Translational Isomerism in Some Two- and Three-Station [2]Rotaxanes

Article abstract of DOI:10.1021/jo9612584

The template-directed syntheses of three [2]rotaxanes are described. They all have dumbbell , components, with both hydroquinone and resorcinol rings inserted into polyether chains terminated by tetraarylmethane stoppers, that become encircled during the key self-assembly processes by the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), with its two π-electron deficient bipyridinium units. It has been demonstrated by low-temperature ¹H NMR spectroscopy that the π-electron deficient tetracationic cyclophane has a remarkably high preference to reside around the hydroquinone ring in these molecular shuttles. This observation illustrates how a very small constitutional difference-hydroquinone versus resorcinol recognition sites-can lead to the overwhelming preference for one translational isomer over another in this particular range of [2]rotaxanes.

Full text of DOI:10.1021/jo9612584

3062
J . Org. Chem. 1997, 62, 3062-3075
Tr a n sla tion a l Isom er ism in Som e Tw o- a n d Th r ee-Sta tion
[2]Rota xa n es†
David B. Amabilino, Peter R. Ashton, Sue E. Boyd, Marcos Go´mez-Lo´pez, Wayne Hayes, and
J . Fraser Stoddart*
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
Received J uly 3, 1996X
The template-directed syntheses of three [2]rotaxanes are described. They all have dumbbell
components, with both hydroquinone and resorcinol rings inserted into polyether chains terminated
by tetraarylmethane stoppers, that become encircled during the key self-assembly processes by
the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), with its two π-electron deficient
1
bipyridinium units. It has been demonstrated by low-temperature H NMR spectroscopy that the
π-electron deficient tetracationic cyclophane has a remarkably high preference to reside around
the hydroquinone ring in these molecular shuttles. This observation illustrates how a very small
constitutional differenceshydroquinone versus resorcinol recognition sitesscan lead to the
overwhelming preference for one translational isomer over another in this particular range of
[2]rotaxanes.
In tr od u ction
the supramolecular chemist has adopted concepts such
as self-assembly,6 self-replication,7 and self-organization8
that are prolific in biology and applied them successfully
into the artificial world of synthetic chemistry. The first
inefficient syntheses9 of catenanes and rotaxanes relied
upon the statistical threading of a linear component
through a cyclic one. However, it has been possible to
design and synthesize well-defined compatible and comple-
mentary molecular components with the ability to rec-
ognize each other and then to self-assemble them spon-
taneously into molecular assemblies by employing
noncovalent bonding interactions. Notable examples,
which illustrate the potential of the self-assembly strat-
egy, have been described by Sauvage and co-workers,10
who have designed and prepared an impressive array of
catenanes, rotaxanes, and knots using a copper(I)-based
template procedure. Hydrogen bonding has been em-
ployed more recently to self-assemble another class of
catenanes and rotaxanes.11 The ability of macrocyclic
polyethers to form pseudorotaxane-like inclusion com-
Supramolecular chemists1 employ the very same non-
covalent bonding interactionsse.g., π-π stacking interac-
tions2 and hydrogen bonds3swhich regulate biological
systems and processes in order to construct a series of
fascinating unnatural interlocked molecular compounds,4
such as the catenanes and rotaxanes.5 In recent times,
† Molecular Meccano. 17. For Part 16, see: Asakawa, M.; Ashton,
P. R.; Boyd, S. E.; Brown, C. L.; Menzer, S.; Pasini, D.; Stoddart, J . F.;
Tolley, M. S.; White, A. J . P.; Williams, D. J .; Wyatt, P. G. Chem. Eur.
J . 1997, 3, 463-481.
X Abstract published in Advance ACS Abstracts, April 1, 1997.
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Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3063
plexes with linear secondary dialkylammoniun salts12
provides supramolecular chemists with further alterna-
tive building blocks for the construction of mechanically-
interlocked molecular assemblies and supramolecular
arrays.13
Sch em e 1
Rotaxanes, although lacking the topological appeal of
the catenanes, have been the subject of intense research
because of their abacus-like geometry which makes them
an obvious initial starting point for the investigation of
switching phenomena in molecular systems.14 They can
also be incorporated into polymers, i.e., polyrotaxanes,15
bringing together the scientific disciplines of supramo-
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formed by the self-assembly of π-electron rich (e.g.,
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and rotaxanes containing these building blocks remains
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and synthesized. It has been possible to modify the
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3064 J . Org. Chem., Vol. 62, No. 10, 1997
Amabilino et al.
Sch em e 2
Sch em e 3
two nondegenerate π-electron rich stations, one of them
a hydroquinone ring and the other a p-xylene,19 an
indole,20 or a tetrathiafulvalene unit.21 Furthermore, a
molecular switch,22 inspired by the translational isomer-
ism displayed in these desymmetrized [2]rotaxanes, has
been constructed in which one of the π-electron rich
stations is a benzidine unit and the other one is a
biphenol unit. In the case of this particular molecular
shuttle, the control of the movement of the tetracationic
cyclophane can be effected either chemically or electro-
chemically.
been self-assembled23 previously in 15% yield (Scheme
1). It was observed that changing the constitution of the
macrocyclic polyether not only affects drastically the
efficiency of the self-assembly process but it also alters
the nature of the dynamic motion of the two interlocked
rings with respect to each other. Variable temperature
1H NMR spectroscopic studies carried out on a CD3COCD3
solution of 2‚4PF6 revealed the existence (Scheme 2) of
two translational isomers, A and B.23 The translational
isomer ratio A:B was found to be 98:2 at 253 K. It is
noteworthy that this remarkable preference for the
A [2]catenane, 2‚4PF6, incorporating a resorcinol unit
(1,3-dihydroxybenzene) in the macrocyclic polyether com-
ponent, namely, (p-phenylene)(m-phenylene)-33-crown-
10 (1), with the tetracationic cyclophane cyclobis(paraquat-
p-phenylene) as the π-electron deficient component, has
(19) Ashton, P. R.; Bissell, R. A.; Spencer, N.; Stoddart, J . F.; Tolley,
M. S. Synlett 1992, 914-918.
(20) Ashton, P. R.; Bissell, R. A.; Go´rski, R.; Philp, D.; Spencer, N.;
Stoddart, J . F.; Tolley, M. S. Synlett 1992, 919-922.
(21) Ashton, P. R.; Bissell, R. A.; Spencer, N.; Stoddart, J . F.; Tolley,
M. S. Synlett 1992, 923-926.
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(London) 1994, 369, 133-137.
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Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3065
Sch em e 5
F igu r e 1. Mass spectrum of the two-station [2]rotaxane
23‚4PF6.
Sch em e 4
different translational isomers and how we are able to
conclude that the high translational selectivity observed
in the [2]catenane 2‚4PF6 does translate into the analo-
gous [2]rotaxanes. In addition, the translational selectiv-
ity displayed by the three new molecular shuttles gives
information about the preferential sites of residence of
the π-electron deficient tetracationic cyclophane, not only
in relation to the stereoelectronic nature of the π-electron
rich stations but also in respect to the symmetries of the
π-electron rich dumbbell components. All of this infor-
mation improves our understanding of the nature of the
noncovalent bonding interactions which regulate the self-
assembly processes, enabling the future construction of
functioning molecular assemblies and supramolecular
arrays.
inclusion of the hydroquinone ring within the cavity of
the tetracationic cyclophane was exhibited for 2‚4PF6sa
very simple desymmetrized [2]catenane.
Resu lts a n d Discu ssion
In this paper, we report on the self-assembly of three
new [2]rotaxanes containing hydroquinone and resorcinol
rings in their dumbbell components. We show how H
Syn th esis. The first objective was to synthesize a
desymmetrized dumbbell compound, comprising one re-
sorcinol and one hydroquinone ring as the potential
π-electron rich recognition sites. In order to achieve this
1
NMR spectroscopic studies provide information about the

3066 J . Org. Chem., Vol. 62, No. 10, 1997
Amabilino et al.
Sch em e 6
Sch em e 7
goal, the synthetic strategy outlined in Scheme 3 was
applied in the first instance. An excess of resorcinol was
reacted with benzyl bromide, under mildly basic condi-
tions, to produce the phenol 3.24 Alkylation of the phenol
3 with the tosylate 420 in the presence of base yielded
the benzyl-protected phenol 5 in good yield. Hydro-
genolysis of the O-benzyl groups in the masked phenol
5, under standard conditions, afforded the phenol 6 in
97% yield.
The other half of the dumbbell compound, comprising
the π-electron rich hydroquinone ring, was synthesized
according to the route outlined in Schemes 4 and 5.
Commercially available 4-(benzyloxy)phenol (7) was alky-
lated with 2-(2-(2-chloroethoxy)ethoxy)ethanol in the
presence of base to afford the alcohol 8. Tosylation of
the alcohol 8 yielded the corresponding tosylate 9, which
was then reacted with the phenol 1020 under basic
conditions to produce the protected phenol 11. Subse-
quent deprotection using standard procedures gave a 95%
yield of the phenol 12, which was further alkylated with
2-(2-(2-chloroethoxy)ethoxy)ethanol to produce the alco-
hol 13, which was then reacted with tosyl chloride in
the presence of triethylamine and DMAP to give the
tosylate 14.
The unsymmetrical dumbbell compound 15, comprising
one hydroquinone ring and one resorcinol ring as the
π-electron-donating recognition sites, was constructed
(Scheme 6) by coupling the phenol 6 and the monotosy-
late 14 under mildly basic conditions.
(24) Fitton, A. O.; Ramage, G. R. J . Chem. Soc. 1962, 4870-4874

Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3067
Sch em e 8
Sch em e 9
The syntheses of the symmetrical dumbbell compounds
were achieved by following a similar synthetic strategy:
it is outlined in Schemes 7 and 8. Resorcinol was
dialkylated with tosylate 9 under basic conditions to yield
the protected bisphenol 16. Deprotection by hydro-
genolysis of both benzyloxy groups afforded the corre-
sponding bisphenol 17 which was then reacted with 2
molar equiv of the tosylate 4 in the presence of base to
produce (Scheme 7) the symmetrical dumbbell compound
18 containing one resorcinol ring sandwiched between
two hydroquinone rings within a polyether chain.
(Scheme 8) in 60% by reaction under basic conditions of
2 molar equiv of the phenol 6 with the bistosylate 19 to
produce the symmetrical dumbbell compound 20.
The self-assembly of the unsymmetrical [2]rotaxane
23‚4PF6 was achieved (Scheme 9) in 11% yield by stirring
1 molar equiv of the π-electron rich dumbbell compound
15 in the presence of 3 molar equiv of the bipyridinium
salt 21‚2PF6 and 1.2 molar equiv of 1,4-bis(bromometh-
yl)benzene (22) in a DMF solution at room temperature
and ambient pressure (Scheme 9), followed by counterion
exchange with NH4PF6/H2O to yield the hexafluorophos-
phate salt 23‚4PF6. The mass spectrum (Figure 1) of
23‚4PF6 reveals peaks corresponding to the molecular ion
The analogous symmetrical dumbbell compound 20,
comprised of two resorcinol rings sandwiching one hyd-
roquinone ring within a polyether chain, was synthesized

3068 J . Org. Chem., Vol. 62, No. 10, 1997
Amabilino et al.
Sch em e 10
Sch em e 11
and the molecular ion less one, two, and three hexafluro-
phosphate counterions.
The symmetrical [2]rotaxanes 24‚4PF6 and 25‚4PF6,
comprising the dumbbell components 18 and 20, respec-

Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3069
1
F igu r e 2. Partial H NMR spectrum of 23‚4PF6 in CD3COCD3 at 304 K.
tively, were self-assembled in 12% and 14% yields,
employing conditions identical to those used for the self-
assembly of the [2]rotaxane 23‚4PF6 (Schemes 10 and
11).
in a linear system does not affect the self-assembly
processes as much as that in the case of a [2]catenane.
1H NMR Sp ectr oscop y. The 1H NMR spectra re-
corded for the [2]rotaxanes 23‚4PF6, 24‚4PF6, and 25‚4PF6
exhibit marked temperature dependencies in accordance
with the highly fluxional solution state structures ex-
pected for mechanically-interlocked compounds.
The yields of the [2]rotaxanes are relatively low in
comparision to the 32% yield reported for the self-
assembly of the prototypical molecular shuttle18 in which
the symmetrical linear dumbbell component contains two
π-electron rich hydroquinone rings. Nonetheless, the
yields of 23‚4PF6, 24‚4PF6, and 25‚4PF6 seem to be of
similar magnitudes to those reported for the self-as-
sembly of other molecular shuttles in which one of the
hydroquinone rings is replaced by a different π-electron
rich unit.
It can be concluded that the presence of the meta-
substituted resorcinol ring in the linear polyether chain
undermines the efficiency of the self-assembly processes
when compared to the reference situation where only
para-substituted hydroquinone rings are present in the
dumbbell components. Nevertheless, the decrease in the
efficiency of the self-assembly process is not as dramatic
as that observed for the related [2]catenanes. This
difference undoubtedly reflects the inclusion of a meta-
substituted benzene ring in the macrocyclic polyether
component which forces the crown ether to adopt a
conformation that disrupts the molecular recognition
between the individual molecular precursors, thus hin-
dering the self-assembly process. On the other hand, the
dumbbell component possesses much more conforma-
tional freedom than do the macrocyclic polyether analogs,
and so the inclusion of meta-substituted benzenoid rings
The 1H NMR spectrum (400 MHz, CD3COCD3) of
23‚4PF6 at room temperature (Figure 2) shows largely
broadened or averaged signals. In particular, only one
resonance is observed for each of the R and â protons on
the bipyridinium units of the tetracationic cyclophane.
Process 1, i.e., the shuttling of the tetracationic cyclo-
phane back and forth between the nondegenerate π-elec-
tron rich recognition sites (Scheme 9), is therefore
occurring at a rate comparable to or greater than that of
1
the 400 MHz H NMR time scale at ambient tempera-
tures. Upon cooling of the solution, the spectra sharpen
(Figure 3) initially such that, at 240 K, resonances
attributable to the major translational isomer 1, i.e., the
species in which the tetracationic cyclophane resides on
the hydroquinone station, are well resolved. The assign-
ment of the resonances was assisted by two-dimensional
COSY and NOESY experiments. The corresponding
resonances expected for the minor translational isomer
2 are, however, broad and indistinct by comparison. The
reason for this phenomenom is probably associated in
part with a further site-exchange process occurring as a
result of the included resorcinol ring departing from the
cavity of the tetracationic cyclophane, re-orienting itself,
and re-entering the cavity.

3070 J . Org. Chem., Vol. 62, No. 10, 1997
Amabilino et al.
1
F igu r e 3. Partial H NMR spectrum of 23‚4PF6 in CD3COCD3 at 240 K.
(Hb and Hd), and a further apparent triplet (Hc) resonat-
ing at δ 5.87 (J ≈ 1 Hz), δ 6.15 and 6.35, and δ 6.85 (J ≈
7 Hz), respectively. Similarly, resonances corresponding
to the protons of the linking phenylene rings within the
tetraarylmethane stoppers appear as two different AA′XX′
systems, resonating at δ 6.58 and 6.97 and δ 6.97 and
7.20, respectively. The isolated resonances were com-
pared to the overlapping resonances for the R-protons of
the bipyridinium units, as illustrated in Figure 4. This
region shows the two doublets expected for the chemically
nonequivalent R-protons of the bipyridinium units in the
desymmetrized tetracationic cyclophane associated with
the major translational isomer, resonating on top of a
broad signal attributable to the minor translational
isomer. As this region must account for all the tetraca-
tionic cyclophane present in both translational isomers
of the [2]rotaxane, a not unreasonable estimate of the
relative concentration of the minor translational isomer
present in the solution at this temperature can be
obtained by simple subtraction of the appropriately-
weighted integral intensity. Thus, the relative recogni-
tion-site occupancy for the tetracationic cyclophane of the
[2]rotaxane 23‚4PF6 in CD3COCD3 solution at 240 K was
calculated as 2:1 in favor of hydroquinone occupancy over
that of resorcinol occupancy.
F igu r e 4. Partial 1H NMR spectrum of 23‚4PF6 in CD3COCD3
at 240 K depicting the shift region of the R-bipyridinium
protons and the region for the resorcinol Ha proton.
Relative recognition-site occupancies were calculated
by comparison of the net integral intensities of the
isolated resonances observed for the major translational
isomer with the total integral intensity of the character-
istic chemical shift region for the R-protons on the
bipyridinium units (Figure 4). Specifically, the signals
corresponding to the unoccupied resorcinol station show
the expected apparent triplet (Ha), two double doublets
Unfortunately, further cooling of the solution resulted
in only further broadening of the resonances to the extent
that, at temperatures around 200 K (400 MHz), no
signals were clearly resolved. The increasing complexity
of the spectra with decreasing temperature could result
from the system folding itself (Scheme 12) in order to

Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3071
Sch em e 12
maximize the effectiveness of the “alongside” interaction
between the tetracationic cyclophane and the unoccupied
π-electron rich recognition site. Resolution of this issue
could only be accomplished using much higher field
strengths and has not been explored further here. It is
noteworthy, however, that the relative site occupancy
observed for the analogous [2]catenane23sa system in
which the two π-electron rich components are incorpo-
rated into a crown ether ring and are thus preorganized
for efficient “inside” and “alongside” complexation of the
tetracationic cyclophanesis much more strongly weighted
in favor of hydroquinone occupation at the expense of
resorcinol occupation.
The three-station [2]rotaxane 25‚4PF6, in which a
hydroquinone station is sandwiched between two resor-
cinol units, behaves in a manner similar to the [2]rotax-
anes 23‚4PF6 and 24‚4PF6. The 1H NMR spectrum
recorded in CD3COCD3 at 220 K (400 MHz) shows well-
resolved resonances for the protons corresponding to the
alongside resorcinol rings. A broad apparent singlet (Ha)
at δ 5.88, two double doublets (Hd/b) at δ 6.13 and 6.45,
and an apparent triplet (Hc) at δ 7.18 (J ≈ 7 Hz),
corresponding to the major translational isomer 1 (Scheme
11), where the hydroquinone ring is included within the
cavity of the tetracationic cyclophane, are observed. The
signals corresponding to the linking phenylene rings
within the tetraarylmethane stoppers resonate as a
single AA′BB′ (He/f) system at δ 6.98 and 7.16 for the
major translational isomer, indicating the presence of a
symmetrical [2]rotaxane. The relative recognition-site
occupancy calculated for 25‚4PF6 in CD3COCD3 at 220
K was 8:1 in favor of translational isomer 1 over
translational isomer 2. This high selectivity can be
explained on the basis of the most favored geometry in
solution (Scheme 12), wherein the tetracationic cyclo-
phane resides around the central hydroquinone ring,
leaving the two π-electron deficient bipyridinium units
of the tetracationic cyclophane to interact in an “exo”
fashion with the two alongside π-electron rich resorcinol
rings, resulting in the tetracationic cyclophane being
sandwiched by the two “free” resorcinol rings, as observed
in other linear pseudorotaxane systems.23b By adopting
this geometry, the rotaxane gains some extra stabilizing
interactions.
The behavior of the three-station [2]rotaxane 24‚4PF6
is very similar to that of 23‚4PF6. The main difference
comes from the symmetrical nature of the dumbbell
component of 24‚4PF6, comprising two degenerate hyd-
roquinone stations. The shuttling of the tetracationic
cyclophane gives rise to two different translational
isomers, 1 and 2, as depicted in Scheme 10. The 1H NMR
spectrum (400 MHz, CD3COCD3) of 24‚4PF6 at 240 K
(Figure 5) shows well-resolved resonances attributable
to the major translational isomer 1. The signals corre-
sponding to the protons of the unoccupied resorcinol ring
can also be observed: they are an apparent triplet (Ha)
at δ 5.70 (J ≈ 1 Hz), two overlapping double doublets
(Hb/d) centered on δ 6.25, and another apparent triplet
(Hc) centered on δ 6.84 (J ≈ 7 Hz). The signals for the
protons corresponding to the linking phenylene rings
within the tetraarylmethane stoppers resonate as two
different AA′XX′ (He/f and Hg/h) systems with δ 7.15 and
6.91 and δ 6.96 and 6.57. These two AA′XX′ systems
correspond to the major translational isomer 1, where
the tetracationic cyclophane is residing on one of the
degenerate hydroquinone rings. No isolated resonances
for the minor translational isomer 2 can be observed. The
relative recognition-site occupancy for the tetracationic
cyclophane in 24‚4PF6 in CD3COCD3 at 240 K was
calculated in the same fashion as for that described in
23‚4PF6. It revealed a 4:1 ratio in favor of translational
isomer 1 over translational isomer 2.
Con clu sion s
The self-assembly of three novel [2]rotaxanes, 23‚4PF6-
25‚4PF6, containing resorcinol and hydroquinone sta-
tions, has been achieved in reasonable yields (11-12%).
Although these yields are lower than that (32%) for the
self-assembly of a [2]rotaxane comprising two hydro-
quinone rings in the dumbbell component,18 they are
similar to those obtained when one of the hydroquinone
rings is replaced by another π-electron rich station.19-21

3072 J . Org. Chem., Vol. 62, No. 10, 1997
Amabilino et al.
1
F igu r e 5. Partial H NMR spectrum of the [2]rotaxane 24‚4PF6 in CD3COCD3 at 240 K.
Ta ble 1. Rela tive Site Occu p a n cy for
bonding interactions (Table 1). The [2]rotaxane 25‚4PF6
enjoys the highest selectivity of one translational isomer
over the other, and therefore it represents the first step
in the construction of abacus-like molecular structures
with switching capabilities that could be controlled by
external stimuli.
The isomer selectivities observed for the linear [2]ro-
taxanes are not nearly as high as that for the analogous
[2]catenane 2‚4PF6. This observation is an interesting
one that merits further investigation by computational
methods. These investigations are underway.
Resor cin ol-Con ta in in g Molecu la r Assem blies As
Deter m in ed by 1H NMR Sp ectr oscop y
temperature
(K)
site
compound
solvent
occupancya
2‚4PF6
CD3COCD3
CD3COCD3
CD3COCD3
CD3COCD3
253
240
240
220
98:2
2:1
4:1
23‚4PF6
24‚4PF6
25‚4PF6
8:1
a
The site occupancy is always such that the major translational
isomer has the cyclobis(paraquat-p-phenylene) tetracationic com-
ponent encircling the hydroquinone ring in the other component.
There is a decrease in the efficiency of the self-assembly
process when one of the hydroquinone stations is replaced
by a resorcinol one, but the effect is not as dramatic as
that observed in the case of the corresponding [2]cat-
enane system.
Exp er im en ta l Section
Gen er a l P r oced u r es. Solvents were used as supplied,
with the exception of the following: dimethylformamide (DMF)
was distilled from calcium hydride under reduced pressure and
acetonitrile (MeCN) was distilled under nitrogen from calcium
hydride. Developed thin layer chromatography (TLC) plates
were air-dried, scrutinized under a UV lamp, and, if necessary,
then either sprayed with cerium(IV)sulfate-sulfuric acid
reagent and heated to ca. 100 °C or developed in an iodine
tank. Microanalyses were performed by the University of
Sheffield Microanalytical Service. Melting points were deter-
mined in an open capillary tube and are uncorrected. 1H
nuclear magnetic resonance (NMR) spectra were recorded at
either 300 or 400 MHz using the deuterated solvent as a lock
and residual protonated solvent or tetramethylsilane as an
internal reference. 13C NMR spectra were recorded at either
75 or 100 MHz.
1
The variable temperature H NMR spectroscopic stud-
ies reveal that [2]rotaxanes 23‚4PF6-25‚4PF6 exist as
two different translational isomers in all three cases. The
two-station [2]rotaxane 23‚4PF6 displays an approxi-
mately 2:1 selectivity for the major translational isomer
1 over the translational isomer 2. The three-station
[2]rotaxane 24‚4PF6 shows a selectivity of approximately
4:1. The difference in selectivity can be explained easily
on the basis that the [2]rotaxane possesses two hydro-
quinone stations and only one resorcinol one. Finally,
the three-station [2]rotaxane 25‚4PF6 exhibits the highest
selectivity of 8:1 as a result of folding in solution (Scheme
12) in order to maximize the alongside noncovalent
3-(Ben zyloxy)p h en ol24 (3). A solution of resorcinol (50 g,
450 mmol) and K2CO3 (6.21 g, 45 mmol) in dry MeCN (200

Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3073
mL) was refluxed under nitrogen for 1 h. A solution of benzyl
bromide (7.7 g, 0.045 mol) in dry MeCN (250 mL) was added
dropwise over 1 h to the reaction mixture, the solution was
allowed to reflux for 4 days under nitrogen with vigorous
stirring. The solution was cooled down to room temperature
and filtered, and the solvent was removed in vacuo. The
residual oil was taken up in CH2Cl2 (200 mL) and washed with
dilute aqueous HCl (pH 3, 2 × 200 mL) and then brine (2 ×
200 mL). The organic phase was dried (MgSO4) and the
solvent removed in vacuo. Column chromatography (SiO2,
CH2Cl2) afforded the phenol 3 as a white solid (6.29 g, 70%):
mp 51-51.8 °C (lit.24 mp 50-51 °C); IR (NaCl) 3424, 3031,
2936, 2872, 2433, 1594, 1498, 1490, 1454, 1381, 1238, 1216,
1146, 1080, 1026, 940, 838, 764, 696 cm-1; EIMS 200 (M+); 1H
NMR (CDCl3, 300 MHz, 25 °C) δ 5.01 (s, 2H), 6.12 (s, 1H),
6.49-6.47 (dd, 1H, J ) 7, 1 Hz), 6.62-6.60 (dd, 1H, J ) 7, 1
Hz), 7.15 (t, 1H, J ) 7 Hz), 7.45-7.34 (m, 5H); 13C NMR
(CDCl3, 75 MHz) δ 70.2, 102.7, 107.5, 108.4, 127.6, 128.1,
128.7, 130.3, 136.9, 156.8, 160.2.
1-[2-(2-(2-(Tr itylph en oxy)eth oxy)eth oxy)eth oxy]-3-(ben -
zyloxy)ben zen e (5). A solution of 3-(benzyloxy)phenol (3)
(1.79 g, 8.9 mmol), K2CO3 (1.8 g, 13 mmol), and a catalytic
amount of LiBr in dry MeCN (100 mL) was mixed and heated
under reflux for 1 h in a nitrogen atmosphere. A solution of
tosylate20 4 (5.58 g, 8.9 mmol) in dry MeCN (100 mL) was
added dropwise over 30 min to the reaction mixture; the
solution was heated under reflux for 4 days under nitrogen
with vigorous stirring. The solution was allowed to cool to rt
before it was filtered and the solvent removed in vacuo. The
residual oil was dissolved in CH2Cl2 (200 mL) and washed with
dilute HCl (pH 3, 2 × 200 mL) and brine (2 × 200 mL). The
organic phase was dried (MgSO4) and the solvent removed in
vacuo to yield the protected phenol 5 as a yellow oil (4.82 g,
84%): IR (NaCl) 3056, 2924, 2873, 1594, 1508, 1491, 1448,
1250, 1182, 1154, 829, 748, 702 cm-1; LSIMS m/z 650 (M+);
1H NMR (CDCl3, 300 MHz, 25 °C) δ 3.78 (s, 4H), 3.90-3.86
(m, 4H), 4.15-4.12 (m, 4H), 5.06 (s, 2H), 6.57-6.54 (dd, 1H,
J ) 7, 1 Hz), 6.62-6.60 (m, 2H), 6.83-6.80 (AA′BB′ system,
2H, J ) 8 Hz), 7.14-7.11 (AA′BB′ system, 2H, J ) 8 Hz), 7.30-
7.19 (m, 16H), 7.48-7.35 (m, 5H); 13C NMR (CDCl3, 75 MHz)
δ 64.3, 67.3, 67.5, 69.8, 70.0, 70.8, 102.1, 107.2, 107.4, 113.4,
125.9, 127.4, 127.5, 127.9, 128.6, 129.9, 131.1, 132.2, 139.2,
147.1, 156.8, 160.0; HRMS calcd for C44H42O5 [M]+ 650.3032,
found 650.3041 (err -1.3 ppm).
1-[2-(2-(2-(Tr itylp h en oxy)eth oxy)eth oxy)eth oxy]-3-h y-
d r oxyben zen e (6). A solution of 5 (5.57 g, 8.7 mmol) in
CHCl3 (200 mL) was added to a suspension of Pd/C (5%, 1.5
g) in MeOH (200 mL). The suspension was stirred for 12 h as
hydrogen gas was bubbled into the mixture. The suspension
was filtered through Celite, and the solvent was removed in
vacuo to produce phenol 6 as a white solid (4.66 g, 97%).
Phenol 6 is prone to oxidation, and so the next reaction was
carried out immediately using the crude product.
1-[2-(2-(2-H y d r o x y e t h o x y )e t h o x y )e t h o x y ]-4-(b e n -
zyloxy)b en zen e20 (8). A stirred suspension of 4-(benzyl-
oxy)phenol (15 g, 75 mmol) and K2CO3 (35 g, 250 mmol) in
dry MeCN (250 mL) was brought to reflux under nitrogen. 2-(2-
(2-Chloroethoxy)ethoxy)ethanol (22 mL) was added dropwise,
and the resulting mixture was stirred at reflux under nitrogen
for 3 days. The suspension was filtered and the solvent re-
moved in vacuo. CH2Cl2 (200 mL) was added to the residue;
the resultant mixture was washed with dilute HCl (pH 3, 3 ×
250 mL) and then distilled H2O (3 × 250 mL). The organic
phase was dried (MgSO4) and the solvent removed in vacuo,
yielding product 8 as a white powder (21.05 g, 84%): mp 49-
50 °C; IR (NaCl) 3298, 2935, 2879, 1511, 1452, 1237, 1115,
1066, 1029, 952, 833, 737 cm-1; EIMS m/z 332 (M+); 1H NMR
(CDCl3, 300 MHz, 25 °C) δ 3.50-3.63 (m, 2H), 3.68-3.74 (m,
4H), 3.82-3.85 (t, 2H), 4.07-4.10 (m, 4H), 5.01 (s, 2H), 6.83-
6.91 (m, 4H), 7.28-7.44 (m, 5H); 13C NMR (CDCl3, 75 MHz) δ
61.8, 68.1, 69.9, 70.4, 70.7, 70.8, 72.5, 115.7, 115.8, 127.5, 127.9,
128.5, 137.3, 153.1, 153.2; HRMS calcd for C19H24O5 [M]+
332.1623, found 332.1616 (err 2.3).
of DMAP in dried CH2Cl2 was prepared and cooled to 0 °C
under nitrogen. A solution of p-toluenesulfonyl chloride (2.07
g, 10 mmol) in dry CH2Cl2 (300 mL) was added dropwise with
continuous stirring over 2 h to the reaction mixture; the
solution was allowed to warm up to rt while being stirred
under nitrogen for 4 h. The solution was filtered and the
solvent removed in vacuo. CH2Cl2 (200 mL) was added to the
residue, and the solution was washed with dilute HCl (pH 3,
2 × 250 mL) and distilled H2O (2 × 250 mL). The organic
layer was dried (MgSO4) and the solvent was removed in vacuo
to yield a yellow oil which was recrystallized from hexane:
EtOAc (8:2) to give a pale yellow powder. This powder was
washed thoroughly with hexane to give product 9 as a white
powder (3.7 g, 82%): mp 52-52 °C; IR (NaCl) 2869, 2360, 1597,
1506, 1353, 1189, 1175, 1096, 920, 712, 662 cm-1; LSIMS 486
(M+); 1H NMR (CDCl3, 300 MHz, 25 °C) δ 2.43 (s, 3H), 3.59-
3.62 (m, 2H), 3.64-3.71 (m, 6H), 3.78-3.81 (m, 2H), 4.04-
4.07 (m, 2H), 5.01 (s, 2H), 6.82-6.92 (m, 4H), 7.31-7.44 (m,
7H), 7.79-7.81 (AA′BB′ system, 2H, J ) 8 Hz); 13C NMR
(CDCl3, 75.5 MHz) δ 21.6, 68.1, 68.7, 69.2, 69.9, 70.7, 70.8,
70.8, 115.6, 115.8, 127.5, 127.9, 128.0, 128.5, 129.8, 133.1,
137.3, 144.8, 153.2; HRMS calcd for C26H30O7S [M]+ 486.1712,
found 486.1700 (err 2.5).
1-[2-(2-(2-(Tr itylph en oxy)eth oxy)eth oxy)eth oxy]-4-(ben -
zyloxy)ben zen e (11). A stirred suspension of the vacuum-
dried tritylphenol (10) (1.64 g, 5 mmol) and K2
CO3 (2.86 g,
20.7 mmol) in dry MeCN (12 mL) was brought to reflux under
nitrogen. A solution of tosylate 9 (2 g, 4.11 mmol) in dry MeCN
(15 mL) was added dropwise over 30 min. The resulting
mixture was stirred for 4 days at 80 °C under nitrogen. The
cream-colored suspension was filtered and the solvent removed
in vacuo. The residual oil was taken up in CH2
Cl2 (100 mL)
and washed with dilute HCl (pH 3, 3 × 100 mL) and distilled
H2O (3 × 100 mL). The organic phase was dried (MgSO4) and
the solvent removed in vacuo to yield a yellow oil. Column
chromatography (SiO2, CH2Cl2) afforded 11 as a white solid
(2.19 g, 45%): mp 80.8-81 °C; IR (NaCl) 3056, 3030, 2920,
2871, 1507, 1452, 1229, 1125, 826, 747, 702 cm-1; EIMS m/z
650 (M+); 1H NMR (CDCl3, 300 MHz, 25 °C) δ 3.77 (s, 4H),
3.84-3.88 (m, 4H), 4.08-4.14 (m, 4H), 5.01 (s, 2H), 6.81-6.84
(AA′BB′ system, 2H, J ) 8 Hz), 6.85-6.93 (m, 4H), 7.11-7.14
(AA′BB′ system, 2H, J ) 8 Hz), 7.18-7.46 (m, 20H); 13C NMR
(CDCl3, 75 MHz) δ 64.4, 67.3, 68.1, 69.9, 70.0, 70.7, 70.9, 113.4,
115.7, 115.9, 125.9, 126.2, 127.5, 127.5, 127.9, 128.6, 131.2,
132.2, 137.3, 139.2, 147.1, 153.2, 153.2, 156.8. Anal. Calcd
for C44H42O5: C, 81.20; H, 6.50. Found: C, 81.02; H, 6.70.
1-[2-(2-(2-(Tr itylp h en oxy)eth oxy)eth oxy)eth oxy]-4-h y-
d r oxyben zen e (12). A solution of 11 (1.55 g, 2.38 mmol) in
CH2Cl2 (125 mL) was added to a suspension of Pd/C (5%, 0.31
g) in MeOH (125 mL). H2 gas was bubbled through the
mixture with continuous stirring for 15 h. The solution was
filtered through Celite. The solvent was removed in vacuo to
yield 12 as a white solid (1.24 g, 95%). This product was
unstable, and so the next reaction was carried out immediately
using the crude product.
1-[2-(2-(2-(Tr itylp h en oxy)eth oxy)eth oxy)eth oxy]-4-[2-
(2-(2-h yd r oxyeth oxy)eth oxy)eth oxy]ben zen e19 (13).
A
stirred suspension of 12 (1.24 g, 2.21 mmol) and K2CO3 (4.36
g, 31.5 mmol) in MeCN (40 mL) was brought to reflux under
nitrogen with continuous stirring. 2-(2-(2-Chloroethoxy)-
ethoxy)ethanol (2.74 mL, 14.8 mmol) was added dropwise, and
the resulting mixture was heated under reflux under nitrogen
for 3 days. The solution was cooled and filtered, and the
solvent was removed in vacuo. CH2Cl2 (200 mL) was added
to the residue, and the resultant mixture was washed with
dilute HCl (pH 3, 2 × 250 mL) and then distilled H2O (2 ×
250 mL). The organic phase was dried (MgSO4) and the
solvent removed in vacuo to yield a yellow oil. Column
chromatography [SiO2, CH2Cl2:MeOH (98.5:1.5)] gave 13 as a
yellow oil, which was crystallized from hexane and washed
thoroughly with hexane:EtOAc (5:2) to yield the title compound
as a pale yellow solid (1.2 g, 69%): mp 49-50 °C; IR (NaCl)
3420, 3057, 3029, 2874, 2360, 2340, 1508, 1490, 1234, 1183,
1123, 1066, 939, 750, 702 cm-1; LSIMS m/z 692 (M+); 1H NMR
δ (CDCl3, 300 MHz, 25 °C) δ 3.61-3.67 (m, 6H), 3.70-3.76
(m, 6H), 3.82-3.88 (m, 6H), 4.06-4.12 (m, 6H), 6.77-6.8
1-[2-(2-(2-(p-Tolu en esu lfon yloxy)eth oxy)eth oxy)eth oxy]-
4-(ben zyloxy)ben zen e (9). A solution of the alcohol 8 (3 g,
9.2 mmol), Et3N (3.78 mL, 37.4 mmol), and a catalytic amount

3074 J . Org. Chem., Vol. 62, No. 10, 1997
Amabilino et al.
(AA′BB′ system, 2H, J ) 8 Hz), 6.83 (s, 4H), 7.07-7.10 (AA′BB′
system, 2H, J ) 8 Hz), 7.18-7.26 (m, 15H); 13C NMR (CDCl3,
75.5 MHz) δ 42.7, 61.8, 64.3, 67.3, 68.2, 69.8, 69.9, 69.9, 70.4,
70.8, 70.9, 72.5, 113.4, 115.6, 125.9, 127.4, 131.1, 132.2, 139.2,
147.1, 153.1. Anal. Calcd for C43H48O8: C, 74.54; H, 6.98.
Found: C, 74.56; H, 6.94.
IR (NaCl) 3062, 3032, 2924, 2872, 1593, 1507, 1454, 1289,
1228, 1124, 924, 826, 741, 697 cm-1; LSIMS m/z 738 (M+); 1H
NMR (CDCl3, 300 MHz, 25 °C) δ 3.73 (s, 8H), 3.84-3.80 (m,
8H), 4.09-4.04 (m, 8H), 4.98 (s, 4H), 6.51-6.49 (m, 3H), 6.86-
6.84 (m, 8H), 7.13 (t, 1H, J ) 7 Hz)), 7.42-7.24 (m, 10H); 13
C
NMR (CDCl3, 75 MHz) δ 61.8, 67.4, 68.1, 69.8, 69.9, 70.7, 70.9,
102.4, 106.9, 107.2, 108.1, 115.7, 115.9, 127.5, 127.9, 128.6,
130.0, 137.3, 153.2; HRMS calcd for C44H50O10 [M]+ 738.3440,
found 738.3411 (err -1.0).
1,3-Bis[2-(2-(2-(4-h yd r oxyp h e n oxy)e t h oxy)e t h oxy)-
eth oxy]ben zen e (17). A solution of compound 16 (0.580 g,
0.78 mmol) in CHCl3 (100 mL) was added to a suspension of
Pd/C (5%, 1 g) in MeOH (100 mL). The resulting suspension
was stirred at rt for 10 h as H2 gas was bubbled into the
mixture. The suspension was then filtered through Celite and
the solvent removed in vacuo to give the bisphenol 17 as a
white solid (0.42 g, 95%). Since compound 17 is unstable, the
next reaction was carried out immediately using the crude
product.
1-[2-(2-(2-(p-Tolu en esu lfon yloxy)eth oxy)eth oxy)eth oxy]-
4-[2-(2-(2-(t r i t y lp h e n o x y )e t h o x y )e t h o x y )e t h o x y ]-
ben zen e (14). A stirred solution of the vacuum-dried 13 (0.4
g, 0.5 mmol), Et3N (0.8 mL, 8 mmol), and a catalytic amount
of DMAP in dry CH2Cl2 (20 mL) was cooled to 0 °C under a
nitrogen atmosphere. A solution of p-toluenesulfonyl chloride
(0.14 g, 0.55 mmol) in dry CH2Cl2 (10 mL) was added dropwise
over 30 min. The resultant mixture was left stirring at 0 °C
for 2 h. The solution was warmed up to room temperature
and then filtered, and the solvent was removed in vacuo to
give a yellow oil. This oil was dissolved in CH2Cl2 (100 mL)
and washed with dilute HCl (pH 3, 2 × 100 mL) and distilled
H2O (2 × 100 mL). The organic phase was dried (MgSO4) and
the solvent removed in vacuo to yield a pale yellow oil. Column
chromatography [SiO2, CH2Cl2:MeOH (99:1)] afforded 14 as a
yellow oil (0.1 g, 41%): IR (NaCl) 3055, 2923, 1598, 1508, 1453,
1356, 1232, 1176, 1124, 1010, 924, 816, 704 cm-1; LSIMS m/ z
846 (M+); 1H NMR (CDCl3, 300 MHz, 25 °C) δ 2.41 (s, 3H),
3.59-3.81 (m, 18H), 4.02-4.17 (m, 8H), 6.76-6.79 (AA′BB′
system, 2H, J ) 8 Hz), 6.81-6.83 (m, 4H), 7.07-7.10 (AA′BB′
system, 2H, J ) 8 Hz), 7.13-7.25 (m, 15H), 7.29-7.31 (AA′BB′
system, 2H, J ) 6 Hz), 7.58-7.61 (AA′BB′ system, 2H, J ) 6
Hz); 13C NMR (CDCl3, 75 MHz) δ 21.6, 42.8, 61.8, 64.3, 67.3,
68.1, 68.8, 69.9, 70.4, 70.8, 70.8, 70.9, 71.4, 72.5, 113.4, 115.7,
125.9, 127.4, 128.0, 129.7, 129.8, 131.1, 132.2, 133.1, 139.2,
1,3-B i s {2-(2-(2-[4-t r i t y lp h e n o x y )e t h o x y )e t h o x y )-
eth oxy]p h en oxy]eth oxy)eth oxy)eth oxy}ben zen e (18). A
solution of the biphenol 17 (0.41 g, 0.73 mmol), K2CO3 (1 g,
7.2 mmol), and a catalytic amount of LiBr in dry MeCN (70
mL) was refluxed for 1 h under nitrogen. A solution of tosylate
4 (1.14 g, 1.84 mmol) in dry MeCN (100 mL) was added
dropwise over 30 min to the reaction mixture; the solution was
heated under reflux for 5 days in a nitrogen atmosphere with
vigorous stirring. The solution was then allowed to cool down
to rt before it was filtered and the solvent removed in vacuo.
The residual oil was dissolved in CH2Cl2 (200 mL) before being
washed with dilute HCl (pH 3, 2 × 200 mL) and brine (2 ×
200 mL). The organic phase was dried (MgSO4) and the
solvent removed in vacuo. Column chromatography [SiO2,
CH2Cl2:MeOH (98:2)] afforded the dumbbell compound 18 as
a brown oil (1.07 g, 71%): IR (NaCl) 3054, 3030, 2874, 1597,
1510, 1452, 1240, 1183, 1136, 949, 827, 740, 700 cm-1; LSIMS
144.8, 147.1, 153.1, 153.2, 156.8. Anal. Calcd for C50H54
-
O10S: C, 70.90; H, 6.43; S, 3.78. Found: C, 71.02; H, 6.21; S,
3.90.
1 -{p -[2 -(2 -(2 -(4 -T r i t y l p h e n o x y )e t h o x y )e t h o x y )-
e t h o x y ]p h e n o x y }-10-{m -[2-(2-(2-(4-t r i t y lp h e n o x y )-
eth oxy)eth oxy)eth oxy]p h en oxy}-3,6-d ioxa octa n e (15). A
solution of phenol 6 (0.58 g, 1.04 mmol), K2CO3 (1g, 7.2 mmol),
and a catalytic amount of LiBr in dry MeCN (100 mL) was
heated under reflux over 1 h under a nitrogen atmosphere. A
solution of tosylate 14 (0.88 g, 1.04 mmol) in dry MeCN (70
mL) was added dropwise over 30 min to the previous solution.
The resulting mixture was heated under reflux for 5 days
under nitrogen with vigorous stirring. The solution was cooled
down to rt and then filtered, and the solvent was removed in
vacuo. The residual oil was then dissolved in CH2Cl2 (200 mL)
and washed with dilute HCl (pH 3, 2 × 200 mL) and brine
(2 × 200 mL). The organic phase was dried (MgSO4) and the
solvent removed in vacuo to give a brown oil. Column
chromatography [SiO2, CH2Cl2:MeOH (99:1)] yielded dumbbell
compound 15 as a brown oil (0.91 g, 71%): IR (NaCl) 3054,
3029, 2922, 2873, 1606, 1508, 1492, 1448, 1230, 1185, 1128,
1065, 948, 827, 748, 703 cm-1; LSIMS m/z 1234 (M+); 1H NMR
(CDCl3, 300 MHz, 25 °C) δ 3.76 (s, 12H), 3.87-3.86 (m, 12H),
4.12-4.09 (m, 12H), 6.54-6.52 (m, 2H), 6.83-6.80 (AA′BB′
system, 4H, J ) 8 Hz), 6.86-6.85 (m, 4H), 7.14-7.11 (AA′BB′
system, 4H, J ) 8 Hz), 7.29-7.18 (m, 32 H); 13C NMR (CDCl3,
75 MHz) δ 30.2, 64.1, 67.1, 67.2, 67.9, 69.6, 69.8, 70.7, 71.1,
72.3, 101.6, 106.9, 113.2, 115.4, 125.7, 127.3, 128.4, 129.7,
131.0, 132.0, 139.0, 146.9, 152.9, 153.4, 156.6, 159.8; HRMS
calcd for C80H82O12 [M]+ 1234.5806, found 1234.5831 (err -2.0).
1 , 3 - B i s [ 2 - ( 2 - ( 2 - ( 4 - ( ( b e n z y l o x y ) p h e n o x y ) -
eth oxy)eth oxy)eth oxy]ben zen e (16). A solution of resor-
cinol (0.24 g, 2.2 mmol), K2CO3 (1.5 g, 10.8 mmol), and a
catalytic amount of LiBr in dry MeCN (50 mL) was brought
to reflux for 1 h in a nitrogen atmosphere. A solution of
tosylate 9 (2.12 g, 4.4 mmol) in dry MeCN (150 mL) was added
dropwise over 30 min to the reaction mixture; the solution was
refluxed under nitrogen for 5 days with vigorous stirring. The
solution was cooled to rt and filtered, and the solvent was
removed in vacuo. The residual oil was dissolved in CH2Cl2
(200 mL) and washed with dilute HCl (pH 3, 2 × 200 mL) and
brine (2 × 200 mL). The organic phase was dried (MgSO4)
and the solvent removed in vacuo. Column chromatography
[SiO2, EtOAc:hexane (40:60) and then CH2Cl2:MeOH (98:2)]
yielded diprotected bisphenol 16 as a yellow oil (2.0 g, 62%):
1
m/z 1460 (M + H)+; H NMR (CDCl3, 300 MHz, 25 °C) δ 3.72
(s, 16H), 3.89-3.85 (m, 16H), 4.14-4.08 (m, 16H), 6.55-6.52
(m, 3H), 6.83-6.80 (AA′BB′ system, 4H, J ) 8 Hz), 6.86-6.85
(m, 8H), 7.14-7.11 (AA′BB′ system, 4H, J ) 8 Hz), 7.29-7.19
(m, 31H); 13C NMR (CDCl3, 75 MHz) δ 53.5, 61.8, 64.3, 67.3,
67.4, 68.1, 69.8, 69.9, 70.9, 72.5, 101.8, 107.1, 113.4, 115.6,
123.4, 125.9, 127.5, 128.6, 129.9, 131.1, 132.2, 139.2, 147.1,
153.1, 156.7, 160.0. Anal. Calcd for C92H98O16: C, 75.68; H,
6.77. Found: C, 75.62; H, 6.87.
1,4-Bis{2-(2-(2-[3-[2-(2-(2-(4-t r it ylp h e n oxy)e t h oxy)-
e t h o x y )e t h o x y ]p h e n o x y ]e t h o x y )e t h o x y )e t h o x y }-
ben zen e (20). A solution of the phenol 6 (4.29 g, 7.6 mmol),
K2CO3 (3 g, 21 mmol), and a catalytic amount of LiBr in dry
MeCN (150 mL) was heated under reflux for 1 h in a nitrogen
atmosphere. A solution of the bistosylate 19 (2.61 g, 3.8 mmol)
in dry MeCN (150 mL) was added dropwise over 30 min to
the reaction mixture; the solution was refluxed under nitrogen
for 7 days with vigorous stirring. The solution was then
allowed to cool down to rt before it was filtered and the solvent
removed in vacuo. The residual oil was dissolved in CH2Cl2
and washed with dilute HCl (pH 3, 2 × 200 mL) and then brine
(2 × 200 mL). The organic phase was dried (MgSO4) and the
solvent removed in vacuo. Column chromatography [(SiO2,
CH2Cl2:MeOH (99:1) and then CH2Cl2:MeOH (98:2)] afforded
the dumbbell compound 20 as a brown oil (3.33 g, 60%): IR
(NaCl) 3054, 3029, 2923, 2873, 1594, 1507, 1492, 1448, 1233,
1185, 1126, 946, 827, 748, 703 cm-1; LSIMS m/z 1460 (M +
H)+; 1H NMR (CDCl3, 300 MHz, 25 °C) δ 3.72 (s, 16H), 3.89-
3.84 (m, 16H), 4.14-4.07 (m, 16H), 6.53-6.51 (m, 6H), 6.83-
6.80 (AA′BB′ system, 4H, J ) 8 Hz), 6.86-6.85 (m, 4H), 7.13-
7.10 (AA′BB′ system, 4H, J ) 8 Hz), 7.29-7.19 (m, 32H); 13C
NMR (CDCl3, 75 MHz) δ 30.4, 42.8, 64.4, 67.3, 67.5, 68.1, 69.8,
70.0, 70.1, 70.1, 71.3, 71.4, 101.9, 107.2, 113.4, 115.7, 125.9,
127.5, 129.9, 131.2, 132.2, 139.2, 147.1, 153.2, 156.8, 160.0.
Anal. Calcd for C92H98O16: C, 75.68; H, 6.77. Found: C, 75.67;
H, 6.68.
{[2]-[1-{p -[2-(2-(2-(4-Tr it ylp h e n oxy)e t h oxy)e t h oxy)-
eth oxy]p h en oxy}-10-{m -[2-(2-(2-(4-tr itylp h en oxy)eth oxy-
)et h oxy)et h oxy]p h en oxy}-3,6-d ioxa oct a n e][9,18,29,38-
t et r a a zon ia [1.1.0.1.1.0]p a r a cyclop h a n e]r ot a xa n e} Tet -
r a k is(h exa flu or op h osp h a te) (23‚4P F 6). A solution of the

Translational Isomerism in [2]Rotaxanes
J . Org. Chem., Vol. 62, No. 10, 1997 3075
dumbbell compound 15 (0.503 g, 0.4 mmol), the bipyridinium
salt 21‚2PF6 (0.086 g, 1.2 mmol), and the dibromide 22 (0.38
g, 1.4 mmol) in dry DMF (10 mL) was stirred for 10 days at
room temperature and pressure. Thereafter, Et2O (50 mL)
was added to the reaction mixture in order to precipitate all
the charged species. The orange precipitate was filtered and
washed with Et2O (50 mL) and CH2Cl2 (50 mL). Column
chromatography [SiO2, MeOH:NH4Cl (2 M):MeNO2 (7:2:1)]
afforded the rotaxane 23‚4PF6 as a red solid in the form of
the chloride salt. The red solid was dissolved in H2O, and a
saturated aqueous solution of NH4PF6 was added dropwise
until no further precipitation was observed. The red precipi-
tate was filtered off and washed thoroughly with H2O to yield
rotaxane 23‚4PF6 as a red powder (100 mg, 11%) after vacuum
drying: mp > 250 °C dec; IR (NaCl) 3055, 2921, 2360, 1636,
1594, 1508, 1452, 1247, 1183, 1151, 841, 699 cm-1; UV/vis λmax
(ꢀ) 252 nm (37500), 463 nm (328); LSIMS m/z 2336 (M+), 2191
approximately 52H), 6.00 (s, 8H), 6.82 (bm, approximately 4H),
7.02 (bm, approximately 2H), 7.28-7.16 (m, 34H), 8.02 (s, 8H),
8.21-8.19 (d, 8H, J ) 6 Hz), 9.34-9.32 (d, 8H, J ) 6 Hz);
12
HRMS calcd for
C
13C1H130F18N4O16P3 [M - PF6]+ 2414.8440,
127
found 2414.8352 (err 3.7).
{[2]-[1,4-B is {2-(2-(2-[3-[2-(2-(2-(4-t r it y lp h e n o x y )-
e t h o x y )e t h o x y )e t h o x y ]p h e n o x y ]e t h o x y )e t h o x y )-
e t h o x y }p h e n y l][9,18,29,38-t e t r a a zo n ia [1.1.0.1.1.0]-
p a r a cyclop h a n e]r ot a xa n e} Tet r a k is(h exa flu or op h os-
p h a te) (25‚4P F 6). A solution of the dumbbell compound 20
(0.83 g, 0.5 mmol), the bipyridinium salt 21‚2PF6 (1.2 g, 1.7
mmol), and the dibromide 22 (0.18 mg, 0.6 mmol) in dry DMF
(10 mL) was stirred for 10 days at room temperature and
pressure. Thereafter, Et2O (50 mL) was added to the reaction
mixture in order to precipitate all the charged species. The
orange precipitate was filtered and washed with Et2O (50 mL)
and CH2Cl2 (50 mL). Column chromatography [SiO2, MeOH:
NH4Cl (2 M):MeNO2 (7:2:1)] afforded the rotaxane 25‚4PF6 as
a red solid in the form of the chloride salt. The red solid was
dissolved in H2O, and a saturated aqueous solution of NH4PF6
was added dropwise until no further precipitation was ob-
served. The red precipitate was filtered and washed thor-
oughly with H2O to yield the rotaxane 25‚4PF6 as a red powder
(0.20 g, 14%) after vacuum drying: mp > 250 °C dec; IR (NaCl)
1
(M - PF6)+, 2046 (M - 2PF6)+, 1900 (M - 3PF6)+; H NMR
(CD3COCD3, 300 MHz, 25 °C) δ 4.15-3.64 (m, 40H), 5.99 (s,
8H), 6.81-6.49 (bm, approximately 3H,), 6.99-6.96 (AA′BB′
system, 4H, J ) 8 Hz), 7.07-7.04 (AA′BB′ system, 4H, J ) 8
Hz), 7.26-7.19 (m, 31H), 8.02 (s, 8H), 8.19-8.17 (d, 8H, J )
6 Hz), 9.31-9.29 (d, 8H, J ) 6 Hz); HRMS calcd for
C116H114F18N4P3O12 [M - PF6]+ 2189.7359, found 2189.7323
(err 1.7).
3056, 2922, 2360, 1635, 1507, 1411, 1134, 836, 790, 702 cm-1
;
{[2]-[1,3-B is {2-(2-(2-[4-[2-(2-(2-(4-t r it y lp h e n o x y )-
e t h o x y )e t h o x y )e t h o x y ]p h e n o x y ]e t h o x y )e t h o x y )-
e t h o x y }p h e n y l][9,18,29,38-t e t r a a zo n ia [1.1.0.1.1.0]-
p a r a cyclop h a n e]r ot a xa n e} Tet r a k is(h exa flu or op h os-
p h a te) (24‚4P F 6). A solution of the dumbbell compound 18
(0.50 mg, 0.4 mmol), the bipyridinium salt 21‚2PF6 (0.086 g,
1.2 mmol), and the dibromide 22 (0.38 g, 1.4 mmol) in dry DMF
(10 mL) was stirred for 10 days at room temperature and
pressure. Thereafter, Et2O (50 mL) was added to the reaction
mixture in order to precipitate all the charged species. The
orange precipitate was filtered and washed with Et2O (50 mL)
and CH2Cl2 (50 mL). Column chromatography [SiO2, MeOH:
NH4Cl (2 M):MeNO2 (7:2:1)] afforded the rotaxane 24‚4PF6 as
a red solid in the form of the chloride salt. The red solid was
dissolved in H2O, and a saturated aqueous solution of NH4PF6
was added dropwise until no further precipitation was ob-
served. The red precipitate was filtered off and washed
thoroughly with H2O to yield rotaxane 24‚4PF6 as a red powder
(0.11 g, 12%) after vacuum drying: mp > 250 °C dec; IR (NaCl)
UV/vis λmax (ꢀ) 242 nm (38 100), 442 nm (315); LSIMS m/z 2415
1
(M - PF6)+, 2270 (M - 2PF6)+, 2125 (M - 3PF6)+; H NMR
(CD3COCD3, 300 MHz, 25 °C) δ 4.10-3.64 (m, 52H), 5.99 (s,
8H), 6.82 (bs, approximately 6H), 7.07-7.04 (AA′BB′, system,
4H, J ) 8 Hz), 7.29-7.15 (m, 34H), 8.02 (s, 8H), 8.24-8.21 (d,
8H, J ) 6 Hz), 9.33-9.31 (d, 8H, J ) 6 Hz); HRMS calcd for
12
C
13C1H130F18N4O16P3 [M - PF6]+ 2414.8440, found 2414.8486
127
(err -1.9).
Ack n ow led gm en t. We thank the Engineering and
Physical Science Research Council for grants to pur-
chase mass spectrometry equipment and for a postdoc-
toral fellowship (to S.E.B.) and Eusko J aurlaritza,
Unibersitate, Ikerketa eta Hizkuntza Saila, for a pre-
doctoral grant (to M.G.-L.).
Su p p or tin g In for m a tion Ava ila ble: Copies of NMR
spectra (8 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
3054, 2921, 1636, 1508, 1452, 1248, 1136, 1056, 842, 702 cm-1
;
UV/vis λmax (ꢀ) 244 nm (38700), 445 nm (320); LSIMS m/z 2560
(M+), 2415 (M - PF6)+, 2270 (M - 2PF6)+, 2125 (M - 3PF6)+;
1H NMR (CD3COCD3, 300 MHz, 25 °C) δ 4.07-3.65 (bm,
J O9612584