Bromination of N-phenyloxypropyl-N′-ethyl-4,4′-bipyridium in cucurbit[8]uril molecular reactor

Article abstract of DOI:10.1016/j.cclet.2016.10.004

CB[n] (n?=?6–8) is a family of synthetic macrocyclic host molecules composed of n glycoluril units, which can be employed as molecular reactor. N-Phenyloxypropyl-N′-ethyl-4,4′-bipyridium (1) was designed to form a host–guest inclusion complex with CB[n] (n?=?6–8), subsequently, the bromination reaction of 1 and its corresponding inclusion complexes was investigated in this work. In the case of 1/CB[8], the folded including mode is quite helpful to acquire 1-bormination product completely through intramolecular charge transfer (ICT), and CB[8] can provide a safe bromination environment for 1.

Full text of DOI:10.1016/j.cclet.2016.10.004

G Model
CCLET 3839 1–4
Chinese Chemical Letters xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
1
Original article
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Bromination of N-phenyloxypropyl-N -ethyl-4,4 -bipyridium in
cucurbit[8]uril molecular reactor
a
a
a
a,
b,
4
Q1
Tian-Tian Li , Lan-Lan Wen , Hai-Long Ji , Feng-Yu Liu *, Shi-Guo Sun *
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6
a
State Key Laboratory of Fine Chemicals, School of Chemistry, Dalian University of Technology, Dalian 116023, China
College of Science, Northwest A&F University, Yangling 712100, China
b
A R T I C L E I N F O
A B S T R A C T
Article history:
Received 23 June 2016
CB[n] (n = 6–8) is a family of synthetic macrocyclic host molecules composed of n glycoluril units, which
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Received in revised form 13 September 2016
Accepted 18 September 2016
Available online xxx
can be employed as molecular reactor. N-Phenyloxypropyl-N -ethyl-4,4 -bipyridium (1) was designed to
form a host–guest inclusion complex with CB[n] (n = 6–8), subsequently, the bromination reaction of 1
and its corresponding inclusion complexes was investigated in this work. In the case of 1/CB[8], the
folded including mode is quite helpful to acquire 1-bormination product completely through
intramolecular charge transfer (ICT), and CB[8] can provide a safe bromination environment for 1.
ã 2016 Feng-Yu Liu and Shi-Guo Sun. Chinese Chemical Society and Institute of Materia Medica, Chinese
Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Keywords:
Cucurbituril
Molecular reactor
Intramolecular charge transfer (ICT)
Bromination
Inclusion
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1
. Introduction
provide a possibility to fine modulate the reaction through
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different binding mode aroused by the different CB[n] cavity. To
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In recent years, the host–guest chemistry of the cucurbit[n]uril
CB[n], where n = 5–8, 10, and 14) family has been making big
touch this unexplored issue, N-phenyloxypropyl-N -ethyl-4,4 -
bipyridium (1, Fig. 1) was designed based on our previous work
[12]. In this molecule, the donor segment, phenoxy moiety, is
(
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
progress due to their tubular molecular structures [1–3]. In which
the two polar “portals” together with a hydrophobic cavity and a
modest or low water solubility provide an environmentally
friendly water soluble confined medium for chemical reactions
taken place. Among them, CB[6], CB[7] and CB[8] are more
attractive due to their proper cavity size. Since CB[6] was pioneered
as a reactor for 1,3-dipolar cycloaddition reactions in 1983 [4],
several other examples of photocycloadditions using CB[7] and CB
2+
covalently linked to the ethyl viologen dication (EV ) fragment to
facilitate the ICT interaction (as seen from its folded conformation
in Fig. 1), permitting the phenol moiety inserted together with the
viologen moiety into the cavity of CB[8]. Meanwhile, the viologen
moiety can be included in CB[7], and the phenoxy moiety can be
included in CB[6] due to the relative small cavity size (Fig. 1). All
these provide a possibility to perform the same reaction in the
presence of different CB[n] cavity.
Considering that electrophilic aromatic substitution reactions
such as bromination, nitration, sulfonation etc. are important ways
to introduce functional groups onto benzene rings, especially,
these reactions are quite fundamental either in basic organic
chemistry books or for typical organic synthesis, herein, bromina-
tion of 1 and its corresponding inclusion complexes of CB[n] (n = 6–
8) was investigated. The results demonstrated that CB[8]
performed pretty well as a molecular reactor to control bromina-
tion results of 1, more importantly, CB[8] can provide a safe
bromination environment for 1, which is quite helpful to acquire 1-
bormination product completely and enhance the stability of the
corresponding reaction products. While the host–guest assembly
of 1/CB[n] (n = 6, 7) would definitely decrease the ICT interaction of
[8] were reported [5]. Meanwhile, CB[7] was further employed as a
barrel together with transition-metal ions as lids, to control phase-
selective photolysis of bicyclic azoalkanes [6]. While CB[8] can
mediate intermolecular photodimerization either in the solid state
or in aqueous solution [7]. Furthermore, several other applications
using CB[n] (n = 6–8) were reported in succession [8–11]. To gain
further understanding on the CB[n] based molecular reactor, it
would be interesting to employ the same reactant/reagent and
perform the same reaction under the circumstance of different CB
[n] cavity. To fulfill this, a fundamental question is whether the
reactant can form a host–guest interaction with different CB[n], to
5
5
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5
2
3
4
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*
Corresponding authors.
1, leading to the molecule to be broken down easily during
E-mail addresses: liufengyu@dlut.edu.cn (F.-Y. Liu), sunsg@nwsuaf.edu.cn
(
S.-G. Sun).
bromination (Scheme 1). Such an assay would be helpful for
http://dx.doi.org/10.1016/j.cclet.2016.10.004
001-8417/ã 2016 Feng-Yu Liu and Shi-Guo Sun. Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V.
All rights reserved.
1
0
0
Please cite this article in press as: T.-T. Li, et al., Bromination of N-phenyloxypropyl-N -ethyl-4,4 -bipyridium in cucurbit[8]uril molecular
reactor, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.10.004

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T.-T. Li et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
Table 1
Bromination result (HPLC isolated yield (%)) of 1 and 1/CB[n] (n = 6–8).
Sample
Time
T1 (%)
T2 (%)
By-product (%)
(
1-bromination)
(2-bromination)
1
10 min
84.0
69.8
51.2
19.2
10.9
19.1
34.1
10.0
3.7
6.5
14.1
40.9
3
2
5
0 min
h
h
1/CB[8]
1/CB[6]
1/CB[7]
10 min
100.0
100.0
98.2
0
0
1.0
11.6
0
0
0
0
3
2
5
0 min
h
h
82.6
Fig. 1. Structure of 1 and schematic representation of the assembly of 1/CB[n] (n =
10 min
83.6
69.2
57.2
0
15.4
30.8
34.7
16.0
0
0
0
6
–8).
3
2
5
0 min
h
h
5
5
7
8
investigating functional systems centered on the CB[n] molecular
reactor.
83.0
10 min
30 min
81.3
13.5
5.8
–
7.0
30.7
34.6
–
11.0
46.2
49.2
–
5
9
2. Results and discussion
2
5
h
h
6
6
6
6
6
6
6
6
6
6
7
7
7
7
7
7
7
7
7
7
8
8
8
8
8
8
8
8
8
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
The inclusion of the viologen derivatives in CB[n] (n = 6–8) has
been studied extensively in the literature [13]. Accordingly,
formation of the including complex CB[n] (n = 6–8) and 1/CB[n]
8
9
9
9
9
9
9
9
9
9
9
0
1
2
3
4
5
6
7
8
1
can be well modulated by the confined environment of CB[8]
(Figs. S7–S8 in Supporting information). When the reaction lasted
for 10 min, for 1 alone, there would be 84.0% T1 and 10.9% T2
products in aqueous solution. In the case of 1/CB[8], the folded ICT
including mode is quite helpful to acquire T1 completely in
confined hydrophobic environment of CB[8] (Figs. S7–S8 in
Supporting information).
(
n = 6–8) can be clearly observed on H NMR (Figs. S1–S3 in
1
Supporting information). H NMR titration experiment supported
the formation of a 1:1 host–guest complex 1/CB[n] [14–17].
Electrospray ionization mass spectrometry (ESI-MS, Fig. S4 in
Supporting information) gave a positively charged peak at m/z
ꢀ 2+
6
51.20 (calcd. for [1 + CB[6]-2Cl ] , 651.23) in the case of CB[6], m/
ꢀ 2+
z 734.17 (calcd. for [1 + CB[7]-2Cl ] , 734.25) for CB[7], and m/z
ꢀ 2+
A molecular modeling research (HyperChem with Molecular
Mechanics) also showed that the molecule 1 inside the cavity of CB
[8] adopted a folded conformation to place the phenoxy moiety in a
8
17.25 (calcd. for [1 + CB[8]-2Cl ] , 817.28) for CB[8], respectively,
providing direct evidence for the formation of the 1:1 including
complex. The formation of 1:1 including complex was further
confirmed by UV/vis absorption titration experiments (Fig. S5 in
Supporting information). It is noted that 1 revealed an absorption
band at around 260 nm, whose absorption intensity decreased
gradually with the addition of CB[n] (n = 6–8). In the case of 1/CB
2
+
99
close interaction distance with EV moiety (Fig. 2), which was in
good accordance with the argument in the literature [12].
According to the results of HPLC-MS (Fig. S11 in Supporting
information), bromination products of 1 could be decomposed into
1
1
1
00
01
02
0
103
104
105
106
other by-products easily, such as 4,4 -bipyridinum radical cation
[
8], a broad new absorption band appeared at about 310 nm, which
+
ꢁ
+ꢁ
+ꢁ
(V ) (MS (ESI, m/z): (V ) C10H11N2 , calculated for 159.1, found,
can be attributed to the ICT resulting from the host–guest complex
formation [12], providing an additional evidence for the host–
guest complexes formation.
To make a reference for high performance liquid chromato-
graph (HPLC), standard substances T1 (1-bromination) and T2 (2-
bromination) were synthesized (synthetic procedures were shown
in Supporting information). The bromination experimental results
could be analyzed through HPLC and chromatography mass
spectrometry (HPLC-MS). The retention time for 1, T1, T2 was
0
159.1) and 4-ethyl-4 -hydroxyethyl-bipyridinum radical cation
(MS (ESI, m/z): C14H17N O , calculated for 230.1, found, 230.1)
+ꢁ
2
1
1
1
1
1
07
08
09
10
11
(Fig. S11a in Supporting information). Along with the extension of
reaction time, other by-products could be ignored due to the little
yield. For 1 alone, most of the bromination products were
decomposed after the reaction lasted for 5 h. While, the folded
conformation of 1 in CB[8] provides a close interaction distance
2
+
112
between the phenoxy moiety and the EV moiety, which quite
facilitate the ICT [8]. So the bromination products of 1/CB[8] were
quite stable under the strongly acidic conditions, even for 5 h.
1
1
13
14
4
.98 min, 9.32 min, 13.10 min, respectively (Fig. S6 in Supporting
information). As shown in Table 1, the reaction products T1 and T2
Scheme 1. Schematic synthetic procedures of the bromination of 1 in the presence of CB[n] (n = 6–8).
0
0
Please cite this article in press as: T.-T. Li, et al., Bromination of N-phenyloxypropyl-N -ethyl-4,4 -bipyridium in cucurbit[8]uril molecular
reactor, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.10.004

G Model
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T.-T. Li et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
3
1
1
54
55
Absorption spectra were measured on a PerkinElmer Lambda
3
5 UV–vis spectrophotometer.
1
56
4
.2. Synthetic procedures
1
1
57
58
CB[n] (n = 6–8) was synthesized according to the literature [16].
The yield of CB[6], CB[7] and CB[8] was ca. 38%, 30% and 10%,
1
159
respectively. H NMR (400 MHz, D
2
O), CB[6]: d 5.82 (d, 12H,
1
1
1
60
61
62
J = 15.6 Hz), 5.55 (s, 12H), 4.23 (d, 12H, J = 15.6 Hz); CB[7]:
d
5.78 (d,
1
5
4H, J = 15.4 Hz), 5.54 (s, 14H), 4.24 (d, 14H, J = 15.4 Hz); CB[8]:
d
.72 (d, 16H, J = 15.4 Hz), 5.58 (s, 16H), 4.31 (d, 16H, J = 15.4 Hz).
0
0
163
64
165
N-Phenyloxyethyl-N -ethyl-4,4 -bipyridium (1): This com-
pound was synthesised according to the previous work [12].
1
1
The total yield of 1 was 30%. H NMR (400 MHz, D
.18 (d, 2H, J = 8.0 Hz), 9.10–9.08 (d, 2H, J = 8.0 Hz), 8.52–8.48 (m,
4H), 7.32–7.28 (t, 2H, J = 8.0 Hz), 7.02–6.98 (t, 1H, J = 4.0 Hz), 6.96–
.94 (d, 2H, J = 4.0 Hz), 5.13–5.10 (t, 2H, J = 4.0 Hz), 4.75–4.70 (q, 2H,
2
O), 1: d 9.20–
1
1
1
1
66
67
68
69
9
Q4
Fig. 2. Optimized molecular modeling of 1/CB[8] (left) and T1/CB[8] (right) with Br-
6
,
N-, C-, O- and H-atom in yellow, blue, cyan, red and white color, respectively. To
make clarity, CB[8] is presented in sticks, and 1, T1 are in balls and cylinders for a
clear view of the inclusion. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)
J = 4.0 Hz), 4.62–4.60 (t, 2H, J = 4.0 Hz), 1.67–1.64 (t, 3H, J = 4.0 Hz).
ꢀ 2+
170
171
HRMS: (m/z (%)): 153.0861 (100) [M ꢀ 2Cl ] (Calculated mass:
1
53.0868) (Synthetic procedures were shown in Supporting
1
1
72
73
information).
Bromination of 1 and 1/CB[n] (n = 6–8): Compound 1 (20 mg)
was dissolved in 250 mL water. In the case of the including
complexes, 20% excess of CB[n] was added to allow 1 to be
completely included. To ensure the bromination reaction
completely, 6 equiv. of bromine was added into the system. The
reaction was last for 10 min, 30 min, 2 h, 5 h, respectively. Then
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Control experiments were also carried out for the bromination
reaction of 1/CB[n] (n = 6, 7). The bromination result of 1/CB[n]
n = 6, 7) were presented in Table 1. Compared with the
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
(
bromination of 1 alone, the bromination of 1/CB[6] would produce
nearly 5% more T2 after the reaction lasted for 10 min. However,
along with the extension of reaction time, the bromination
products of 1/CB[6] are more likely to be decomposed (Fig. S9 in
Supporting information). And after the reaction lasted for 5 h, there
would be 83.0% by-products. This can be explained as follows.
Including of CB[6] keeps the phenoxy moiety a little far away from
the viologen cation moiety (Fig. S12 in Supporting information),
which somehow increases the electron density of phenoxy moiety.
Unfortunately, the host–guest assembly of 1/CB[6] would definite-
ly decrease the ICT interaction of 1, leading to the molecule to be
broken down easily.
In the case of 1/CB[7], the phenoxy moiety locates just outside
the cavity of CB[7], and the viologen cation moiety is completely
seated inside the cavity (Fig. S13 in Supporting information). The
ICT interaction between the viologen cation moiety and the
phenoxy moiety was decreased, when 1 was encapsulated in CB[7].
Although the yield of T2 can be improved, the decomposed
products also increase from 11.0% to 49.2%, when the reaction time
was prolonged from 10 min to 2 h. No further reaction was done
considering of the significant decomposition of 1/CB[7].
saturated NaHCO
neutral. The solution was concentrated to ca.10 mL and drop wised
into a saturated NH PF aqueous solution. The precipitate was
3
solution was added to adjust the solution to
4
6
collected and dried to give some crude product, which was
redissolved in anhydrous acetonitrile, an aliquot of the supernate
was injected into the HPLC systems to get final separation.
On HPLC system, a satisfactory separation was obtained using a
4
5
.6 mm ꢂ 250 mm ultimate XB-C18 column with a diameter of
m. Detection at 260 nm with a linear gradient containing
O (added 0.3% triethylamine and 0.3% acetic acid)
m
methanol/H
2
were found to be the most efficient eluents for this separation. In
the first 20 min, the water ratio was changed from 70% to 30%, and
then decreased from 30% to 0 in the later 10 min. The collection
time was 40 min. Under the circumstance, the retention time for 1,
T1, T2 was 4.98 min, 9.32 min, 13.10 min, respectively (Fig. S6).
194
Acknowledgments
Q3 195
This work was financially supported by State Key Laboratory of
Fine Chemicals, Dalian University of Technology, National Natural
Science Foundation of China (Nos. 21272030, 21472016, 21306019,
1
96
197
98
1
39
3
. Conclusion
1
21576042).
1
1
1
1
1
1
40 Q2
41
In conclusion, 1 can form a host–guest inclusion compound
199
with different CB[n] (n = 6–8) cavity through different binding
modes, and CB[8] works pretty well as a molecular reactor to
adjust the bromination results. Especially, CB[8] can provide a
quite safe bromination environment for 1. All these shed some new
light on CB[n] host–guest chemistry.
Appendix A. Supplementary data
42
43
200
201
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.cclet.2016.10.004.
44
45
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02
References
1
1
46
47
4
. Experimental
[1] J.W. Lee, S. Samal, K. Kim, et al., Cucurbituril homologues and derivatives: new
2
03
opportunities in supramolecular chemistry, Acc. Chem. Res. 36 (2003) 621–
4
.1. Materials and apparatus
204
05
6
30.
[
[
2] K. Kim, N. Selvapalam, D.J. Kim, et al., Functionalized cucurbiturils and their
applications, Chem. Soc. Rev. 36 (2007) 267–279.
3] (a) J. Lagona, P. Mukhopadhyay, L. Isaacs, et al., The cucurbit[n]uril family,
2
1
1
1
1
1
1
48
49
50
51
52
53
Doubly purified water used in all experiments was from Milli-Q
systems. Other solvents and reagents were of analytical grade and
206
207
208
Angew. Chem. Int. Ed. 44 (2005) 4844–4870;
(b) J.X. Cheng, L.L. Liang, Z. Tao, et al., Twisted cucurbit[14]uril, Angew. Chem.
125 (2013) 7393–7396.
1
used without further purification. H NMR spectra were recorded
on a VARIAN INOVA-400 spectrometer with chemical shifts
reported as ppm. Mass spectrometric data were obtained on a
Q-Tof MS spectrometer (Micromass, Manchester, England).
[4] (a) B. Zheng, F. Wang, F.H. Huang, et al., Supramolecular polymers constructed
209
210
by crown ether-based molecular recognition, Chem. Soc. Rev. 41 (2012) 1621–
1636;
0
0
Please cite this article in press as: T.-T. Li, et al., Bromination of N-phenyloxypropyl-N -ethyl-4,4 -bipyridium in cucurbit[8]uril molecular
reactor, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.10.004

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4
T.-T. Li et al. / Chinese Chemical Letters xxx (2016) xxx–xxx
2
2
2
2
2
2
2
2
11
12
13
14
15
16
17
18
(
b) S.Y. Dong, B. Zheng, F.H. Huang, et al., Supramolecular polymers
[11] (a) Z.S. Hou, Y.B. Tan, K. Kim, et al., Preparation of novel side-chain
pseudopolyrotaxanes consisting of cucurbituril[6] and polyamine salts,
Chin. Chem. Lett. 16 (2005) 1031–1034;
258
259
260
261
262
263
264
constructed from macrocycle-based host–guest molecular recognition
motifs, Acc. Chem. Res. 47 (2014) 1982–1994;
(
c) G. Yu, K. Jie, F.H. Huang, Supramolecular amphiphiles based on host–guest
molecular recognition motifs, Chem. Rev. 115 (2015) 7240–7303;
d) M.M. Zhang, X.Z. Yan, W. Harry, et al., Stimuli-responsive host–guest
(b) H.Y. Lu, J.R. Li, D.X. Shi, et al., A novel synthesis of nitroform by the nitrolysis
of cucurbituril, Chin. Chem. Lett. 26 (2015) 365–368;
(
(c) J.M. Yi, X. Xiao, Z. Tao, et al., Supramolecular self-assembly of cucurbit[8]uril
0
systems based on the recognition of cryptands by organic guests, Acc. Chem.
Res. 47 (2014) 1995–2005.
5] W.L. Mock, T.A. Irra, T.L. Manimaran, et al., Cycloaddition induced by
cucurbituril: a case of Pauling principle catalysis, J. Org. Chem. 48 (1983)
with 2, 2 -(heptane-1,7-dily) dibenzimidazolium chloride, Acta Chim. Sin. 72
(2014) 949–955;
2
65
[
(d) M. Zhang, J. Gao, Z.Y. Tian, et al., Enhanced dSTORM imaging using
fluorophores interacting with cucurbituri, Sci. China Chem. 59 (2016) 848–
852.
219
20
266
267
2
3
619–3620.
[
6] (a) J.W. Lee, K.P. Kim, K. Kim, et al., Unprecedented host-induced
intramolecular charge-transfer complex formation, Chem. Commun. (2002)
[12] T.Y. Zhang, S.G. Sun, X.J. Peng, et al., Redox-induced partner radical formation
and its dynamic balance with radical dimer in cucurbit[8]uril, Phys. Chem.
Chem. Phys. 11 (2009) 11134–11139.
[13] (a) L. Cera, C.A. Schalley, Stimuli-induced folding cascade of a linear oligomeric
guest chain programmed through cucurbit[n]uril self-sorting (n = 6, 7, 8),
Chem. Sci. 5 (2014) 2560–2567;
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
268
269
2
692–2693;
(
b) M. Pattabiraman, A. Natarajan, V. Ramamurthy, et al., Template directed
270
271
272
273
274
275
276
277
278
279
280
281
282
283
photodimerization of trans-1,2-bis(n-pyridyl)ethylenes and stilbazoles in
water, Chem. Commun. (2005) 4542–4544;
(
c) M. Pattabiraman, L.S. Kaanumalle, V. Ramamurthy, et al., Regioselective
(b) C. Hu, Y. Zheng, O.A. Scherman, et al., Cucurbit[8]uril directed stimuli-
responsive supramolecular polymer brushes for dynamic surface engineering,
Chem. Commun. 51 (2015) 4858–4860;
(c) E. Apple, M.J. Rowland, O.A. Scherman, et al., Enhanced stability and activity
of temozolomide in primary glioblastoma multiforme cells with cucurbit[n]
uril, Chem. Commun. 48 (2012) 9843–9845;
(d) Y.Y. Mao, K. Liu, T. Yi, et al., CB[8] gated photochromism of a diarylethene
derivative containing thiazole orange groups, Chem. Commun. 51 (2015)
6667–6669;
(e) E.A. Apple, J.D. Barrio, O.A. Scherman, et al., Metastable single-chain
polymer nanoparticles prepared by dynamic cross-linking with nor-seco-
cucurbit[10]uril, Chem. Sci. 3 (2012) 2278–2280.
photodimerization of cinnamic acids in water: templation with cucurbiturils,
Langmuir 22 (2006) 7605–7609;
(
d) N. Barooah, B.C. Pemberton, J. Sivaguru, et al., Photodimerization and
complexation dynamics of coumarins in the presence of cucurbit[8]urils,
Photochem. Photobiol. Sci. 7 (2008) 1473–1479;
(
e) L. Lei, L. Luo, C.H. Tung, et al., Cucurbit[8]uril-mediated photodimerization
of alkyl 2-naphthoate in aqueous solution, Tetrahedron Lett. 49 (2008) 1502–
505;
f) X.L. Wu, L. Luo, C.H. Tang, et al., Highly efficient cucurbit[8]uril-templated
1
(
intramolecular photocycloaddition of 2-naphthalene-labeled poly (ethylene
glycol) in aqueous solution, J. Org. Chem. 73 (2008) 491–494;
(
g) B. Chen, S.F. Cheng, L.Z. Wu, et al., Highly efficient cucurbit[8]uril-
templated intramolecular photocycloaddition of 2-naphthalene-labeled poly
ethylene glycol) in aqueous solution, Photochem. Photobiol. Sci. 10 (2011)
441–1444.
[14] (a) S. Choi, S.H. Park, K. Kim, et al., A stable cis-stilbene derivative encapsulated
284
285
286
in cucurbit[7]uril, Chem. Commun. (2003) 2176–2177;
(
1
(b) Y.H. Ko, K. Kim, K.J. Kim, et al., Designed self-assembly of molecular
necklaces using host-stabilized charge-transfer interactions, J. Am. Chem. Soc.
126 (2004) 1932–1937;
(c) Y. Ling, W. Wang, A.E. Kaifer, et al., A new cucurbit[8]uril-based fluorescent
receptor for indole derivatives, Chem. Commun. (2007) 610–612;
(d) W. Ong, A.E. Kaifer, Salt effects on the apparent stability of the
cucurbit[7]uril-methyl viologen inclusion complex, J. Org. Chem. 69 (2004)
1383–1385;
2
87
[
[
7] W. Lali, P. Petrovi ꢀc , J.P. Djukic, et al., The inhibition of iridium-promoted water
oxidation catalysis (WOC) by cucurbit[n]urils, Dalton Trans. 41 (2012) 12233–
2
2
42
43
288
289
12243.
2
90
8] (a) S.Y. Jon, Y.H. Ko, K. Kim, et al., A facile, stereoselective [2 + 2] photoreaction
244
245
246
247
248
249
250
251
252
253
291
292
293
294
295
mediated by cucurbit[8]uril, Chem. Commun. (2001) 1938–1939;
(
b) M. Pattabiraman, A. Pattabiraman, V. Ramamurthy, et al., Templating
photodimerization of trans-cinnamic acids with cucurbit[8]uril and
-cyclodextrin, Org. Lett. 7 (2005) 529–532;
c) R.B. Wang, L. Yuan, D.H. Macartney, et al., Cucurbit[7]uril mediates the
(e) J. Kim, I.S. Jung, K.J. Kim, et al., New cucurbituril homologues: syntheses,
isolation, characterization, and X-ray crystal structures of cucurbit[n]uril
(n = 5, 7, and 8), J. Am. Chem. Soc. 122 (2000) 540–541.
g
(
stereoselective [4 + 4] photodimerization of 2-aminopyridine hydrochloride in
aqueous solution, J. Org. Chem. 71 (2006) 1237–1239;
[15] (a) U. Rauwald, O.A. Scherman, Supramolecular block copolymers with
cucurbit[8]uril in water, Angew. Chem. Int. Ed. 47 (2008) 3950–3953;
(b) W. Wang, A.E. Kaifer, Electrochemical switching and size selection in
cucurbit[8]uril-mediated dendrimer self-assembly, Angew. Chem. Int. Ed. 45
(2006) 7042–7046.
296
297
298
299
(
d) B.C. Pemberton, N. Barooah, J. Sivaguru, et al., Supramolecular
photocatalysis by confinement—photodimerization of coumarins within
cucurbit[8]urils, Chem. Commun. 46 (2010) 225–227.
[
9] A.L. Koner, C. Márquez, W.M. Nau, et al., Chemoselektive photoreaktionen
mithilfe von übergangsmetallen in cucurbiturilen, Angew. Chem. Int. Ed. 50
[16] J.W. Lee, I. Hwang, K. Kim, et al., Synthetic molecular machine based on
reversible end-to-interior and end-to-end loop formation triggered by
electrochemical stimuli, Chem. Asian J. 3 (2008) 1277–1283.
[17] A. Day, A.P. Arnold, B.J. Snushall, et al., Controlling factors in the synthesis of
cucurbituril and its homologues, J. Org. Chem. 66 (2001) 8094–8100.
2
2
54
55
300
301
(
2011) 545–548.
[
10] T. Fuenzalida, D. Fuentealba, A study of the Fenton-mediated oxidation of
2
2
56
57
302
methylene blue–cucurbit[n]uril complexes, Photochem. Photobiol. Sci. 14
(
2015) 686–692.
0
0
Please cite this article in press as: T.-T. Li, et al., Bromination of N-phenyloxypropyl-N -ethyl-4,4 -bipyridium in cucurbit[8]uril molecular
reactor, Chin. Chem. Lett. (2016), http://dx.doi.org/10.1016/j.cclet.2016.10.004