Molecular meccano, 51. - Diastereoselective self-assembly of [2]catenanes

Article abstract of DOI:10.1002/(SICI)1099-0690(199905)1999:5<995::AID-EJOC995>3.0.CO;2-K

Two chiral π-electron-rich crown ethers incorporating either a binaphthol or two D-mannitol units have been synthesized and their abilities to bind bipyridinium guests demonstrated. Both crown ethers could be interlocked mechanically with cyclobis(paraqua

Full text of DOI:10.1002/(SICI)1099-0690(199905)1999:5<995::AID-EJOC995>3.0.CO;2-K

FULL PAPER
Molecular Meccano, 51[°]
Diastereoselective Self-Assembly of [2]Catenanes
Peter R. Ashton,[a] Aaron M. Heiss,[a][°°] Dario Pasini,[a] Francisco M. Raymo,[a][°°]
¸
Andrew N. Shipway,[a] J. Fraser Stoddart,*[a][°°] and Neil Spencer[a]
Keywords: Catenanes / Diastereoselectivity / Molecular Recognition / Self-Assembly / Template-Directed Synthesis
Two chiral π-electron-rich crown ethers incorporating either
a binaphthol or two -mannitol units have been synthesized
and their abilities to bind bipyridinium guests demonstrated.
Both crown ethers could be interlocked mechanically with
modest diastereoselection (56:44–67:33) occurs during the
kinetically controlled self-assembly of the catenanes. The
free energy barriers (12.8–16.8 kcal mol–1) associated with
the circumrotation of one macrocyclic component through
D
cyclobis(paraquat-p-phenylene) to afford two chiral the cavity of the other and vice versa were determined by
[2]catenanes. Furthermore, these crown ethers were also
mechanically interlocked with a tetracationic cyclophane
variable-temperature 1H-NMR spectroscopy. In addition,
another dynamic process involving the “rocking” of the
incorporating
a 2,2Ј-dihydroxy-1,1Ј-binaphthyl spacer to mean planes of the mechanically interlocked macrocycles
afford mixtures of diastereoisomeric [2]catenanes. The
composition of these mixtures was determined by 1H-NMR-
with respect to each other was also identified and the
associated free energy barriers (10.3–10.4 kcal mol–1
)
spectroscopic and HPLC analyses which revealed that determined.
complexes. Here, we report the syntheses of (i) two chiral π-
electron-rich crown ethers incorporating either an element
of axial chirality or chiral centers, (ii) two chiral [2]ca-
tenanes, each incorporating one or other, of the chiral
crown ethers and an achiral tetracationic cyclophane, (iii)
the mechanical interlocking of the chiral crown ethers with
a chiral tetracationic cyclophane to afford diastereoisomeric
mixtures of chiral [2]catenanes, and (iv) the investigation of
the dynamic processes associated with the relative move-
ments of the ring components within these [2]catenanes in
solution.
Introduction
Catenanes[1] incorporating complementary π-electron-
rich and π-electron-deficient macrocyclic components self-
assemble[2] under kinetic control from appropriate precur-
sors. In this process, intermediate complexes self-assemble
under the guidance of [CϪH···O] hydrogen bonds, [π···π]
stacking, and [CϪH···π] interactions after the formation of
one covalent bond. The subsequent formation of a second
covalent bond interlocks mechanically the components,
converting the supramolecular complex into a molecular
compound Ϫ namely, a catenane. Competition experiments
have demonstrated[3] that the relative rates of formation of
the second covalent bond “select” the components which
will be integral parts of the interlocked molecules in the
final product. In order to gain some further insight into
the mechanisms of these self-assembly processes, we have
investigated the formation of diastereoisomeric [2]ca-
tenanes,[4] starting from racemic mixtures of one compo-
nent, or its precursors, and the pure enantiomer of the other
component. Diastereoselection should occur if the rates of
covalent bond formation are influenced by the different
stereochemistries of the intermediate diastereoisomeric
Results and Discussion
Synthesis
Reaction of 1 with (RS)-2 under high-dilution conditions
gave (Scheme 1) (RS)-3 in an overall yield of 21%. The en-
antiomerically pure (R)-3 was obtained by allowing 1 to
react with (R)-2 under otherwise identical conditions. High-
performance liquid-chromatographic (HPLC) analysis of
(R)-3 revealed an enantiomeric purity higher than 98%.
Upon mixing (Scheme 2) (RS)-3 with 4·2PF6 in MeCN, an
orange color appears, indicating complex formation. Spec-
trophotometric titrations revealed an association constant
(Ka) of 23 Ϫ1 at 25°C, corresponding to a free energy of
association (∆G°) of Ϫ1.9 kcal molϪ1. Reaction of 5·2PF6
and 6 in the presence of (RS)-3 gave (Scheme 3) (RS)-
7·4PF6 in an overall yield of 20%, after counterion ex-
change.
[a]
School of Chemistry, University of Birmingham,
Edgbaston, Birmingham B15 2TT, UK
[°]
Part 50: P. R. Ashton, S. E. Boyd, A. Brindle, S. J. Langford,
´
´
S. Menzer, L. Perez-Garcıa, J. A. Preece, F. M. Raymo, N.
Spencer, J. F. Stoddart, A. J. P. White, D. J. Williams, New J.
Chem., in press.
Current address: Department of Chemistry and Biochemistry,
University of California, Los Angeles,
405 Hilgard Avenue, Los Angeles, California, 90095-1569,
USA
Fax: (internat.) ϩ1-310/206-1843
E-mail: stoddart@chem.ucla.edu
[°°]
Alkylation (Scheme 4) of ()-8 with 9, followed by the
removal of the tetrahydropyranyl protecting group, afforded
()-10 in a yield of 57%. Tosylation of ()-10 gave ()-11,
which was allowed to react with 4-benzyloxyphenol, before
Eur. J. Org. Chem. 1999, 995Ϫ1004
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J. F. Stoddart et al.
FULL PAPER
Scheme 1. Synthesis of the crown ethers (R)-3 and (S)-3
Scheme 2. Complexation of 4·2PF6 by (R)-3 and (S)-3
being subjected to hydrogenolysis. The resulting diol ()-12 tures of the crown ether 3 and of the dibromide 16, all four
was treated with ()-11 to yield the crown ether ()-13 in isomers self-assemble and no diastereoselectivity is ob-
a yield of 14%. Upon mixing the π-electron-rich crown served. However, (R/R)-15·4PF6 can be obtained exclusively
ether ()-13 and the π-electron-deficient guest 4·2PF6 in when (R)-3 and (R)-16 are used (Entry 2 in Table 1) under
MeCN, an orange color appears spontaneously indicating similar conditions. When route B is employed (Entry 3 in
the formation of a complex. Spectrophotometric titrations Table 1) using (R)-3 and a racemic mixture of the salt
revealed an association constant (Ka) of 41 Ϫ1 at 25°C, 17·4PF6, (R/R)-15·4PF6 and (R/S)-15·4PF6 are obtained in
corresponding to a free energy of association (∆G°) of Ϫ2.2 an overall yield of 33% and with a diastereoisomeric ratio
kcal molϪ1. Reaction of 5·2PF6 and 6 in the presence of of ca. 54:46 in favor of (R/R)-15·4PF6. When similar con-
()-13 afforded (Scheme 5) the [2]catenane ()-14·4PF6 ditions are employed (Entry 4 in Table 1) using a racemic
in a yield of 17%, after counterion exchange.
mixure of the crown ether 3 and (R)-17·4PF6, (R/R)-
Two pairs of enantiomers are associated (Figure 1) with 15·4PF6 and (R/S)-15·4PF6 are obtained in an overall yield
the [2]catenane 15·4PF6. The diastereoisomers can be dis- of 23% and with a diastereoisomeric ratio of ca. 66:34 in
1
tinguished by H-NMR spectroscopy and by HPLC while favor of (R/R)-15·4PF6.
1
the enantiomers, of course, have identical H-NMR spectra
Mixtures of the diastereoisomeric [2]catenanes (R/)-
and retention times. The diastereoisomeric ratios for mix- 18·4PF6 and (S/)-18·4PF6 (Figure 3) were obtained fol-
tures of these isomers, obtained following routes A and B lowing routes A and B under the conditions listed in Table
(Scheme 6) under the conditions listed in Table 1, could be 2. When route A was employed (Entry 1 in Table 2) using
determined by 1H-NMR spectroscopy and HPLC. When ()-13 and a racemic mixture of the dibromide 16, (R/)-
route A is employed (Entry 1 in Table 1) using racemic mix- 18·4PF6 and (S/)-18·4PF6 were obtained in an overall
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Molecular Meccano, 51
FULL PAPER
Scheme 3. Template-directed synthesis of the [2]catenanes (R)-7·4PF6 and (S)-7·4PF6
Scheme 4. Synthesis of the crown ether ()-13
Scheme 5. Template-directed synthesis of the [2]catenane ()-14·4PF6
yield of 25% with a diastereoisomeric ratio of 57:43 in favor employed (Entry 3 in Table 2), using ()-13 and a racemic
of (R/)-18·4PF6. By employing ()-13 and (R)-16 under mixture of the salt 17·2PF6, (R/)-18·4PF6 and (S/)-
similar conditions (Entry 2 in Table 2), (R/)-18·4PF6 was 18·4PF6 were obtained in an overall yield of 28% with a
obtained exclusively in a yield of 27%. When route B was diastereoisomeric ratio of 58:42 in favor of (R/)-18·4PF6.
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J. F. Stoddart et al.
Table 1. Reaction conditions[a] and diastereoselectivities observed for the kinetically controlled self-assembly of the [2]catenane 15·4PF6
FULL PAPER
Entry
Reagents
Reagents
ratio
Time
[d]
Yield[b]
(%)
Diastereoselectivity
1H NMR
HPLC
1
2
3
4
(RS)-3
5·2PF6
(RS)-16
(R)-3
1
14
14
14
4
16
21
33
23
50:50[c]
Ϫ
48:52[c]
1
1.2
2
Ϫ
7·2PF6
(R)-16
(R)-3
1
1.2
2
56:44[c]
67:33[d]
54:46[c]
66:34[d]
6
1.2
1
(RS)-17·2PF6
(RS)-3
6
1
6
(R)-17·2PF6
7.2
[a]
[b]
[c]
All reactions were carried out in MeCN. Ϫ Overall yield determined after column chromatography and counterion exchange. Ϫ
[d]
Ratio between (R/R)-15·4PF6 and (R/S)-15·4PF6. Ϫ Ratio between (R/R)-15·4PF6 and (S/R)-15·4PF6.
1,4-dioxybenzene unit with respect to the mean plane of the
tetracationic cyclophane in which it is inserted.
In (RS)-7·4PF6, process I cannot occur since the binaph-
thol unit is too large to pass through the cavity of the tetra-
cationic cyclophane. At ambient temperature, process II is
1
fast on the H-NMR timescale and the bipyridinium units
located inside and outside the cavity of the crown ether
component cannot be distinguished. On cooling
a
(CD3)2CO solution of (RS)-7·4PF6 down, process II be-
comes slow and the set of signals associated with the α-
bipyridinium protons separate into two sets. By employing
the approximate coalescence treatment,[5] a free energy bar-
rier of 12.8 kcal molϪ1 at a coalescence temperature of 260
K was determined (Table 3) for process II. On further cool-
ing, process III becomes slow and the two sets of signals
for the α-bipyridinium protons separate into four sets. in
addidtion, the 1,4-dioxybenzene protons Ha and Hb (Figure
3) can be distinguished since they resonate as two distinct
singlets at δ ϭ 2.18 and 5.80, respectively. Again, by em-
ploying the approximate coalescence treatment, a free en-
ergy barrier of 10.3 kcal molϪ1 at a coalescence temperature
of 217 K was determined (Table 3) for process III.
In ()-14·4PF6, process I is slow on the 1H-NMR times-
cale at ambient temperature in (CD3)2CO and the “inside”
and “outside” 1,4-dioxybenzene protons resonate at δ ϭ
3.30 and 6.30, respectively. Upon warming the solution,
broadening of the signals occurs as process I becomes fast.
Line-broadening analysis[6] revealed (Table 3) a free energy
barrier of 16.8 kcal molϪ1 at a temperature of 335 K for
process I. Upon cooling the solution down, processes II and
III become slow. As a result, the set of signals observed for
the α-bipyridinium protons separates into two sets and then
into four. By employing the approximate coalescence treat-
ment, free energy barriers of 12.8 and 10.4 kcal molϪ1 at
coalescence temperatures of 269 and 221 K, respectively,
were determined (Table 3) for processes II and III, respec-
tively.
Figure 1. The two pairs of enantiomers associated with the [2]cate-
nanes 15·4PF6
1H-NMR Spectroscopy
The dynamic processes IϪIII illustrated in Figure 3 are
associated with the [2]catenanes in solution. Process I in-
volves the circumrotation of the crown ether component
through the cavity of the tetracationic cyclophane. Process
II corresponds to the circumrotation of the tetracationic
In (R/R)-15·4PF6, process I cannot occur since the bi-
cyclophane through the cavity of the macrocyclic polyether. naphthol unit is too large to pass through the cavity of the
Process III involves the “rocking” of the [O···O] axis of one tetracationic cyclophane, cf. the case of 7·4PF6. At 323 K,
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Molecular Meccano, 51
FULL PAPER
Scheme 6. The routes A and B used to synthesize the [2]catenanes 15·4PF6 and 18·4PF6
Table 2. Reaction conditions[a] and diastereoselectivities observed
for the kinetically controlled self-assembly of the [2]catenane
18·4PF6
Entry Reagents
Reagents Yield[b] Diastereoselectivity[c]
ratio
(%)
1H NMR
1
2
3
5·2PF6
()-13
(RS)-16
5·2PF6
()-13
(R)-16
1
25
57:43
1.5
1
1
2
1.2
1.2
1.5
1
27
28
Ϫ
6
58:42
()-13
(RS)-17·2PF6
[a]
[b]
All reactions were carried out in MeCN for 14 d. Ϫ
Overall
yield determined after column chromatography and counterion ex-
change. Ϫ Ratio between (R/)-18·4PF6 and (S/)-18·4PF6.
[c]
Figure 3. The dynamic processes associated with the [2]catenanes
in solution
1
the H-NMR spectrum of a (CD3)2CO solution of (R/R)-
15·4PF6 shows (Figure 4) one set of signals for the α-bipyri-
dinium protons adjacent to the binaphthol spacer and one
Figure 2. The two diastereoisomers (R/)-18·4PF6 and (S/)-
18·4PF6
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J. F. Stoddart et al.
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Table 3. Kinetic parameters for the dynamic processes associated with the [2]catenanes (RS)-7·4PF6, ()-14·4PF6, and (R/)-18·4PF6
in (CD3)2CO
Compound
Probe protons
∆ν[a] [Hz]
k[b] [sϪ1
]
T[c] [K]
∆GՆ[d]·[kcal molϪ1] Process
(RS)-7·4PF6
()-14·4PF6
α-bipyridinium
40
89
260
217
335
269
221
294
12.8
10.3
16.8
12.8
10.4
14.6
II[e]
III[e]
I[f]
α-bipyridinium
117
26
260
82
“outside” [OC6H4O]
α-bipyridinium
101
103
116
224
229
258
II[e]
III[e]
I[e]
α-bipyridinium
(R/)-19·4PF6
mannitol H3 and H4
[a]
[b]
[c]
[d]
[e]
Error ± 1 Hz. Ϫ
Error ± 5 sϪ1. Ϫ Error ± 1 K. Ϫ
Error ± 0.2 kcal molϪ1. Ϫ The coalescence method was employed to
[f]
determine the kinetic parameters. Ϫ The exchange method was employed to determine the kinetic parameters.
1
Figure 4. Partial H-NMR spectrum of the [2]catenane (R/R)-15·4PF6 recorded in (CD3)2CO at 323 K
1
set of signals for α-bipyridinium protons close to the p- partial H-NMR spectrum of a mixture of (R/R)-15·4PF6
phenylene spacer. Similarly, one AB system (δ ϭ 6.06Ϫ6.30) and (R/S)-15·4PF6 is shown in Figure 6. The resonances
is observed for the [CH2Nϩ] protons adjacent to the bi- associated with the 1,4-dioxybenzene protons of the two
naphthol spacer and another (δ ϭ 5.84Ϫ6.04) is associated diastereoisomers appear as two distinct singlets at δ ϭ 4.87
to the [CH2Nϩ] protons close to the p-phenylene spacer. and 4.81.
The 1,4-dioxybenzene protons resonate as a singlet at δ ϭ
4.86. On cooling the solution down, processes II and III
1
become slow, giving rise to very complex H-NMR spectra
Conclusions
which we have not been able to assign fully.
In (R/)-18·4PF6, process I is slow on the H-NMR ti-
1
mescale at 253 K in (CD3)2CO. As a result, the H3 and H4
Complementary components, incorporating either ele-
protons of the mannitol units give rise (Figure 5) to two ments of axial chirality or chiral centers, were allowed to
sets of signals at δ ϭ 4.84 and 4.55 which coalesce into one react under competitive conditions. Their diastereoselective
on warming the solution up to 295 K. By employing the self-assembly into [2]catenanes occurs through the forma-
coalescence treatment, a free energy barrier of 14.6 kcal tion of intermediate diastereoisomeric complexes. The rela-
molϪ1 at a coalescence temperature of 294 K was deter- tive stereochemistries of the interlocked components of the
mined (Table 3) for process I. At low temperatures, pro- intermediate complexes govern the rates of ring closure
cesses II and III become slow, giving rise to very complex (Scheme 6) determining the outcome of the kinetically con-
1H-NMR spectra which we have not been able to assign trolled self-assembly processes and imposing diastereoselec-
fully.
tion. Variable-temperature 1H-NMR-spectroscopic analyses
The diastereoisomeric mixtures of the [2]catenanes of some of the [2]catenanes enabled the determination of
15·4PF6 and 18·4PF6 were analyzed by 1H-NMR spec- the free energy barriers associated with the dynamic pro-
troscopy in order to evaluate the diastereoisomeric ratios. cesses involving the circumrotation of one macrocyclic com-
1
Even although the H-NMR spectra are very complex, un- ponent through the cavity of the other and vice versa and
ique resonances for the diastereoisomers can be identified the “rocking” of the mean planes of the mechanically inter-
and their relative intensities measured. As an example, the locked macrocycles with respect to each other.
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Molecular Meccano, 51
FULL PAPER
1
Figure 5. Partial H-NMR spectrum of the [2]catenane (R/)-18·4PF6 recorded in (CD3)2CO at 253 K
(LSIMS) were obtained with the VG Zabspec operating at a resolu-
tion of 6000 and using voltage scanning with CsI as a reference. Ϫ
1H-Nuclear Magnetic Resonance (1H-NMR) spectra were recorded
either with a Bruker AC300 (300 MHz) spectrometer or with a
Bruker AMX400 (400 MHz) spectrometer using either the solvent
or TMS as internal standards. Ϫ 13C-Nuclear Magnetic Resonance
(13C-NMR) spectra were recorded with either a Bruker AC300
(75.5 MHz) spectrometer or a Bruker AMX400 (100.6 MHz) spec-
trometer using either the solvent or TMS as internal standards. All
chemical shifts are quoted in ppm on the δ scale. Ϫ Microanalyses
were performed by the University of Birmingham Microanalytical
Service and by the University of North London Microanalytical
Service.
Crown Ether 3: A solution of 1 (2.7 g, 3.5 mmol) in dry MeCN (50
mL) was added to a suspension of Cs2CO3 (11.5 g, 35 mmol) and
CsOTs (3 g, 9.8 mmol) in dry MeCN (400 mL). The mixture was
heated under reflux and (RS)-2 (1 g, 3.5 mmol) in dry MeCN (200
mL) was added dropwise over a period of 6 h. Heating under reflux
was continued for 3 d. The reaction mixture was filtered, the sol-
Figure 6. Partial 1H-NMR spectrum of a mixture of (R/S)-15·4PF6
of (R/R)-15·4PF6 recorded in (CD3)2CO at 323 K
Experimental Section
General Methods: Chemicals were purchased from Aldrich and
used as received. Solvents were dried according to procedures de- vent was removed under reduced pressure, and the residue par-
scribed in the literature.[7] The compounds 1,[8] 5·2PF6,[7] 15,[9] titioned between H2O (400 mL) and CHCl3 (400 mL). The aqueous
[9]
17·2PF6 were prepared according to procedures described in the
literature. Ϫ Thin-layer chromatography (TLC) was carried out
using aluminium sheets precoated with silica gel 60 F (Merck
5554). The plates were inspected by UV light and developed with
iodine vapor. Ϫ Column chromatography was carried out using
silica gel 60 F (Merck 9385, 230Ϫ400 mesh). Ϫ High-performance
liquid chromatography (HPLC) was performed using a Gilson 714
system fitted with a UV/Vis detector. Ϫ Melting points were deter-
mined with an Elecrothermal 9200 apparatus and are not cor-
layer was extracted with CHCl3 (3 ϫ 400 mL). The combined or-
ganic layers were washed with H2O (3 ϫ 300 mL) and dried
(MgSO4). The solvent was removed under reduced pressure and
the residue was purified by column chromatography (SiO2: hexane/
MeCO2Et, 50:50 and then 20:80, v/v) to afford (RS)-3 (520 mg,
1
21%) as a white glass. Ϫ LSIMS; m/z: 712 [M]ϩ. Ϫ H NMR (300
MHz, CDCl3, 25°C): δ ϭ 7.90 (2 H, d, J ϭ 7 Hz), 7.83 (2 H, d,
J ϭ 7 Hz), 7.40 (2 H, d, J ϭ 7 Hz), 7.31 (2 H, m), 7.19 (2 H, m),
7.15 (2 H, d, J ϭ 7 Hz), 6.81 (4 H, s), 4.05 (8 H, m), 3.78 (4 H,
rected. Ϫ UV/Vis spectra were recorded with a Perkin-Elmer m), 3.62 (4 H, m), 3.50 (4 H, m), 3.42 (4 H, m), 3.28 (4 H, m), 3.11
Lambda 2 using HPLC-quality solvents. Ϫ Electron-impact mass
(4 H, m). Ϫ 13C NMR (75.5 MHz, CDCl3, 25°C): δ ϭ 154.4, 153.2,
spectra (EIMS) were performed using a Kratos Profile spec- 134.1, 129.4, 129.3, 127.8, 126.2, 125.6, 123.6, 120.5, 116.0, 115.8,
trometer. Ϫ Liquid secondary-ion mass spectra (LSIMS) were ob-
tained from a VG Zabspec mass spectrometer, equipped with a 35-
keV cesium-ion gun. Samples were dissolved in either a 3-nitro-
70.9, 70.5, 70.4, 69.8, 69.7, 69.6, 68.5, 29.7. Ϫ C42H48O10 (712.84):
calcd. C 70.77, H 6.78; found C 70.49, H 6.75. Ϫ The enantiomer-
ically pure crown ether (R)-3 was obtained by employing enantiom-
benzyl alcohol or 2-nitrophenyl octyl ether matrix, previously co- erically pure (R)-2 instead of (RS)-2 under otherwise identical con-
ated onto a stainless steel probe tip. High-resolution mass spectra
ditions. Ϫ [α]20 ϭ ϩ34 (c ϭ 0.08 in CHCl3).
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[2]Catenane 7·4PF6: (RS)-3 (180 mg, 0.25 mmol), 5·2PF6 (176 mg,
CDCl3, 25°C): 144.9, 129.9, 128.0, 99.2, 80.7, 80.6, 71.2, 69.3, 68.1,
0.30 mmol), and 6 (66 mg, 0.26 mmol) in dry MeCN (30 mL) was 21.7. Ϫ C24H30O10S2 (542.43): calcd. C 53.12, H 5.57, S 11.82;
stirred for 10 d at ambient temp. The solvent was removed under
reduced pressure and the residue was purified by column chroma-
tography (SiO2: MeOH/2  aq. NH4Cl/MeNO2, 7:2:1, v/v/v). The
resulting solid was dissolved in H2O and a saturated aqueous solu-
tion of NH4PF6 was added until no further precipitation occurred.
The red precipitate was filtered and air-dried to afford (RS)-7·4PF6
(90 mg, 20%) as a red solid. Ϫ LSIMS; m/z: 1812 [M]ϩ, 1667 [M
Ϫ PF6]ϩ, 1522 [M Ϫ 2PF6]ϩ, 1377 [M Ϫ 3PF6]ϩ. Ϫ 1H NMR [400
MHz, (CD3)2CO, 25°C]: δ ϭ 9.31 (8 H, d, J ϭ 7 Hz), 8.18 (8 H,
d, J ϭ 7 Hz), 8.03 (8 H, s), 7.92 (2 H, d, J ϭ 7 Hz), 7.85 (2 H, d,
J ϭ 7 Hz), 7.35 (2 H, m), 7.24 (2 H, m), 7.07 (2 H, d, J ϭ 7 Hz),
6.03 (4 H, d, J ϭ 13 Hz), 5.93 (4 H, d, J ϭ 13 Hz), 4.20Ϫ3.15 (36
H, m). Ϫ 13C NMR [75.5 MHz, (CD3)2CO, 25°C]: δ ϭ 155.2,
151.1, 147.7, 147.6, 145.8, 137.7, 134.5, 131.8, 130.7, 128.8, 127.3,
126.8, 125.8, 125.1, 122.0, 118.2, 113.9, 71.7, 71.1, 70.7, 70.6, 70.4,
70.1, 69.1, 67.9, 65.7. Ϫ C78H80N4O10P4F24 (1813.31): calcd. C
51.66, H 4.45 N 3.09; found C 51.60, H 4.42, N 2.88.
found C 53.26, H 5.65, S 12.10.
2,5-Di-O-[2Ј-(p-hydroxyphenoxy)ethoxy]-1,4:3,6-dianhydro-D-
mannitol (D)-12: A solution of 4-benzyloxyphenol (8.9 g, 44.2
mmol) was added to a suspension of 3.7 g of NaH (93 mmol, 60%
in mineral oil) in dry DMF (300 mL). The reaction mixture was
heated at 80°C for 2 h and then a solution of ()-11 (8 g, 15 mmol)
in dry DMF (100 mL) was added under N2. The reaction mixture
was maintained at 90°C for 4 d and then H2O and 10% aqueous
H2SO4 were added. The solvent was removed under reduced press-
ure and the residue was partitioned between H2O (300 mL) and
CH2Cl2 (300 mL). The aqueous layer was extracted with CH2Cl2
(3 ϫ 400 mL). The combined organic layers were washed with an
aqueous solution of 1M NaOH (3 ϫ 400 mL), H2O (3 ϫ 300 mL),
and dried (MgSO4). The solvent was removed under reduced press-
ure and the residue was purified by column chromatography (SiO2:
hexane/MeCO2Et, 20:80 and then 50:50, v/v) to yield 2,5-di-O-[2Ј-
(p-benzyloxyphenoxy)ethoxy]-1,4:3,6-dianhydro--mannitol as
a
20
2,5-Di-O-2Ј-(hydroxyethoxy)-1,4:3,6-dianhydro-D-mannitol [(D)-10]:
white solid (4 g, 45%). Ϫ [α589
]
ϭ ϩ61 (c ϭ 0.07 in CHCl3). Ϫ
EIMS; m/z (%): 598 (65) [M]ϩ. Ϫ 1H NMR (300 MHz, CDCl3,
25°C): δ ϭ 7.45 (10 H, m), 6.95 (8 H, m), 5.02 (4 H, s), 4.61 (2 H,
m), 4.22Ϫ3.75 (14 H, m). Ϫ 13C NMR (75.5 MHz, CDCl3, 25°C):
δ ϭ 153.2, 153.0, 137.3, 128.6, 127.5, 116.1, 115.8, 115.6, 81.0, 80.6,
71.2, 70.6, 69.3, 68.2. Ϫ C36H38O8 (598.65): calcd. C 72.22, H 6.40;
found C 72.21, H 6.45. Ϫ A solution of 2,5-di-O-[2Ј-(p-benzyloxy-
phenoxy)ethoxy]-1,4:3,6-dianhydro--mannitol (4 g, 6.6 mmol) in
CHCl3/MeOH (9:1, v/v, 70 mL) was subjected to hydrogenolysis
for 8 h at ambient temp. in the presence of 10% palladium on char-
coal (0.5 g). The mixture was filtered and the solvent was removed
under reduced pressure to afford ()-12 (2.7 g, 98%) as a white
solid which was used in the following step without further purifi-
cation. Ϫ LSIMS; m/z: 441 [M ϩ Na]ϩ, 418 [M]ϩ. Ϫ 1H NMR
[300 MHz, (CD3)2CO, 25°C]: δ ϭ 7.85 (2 H, br. s), 6.88 (8 H, m),
4.62 (2 H, m), 4.15 (2 H, m), 4.04 (4 H, m), 3.95Ϫ3.6 (8 H, m). Ϫ
13C NMR [75.5 MHz, (CD3)2CO, 25°C]: δ ϭ 153.0, 152.1, 116.4,
116.3, 81.4, 81.3, 71.7, 69.4, 68.9.
A suspension of finely ground NaOH (6.6 g, 165 mmol) in DMSO
(100mL) was stirred mechanically for 15 min at 50°C. ()-8 (3 g,
21 mmol) was added to the mixture and stirring and heating were
maintained for 1 h. A solution of 9 (18.5 g, 62 mmol) in DMSO
(30 mL) was added and the resulting mixture was heated for 18 h
at 80°C with stirring. After cooling down to ambient temperature,
the solvent was removed under reduced pressure by trap-to-trap
distillation and the solid residue was treated with a 1:1 (v/v) mix-
ture of CHCl3/H2O (800 mL). The organic layer was washed with
H2O and dried (MgSO4). The solvent was removed under reduced
pressure and the residue was purified by column chromatography
(SiO2: EtOAc) to yield (Rf ϭ 0.20) 2,5-di-O-[2Ј-(tetrahydropy-
ranyloxy)ethoxy]-1,4:3,6-dianhydro--mannitol (5 g, 61%) as a yel-
1
low oil. Ϫ H NMR (300 MHz, CDCl3, 25°C): δ ϭ 4.65Ϫ4.58 (4
H, m), 4.17Ϫ3.95 (4 H, m), 3.90Ϫ3.40 (16 H, m), 1.85Ϫ1.35 (12
H, m). Ϫ 13C NMR (75.5 MHz, CDCl3, 25°C): δ ϭ 99.1, 98.8,
80.9, 80.5, 71.1, 70.0, 66.9, 66.7, 62.3, 62.1, 60.4, 30.6, 25.4, 19.6,
19.4. Ϫ Concentrated HCl (0.5 mL) was added to a solution
of 2,5-di-O-[2Ј-(tetrahydropyranyloxy)ethoxy]-1,4:3,6-dianhydro--
mannitol (4 g, 12.4 mmol) in MeOH (30 mL). The solution was
stirred for 3 h at ambient temp., after which time no traces of start-
ing material were present by TLC (SiO2: CHCl3/MeOH, 100:1, v/
v). The solution was filtered, concentrated and the residue was dis-
solved in CHCl3 and dried (K2CO3) to yield ()-10 (2.7 g, 93%) as
Crown Ether (DD)-13: A solution of ()-12 (500 mg, 1.20 mmol)
was added to a suspension of of NaH (155 mg, 3.90 mmol, 60%
suspension in mineral oil) and CsOTs (20 mg) in dry DMF (120
mL). The mixture was heated for 1 h at 80°C and a solution of
()-11 (650 mg, 1.20 mmol) in dry DMF (80 mL) was added drop-
wise over a period of 6 h under N2. The mixture was maintained
for 14 d at 90°C. After cooling down to ambient temp., H2O (50
mL) and aqueous 10% H2SO4 (20 mL) were added. The solvent
was removed under reduced pressure and the residue was par-
titioned between H2O (300 mL) and CHCl3 (300 mL). The aqueous
layer was extracted with CHCl3 (3 ϫ 400 mL). The combined or-
ganic layers were washed with H2O (3 ϫ 300 mL) and dried
(MgSO4). The solvent was removed under reduced pressure and
the residue was purified by column chromatography (SiO2, MeC-
O2Et and then CH2Cl2/MeOH, 95:5) to yield ()-13 (100 mg,
1
a colourless oil. Ϫ H NMR (300 MHz, CDCl3, 25°C): δ ϭ 4.58
(2 H, m), 4.08 (4 H, m), 3.72 (10 H, m), 3.15 (2 H, br. s). Ϫ 13C
NMR (75.5 MHz, CDCl3, 25°C): δ ϭ 80.7, 80.5, 72.5, 71.5, 61.9.
2,5-Di-O-[2Ј-(p-tolylsulfonyloxy)ethoxy]-1,4:3,6-dianhydro-
D-
mannitol ( )-11: A solution of NaOH (2 g, 50 mmol) in H2O (50
D
mL) was added to a solution of ()-10 (2.6 g, 11 mmol) in THF
(50 mL). The reaction mixture was cooled down to 0°C with stir-
ring and a solution of p-toluenesulfonyl chloride (5.1 g, 27 mmol)
in THF (80 mL) was added dropwise over a period of 1 h. The
reaction mixture was stirred for 3 h and then was poured into 400
mL of a 1:1 ice/water mixture. The aqueous layer was extracted
with CH2Cl2 (3 ϫ 500 mL), the combined organic layers were dried
(MgSO4), and concentrated under reduced pressure.·The residue
was purified by column chromatography (SiO2, CH2Cl2 and then
CH2Cl2/MeOH, 98:2, v/v) to yield ()-11 (3.0 g, 50%) as a brown
20
14%) as a white solid. Ϫ [α]589 ϭ ϩ45 (c ϭ 0.023 in CHCl3). Ϫ
LSIMS; m/z: 616 [M]ϩ. Ϫ 1H NMR (300 MHz, CDCl3, 25°C): δ ϭ
6.81 (8 H, s), 4.53 (4 H, m), 4.20Ϫ3.95 (20 H, m), 3.90Ϫ3.70 (8 H,
m). Ϫ 13C NMR (75.5 MHz, CDCl3, 25°C): 153.0, 115.8, 80.8,
80.7, 71.5, 69.6, 68.6. Ϫ C32H40O12 (616.60): calcd. C 62.33, H 6.54;
found C 62.44, H 6.45.
20
oil. Ϫ [α]589 ϭ ϩ59 (c ϭ 0.03 in CHCl3). Ϫ LSIMS; m/z: 543 [M
[2]Catenane (DD)-14·4PF6: A solution of 5·2PF6 (55 mg, 0.078
1
ϩ H]ϩ. Ϫ H NMR (300 MHz, CDCl3, 25°C): δ ϭ 7.80 (4 H, d, mmol), 6 (25 mg, 0.095 mmol), and ()-13 (70 mg, 0.114 mmol)
J ϭ 8 Hz), 7.35 (4 H, d, J ϭ 8 Hz), 4.48 (2 H, m), 4.18 (4 H, m), in dry MeCN (30 mL) was stirred for 12 d at ambient temp. The
3.98Ϫ3.55 (10 H, m), 2.45 (6 H, s). Ϫ 13C NMR (75.5 MHz, solvent was removed under reduced pressure and the residue was
1002
Eur. J. Org. Chem. 1999, 995Ϫ1004

Molecular Meccano, 51
FULL PAPER
purified by column chromatography (SiO2: MeOH/2  aq. NH4Cl/
MeNO2, 7:2:1, v/v/v). The resulting solid was dissolved in H2O and
a saturated aqueous solution of NH4PF6 was added until no
further precipitation occurred. The red precipitate was washed sev-
eral times with MeNO2/H2O to yield ()-14·4PF6 (25 mg, 17%)
65.8, 63.5. Ϫ C82H80F24N4O14P4 (1925.40): calcd. C 51.15, H 4.19;
found C 51.35, H 4.26.
General Procedure for the Competition Experiments: Known
amounts (0.04Ϫ0.20 mmol) of the reagents (Tables 1 and 2) were
stirred in MeCN (20Ϫ30 mL) at ambient temp. The mixtures were
then purified by column chromatography (SiO2: MeOH/2  aq.
NH4Cl/MeNO2, 7:2:1, v/v/v and then MeOH/1  aq. NH4Cl, 7:3,
v/v). We estimate an error of 2% as a result of instrumentation and
sample manipulation.
as a red solid. Ϫ [α]25 ϭ Ϫ78 (c ϭ 0.003 in Me2CO). Ϫ LSIMS;
578
m/z: 1735 [M ϩ H2O]ϩ, 1571 [M Ϫ PF6]ϩ, 1427 [M Ϫ 2PF6]ϩ,
1282 [M Ϫ 3PF6]ϩ. Ϫ 1H NMR [400 MHz, (CD3)2SO, 25°C]: δ ϭ
9.20 (8 H, d, J ϭ 7 Hz), 8.10 (8 H, bs), 7.92 (8 H, s), 6.28 (4 H, s),
5.74 (4 H, d, J ϭ 13 Hz), 5.64 (4 H, d, J ϭ 13 Hz), 4.90 (2 H, m),
4.60 (2 H, m), 4.3Ϫ3.5 (28 H, m), 3.30 (4 H, s). Ϫ 13C NMR [75.5
MHz, (CD3)2SO, 25°C]: δ ϭ 153.4, 151.6, 147.5, 145.9, 137.9,
132.1, 127.0, 115.9, 114.3, 85.7, 82.1, 81.2, 80.7, 74.6, 72.6, 71.2,
70.8, 69.1, 68.7. Ϫ C68H72F24N4O12P4 (1717.13): calcd. C 47.56, H
4.23, N 3.26; found C 47.67, H 4.14, N 3.26.
Association Constants: A series of solutions with constant concen-
tration (1.15 ϫ 10Ϫ3 ) of either (RS)-3 or of ()-13 and contain-
ing different amounts of 4·2PF6 (10Ϫ4Ϫ10Ϫ1 ) in MeCN were
prepared. The absorbance at the wavelength (λmax) corresponding
to the maximum of the charge-transfer band for the 1:1 complex
was measured for all the solutions at 25°C. The correlations be-
tween the absorbance and the guest concentration was used[10] to
evaluate the association constant (Ka) by non-linear curve fitting.
[2]Catenane (R/R)-15·4PF6: A solution of (R)-3 (200 mg, 0.28
mmol), 5·2PF6 (100 mg, 0.14 mmol), and (R)-16 (80 mg, 0.17
mmol) in dry MeCN (30 mL) was stirred for 14 d at ambient temp.
The solvent was removed under reduced pressure and the residue
was purified by column chromatography (SiO2: MeOH/2  aq.
NH4Cl/MeNO2, 7:2:1, v/v/v and then MeOH/1  aq. NH4Cl, 7:3,
v/v). The resulting solid was dissolved in H2O and a saturated
aqueous solution of NH4PF6 was added until no further precipi-
tation occurred. The red precipitate was filtered and air dried to
yield (R/R)-15·4PF6 (57 mg, 24%) as a red solid. Ϫ [α]58925 ϭ ϩ131
(c ϭ 0.002 in MeCN). Ϫ LSIMS; m/z: 1876 [M Ϫ PF6]ϩ, 1731 [M
Ϫ 2PF6]ϩ, 1586 [M Ϫ 3PF6]ϩ. Ϫ HRLSIMS; m/z calcd. for [M
High-Performance Liquid Chromatography: (RS)-3 was analyzed at
ambient temperature by employing a Chiralcel OD-H column flow
rate ϭ 1.0 mL/min; mobile phase heptane/EtOH, 80:20, v/v; detec-
tor wavelength ϭ 230 nm]. The retention times of (S)-3 and (R)-3
were 14 and 16 min, respectively. The diasteroisomeric mixtures of
the [2]catenanes 15·4PF6 and 18·4PF6 were analyzed at ambient
temperature by employing a Hypersil BDS C18 column {flow
rate ϭ 1.0 mL/min; mobile phase: pump A ϭ 0.1% CF3CO2H in
H2O, pump B ϭ (0.1% CF3CO2H in MeCN)/(0.1% CF3CO2H in
H2O), 95:5, v/v; time [min]/pump A (%) ϭ 0/50, 0.10/50, 5/60, 12/
100, 40/100, 45/50; detector wavelength ϭ 260 nm}.
1
Ϫ 2PF6]ϩ (C92H88F12N4O12P2) 1730.5686, found 1730.5609. Ϫ H
NMR [400 MHz, (CD3)2CO, 0°C]: δ ϭ 9.33 (4 H, d, J ϭ 7 Hz),
9.13 (4 H, d, J ϭ 7 Hz), 8.53 (2 H, s), 8.37 (2 H, bs), 8.08 (2 H, d,
J ϭ 7 Hz), 8.02 (4 H, d, J ϭ 7 Hz), 7.98 (4 H, s), 7.96 (4 H, d,
J ϭ 7 Hz), 7.78Ϫ7.71 (4 H, m), 7.47 (2 H, m), 7.43 (2 H, m), 7.33
(2 H, m), 7.23 (2 H, m), 7.18 (2 H, d, J ϭ 7 Hz), 7.02 (2 H, d, J ϭ
8 Hz), 6.27 (2 H, d, J ϭ 14 Hz), 6.10 (2 H, d, J ϭ 14 Hz), 6.00 (2
H, d, J ϭ 13 Hz), 5.87 (2 H, d, J ϭ 13 Hz), 4.83 (4 H, br. s),
4.2Ϫ3.5 (32 H, m). Ϫ 13C NMR [75.5 MHz, (CD3)2CO, 25°C]: δ ϭ
155.4, 153.9, 151.8, 148.0, 147.9, 146.8, 146.0, 137.6, 135.8, 134.6,
134.4, 131.6, 130.7, 130.6, 129.9, 129.6, 129.1, 128.7, 127.4, 126.7,
125.9, 125.8, 125.2, 125.1, 124.8, 122.9, 121.6, 118.0, 114.7, 113.7,
71.5, 71.3, 70.9 ,70.7, 70.6, 70.3, 69.8, 67.7, 65.6, 63.6.
Acknowledgments
The Glaxo Chromatography Department is gratefully acknowl-
edged for the HPLC analysis of the crown ether 3 and for financial
support along with the Engineering and Physical Sciences Research
Council in the United Kingdom.
[1]
[1a]
For accounts, books, and reviews on catenanes, see:
G.
Schill, Catenanes, Rotaxanes and Knots, Academic Press, New
[1b]
York, 1971. Ϫ
3161Ϫ3212. Ϫ
D. M. Walba, Tetrahedron 1985, 41,
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[1c]
Chem. Rev. 1987, 87, 795Ϫ810. Ϫ [1d] J.-P. Sauvage, Acc. Chem.
[2]Catenane (R/DD)-18·4PF6: A solution of 5·2PF6 (55 mg, 0.08
mmol), ()-13 (70 mg, 0.11 mmol), and (R)-16 (43 mg, 0.09 mmol)
in dry MeCN (30 mL) was stirred for 14 d at ambient temp. The
solvent was removed under reduced pressure and the residue was
purified by column chromatography (SiO2: MeOH/2  aq. NH4Cl/
MeNO2, 7:2:1, v/v/v and then MeOH/1  aq. NH4Cl, 7:3, v/v).
The resulting solid was dissolved in H2O and a saturated aqueous
solution of NH4PF6 was added until no further precipitation oc-
curred. The red precipitate obtained was washed several times with
MeNO2/H2O to yield (R/)-18·4PF6 (40 mg, 26%) as a red solid.
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Res. 1990, 23, 319Ϫ327. Ϫ
C. O. Dietrich-Buchecker, J.-P.
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Sauvage, Bioorg. Chem. Front.,1991, 2, 195Ϫ248. Ϫ
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M. Belohradsky, F. M. Raymo, J. F. Stoddart,
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25
Ϫ [α]589 ϭ ϩ80 (c ϭ 0.008 in MeCN). Ϫ LSIMS; m/z: 1947 [M
Nepogodiev, J. F. Stoddart, Chem. Rev. 1998, 98, 1959Ϫ1976.
ϩ Na]ϩ, 1778 [M Ϫ PF6]ϩ, 1635 [M Ϫ 2PF6]ϩ, 1490 [M Ϫ 3PF6]ϩ.
Ϫ 1H NMR (400 MHz, CD3COCD3, 31°C): δ ϭ 9.27 (4 H, d, J ϭ
7 Hz), 9.20 (4 H, d, J ϭ 7 Hz), 8.51 (2 H, s), 8.30 (2 H, s), 8.17 (4
H, d, J ϭ 7 Hz), 8.13 (4 H, d, J ϭ 7 Hz), 8.11 (4 H, s), 8.08 (2 H,
d, J ϭ 8 Hz), 7.50 (2 H, dt, J ϭ 1.5, 8 Hz), 7.41 (2 H, dt, J ϭ 1.5,
8 Hz), 7.12 (2 H, d), 6.34 (2 H, d, J ϭ 14 Hz), 6.13 (2 H, d, J ϭ
14 Hz), 6.05 (2 H, d, J ϭ 13 Hz), 5.98 (2 H, d, J ϭ 13 Hz), 5.50
(8 H, br. s), 4.68 (4 H, br. s), 4.21Ϫ3.55 (28 H, m). Ϫ 13C NMR
(75.5 MHz, CD3COCD3, 25°C): δ ϭ 153.9, 153.8, 148.7, 148.2,
146.4, 145.7, 137.8, 136.2, 135.6, 131.9, 129.9, 129.7, 129.3, 127.6,
126.5, 125.4, 124.9, 122.1, 115.5, 114.0, 81.1, 81.0, 73.0, 70.4, 68.7,
[1o]
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D. G. Hamilton, J. E. Davies, L. Prodi, J. K. M. Sanders,
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For accounts and reviews on the kinetically controlled self-as-
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D. Philp, J. F. Stoddart, Synlett
[2b]
1991, 445Ϫ458. Ϫ
D. Pasini, F. M. Raymo, J. F. Stoddart,
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