3) δ 146.3, 143.2, 138.4,
138.1, 129.6, 128.2, 126.8, 126.3, 63.0, 56.0, 40.4, 32.8, 30.2, 28.5, 25.7,
25.6, 15.5; IR (KBr) 3334, 3023, 2961, 2931, 2869, 1906, 1792, 1653,
1608, 1558, 1496, 1456, 1004, 815, 517 cm−1. Anal. Calcd for
C49H52O: C, 89.59; H, 7.98. Found: C, 89.33; H, 8.03.
5b: colorless amorphous solid: yield 0.28 g (49%, from 0.50 g (0.7
1
mmol) of 4b); H NMR (500 MHz, CDCl3) δ 7.55 (t, J = 8.0 Hz,
Rotaxane 10b: colorless amorphous solid; yield 149 mg (64%); 1H
NMR (300 MHz, CDCl3) δ 8.42 (d, J = 8.1 Hz, 4H), 8.40 (d, J = 8.4
Hz, 4H), 8.16 (d, J = 8.4 Hz, 2H), 8.11 (d, J = 8.4 Hz, 2H), 8.01 (d, J
= 9.0 Hz, 2H), 7.94 (d, J = 8.4 Hz, 2 H), 7.64 (s, 2H), 7.62 (s, 2H),
7.47 (d, J = 8.1 Hz, 12H), 7.46 (d, J = 8.7 Hz, 12H), 7.32 (d, J = 8.7
Hz, 12H), 7.20 (d, J = 8.47 Hz, 12H), 7.12 (t, J = 8.1 Hz, 1H), 7.00 (d,
J = 9.0 Hz, 4H), 6.95 (d, J = 8.7 Hz, 4H), 6.64 (s, 1H), 6.46 (d, J = 8.6
Hz, 2H), 3.88 (t, J = 6.0 Hz, 4H), 3.77 (t, J = 6.6 Hz, 4H), 3.68 (t, J =
6.6 Hz, 4H), 2.66 (q, J = 7.5 Hz, 12H), 2.59−2.50 (m, 4H), 1.72−1.40
(m, 16H), 1.37−1.19 (m, 8H), 1.24 (t, J = 7.5 Hz, 18 H), 1.19−0.99
(m, 16H); 13C NMR (151 MHz, CDCl3) δ 160.5, 160.4, 165.4, 156.3,
156.2, 146.3, 146.0, 143.1, 138.3, 138.0, 136.6, 131.7, 129.8, 129.6,
128.9, 128.9, 128.3, 128.2, 127.4, 127.4, 126.8, 126.2, 125.5, 119.2,
114.7, 114.7, 106.7, 101.2, 67.8, 67.8, 55.9, 40.4, 30.3, 29.3, 29.3, 29.2,
28.5, 25.9, 25.9, 25.7, 25.5, 15.5; IR (KBr) 3024, 2929, 2855, 1903,
1602, 1587, 1494, 1249, 1173, 836, 816 cm−1. Anal. Calcd for
C168H166N4O6: C, 86.34; H, 7.16; N, 2.40. Found: C, 86.51; H, 7.12;
N, 2.37.
12H), 7.42 (d, J = 8.5 Hz, 6H), 7.30 (d, J = 8.5 Hz, 6H), 3.61 (t, J =
7.0 Hz, 2H), 2.69−2.66 (m, 2H), 2.59−2.54 (m, 3H), 1.96−1.88 (m,
12H), 1.81−1.78 (m, 3H), 1.54−1.24 (m, 23H) ; 13C NMR (126
MHz, CDCl3) δ 147.0, 146.3, 138.4, 138.1, 129.5, 127.1, 126.8, 126.2,
62.9, 56.0, 44.2, 40.4, 34.4, 32.7, 30.2, 26.9, 26.1, 25.7, 25.6; IR (KBr)
3421, 3025, 2924, 2849, 2365, 2110, 1655, 1559, 1497, 1448, 1004,
813, 470, 438, 410 cm−1. Anal. Calcd for C61H70O: C, 89.43; H, 8.61.
Found: C, 89.32; H, 8.70.
Preparation of 6a,b from 5a,b. Representative Procedure.
To a mixture of 5a (1.64 g, 2.5 mmol), Ph3P (1.31 g, 5.0 mmol), and
imidazole (0.374 g, 5.5 mmol) in anhydrous ether/CH3CN (7.5 mL/
2.5 mL) was added I2 (1.40 g, 5.5 mmol) with stirring at rt. After 2 h,
the reaction mixture was quenched with saturated aqueous Na2S2O3,
and the aqueous phase was extracted with CH2Cl2. The combined
organic layer was dried over MgSO4 and concentrated in vacuo. The
residue was purified by silica gel column chromatography using
hexane−CH2Cl2 (3/1(v/v)) as the eluent to yield 6a (1.80 g, 94%) as
a colorless amorphous solid: 1H NMR (300 MHz, CDCl3) δ 7.51 (d, J
= 8.4 Hz, 6H), 7.50 (d, J = 8.7 Hz, 6H), 7.36 (d, J = 8.4 Hz, 6H), 7.24
(d, J = 8.7 Hz, 6H), 3.13 (t, J = 7.1 Hz, 2H), 2.67 (q, J = 7.5 Hz, 6H),
2.70−2.57 (m, 2H), 1.82−1.66 (m, 2H), 1.42−1.30 (m, 4H), 1.25 (t, J
= 7.5 Hz, 9H), 1.26−1.10 (m, 2H); 13C NMR (75 MHz, CDCl3) δ
146.2, 143.2, 138.4, 138.0, 129.5, 128.2, 126.8, 126.3, 56.0, 40.3, 33.5,
30.4, 29.3, 28.5, 25.5, 15.6, 7.2; IR (KBr) 3022, 2962, 2928, 2869,
1903, 1496, 1005, 813 cm−1. Anal. Calcd for C49H51I: C, 76.75; H,
6.70. Found: C, 77.00; H, 6.57.
Rotaxane 10d: colorless amorphous solid; yield 132 mg (51%); 1H
NMR (300 MHz, CDCl3) δ 8.43 (d, J = 8.5 Hz, 4H), 8.39 (d, J = 8.7
Hz, 4H), 8.15 (d, J = 8.5 Hz, 2H), 8.12 (d, J = 8.7 Hz, 2H), 8.00 (d, J
= 8.7 Hz, 2H), 7.96 (d, J = 8.5 Hz, 2H), 7.67 (s, 2H), 7.64 (s, 2H),
7.46 −7.50 (m, 24H), 7.33 (d, J = 8.3 Hz, 12H), 7.23 (d, J = 8.5 Hz,
12H), 7.13 (t, J = 8.1 Hz, 1H), 7.06 (d, J = 8.5 Hz, 4H), 6.91 (d, J = 8
0.5 Hz, 4H), 6.73 (s, 1H), 6.48 (d, J = 8.3 Hz, 2H), 3.91−3.89 (m,
8H), 3.76 (t, J = 7.0 Hz, 4H), 2.66−2.53 (m, 10H), 1.88−1.59 (m,
42H), 1.50−1.27 (m, 50H); 13C NMR (125 MHz, CDCl3) δ 160.5,
160.4, 160.3, 156.5, 156.2, 146.9, 146.3, 145.9, 138.3, 138.1, 136.7,
131.9, 131.7, 129.8, 129.7, 129.5, 128.9, 127.4, 127.1, 126.9, 126.8,
126.7, 126.2, 125.5, 125.4, 119.4, 114.7, 114.6, 106.8, 101.5, 67.9, 67.7,
55.9, 44.2, 40.4, 34.4, 30.3, 29.7, 29.5, 29.4, 29.0, 26.9, 26.1, 26.0, 25.9,
25.8, 25.6; IR (KBr) 2923, 2849, 1602, 1587, 1489, 1248, 1173, 1004,
835, 813, 469 cm−1; HR-MS (ESI-TOF) calcd for C188H196N4O6 ([M
+ 2H]2+) 1302.7577, found 1302.7579.
6b: colorless amorphous solid: yield 0.47 g (96% from 0.44 g (0.53
1
mmol) of 5b); H NMR (500 MHz, CDCl3) δ 7.50 (t, J = 8.5 Hz,
12H), 7.35 (d, J = 8.0 Hz, 6H), 7.24 (d, J = 8.0 Hz, 6H), 3.12 (t, J =
7.0 Hz, 2H), 2.63−2.59 (m, 2H), 2.54−2.49 (m, 3H), 1.90−1.82 (m,
12H), 1.75−1.73 (m, 5H), 1.47−1.17 (m, 21 H); 13C NMR (126
MHz, CDCl3) δ 147.1, 146.2, 138.5, 138.2, 129.5, 127.2, 126.8, 126.3,
56.0, 44.2, 40.4, 34.4, 33.5, 30.4, 29.3, 26.9, 26.2, 25.5, 7.15; IR (KBr)
3024, 2923, 2848, 2360, 1734, 1717, 1699, 1685, 1654, 1559, 1542,
1496, 1447, 1396, 1193, 1004, 812, 529, 472, 442, 418, 410 cm−1. Anal.
Calcd for C61H69I: C, 78.86; H, 7.49. Found: C, 78.71; H, 7.51.
General Procedure for the Template Synthesis of [2]-
Rotaxanes (Table 1). To a solution of Cu(CH3CN)4PF6 (37 mg,
0.1 mmol) in dry CH2Cl2 (5 mL) was added macrocyclic
phenanthroline 7 (0.1 mmol), and the mixture was stirred at room
temperature. After 5 min, the solution was added to a suspension of
Rotaxane 10e: colorless amorphous solid; yield 143 mg (54%); 1H
NMR (300 MHz, CDCl3) δ 8.71−8.41 (m, 8H), 8.17 (d, J = 8.5 Hz,
2H), 8.11 (d, J = 8.5 Hz, 2H), 8.03 (d, J = 8.5 Hz, 2H), 7.96 (d, J = 8.5
Hz, 2H), 7.65 (s, 2H), 7.63 (s, 2H), 7.52−7.48 (m, 24H), 7.34 (d, J =
8.5 Hz, 12H), 7.24 (d, J = 8.3 Hz, 12H), 7.15 (t, J = 8.1 Hz, 1H), 7.03
(d, J = 8.7 Hz, 4H), 6.98 (d, J = 8 0.7 Hz, 4H), 6.68 (s, 1H), 6.50 (d, J
= 8.3 Hz, 2H), 3.91 (t, J = 6.2 Hz, 4H), 3.79 (t, J = 6.4 Hz, 4H), 3.70
(t, J = 6.6 Hz, 4H), 2.61−2.48 (m, 10H), 1.88−1.68 (m, 30H), 1.51−
1.35 (m, 70H); 13C NMR (125 MHz, CDCl3) δ 160.5, 160.4, 160.4,
156.3, 156.1, 146.9, 146.3, 145.9, 138.3, 138.1, 136.6, 131.6, 129.8,
129.5, 128.9, 127.3, 127.1, 126.7, 126.2, 125.4, 119.1, 114.7, 114.6,
106.7, 101.3, 67.8, 67.7, 55.9, 44.1, 40.4, 34.4, 30.2, 29.3, 29.2, 29.1,
26.8, 26.1, 25.9, 25.8, 25.7, 25.5; IR (KBr) 2923, 2849, 1602, 1587,
1489, 1248, 1173, 1004, 835, 813, 469 cm−1; HR-MS (ESI-TOF) calcd
for C192H204N4O6 ([M + 2H]2+) 1330.7890, found 1330.7916.
8
19 (0.1 mmol) in dry CH3CN (5 mL), and the mixture was stirred at
room temperature for 1 h. The solvent was removed under reduced
pressure. To the residue were added 6 (0.2 mmol), dry DMF (2 mL),
and Cs2CO3 (130 mg, 0.4 mmol). The reaction mixture was stirred at
60 °C for 2 days, and then DMF was removed in vacuo. To the residue
were added CH3CN (10 mL), CH2Cl2 (5 mL), H2O (5 mL), and
KCN (33 mg, 0.5 mmol), and the mixture was stirred at room
temperature for 14 h. The organic layer was washed with water, dried
over Na2SO4, and concentrated in vacuo. The residue was purified by
silica gel column chromatography using hexane−CH2Cl2 as the eluent.
Rotaxane 10a: pale yellow amorphous solid; yield 136 mg (60%);
1H NMR (300 MHz, CDCl3) δ 8.39−8.36 (br, 8H), 8.14 (d, J = 8.0
Hz, 2H), 8.11 (d, J = 8.4 Hz, 2H), 8.00−7.94 (br, 4H), 7.66 (s, 2H),
1
11a: colorless amorphous solid; H NMR (300 MHz, CDCl3) δ
8.38 (d, J = 8.7 Hz, 4H), 8.22 (d, J = 8.4 Hz, 2H), 8.04 (d, J = 8.4 Hz,
2H), 7.71 (s, 2H), 7.50 (d, J = 8.1 Hz, 24H), 7.38 (d, J = 8.4 Hz, 12H),
7.23 (d, J = 8.7 Hz, 12H), 7.04 (d, J = 8.7 Hz, 4H), 4.00 (t, J = 6.3 Hz,
4H), 2.66 (q, J = 7.5 Hz, 12H), 2.70−2.62 (m, 4H), 1.83−1.70 (m,
4H), 1.52−1.37 (m, 8H), 1.25 (t, J = 7.5 Hz, 18H), 1.30−1.17 (m,
F
dx.doi.org/10.1021/jo302800t | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
4H); 13C NMR (75 MHz, CDCl3) δ 160.5 156.4, 146.3, 145.8, 143.2,
138.4, 138.0, 136.9, 131.7, 129.6, 129.0, 128.2, 127.5, 126.8, 126.3,
125.6, 119.5, 114.7, 68.0, 56.0, 40.4, 30.2, 29.3, 28.5, 26.0, 25.7, 15.5;
IR (KBr) 3023, 2960, 2930, 2867, 1902, 1602, 1495, 1248, 1173, 1005,
815 cm−1. Anal. Calcd for C122H116N2O2: C, 89.23; H, 7.12; N, 1.71.
Found: C, 89.53; H, 7.18; N, 1.69.
55.9, 44.2, 40.4, 34.4, 30.1, 29.6, 29.1, 26.9, 26.1, 25.9, 25.8, 25.7, 25.6;
IR (KBr) 3025, 2922, 2849, 1601, 1495, 1447, 1286, 1248, 1170, 1004,
833, 532 cm−1; HR-MS (MALDI-TOF) calcd for C180H189N2O6 ([M
+ H]+) 2474.4540, found 2474.4662.
Rotaxane 15b: colorless amorphous (37 mg, 74%); 1H NMR (300
MHz, CDCl3) δ 8.40 (d, J = 8.9 Hz, 4H), 8.17 (d, J = 8.5 Hz, 2H),
8.00 (d, J = 8.5 Hz, 2H), 7.67 (s, 2H), 7.50−7.45 (m, 24H), 7.39 (d, J
= 8.9 Hz, 4H), 7.39 (d, J = 8.5 Hz, 12H), 7.25−7.22 (m, 12H), 7.10 (t,
J = 8.1 Hz, 1H), 7.01 (d, J = 8.9 Hz, 4H), 6.72 (d, J = 8 0.9 Hz, 4H),
6.51 (s, 1H), 6.44 (d, J = 8.3 Hz, 2H), 3.93−3.86 (m, 8H), 3.78 (t, J =
6.4 Hz, 4H), 2.59−2.47 (m, 10H), 1.88−1.57 (m, 40H), 1.50−1.13
(m, 60H); 13C NMR (125 MHz, CDCl3) δ 160.7, 160.4, 159.7, 156.1,
147.0, 146.3, 138.4, 138.1, 134.0, 129.7, 129.5, 129.0, 127.4, 127.2,
126.8, 126.2, 125.5, 114.8, 114.6, 113.6, 106.9, 100.8, 81.5, 73.2, 68.0,
67.9, 67.8, 67.7, 56.0, 44.2, 40.4, 34.4, 30.2, 29.7, 29.3, 29.3, 29.2, 29.1,
26.9, 26.2, 25.9, 25.8, 25.7, 25.6; IR (KBr) 3025, 2923, 2849, 1602,
1496, 1249, 1170, 1004, 813, 531 cm−1; HR-MS (MALDI-TOF) calcd
1
11b: colorless amorphous solid; H NMR (500 MHz, CDCl3) δ
8.42 (d, J = 9.0 Hz, 4H), 8,22 (d, J = 8.5 Hz, 2H), 8.06 (d, J = 9.0,
2H), 7.71 (s, 2H), 7.54−7.52 (m, 24H), 7.40(d, J = 8.5 Hz, 12H), 7.26
(d, J = 8.5 Hz, 12H), 7.08 (d, J = 9.0 Hz, 4H), 4.02 (t, J = 6.5 Hz, 4H),
2.70−2.67 (m, 4H), 2.55−2.50 (m, 6H), 1.92−1.74 (m, 34H), 1.49−
1.22 (m, 42H); 13C NMR (125 MHz, CDCl3) δ 160.4, 156.3, 147.0,
146.3, 146.0, 138.4, 138.2, 136.7, 131.9, 129.6, 128.9, 127.4, 127.2,
126.8, 126.3, 125.5, 119.2, 114.7, 67.9, 56.0, 44.2, 40.4, 34.4, 30.2, 29.3,
26.9, 26.1, 25.9, 25.7; IR (KBr) 3024, 2923, 2848, 1736, 1603, 1495,
1447, 1247, 1173, 1004, 836, 812, 732, 528, 439 cm−1. Anal. Calcd for
C146H152N2O2: C, 89.16; H, 7.79; N, 1.42. Found: C, 88.91; H, 7.98;
N, 1.38.
+
for C184H197N2O6 ([M + H] ) 2530.5166, found 2530.507.
Deslipping Reactions of [2]Rotaxanes (Table 2). A solution of
the rotaxane (1 μmol) in 1,1,2,2-tetrachloroethane-d2 (0.6 mL) was
heated in an NMR tube. The ratio of the starting material and the axle
was monitored by the integration of the NMR signals (rotaxane
(10a,b,e): 3.7−3.95 ppm, dissociated compounds (7a,b and 11a,b):
3.95−4.1 ppm). Heating was continued until 50−60% of the rotaxane
dissociated. The kinetic parameters were calculated by carrying out
these reactions at different temperatures.
Alkyne 13. To a solution of 6b (0.65 g, 0.7 mmol) and 2-(4-
hydroxyphenyl)-1-trimethylsilylacetylene20 (12, 0.26 g, 1.4 mmol) in
DMF (10 mL) was added K2CO3 (1.0 g, 7.0 mmol) with stirring. The
mixture was heated to 60 °C and stirred for 14 h. Then DMF was
removed in vacuo. To the residue were added THF (5 mL), MeOH (5
mL), KF (1.0 g), and KOH (0.04 g). After being stirred at 60 °C for
19 h, the mixture was cooled to room temperature and acidified with 2
M aqueous HCl to pH 2. The aqueous layer was extracted with
CH2Cl2, and the organic layer was dried over MgSO4 and
concentrated in vacuo. The residue was purified by silica gel column
chromatography using hexane−CH2Cl2 (6/1 (v/v)) to afford 13 (0.52
g, 82%) as a colorless amorphous solid: 1H NMR (300 MHz, CDCl3)
δ 7.52−7.47 (m, 12H), 7.38−7.33 (m, 8H), 7.26−7.22 (m, 6H), 6.77
(d, J = 9.0 Hz, 2H), 3.88 (t, J = 6.4 Hz, 2H), 2.96 (s, 1H), 2.65−2.48
(m, 5H), 1.87−1.71 (m, 18H), 1.50−1.22 (m, 20H); 13C NMR (125
MHz, CDCl3) δ 159.5, 147.1, 146.3, 138.4, 138.2, 133.5, 129.6, 127.2,
126.8, 126.3, 120.3, 114.4, 83.8, 75.6, 67.9, 56.0, 44.2, 40.4, 34.4, 30.1,
29.1, 26.9, 26.2, 25.9, 25.6; IR (KBr) 3284, 3024, 2923, 2849, 1605,
1496, 1447, 1248, 1004, 812, 534 cm−1. Anal. Calcd for C69H74O: C,
90.15; H, 8.11. Found: C 89.97; H, 8.11.
General Procedure for the Synthesis of [2]Rotaxanes by
Oxidative Coupling Reactions of Alkynes. To a mixture of
macrocyclic phenanthroline−Cu(I) complex 14 (0.02 mmol), alkyne
13 (74 mg, 0.08 mmol), and K2CO3 (0.017g, 0.12 mmol) in dry xylene
(1.0 mL) was added I2 (10 mg, 0.04 mmol) with stirring. The mixture
was heated to 130 °C and stirred for 48 h. CH3CN (3 mL), CH2Cl2 (3
mL), KCN (10 mg, excess), and H2O (2 mL) were added, and the
mixture was stirred at room temperature for 4 h. The aqueous layer
was extracted with CH2Cl2, and the combined organic layer was
washed with water. The organic layer was dried over MgSO4 and
concentrated in vacuo. The residue was purified by silica gel column
chromatography using hexane−CH2Cl2 (3/1 (v/v)) as the eluent and
preparative GPC to afford rotaxane 15.
ASSOCIATED CONTENT
■
S
* Supporting Information
NMR spectra (1H, 13C) for new compounds and details of the
kinetic experiments. This material is available free of charge via
the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*Tel: +81-3-5228-8715. E-mail: ssaito@rs.kagu.tus.ac.jp.
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the UBE Foundation for financial support. This work
was supported in part by JSPS KAKENHI Grant No.
21655017.
REFERENCES
■
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Rotaxane 15a: colorless amorphous (41 mg, 82%); 1H NMR (500
MHz, CDCl3) δ 8.39 (d, J = 8.5 Hz, 4H), 8.17 (d, J = 8.2 Hz, 2H),
8.00 (d, J = 8.5 Hz, 2H), 7.67 (s, 2H), 7.50 −7.46 (m, 24H), 7.41 (d, J
= 8.9 Hz, 2H), 7.32 (d, J = 8.5 Hz, 12H), 7.24−7.22 (m, 12H), (t, J =
8.2 Hz, 1H), 6.98 (d, J = 8.9 Hz, 4H), 6.73 (d, J = 8 0.9 Hz, 4H), 6.63
(s, 1H), 6.47 (d, J = 8.3 Hz, 2H), 3.95−3.89 (m, 8H), 3.77 (t, J = 6.4
Hz, 4H), 2.58−2.49 (m, 10H), 1.90−1.73 (m, 28H), 1.62−1.57 (m,
4H), 1.47−1.13 (m, 50H); 13C NMR (125 MHz, CDCl3) δ 160.5,
160.4, 159.7, 156.3, 147.0, 146.2, 138.4, 138.1, 136.7, 134.0, 131.7,
129.7, 129.5, 128.9, 127.4, 127.1, 127.0, 126.9, 126.8, 126.2, 125.5,
119.2, 114.8, 114.7, 113.5, 107.1, 100.9, 81.6, 73.3, 67.9, 67.8, 67.7,
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(3) Most of the rotaxanes described in this paper are “pseudorotax-
anes”, which are metastable and dissociate under certain conditions.
We suspect, however, that a significant number of “rotaxanes” reported
to date are “psudorotaxanes”, since the detailed study of the
dissociation reaction under harsh conditions has not been carried
out for many compounds. Therefore, we described our compounds as
“rotaxanes”. It may be necessary to utilize kinetic parameters for the
G
dx.doi.org/10.1021/jo302800t | J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
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reviewer for valuable suggestions.
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