The exclusivity of multivalency in dynamic covalent processes

Article abstract of DOI:10.1002/anie.200453963

Less is more: It is much less efficient to synthesize both components of a multivalent recognition site separately than it is to use one multivalent component to act as a template for the catalytically orchestrated construction of the other component, as

Full text of DOI:10.1002/anie.200453963

Angewandte
Chemie
[7]
Mechanically Interlocked Compounds
tion.The advent of dynamic covalent chemistry
has,
however, opened up an attractive alternative route[13] to
mechanically interlocked molecules which relies upon the
thermodynamically controlled strict self-assembly of their
covalently linked components proceeding in unison with
mechanical bond formation under the guidance of the
templation provided by noncovalent interactions.In partic-
ular, it has been shown that 1) the reversible ring-closing
metathesis (RCM) reaction and 2) the ring-opening, ring-
closing metathesis (RORCM) reaction, also operating under
equilibrium control, are both mediated by functional-group-
tolerant ruthenium–alkylidene catalysts[14] and can be used[15]
in the thermodynamically controlled synthesis of catenanes
and rotaxanes.[16] In the specific knowledge that [2]rotax-
anes[17] and [3]catenanes,[18] where the supramolecular assis-
tance[19] for their formation comes from the interaction[20] of
The Exclusivity of Multivalency in Dynamic
Covalent Processes**
´
Jovica D. Badjic, Stuart J. Cantrill, Robert H. Grubbs,*
Erin N. Guidry, Raul Orenes, and J. Fraser Stoddart*
Natureꢀs reliance on multivalency[1] as a means[2] of compen-
sating for weak monovalent protein–ligand interactions is
now a widely accepted phenomenon[3] which controls a
panoply of biological events and whose delicate manipula-
tions could have far-reaching therapeutic implications.In
recent times, the physical basis of multivalency effects, based
on a thermodynamic model combined with computational
studies, has been explored rigorously[4] and a comprehensive
thermodynamic investigation of the calcium–EDTA interac-
tions has been reported.[5] Since thermodynamics seem, by
and large,[6] to rule the roost as far as multivalency is
concerned, it occurred to us that it should be the perfect
phenomenon to probe using the concept of dynamic covalent
chemistry.[7] Herein we describe a situation in which the
concept works in the exclusive context of the phenomenon;
that is, dynamic covalent chemistry can be achieved in a
highly efficient manner using multivalent ligands, but fails
altogether when no ligand or a monovalent counterpart is
employed.
As a part of some on-going research to probe multi-
valency in artificial systems[8] exhibiting molecular recogni-
tion, we have recently uncovered a compelling example[9] of
multivalency between a tritopic receptor, in which three
benzo[24]crown-8 rings are fused onto a triphenylene core,
and a trifurcated trication, wherein three dibenzylammonium
ions are linked 1,3,5 to a central benzenoid core: the outcome
is an extremely stable (Ka > 107 molLÀ1 in CH2Cl2) triply
threaded, two-component superbundle.This observation led
subsequently to the template-directed synthesis[10] of a proto-
type[11] of an artificial molecular machine,[12] namely, a
mechanically interlocked, triply threaded, molecular bundle
by kinetically controlled post-assembly covalent modifica-
+
CH2NH2 CH2 ion centers, either by developing olefinic crown
ether analogues containing 24-membered rings or with
dibenzo[24]crown-8, we decided to explore the possibility
that the multivalency effect can be exploited during RCM and
RORCM.We demonstrate that it can be exploited in a
convincing manner: multivalency flourishes in situations
where monovalency falters.
As outlined in Schemes 1 and 2, respectively, we have
prepared the triphenylene hexa-olefin 3 and the trifurcated
trisammonium salt [5-H3][PF6]3 by standard protocols (see the
Experimental Section).Their 1H NMR spectra, recorded in
CD3CN and CDCl3, respectively, are reproduced in Figure 1a
and b, respectively.When a solution of 3 (15 mm) in CD2Cl2 at
[*] Prof. R. H. Grubbs, E. N. Guidry
Arnold and Mabel Beckman Laboratory of Chemical Synthesis
Division of Chemistry and Chemical Engineering
California Institute of Technology
Pasadena, CA 91125 (USA)
Fax: (+1)626-564-9297
E-mail: rhg@caltech.edu
´
Dr. J. D. Badjic, Dr. S. J. Cantrill, R. Orenes, Prof. J. F. Stoddart
California NanoSystems Institute and
Department of Chemistry and Biochemistry
University of California, Los Angeles
405 Hilgard Avenue, Los Angeles, CA 90095 (USA)
Fax: (+1)310-206-1843
E-mail: stoddart@chem.ucla.edu
[**] We thank the National Science Foundation (CHE 0317170) for
funding this research which is also supported in part by equipment
grants (CHE 9974928 and CHE 0092036) from the National Science
Foundation. We also thank the Office of Naval Research for support
through its MURI program.
Scheme 1. Synthesis of the hexa-olefin 3. DMAP=4-dimethylaminopyr-
idine, DMF=dimethylformamide, Ts=toluene-4-sulfonyl.
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a considerable entropy loss which most likely would swamp a
very small enthalpic gain.
When a mixture (each 15 mm in CD2Cl2 at 408C) of 3 and
[5-H3][PF6]3 was subjected to
a RCM reaction using
[(PCy3)2(Cl)2Ru CHPh] (1.6 mm, 11 mol%), the 1H NMR
spectrum recorded after 4 h revealed a complex array of well-
defined resonances.With the aid of 2D NMR ( 1H-1H COSY)
experiments, almost all the resonances could be assigned to an
=
=
isomeric mixture of [6-H3][PF6]3 containing C C double
bonds with both E and Z configurations.The formation
(Scheme 3) of the mechanically interlocked molecular
“bundle” [6-H3][PF6]3 with averaged quasi C3v symmetry is
consistent with the 1H NMR spectroscopic data (see Fig-
Scheme 2. Syntheses of the trisammonium tris(hexafluorophosphate)
ure 1c).The methylene protons H and He on the carbon
salts [4-H3][PF6]3 and [5-H3][PF6]3. THF=Tetrahydrofuran
d
atoms adjacent to the secondary dialkylammonium centers in
[6-H3][PF6]3 resonate as broad multiplets centered on d = 4.63
and 4.74 ppm: these “same” protons resonate as sharp singlets
at d = 4.20 and 4.29 ppm in [5-H3][PF6]3.The downfield shifts
and the multiplicities exhibited by Hd and He in [6-H3][PF6]3
are diagnostic of their having been threaded by benzo[24]-
crown-6 rings, that is, they demonstrate the interlocked nature
of the “two” components in [6-H3]3+.Furthermore, the
resonances of the aromatic core protons Ha and Hh at d =
7.72 and 7.44 ppm, respectively, in the “two” components
within [6-H3]3+ are shifted significantly upfield relative
(Figure 1a and b) to the chemical shifts (d = 7.96 and
7.88 ppm, respectively) of the analogous protons in the
individual components—namely [5-H3]3+ and 3, respec-
tively—which indicates p-p stacking of the central aromatic
cores of the components with respect to one another.The
=
408C is treated with [(PCy3)2(Cl)2Ru CHPh] (1.6 mm,
11 mol%), a complex mixture of products is formed, as
indicated by thin layer chromatography and 1H NMR
spectroscopy.A very similar outcome emerged when a
mixture of 3 (15 mm) with the monovalent bis-3,5-dimethoxy-
benzylammonium hexafluorophosphate[17] (45 mm) was
treated under exactly the same reaction conditions with the
same ruthenium–alkylidene catalyst.Thus, both without and
with a monovalent template, little or none of the desired
crown ether analogue 7, or the anticipated[4] rotaxane, are
formed.The reasons for these observations could relate to the
myriad of potential products that could be formed by
different intramolecular RCM reactions.Also, amplification
by the monovalent template to give a [4]rotaxane would incur
Figure 1. The 1H NMRspectra (500 MHz, 298 K) of a) the trifurcated trisammonium salt [ 5-H3][PF6]3 (15 mm in CD3CN), b) the hexa-olefin 3
(15 mm in CDCl3), c) the mechanically interlocked “bundle” [6-H3][PF6]3 (15 mm in CD2Cl2), and d) the hydrogenated [6-H3][PF6]3 (15 mm in
CD2Cl2). Asterisk=residual solvent.
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=
Scheme 3. The efficient preparation of the mechanically interlocked “bundle” [6-H3][PF6]3 as a mixture of isomers containing C C bonds with both
E and Z configurations can be achieved through either a ring-closing metathesis (RCM) reaction starting from an equimolar mixture (each 15 mm
=
in CH2Cl2 at 408C) of the trifurcated trisammonium salt [5-H3][PF6]3 and hexa-olefin 3 using the functional group tolerant [(PCy3)2(Cl)2Ru CHPh]
(1.6 mm, 11 mol%) catalyst or ring-closing ring-opening metathesis (RORCM) reaction starting from an equimolar mixture (each 16 mm in
=
CH2Cl2 at 258C) of the trifurcated trisammonium salt [5-H3][PF6]3 and triscrown 7 using the catalyst [(IMesH2)(PCy3)(Cl)2Ru CHPh] (2.35 mm,
15 mol%). The synthesis of the triscrown 7 is shown on the left side. A triply threaded two component “superbundle” is assembled from an equi-
molar mixture (25 mm each in CH2Cl2 at 408C) of 3 and the trifurcated trisammonium tris(hexafluorophosphate) salt [4-H3][PF6]3 containing
=
[(PCy3)2(Cl)2Ru CHPh] (1.6 mm, 6 mol%) as the catalyst. The 1:1 complex formed as a result of this RCM reaction was then treated with a slight
excess (>3 equiv) of Et3N to deprotonate the [4-H3]3+ component and so release[9] the tris(crown ether) 7 as a mixture of isomers where the C C
=
bonds in the macrorings have either E or Z configurations.
almost quantitative production[21] of [6-H3][PF6]3 is presum-
ably the result of the build-up of cooperative binding
interactions, which result from the three productive RCM
reactions that lead to the statistical and cluster effects[8]
associated with the multivalency that characterizes the
PtO2) of all the (E/Z) olefinic bonds present in [6-H3][PF6]3
yielded (72%) a mechanically interlocked bundle with
averaged C3v symmetry as evidenced (Figure 1d) by
1H NMR spectroscopy.The “resonance” at d = 5.53 ppm for
the olefinic protons Hi in [6-H3][PF6]3 disappears and is
replaced by a signal centered on d = 1.57 ppm for protons
thermodynamically stable product.Hydrogenation (H
/
2
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associated with CH2 groups located in the middle of poly-
methylene chains.
using a template, to make a component—namely, the
tris(crown ether) 7—for use subsequently in a successful
RORCM reaction, using another template, to make a
“bundle” incorporating that component.
We have also discovered that it is possible to assemble [6-
H3][PF6]3 directly from the situation (Scheme 3) wherein both
components—that is, [5-H3]3+ and 7—are already preformed.
The tris(crown ether) 7 was synthesized by, first of all,
constructing a triply threaded two-component “superbundle”
from an equimolar mixture (25 mm each in CH2Cl2 at 408C)
of 3 and the trifurcated trisammonium tris(hexafluorophos-
Since the multivalency effect[1–6] is primarily a thermody-
namic phenomenon, it seems entirely reasonable that multi-
valent sites between two or more components can be created
spontaneously in situ by dynamic covalent chemistry,[7]
a
concept wherein reactivity is expressed in a thermodynamic
context.The results reported here, together with those
already described in the literature,[9,10] demonstrate that it is
much less efficient to synthesize both components of a
multivalent recognition site separately than it is to use one
multivalent component to act as a template for the catalyti-
cally orchestrated construction of the other component.The
situation is reminiscent of nature which frequently uses
enzymes, in conjugation with self-assembly processes, to build
up large and functional molecular structures.We foresee
developments in polymer chemistry where the dynamic
interplay between molecular recognition and the reversible
formation of covalent (and mechanical) bonds using suitable
catalysts will lead to the efficient production of high-
molecular-weight polymers just as rich in information content
as are many biopolymers.
phate)[9] salt [4-H3][PF6]3 containing [(PCy3)2(Cl)2Ru CHPh]
=
(1.6 mm, 6 mol%) as the catalyst.The 1:1 complex formed as
a result of this RCM reaction was then treated with a slight
excess (> 3 equiv) of Et3N to deprotonate the [4-H3]3+
component and so release[9] the tris(crown ether) 7 as a
=
mixture of isomers in which the C C bonds in the macrorings
have either E or Z configurations.The “compound” was
isolated in 69% yield following chromatography.Hydro-
=
genation (H2/PtO2) of the C C bonds in 7 afforded a pure
saturated tris(crown ether) which was fully characterized by
1H NMR spectroscopy and mass spectrometry.Next, a
solution of [5-H3]3+ and 7—each 16 mm in CD2Cl2—was
prepared and an 1H NMR spectrum was recorded (Figure 2).
Experimental Section
1: A solution of diethylene glycol (71 g, 0.67 mol), 5-bromo-1-pentene
(10 g, 0.17 mol) in H2O containing NaOH (13.4 g, 0.33 mol) was
heated at 808C for 24 h.A standard work-up procedure gave a crude
product, which was purified by column chromatography (SiO2:hex-
1
anes/Et2O, 1:1), to yield 1 as a colorless oil (11.7 g, 76%). H NMR
(500 MHz, CDCl3): d = 1.64 (m, 2H), 2.05 (m, 2H), 3.42 (m, 2H), 3.61
(m, 8H), 4.94 (m, 2H), 5.74 ppm (m, 1H); 13C NMR (125 MHz,
CDCl3): d = 28.5, 30.0, 61.5, 70.0, 70.2, 70.6, 72.4, 114.6, 138.0 ppm.
2: Compound 1 (3.0 g, 17.0 mmol), Et3N (8.6 g, 85.0 mmol), and a
few crystals of DMAP were dissolved in dry CH2Cl2 (50 mL) and a
solution of TsCl (7.0 g, 36.0 mmol) in dry CH2Cl2 (100 mL) was added
over 2 h.The reaction mixture was stirred overnight before being
subjected to a standard work-up procedure.Column chromatography
(SiO2, hexanes/Et2O, 1:1) of the crude product afforded 2 as a pale
yellow oil (4.9 g, 87%). 1H NMR (500 MHz, CDCl3): d = 1.63 (m,
2H), 2.06 (m, 2H), 2.42 (s, 3H), 3.41 (t, J = 7 Hz, 2H), 3.48 (m, 2H),
3.55 (m, 2H), 3.67 (t, J = 5 Hz, 2H), 4.14 (t, J = 5 Hz, 2H), 4.94 (m,
2H), 5.77 (m, 1H), 7.31 (d, J = 8 Hz, 2H), 7.77 ppm (d, J = 8 Hz, 2H);
13C NMR (125 MHz, CDCl3): d = 21.5, 28.6, 30.1, 68.5, 69.1, 69.9, 70.6,
70.7, 114.6, 127.8, 129.7, 132.9, 138.1, 144.7 ppm. HRMS (EI): m/z
found: 329.1425, calcd for C14H25O5S: 329.1423 [M+H]+.
Figure 2. Partial 1H NMRspectra (500 MHz, CD 2Cl2, 16 mm each,
298 K) of an equimolar mixture of [5-H3][PF6]3 and 7, before (0 min)
and after (6–153 min) addition of the catalyst [(IMesH2)(PCy3)(Cl)2Ru
CHPh] (2.35 mm, 15 mol%), which shows the exclusive formation
(>95%) of the mechanically interlocked “bundle” [6-H3][PF6]3 with
time in a series of RORCM reactions. Asterisk=residual solvent.
=
3: An oven-dried 1 L three-necked, round-bottomed flask,
equipped with a stirrer bar, a gas-inlet tube, a dropping funnel, and
a condenser, was purged with Ar for 10 min and then filled with
anhydrous DMF (150 mL).Cs 2CO3 (10.1 g, 31.0 mmol) was added to
the flask and the white suspension stirred vigorously with heating at
It revealed that, even though the two components do not form
1008C.The dropping funnel was charged with
a solution of
a supramolecular bundle, an RORCM reaction does take
2,3,6,7,10,11-hexahydroxytriphenylene (500 mg, 1.6 mmol) and
2
=
(4.1 g, 12.4 mmol) in anhydrous DMF (250 mL) and this solution
was added dropwise over 24 h to the suspension, which was then
heated at 1008C for another 3 days.On cooling the reaction mixture
down to room temperature, the suspension was filtered off and the
place upon addition of [(IMesH2)(PCy3)(Cl)2Ru CHPh]
(2.3 mm, 15 mol%) as the catalyst.[22] The equilibration
process was followed (Figure 2) by H NMR spectroscopy:
equilibrium was attained in about 150 minutes to give a 95%
yield of the mechanically interlocked two-component
“bundle” [6-H3][PF6]3 which was also characterized by mass
spectrometry.Hence, an RCM reaction has been employed,
1
residue was washed with CHCl3 (250 mL).The filtrate and CHCl
3
washings were concentrated under reduced pressure.The resulting
dark tar was dissolved in CHCl3 (200 mL) and washed with 10%
aqueous K2CO3 (2 ” 150 mL) and finally with brine (150 mL).The
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organic layer was dried (Na2SO4), filtered, and concentrated under
reduced pressure to afford a crude product which was subjected to
column chromatography (SiO2, hexanes/EtOAc, 4:6) to yield 3 as a
6H), 6.47 (brt, 3H), 6.79 (d, J = 2 Hz, 6H), 7.47 (s, 6H), 7.58 (d, J =
8 Hz, 6H), 7.71 (s, 3H), 7.83 (d, J = 8 Hz, 6H), 7.96 ppm (brs, 6H);
13C NMR (125 MHz, CD2Cl2): d = 25.7, 27.9, 29.6, 51.9, 52.8, 55.3,
67.9, 70.7, 71.2, 72.1, 73.0, 100.5, 104.4, 106.0, 120.5, 123.1, 125.8, 129.0,
129.6, 133.8, 136.5, 138.1, 145.9, 161.2 ppm; MS (MALDI): m/z (%):
2319.0 [MÀPF6]+ (5), 2174.1 [MÀ2PF6]+ (40), 2028.1 [MÀHÀ3PF6]+
1
yellow oil (400 mg, 20%); H NMR (500 MHz, CDCl3): d = 1.66 (m,
12H), 2.08 (m, 12H), 3.46 (t, J = 7 Hz, 12H), 3.62 (t, J = 5 Hz, 12H),
3.78 (t, J = 5 Hz, 12H), 3.98 (t, J = 5 Hz, 12H), 4.39 (t, J = 5 Hz, 12H),
4.95 (m, 12H), 5.77 (m, 6H), 7.87 ppm (s, 6H); 13C NMR (125 MHz,
CDCl3): d = 28.6, 30.1, 69.1, 69.8, 70.1, 70.6, 70.8, 107.9, 114.6, 123.8,
138.1, 148.6 ppm. HRMS (MALDI): m/z found: 1283.7393, calcd for
C72H108O18Na: 1283.7428 [M+Na]+.
(100).HRMS (ESI):
m/z found: 1087.5990, calcd for
C120H162O24N3PF6: 1087.5606 [MÀ2PF6]2+
.
7: A solution of 3 (96 mg, 0.076 mmol) and [4-H3][PF6]3 (84 mg,
0.076 mmol) in anhydrous CH2Cl2 (3 mL) was purged with argon for
=
10 min.The catalyst [(PCy 3)2(Cl)2Ru CHPh] (4 mg, 0.005 mmol) was
[4-H3][PF6]3: The synthesis of this trisammonium tris(hexafluoro-
phosphate) salt has been reported previously.[9]
added under a dry Ar atmosphere and the reaction mixture heated at
408C for 4 h.The solvent was evaporated off under reduced pressure
and several drops of Et3N added, followed by CH2Cl2 (5 mL).The
solvent was once again removed under reduced pressure and the
crude product subjected to column chromatography (SiO2, CH2Cl2/
MeOH, gradient from 10:0 to 8:2) to yield 7 as a white solid (62 mg,
69%) as a mixture of isomers. 1H NMR (500 MHz, CD2Cl2): d = 1.61
(m, 12H), 2.02–2.17 (m, 12H), 3.47 (m, 12H), 3.51 (m, 12H), 3.76 (m,
12H), 3.97 (m, 12H), 4.37 (m, 12H), 5.31–5.40 (m, 6H), 7.88 ppm (s,
6H).HRMS (MALDI): m/z found: 1199.6463, calcd for C66H96O18Na:
1199.6489 [M+Na]+.To complete the characterization of this
tris(crown ether), PtO2 (5.4 mg) was added to a solution of 7
(50 mg, 0.020 mmol) in anhydrous THF (8 mL), and the reaction
mixture was stirred under H2 for 5 h.The solvent was then removed
under reduced pressure and the crude product was subjected to
column chromatography (SiO2, CH2Cl2/MeOH, 95:5) to yield the
pure fully characterized hydrogenated derivative of 7 as an off-white
[5-H3][PF6]3: A mixture of 1,3,5-tris(p-formylphenyl)benzene
(1.0 g, 2.6 mmol) and 3,5-dimethoxybenzylamine (1.3 g, 7.7 mmol)
in PhMe (150 mL) was heated under reflux for 24 h and the H2O was
collected in a Dean–Stark apparatus.The solution was allowed to cool
down to room temperature and the solvent was evaporated under
reduced pressure to give the trisimine as a yellow oil (2.1 g, 99%).
This oil was dissolved in dry THF (60 mL) and dry MeOH (25 mL).
After the portionwise addition of NaBH4 (600 mg, 15.8 mmol), the
reaction mixture was left to stir overnight.5 m HCl (200 mL) was then
added to the reaction mixture, which was concentrated to a residue
that was partitioned between aqueous 2m NaOH solution (100 mL)
and CH2Cl2 (150 mL).The aqueous layer was then extracted further
with CH2Cl2 (100 mL).The combined organic extracts were washed
with H2O (100 mL) and then dried (Na2SO4).Filtration, followed by
solvent evaporation, gave the crude product which was subjected to
column chromatography (SiO2, hexanes/Et2O, 1:1) to afford the
trisamine as a pale yellow oil (1.0 g, 46%). 1H NMR (500 MHz,
CDCl3): d = 3.84 (s, 6H), 3.85 (s, 18H), 3.93 (s, 6H), 6.44 (t, J = 2 Hz,
3H), 6.60 (d, J = 2 Hz, 6H), 7.51 (d, J = 8 Hz, 6H), 7.73 (d, J = 8 Hz,
6H), 7.84 ppm (s, 3H). This oil was dissolved in THF/MeOH (30 mL,
25:5) and concentrated 12m HCl (30 drops) was added.The reaction
mixture was stirred for 6 h and then filtered.The resulting white solid
was dissolved in hot MeOH/H2O and saturated aqueous NH4PF6
solution was added.The resulting suspension was extracted with
1
solid (38 mg, 75%). H NMR (500 MHz, CD2Cl2): d = 1.20–1.70 (m,
36H), 3.46 (t, J = 6 Hz, 12H), 3.60 (t, J = 5 Hz, 12H), 3.75 (t, J = 5 Hz,
12H), 3.97 (t, J = 5 Hz, 12H), 4.39 (t, J = 5 Hz, 12H), 7.92 ppm (s,
6H); 13C NMR (125 MHz, CD2Cl2): d = 25.5, 28.4, 29.2, 69.7, 70.2,
70.5, 71.1, 71.2, 108.7, 124.1, 148.9 ppm; HRMS (MALDI): m/z
found: 1205.7015, calcd for C66H102O18Na: 1205.6958 [M+Na]+.
“Magic ring” synthesis of [6-H3][PF6]3: Catalyst [(IMesH2)(P-
=
Cy3)(Cl)2Ru CHPh] (1.0 mg dissolved in CD2Cl2, 15 mol%) was
added to a solution of the tris(crown ether) 7 (9.6 mg, 0.008 mmol)
and the trisammonium salt [5-H3][PF6]3 (10.5 mg, 0.008 mmol) in
CD2Cl2 (0.5 mL) under a dry Ar atmosphere. The reaction to give [6-
H3][PF6]3 was followed (Figure 2) by 1H NMR spectroscopy at 298 K.
MeNO2 (50 mL).The MeNO extract was washed with H2O (4 ”
2
70 mL), dried (Na2SO4), filtered, and the solvent was removed
under reduced pressure to give [5-H3][PF6]3 as a white solid (1.2 g,
1
79%). H NMR (500 MHz, CD3CN): d = 3.79 (s, 18H), 4.19 (s, 6H),
4.29 (s, 6H), 6.55 (t, J = 2 Hz, 3H), 6.62 (d, J = 2 Hz, 6H), 7.59 (d, J =
8 Hz, 6H), 7.90 (d, J = 8 Hz, 6H), 7.96 ppm (s, 3H); 13C NMR
(125 MHz, CD3CN): d = 50.9, 51.4, 55.1, 100.9, 107.7, 117.2, 125.2,
127.7, 130.1, 130.7, 132.5, 141.3, 141.4, 161.2 ppm. HRMS (ESI): m/z
found: 844.4312, calcd for C54H58O6N3: 844.4320 [MÀ2HÀ3PF6]+.
[6-H3][PF6]3: A solution of 3 (58 mg, 0.046 mmol) and [5-H3]
[PF6]3 (59 mg, 0.046 mmol) in anhydrous CH2Cl2 (3.0 mL) was purged
Received: February 6, 2004 [Z53963]
Keywords: metathesis · molecular recognition ·
.
NMRspectroscopy · supramolecular chemistry
=
with Ar for 10 min.The catalyst [(PCy 3)2(Cl)2Ru CHPh] (4 mg,
[1] a) R.T.Lee, Y.C.Lee,
Glycoconjugate J. 2000, 17, 543 – 551;
0.005 mmol) was added under a dry Ar atmosphere and the reaction
mixture heated at 408C for 4 h.The solvent was evaporated off under
reduced pressure and the crude product subjected to column
chromatography (SiO2, CH2Cl2/MeNO2, 8:2) to yield [6-H3][PF6]3 as
a white solid (70 mg, 62%) and as a mixture of isomers. 1H NMR
(500 MHz, CD2Cl2): d = 1.77 (m, 12H), 2.10–2.40 (m, 12H), 3.60–4.10
(m, 60H), 3.73 (s, 18H), 4.60 (m, 6H), 4.74 (m, 6H), 5.47–5.55 (m,
6H), 6.50 (m, 3H), 6.80 (m, 6H), 7.44 (m, 6H), 7.60 (m, 6H), 7.72
(brs, 3H), 7.83 (d, J = 7 Hz, 6H), 7.95 ppm (brs, 6H); MS (MALDI-
TOF): m/z (%): 2313.9 [MÀPF6]+ (10), 2166.5 [MÀHÀ2PF6]+ (40),
2020.7 [MÀ2HÀ3PF6]+ (57).To complete the characterization of this
mechanically interlocked “bundle”, PtO2 (5.4 mg) was added to a
solution of [6-H3][PF6]3 (48 mg, 0.020 mmol) in anhydrous THF
(8 mL) and the reaction mixture was stirred under H2 for 4 h.The
solvent was then removed under reduced pressure and the crude
product purified by column chromatography (SiO2, CH2Cl2/MeNO2,
8:2) to yield the fully characterized derivative of [6-H3][PF6]3 as a
white solid (35 mg, 72%). 1H NMR (500 MHz, CD2Cl2): d = 1.40–1.70
(m, 36H), 3.50–4.15 (m, 60H), 3.74 (s, 18H), 4.71 (m, 6H), 4.80 (m,
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3278
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www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 3273 –3278