Dynamic self-inclusion behavior of pillar[5]arene-based pseudo[1]rotaxanes

Article abstract of DOI:10.1039/c3ob42044b

It was found that spontaneous isomerization takes place between three isomers of a pillar[5]arene (P5)-based pseudo[1]rotaxane. The isomerization process could be monitored by ¹H NMR spectra in polar solvent and the geometric configurations of the three isomers were further evaluated by theoretical calculations. In the threaded forms, the alkyl side chain might be preorganized by intramolecular N-H...O bonds between the urea group of the side chain and the methoxy group of the P5 and further stabilized by multiple interactions, including H-bonding, C-H...π interactions, and the steric effect of the N-Boc moiety. These cooperative interactions greatly enhance the stability of the threaded form in polar solvent, and endow it with very special self-inclusion behavior. The Royal Society of Chemistry.

Full text of DOI:10.1039/c3ob42044b

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Dynamic self-inclusion behavior of pillar[5]arene-
based pseudo[1]rotaxanes†
Cite this: DOI: 10.1039/c3ob42044b
Yangfan Guan,a Pingying Liu,b Chao Deng,a Mengfei Ni,a Shuhan Xiong,a Chen Lin,a
Xiao-Yu Hu,*a Jing Ma*b and Leyong Wang*a
It was found that spontaneous isomerization takes place between three isomers of a pillar[5]arene (P5)-
based pseudo[1]rotaxane. The isomerization process could be monitored by 1H NMR spectra in polar
solvent and the geometric configurations of the three isomers were further evaluated by theoretical cal-
culations. In the threaded forms, the alkyl side chain might be preorganized by intramolecular N–H⋯O
bonds between the urea group of the side chain and the methoxy group of the P5 and further stabilized
by multiple interactions, including H-bonding, C–H⋯π interactions, and the steric effect of the N-Boc
moiety. These cooperative interactions greatly enhance the stability of the threaded form in polar solvent,
and endow it with very special self-inclusion behavior.
Received 12th October 2013,
Accepted 18th November 2013
DOI: 10.1039/c3ob42044b
www.rsc.org/obc
by intramolecular H-bonding, leading to the formation of a
pseudo[1]rotaxane structure, which will accelerate the aminoly-
Introduction
Among various interlocked architectures,1 pseudo[1]rotaxane sis by enhancing the stability of the intermediate. Ogoshi’s
is a special type of supramolecular system that contains both work10 had shown that an octyltrimethyl ammonium functio-
the wheel and axle in one molecule, with a fast or slow nalized P5 predominantly formed a self-inclusion complex
exchange process between threaded and open forms. The structure in CHCl3. However, previously reported pseudo[1]-
threaded structure of pseudo[1]rotaxane has been successfully rotaxanes shared the following characteristics: (1) it is difficult
proved by many researchers via spectroscopic measurements,2 or impossible to separate the open and threaded forms of a
solid structure analysis3 or the introduction of a stopper unit pseudo[1]rotaxane due to their dynamic behavior; (2)
to form the [1]rotaxane.4 In particular, pseudo[1]rotaxanes and especially, a highly polar solvent would prevent H-bond or
[1]rotaxanes can be extensively used as molecular machines to C–H⋯π interactions between the alkyl chain and P5 cavity.
show corresponding responses to some specific stimuli due to Thus pillararene-based pseudorotaxanes in polar solvent have
their reversible conversion behavior, and many functionalized been the subject of only a few reports.7a,11 (3) In general, the
macrocyclic molecules have been synthesized for this large stoppers in the axle keep the axle from being included
purpose.4b,5
Ever since the discovery of pillararene,6 pillar[5]arenes (P5)
into the P5 cavity due to their steric effect.
On the basis of our previous study of the pseudo[2]rotax-
continue to be attractive wheel components in constructing anes assembled by urea-modified pillar[5]arene and linear
interlocked assemblies, and various pillararene-based pseudo- guests,11,12 we describe here the preparation of an unconven-
rotaxanes with diverse functions have been reported in the last tional pseudo[1]rotaxane, whose pure open and threaded
few years.7 For example, Cao and co-workers8 reported that forms could be isolated by column chromatography tempor-
pillar[5]arene-based pseudorotaxanes selectively bound di- arily. In particular, the pure open and threaded forms could
halogen alkanes in non-polar solvent. Hou et al.9 reported that both spontaneously and slowly isomerize into the other as well
the amide group was introduced to the side-chain of P5 to as the third isomer in polar solvent (DMSO) and reached equi-
tune the resulting axle toward the inner space of the P5 cavity librium after four months at 20 °C. Moreover, the influence of
the stopper size and urea moiety on the self-inclusion behavior
of pseudo[1]rotaxanes in our case was discussed in detail,
aKey Laboratory of Mesoscopic Chemistry of MOE, Center for Multimolecular
Chemistry, School of Chemistry and Chemical Engineering, Nanjing University,
Nanjing 210093, China. E-mail: huxy@nju.edu.cn, lywang@nju.edu.cn
where, especially, the size of the N-Boc stopper cooperating
with other non-covalent interactions could enhance the stabi-
lity of the self-inclusion structure, instead of preventing the
self-inclusion of the axle. In addition, the formation pathway
of this pseudo[1]rotaxane is also proposed and supported by
control experiments.
bInstitute of Theoretical and Computational Chemistry, Nanjing University, Nanjing
210093, China. E-mail: majing@nju.edu.cn
†Electronic supplementary information (ESI) available: 1H and 13C NMR spectra
and theoretical calculation data. See DOI: 10.1039/c3ob42044b
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Initially, the structural characterization of the pure major
product 1u and minor product 1conf1 was investigated by NMR
spectroscopy. After four days, 1H NMR spectra of both pro-
Results and discussion
Synthesis, isolation, and structural characterization of 1conf1/1u
According to the literature method,13 amino-functionalized ducts became complicated with new peaks appearing com-
pillar[5]arene 8 was reacted with the di-substituted amine 9 in pared to the freshly purified ones. Hence, in order to achieve
chloroform at 25 °C for 24 h, and then one major product 1u their pure spectra, NMR experiments were carried out within
together with a small fraction of the minor product 1conf1 were 6 h after the pure product was isolated by column chromato-
observed as two independent spots on TLC, and then the pure graphy, and full characterization of 1u and 1conf1 by NMR spec-
1u and 1conf1 were obtained by column chromatography, troscopy was accomplished always with freshly purified
respectively (yields of 56% for 1u, 6% for 1conf1) (Fig. 1A), products. Since the urea protons of 1u and 1conf1 both disap-
where the major product 1u was expected to be a non- peared in their 1H NMR spectra in CDCl3 and their alkyl chain
inclusion complex and the minor product 1conf1 could be an signals became broad as well, all their characterizations were
1
unexpected inclusion complex.
then carried out in DMSO-d6. Based on their H NMR spectra,
the major product 1u differs from the minor product 1conf1
mainly in two regions (Fig. 1B): (1) the two urea proton peaks
of 1u are adjacent (6.02 and 5.92 ppm); but in the spectrum of
1conf1, Hc shifts downfield to 6.4 ppm, while the other one Hd
is located at 5.90 ppm, suggesting that Hc of the ureido might
be involved in stronger H-bonding interactions than Hd. (2) In
the spectrum of 1u, no peak can be obviously observed in the
range of 0.5 to −2.0 ppm, suggesting the side chain of 1u devi-
ates from the macrocycle cavity, which confirmed that 1u was
a non-inclusion complex as expected. In the spectrum of
1conf1, the four peaks corresponding to the four methylene
protons Hh, Hi, Hk and Hj (−0.43, −0.91, −1.33, and
−1.65 ppm) were remarkably observed in the high field,
whereas He and Hf of the alkyl side chain were observed with a
slight upfield shift compared to 1u. These results indicated
that the four methylene protons Hh, Hi, Hk and Hj in 1conf1
were located in the central position of the P5 cavity to achieve
an inclusion complex, and He of the methylene connecting to
urea moiety stayed outside the P5 cavity.
The above 1H NMR spectra undoubtedly reveal the
inclusion structure of 1conf1. However, is this inclusion struc-
ture a self-inclusion or interpenetration structure? In other
words, does 1conf1 exist as a pseudo[1]rotaxane structure,
dimers, trimers, or n-mers in polar solvent? In order to resolve
this structural question, we first measured the 1H NMR spectra
of 1conf1 at different concentrations in the range of 1.0–60 mM
1
(Fig. S2†), which showed that the H NMR spectra of 1conf1 is
concentration independent, suggesting that 1conf1 exists predo-
minantly in the form of the pseudo[1]rotaxane or cyclic oligo-
mer in polar solvent. Subsequently, high resolution
electrospray ionization mass spectrometry (HR-ESI-MS) investi-
gation was performed, in which two indicative peaks corres-
ponding to [M + H]+ at m/z 1050.5686 and [M + Na]+ at m/z
1072.5504 were clearly observed and no other peaks corres-
ponding to higher molecular weight interlocked structures
were observed, confirming the presence of 1conf1 as the
pseudo[1]rotaxane structure. The 2D ROESY spectrum of 1conf1
exhibits clear NOE correlations between protons Hf, Hg, Hh,
Hi, Hj, Hk of the aliphatic chain and the methoxy protons Ho
(Fig. 1C, cross-peaks I) and the aromatic protons Hq of P5
(Fig. 1C, cross-peaks II), also supporting the formation of the
self-inclusion structure of 1conf1. Furthermore, the ROESY
spectrum of 1conf1 displayed very clear NOE correlations
Fig. 1 (A) Schematic representation of the synthesis of 1conf1 and 1u; (B)
1H NMR spectrum of 1conf1 and 1u (400 MHz, DMSO-d6, 298 K), the
peaks marked with * are ascribed to DMSO-d6; (C) Partial 2D ROESY
spectrum of 1conf1 (400 MHz, DMSO-d6, 298 K).
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between protons Hc and Hd of the urea group and protons Ho implying that the system of the self-inclusion structures 1conf1
,
of the methoxy moiety, respectively, as well as between protons 1conf2 and the non-inclusion structure 1u reached equilibrium
Hm of the amide group of N-Boc and protons Ho of the at 20 °C in DMSO-d6, where the open structure 1u and self-
methoxy moiety (Fig. S3,† cross-peaks III). These correlations inclusion structure 1conf2 were both transformed from self-
indicated that 1conf1 was possibly stabilized by two types of inclusion structure 1conf1
.
N–H⋯O bonds, one between the N-Boc moiety and the Subsequently, the transformation from pure non-inclusion
methoxy group of P5, and the other between the urea group structure 1u into 1conf1 and 1conf2 was able to be similarly
and the methoxy group of P5.
observed from the time-dependent 1H NMR spectra of pure
non-inclusion structure 1u in DMSO-d6 at 20 °C (Fig. 2E–2H).
The pure non-inclusion compound 1u showed no signal in the
Transformations between 1conf1, 1conf2 and 1u
As mentioned above, we found that pure 1conf1 or 1u gradually high field of 1H NMR spectra, but after 141 h, two new and
turned into mixtures of isomers in DMSO after days, where, independent sets of signals in the high field of 1H NMR
interestingly, the third isomer 1conf2 could be observed but spectra corresponding to 1conf1 and 1conf2 were observed with
could not be isolated by column chromatography. Initially, the peak integration ratio of 1 : 25 (Fig. 2F, colored in red and
time-dependent 1H NMR of sample 1conf1 was performed to green, respectively), which then changed into 1 : 4 after 261 h.
investigate the transformation of pure 1conf1 to 1u and the
We have deduced the formation of two types of hydrogen
third isomer 1conf2 (Fig. 2A–2D) in DMSO-d6 at 20 °C. We bonds between the urea/amide group and the methoxy group
found that after 77 h (Fig. 2B), two new peaks at 6.15 and in 1conf1, and it is well known that the fluoride ion shows a
6.00 ppm (colored in purple) corresponding to the urea strong binding ability to N–H bonds even in polar solvents,14
protons Hc and Hd of 1u (colored in purple) appeared and the therefore, we added fluoride ions into the solution of 1conf1 to
peak intensity of 1conf1 (colored in red) decreased to 91% of its investigate the effect of fluoride ions in our system. At the
initial value (based on the peak integration of Hg). Moreover, beginning, the spectrum of pure 1conf1 showed only one set of
another set of peaks (0.51, −0.07, −0.81, −1.82, −1.95 ppm, peaks for Hg–j in the high field (Fig. 3A, colored in red). After
colored in green) that we assigned to the third isomer 1conf2 165 h, the peaks assigned to 1conf2 (Fig. 3B, colored in green)
emerged, which could be another conformation of a self- and 1u (Fig. 3B, colored in purple) were observed, indicating
inclusion structure different from 1conf1. After 289 h (Fig. 2C), 1conf1 partially transformed into 1conf2 and 1u as mentioned
the newly appeared urea protons Hc and Hd of 1u became above. Then an excess amount of tetra-n-butylammonium fluo-
broad and the peak intensity of 1conf1 decreased to 30% of its ride salt was added into the NMR tube, and the resulting spec-
initial value in the spectra, where the molar ratio of 1u/1conf1
/
trum is shown in Fig. 3C: in the low field, the urea proton Hd
1conf2 was calculated by the peak integration to be 55/30/15. and the amide proton Hm of 1conf1 together with the urea
After 4 months, the peak intensity of Hg of 1conf1 still kept 24% proton Hd of 1u shifted downfield to ∼7.7, 6.4, 8.2 ppm and
of its initial value (Fig. 2D) in the spectra, where the molar became broad, while the urea proton Hc of 1conf1 remained
ratio of 1u/1conf1/1conf2 was then calculated to be 60/24/16, unchanged due to the stable intramolecular H-bonding, and it
Fig. 2 Time-dependent transformation of 1conf1 and 1u monitored by 1H NMR spectra (400 MHz, DMSO-d6, 298 K). (A) compound 1conf1, (B) 1conf1
after 77 h, (C) 1conf1 after 289 h, (D) 1conf1 after 4 months, (E) compound 1u, (F) 1u after 141 h, (G) 1u after 261 h, and (H) 1u after 4 months. The color
of the proton signals were in accordance with 3D cartoon models: 1conf1 in red, 1u in purple and 1conf2 in green.
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Fig. 3 Fluoride ion induced transformation from 1conf1 to 1conf2 monitored by 1H NMR spectra (400 MHz, DMSO-d6, 298 K). (A) Pure compound
conf1, (B) 1conf1 after 165 h, and (C) upon addition of excess amount of tetra-n-butylammonium fluoride salt.
1
was overlapped with the downfield shifted proton Hm of 1conf1
;
the amide group of N-Boc and the urea group of the alkyl side
in the high field (from 0.5 to −2.0 ppm), the signals of 1conf1 chain formed two types of H-bonds with the methoxy group of
disappeared upon addition of F− and the resulting signals P5, resulting in a “loosen” style conformation; while in 1conf2
were highly similar to that of 1conf2. Based on these obser- the stronger hydrogen bonds between the inverted urea of the
vations, it seemed that the fluoride ion functioned as an accel- alkyl side chain and P5 forced the alkyl side chain more deeply
erator for the transformation from 1conf1 to 1conf2, probably to thread into the cavity of P5, making the N-Boc end of the
because fluoride ions could strongly bind Hm of the amide side chain stay away from the rim of P5 with the hydrogen
group forcing the end of the axle of 1conf1 to slip away from the bonds between the alkyl side chain and P5 no longer present.
rim of the cavity to achieve another self-inclusion isomer, Thus the conformation of 1conf2 could be described as a “con-
1conf2, where the H-bonds between the amide group and tract” style. Probably, the tension of the urea group in 1conf1 is
methoxy groups of P5 were broken by F− but Hc of the urea the driving force for the transformation of 1conf1 to 1conf2. In
group maintained its intramolecular H-bonds with the addition, the results showed that 1conf1 is the most stable among
methoxy group of P5.
the three isomers 1conf1, 1conf2 and 1u (Table S1†), and the energy
Therefore, on the basis of these experimental data, theore- of 1conf2 is only 3.38 kcal mol−1 higher than 1conf1, which prob-
tical calculations for the conformations of 1conf1, 1conf2 and 1u ably could explain the reason why 1conf1 and 1conf2 exist as confor-
were carried out with the Gaussian 09 program package15 to mational isomers but 1conf2 could not be separated. The
optimize the conformations of 1conf1 and 1conf2 (Fig. 4) and calculated 1H NMR chemical shifts of 1conf1 are in accordance
1
further compute the H NMR chemical shifts and vibrational with its experimental data (Fig. S65a†), and the calculated chemi-
frequencies using density functional theory (DFT) with the cal shifts of 1conf2 are quite different from the experimental
M062X functional and the 6-31G(d,p) basis set. The theoretical results of 1conf1 (Fig. S65b†), supporting the different confor-
calculation results supported the conformations of 1conf1 and mations between 1conf1 and 1conf2. Moreover, the calculated 1H
1conf2 (Fig. 4): the two N–H bonds of the urea group oriented NMR spectrum of 1u and IR spectrum of 1conf1 are also consist-
in opposite directions in both 1conf1 and 1conf2 due to the intra- ent with their experimental data (Fig. S66 and S67†).
molecular hydrogen bonds. The difference between confor-
mation 1conf1 and 1conf2 was caused by the different hydrogen
Influence of the stopper size on self-inclusion behavior
bonding sites between the alkyl side chain and P5: in 1conf1
,
For the pillar[5]arene-based AB type derivatives which contain
a P5 macrocycle and a side chain with a stopper at the end,
“small” size stoppers (such as a bipyridine moiety and an alkyl
chain) only formed un-interlocked pseudorotaxanes with fast
rates of the alkyl chain’s slipping in and out, while “large” size
stoppers (such as the adamantyl group,16 3,5-di-tert-butylben-
zene,17 3,5-dinitrobenzene,18 and ureidopyrimidinone motif19)
prevented the side chain from threading or dethreading. The
tert-butoxy carbonyl group in 1conf1 is a middle sized stopper,
therefore, does this specific size contribute to the stability of
the self-inclusion structure 1conf1? With this thought, the N-
Boc stopper in 1conf1 was replaced by other functional groups
with different sizes (Scheme 1).
Fig. 4 The optimized geometries of the pseudo[1]rotaxane 1conf1 (left)
and 1conf2 (right) at the M062X/6-31G(d,p) level using the PCM model
(only the hydrogen atoms involved in H-bonding are shown for clarity).
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larger stopper, 3,5-di-tert-butylbenzyl chloride, in chloroform
to give the self-interlocked [1]rotaxane 5 in 26.6% yield, and
the transformation of self-interlocked [1]rotaxane 5 into the
corresponding open form was not observed. As a result, suc-
cessful preparation of this self-locked [1]rotaxane 5 confirmed
that compound 3 could form a relatively stable self-inclusion
structure in chloroform.
Therefore, all the above results have shown that the N-Boc
moiety is one of the key factors for the formation of the self-
Scheme 1 Chemical structures of pseudo[1]rotaxanes with different inclusion structure 1conf1. With larger or smaller size stoppers,
stoppers and their calculated stopper sizes.
the dynamic transformation between the self-inclusion and
non-inclusion structure could not be observed in DMSO-d6.
The size of the tert-butoxy carbonyl moiety (∼2.9 Å) is between
the amino/acetyl group (∼2.3 Å) and the 3,5-di-tert-butylbenzyl
group (∼9.8 Å), which makes the axle of 1conf1 possible but
laborious to thread into or dethread from the P5 cavity
(internal cavity diameter 4.7 Å22). When the axle is encapsu-
lated by the P5 cavity, it will be stably trapped in the cavity
under the cooperative interactions of the steric effect from the
bulky N-Boc moiety and the other non-covalent interactions,
thus the self-inclusion form 1conf1 is more stable than conven-
tional pseudo[1]rotaxanes.
Firstly, deprotection of the N-Boc moiety of the isomer
mixture of 1u/1conf1/1conf2 in an acidic medium generated the
amino-substituted compound 3, and the self-inclusion and
non-inclusion analogues of 3 cannot be separated any more
due to the fast rates of the alkylamino chain’s slipping in and
out. Huang et al. have reported that an amino-modified co-
pillar[5]arene with ten methylene groups tends to form cyclic
dimers in CDCl3 at low temperature (−35 °C).20 But for com-
pound 3, in polar solvent DMSO-d6 (Fig. 5B), the chemical
shifts of the alkyl side chain protons were the same as for free
1,8-diamino octane in DMSO-d6 (Fig. 5C), indicating that the
alkyl side chain did not thread into the cavity of P5. However,
in CDCl3 the alkyl side chain protons of compound 3 shifted
upfield (0.75–0 ppm) and became broad (Fig. 5A), suggesting
that compound 3 existed as the self-inclusion and non-
inclusion isomers with fast exchange rates on the NMR time
scale in CDCl3, which was also supported by the concen-
tration-dependent 1H NMR spectra of 3 in CDCl3 (Fig. S5†).
The self-inclusion structure of compound 3 in CDCl3 could be
totally destroyed in DMSO-d6 to transform into the non-
inclusion structure. When the amino group was replaced by a
methyl carbonyl group, similar to 3, the inclusion behavior of
4 is also solvent dependent (Fig. S6†): in CDCl3, the protons of
the alkyl chain of 4 shifted upfield and became broad, while in
DMSO-d6 the inclusion structure could not be formed.
Function of the urea moiety in the self-inclusion structure
Since the function of the N-Boc moiety has been revealed, we
then focus on the function of the urea moiety in the self-
inclusion structure 1conf1. Previously, Hou et al.9 reported that
a pillar[5]arene bearing an amide group on the side chain
could form intramolecular hydrogen bonds on the rim of P5
and tuned the side chain into a self-inclusion conformation in
the solid state. The position of the N–H bond of the amide
group in P5 is similar to the urea moiety in our case. This
inspired us to further investigate the effects of the urea group
of the alkyl side chain of 1conf1, which might also play an
important role in the formation of the self-inclusion structure
by intramolecular hydrogen bonding. As discussed above, both
1conf1 and 1conf2 contain intramolecular H-bond between the
urea moiety and the methoxy group of P5, therefore, with the
aim of weakening the intramolecular H-bond via lengthening
the distance between the P5 skeleton and the urea moiety
from two to four methylenes, compound 2/2u was synthesized.
It was found that the minor product self-inclusion form 2 and
major product non-inclusion form 2u (Scheme 2) could also
In order to further confirm the self-inclusion structure16,21
of compound 3 in chloroform, compound 3 was reacted with a
Fig. 5 1H NMR spectra (300 MHz, 298 K) of (A) 3 in CDCl3, (B) 3 in
DMSO-d6, and (C) 1,8-diamino octane in DMSO-d6.
Scheme 2 Chemical structures of compounds 2, 2u and 6.
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be obtained and isolated via column chromatography in 4% intramolecular H-bonds. Based on the 1H NMR spectra, the
and 62% yields, respectively. transformation between 2 and 2u (Fig. S8†) in DMSO was
Comparing the chemical shifts of the urea protons of com- much simpler compared to both 1conf1 and 1u because the
pounds 1conf1, 1u, 2, and 2u (Fig. 6A–6D), it is interesting to third isomer could not be observed in this case. Dethreading
note that the two urea peaks of the open form 1u or 2u are behavior of 2 occurred at an extremely slow rate at around
adjacent in the spectra, while the urea peaks of compound 20 °C in DMSO, and after 50 days the threaded methylene
1conf1 showed a much lower shift for Hc (6.43 ppm) than Hd signals Hi could hardly be identified any more (spectrum f in
(5.90 ppm), indicating Hc forms intramolecular hydrogen Fig. S8†), suggesting that the self-inclusion structure of 2
bonds with oxygen-donor atoms in 1conf1. In the spectrum of 2, becomes relatively unstable in polar solvent after lengthening
He (6.43 ppm) is only 0.28 ppm lower than Hf (5.89 ppm), the distance between the urea moiety and the P5 cavity.
which could be interpreted as that increasing the length
Furthermore, another pillar[5]arene derivative 6 (Scheme 2)
between the urea moiety and the P5 backbone weakened the without the urea moiety on the alkyl side chain was syn-
thesized and further investigated. It could form the self-
inclusion structure only in CDCl3 as indicated by four peaks in
the upfield region from 0.5 to −2.0 ppm (Fig. 7A), while the
inclusion structure was totally destroyed in DMSO-d6 (Fig. 7B).
This phenomenon also confirmed that the urea moiety plays
an important role in the self-inclusion behavior of 1conf1 and
1conf2 by intramolecular hydrogen bonding between the urea
moiety and methoxy groups of P5.
The formation pathway of the threaded form 1conf1
We proposed three possible pathways for the formation of the
pseudo[1]rotaxane product 1conf1 (Fig. 8): (Path I) a Reaction-
Followed-By-Threading process, which means the carbonyl
imidazolium reacts with the amino group first to form the
urea moiety outside the P5 cavity, then the N-Boc side chain
threads into the cavity and is further stabilized by the hydro-
gen bonding and multiple C–H⋯π interactions. In order for
the molecule to transform slowly from 1u to 1conf1, the tert-
butyl group must overcome the confines of the limited pillar-
shaped cavity. (Path II) A Threading-Followed-By-Reaction
process, which means 1conf1 was produced from the in situ gen-
erated pseudo[2]rotaxane 8 . 9. (Path III) Unit tumbling,23
Fig. 6 The urea proton signals of (A) 2u, (B) 2, (C) 1u, and (D) 1conf1 in
1H NMR spectra (400 MHz, DMSO-d6, 298 K). The value of the chemical
shift (ppm) is labeled above in blue.
Fig. 7 1H NMR spectra of 6 in (A) CDCl3 and (B) DMSO-d6 (400 MHz, 298 K).
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Fig. 8 Proposed pathways for the formation of pseudo[1]rotaxane.
meaning that the unthreaded 1u is converted into pseudo[1]- experiments on appropriate-size stoppers, we found that the
rotaxane through tumbling of the hydroquinone unit. cooperative effect of the steric N-Boc moiety, intramolecular
In order to reveal the real path of our case, we designed a hydrogen bonding of the urea moiety and other non-covalent
control experiment, in which compound 11 with the bulky tri- interactions were the essential factors for this special thread-
phenylchloromethyl moiety taking the place of the N-Boc pro- ing phenomenon in polar solvent. The discovery of this
tection moiety was reacted with compound 8 (Scheme 3). If dynamic pseudo[1]rotaxane 1conf1 represents a special type of
path (II) or (III) is possible, [1]rotaxane-like compound 7 is envi- inclusion phenomenon, and further studies on the controlla-
sioned as one of the product. However, it turned out that only ble switch of the pseudo[1]rotaxane through anions and com-
the unlocked product 7u was obtained in a yield of 44.1%, and petitive guests are now ongoing in our lab.
no trace of 7 was observed. This result supported that the for-
mation of 1conf1 is a Reaction-Followed-By-Threading process.
Experimental
Materials and methods
Conclusions
All reactions were performed under the atmosphere unless
In summary, we reported the preparation of an unconventional noted. Commercially available reagents and solvents were
pseudo[1]rotaxane, whose threaded form 1conf1 and open form employed without further purification. 1H NMR spectra were
1u could be isolated temporarily, and the self-inclusion struc- recorded at 300 and 400 MHz and are reported relative to deut-
ture of 1conf1 was proved via HR-ESI-MS, varying concentration erated solvent signals. Data for 1H NMR spectra are reported
1H NMR, and 2D ROESY NMR measurements. Different from as follows: chemical shift (δ, ppm), multiplicity, coupling con-
previously reported pseudo[1]rotaxanes, it could be clearly stant (Hz), and integration. Splitting patterns are designated
observed from the NMR spectra that 1u and 1conf1 both could as follows: s, singlet; d, doublet; t, triplet; q, quartet; m, multi-
spontaneously and slowly isomerize into mixtures of 1u, 1conf1 plet; and br, broad. 13C NMR spectra were recorded at 75 and
and the third newly appeared threaded form 1conf2 in polar 100 MHz. Data for 13C NMR spectra are reported in terms of
solvent DMSO, respectively. The conformations of 1u, 1conf1 chemical shift. The chemical shifts are reported in parts per
and 1conf2 were further evaluated and supported by compu- million (δ, ppm). The Fourier transform infrared (FTIR)
tational calculations. In the following series of control samples were prepared as thin films on KBr plates, and
Scheme 3 Control experiment.
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spectra were recorded on a spectrometer and are reported in 28.8, 28.2, 26.4, 26.2. HR-ESI-MS: m/z calcd for C62H83N3O13
terms of frequency of absorption (cm−1). Thin-layer chromato- [M]+ 1077.5926, found [M + H]+ 1078.6008.
1
graphy (TLC) was carried out using precoated silica gel sheets.
2u: mp 109–111 °C. H NMR (400 MHz, DMSO-d6, 298 K) δ
Flash chromatography was performed with silica gel (ppm) = 6.79–6.76 (m, 10H), 5.80 (s, 1H), 5.72 (s, 1H), 3.82 (s,
(200–300 mesh) with compressed air. Compounds not men- 2H), 3.74–3.66 (m, 37H), 3.06 (s, 2H), 2.94 (s, 1H), 2.88 (s, 1H),
tioned in the manuscript are the synthetic precursors: com- 1.74 (s, 2H), 1.60 (s, 2H), 1.37 (s, 9H), 1.22–1.16 (m, 10H). 13C
pound 10 is the precursor of 9, compound 12 is the precursor NMR (100 MHz, DMSO-d6, 298 K) δ (ppm) = 158.0, 149.8,
of 11, compounds 13–15 are the precursors of 2/2u, com- 149.6, 127.5, 127.4, 127.2, 114.1, 113.2, 95.4, 79.2, 77.2, 71.7,
pounds 16–18 are the precursors of 6. See the ESI† for details.
Pseudo[1]rotaxane 1conf1/1u. The procedure for reacting imi- identical in the ESI-MS spectrum.
dazolides with amine is exemplified by the synthesis of mono- Pseudo[1]rotaxane 3. Removal of the Boc-protecting groups
functional ureidopyrimidinone.13 Compound (0.4 g, with TFA was performed according to the literature method.24
67.6, 55.3, 54.9, 50.6, 30.1, 28.8, 28.2, 28.0, 26.4. 2u and 2 are
9
1.18 mol) and 8 (0.858 g, 1.1 mmol) were dissolved in CHCl3 A solution of 1conf1/1u (1.34 g, 1.27 mmol) and trifluoroacetic
(20 mL) and this solution was stirred overnight under nitrogen acid (5 mL) in dichloromethane (10 mL) was stirred for 12 h,
at 25 °C. The reaction mixture was washed with saturated the acid and dichloromethane were removed by evaporation in
NaHCO3 solution (20 mL) and brine (20 mL). After drying with vacuo. The dark green oil like crude product was dissolved in
Na2SO4, the organic layer was removed by evaporation in vacuo. dichloromethane (10 mL) again and washed with saturated
Column chromatography was used in the final separation with NaHCO3 solution (2 × 20 mL). After drying with Na2SO4, the
CH2Cl2–CH3OH (140 : 1, v/v) as the eluent, to give 1u (0.647 g, solvent was removed and the residue was purified by column
56%) and 1conf1 (0.070 g, 6%) as white solid.
chromatography on silica gel (CH2Cl2–CH3OH v/v = 40 : 1–1 : 1)
1conf1: FT IR (KBr) ν (cm−1) = 3417.2, 3370.6, 2933.4, 2847.2, to give 3 as a white solid (0.83 g, 68.9%). Mp 111–114 °C. H
2834.9, 2482.1, 2147.7, 2039.6, 1713.7, 1643.3, 1561.5, 1560.1, NMR (400 MHz, DMSO-d6, 298 K): δ (ppm) = 7.75 (s, 2H),
1497.4, 1465.9, 1397.7, 1364.9, 1214.8, 1172.4, 1048.9, 882.4, 6.80–6.60 (m, 10H), 6.08 (s, 1H), 5.98 (s, 1H), 3.77 (m, 2H),
774.8, 702.9, 647.6. 1H NMR (400 MHz, DMSO-d6, 298 K) 3.68–3.63 (m, 37H), 3.39 (m, 2H), 2.97 (s, 2H), 2.73 (s, 2H),
δ (ppm) = 6.84–6.79 (m, 10H), 6.43 (s, 1H), 5.89 (s, 1H), 1.51–1.18 (m, 12H). 13C NMR (100 MHz, DMSO-d6, 298 K) δ
4.51–4.46 (d, 1H), 3.85 (s, 2H), 3.75–3.63 (m, 37H), 3.50 (t, (ppm) = 158.1, 150.0, 149.98, 149.94, 149.89, 149.85, 149.1,
J = 4.7 Hz, 2H), 2.81 (m, 2H), 1.48 (s, 2H), 1.40 (s, 9H), 0.85 (s, 127.8, 127.6, 127.50, 127.45, 127.41, 127.35, 114.4, 113.6,
2H), 0.16 (s, 2H), −0.44 (s, 2H), −0.91 (s, 2H), −1.32 (s, 2H), 113.24, 113.16, 113.08, 79.2, 68.0, 55.4, 55.3, 41.2, 32.5, 30.0,
−1.65 (s, 2H). 13C NMR (100 MHz, DMSO-d6, 298 K) δ (ppm) = 29.1, 29.0, 28.95, 28.90, 28.84, 28.77, 28.71, 26.4, 26.1.
158.4, 156.6, 155.5, 154.5, 149.92, 149.87, 149.7, 149.6, HR-ESI-MS m/z: calcd for C55H71N3O11 [M]+ 949.5089, found
149.0, 148.8, 127.5, 127.2, 127.1, 113.3, 112.8, 112.4, 95.4, 77.2, [M + H]+ 950.5419.
1
77.1, 55.39, 55.32, 51.5, 30.6, 29.9, 29.4, 28.9, 28.7, 28.2, 28.1,
Pseudo[1]rotaxane 4. A solution of 3 (0.3 g, 0.32 mmol) and
27.0, 26.2, 24.8 ppm. HR-ESI-MS: m/z calcd for C60H79N3O13 triethylamine (0.04 g, 0.40 mmol) in chloroform (15 mL) was
[M]+ 1049.5613, found [M + H]+ 1050.5686, [M + Na]+ stirred for 10 min, then a solution of acetyl chloride (0.03 g,
1072.5504.
0.4 mmol) in chloroform (5 mL) was added to the reaction
1
1u: mp 115–117 °C. H NMR (400 MHz, DMSO-d6, 298 K) δ solution. After 30 min, the reaction was completed, monitored
(ppm) = 6.82–6.71 (m, 10H), 6.02 (s, 1H), 5.92 (s, 1H), by TLC. The solvent was removed in vacuo and the residue was
4.51–4.46 (d, 1H), 3.79 (s, 2H), 3.72–3.66 (m, 37H), 3.40 (t, J = purified by column chromatography on silica gel (CH2Cl2–
4.7 Hz, 2H), 3.31 (water peak), 2.97 (m, 2H), 2.86 (m, 2H), 2.49 CH3OH, v/v = 30 : 1), giving 4 as a white solid (0.298 g, 95.2%).
(solvent peak), 1.36 (s, 9H), 1.21 (s, 12H). 13C NMR (100 MHz, Mp 125–126 °C. H NMR (400 MHz, DMSO-d6, 298 K) δ (ppm)
1
DMSO-d6, 298 K) δ (ppm) = 158.1, 155.5, 150.0, 149.9, 149.6, = 7.70 (s, 1H), 6.82–6.72 (m, 10H), 5.99 (s, 1H), 5.85 (s, 1H),
149.1, 127.8, 127.5, 127.4, 127.2, 113.6, 113.3, 77.2, 55.41, 3.80 (t, J = 6.6 Hz, 2H), 3.68–3.64 (m, 37H), 3.40 (q, J = 6.9 Hz,
55.36, 54.9, 54.8, 30.0, 29.4, 29.3, 29.0, 28.8, 28.2, 28.1, 26.3, 2H), 2.97–2.92 (m, 4H), 1.77 (s, 3H), 1.30–1.13 (m, 12H). 13C
26.2, 22.8. HR-ESI-MS: m/z calcd for
1049.5613, found [M + H]+ 1050.5696, [M + Na]+ 1072.5526. 1u 149.98, 149.94, 149.91, 149.8, 149.3, 149.1, 127.7, 127.6, 127.5,
and 1conf1 are identical in the ESI-MS spectrum. 127.46, 127.40, 127.35, 114.3, 113.6, 113.3, 95.4, 68.0, 55.4,
C
60H79N3O13 [M]+ NMR (100 MHz, DMSO-d6, 298 K) δ (ppm) = 168.8, 158.1,
Pseudo[1]rotaxane 2/2u. The synthesis of 2 and 2u was the 55.34, 55.30, 29.9, 29.1, 28.9, 28.8, 26.4, 26.3, 22.6. HR-ESI-MS:
same as 1conf1 and 1u. Column chromatography (CH2Cl2– m/z calcd for C57H73N3O12 [M]+ 991.5194, found [M + H]+
CH3OH v/v = 140 : 1) gave 2 (4%) and 2u (62%) as white solid.
2: 1H NMR (400 MHz, DMSO-d6, 298 K) δ (ppm) = 6.84–6.76
992.5349, [M + Na]+ 1014.5107.
[1]Rotaxane 5. The capping reaction was performed accord-
(m, 10H), 6.17 (s, 1H), 5.89 (s, 1H), 3.83 (s, 2H), 3.74–3.63 (m, ing to the literature method.17 A solution of 3 (0.2 g,
37H), 3.17 (s, 2H), 2.89 (s, 1H), 2.87 (s, 1H), 1.85 (s, 2H), 1.68 0.21 mmol) and 3,5-di-tert-butylbenzaldehyde (0.05 g,
(m, 2H), 1.39 (s, 9H), 1.22–1.16 (m, 6H), 0.72 (s, 2H), 0.11 (s, 0.23 mmol) in chloroform (20 mL) was stirred for 24 h, then
2H), −0.76 (s, 2H), −2.02 (s, 2H), −2.09 (s, 2H). 13C NMR NaBH4 (0.03 g, 0.8 mmol) and ethanol (5 mL) were added in
(100 MHz, DMSO-d6, 298 K) δ (ppm) = 158.1, 155.5, 149.8, the reaction solution. After another 24 h, the reaction was com-
149.2, 127.5, 127.4, 114.1, 113.2, 77.2, 55.3, 30.1, 29.4, 28.9, pleted, monitored by TLC. The solvent was removed in vacuo
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and the residue was purified by column chromatography on removed by evaporation in vacuo and the product was obtained
silica gel (CH2Cl2–CH3OH, v/v = 10 : 1–6 : 1), giving 5 as a white as a buff powder (0.91 g, 98%). Remark: this compound is
solid (0.065 g, 26.6%). Mp 93–96 °C. 1H NMR (400 MHz, unstable under acidic conditions, thus 9 was utilized without
DMSO-d6, 298 K) δ (ppm) = 7.48 (s, 1H), 7.43 (s, 1H), 7.39 (s, further purification by silica column chromatography, which
1H), 6.83–6.77 (m, 10H), 6.12 (s, 1H), 6.02 (s, 1H), 4.03 (s, 2H), caused a little impurity in the spectrum. Mp 58–62 °C. 1H
3.78–3.63 (m, 39H), 3.40 (m, 2H), 2.99 (m, 2H), 2.83 (m, 2H), NMR (300 MHz, CDCl3, 298 K) δ (ppm) = 8.27 (s, 1H), 8.07 (s,
1.63 (m, 2H), 1.35 (s, 9H), 1.33 (s, 9H), 1.24 (m, 2H), −0.25 (br, 1H), 7.60 (s, 1H), 7.32 (chloroform solvent), 7.01 (s, 1H), 4.90
2H), −1.14 (br, 2H), −1.69 (br, 2H), −2.06 (br, 2H). 13C NMR (s, 1H), 3.37 (q, J = 4.7 Hz, 2H), 3.06 (q, J = 5.1 Hz, 2H), 1.59
(100 MHz, DMSO-d6, 298 K) δ (ppm) = 158.4, 158.3, 158.1, (m, 2H), 1.43 (s, 10H), 1.25 (s, 9H). 13C NMR (100 MHz, CDCl3,
150.6, 150.0, 149.8, 149.7, 149.6, 149.1, 149.0, 127.7, 127.6, 298 K) δ (ppm) = 156.3, 149.2, 136.1, 129.5, 116.5, 79.1, 57.9,
127.4, 127.2, 123.9, 122.0, 114.3, 113.7, 113.3, 112.5, 95.4, 67.9, 40.9, 40.5, 30.0, 29.2, 28.9, 28.4, 26.6, 26.5. HR-ESI-MS: m/z
55.4, 55.3, 55.2, 55.1, 54.7, 52.0, 50.8, 46.8, 34.59, 34.56, 34.44, calcd for C17H30N4O3 [M]+, 338.2318, found [M + H]+ 339.2521,
34.34, 31.23, 31.17, 30.0, 29.1, 29.0, 28.7, 28.5, 26.9, 26.3, 26.0, [M + Na]+ 361.2215.
25.5. HR-ESI-MS m/z: calcd for C70H93N3O11 [M]+ 1151.6810,
N-(tert-Butoxycarbonyl)-1,8-octanediamine (10). Mono-pro-
tection of diamines with the Boc group was performed accord-
found [M + H]+ 1152.6902.
Pseudo[1]rotaxane 6. The synthesis of 6 was similar to that of ing to the literature method.24 A solution of Boc2O (2.42 g,
1
10 (see below). Yield: 45%. Mp 103–105 °C. H NMR (400 MHz, 12 mmol) in CHCl3 (40 mL) was added dropwise over a 2 h
CDCl3, 298 K) δ (ppm) = 7.02–6.80 (m, 10H), 3.95–3.66 (m, 39H), period to the solution of 1,8-diamino octane (3.46 g, 24 mmol)
1.88 (m, 2H), 1.60 (m, 2H), 1.51 (s, 9H), 1.43 (m, 2H), 1.33 (m, and TEA (2.42 g, 24 mmol) in CHCl3 (150 mL) cooled with an
2H), 1.27 (m, 2H), 1.12 (m, 2H), 0.88 (s, 2H), 0.29 (m, 2H), −0.65 ice-bath. The reaction mixture was stirred overnight at room
(s, 2H), −1.92 (s, 2H), −1.96 (s, 2H). 13C NMR (100 MHz, CDCl3, temperature and filtered. The filtrate was concentrated under
298 K) δ (ppm) = 155.6, 154.8, 150.94, 150.90, 150.86, 150.76, vacuum and the resulting oil dissolved in CHCl3 (100 mL) was
150.68, 150.5, 150.3, 150.2, 150.1, 149.8, 128.6, 128.39, 128.35, washed with H2O (6 × 100 mL) until 1,8-diamino octane could
128.24, 128.16, 128.1, 115.2, 114.3, 114.2, 113.9, 113.7, 113.1, not be observed by TLC, the organic layer was dried with anhy-
78.5, 68.7, 68.6, 68.4, 55.89, 55.85, 55.78, 55.72, 55.61, 55.58, drous MgSO4 and concentrated under vacuum to afford pure
55.50, 55.3, 55.2, 40.7, 30.1, 30.0, 29.73, 29.68, 29.5, 29.4, 29.3, mono-Boc-protected diamine 10. Further purification by silica
1
29.1, 28.6, 28.5, 26.1. H NMR (400 MHz, DMSO-d6, 298 K) δ column chromatography (CH2Cl2–CH3OH, v/v = 200 : 1–60 : 1)
(ppm) = 6.79–6.75 (m, 10H), 5.69 (s, 1H), 3.82 (t, J = 6.2 Hz, gave 10 as a white solid (1.30 g, 36.5%). Mp 73–74 °C. 1H NMR
2H), 3.73–3.31 (m, 37H), 2.76 (q, J = 6.3 Hz, 2H), 1.73 (m, 2H), (300 MHz, CDCl3, 298 K) δ (ppm) = 4.56 (s, 1H), 3.08 (q, J = 6.5
1.47 (m, 2H), 1.37 (s, 9H), 1.32 (m, 2H), 1.24 (m, 2H), 1.16–0.97 Hz, 2H), 2.66 (t, J = 7.0 Hz, 2H), 1.65 (s, 2H), 1.42 (s, 12H), 1.28
(m, 10H, overlapped). 13C NMR (100 MHz, DMSO-d6, 298 K) δ (s, 9H). 13C NMR (100 MHz, CDCl3, 298 K) δ (ppm) = 163.5,
(ppm) = 155.4, 149.97, 149.91, 149.87, 149.82, 149.80, 149.2, 156.0, 78.8, 41.7, 41.3, 40.5, 32.2, 30.6, 30.0, 29.2, 29.1, 28.4,
127.49, 127.46, 127.41, 127.36, 114.1, 113.3, 113.2, 95.4, 79.2, 26.7. HR-ESI-MS: m/z calcd for C13H28N2O2 [M]+ 244.2151,
77.2, 67.7, 55.34, 55.27, 55.2, 54.8, 29.2, 28.9, 28.84, 28.75, found [M + H]+ 245.2290, [M + Na]+ 267.2044.
28.69, 28.61, 28.5, 28.22, 28.16, 26.2, 25.4. HR-ESI-MS: m/z
N-(Triphenylmethyl)-N′-(imidazolylcarbonyl)-1,8-octanedi-
calcd for C61H81NO12 [M]+ 1019.5759, found [M
1020.5834.
+
H]+ amine (11). Compound 11 was synthesized in a similar way as
that of 9. Yield: 99%. Mp 93–96 °C. 1H NMR (300 MHz, CDCl3,
Copillar[5]arene 7u. The synthetic procedure of 7u is 298 K) δ (ppm) = 8.17 (s, 1H), 7.46 (d, J = 7.3 Hz, 6H), 7.40 (s,
similar to that of compound 1conf1. Yield: 44.1%. Mp 93–96 °C. 1H), 7.26 (chloroform solvent), 7.25 (t, J = 6.2 Hz, 6H), 7.16 (t,
1H NMR (400 MHz, DMSO-d6, 298 K) δ (ppm) = 7.39 (d, J = 7.6 J = 7.2 Hz, 3H), 7.01 (s, 1H), 3.37 (q, J = 6.4 Hz, 2H), 2.11 (t, J =
Hz, 6H), 7.27 (t, J = 7.4 Hz, 6H), 7.15 (t, J = 7.2 Hz, 3H), 7.0 Hz, 2H), 1.61–1.26 (m, 12H). 13C NMR (100 MHz, CDCl3,
6.82–6.76 (m, 10H), 6.02 (s, 1H), 5.92 (s, 1H), 3.79 (t, 2H), 298 K) δ (ppm) = 149.0, 146.3, 135.8, 130.0, 128.7, 127.8, 126.2,
3.68–3.60 (m, 37H), 3.40 (q, 2H), 2.98 (m, 2H), 1.95 (m, 2H), 116.3, 96.1, 71.0, 64.5, 43.6, 41.1, 30.8, 29.5, 29.2, 27.3, 26.8,
1.43 (s, 2H), 1.33 (s, 2H), 1.19 (s, 8H). 13C NMR (75 MHz, 14.2. HR-ESI-MS m/z: calcd for C32H37N3O [M]+ 479.2937,
DMSO-d6, 298 K) δ (ppm) = 158.0, 150.0, 149.1, 146.3, 128.3, found [M + H]+ 481.2978, [M + Na]+ 503.2784.
127.7, 127.6, 125.9, 113.6, 113.3, 95.4, 70.4, 67.9, 55.4, 43.3,
N-(Triphenylmethyl)-1,8-octanediamine (12). Compound 12
30.0, 29.0, 28.8, 26.9, 26.4. HR-ESI-MS m/z: calcd for was synthesized in a similar way as that of 10, colorless oil,
1
C74H85N3O11 [M]+ 1191.6184, found [M + H]+ 1192.6503, yield: 36.5%. H NMR (300 MHz, CDCl3, 298 K) δ (ppm) = 7.49
[M + Na]+ 1214.6072.
(d, J = 7.4 Hz, 6H), 7.28 (t, J = 7.1 Hz, 6H), 7.18 (t, J = 7.1 Hz,
N-(tert-Butoxycarbonyl)-N′-(imidazolylcarbonyl)-1,8-octane- 3H), 2.68 (t, J = 6.9 Hz, 2H), 2.12 (t, J = 6.9 Hz, 2H), 1.48–1.27
diamine (9). The synthesis of 9 was according to the literature (m, 16H). 13C NMR (100 MHz, CDCl3, 298 K) δ (ppm) = 146.4,
method.13 10 (0.67 g, 2.74 mmol) and 1,1-carbonyldiimidazole 128.7, 127.8, 126.2, 70.9, 43.6, 42.3, 33.9, 30.9, 29.7, 29.5, 27.4,
(CDI) (1.38 g, 8.5 mmol) were suspended in CHCl3 (50 mL) 26.9. HR-ESI-MS m/z: calcd for C27H34N2 [M]+ 386.2722, found
and stirred for 12 h at room temperature. The reaction mixture [M + H]+ 387.2795.
was washed with saturated NaHCO3 solution (40 mL) and
1-(4-Bromo-n-butoxy)-4-methoxybenzene (13). The synthetic
brine (40 mL). After drying with Na2SO4, the organic layer was procedure of 13 is according to the literature,25 yield 85.9%.
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Mp 31–32 °C. 1H NMR (400 MHz, CDCl3, 298 K) δ (ppm) = 6.80 3.66–3.64 (m, 37H), 2.08 (t, J = 5 Hz, 2H), 1.71 (m, 2H), 1.41
(s, 4H), 3.90 (t, J = 4 Hz, 2H), 3.73 (s, 3H), 3.45 (t, J = 5 Hz, 2H), (m, 2H), 1.1 (m, 2H), 1.11–0.82 (m, 10H), 0.68 (s, 4H). 13C
2.04–2.01 (m, 2H), 1.90–1.86 (m, 2H). 13C NMR (100 MHz, NMR (100 MHz, DMSO-d6, 298 K) δ (ppm) = 149.8, 127.4,
CDCl3, 298 K) δ (ppm) = 153.9, 153.1, 115.5, 114.7, 67.5, 55.7, 112.9, 95.5, 67.7, 55.0, 41.2, 32.5, 29.4, 29.3, 29.2, 29.1, 25.8.
33.6, 29.6, 28.1 ppm. LR-ESI-MS m/z: calcd for C11H15BrO2 [M]+ HR-ESI-MS m/z: calcd for C56H73NO10 [M]+ 919.5234, found
258.0255, found [M + H]+ 259.00, [M + K]+ 296.10.
[M + H]+ 920.5329, [M + Na]+ 942.4845.
Copillar[5]arene 14. 14 was synthesized according to a
reported method.26 Paraformaldehyde (1.80 g, 60.0 mmol) was
added to
a solution of 1,4-dimethoxybenzene (2.75 g,
Acknowledgements
20.0 mmol) and 1-(4-bromobutoxy)-4-methoxybenzene (0.32 g,
1.25 mmol) in dry CH2Cl2 (150 mL) under a nitrogen atmos- We gratefully thank the National Basic Research Program of
phere. Anhydrous FeCl3 (0.52 g, 3.2 mmol) was then added to China (2011CB808600) and the National Natural Science Foun-
the solution and the mixture was stirred in an ice bath for dation of China (nos. 20932004, 21072093, 21202083,
2.5 h. The solution was then washed with H2O (150 mL). The 91227106) for financial support.
organic layer was dried with anhydrous Na2SO4, concentrated
under vacuum, and subjected to silica column chromato-
graphy (hexanes–CH2Cl2 v/v = 1 : 3) to give 14 (0.11 g, 10%).
Notes and references
Mp 99–102 °C. 1H NMR (400 MHz, DMSO-d6, 298 K) δ (ppm) =
6.85–6.75 (m, 10H, ArH), 3.86 (t, J = 6.1 Hz, 2H), 3.81–3.61 (m,
37H), 3.50 (t, J = 6.4 Hz, 2H), 1.92 (m, 2H), 1.81 (m, 2H). 13C
NMR (75 MHz, DMSO-d6, 298 K) δ (ppm) = 153.3, 153.0, 151.2,
150.0, 149.2, 129.3, 127.5, 116.4, 114.6, 114.2, 113.2, 111.4,
110.9, 95.4, 67.1, 55.7, 55.4, 34.5, 29.5, 28.9, 27.9. HR-ESI-MS
m/z: calcd for C48H55BrO10 [M]+ 870.2979, found [M + NH4]+
888.3342.
1 (a) D. B. Amabilino and J. F. Stoddart, Chem. Rev., 1995, 95,
2725–2828; (b) F. M. Raymo and J. F. Stoddart, Chem. Rev.,
1999, 99, 1643–1664; (c) X. Ma and H. Tian, Chem. Soc.
Rev., 2010, 39, 70–80; (d) R. S. Forgan, J.-P. Sauvage and
J. F. Stoddart, Chem. Rev., 2011, 111, 5434–5464;
(e) J. Rotzler and M. Mayor, Chem. Soc. Rev., 2013, 42, 44–
62.
Copillar[5]arene 15. The synthetic procedure of 15 is similar
to our previous work,27 the combined yield from 13 to 15 is
calculated to be 20.0%. Mp 113–116 °C. 1H NMR (400 MHz,
DMSO-d6, 298 K) δ (ppm) = 6.79–6.76 (m, 10H), 3.81 (t, 2H, J =
6.3 Hz), 3.65 (m, 37H), 2.57 (t, J = 6.8 Hz, 2H), 1.73 (m, 2H),
1.52 (m, 2H). 13C NMR (100 MHz, DMSO-d6, 298 K) δ (ppm) =
149.9, 127.5, 114.0, 113.3, 95.4, 67.7, 55.4, 28.9, 26.6.
HR-ESI-MS m/z: calcd for C48H57NO10 [M]+ 807.3982, found
[M + H]+ 808.4321, [M + Na]+ 830.3894.
1-(12-Bromododecyl)-4-methoxybenzene (16). The synthetic
procedure of 16 is similar to that of compound 13. Yield:
81.75%. Mp 38–42 °C. 1H NMR (300 MHz, CDCl3, 298 K) δ
(ppm) = 7.26 (solvent peak), 6.83 (s, 4H, ArH), 3.90 (t, J = 5.0
Hz, 2H), 3.76 (s, 3H), 3.40 (t, J = 5.2 Hz, 2H), 1.85 (m, 2H), 1.75
(m, 2H), 1.43–1.26 (m, 16H). 13C NMR (75 MHz, CDCl3, 298 K)
δ (ppm) = 153.7, 153.3, 115.4, 114.6, 55.7, 34.0, 32.9, 29.6,
29.5, 29.4, 28.8, 28.2, 26.1. HR-ESI-MS: m/z calcd for
C19H31BrO2 [M]+, 370.1507, found [M + H]+ 371.1581.
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Copillar[5]arene 17. The synthetic procedure of 17 is similar
1
to that of compound 14. Mp 178–180 °C. H NMR (400 MHz,
DMSO-d6, 298 K) δ (ppm) = 6.85–6.75 (m, 10H, ArH), 3.84 (t, J =
6.1 Hz, 2H), 3.77–3.63 (m, 37H), 3.50 (t, J = 6.4 Hz, 2H), 1.92
(m, 2H), 1.81 (m, 2H). 13C NMR (100 MHz, CDCl3, 298 K) δ
(ppm) = 150.5, 150.4, 150.3, 150.2, 149.8, 128.0, 113.7, 113.3,
113.2, 113.0, 68.5, 55.6, 55.4, 55.3, 33.7, 31.6, 30.0, 29.3, 29.2,
28.2, 27.7, 25.6. HR-ESI-MS m/z: calcd for C56H71BrO10 [M]+
982.4231, found [M + NH4]+ 1000.4586.
Copillar[5]arene 18. The synthetic procedure of 18 is similar
to that of compound 15, the combined yield from 16 to 18 is
calculated to be 24.6%. Mp 112–114 °C. 1H NMR (400 MHz,
DMSO-d6, 298 K) δ (ppm) = 6.79–6.75 (m, 10H), 3.80 (m, 2H),
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