Branched [n]rotaxanes (n = 2-4) from multiple dibenzo-24-crown-8 ether wheels and 1,2-bis(4,4′-dipyridinium)ethane axles

Article abstract of DOI:10.1039/b418772e

To investigate the possibility of incorporating the 1,2-bis(pyridinium) ethane24?8 [2]pseudorotaxane motif into dendrimer like macromolecules, a series of branched [n]rotaxanes were prepared employing multiple dibenzo-24-membered crown ether wheels with v

Full text of DOI:10.1039/b418772e

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A R T I C L E
Branched [n]rotaxanes (n = 2–4) from multiple dibenzo-24-crown-8
ether wheels and 1,2-bis(4,4ꢀ-dipyridinium)ethane axles
Stephen J. Loeb* and David A. Tramontozzi
Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, Canada
N9B 3P4. E-mail: loeb@uwindsor.ca; Fax: 1-519-973-7098; Tel: 1-519-253-3000
Received 15th December 2004, Accepted 16th February 2005
First published as an Advance Article on the web 7th March 2005
To investigate the possibility of incorporating the 1,2-bis(pyridinium)ethane⊂24C8 [2]pseudorotaxane motif into
dendrimer like macromolecules, a series of branched [n]rotaxanes were prepared employing multiple
dibenzo-24-membered crown ether wheels with various aromatic core structures and the 1,2-bis(4,4ꢀ-
dipyridinium)ethane axle. Yields of branched [2]-, [3]- and [4]rotaxanes were dependent on the size of the core and the
relative proximity of the crown ethers arranged around the core unit.
of this motif to the construction of larger branched [n]rotaxanes
built around new multiple site dibenzo[24]crown ethers; Fig. 2.
Introduction
Polyrotaxanes1 and polycatenanes2 are supramolecular poly-
mers which contain macromolecular architectures built, in some
fashion, around mechanical linkages. The interest in these chem-
ical systems can be attributed in part to their aesthetic structures
but also to the fundamental role that interlocked components
might play in entanglements, rheology, elasticity and mechanical
properties of polymers.1–3 In particular, dendrimers and hyper-
branched macromolecules based on interlocked components
have attracted recent attention as both models for supramolecu-
lar polymers and interesting macromolecules in their own right.4
A number of templating motifs and synthetic strategies have
been studied but the efficient incorporation of multiple mechan-
ically linked subunits into a single macromolecule remains a
challenge for the synthetic chemist.4a–d,5
A single generation dendrimer (G1) contains three distinct
components, the core, the terminal groups and the branches
that connect the two. Further generations can be prepared
if the terminal groups of the G1 molecule can be further
branched and terminated to give G2 and this process repeated
to give G3, G4, etc.6 There are therefore, a variety of ways that
mechanical linkages can be introduced into dendrimers. These
have been termed Types I, II and III by Lee and Kim, where the
interlocked component occupies the core, the terminal group
or the branches respectively.7 We are particularly interested
in Type III dendrimers in which all the branching points
of the macromolecule are mechanical linkages. These can be
constructed by either (A) threading multiple ring components
on to branches attached to a single core or (B) threading multiple
axles on to rings appended to a central core.7
The [2]pseudorotaxane motif which combines 1,2-
bis(pyridinium)ethane axles and 24C8 wheels (Fig. 1) has
previously been used to construct various [2]- and [3]rotaxanes,
[3]catenanes and molecular shuttles.8 Using metal-based linking
nodes this motif has also been incorporated into 1D, 2D
and 3D-polyrotaxanes.9 As a possible route to Type III-B
dendrimeric polyrotaxanes, we describe herein, the application
Fig. 2 A cartoon depiction of the pathway to a Type III-B dendritic
polyrotaxane incorporating ring components at the branching points
(axle = blue, wheel = red, core unit = yellow, stoppers = green).
Results and discussion
Our approach was to take various polyphenolic cores and
attach DB24C8 appendages. The resulting multi-site crown
ethers would then allow us to study the effects of the various
geometries and spatial arrangements around the core upon
threading the 1,2-bis(4,4ꢀ-dipyridinium)ethane dicationic axle,
12+. We naturally anticipated that spacing the crown ethers
away from each other would lead to a higher proportion of
the fully occupied core thereby introducing fewer defects into
this divergent synthesis.
The simple phenyl ether 5 was prepared as a model for
the multi-site DB24C8 derivatives used in this study; having
a single macrocycle appended to the core benzene unit. As
outlined in Scheme 1, the known aldehyde 210 was reduced to
the alcohol 3 and chlorinated to yield 4 which upon reaction
with phenol under typical Williamson ether synthesis conditions
gave 5 in near quantitative yield; 98%. The 1H NMR spectrum
of 5 showed a characteristic resonance at 4.65 ppm for the
Fig. 1 A [2]pseudorotaxane is easily formed between the dicationic
“axle” 1,2-bis(4,4ꢀ-dipyridinium)ethane, 12+ (blue) and the macrocyclic
“wheel” DB24C8 (red).
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1
1 3 9 3
©

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Scheme 1 Reagents and conditions: i, NaBH4, EtOH–CH2Cl2 (1 : 1); ii, SOCl2, CH2Cl2; iii, C6H5OH, K2CO3, CH3CN; iv, 2 eq. 1.2OTf, 4 eq.
t-Bu(C6H4)CH2Br, MeNO2–NaOTf(aq).
and the electron poor pyridinium rings. This is consistent with
[2]pseudorotaxane formation. This solution was then stirred
at room temperature overnight and 4 equivalents of 4-tert-
butylbenzyl bromide added along with a layer of saturated
aqueous sodium triflate. This two-phase reaction mixture was
stirred for three days during which time the solution turned
orange, indicative of a change in the charge transfer band due to
conversion of the axle from a dipyridinium to a tetrapyridinium
cation, and thus [2]rotaxane formation. The [2]rotaxane 6.4OTf
was isolated by silica column chromatography using a 6 : 1 : 3
ratio of methanol–nitromethane–2 M NH4Cl(aq) as eluent.
The isolated material was then anion exchanged with NaOTf
to regenerate the salt 6.4OTf, as an orange–red solid in 40%
overall yield. HR-ESI-MS verified the production of 6.4OTf
as peaks corresponding to the loss of one, two, three and four
triflate anions from the molecular ion were detected at 1635.5120
[6.3OTf]+, 743.2850 [6.2OTf]2+, 445.8500 [6.OTf]3+ and 297.1564
[6]4+, respectively. The interlocked nature of 64+ was confirmed
Fig. 3 A ball-and-stick representation of the X-ray crystal structure of
5.
new benzyloxy methylene group as well as the expected peaks
for methylene and aromatic protons from the DB24C8 and
phenolic groups. A high-resolution electrospray ionisation mass
spectrum (HR-ESI-MS) showed one significant, singly charged
peak (577.2414) with a mass 23 m/z units higher than expected
for 5 which was identified as [M + Na]+.
1
by H NMR spectroscopy. Hydrogen bonding between the a-
pyridinium and ethylene protons of the axle and the polyether
oxygens of the macrocycle was apparent from the downfield shift
of these signals (Dd = 0.31–0.34 ppm). In addition, p-stacking
interactions were evident from the upfield shifts of the aromatic
protons (Dd = 0.14–0.52 ppm). Finally, a diagnostic chemical
shift change occurs for the benzylic protons of the crown; 5
shows a singlet at 4.96 ppm but in the [2]rotaxane 6.4OTf this
signal shifts upfield to 4.55 ppm (Dd = 0.41 ppm). As there is
a clear difference between free and complexed crown for this
signal and since it occurs in a relatively uncluttered part of the
spectrum, this shift can be used to calculate (vide infra) the
amount of each species in a mixture of [n]rotaxanes.
X-Ray quality crystals of 5 were grown by vapour diffusion of
hexanes into a saturated chloroform solution of the compound.
The solid-state structure11 (Fig. 3) is interesting for two reasons;
(i) it shows that the conformation of the DB24C8 macrocycle is
essentially the same as that found for the parent DB24C8 and (ii)
it demonstrates that the appended aromatic ring is rotated away
from the opening of the crown cavity. Both these observations
indicate that each individual macrocycle of the new multi-site
crown ethers should be available for threading axle 12+ and
formation of a [2]pseudorotaxane.
The crown ether 5 was used to prepare the corresponding
[2]rotaxane 6.4OTf. This compound contains all the major
subunits of the target branched [n]rotaxanes and was used as
a guide for characterisation of these more complex macro-
molecules. The preparative conditions used were similar to those
employed for other [2]rotaxanes prepared using this motif.8
Initially, 5 and 1.2OTf were dissolved in nitromethane to give
a yellow solution indicative of p–p interactions and charge
transfer between the electron rich rings of the crown ether
The first step towards preparing analogous branched
[n]rotaxanes was to prepare the multi-site derivatives of DB24C8
shown in Fig. 4. As described for 5, a Williamson ether
synthesis from the chloromethyl derivative 4 was used to append
DB24C8 units to a central benzene core through –OCH2– link-
ages. 1,2-, 1,3- and 1,4-core substituted bis(crowns) 7–9 were pre-
pared from catechol, resorcinol and hydroquinone, respectively.
1
The H NMR spectra of 7–9 exhibited OCH2 (3.8–4.2 ppm)
Fig. 4 Three bis(crown) ethers based on a single benzene core.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1
1 3 9 4

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Fig. 5 The [2]rotaxanes 104+, 124+and 144+ and [3]rotaxanes 118+, 138+ and 158+ formed from the bis(crown) ethers 7,8 and 9 respectively.
Table 1 Mass spectrometry dataa for branched [n]rotaxanes 10–15
and aromatic resonances (6.8–7.0 ppm) attributable to an
unsymmetrical DB24C8 along with a single benzylic resonance
at ∼5.0 ppm. Further aromatic resonances were consistent with
the substitution patterns expected for the different cores. New
crown ethers 7–9 were also identified by HR-ESI-MS as the
[M + Na]+ and [M + 2Na]2+ ions (see Experimental section).
To investigate the ability of these crowns to form branched
[2]- and [3]rotaxanes, 7–9 were combined with two equivalents
of 1,2-bis(4,4ꢀ-bipyridinium)ethane triflate, 1.2OTf, per crown
ether moiety and an excess of 4-tert-butylbenzyl bromide
added to effect stoppering. All six of the rotaxanes 10.4OTf–
15.8OTf (Fig. 5) were isolated by column chromatography and
[n]Rotaxane
10.4OTf
Complex ion
Observed mass (m/z)
[10.3OTf]+
[10.2OTf]2+
[10.OTf]3+
[10]4+
2111.7068
981.3887
604.6057
416.2236
11.8OTf
[11.6OTf]2+
[11.5OTf]3+
[11.4OTf]4+
[11.3OTf]5+
[11.2OTf]6+
1596.4931
1014.6910
723.7757
549.2340
432.8669
1
successfully characterized by H NMR spectroscopy and HR-
1
ESI-MS. The [3]rotaxanes exhibited simpler H NMR spectra
12.4OTf
13.8OTf
[12.3OTf]+
[12.2OTf]2+
[12.OTf]3+
[12]4+
2111.7097
981.3876
604.6085
416.2225
due to the inherent symmetry of having both crown ether
sites involved in rotaxane formation. Characteristic shifts were
similar to those observed for the model [2]rotaxane 6.4OTf and
this verified their interlocked nature. The [2]rotaxane 1H NMR
spectra were much more complicated as both complexed and
uncomplexed crown peaks were present along with those from
the complexed pyridinium axles. HR-ESI-MS showed ions due
to the loss of 1–4 triflate anions and are summarized in Table 1.
Table 2 summarizes the yields for these reactions. Although
the total isolated yield of [n]rotaxanes was variable, due to
variations in work-up, there was a clear trend in the ratio of
[2]rotaxane to [3]rotaxane produced. When the two crown ether
rings were positioned adjacent to each other in the 1- and 2-
positions of the central benzene core, the [2]rotaxane was heavily
favoured. However, as the two macrocycles were positioned
farther apart at the 1,3- and 1,4 positions, the yield of [3]rotaxane
increased relative to the [2]rotaxane. Statistically, the [2]rotaxane
should be favoured as it must form first but the trend indicates
that the proximity of a neighbouring site inhibits the threading
of a second axle through the second crown ether. This inhibition
is more pronounced when the sites are closer together and this
is mirrored in the relative yields of [2]rotaxane vs. [3]rotaxane.
Since it appeared that utilising a single aromatic ring as the
central core might be sterically limiting, we also chose to look
at two cores with multiple aromatic rings derived from 4,4ꢀ-
biphenol and 1,3,5-tris(4-hydroxyphenyl)benzene. Crown ether
16 was prepared from 4,4ꢀ-biphenol and two equivalents of 4
in a fashion similar to that used to make 7–9. Reaction of 16
with four equivalents of 1.2OTf and excess 4-tert-butylbenzyl
bromide gave the [2]rotaxane 17.4OTf and the [3]rotaxane
18.8OTf; see Fig. 6. Both the [2]rotaxane 17.4OTf and the
[3]rotaxane 18.8OTf were isolated by column chromatography
[13.6OTf]2+
[13.5OTf]3+
[13.4OTf]4+
[13.3OTf]5+
[13.2OTf]6+
1596.4929
1014.6904
723.7753
549.2345
432.8674
14.4OTf
15.8OTf
[14.3OTf]+
[14.2OTf]2+
[14.OTf]3+
[14]4+
2111.7312
981.3898
604.6115
416.2171
[15.6OTf]2+
[15.5OTf]3+
[15.4OTf]4+
[15.3OTf]5+
[15.2OTf]6+
1596.4932
1014.7112
723.7756
549.2338
432.8712
a Data were recorded on a Micromass LCT electrospray ionisation mass
spectrometer using MeCN–H2O mixtures. HR spectra were recorded in
lockmass mode.
ESI-MS. As observed for 10.4OTf–15.8OTf, the [3]rotaxane,
18.8OTf, exhibited a less complicated 1H NMR spectrum
due to symmetry with characteristic shifts similar to those
observed for the model [2]rotaxane 6.4OTf thus verifying the
1
interlocked structure. The H NMR spectrum of [2]rotaxane
17.4OTf exhibited resonances attributable to both complexed
and uncomplexed crown in a 1 : 1 ratio as well as those from
the pyridinium axle. HR-ESI-MS showed ions due to the loss of
1–4 triflate anions and are summarized in Table 3.
Crown ether 19 was prepared from 1,3,5-tris(4-hydroxy-
phenyl)benzene and three equivalents of 4. Reaction of 19 with
1
and successfully characterized by H NMR spectroscopy and
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1
1 3 9 5

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Table 2 Yields of branched [n]rotaxanes for crown ethers 7–9
Crown ether
Chemical yield of [n]rotaxanesa (%)
[2]Rotaxaneb (%)
[3]Rotaxanec (%)
7
8
9
92
83
68
82
70
62
18
30
38
a Total chemical yield of all [n]rotaxanes. b The percentage of the total [n]rotaxane material that is [2]rotaxane. c The percentage of the total [n]rotaxane
material that is [3]rotaxane.
Fig. 6 The bis(crown) ether 16 with a biphenyl spacer allows formation of the [2]rotaxane 174+ and the [3]rotaxane 188+ which is shown above.
Table 3 Mass spectrometry dataa for [n]rotaxanes 17, 18 and 20–22
Table 4 Yields of branched [n]rotaxanes for crown ethers 16 and 19
[n]Rotaxane
17.4OTf
Complex ion
Observed mass (m/z)
Crown ether [2]Rotaxanea (%) [3]Rotaxaneb (%) [4]Rotaxanec (%)
[17.3OTf]+
[17.2OTf]2+
2187.7471
1019.3996
16
19
69
32
31
33
—
35
a The percentage of the total isolated [n]rotaxane material that is
18.8OTf
[18.6OTf]2+
[18.5OTf]3+
[18.4OTf]4+
[18.3OTf]5+
[18.2OTf]6+
1634.5197
1040.0862
742.7834
564.4354
445.5335
[2]rotaxane. b [3]Rotaxane. c [4]Rotaxane.
three pyridinium axles. The HR-ESI-MS results for compound
22.12OTf allowed unambiguous determination of exact mass
for the ion [22.5OTf]7+. Other ions observed at lower resolution
limit were still sufficient to provide further evidence in terms
of position and profile for the existence of the [4]rotaxane; see
Table 3.
The product distribution of [n]rotaxanes for these multi-crown
ethers with larger cores is interesting (Table 4). It appears that
on going from a single benzene unit with a 1,4-positioning, 9,
to a biphenyl unit with the same positioning, 16, there is no
increase in the yield of the fully complexed [3]rotaxane; 38 vs.
31%, respectively. Presumably the negative factors preventing the
threading of the second ring are already reduced to a minimum
with the hydroquinone unit and that further separation with
a biphenol group has no effect. For the tris-crown ether, 19,
the yields of [2]rotaxane, [3]rotaxane and [4]rotaxane are 32, 33
and 35%, reflecting a uniform decrease in the efficiency of each
subsequent threading.
20.4OTf
21.8OTf
[20.2OTf]2+
[20.OTf]3+
[20]4+
1333.5374
839.3750
592.2961
[21.6OTf]2+
[21.5OTf]3+
[21.4OTf]4+
[21.3OTf]5+
[21.2OTf]6+
1948.6509
1249.4468
899.8655
690.0938
550.2519
22.12OTf
[22.5OTf]7+
[22.4OTf]8+
626.1077
529.2
a Data were recorded on a Micromass LCT electrospray ionisation mass
spectrometer using MeCN–H2O mixtures. HR spectra were recorded in
lockmass mode.
six equivalents of 1.2OTf and excess 4-tert-butylbenzylbromide
gave the [2]rotaxane 20.4OTf, the [3]rotaxane 21.8OTf and the
branched [4]rotaxane 22.12OTf; see Fig. 7. In order to elute
the highly charged [4]rotaxane, 22.12OTf, a more polar solvent
system (2 M NH4Cl(aq)–DMF (1 : 1)) was applied after the
elution of 20.4OTf and 21.8OTf. Like fractions (as determined
by TLC), were combined and anion exchanged with NaOTf to
regenerate the salt 22.12OTf as a glassy dark orange–red solid.
Summary and conclusions
The first generations of Type III-B dendrimeric polyrotaxanes
can be prepared using the pseudorotaxane motif which combines
1,2-bis(pyridinium)ethane axles and 24C8 wheels. Multi-crown
ethers are easily prepared from commercially available phenolic
cores and the chloromethyl derivative of DB24C8. The product
distribution of branched [n]rotaxanes observed gives a crude
measure of the efficiency of the threading process required to
produce the fully saturated polyrotaxanes (i.e. all the crowns
converted to rotaxanes). The size of the core can be a single
benzene ring but this is only practical for the formation of two
branches as the two crowns need to be positioned away from each
other in the 1,4-orientation to minimize inhibitory interactions.
1
The H NMR spectrum of the [2]rotaxane 20.4OTf exhibited
resonances attributable to both complexed and uncomplexed
crown in a 1 : 2 ratio while for the [3]rotaxane 21.8OTf this ratio
was 2 : 1 as two of the three crown units are involved in rotaxane
formation. Although the branched [4]rotaxane, 22.12OTf is the
largest molecule prepared in this study the 1H NMR spectrum
was again less complicated due to symmetry with characteristic
shifts for complexed crown only along with resonances for the
1 3 9 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1

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Fig. 7 The tris(crown) ether 19 allows the synthesis of the [2]rotaxane 204+, the [3]rotaxane 218+ and the [4]rotaxane 2212+ which is shown above.
Attaching phenolic units to a central benzene ring allowed
the formation of a larger [4]rotaxane with three branches. The
efficiency of the threading steps decreased sequentially but was
sufficient to allow a moderate yield of the [4]rotaxane under the
limited conditions of this study.
The decrease in efficiency of the threading process upon
addition of each new rotaxane can be attributed to three factors;
(1) steric interactions between an already complexed crown ether
site (pseudorotaxane or rotaxane) and the new incoming thread,
(2) electrostatic repulsions between an existing rotaxane thread
and the new incoming thread and (3) partial occupation of the
unoccupied crown ether recognition elements by a neighboring
rotaxane unit.
experiments were performed on a Bru¨ker Avance 500 instrument
using the deuterated solvent as the lock and the residual solvent
or TMS as the internal reference. Conventional 2-D NMR
experiments (1H–1H COSY and NOESY) were used to assign
all peaks. High-resolution mass spectrometry experiments were
performed on a Micromass LCT electrospray time of flight
(TOF) mass spectrometer in lockmass mode. Solutions of 50–
100 ng lL−1 were prepared in MeCN–H2O (1 : 1) (unless
otherwise indicated) and injected for analysis at a rate of
5 lL min−1 using a syringe pump. The diagram for the X-ray
crystal structure was generated with the program DIAMOND.11
Preparation of crown ether, 3
We are currently focused on optimising the yield of the fully
occupied [n]rotaxanes while developing a strategy to further
functionalise the peripheral stoppering units to allow for the
addition of the new branches and the next generation of
dendrimer.
To a solution of 2 (2.55 g, 5.35 mmol) in ethanol (50 mL) and
methylene chloride (50 mL) cooled to 0 ◦C was slowly added
sodium borohydride (0.607 g, 16.0 mmol) and the resulting
solution allowed to come to room temperature and then stir
overnight. The reaction mixture was acidified with 1 M HCl (3 ×
30 mL) and then extracted with methylene chloride (100 mL).
The organic layer was washed with 1 M NaHCO3 (3 × 50 mL),
water (2 × 50 mL), dried over anhydrous MgSO4 and evaporated
Experimental
Ammonium chloride, tert-butylbenzyl bromide, sodium boro-
hydride, pyridine, thionyl chloride, potassium carbonate, 4,4ꢀ-
biphenol, catechol, hydroquinone, phenol, resorcinol, sodium
triflate and 1,3,5-tris(4-hydroxyphenyl)benzene were purchased
from Aldrich and used as received. Deuterated solvents were
obtained from Cambridge Isotope Laboratories and used as
received. Solvents were dried using an Innovative Technolo-
gies Solvent Purification System. Thin Layer Chromatography
(TLC) was performed using Merck Silica gel 60 F254 plates and
viewed under UV light. Column chromatography was performed
using Silicycle Ultra Pure Silica Gel (230–400 mesh). 1H NMR
1
to yield the desired off-white solid 3. Yield 2.48 g (97%). H
NMR (500 MHz, CDCl3): d 6.82–6.91 (m, 7H), 4.13–4.17 (m,
8H), 3◦.89–3.91 (m, 8H) 3.81–3.83 (m, 8H), 4.58 (s, 2H). Mp
95–96 C. HR-ESI-MS: m/z [3 + Na]+: calc.: 501.2101, found:
501.2100.
Preparation of crown ether, 4
To a solution of pyridine (5.29 g, 66.9 mmol) and thionyl
chloride (7.54 g, 63.4 mmol) in methylene chloride (40 mL) was
added a solution of 3 (6.54 g, 13.7 mmol) in methylene chloride
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1
1 3 9 7

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(10 mL) and the solution stirred at room temperature for 1 h.
Chloroform (50 mL) was added and the reaction mixture poured
over cold water (100 mL). The aqueous layer was extracted with
methylene chloride (2 × 50 mL) and the combined organic layers
washed with water (2 × 50 mL), 1 M NaHCO3 (2 × 50 mL),
a saturated sodium chloride solution (50 mL), dried (MgSO4)
and concentrated (5 mL). Hexanes were added to precipitate
the desired white solid product, 4. Yield 6.51 g (96%). 1H NMR
(500 MHz, CDCl3): d 6.80–6.90 (m, 7H), 4.14–4.17 (m, 8H).
3.90–3.92 (m, 8H), 3.81–3.82 (m, 8H), 4.52 (s, 2H). Mp 90–
Preparation of bis(crown ether), 8
To a solution of resorcinol (0.053 g, 0.48 mmol) and 4 (0.527 g,
1.06 mmol) in acetone (80 mL) was added potassium carbonate
(0.957 g, 6.92 mmol). The mixture was refluxed for 7 days,
cooled and then filtered. After the solvent was removed, the
residue was dissolved in chloroform (50 mL), washed with water
(2 × 50 mL) and dried with anhydrous MgSO4. The solvent
was evaporated to give a yellow residue which was dissolved
in chloroform (3 mL). Hexanes were added to precipitate the
desired white solid, 8. Yield 0.138 g (28%). 1H NMR (500 MHz,
CDCl3): d 7.14 (t, 1H, 3J = 7.6 Hz), 6.83–6.93 (m, 14H), 6.54–
6.58 (m, 3H), 4.90 (s, 4H), 4.12–4.15 (m, 16H), 3.88–3.90 (m,
16H), 3.80 (s, 16H). Mp 110–111 ◦C. HR-ESI-MS: m/z [8 +
Na]+: calc.: 1053.4460, found: 1053.4467. [8 + 2Na]2+: calc.:
538.2179, found: 538.2207.
◦
91 C. HR-ESI-MS: m/z [4 + Na]+: calc.: 519.1762, found:
519.1750.
Preparation of crown ether, 5
To a solution of 4 (0.630 g, 1.27 mmol) and phenol (0.087 g,
0.92 mmol) in acetonitrile (30 mL) was added potassium
carbonate (0.662 g, 4.79 mmol) and the mixture stirred under
reflux for 5 days. The solvent was evaporated and the residue
partitioned between chloroform and water. The organic layer
was washed with water (2 × 50 mL), dried with anhydrous
MgSO4 and concentrated to give the desired off-white solid,
5. Yield 2.48 g (97%). X-Ray quality crystals were grown by the
slow diffusion of hexanes into a saturated chloroform solution
Preparation of bis(crown ether), 9
To a solution of hydroquinone (0.033 g, 0.299 mmol) and 4
(0.366 g, 0.736 mmol) in acetone (80 mL) was added potassium
carbonate (0.641 g, 4.64 mmol) and the mixture refluxed for
7 days. The reaction contents were filtered and the filtrate
evaporated. The residue was dissolved in chloroform (50 mL),
washed with water (2 × 50 mL), dried with anhydrous MgSO4
and evaporated to yield a yellow residue. After dissolution in
chloroform (3 mL), hexanes were added to precipitate the desired
white solid, 9. Yield 0.113 g (37%). 1H NMR (500 MHz, CDCl3):
d 6.84–6.94 (m, 18H), 4.90 (s, 4H), 4.14–4.16 (m, 16H), 3.89–
3.91 (m, 16H), 3.82 (s, 16H). Mp 125–126 ◦C. HR-ESI-MS: m/z
[9 + Na]+: calc.: 1053.4460, found: 1053.4459.
1
of 5. H NMR (500 MHz, CDCl3): d 7.26–7.27 (m, 2H) 6.93–
6.96 (m, 5H), 6.84–6.88 (m, 5H), 4.96 (s, 2H), 4.14–4.17 (m, 8H),
3.90–3.92 (m, 8H), 3.82 (s, 8H). Mp 105–106 ◦C. HR-ESI-MS:
m/z [5 + Na]+: calc.: 577.2414, found: 577.2427.
Preparation of [2]rotaxane, 6.4OTf
Crown ether 5 (0.110 g, 0.198 mmol) and 1.2OTf (0.050 g,
0.097 mmol) were dissolved in nitromethane (20 mL) and stirred
overnight. 4-tert-Butylbenzyl bromide (0.133 g, 0.586 mmol) and
3 mL of saturated NaOTf(aq) were added and the two-phase
reaction stirred for 4 days. The organic layer was separated, dried
over anhydrous MgSO4 and evaporated to dryness. The orange
residue was taken up in acetonitrile (1 mL) and filtered. The
solvent was removed from the filtrate and the residue subjected
to column chromatography [SiO2: methanol–nitromethane–2 M
NH4Cl(aq) (6 : 1 : 3)], (Rf = 0.47). Like fractions were combined,
the solvent removed and anion exchanged with NaOTf(aq) to
yield the product as an orange–red solid. Yield 0.0713 g (41%).
1H NMR (500 MHz, CD3CN): d 9.33 (d, 4H, 3J = 6.7), 8.92 (d,
4H, 3J = 6.7 Hz), 8.24 (d, 4H, 3J = 6.7 Hz), 8.17 (d, 4H, 3J =
6.7 Hz), 7.54 (d, 4H, 3J = 8.3 Hz), 7.40 (d, 4H, 3J = 8.3 Hz), 7.36
Preparation of [2]rotaxane, 10.4OTf and [3]rotaxane, 11.8OTf
Crown ether 7 (0.0153 g, 0.0148 mmol) and 1.2OTf (0.0152 g,
0.0296 mmol) were dissolved in nitromethane (20 mL)
and stirred overnight. 4-tert-Butylbenzyl bromide (0.0229 g,
0.101 mmol) and 3 mL of a saturated NaOTf(aq) were added
and the two-phase reaction stirred for 7 days. The organic layer
was separated, dried with anhydrous MgSO4 and evaporated
to dryness. The orange residue was taken up in MeCN (1 mL)
and filtered. The solvent was removed from the filtrate and the
residue subjected to column chromatography [SiO2: methanol–
nitromethane–2 M NH4Cl(aq) (6 : 1 : 3)]. Like fractions
were combined, the solvent removed and anion exchanged
with NaOTf(aq) to yield the products as orange–red solids.
Overall chemical yield 92%. 10.4OTf: 0.0252 g (82% of total
3
3
3
(dd, 2H, J = 8.2 Hz, J = 7.5 Hz), 7.02 (t, 1H, J = 7.3 Hz),
6.93 (d, 2H, 3J = 8.2), 6.79 (d, 1H, 4J = 1.7 Hz), 6.66–6.64 (m,
3H), 6.50 (dd, 1H, 4J = 1.5 Hz, 3J = 8.2 Hz), 6.40–6.42 (m, 2H)
5.72 (s, 4H), 5.61 (s, 4H◦), 4.57 (s, 2H), 4.00–4.08 (m, 24H), 1.32
(s, 18H). Mp 130–131 C. HR-ESI-MS: m/z [6.3OTf]+: calc.:
1635.5112, found: 1635.5120. [6.2OTf]2+: calc.: 743.2796, found:
743.2850. [6.OTf]3+: calc.: 445.8691, found: 445.8500. [6]4+: calc.:
297.1638, found: 297.1564.
1
material) (Rf = 0.63). H NMR (500 MHz, CD3CN): d 9.27
3
3
(d, 4H, J = 6.6 Hz), 8.90 (d, 4H, J = 6.5 Hz), 8.00 (d, 4H,
3J = 6.5 Hz), 8.15 (d, 4H, J = 6.6 Hz), 7.51 (d, 4H, J =
3
3
3
8.4 Hz), 7.40 (d, 4H, J = 8.4 Hz), 7.17–7.19 (m, 1H), 7.03–
7.09 (m, 4H), 6.80–6.98 (m, 8H), 6.53–6.59 (m, 3H), 6.39 (d,
8H, 3J = 8.2 Hz), 6.33–6.35 (m, 1H), 5.75–5.77 (m, 4H), 5.52–
5.54 (m, 4H), 4.86 (s, 2H), ◦4.57 (s, 2H), 3.46–4.22 (m, 48H),
1.32 (s, 18H). Mp 127–128 C. HR-ESI-MS: m/z [10.3OTf]+:
calc.: 2111.7158, found: 2111.7068. [10.2OTf]2+: calc.: 981.3819,
found: 981.3887. [10.OTf]3+: calc.: 604.6039, found: 604.6057.
[10]4+: calc.: 416.2149, found: 416.2236. 11.8OTf: 0.0109 g (18%
Preparation of bis(crown ether), 7
To a solution of catechol (0.0402 g, 0.365 mmol) and 4 (0.446 g,
0.897 mmol) in acetone (80 mL) was added potassium carbonate
(0.879 g, 6.36 mmol). The mixture was refluxed for 7 days, cooled
and then filtered. The filtrate was evaporated to dryness and
the residue dissolved in chloroform (50 mL). The solution was
washed with water (2 × 50 mL), dried with anhydrous MgSO4
and evaporated to yield a yellow residue which was dissolved in
chloroform (3 mL) and hexanes added to precipitate the desired
white solid 7. Yield 0.085 g (23%). 1H NMR (500 MHz, CDCl3):
d 6.81–6.97 (m, 18H), 4.07–4.15 (m, 16H), 3.85–3.91 (m, 16H),
3.80–3.82 (m, 16H), 5.03 (s, 4H). Mp 121–122 ◦C. HR-ESI-MS:
m/z [7 + Na]+: calc.: 1053.4460, found: 1053.4467. [7 + 2Na]2+:
calc.: 538.2179, found: 538.2084.
1
of total material) (Rf = 0.54). H NMR (500 MHz, CD3CN):
3
3
d 9.29 (d, 8H, J = 6.8 Hz), 8.94 (d, 8H, J = 6.8 Hz), 8.23
(d, 8H, 3J = 6.8 Hz), 8.15 (d, 8H, 3J = 6.8 Hz), 7.52 (d,
3
3
8H, J = 8.4 Hz), 7.42 (d, 8H, J = 8.4 Hz), 6.99–7.02 (m,
4
4H), 6.78 (d, 2H J = 1.5 Hz), 6.61–6.66 (m, 4H), 6.54 (d,
3
4
3
2H, J = 8.2 Hz), 6.44 (dd, 2H, J = 1.5, J = 8.2 Hz), 6.37–
6.40 (m, 4H), 5.73 (s, 8H), 5.56 (s, 8H), 4.61 (s, 4H), 3.95–4.04
(m, 48H), 1.29 (s, 36H). Mp 175–176 ◦C. HR-ESI-MS: m/z
[11.6OTf]2+: calc.: 1596.4877, found: 1596.4901. [11.5OTf]3+:
calc.: 1014.6745, found: 1014.6815. [11.4OTf]4+: calc.: 723.7679,
found: 723.7728. [11.3OTf]5+: calc.: 549.2239, found: 549.2340.
[11.2OTf]6+: calc.: 432.8612, found: 432.8621.
1 3 9 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1

View Article Online
Preparation of [2]rotaxane, 12.4OTf and [3]rotaxane, 13.8OTf
[15.5OTf]3+: calc.: 1014.6745, found: 1014.7112. [15.4OTf]4+:
calc.: 723.7679, found: 723.7756. [15.3OTf]5+: calc.: 549.2239,
found: 549.2338. [15.2OTf]6+: calc.: 432.8612, found: 432.8712.
Crown ether 8 (0.0148 g, 0.0144 mmol) and 1.2OTf (0.0185 g,
0.0359 mmol) were dissolved in nitromethane (20 mL)
and stirred overnight. 4-tert-Butylbenzyl bromide (0.0278 g,
0.122 mmol) and 3 mL of a saturated NaOTf(aq) were added and
the two-phase reaction stirred for 7 days. The organic layer was
separated, dried over anhydrous MgSO4 and evaporated. The
orange residue was taken up in MeCN (1 mL) and filtered. The
solvent was removed from the filtrate and the residue subjected
to column chromatography [SiO2: methanol–nitromethane–2 M
NH4Cl(aq) (6 : 1 : 3)]. Like fractions were combined and anion
exchanged with NaOTf(aq) to yield the products as orange–red
solids. Overall chemical yield 83%. 12.4OTf: 0.0189 g (70% of
Preparation of bis(crown ether), 16
To a solution of 4,4ꢀ-biphenol (0.044 g, 0.234 mmol) and
4 (0.213 g, 0.429 mmol) in acetonitrile (80 mL) was added
potassium carbonate (0.353 g, 2.55 mmol). The mixture was
refluxed for 4 days, cooled, filtered and then the solvent removed.
The residue was dissolved in chloroform (50 mL), washed with
water (2 × 50 mL), dried over anhydrous MgSO4. The solvent
was evaporated to yield a yellow residue. The crude material was
dissolved in chloroform (3 mL) and hexanes added to precipitate
the desired white solid, 16. Yield 0.136 g (52%). 1H NMR
1
total material) (Rf = 0.63). H NMR (500 MHz, CD3CN): d
3
3
3
9.31 (d, 4H, J = 6.6 Hz), 8.86 (d, 4H, J = 6.5 Hz), 8.24 (d,
4H, 3J = 6.6 Hz), 8.15 (d, 4H, 3J = 6.5 Hz), 7.52 (d, 4H, 3J =
(500 MHz, CDCl3): d 7.45 (d, 4H, J = 8.7 Hz), 6.99 (d, 4H,
3J = 8.7 Hz), 6.94–6.97 (m, 4H), 6.86–6.89 (m, 10H), 4.99 (s, 4H),
4.14–4.18 (m, 16H), 3.90–3.91 (m, 16H), 3.82 (s, 16H). Mp 151–
152 ◦C. HR-ESI-MS: m/z [16 + Na]+: calc.: 1129.4773, found:
1129.4790; [16 + 2Na]2+: calc.: 576.2335, found: 576.2343.
3
3
8.3 Hz), 7.36 (d, 4H, J = 8.3 Hz), 7.25 (t, 1H, J = 8.2 Hz),
7.03–7.05 (m, 2H), 6.89 (m, 1H), 6.80 (s, 1H), 6.63–6.69 (m, 5H),
6.57 (br s, 1H), 6.47–6.51 (m, 2H), 6.40–6.45 (m, 4H), 6.33 (dd,
1H, 4J = 1.5, 3J = 8.2 Hz), 5.68–5.72 (m, 4H), 5.60 (s, 4H), 5.05
(s, 2H), 4.51 (s, 2H), 3.97–4.14 (m, 32H), 3.65–3.80 (m, 16H),
Preparation of [2]rotaxane, 17.4OTf and [3]rotaxane, 18.8OTf
◦
1.31 (s, 18H). Mp 135–136 C. HR-ESI-MS: m/z [12.3OTf]+:
calc.: 2111.7158, found: 2111.7097. [12.2OTf]2+ 981.3819, found:
981.3876. [12.1OTf]3+: calc.: 604.6039, found: 604.6085. [12]4+:
calc.: 416.2149, found: 416.2225. 13.8OTf: 0.0131 g (30% of total
material) (Rf = 0.40). 1H NMR (500 MHz, CD3CN): d 9.33 (d,
8H, 3J = 6.8 Hz), 8.94 (d, 8H, 3J = 6.9 Hz), 8.28 (d, 8H, 3J =
6.8 Hz), 8.20 (d, 8H, 3J = 6.9 Hz), 8.94 (d, 8H, 3J = 6.9 Hz), 7.51
(d, 8H, 3J = 8.4 Hz), 7.41 (d, 8H, 3J = 8.4 Hz), 7.32 (t, 1H, 3J =
8.2 Hz), 6.81 (d, 2H, 4J = 1.6 Hz), 6.60–6.65 (m, 9H), 6.55 (dd,
2H, 4J = 1.6, 3J = 8.2 Hz), 6.39–6.42 (m, 4H), 5.61 (s, 8H), 4.63
(s, 4H), 4.00–4.06 (m, 48H), 1.31 (s, 36H). Mp 190–191 ◦C. HR-
ESI-MS: m/z [13.6OTf]2+: calc.: 1596.4877, found: 1596.4929.
[13.5OTf]3+: calc.: 1014.6745, found: 1014.6904. [13.4OTf]4+:
calc.: 723.7679, found: 723.7753. [13.3OTf]5+: calc.: 549.2239,
found: 549.2345. [13.2OTf]6+: calc.: 432.8612, found: 432.8674.
Crown ether 16 (0.0308 g, 0.0278 mmol) and 1.2OTf (0.0571 g,
0.111 mmol) were dissolved in nitromethane (20 mL) and stirred
overnight. 4-tert-Butylbenzyl bromide (0.0504 g, 0.222 mmol)
and 3 mL of a saturated NaOTf(aq) were added and the
two-phase reaction stirred for 7 days. The organic layer was
separated, dried over anhydrous MgSO4 and evaporated. The
orange residue was taken up in MeCN (1 mL) and filtered. The
solvent was removed from the filtrate and the residue subjected
to column chromatography [SiO2: methanol–nitromethane–2 M
NH4Cl(aq) (6 : 1 : 3)]. Like fractions were combined, the
solvent removed and anion exchanged with NaOTf(aq) to yield
the products as orange–red solids. Overall chemical yield 37%.
17.4OTf: 0.0167 g (69% of total material) (Rf = 0.59). 1H NMR
3
(500 MHz, CD3CN): d 9.33 (d, 4H, J = 6.8 Hz), 8.93 (d, 4H,
3
3
3J = 6.7 Hz), 8.26 (d, 4H, J = 6.8 Hz), 8.20 (d, 4H, J =
3
3
6.7 Hz), 7.58 (d, 2H, J = 8.8 Hz), 7.56 (d, 2H, J = 8.7 Hz),
7.52 (d, 4H, 3J = 8.4 Hz), 7.40 (d, 4H, 3J = 8.4 Hz), 7.07 (d, 2H,
3J = 8.7 Hz), 6.97–7.02 (m, 3H), 6.89–6.95 (m, 6H), 6.81 (d, 1H,
Preparation of [2]rotaxane, 14.4OTf and [3]rotaxane, 15.8OTf
Crown ether 9 (0.0151 g, 0.0146 mmol) and 1.2OTf (0.0188 g,
0.0366 mmol) were dissolved in nitromethane (20 mL)
and stirred overnight. 4-tert-Butylbenzyl bromide (0.0278 g,
0.122 mmol) and 3 mL of a saturated NaOTf(aq) were added and
the two-phase reaction stirred for 7 days. The organic layer was
separated, dried over anhydrous MgSO4 and evaporated. The
orange residue was taken up in MeCN (1 mL) and filtered. The
solvent was removed from the filtrate and the residue subjected
to column chromatography [SiO2: methanol–nitromethane–2 M
NH4Cl(aq) (6 : 1 : 3)]. Like fractions were combined and anion
exchanged with NaOTf(aq) to yield the products as orange–
red solids. Overall chemical yield 68%. 14.4OTf: 0.0139 g (62%
4J = 1.4 Hz), 6.64–6.68 (m, 3H), 6.53 (dd, 1H, J = 1.4, J =
8.2 Hz), 6.40–6.42 (m, 2H), 5.72 (d, 4H, J = 1.8 Hz), 5.62 (s,
4H), 5.04 (s, 2H), 4.60 (s, 2H), 4.00–4.13 (m, 32H), 3.78–3.81 (m,
8H), 3.68 (s, 8H), 1.30 (s, 18H). Mp 140–141 ◦C. HR-ESI-MS:
m/z [17.3OTf]+: calc.: 2187.7471, found: 2187.7874. [17.2OTf]2+:
calc.: 1019.3976, found: 1019.3996. 18.8OTf: 0.00881 g (31% of
4
3
1
total material) (Rf = 0.44). H NMR (500 MHz, CD3CN): d
3
3
9.33 (d, 8H, J = 6.9 Hz), 8.94 (d, 8H, J = 6.8 Hz), 8.26
3
3
(d, 8H, J = 6.9 Hz), 8.20 (d, 8H, J = 6.8 Hz), 7.63 (d, 4H,
3
3
3J = 8.7 Hz), 7.52 (d, 8H, J = 8.4 Hz), 7.40 (d, 8H, J =
3
4
8.4 Hz), 7.02 (d, 4H, J = 8.7 Hz), 6.81 (d, 2H, J = 1.3 Hz),
6.64–6.67 (m, 6H), 6.52 (dd, 2H, 4J = 1.3, 3J = 8.1 Hz), 6.40–
6.42 (m, 4H), 5.73 (s, 8H), 5.62 (s, 8H), 4.60 (s, 4H), 4.00–4.09
(m, 48H), 1.29 (s, 36H). Mp 175–176 ◦C. HR-ESI-MS: m/z
[18.6OTf]2+: calc.: 1634.5034, found: 1634.5197. [18.5OTf]3+:
calc.: 1040.0182, found: 1040.0862. [18.4OTf]4+: calc.: 742.7757,
found: 742.7834. [18.3OTf]5+: calc.: 564.4301, found: 564.4354.
[18.2OTf]6+: calc.: 445.5331, found: 445.5335.
1
of total material) (Rf = 0.61). H NMR (500 MHz, CD3CN):
3
3
d 9.30 (d, 4H, J = 6.8 Hz), 8.80 (d, 4H, J = 6.8 Hz), 8.15
(d, 4H, 3J = 6.8 Hz), 7.99 (d, 4H, 3J = 6.8 Hz), 7.56 (d,
3
3
4H, J = 8.4 Hz), 7.40 (d, 4H, J = 8.4 Hz), 6.82–6.97 (m,
3
10H), 6.60–6.72 (m, 5H), 6.48 (t, 1H, J = 8.3 Hz), 6.38–6.40
(m, 2H), 5.71 (s, 4H), 5.59 (s, 4H), 4.98 (s, 2H), 4.61 (s, 2H),
3.99–4.15 (m, 32H), 3.82–3.85 (m, 8H), 3.70–3.72 (m, 8H),
◦
1.31 (s, 18H). Mp 135–136 C. HR-ESI-MS: m/z [14.3OTf]+:
calc.: 2111.7158, found: 2111.7312. [14.2OTf]2+: calc.: 981.3819,
found: 981.3898. [14.OTf]3+: calc.: 604.6039, found: 604.6115.
[14]4+: calc.: 416.2149, found: 416.2171. 15.8OTf: 0.0138 g (38%
of total material) (Rf = 0.30). 1H NMR (500 MHz, CD3CN): d
Preparation of tris(crown ether), 19
To a solution of 1,3,5-tris(4-hydroxyphenyl)benzene (0.052 g,
0.147 mmol) and 4 (0.284 g, 0.571 mmol) in acetone (80 mL)
was added potassium carbonate (0.694 g, 5.02 mmol) and the
mixture was refluxed for 7 days. The reaction contents were
filtered and the filtrate was evaporated. The residue was dissolved
in chloroform (50 mL), washed with water (2 × 50 mL), dried
with anhydrous MgSO4 and evaporated to yield a yellow solid.
This material was dissolved in chloroform (3 mL) and hexanes
added to precipitate the desired white solid, 19. Yield 0.102 g
3
3
9.33 (d, 8H, J = 6.8 Hz), 8.94 (d, 8H, J = 6.8 Hz), 8.26 (d,
8H, 3J = 6.8 Hz), 8.19 (d, 8H, 3J = 6.8 Hz), 7.55 (d, 8H, 3J =
3
8.4 Hz), 7.44 (d, 8H, J = 8.4 Hz), 6.94 (s, 4H), 6.78 (d, 2H,
4J = 1.7 Hz), 6.63–6.65 (m, 6H), 6.50 (dd, 2H, J = 1.7 J =
4
3
7.8 Hz), 6.39–6.41 (m, 4H), 5.72 (s, 8H), 5.61 (s, 8H), 4.54 (s,
◦
4H), 4.00–4.06 (m, 48H), 1.29 (s, 36H). Mp 180–181 C. HR-
ESI-MS: m/z [15.6OTf]2+: calc.: 1596.4877, found: 1596.4932.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 3 9 3 – 1 4 0 1
1 3 9 9

View Article Online
(40%). 1H NMR (500 MHz, CDCl3): d 7.64 (s, 3H), 7.60 (d, 6H,
3J = 8.7 Hz), 7.05 (d, 6H, 3J = 8.7 Hz), 6.96–6.98 (m, 6H), 6.87–
6.88 (m, 15H), 5.02 (s, 6H), 4.13–4.19 (m, 24H), 3.90–3.92 (m,
polarization corrections and empirical absorption corrections,
based on redundant data at varying effective azimuthal angles,
were applied to the data set. The structure was solved by
direct methods, completed by subsequent Fourier syntheses
and refined with full-matrix least-squares methods against |F2|
data. All non-hydrogen atoms were refined anisotropically. The
thermal parameter for atom C(26) was restrained using the
ISOR command. There was evidence for a slight disorder for
one of the OCH2CH2O linkages but this was not modelled.
All hydrogen atoms were treated as idealized contributions.
Scattering factors and anomalous dispersion coefficients are
contained in the SHELXTL 5.03 program library12
◦
24H), 3.82 (s, 24H). Mp 115–116 C. HR-ESI-MS: m/z [19 +
Na]+: calc.: 1757.7445, found: 1757.7448.
Preparation of [2]rotaxane, 20.4OTf, [3]rotaxane, 21.8OTf and
[4]rotaxane, 22.12OTf
Crown ether 19 (0.053 g, 0.031 mmol) and 1.2OTf (0.110 g,
0.214 mmol) were dissolved in nitromethane (20 mL) and stirred
overnight. 4-tert-Butylbenzyl bromide (0.100 g, 0.440 mmol)
and 3 mL of a saturated NaOTf(aq) were added and the
two-phase reaction stirred for 7 days. The organic layer was
separated, dried over anhydrous MgSO4 and evaporated. The
orange residue was taken up in MeCN (1 mL) and filtered. The
solvent was removed from the filtrate and the residue subjected
to column chromatography [SiO2: methanol–nitromethane–2 M
NH4Cl(aq) (6 : 1 : 3) up to DMF–2 M NH4Cl(aq) (1 : 1)]. Like
fractions were combined and anion exchanged with NaOTf(aq)
to yield the products as orange–red solids. Overall chemical yield
85%. 20.4OTf: 0.0243 g (32% of total material) (Rf = 0.63). 1H
Crystal data. C31H38O9, M = 554.61, triclinic, space group
˚
P1 (no. 1), a = 8.5216(13), b = 8.6643(13), c = 10.4987(16) A, a =
◦
3
˚
92.857(3), b = 96.328(3), c = 113.673(3) , V = 701.82(18) A ,
Z = 1, Dc = 1.312 g cm−3, l(Mo-Ka) = 0.096 mm−1, colourless
block; 2474 independent measured reflections, F2 refinement,
R1 = 0.0961, wR2 = 0.1034 [I > 2r(I)], R1 = 0.2339, wR2 =
0.2423 (all data), goodness-of-fit = 1.42, 361 parameters, 9
restraints.
CCDC reference number 258420.
See http://www.rsc.org/suppdata/ob/b4/b418772e/ for cry-
stallographic data in .cif or other electronic format.
3
NMR (500 MHz, CD3CN): d 9.33 (d, 4H, J = 6.4 Hz), 8.90
3
3
(d, 4H, J = 6.5 Hz), 8.23 (d, 4H, J = 6.4 Hz), 8.16 (d, 4H,
3J = 6.5 Hz), 7.73–7.81 (m, 9H), 7.50 (d, 4H, J = 8.3 Hz),
3
3
7.39 (d, 4H, J = 8.3 Hz), 6.91–7.12 (m, 20H), 6.83 (d, 1H,
Acknowledgements
4J = 1.5 Hz), 6.62–6.64 (m, 3H), 6.58 (dd, 1H, J = 1.5, J =
8.2 Hz), 6.40–6.42 (m, 2H), 5.71 (d, 4H, J = 4.1 Hz), 5.61
(s, 4H), 5.08 (s, 4H), 4.65 (s, 2H), 4.02–4.17 (m, 40H), 3.77–
3.80◦(m, 16H), 3.64–3.66 (m, 16H), 1.30 (s, 18H). Mp 137–
138 C. HR-ESI-MS: m/z [20.2OTf]2+: calc.: 1333.5312, found:
1333.5374 [20.OTf]3+: calc.: 839.3701, found: 839.3750, [20]4+:
calc.: 592.2896, found: 592.2961. 21.8OTf: 0.036 g (33% of total
4
3
We thank the Natural Sciences and Engineering Council
of Canada for financial support of this research and Dr
Shuangquan Zhang for recording all ESI-MS.
References
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1
material) (Rf = 0.51). H NMR (500 MHz, CD3CN): d 9.34
3
3
(d, 8H, J = 6.8 Hz), 8.93 (d, 8H, J = 6.7 Hz), 8.26 (d, 8H,
3J = 6.8 Hz), 8.20 (d, 8H, J = 6.7 Hz), 7.81–7.85 (m, 9H),
3
7.51 (d, 8H, 3J = 8.4 Hz), 7.40 (d, 8H, 3J = 8.4 Hz), 7.13–7.15
3
3
(m, 2H), 7.08 (d, 6H, J = 8.7 Hz), 7.04 (d, 1H, J = 8.3 Hz),
6.93–6.97 (m, 4H), 6.89 (d, 2H, 3J = 8.3 Hz), 6.83 (d, 2H, 4J =
1.2 Hz), 6.64–6.66 (m, 4H), 6.56 (dd, 2H, 4J = 8.3, 3J = 1.2 Hz),
6.41–6.42 (m, 4H), 5.72 (d, 8H, J = 4.0 Hz), 5.62 (s, 8H), 5.09
(s, 2H), 4.64 (s, 4H), 4.01–4.14 (m, 56H), 3.77–3.81 (m, 8H),
3.66 (d, 8H, 3J = 1.9 Hz), 1.27 (s, 36H). Mp 165–166 ◦C. HR-
ESI-MS: m/z [21.6OTf]2+: calc.: 1948.6370, found: 1948.6509.
[21.5OTf]3+: calc.: 1249.4406, found: 1249.4468. [21.4OTf]4+:
calc.: 899.8425, found: 899.8655. [21.3OTf]5+: calc.: 690.0836,
found: 690.0938. [21.2OTf]6+: calc.: 550.2443, found: 550.2519.
22.12OTf: 0.0497 g (35% of total material) (Rf = 0.35). 1H NMR
(500 MHz, CD3CN): d 9.34 (d, 12H, 3J = 8.9 Hz), 8.95 (d, 12H,
3
3
3J = 8.9 Hz), 8.29 (d, 12H, J = 8.9 Hz), 8.22 (d, 12H, J =
3
8.9 Hz), 7.87 (s, 3H), 7.83 (d, 6H, J = 8.5 Hz), 7.73 (d, 12H,
3
3
J = 2.9 Hz), 7.50 (d, 12H, J = 8.4 Hz), 7.40 (d, 12H, J =
3
4
8.4 Hz), 7.09 (d, 6H, J = 8.7 Hz), 6.83 (d, 3H, J = 1.5 Hz),
6.69 (d, 3H, 3J = 8.2 Hz), 6.64–6.66 (m, 6H), 6.55 (dd, 3H, 4J =
1.5, 3J = 8.2 Hz), 6.39–6.42 (m, 6H), 5.63 (s, 12H), 4.64 (s, 6H),
4.01–4.10 (m, 72H), 1.27 (s, 54H). Mp 190–191 ◦C. HR-ESI-MS:
m/z [22.5OTf]7+: calc.: 626.1036, found 626.1077. LR-ESI-MS
[22.4OTf]8+: calc.: 529.2, found 529.2.
X-Ray structure determination of crown ether, 5
Colourless crystals of 5 were grown by slow diffusion of hexanes
into a saturated chloroform solution. Crystals were mounted
on a short glass fibre attached to a tapered copper pin and the
crystal cooled to 173.0(1) K. A full hemisphere of data were
collected with 30 s frames on a Bru¨ker APEX diffractometer
fitted with a CCD based detector. Decay (<1%) was monitored
by 50 standard data frames measured at the beginning and end
of data collection. The data was relatively weak due to the poor
quality of the crystals. Diffraction data and unit-cell parameters
were consistent with the assigned space group. Lorentzian
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