General approach for template-directed synthesis of macroheterocycles by ring-closing metathesis (RCM)

Article abstract of DOI:10.1002/adsc.200404282

A general method to prepare macroheterocycles is reported in which a rigid symmetric platinated tris-pincer tricationic complex (3) is used as a template. The system uses bisolefin functionalized pyridine ligands (1, 2) which selectively bind to the three platinum centers of the template resulting in pre-organization of the olefinic tails. By subjecting these pre-organized complexes (4) to olefin metathesis reaction conditions, the olefinic tails were interconnected affording several macroheterocycles of different compositions and sizes. Various pyridines with different substitution patterns (2,6- and 3,5-disubstituted) and different olefinic tails (aliphatic, polyether, and styryl) were synthesized and used in the cyclization reactions, showing the diversity of this method. It was found that only the use of 2,6-disubstituted pyridines resulted in the formation of the desired macrocycles while 3,5-difunctionalized pyridines gave only pyridinophane formation. Furthermore, the length of the olefinic tails needs to be at least eleven atoms (C or O) in order to suppress oligomerization in favor of macrocycle formation. Yields of up to 70% of the macrocycles were obtained using the first-generation [Cl ₂(Cy₃P)₂Ru=CHPh] or second-generation [Cl ₂(Cy₃P)(IMeS)Ru=CHPh] Grubbs' catalysts. Reactions of the platinated pincer pyridines with Schrock Mo-based metathesis catalysts results in exclusive olefin isomerization and no productive metathesis. The generated macrocycles (hosts) could effectively be separated from the template by addition of aqueous sodium chloride and reattached to the (recycled) template (guest). The X-ray structure determination of host-guest complex 10 is the definite proof for this reattachment and the perfect cyclic structure of the macrocycle.

Full text of DOI:10.1002/adsc.200404282

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General Approach for Template-Directed Synthesis of
Macroheterocycles by Ring-Closing Metathesis (RCM)
Alexey V. Chuchuryukin,a Preston A. Chase,a Harm P. Dijkstra,a
Bart M. J. M. Suijkerbuijk,a Allison M. Mills,b Anthony L. Spek,b, c
Gerard P. M. van Klink,a Gerard van Kotena,*
a
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht,
The Netherlands
Phone: (þ31)-30-253-3120, fax: (þ31)-30-252-3615, e-mail: g.vankoten@chem.uu.nl
b
Bijvoet Center for Biomolecular Research, Department of Crystal and Structural Chemistry, Utrecht University,
Padualaan 8, 3584 CH Utrecht, The Netherlands
Correspondence pertaining to crystallographic studies should be addressed to this author
c
E-mail: a.l.spek@chem.uu.nl
Received: September 6, 2004; Accepted: December 3, 2004
Dedicated to Prof. Dr. Richard Schrock on the occasion of his 60th birthday and in recognition of his highly
appreciated contribution to chemistry in general and his pioneering studies on ofefin metathesis in particular.
Abstract: A general method to prepare macrohetero- of the olefinic tails needs to be at least eleven atoms
cycles is reported in which a rigid symmetric platinat- (C or O) in order to suppress oligomerization in favor
ed tris-pincer tricationic complex (3) is used as a tem- of macrocycle formation. Yields of up to 70% of the
plate. The system uses bisolefin functionalized pyri- macrocycles were obtained using the first-genera-
¼
dine ligands (1, 2) which selectively bind to the three tion [Cl2(Cy3P)2Ru CHPh] or second-generation
¼
platinum centers of the template resulting in pre-or- [Cl2(Cy3P)(IMes)Ru CHPh] Grubbsꢀ catalysts. Reac-
ganization of the olefinic tails. By subjecting these tions of the platinated pincer pyridines with Schrock
pre-organized complexes (4) to olefin metathesis re- Mo-based metathesis catalysts results in exclusive ole-
action conditions, the olefinic tails were interconnect- fin isomerization and no productive metathesis. The
ed affording several macroheterocycles of different generated macrocycles (hosts) could effectively be
compositions and sizes. Various pyridines with differ- separated from the template by addition of aqueous
ent substitution patterns (2,6- and 3,5-disubstituted) sodium chloride and reattached to the (recycled) tem-
and different olefinic tails (aliphatic, polyether, and plate (guest). The X-ray structure determination of
styryl) were synthesized and used in the cyclization host-guest complex 10 is the definite proof for this re-
reactions, showing the diversity of this method. It attachment and the perfect cyclic structure of the
was found that only the use of 2,6-disubstituted pyri- macrocycle.
dines resulted in the formation of the desired macro-
cycles while 3,5-difunctionalized pyridines gave only Keywords: macrocyclic ligands; metathesis; N ligands;
pyridinophane formation. Furthermore, the length platinum; ring-closing metathesis; synthetic design
Introduction
the synthesis of macromolecular tri- and hexametallic
ECE-pincer complexes (A–C, Figure 1) and investigat-
Macroheterocyclic compounds are widely used as li- ed their use as recyclable homogeneous catalysts in a
gands for complexation to single metal cations and small nanofiltration membrane reactor.[7] Two interesting fea-
polar organic molecules (e.g., urea).[1] Additionally, tures of these molecules are their shape-persistent back-
Stoddart and co-workers have expanded the scope of bones and their highly symmetric geometries, two very
the crown-ether family in the development of, e.g., mo- important features for a polynuclear macromolecular
lecular shuttles,[2] switches,[3] and logic gates[4] using cat- template in the controlled synthesis of macrocycles.
enane and rotaxane chemistry.[5] Nevertheless, only a We anticipated that coordinating bifunctional ligands
few examples are described in the literature where mac- to the metal centers of these complexes should result
roheterocycles were used as ligands for complexation to in the pre-organization of the functional groups in
rigid polymetallic complexes.[6] Recently, we reported such a way that they can easily be interconnected to
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Figure 1. Symmetric shape-persistent tri- and hexametallic pincer complexes.
form macrocycles. In this approach the final ring-closing
Earlier we communicated the preliminary results on the
reaction (various side-reactions are anticipated) as well synthesis of tris(pyridyl)alkyl heteromacrocycles using
as the nature of the metal-to-ligand coordination bond platinated tri-NCN-pincer complex B (Figure 1) as a tem-
(needs to be sufficiently strong to suppress ligand disso- plate.[15] Here we report a full account of the use of this
ciation) are of crucial importance.
shape-persistent tri-metallic template for the general syn-
Olefin metathesis has developed into one of the most thesis of macroheterocycles of several compositions.
important synthetic methods for the selective genera-
tion of medium to large cyclic systems.[8] A few reports
in literature describe the synthesis of macroheterocycles Results and Discussion
by metathesis of olefin-substituted ligands in the coordi-
nation sphere of organometallic complexes. Most of As the starting materials for the template-directed mac-
these procedures use monometallic complexes as the rocycle synthesis, a number of 2,6-bisolefin substituted
templates.[9] Also the application of metathesis in the pyridines (1a–g) and a 3,5-bisolefin substituted pyridine
synthesis of catenanes,[10] molecular knots[11] and mo- (2a) were used (see Scheme 1). This selection enabled us
lecular wires, insulated with a double helix of alkene to study the influence of the length of the olefin-bearing
chains have been reported, in which a metal ion was chains as well as their positions on the pyridine rings
used as the template to ensure the desired geometry.[12] (3,5- or 2,6-substitution) on the selectivity and the yield
Recently, we reported a model study in which we ap- of the ring-closing reactions.
plied monometallic ECE-pincer complexes (E¼N, S,
The synthesis of the disubstituted pyridine ligands is
metal¼palladium, platinum) coordinated to bisolefin outlined in Scheme 1. Treatment of 2,6-dibromopyri-
functionalized pyridines in ring-closing metathesis dine with the in situ prepared sodium salts of the appro-
(RCM) reactions.[13] This study was performed to deter- priate olefinic alcohols in dry DMF gave 2,6-disubstitut-
mine the optimal reaction conditions for the application ed pyridines 1a – e in 82–97% yield [Scheme 1, Equa-
of metalated multi-ECE-complexes (see Figure 1) as tion (1)]. Pyridine derivatives 1f and g were obtained
templates in the synthesis of macrocycles. Pyridine li- in a two-step sequence; 2,6-pyridinedimethanol was first
gands were chosen because they form stable coordina- reacted with thionyl chloride and subsequent treatment
tion complexes with many palladium and platinum com- of the resulting 2,6-bis(chloromethyl)pyridinium chlor-
plexes and they can also be rather easily functionalized. ide with three equivalents of the in situ prepared sodium
It was found that the NCN-pincer platinum pyridine salts of 9-decen-1-ol (1f) or 5-hexen-1-ol (1g) yielded the
complexes were kinetically the most stable. In addition, corresponding pyridines 1f and 1g both in 97% yield
the pyridine ligated NCN-Pt moiety was found to be the [Scheme 1, Equation (2)]. Finally, treatment of 3,5-pyr-
least active catalyst in a competitive prototropic isomer- idinedicarboxylic acid with thionyl chloride and subse-
ization of the olefinic double bonds (a process known to quent reaction of 2,6-pyridinedicarbonyl dichloride
be catalyzed by a variety of transition metals[14]) to form with 9-decen-1-ol resulted, after a basic work-up, in
internal double bonds (which are considerably less ac- the formation of 2a in 92% yield [Scheme 1, Equa-
tive in metathesis), making this moiety the most attrac- tion (3)].
tive for the templated synthesis of polypyridine macro-
cycles.
The synthesis of the trispyridine-template complexes
is shown in Scheme 2. In all cases, the template precur-
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Scheme 1. Synthesis of bisolefin substituted pyridines. i) Appropriate sodium alkoxide, DMF, 958C, 16 h. ii) SOCl2, CH2Cl2,
RT, 16 h followed by sodium 9-decen-1-olate (1f) or sodium 5-hexen-1-olate (1g), THF, reflux, 4 h. iii) SOCl2, reflux, 16 h fol-
lowed by 9-decen-1-ol, CH2Cl2, reflux, 3 h.
Scheme 2. Synthesis of trispyridine-template complexes. i) AgBF4, CH2Cl2, RT, 16 h.
sor 3[7a] was reacted in dichloromethane with three ity of silver tetrafluoroborate in dichloromethane. Cati-
equivalents of the appropriate pyridine (1a–g or 2a) in onic complexes 4a, 4b, and 4e–h were obtained pure af-
the presence of suspended silver tetrafluoroborate, giv- ter removal of insoluble silver chloride and used
ing the cationic coordination complexes 4a–h, respec- immediately in the RCM reactions. In the case of pyri-
tively, in quantitative yields. In all cases, a prolonged re- dine derivatives 1c and 1d, however, significant amounts
action time (16 h) was necessary due to the poor solubil- of silver salts (~10 mol % of the total amount of silver
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Table 1. Conditions and yields of RCM reactions.
Starting material
Catalyst [mol %/pyridine]
Time [h]
Product
Yield [%9
¼
4a
4b
4c
4d
4e
4f
Cl2(Cy3P)2Ru CHPh (5)
16
6a
6b
6c
6d
6e
6f
6f
6 g
8
67
0
0
41
60
44
20
0
¼
Cl2(Cy3P)2Ru CHPh (5–10)
16–74
16–74
16
48
16
16
16–74
48
¼
Cl2(Cy3P)2Ru CHPh (5–10)
¼
Cl2(Cy3P)2Ru CHPh (5)
¼
Cl2(Cy3P)(IMes)Ru CHPh (15)
¼
Cl2(Cy3P)2Ru CHPh (5)
¼
4f
Cl2(Cy3P)(IMes)Ru CHPh (5)
¼
4 g
4 h
4a
Cl2(Cy3P)2Ru CHPh (5–10)
¼
Cl2(Cy3P)2Ru CHPh (12.5)
70
67
Schrock catalyst 11
16
12
tetrafluoroborate used) were still present in the final sol- gand) (Scheme 3). After detachment from the template
utions of the corresponding complexes 4c and 4d after by aqueous sodium chloride, the macroheterocycles 6a,
removal of insoluble silver chloride by filtration. This 6d and 6f were obtained as mixtures of cis/trans trisole-
is probably a result of partial solubilization of silver salts finic heteromacrocycles. The total yields of macrohe-
by the crown-ether like compounds 1c and 1d. It was ob- terocycles 6a, 6d and 6f, after isolation by preparative
served that complexes containing the dissolved silver thin-layer chromatography (TLC), varied from 41 to
salts did not undergo ring-closing metathesis possibly 67% (Table 1). The best yield was obtained with 4a
due to catalyst deactivation. Therefore, the residual dis- (forming 6a) in which the olefinic tail contains 11 atoms,
solved silver salts were removed by passing small whereas complexes 4d and 4f bearing pyridines with ole-
amounts of hydrogen sulfide through the reaction mix- finic tails of 13 and 12 atoms, respectively, gave some-
ture prior to metathesis. Large excess of hydrogen sul- what lower yields of 41 and 44% (which still equates
fide should be avoided since it causes reversible break- to>74% yield per double bond). In the case of pyridine
age of the platinum-N(pyridine) bond of the cationic substrates 1b, 1c and 1g (complexes 4b, 4c and 4g,
complexes 4c and 4d, resulting in mixtures of different Scheme 3) with olefinic chains bearing less than 11
pincer-ligand complexes (Pt-N and Pt-S complexes). atoms (O, C), no trispyridine macrocycles were ob-
The small excess of hydrogen sulfide was removed served on applying the same metathesis reaction condi-
from the reaction mixture by heating the reaction mix- tions. Also increasing the amount of metathesis catalyst
ture to reflux under a nitrogen atmosphere followed (up to 15 mol %) did not result in the formation of mac-
by removal of silver sulfide by filtration prior to meta- rocyclic metathesis products, instead predominantly lin-
thesis.
ear oligomers were found. These results show that the
Cationic complexes 4a–h were applied in olefin meta- length of the olefinic tail plays an important role in
thesis in the presence of first or second-generation this research with the optimum lying at 11 atoms (C,
Grubbsꢀ catalysts (5–15 mol % per pyridine ligand) O) for this particular template. A similar pyridinophane
(Scheme 3). In addition, metathesis with 4a was attempt- cyclization reaction was recently reported by Fꢂrst-
ed with Schrock Mo-based catalysts (vide infra). The ner.[16]
conditions for the RCM reactions and the yields of the
Template-directed RCM of the less active bis-styrene
obtained macrocycles are summarized in Table 1. The derivative 4e, on the other hand, was only possible in the
olefin metathesis reactions were performed under high presence of large amounts (15 mol %) of the more active
dilution (~10ꢀ3 M) to suppress intermolecular olefin second-generation Grubbsꢀ catalyst, [Cl2(PCy3)(IMes)-
¼
¼
metathesis polymerization. For analysis purposes, all Ru CHPh] [IMes 1,3-bis(2,4,6-trimethylphenyl)-4,5-
pyridine fragments were detached from the template af- dihydro-imidazol-2-ylidene]. In fact, applying the first-
ter metathesis by reacting the resulting platinum pyri- generation Grubbsꢀ catalyst in this reaction resulted in
dine complexes with an aqueous sodium chloride solu- no metathesis at all. The resulting macroheterocycle
tion, affording free metathesis products and the neutral 6e was originally isolated as the pure trans-trisolefin,
template precursor 3. The pyridine products could be however, it was found to undergo slow cis/trans-isomer-
completely separated from 3 by extraction with hexanes ization in solution when exposed to daylight.
In fact, as 3 is completely insoluble in hexanes, pure 3
was quantitatively recovered and could be reused in sub- 2,6- to 3,5-diolefin functionalized pyridines, resulted
sequent experiments. solely in pyridinophane RCM. Thus subjecting 4h to
Surprisingly, changing the substitution pattern from
Trispyridine-template complexes 4a, 4d and 4f were the RCM conditions gave only monopyridinyl macrocy-
converted into their corresponding trispyridine macro- cle (pyridinophane) 8 in 70% yield (Scheme 3); no indi-
cycles 5a, 5d and 5f using first-generation Grubbsꢀ cata- cation of a trispyridinyl macrocycle was observed even
¼
lyst [Cl2(PCy3)2Ru CHPh] (5 mol % per pyridine li- though the length of the olefinic chains (12 atoms) was
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Scheme 3. RCM with template-bound bisolefin-substituted pyridines. i) [Ru] catalyst 5–15 mol %, CH2Cl2, reflux. ii) NaCl,
H2O/CH2Cl2, RT, 20 h. iii) H2, Pd/C, RT, various solvents.
anticipated to be sufficient for trispyridinyl macrocycle prevented, affording 6e in high selectivity. Longer reac-
formation. Apparently, in case of 3,5-disubstituted pyri- tion times could be applied in this case since the styrene
dines, the two olefinic tails of one pyridine ligand can double bond does not suffer from the transition metal-
easily reach each other since there is hardly any steric catalyzed olefin isomerization reaction for obvious rea-
hindrance of the pyridine ring, making pyridinophane sons.
RCM preferable.[13] In the case of 2,6-disubstituted pyr-
As macrocycles 6 were formed as mixtures of cis/trans-
idines this undesired process is impeded due to steric trisolefinic heteromacrocycles, hydrogenation of the
hindrance of the pyridine ring and the NCN-Pt pincer; double bonds in 6 using H2 and Pd/C in CH2Cl2 was per-
an intramolecular RCM (to give a pyridinophane) formed to facilitate analysis, affording the correspond-
would have to take place via a back-flip conformation, ing saturated macrocycles 7 (Scheme 3). In the case of
which is highly unfavorable.
7f, some hydrogenolysis of the benzylic ether bonds
In the synthesis of 6a, 6d and 6f, not only the desired was observed as a side reaction.[17] Furthermore, it
macrocycles were obtained but also linear oligomers should be noted that according to mass spectrometry
were formed as minor side-products. In an attempt to in- the product mixtures of the saturated compounds 7a
crease the reaction rate and the selectivity of the RCM and 7f contained traces of macrocycles (<5%) having
reaction and to decrease the amount of catalyst, the one CH2 group less then the expected macrocycles.
more reactive second-generation Grubbsꢀ catalyst, These macrocycles were most likely formed through
¼
[Cl2(PCy3)(IMes)Ru CHPh], was used in the metathe- cross metathesis of an a-olefinic substituent (external
sis reaction of 4f (as a model reaction). Unfortunately, double bond) with a b-olefinic one (internal double
this led to a dramatic decrease in yield of macrocycle bond), the latter being formed by a metal-catalyzed pro-
6f (20%, Table 1), while large amounts of oligomers totropic isomerization reaction (vide supra).[14] Unfortu-
were formed. These findings point to the occurrence of nately, it was not possible to separate these macrocycles
secondary cross and ring-opening metathesis polymeri- from the desired products 7a and 7f by preparative TLC.
zation (ROMP) reactions. Onlyin the case ofstyrene de-
The macrocycles 7a, 7d and 7f, which are very flexible
rivative 4e did the second generation Grubbsꢀ catalyst and not preorganized (e.g., by conformational preferen-
give a satisfactory result (vide supra). Apparently, due ces in the connecting alkanediyl chains), were further
to the less-active nature of the double bonds of the styr- studied as hosts for the highly preorganized macromo-
ene moiety and the higher stability of the resulting stil- lecular trimetallic guest 3 (Scheme 4). The reactions of
benoid double bonds, cross-metathesis and ROMP are macrocycles 7a, 7d and 7f with 3 in dichloromethane in
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Scheme 4. Host-guest chemistry with macrocycles. i) AgBF4, CH2Cl2, RT, 16 h followed by work-up with acetone. ii) NaBPh4,
acetone, RT, 1 h.
the presence of silver tetrafluoroborate gave – after the pincer aryl rings is 40.2(2)8. The pincer groups are cy-
work-up with acetone – the corresponding complexes cloplatinated at the position between the two CH2NMe2
9a, 9d and 9f in almost quantitative yield (95–98%). substituents, yielding two five-membered PtCN2 chelate
Characterization of host-guest complexes 9 comprised rings per square planar platinum atom. A chloride anion
NMR spectroscopy, elemental analysis and electrospray trans to Cipso completes the square planar coordination
mass spectrometry. The mass and isotopic patterns in the environment of each platinum(II) center. The shape of
experimental spectra were identical to that in the calcu- the framework is most easily approximated as an equi-
ꢀ
lated spectra for the tricationic complexes 9. In spite of lateral triangle with sides defined by the Cl Cl distance
all the convincing evidence for the formation of macro- of 17.281(2) ꢃ. In the crystal structure of 10, the pe-
cycles using RCM, an X-ray crystal structure of one of ripheral chloride anions in 3 are replaced by the pyridine
the host-guest complexes would deliver the definite N atoms of the neutral macrocyclic ligand 7a (Figure 2);
ꢀ
proof for the perfect macrocyclic structure of com- the N N distances in the coordinated ligand range from
pounds 7 and for the reattachment of 7a, 7d and 7f to 16.684(7) to 17.196(6) ꢃ. The three pyridine rings, which
template 3. Crystallization of 9a from several solvent are linked by saturated O(CH2)18O bridges, are oriented
mixtures resulted in colorless crystals, however, in at angles of 84.3(4) to 89.8(3)8 with respect to the square
each case the quality of these crystals was too poor to re- planar PtCN3 coordination planes. The overall shape of
solve the crystalstructure (too much disorder in the crys- the template is retained upon reattachment of the tris-
tals). Therefore, we decided to replace the tetrafluoro- pyridine macrocycle, but the molecular symmetry is re-
borate counter ions of 9a for tetraphenylborate ions by duced. Each of the pincer-platinum moieties in 10 is tilt-
reacting 9a in acetone with sodium tetraphenylborate, ed at a different angle with respect to the central ben-
affording host-guest complex 10 (Scheme 4). Crystalli- zene ring, the twist angles between the different indivi-
zation of the resulting tris(tetraphenylborate) host- dual pincer aryl rings and the central aryl ring ranging
guest complex 10 from an acetone/diethyl ether mixture, from 25.6(3) to 85.1(5)8.
resulted in colorless crystals which could be resolved by
Attempts have also been made to perform RCM em-
an X-ray crystal structure determination (Figure 2). For ploying the high-oxidation state Mo-based alkylidene
comparison, we also crystallized the template molecule systems developed by Schrock.[8d] This was investigated,
3 from a dichloromethane/diethyl ether mixture and de- in part, to test the ability of the Pt cation to protect the
termined the X-ray crystal structure (Figure 3). The Lewis basic pyridine nitrogen[13] as the highly electro-
ꢀ
structure of the Pd Br version of tripincer 3 is also philic Schrock system is also sensitive to deactivation
known.[7a] As shown in Figure 3, the molecular structure by pyridine functionalities due to blockage of reactive
of the template precursor 3 consists of a central benzene sites by the Lewis base.[8d] Also of interest is comparison
ring that is substituted at the 1-, 3-, and 5-positions with of the RCM reaction using the highly active Schrock sys-
pincer-platinum moieties. Since the template possesses tem and that of the similarly active second-generation
exact D3 molecular symmetry, the three pincer-platinum Grubbsꢀ catalyst, where lower amounts of the desired
groups have the same geometry and orientation. The macrocycle were obtained (vide supra). Using identical
twist angle between the planes of the central ring and conditions to the aforementioned RCM reaction using
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Figure 2. ORTEP representation (50% probability) of 10. The tetraphenylborate anions and hydrogen atoms have been omit-
ted for clarity. Only the major conformation of each of the disordered groups is shown.
the Grubbsꢀ systems, 5 mol % (per pyridine) of bis(hexa- [M – 28] due to loss of one and two methylene units, re-
fluoro-tert-butoxide)(2,6-diisopropylphenylimido) (neo- spectively. Further evidence for isomerization was
phylidene)molybdenum (11) was reacted with pyridine- found in the 1H NMR spectrum where multiple sets of
ligated tricationic Pt pincer 4a in dichloromethane (see triplets at d¼0.86–0.96 were observed, indicating that
Scheme 5). Reactions at room temperature over the numerous chemo-isomeric internal olefin products are
course of 16 h indicated partial formation of internal present due to further inward migration of the double
olefins, consistent with metathesis. Significant conver- bond. In addition, the 13C NMR spectrum exhibits multi-
sion to internal olefin,>88% based on integrated olefin ple (>ten) carbon signals at d¼123.8–132.2 that corre-
signals in the 1H NMR spectrum, was observed on pro- late via HETCOR to the broad multiplet at d¼5.4 in the
longed reaction at room temperature (>30 hours) or 1H NMR spectrum, again due to multiple internal ole-
upon reflux for 16 hours.
Detachment of the pyridine with aqueous NaCl and
fins.
Olefin isomerization is a known, albeit typically mi-
purification of the product by preparative TLC resulted nor, side-reaction that is promoted by a number of active
in isolation of a single band; no product bands for dimer- olefin metathesis catalysts. The original “ill-defined”
ic or higher-order linear or cyclic oligomers were noted heterogeneous catalyst systems are known to promote
and the yield of the isolated product was 67%. Analysis olefin isomerization[8e,18] and there are a small number
of the product by 1H and 13C NMR spectroscopy, as well of reports in which the Grubbs-type Ru-based systems
as 1H-1H COSY and 1H-13C HETCOR, and by GC/MS also exhibit this feature,[19,20] with second-generation
indicated that extensive olefin isomerization had oc- catalysts exhibiting a greater propensity to accelerate
curred in the “tails” to give mixed cis/trans products of isomerization in some cases.[21] The Schrock Mo-based
type 12 (Scheme 5) and that no productive metathesis systems are also known in isolated cases to catalyze ole-
products were evident. The mass spectrum obtained ex- fin isomerization, although typically to a lesser extent.[22]
hibits a molecular ion peak at M¼388 (m/z), equivalent One example of olefin isomerization with 11 before
to those of the starting pyridine 1a; products of olefin RCM was reported in the attempted synthesis of a euni-
metathesis would exhibit mass values of [M – 14] and cellin diterpene derivative.[23]
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Figure 3. ORTEP representation (50% probability) of the template precursor 3. Hydrogen atoms have been omitted for clari-
ty.
tially no isomerization and did not react at room temper-
ature. Also, catalyst 11 is known to catalyze metathesis
of internal olefins under the conditions (temperature
and solvent) employed[8d] and, as such, the composition
of the catalyst may have been altered by reaction with
species present in the mixture. The exact nature of this
olefin isomerization catalyst is under investigation and
utility of combination olefin metathesis/isomerization
is being explored.
Conclusion
An efficient and selective method to prepare macrohe-
terocycles using templated synthesis is reported. We
have shown that the tris-NCN-Pt pincer complex 3 is a
Scheme 5. Olefin isomerization using Schrock catalyst 11. i)
5 mol % (per pyridine) 11, CH2Cl2, reflux. ii) NaCl, H2O.
suitable template for the construction of macrohetero-
cycles from pyridines containing two olefinic side chains
using RCM methodology with Grubbsꢀ Ru-based cata-
The data presented herein suggest that 11 is not com- lysts. This procedure yielded four different macrocycles
patible with the cationic platinated pincer pyridines in in which the side-chains connecting the pyridine moiet-
olefin metathesis. However, the combination of these ies contain different functionalities, showing the versa-
species generates an efficient olefin isomerization cata- tility of this method. However, the combination of
lyst. Olefin isomerization was also noted during prelimi- NCN-Pt pincer pyridine complexes and Schrock Mo-
nary studies employing mono-platinated and -palladat- based catalyst 11 resulted only in olefin isomerization
ed pincers.[13] In these cases, however, platinum species products. Only 2,6-diolefin substituted pyridines afford
with sufficiently elongated alkyl chains exhibited essen- trispyridinediyl-containing macroheterocycles whereas
454
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Template-Directed Synthesis of Macroheterocycles by RCM
3,5-diolefin substituted pyridines form pyridinophane the complexation of several guests (e.g., cations) within
macroheterocycles under RCM conditions (thus intra- one macrocycle.[25] We are currently further investigat-
pyridine RCM). Also the use of template-bound 2,6-bi- ing the host-guest properties mentioned above and we
solefin substituted pyridines with olefin side-chain less will present the results in due time.
then 11 atoms (O, C) did not produce trispyridinediyl-
containing macroheterocycles due to insufficient
lengths of the olefinic tails; instead oligomeric pyridine
products were obtained. The best yield of trispyridinedi-
Experimental Section
yl-containing macroheterocycles (67% for 6a) using this
All reactions were carried out using standard Schlenk tech-
particular triplatinum template (3) was obtained for 2,6- niques under an inert atmosphere of dry, oxygen-free nitrogen
unless stated otherwise. All solvents were carefully dried and
distilled over appropriate drying agents prior to use. All stand-
ard reagents were purchased from Acros or Aldrich. First- and
second-generation Grubbsꢀ Ru catalysts and Schrock Mo cata-
lyst 11 were purchased from Strem. 2,6-Bis(5-hexenyloxy)pyr-
idine (1b)[13] 2,6-bis[(5-hexenyloxy)methyl]pyridine (1g),[13]
and 3[7a] were obtained according to literature procedures. 1H
(200 or 300 MHz) and 13C (50 or 75 MHz) NMR spectra were
recorded on a Varian AC200 or Inova 300 MHz spectrometer
at 258C, chemical shifts are in ppm referenced internally to re-
bisolefin substituted pyridines with olefin chains con-
taining 11 atoms (O, C) whereas for substrates with lon-
ger olefin chains (12 or 13 atoms) the yields of the corre-
sponding trispyridinediyl-containing macroheterocy-
cles decreased. The macroheterocycles (hosts) could
easily be detached from the macromolecular template
(guest) and quantitatively be reattached to the template
after hydrogenation of the double bonds of the macrocy-
cles. An X-ray crystal structure of host-guest complex 10
provided the definite proof for the perfect cyclic struc- sidual solvent signals. GC/MS analysis was performed using the
following conditions: column PE-17; 30 mꢁ0.32 mm2 ¼50 mm
ture of the macrocycle (9a) and for the efficient reat-
film thickness; gas chromatograph: Perkin-Elmer Autosystem
XL; mass spectrometer: Perkin-Elmer Turbomass. ES-MS
analysis was performed on a Micromass Quattro Ultima spec-
trometer. Preparative TLC was performed using Merck
tachment of macrocycle 9a (host) to template 3 (guest).
Comparison between the crystal structures of the tem-
plate precursor 3 and cationic complex 10 revealed
that attachment of the macrocycle to the trisplatinum
1.13895 plates, adsorbent – silica 60 F254, layer thickness 1 mm.
complex can cause ligand-induced conformational
changes in the complex (e.g., changes in dihedral angles)
in the solid phase and presumably also in solution.
This study shows that it is rather easy to create macro-
2,6-Bis(9-decenyloxy)pyridine (1a)
Sodium foil (0.74 g, 32 mmol) was added to a solution of 9-de-
cen-1-ol (5.0 g, 32 mmol) in THF (50 mL). The mixture was
stirred at reflux until all sodium had dissolved, after which
the THF was evaporated under reduced pressure. Dry DMF
(50 mL) and 2,6-dibromopyridine (3.79 g, 16 mmol) were add-
ed to the residue and the mixture was stirred at 958C overnight.
The DMF was evaporated and the residue was dissolved in wa-
ter (15 mL) and extracted with Et2O (3ꢁ50 mL). The organic
extracts were combined, dried (MgSO4), and filtered. After
evaporation of the solvent the crude product was flash distilled
under vacuum. Yield: 6.0 g (97%), colorless oil. 1H NMR
(200 MHz, CDCl3): d¼1.33 (m, 20H), 1.76 (m, J¼7.0 Hz,
4H), 2.05 (m, J¼7.0 Hz, 4H), 4.23 (t, J¼7.0 Hz, 4H), 4.97
(m, 4H), 5.82 (m, 2H), 6.25 (d, J¼7.7 Hz, 2H), 7.45 (t, J¼
7.7 Hz, 1H); 13C NMR (75 MHz, CDCl3): d¼26.3, 29.1, 29.2,
29.3, 29.5, 29.6, 33.9, 66.1, 101.1, 114.3, 139.3, 140.9, 163.0;
GC/MS: m/z¼388 (calcd. for C25H41NO2: 387.6); anal. calcd.
for C25H41NO2: C 77.47, H 10.66, N 3.61; found: C 77.39, H
10.60, N 3.54.
cycles making use of highly symmetric shape-persistent
macromolecular templates. We believe (and work de-
scribed in literature for single-metal templates supports
this)[9,12] that this methodology is not just restricted to
pyridines and the macromolecular template used in
our work. In earlier work, we have already reported
the preparation of various shape-persistent templates
with different dimensions and containing up to twelve
metal-sites for ligand coordination.[7] Thus combining
our shape-persistent macromolecular templates with a
variety of bisolefin-substituted ligands (e.g., also with
P- and S-coordination to the metal) can lead to a large
number of macroheterocycles containing many func-
tionalities, which can subsequently be used in host-guest
chemistry. As described above, the stilbene-functional-
ized macroheterocycle 6e underwent photo-isomeriza-
tion of the initially formed all-trans macrocycle to give
a mixture of the corresponding trans-trans-cis, trans-
cis-cis, and cis-cis-cis macrocycles. This may potentially
be used to reversibly switch the size and conformation
of the macrocyclic host and thus tailor the affinity for
the guests it can accommodate.[24] Furthermore, giant
crown-ether like macrocycles (such as 7d) could serve
as hosts for other guests. For example, (polyether)pyri-
dine macrocycle 7d is comprised of an 81-membered
ring containing as much as 24 oxygen and 3 (pyridine) ni-
trogen atoms, which could, for example, host lanthanide
2-[2-(Allyloxy)ethoxy]ethan-1-ol
Sodium (10 g, 0.43 mol) was dissolved in diethylene glycol
(100 mL, 112 g, 1.05 mol) at 1008C under stirring and allyl bro-
mide (35.4 mL, 48.4 g, 0.40 mol) was added dropwise under
stirring. The reaction mixture was stirred at 1008C for 2 h,
cooled to room temperature and filtered. The crude product
was distilled from the reaction mixture under vacuum (bp
61–808C/0.8 mm). For further purification the crude product
and actinide ions; due to its size, it may also be used for was redistilled under vacuum (bp 588C/0.7 mm). Yield: 49 g
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Alexey V. Chuchuryukin et al.
1
(84%), colorless oil. H NMR (200 MHz, CDCl3): d¼2.45 (t,
17.3 Hz, 2H), 5.90 (m, 2H), 6.31 (d, J¼7.9 Hz, 2H), 7.45 (t,
J¼7.9 Hz, 1H); 13C NMR (75 MHz, CDCl3): d¼65.2, 69.6,
69.8, 70.8, 70.8, 72.3, 101.9, 117.2, 134.9, 141.1, 162.4; anal.
calcd. for C23H37NO8: C 60.64, H 8.19, N 3.07; found: C 60.48,
H 8.12, N 3.14.
J¼6 Hz, 1H), 3.57–3.78 (m, 8H), 4.03 (dt, J¼5.9 Hz, 2H),
5.19 (dm, J¼10.3 Hz, 1H), 5.27 (dm, J¼17.2 Hz, 1H), 5.92
(m, 1H); 13C NMR (50 MHz, CDCl3): d¼61.8, 69.5, 70.5,
72.3, 72.6, 117.4, 134.5; anal. calcd. for C7H14O3: C 57.51, H
9.65; found: C 57.52, H, 9.60.
6-(4-Vinylphenyl)hexan-1-ol
2,6-Bis{2-[2-(allyloxy)ethoxy]ethoxy}pyridine (1c)
A 1 M solution of BH3-THF complex in THF (50 mL) was add-
ed dropwise under stirring to a colorless solution of 5-hexen-1-
ol (5 g, 50 mmol) in THF (50 mL) at ꢀ788C. The reaction mix-
ture was allowed to warm up under stirring to room tempera-
ture (evolution of hydrogen was observed) and stirred for
2 h. Subsequently, NaOH (8 g, 0.2 mol) in water (40 mL) was
added dropwise very slowly under slow stirring to the reaction
mixture. Vigorous evolution of hydrogen was observed. The re-
action mixture was stirred for 15 minutes and p-bromostyrene
(9.15 g, 50 mmol), Pd(PPh3)2Cl2 (0.7 g, 1 mmol), and PPh3
(0.13 g, 0.5 mmol) were added to the reaction mixture. The re-
action mixture was then stirred at reflux for 8 h, cooled to room
temperature and filtered. The solvent was evaporated under
vacuum, and Et2O (200 mL) and NaOH (10 g) in water
(40 mL) were added to the residue. The organic layer was sep-
arated, the aqueous layer was extracted with Et2O (3ꢁ50 mL),
and the combined organic extracts were dried over MgSO4, fil-
tered and evaporated. The thus obtained crude product was
flash distilled under vacuum. Yield 6.6 g (65%), colorless oil.
This compound should be stored in afreezer to avoid spontane-
2-[2-(Allyloxy)ethoxy]ethan-1-ol (10 g, 68 mmol) was dis-
solved in DMF (50 mL) and sodium hydride (1.7 g, 71 mmol)
was added. The reaction mixture was stirred for 30 min and
2,6-dibromopyridine (7.5 g, 32 mmol) was added. The reaction
mixture was stirred overnight at 1008C. The solvent was evapo-
rated under vacuum, the residue was dissolved in Et2O
(100 mL), filtered, and washed with water (3ꢁ50 mL). After
evaporating the Et2O under vacuum, the crude product was
flash distilled under vacuum (bp 1908C/0.5 mm). Yield: 9.8 g
1
(84%), colorless oil. H NMR (300 MHz, CDCl3): d¼3.62 (t,
J¼4.4 Hz, 4H), 3.71 (t, J¼4.4 Hz, 4H), 3.83 (t, J¼5.0 Hz,
4H), 4.02 (dt, J¼5.5 Hz, 4H), 4.42 (t, J¼5.0 Hz, 4H), 5.17
(dq, J¼10.4 Hz, 2H), 5.27 (dq, J¼17.1 Hz, 2H), 5.91 (m,
2H), 6.32 (d, J¼7.9 Hz, 2H), 7.45 (t, J¼7.9 Hz, 1H); 13C
NMR (75 MHz, CDCl3): d¼65.2, 69.6, 69.9, 70.9, 72.4, 101.9,
117.3, 134.9, 141.1, 162.4; anal. calcd. for C19H29NO6: C 62.11,
H 7.96, N 3.81; found: C 62.06, H 7.86, N 3.90.
1
2-{2-[2-(Allyloxy)ethoxy]ethoxy}ethan-1-ol
ous polymerization. H NMR (200 MHz, CDCl3): d¼1.22–
1.44 (m, 4H), 1.44–1.75 (m, 5H), 2.61 (t, J¼7.5 Hz, 2H), 3.63
(t, J¼6.4 Hz, 2H), 5.19 (d, J¼11.0 Hz, 1H), 5.71 (d, J¼
17.2 Hz, 1H), 6.70 (dd, J¼17.6 Hz, J¼10.6 Hz, 1H), 7.14 (d,
J¼8.2 Hz, 2H), 7.33 (d, J¼8.0 Hz, 2H); 13C NMR (50 MHz,
CDCl3): d¼25.8, 29.2, 31.5, 32.9, 35.8, 63.1, 112.9, 126.2,
128.6, 135.1, 136.7, 142.5; anal. calcd. for C14H20O: C 82.30, H
9.87; found: C 82.22, H 9.79.
Sodium (8 g, 0.35 mol) was dissolved in triethylene glycol
(100 mL, 112 g, 0.75 mol) at 1008C under stirring. The reaction
mixture was cooled to 508C and allyl bromide (30 mL, 42 g,
0.35 mol) was added dropwise under stirring and the reaction
mixture was stirred at 1008C for 2 h. The crude product was dis-
tilled from the reaction mixture under vacuum (bp 89–978C/
0.3 mm). For purification the crude product was redistilled un-
der vacuum (bp 91–928C/0.3 mm). Yield: 61 g (92%), colorless
oil. 1H NMR (300 MHz, CDCl3): d¼2.57 (s, 1H), 3.58 (m, 4H),
3.65 (m, 6H), 3.70 (t, J¼4.4 Hz, 2H), 4.00 (dq, J¼5.7 Hz, 2H),
5.16 (dm, J¼10.4 Hz, 1H), 5.25 (dm, J¼17.1 Hz, 1H), 5.89 (m,
1H); 13C NMR (50 MHz, CDCl3): d¼61.9, 69.5, 70.5, 70.7, 70.8,
72.4, 72.6, 117.3, 134.8; anal. calcd. for C9H18O4: C 56.82, H 9.54;
found: C 57.02, H 9.60.
2,6-Bis{[6-(4-vinylphenyl)hexyl]oxy}pyridine (1e)
6-(4-Vinylphenyl)hexan-1-ol (3.7 g, 18 mmol) was dissolved in
dry DMF (50 mL) and sodium hydride (0.48 g, 20 mmol) was
added. The reaction mixture was stirred for 30 min and 2,6-di-
bromopyridine (2.1 g, 9 mmol) was added. The reaction mix-
ture was stirred overnight at 1008C. The solvent was evaporat-
ed under vacuum, and the residue was dissolved in hexane
(100 mL), filtered, and washed with water (3ꢁ50 mL). The
solvent was evaporated under vacuum, and the crude product
was recrystallized from methanol. Four grams of the crude
product were dissolved in methanol (400 mL) at reflux and
crystallized overnight at ꢀ308C as a solvate with methanol.
The crystals were filtered quickly and allowed to melt at
room temperature. The resulting oil was dried under vacuum.
An additional amount of the product was obtained from the
mother liquor by secondary crystallization. Yield: 3.9 g
(91%), colorless oil. This compound should be stored in a freez-
er to avoid spontaneous polymerization. 1H NMR (300 MHz,
CDCl3): d¼1.36–1.56 (m, 8H), 1.65 (m, J¼7.5 Hz, 4H), 1.77
(m, J¼7.2 Hz, 4H), 2.62 (t, J¼7.6 Hz, 4H), 4.24 (t, J¼
6.5 Hz, 4H), 5.20 (d, J¼10.5 Hz, 2H), 5.71 (d, J¼17.4 Hz,
2H), 6.27 (d, J¼8.1 Hz, 2H), 6.71 (dd, J¼17.7 Hz, J¼
2,6-Bis(2-{2-[2-
(allyloxy)ethoxy]ethoxy}ethoxy)pyridine (1d)
2-{2-[2-(Allyloxy)ethoxy]ethoxy}ethan-1-ol (10 g, 53 mmol)
was dissolved in dry DMF (50 mL) and sodium hydride
(1.3 g, 54 mmol) was added. The reaction mixture was stirred
for 30 min and 2,6-dibromopyridine (6 g, 25 mmol) was added.
The reaction mixture was stirred overnight at 1008C. The DMF
was evaporated under vacuum, the residue was dissolved in
Et2O (100 mL), filtered and washed with water (3ꢁ50 mL).
Et2O was evaporated under vacuum, any volatile impurities
were removed under vacuum at 1708C/0.9 mm. Next, the crude
product was flash distilled under vacuum. Yield: 9.4 g (82%),
1
colorless oil. H NMR (300 MHz, CDCl3): d¼3.57–3.72 (m,
16H), 3.82 (t, J¼5.0 Hz, 4H), 4.01 (dt, J¼5.7 Hz, 4H), 4.41
(t, J¼4.9 Hz, 4H), 5.16 (dm, J¼10.4 Hz, 2H), 5.25 (dq, J¼
456
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Template-Directed Synthesis of Macroheterocycles by RCM
11.1 Hz, 2H), 7.14 (d, J¼8.4 Hz, 4H), 7.34 (d, J¼8.4 Hz, 4H)
7.47 (t, J¼8.0 Hz, 1H); 13C NMR (75 MHz, CDCl3): d¼26.1,
29.2, 31.5, 35.7, 66.1, 101.2, 113.0, 126.3, 128.7, 135.2, 136.9,
140.9, 142.6, 163.0; anal. calcd. for C33H41NO2: C 81.94, H
8.54, N 2.90; found: C 82.08, H 8.44, N 2.88.
12H), 2.99 (s, 36H), 4.33 (s, 12H), 4.42 (t, J¼6.6 Hz, 12H),
4.90 (m, 12H), 5.75 (m, 6H), 6.98 (d, J¼8.4 Hz, 6H), 7.42 (s,
6H), 7.82 (s, 3H), 8.15 (t, J¼8.0 Hz, 3H); 13C NMR (50 MHz,
acetone-d6): d¼26.8, 29.5, 29.8, 29.9, 30.0, 34.3, 54.3, 70.2,
77.6, 101.2, 114.2, 119.5, 124.1, 138.4, 139.6, 144.1, 144.7,
145.4, 145.8, 163.9; anal. calcd. for C117H180B3F12N9O6Pt3: C
52.94, H 6.84, N 4.75; found: C 53.10, H 6.76, N 4.70.
2,6-Bis[(9-decenyloxy)methyl]pyridine (1f)
To a solution of 9-decen-1-ol (5.0 g, 32 mmol) in THF (50 mL)
sodium foil (0.74 g, 32 mmol) was added. The mixture was stir-
red at reflux until all sodium was dissolved and 2,6-bis(chloro-
methyl)pyridinium chloride (2.26 g, 10.7 mmol) was added.
The mixture was stirred at reflux overnight and THF was
evaporated under vacuum. The residue was dissolved in water
(15 mL) and extracted with Et2O (3ꢁ50 mL). The organic ex-
tracts were combined, dried (MgSO4), and filtered. The sol-
vents and unreacted 9-decen-1-ol were removed under vac-
uum. The crude product was flash distilled at reduced pressure.
Cationic Complex 4b
Template precursor
3 (2.0 g, 1.5 mmol), AgBF4 (0.9 g,
4.6 mmol), and 2,6-bis(5-hexenyloxy)pyridine (1b) (1.24 g,
4.51 mmol) were mixed in dry dichloromethane (70 mL). The
resulting mixture was stirred overnight under the exclusion
of light, filtered over Celite and evaporated under vacuum.
Yield: 3.4 g (98%), glassy solid. 1H NMR (300 MHz, acetone-
d6): d¼1.84 (m, J¼7.2 Hz, 12H), 2.02 (m, J¼7.3 Hz, 12H),
2.18 (q, J¼7.0 Hz, 12H), 2.98 (s, 36H), 4.32 (s, 12H), 4.44 (t,
J¼6.3 Hz, 12H), 4.88 (dm, J¼10.4 Hz, 6H), 4.97 (dm, J¼
17.1 Hz, 6H), 5.80 (m, 6H), 6.98 (d, J¼8.2 Hz, 6H), 7.43 (s,
6H), 7.83 (s, 3H), 8.16 (t, J¼8.2 Hz, 3H); anal. calcd. for
C93H132B3F12N9O6Pt3: C 48.19, H 5.74, N 5.44; found: C 48.42,
H 5.85, N 5.37.
1
Yield: 4.3 g (97%), white solid. H NMR (200 MHz, CDCl3):
d¼1.30 (m, 20H), 1.64 (m, J¼7.0 Hz, 4H), 2.04 (m, J¼
7.0 Hz, 4H), 3.54 (t, J¼6.6 Hz, 4H), 4.60 (s, 4H), 4.97 (m,
4H), 5.82 (m, 2H), 7.34 (d, J¼7.7 Hz, 2H), 7.70 (t, J¼7.7 Hz,
1H); 13C NMR (75 MHz, CDCl3): d¼26.3, 29.0, 29.2, 29.5,
29.9, 33.9, 71.3, 73.9, 114.2, 119.8, 137.2, 139.3, 158.4. GC/MS:
m/z¼416 (calcd. for C27H45NO2: 415.7); anal. calcd. for
C27H45NO2: C 78.02, H 10.91, N 3.47; found: C 78.02, H 10.91,
N 3.62.
Cationic Complex 4c
Template precursor 3 (0.91 g, 0.68 mmol), AgBF4 (0.40 g,
2.05 mmol), and 2,6-bis{2-[2-(allyloxy)ethoxy]ethoxy}pyridine
(1c) (0.752 g, 2.05 mmol) were mixed in dry dichloromethane
(70 mL). The resulting mixture was stirred overnight under
the exclusion of light and centrifuged. A slow stream of H2S
was passed through the reaction mixture for 2 min to remove
complexed Agþ, the reaction mixture was refluxed overnight
and filtered over Celite. The solvent was evaporated under vac-
uum. Yield: 1.67 g (94%), glassy solid. 1H NMR (300 MHz, ace-
tone-d6): d¼3.00 (s, 36H), 3.55 (t, J¼4.7 Hz, 12H), 3.76 (t, J¼
4.7 Hz, 12H), 3.91 (dt, J¼5.5 Hz, J¼1.5 Hz, 12H), 4.04 (m,
12H), 4.32, (s, 12H), 4.56 (m, 12H), 5.09 (dq, J¼10.4 Hz, J¼
1.6 Hz, 6H), 5.21 (dq, J¼17.4 Hz, J¼1.8 Hz, 6H), 5.85 (m,
6H), 7.02 (d, J¼8.2 Hz, 6H), 7.39 (s, 6H), 7.79 (s, 3H), 8.18 (t,
J¼8.2 Hz, 3H); 13C NMR (75 MHz, acetone-d6): d¼54.4,
69.8, 69.9, 70.3, 71.2, 72.3, 77.5, 101.4, 116.6, 119.4, 124.1,
136.1, 138.4, 144.3, 144.5, 145.9 (2C), 163.8; anal. calcd. for
C99H144B3F12N9O18Pt3: C 45.84, H 5.60, N 4.86; found: C 45.71,
H 5.70, N 4.84.
Bis(9-decenyl) 3,5-Pyridinedicarboxylate (2a)
3,5-Pyridinedicarboxylic acid (3.2 g, 19.12 mmol) was suspend-
ed in SOCl2 (20 mL, 270 mmol) and stirred at reflux overnight.
Subsequently, the excess SOCl2 was evaporated under vacuum
and the remaining white solid was dissolved in CH2Cl2 (50 mL).
9-Decane-1-ol (6.0 g, 38.4 mmol) was added to the solution and
the reaction mixture was stirred at reflux for 3 h. The volatiles
were removed under vacuum, the residue was suspended in
Et2O (50 mL) and sodium hydroxide (1.6 g, 40 mmol) in water
(10 mL) was added. The reaction mixture was stirred for
15 min, the organic layer was separated, dried over MgSO4,
and filtered. The Et2O was removed in vacuum and the residue
was flash distilled giving a light yellow oil. Yield: 7.8 g (92%).
1H NMR (200 MHz, CDCl3): d¼1.31 (m, 20H), 1.78 (m, J¼
7.0 Hz, 4H), 2.03 (q, J¼6.6 Hz, 4H), 4.37 (t, J¼6.6 Hz, 4H),
4.97 (m, 4H), 5.79 (m, 2H), 8.84 (t, J¼2.2 Hz, 1H), 9.34 (d,
J¼2.2 Hz, 2H); 13C NMR (50 MHz, CDCl3): d¼26.1, 28.8,
29.0, 29.2, 29.3, 29.5, 33.9, 66.1, 114.3, 126.4, 138.1, 139.2,
154.2, 164.6. GC/MS: m/z¼444 (calcd. for C27H41NO4: 443.6);
anal. calcd. for C27H41NO4: C 73.10, H 9.32, N 3.16; found: C
72.97, H 9.35, N 3.24.
Cationic Complex 4d
Template precursor 3 (1.50 g, 1.12 mmol), AgBF4 (0.66 g,
3.38 mmol), and 2,6-bis(2-{2-[2-(allyloxy)ethoxy]ethoxy}
ethoxy)pyridine (1d) (1.53 g, 3.36 mmol) were mixed in dry di-
chloromethane (75 mL). The resulting mixture was stirred
overnight under the exclusion of light and centrifuged. A
slow stream of H2S was passed through the reaction mixture
for 2 min to remove complexed Agþ, the reaction mixture
was subsequently refluxed overnight, and filtered over Celite.
The solvent was evaporated under vacuum. Yield: 3.00 g
(94%), glassy solid. 1H NMR (300 MHz, acetone-d6): d¼2.99
(s, 36H), 3.49 (m, 24H), 3.57 (t, J¼4.8 Hz, 12H), 3.73 (t, J¼
4.9 Hz, 12H), 3.93 (d, J¼5.7 Hz, 12H), 4.02 (m, 12H), 4.31,
Cationic Complex 4a
Template precursor 3 (1.36 g, 1.02 mmol), AgBF4 (0.6 g,
3.07 mmol), and 2,6-bis(9-decenyloxy)pyridine (1a) (1.19 g,
3.07 mmol) were mixed in dry dichloromethane (70 mL). The
resulting mixture was stirred overnight under exclusion of
light, filtered over Celite and evaporated under vacuum. Yield:
2.67 g (99%), glassy solid. 1H NMR (200 MHz, acetone-d6): d¼
1.27 (m, 60H), 1.76 (m, J¼7.2 Hz, 12H), 1.97 (q, J¼7.2 Hz,
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Alexey V. Chuchuryukin et al.
(s, 12H), 4.54 (m, 12H), 5.08 (dq, J¼10.5 Hz, J¼1.5 Hz, 6H),
5.21 (dq, J¼16.8 Hz, J¼2.1 Hz, 6H), 5.85 (m, 6H), 7.00 (d,
J¼8.1 Hz, 6H), 7.39 (s, 6H), 7.81 (s, 3H), 8.16 (t, J¼8.3 Hz,
3H); 13C NMR (75 MHz, acetone-d6): d¼54.5, 69.9,
70.0, 70.3, 71.1, 71.3, 72.3, 77.6, 101.4, 116.4, 119.5, 124.1,
136.3, 138.4, 144.4, 144.7, 145.9(2C), 163.9; anal. calcd. for
C111H168B3F12N9O24Pt3: C 46.64, H 5.92, N 4.41; found: C
46.54, H 5.88, N, 4.34.
(50 MHz, acetone-d6): d¼26.2, 29.8, 34.1, 54.6, 72.1, 73.6,
77.9, 114.9, 119.8, 123.4, 124.4, 126.6, 139.2, 139.4, 140.7,
144.0, 145.7, 160.1; anal. calcd. for C99H144B3F12N9O6Pt3: C
49.50, H 6.04, N 5.25; found: C 49.59, H 6.01; N 5.20.
Cationic Complex 4h
Template precursor 3 (1.30 g, 0.97 mmol), AgBF4 (0.57 g,
2.92 mmol), and bis(9-decenyl) 2,6-pyridinedicarboxylate
(2a) (1.30 g, 2.93 mmol) were mixed in dry dichloromethane
(70 mL). The reaction mixture was stirred overnight under
the exclusion of light and filtered over Celite. The dichlorome-
thane was evaporated under vacuum. Yield: 2.62 g (95%),
glassy solid. 1H NMR (300 MHz, acetone-d6): d¼1.36 (m,
60H), 1.85 (m, J¼7.0 Hz, 12H), 2.04 (q, J¼6.6 Hz, 12H),
3.00 (s, 36H), 4.46 (m, 24H), 4.96 (m, 12H), 5.81 (m, 6H), 7.47
(s, 6H), 7.83 (s, 3H), 9.01 (t, J¼1.8 Hz, 3H), 9.85 (d, J¼
1.8 Hz, 6H); 13C NMR (75 MHz, acetone-d6): d¼26.6, 29.2,
29.6, 29.7, 29.9, 30.1, 34.4, 54.1, 67.2, 77.8, 114.5, 119.7, 124.6,
130.89, 139.4, 139.7, 139.9, 142.8, 144.0, 146.3, 156.0, 163.7;
anal. calcd. for C123H180B3F12N9O12Pt3: C 52.34, H 6.43, N
4.47; found: C 52.45, H 6.51, N 4.38.
Cationic Complex 4e
Template precursor 3 (1.0 g, 0.75 mmol), AgBF4 (0.44 g,
2.26 mmol), and 2,6-bis{[6-(4-vinylphenyl)hexyl]oxy}pyridine
(1e) (1.1 g, 2.27 mmol) were mixed in dry dichloromethane
(70 mL). The resulting mixture was stirred overnight under
the exclusion of light, filtered over Celite, and evaporated un-
der vacuum. Yield: 2.19 g (99%), glassy solid. 1H NMR
(300 MHz, acetone-d6): d¼1.43 (m, J¼7.1 Hz, 12H), 1.57
(m, J¼7.4 Hz, 12H), 1.78 (m, J¼7.5 Hz, 12H), 1.96 (m, J¼
7.2 Hz, 12H), 2.50 (t, J¼7.4 Hz, 12H), 2.93 (s, 36H), 4.25, (s,
12H), 4.38 (t, J¼6.0 Hz, 12H), 5.10 (d, J¼11.1 Hz, 6H), 5.64
(d, J¼17.4 Hz, 6H), 6.61 (dd, J1 ¼17.7 Hz, J2 ¼10.8 Hz, 6H),
6.94 (d, J¼8.4 Hz, 6H), 7.02 (d, J¼8.1 Hz, 12H), 7.25 (d, J¼
7.8 Hz, 12H), 7.37 (s, 6H), 7.83 (s, 3H), 8.13 (t, J¼8.3 Hz,
3H); 13C NMR (75 MHz, acetone-d6): d¼26.8, 29.6, 29.8,
32.0, 35.9, 54.4, 70.3, 77.7, 101.3, 112.9, 119.7, 124.4, 127.0,
129.3, 135.6, 137.6, 137.5, 143.1, 144.2, 144.7, 145.5, 145.9,
163.9; anal. calcd. for C141H180B3F12N9O6Pt3: C 57.55, H 6.17,
N 4.28; found: C 57.38; H 6.19; N 4.18.
Macrocycle 6a
Cationic complex 4a (2.6 g, 0.98 mmol) and Grubbsꢀ catalyst
¼
Cl2(Cy3P)2Ru CHPh (120 mg, 0.147 mmol) were dissolved in
dichloromethane (1000 mL). The mixture was refluxed over-
night under stirring, cooled to room temperature and concen-
trated under vacuum to 200 mL. Saturated aqueous NaCl
(50 mL) was added and the mixture was stirred overnight.
The organic layer was separated, dried (MgSO4), filtered,
and the solvent was evaporated. The RCM products were ex-
tracted with hexane, and separated by preparative TLC, elu-
ent: hexane/dichloromethane¼2/1. Yield: 0.71 g (67%), color-
less oil, which solidifies at room temperature. 1H NMR
(200 MHz, CDCl3): d¼1.30 (m, 60H), 1.75 (m, J¼6.8 Hz,
12H), 1.97 (m, 12H), 4.23 (t, J¼6.8 Hz, 12H), 5.37 (m, 6H),
6.24 (d, J¼8.0 Hz, 6H), 7.44 (t, J¼7.9 Hz, 3H); 13C NMR
(75 MHz, CDCl3): d¼26.2, 29.2, 29.3, 29.5, 29.6, 29.7,
32.7, 66.1, 101.2, 130.5, 140.9, 163.0; ES-MS: m/z¼1079.0
[MþH]þ (calcd. for C69H111N3O6: 1078.64); anal. calcd. for
C69H111N3O6: C 76.83, H 10.37, N 3.90; found: C 76.68, H
10.47, N 3.83.
Cationic Complex 4f
Template precursor 3 (1.64 g, 1.22 mmol), AgBF4 (0.72 g,
3.67 mmol), and 2,6-bis[(9-decenyloxy)methyl]pyridine (1f)
(1.53 g, 3.68 mmol) were mixed in dry dichloromethane
(70 mL). The mixture was stirred overnight under the exclu-
sion of light, filtered over Celite and evaporated under vac-
uum. Yield: 3.30 g (99%), glassy solid. 1H NMR (200 MHz, ace-
tone-d6): d¼1.33 (m, 60H), 1.71 (m, J¼6.4 Hz, 12H), 2.03 (q,
J¼6.6 Hz, 12H), 2.96 (s, 36H), 3.82 (t, J¼6.4 Hz, 12H), 4.46
(s, 12H), 4.96 (m, 12H), 5.84 (m, 18H), 7.51 (s, 6H), 7.88
(s, 3H), 7.94 (d, J¼7.7 Hz, 6H), 8.30 (t, J¼7.7 Hz, 3H);
13C NMR (50 MHz, acetone-d6): d¼26.9, 29.6, 29.7, 30.1,
30.4, 34.4, 54.5, 72.3, 73.6, 77.9, 114.5, 119.8, 124.4, 126.6,
139.1, 139.7, 140.6, 143.9, 145.7, 158.7, 160.1; anal. calcd. for
C123H192B3F12N9O6Pt3: C 53.95, H 7.07, N 4.60; found: C 53.86,
H 6.94, N 4.48.
To recycle the template precursor 3 – insoluble in hexane –
the residue was washed with ethanol (3ꢁ30 mL), dissolved
in chloroform (200 mL) and filtered through silica. The sol-
vents were removed by evaporation under vacuum, and 3
was quantitatively recovered.
Cationic Complex 4g
Template precursor
3 (2.0 g, 1.5 mmol), AgBF4 (0.9 g,
General Procedure for Extraction of Products in
Preparative TLC
4.6 mmol), and 2,6-bis[(5-hexenyloxy)methyl]pyridine (1g)
(1.37 g, 4.5 mmol) were mixed in dry dichloromethane
(70 mL). The mixture was stirred overnight under the exclu-
sion of light, filtered over Celite and evaporated under vac-
uum. Yield: 3.53 g (98%), glassy solid. 1H NMR (200 MHz, ace-
tone-d6): d¼1.55 (m, 12H), 1.73 (m, 12H), 2.10 (q, J¼6.6 Hz,
12H), 2.96 (s, 36H), 3.83 (t, J¼6.2 Hz, 12H), 4.47 (s, 12H),
4.98 (m, 12H), 5.86 (m, 18H), 7.51 (s, 6H), 7.87 (s, 3H), 7.95
(d, J¼7.7 Hz, 6H), 8.31 (t, J¼7.9 Hz, 3H); 13C NMR
After the preparative TLC was eluted, the silica from the
individual bands, identified under UV light (l¼254 nm),
were scrapped off the plate, collected in a beaker and stirred
for 1 hour in dichloromethane/MeOH¼7/3 (60 mL). The silica
was vacuum filtered and washed with dichloromethane/
MeOH¼7/3 (1ꢁ20 mL) and the solvent was removed under
vacuum. This procedure was repeated until a constant weight
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Template-Directed Synthesis of Macroheterocycles by RCM
of product was obtained (usually twice more). To extract the
product from residual silica, the residues were washed with di-
chloromethane (3ꢁ50 mL) and gravity filtered. The filtrate
was removed and the product was dried under vacuum to ob-
tain the macrocycles.
NaCl (40 mL) was added and the mixture was stirred over-
night. The organic layer was separated, dried (MgSO4), fil-
tered, and the solvents were evaporated. The RCM products
were extracted with hexane, and separated by preparative
TLC, eluent: dichloromethane/acetone¼15/1. Yield: 0.37 g
(44%), colorless oil, which solidifies at room temperature. 1H
NMR (200 MHz, CDCl3): d¼1.28 (m, 60H), 1.64 (m, J¼
6.8 Hz, 12H), 1.97 (m, 12H), 3.54 (t, J¼6.4 Hz, 12H), 4.60 (s,
12H), 5.37 (m, 6H), 7.33 (d, J¼7.7 Hz, 6H), 7.69 (t, J¼
7.7 Hz, 3H); 13C NMR (75 MHz, CDCl3): d¼26.2, 29.1, 29.5,
29.5, 29.7, 29.8, 32.6, 71.3, 73.8, 119.8, 130.5, 137.2, 158.4; ES-
MS: m/z¼1163.0 [MþH]þ (calcd. for C75H123N3O6: 1162.8);
anal. calcd. for C75H123N3O6: C 77.47, H 10.66, N 3.61; found:
C 77.42, H 10.73, N 3.54.
Macrocycle 6d
Cationic complex 4d (2.70 g, 0.94 mmol) and first-generation
¼
Grubbsꢀ catalyst Cl2(Cy3P)2Ru CHPh (117 mg, 0.142 mmol)
were dissolved in dichloromethane (1000 mL). The mixture
was refluxed for 16 h under stirring and cooled to room temper-
ature. Saturated aqueous NaCl (40 mL) was added and the
mixture was stirred overnight. The organic layer was separat-
ed, dried (MgSO4), filtered, and the solvent was evaporated.
The RCM products were extracted with Et2O and separated
by preparative TLC, eluent: dichloromethane/acetone¼4/1.
Yield: 0.5 g (41%), colorless oil. 1H NMR (300 MHz, CDCl3):
d¼3.54–3.73 (m, 48H), 3.82 (t, J¼5.5 Hz, 12H), 4.00 (dd,
J¼3.0 Hz, J¼1.5 Hz, 10H), 4.08 (d, J¼4.8 Hz, 2H), 4.41 (t,
J¼5.1 Hz, 12H), 5.71 (t, J¼4.5 Hz, 1H), 5.79 (m, J¼1.4 Hz,
5H), 6.31 (d, J¼8.1 Hz, 6H), 7.46 (t, J¼7.8 Hz, 3H); 13C
NMR (75 MHz, CDCl3): d¼65.2, 69.6, 69.8, 70.8, 71.3, 101.9,
129.6, 141.1, 162.4; ES-MS: m/z¼1282.63 [MþH]þ (calcd.
for C63H99N3O24: 1281.66); anal. calcd. for C63H99N3O24: C
59.00, H 7.78, N 3.28; found: C 58.87, H 7.73, N 3.34.
Macrocycle 7a
Macrocycle 6a (500 mg, 0.463 mmol) was dissolved in dichloro-
methane (15 mL) and the palladium catalyst (50 mg, 10% Pd
on active coal) was added. The mixture was stirred under an at-
mosphere of hydrogen for 4 h at room temperature and fil-
tered. The dichloromethane was evaporated under vacuum.
Yield: 500 mg (99%), white solid. 1H NMR (200 MHz,
CDCl3): d¼1.25 (m, 84H), 1.75 (m, J¼6.8 Hz, 12H), 4.24 (t,
J¼6.8 Hz, 12H), 6.24 (d, J¼7.7 Hz, 6H), 7.44 (t, J¼7.7 Hz,
3H); 13C NMR (75 MHz, CDCl3): d¼26.2, 29.3, 29.5, 29.7,
29.8, 66.1, 101.2, 140.9, 163.0; ES-MS: m/z¼1084.9 [MþH]þ
(calcd. for C69H111N3O6: 1084.7); anal. calcd. for C69H117N3O6:
C 76.40, H 10.87, N 3.87; found: C 76.30, H 10.81, N 3.79.
Macrocycle 6e
Cationic complex 4e (2.15 g, 0.73 mmol) and second-genera-
¼
tion Grubbsꢀ catalyst Cl2(Cy3P)(IMes)Ru CHPh (279 mg,
Macrocycle 7d
0.33 mmol) were subsequently dissolved in dichloromethane
(1000 mL). The mixture was refluxed for 48 h under stirring,
cooled to room temperature and concentrated under vacuum
to 200 mL. Saturated aqueous NaCl (50 mL) was added and
the mixture was stirred overnight. The organic layer was sepa-
rated, dried (MgSO4), and the solvent was evaporated. The
RCM products were extracted with toluene, and separated
by preparative TLC, eluent: toluene/hexane¼3/1. After chro-
matographic separation the product was recrystallized from
acetone (dissolved at reflux and crystallized at ꢀ308C) and
dried under vacuum at 1008C. Yield 0.60 g (60%), colorless
oil solidifying at room temperature. 1H NMR (300 MHz,
CDCl3): d¼1.30–1.46 (m, 24H), 1.66 (m, J¼7.1 Hz, 12H),
1.77 (m, J¼7.1 Hz, 12H), 2.62 (t, J¼7.5 Hz, 12H), 4.24 (t,
J¼6.6 Hz, 12H), 6.26 (d, J¼8.1 Hz, 6H), 7.05 (s, 6H), 7.25 (d,
J¼8.4 Hz, 12H), 7.41 (d, J¼8.1 Hz, 12H), 7.46 (t, J¼8.0 Hz,
3H); 13C NMR (75 MHz, CDCl3): d¼26.0, 28.9, 29.1, 31.4,
35.6, 66.0, 101.2, 126.5, 127.8, 128.9, 135.1, 140.9, 142.2, 163.0;
ES-MS: m/z¼1367.1 [MþH]þ (calcd. for C93H111N3O6:
1366.86); anal. calcd. for C93H111N3O6: C 81.72, H 8.19; found:
C 81.65, H 8.36.
Macrocycle 6d (450 mg, 0.35 mmol) was dissolved in methanol
(20 mL) and palladium on active coal (10%, 50 mg) was added.
The reaction mixture was stirred under hydrogen for 4 h and
filtered. The solvent was evaporated under vacuum. Yield:
450 mg (99%), colorless oil. 1H NMR (300 MHz, CDCl3): d¼
1.62 (m, J¼2.9 Hz, 12H), 3.45 (m, J¼3.5 Hz, 12H), 3.54–
3.75 (m, 48H), 3.82 (t, J¼5.1 Hz, 12H), 4.41 (t, J¼5.0 Hz,
12H), 6.31 (d, J¼7.8 Hz, 6H), 7.45 (t, J¼8.0 Hz, 3H); 13C
NMR (75 MHz, CDCl3): d¼26.4, 65.2, 69.8, 70.2, 70.8,
70.9, 71.2, 101.9, 141.1, 162.4. ES-MS: m/z¼1288.75
[MþH]þ (calcd. for C93H117N3O6: 1287.71); anal. calcd. for
C63H105N3O24: C 58.72, H 8.21, N 3.26; found: C 58.57, H 8.16,
N 3.31.
Macrocycle 7e
Macrocycle 6e (70 mg, 0.051 mmol) was dissolved in THF
(10 mL) and palladium on active coal (10%, 50 mg) was added.
The reaction mixture was stirred under an atmosphere of hy-
drogen for five days and filtered. The solvent was evaporated
under vacuum. Yield: 70 mg (99%), colorless oil, which solidi-
1
fies at room temperature. H NMR (300 MHz, CDCl3): d¼
Macrocycle 6f
1.30–1.46 (m, 24H), 1.63 (m, J¼7.1 Hz, 12H), 1.76 (m, J¼
7.2 Hz, 12H), 2.59 (t, J¼7.7 Hz, 12H), 2.86 (s, 12H), 4.24 (t,
J¼6.8 Hz, 12H), 6.25 (d, J¼8.1 Hz, 6H), 7.08 (s, 24H), 7.45
(t, J¼8.0 Hz, 3H); 13C NMR (75 MHz, CDCl3): d¼26.1, 29.1,
29.2, 31.6, 35.6, 37.7, 66.0, 101.2, 128.44, 128.47, 139.3, 140.3,
140.9, 163.0; ES-MS: m/z¼1372.89 [MþH]þ (calcd. for
Cationic complex 4f (2.0 g, 0.73 mmol) and Grubbsꢀ catalyst
¼
Cl2(Cy3P)2Ru CHPh (90 mg, 0.109 mmol) were subsequently
dissolved in dichloromethane (750 mL). The mixture was re-
fluxed overnight under stirring, cooled to room temperature
and concentrated under vacuum to 150 mL. Saturated aqueous
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DEDICATED CLUSTER
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C93H117N3O6: 1371.89); anal. calcd. for C93H117N3O6: C 81.36, H
8.59, N 3.06; found: C 81.25, H 8.46, N 3.14.
Cationic Complex 9d
Template precursor 3 (326 mg, 0.244 mmol), AgBF4 (143 mg,
0.733 mmol), and macrocycle 7d (315 mg, 0.244 mmol) were
mixed in dichloromethane (10 mL). The mixture was stirred
overnight under the exclusion of light and filtered. The solvent
was evaporated under vacuum. The crude product was dis-
solved in acetone (10 mL), filtered and evaporated under vac-
Macrocycle 7f
Macrocycle 6f (340 mg, 0.292 mmol) was dissolved in dichloro-
methane (15 mL) and palladium catalyst (34 mg, 10% Pd on
active coal) was added. The resulting mixture was stirred under
an atmosphere of hydrogen for 4 h at room temperature and
filtered after which the dichloromethane was evaporated un-
der vacuum. The product was separated by preparative TLC,
eluent: dichloromethane/acetone¼15/1. Yield: 266 mg
1
uum. Yield: 665 mg (98%), white solid. H NMR (300 MHz,
acetone-d6): d¼1.47 (m, J¼3 Hz, 12H), 3.04 (s, 36H), 3.30
(m, 12H), 3.36 (m, 12H), 3.44 (m, 12H), 3.59 (m, 12H), 3.76
(m, 12H), 4.03 (m, 12H), 4.38 (s, 12H), 4.54 (m, 12H), 7.01 (d,
J¼8.1 Hz, 6H), 7.45 (s, 6H), 7.87 (s, 3H), 8.18 (t, J¼8.3 Hz,
3H); 13C NMR (75 MHz, acetone-d6): d¼27.2, 54.9, 69.9,
70.2, 70.6, 71.22, 71.29, 71.36, 71.44, 77.9, 101.5, 119.7, 124.3,
1
(78%), white solid. H NMR (200 MHz, CDCl3): d¼1.27 (m,
84H), 1.63 (m, J¼6.8 Hz, 12H), 3.53 (t, J¼6.4 Hz, 12H), 4.60
(s, 12H), 7.33 (d, J¼7.7 Hz, 6H), 7.69 (t, J¼7.7 Hz, 3H); 13C
NMR (75 MHz, CDCl3): d¼26.2, 29.5, 29.6, 29.7, 29.8, 71.3,
73.9, 119.9, 137.2, 158.4; ES-MS: m/z¼1169.2 [MþH]þ (calcd.
for C75H129N3O6: 1168.8); anal. calcd. for C75H129N3O6: C 77.07,
H 11.12, N 3.60; found: C 77.05, H 11.21, N 3.49.
138.9, 142.9, 144.2, 146.2, 146.7, 163.9; ES-MS: m/z¼839.7
3þ
(calcd. for C105H162N9O24Pt3
: 839.7); anal. calcd. for
C105H162B3F12N9O24Pt3: C 45.36, H 5.87, N 4.53; found: C
45.28, H 5.90, N 4.69.
Cationic Complex 9f
Macrocycle 8
Template precursor 3 (68.1 mg, 0.051 mmol), AgBF4 (30 mg,
0.154 mmol) and macrocycle 7f (70 mg, 0.051 mmol) were
mixed in dichloromethane (10 mL). The mixture was stirred
overnight under the exclusion of light and filtered. The solvent
was evaporated under vacuum. The crude product was dis-
solved in acetone (10 mL), filtered, and the acetone was evapo-
Cationic complex 4 h (2.6 g, 0.92 mmol) was dissolved in di-
chloromethane (1000 mL), and Cl2(Cy3P)2Ru CHPh
¼
(284 mg, 0.345 mmol) was added. The reaction mixture was
stirred at reflux for 48 h, cooled to room temperature, and
the solution was concentrated to 1/3 of the previous volume.
A saturated aqueous solution of NaCl (50 mL) was added
and the reaction mixture was stirred overnight. The organic
layer was separated, dried over MgSO4, and evaporated. The
pyridine derivatives were extracted from the solid residue
with hexane and further separated by preparative TLC. To re-
cover the template precursor 3, the residue – after extraction
with hexane – was washed with ethanol, dissolved in chloro-
form and filtered through silica. The chloroform was evaporat-
ed under vacuum to afford 3. Yield: 0.81 g (70%), light yellow
1
rated under vacuum. Yield: 145 mg (99%), white solid. H
NMR (300 MHz, acetone-d6): d¼1.40 (m, 12H), 1.58 (m, J¼
7.3 Hz, 12H), 1.91 (m, 24H), 2.49 (t, J¼7.4 Hz, 12H), 2.67 (s,
12H), 2.91 (s, 36H), 4.23 (s, 12H), 4.41 (s, 12H), 6.71–6.86 (m,
24H), 6.94 (d, J¼8.4 Hz, 6H), 7.22 (s, 6H), 7.77 (s, 3H), 8.14
(t, J¼8.1 Hz, 3H); 13C NMR (75 MHz, acetone-d6): d¼27.2,
31.8, 35.3, 38.0, 54.4, 70.4, 77.8, 101.3, 119.9, 124.8, 128.9,
129.2, 138.8, 139.7, 140.3, 144.4, 144.7, 145.4, 146.0, 164.1; ES-
MS: m/z¼868.2 (calcd. for C135H174N9O6Pt33þ: 868.1); anal.
calcd. for C135H174B3F12N9O6Pt3: C 56.60, H 6.12, N 4.40; found:
C 56.47, H 6.06, N 4.29.
1
oil. H NMR (200 MHz, CDCl3): d¼1.31 (m, 20H), 1.78 (m,
J¼6.8 Hz, 4H), 1.97 (m, 4H), 4.40 (m, 4H), 5.37 (m, 2H), 8.77
(d, J¼2.0 Hz, 2H), 9.38 (t, J¼2.0 Hz, 1H); GC/MS: m/z¼
416 (calcd. for C25H37NO4: 415.6); anal. calcd. for C25H37NO4:
C 72.26, H 8.97, N 3.37; found: C 72.20, H 9.08, N, 3.45.
Isomerized Pyridine 12
Cationic 4a (0.382 g, 0.14 mmol) was dissolved in dry dichloro-
methane (100 mL) and Schrock catalyst 11 (0.016 g,
0.02 mmol) was dissolved in dry dichloromethane (10 mL) in
a separate Schlenk tube. The solution of 11 was transferred
via cannula into the solution of 4a and the flask rinsed with di-
chloromethane (2ꢁ1 mL). The reaction mixture was heated to
reflux for 16 hours after which the solvent volume was reduced
to 40 mL and NaCl (1.30 g) in water (40 mL) was added and the
biphasic mixture was stirred in air overnight. The layers were
separated and the aqueous layer washed with dichloromethane
(3ꢁ40 mL). The combined organics were dried over MgSO4,
filtered and the solvent removed under vacuum. The product
was extracted with hexanes (3ꢁ15 mL) and the volatiles re-
moved. The product was purified by preparative TLC, eluent:
hexanes/dichloromethane¼7/3. Yield 0.104 g (67%). 1H NMR
(CDCl3, 300 MHz): d¼0.86–0.98 (overlapping t, 3H,
Cationic Complex 9a
Template precursor 3 (122 mg, 0.092 mmol), AgBF4 (54 mg,
0.276 mmol), and macrocycle 7a (100 mg, 0.092 mmol) were
mixed in dichloromethane (20 mL). The mixture was stirred
overnight under the exclusion of light and filtered. The solvent
was evaporated under vacuum. The crude product was dis-
solved in acetone (10 mL), and filtered, and the solvent was
evaporated under vacuum. Yield: 226 mg (95%), white solid.
1H NMR (200 MHz, acetone-d6): d¼1.04 (m, 60H), 1.45 (m,
12H), 1.92 (m, 24H), 2.98 (s, 36H), 4.31 (s, 12H), 4.41 (m,
12H), 6.95 (d, J¼8.0 Hz, 6H), 7.39 (s, 6H), 7.82 (s, 3H), 8.14
(t, J¼8.2 Hz, 3H); 13C NMR (50 MHz, acetone-d6): d¼27.1,
29.6, 29.9, 30.0, 30.1, 30.2, 30.5, 54.4, 70.5, 77.8, 98.0, 101.3,
119.5, 124.2, 138.4, 144.2, 144.8, 145.4, 145.9, 164.0; ES-MS:
m/z¼771.77 (calcd. for C111H174N9O6Pt33þ: 771.75); anal. calcd.
for C111H174B3F12N9O6Pt3: C 51.75, H 6.81, N 4.89; found: C
51.60, H 6.74, N, 4.82.
CH2CH3), 1.26–1.44 (br m, 10H, CH2CH2CH2), 1.59 (d, 1H,
3
¼
JH,H ¼5.7 Hz, CHCH3) 1.64 (m, 3H), 1.76 (overlapping m,
¼
5H, OCH2CH2 and CHCH2CH2), 1.97–2.04 (br m, 6H,
460
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asc.wiley-vch.de
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DEDICATED CLUSTER
FULL PAPERS
Template-Directed Synthesis of Macroheterocycles by RCM
3
¼
CHCH2), 4.23 (t, 4H, JH,H ¼6.8 Hz, OCH2), 4.95 (m, 0.5H,
76.7954(3)8, V¼8400.66(10) ꢃ3, Z¼2, 1calcd. ¼1.294 g·cmꢀ3
;
¼
¼
terminal CH2), 5.35–5.44 (br m, 3.6H, internal CH), 5.82
2219 refined parameters, 3563 restraints, R(F) [I>2s (I)]¼
0.0517, wR(F2)¼0.1357, S¼1.04, Drmax/Drmin ¼1.92/ꢀ1.49
e ꢃꢀ3. CCDC 185367 contains the supplementary crystallo-
graphic data for this paper, see above for access.
3
¼
(m, 0.25H, terminal CH), 6.25 (d, 2H, JH,H ¼7.8 Hz, m-
ArH), 7.45 (t, 1H, JH,H ¼7.8 Hz, p-ArH); 13C NMR (CDCl3,
3
75.5 MHz): d¼13.8, 18.1 (CH3), 25.8, 26.1, 26.3, (CH2), 28.8–
¼
29.8 (10 signals, OCH2CH2, CHCH2CH2), 32.4–32.7 (5 sig-
The asymmetric unit in 10 contains one independent cation-
ic complex and three independent tetraphenylborate anions, as
well as disordered solvent molecules (acetone/Et2O) that could
not be resolved in the difference Fourier map. The solvent con-
tribution was treated using PLATON/SQUEEZE (58 e/unit
cell).[26a] The three macrocycle bridges of the cation are each
disordered over two sets of atomic positions [with refined occu-
pancies of 0.536(7):0.464, 0.63(1):0.37, and 0.630(7):0.370, re-
spectively]. The NCN-pincer moiety coordinated to Pt(2) is
also disordered over two conformations at different twist an-
gles relative to the central benzene ring [with refined occupan-
cies of 0.655(6):0.345]. All non-hydrogen atoms were refined
with anisotropic displacement parameters, but the displace-
ment parameters of the disordered atoms were restrained to
be approximately isotropic. Hydrogen atoms were constrained
to idealized geometries and allowed to ride on their carrier
atoms with an isotropic displacement parameter related to
the equivalent displacement parameter of their carrier atoms.
¼
nals, CHCH2), 66.2 (OCH2), 101.1 (m-CH), 114.3 (terminal
CH2), 129.4–132.2 (10 signals, internal CH), 139.4 (terminal
CH), 140.9 (p-CH), 163.1 (OC); GC/MS: m/z 388.
¼
¼
¼
¼
Crystal Structure Determination of Template
Precursor 3
The intensity data for a single crystal (0.09ꢁ0.24ꢁ0.27 mm) of
3 were collected using graphite-monochromated Mo-Ka radi-
ation, on a Nonius KappaCCD diffractometer at 150 K. An em-
pirical absorption correction was applied using PLATON/DE-
LABS (0.276–0.601 transmission range).[26a] The structure was
solved by automated Patterson methods using DIRDIF99,[27]
and refined on F2 using SHELXL97.[28] The crystal structure
contains voids (5922.9 ꢃ3/unit cell) filled with disordered sol-
vent molecules (dichloromethane/ethanol). Their contribution
to the structure factors was ascertained using PLATON/
SQUEEZE[26b] (1407 e/unit cell). All non-hydrogen atoms
were refinedwith anisotropic displacementparameters. Allhy-
drogen atoms were constrained to idealized geometries and al-
lowed to ride on their carrier atoms with an isotropic displace-
ment parameter related to the equivalent displacement param-
eter of their carrier atoms. Structure validation and molecular
graphics preparation were performed with the PLATON pack-
age.[26a] C42H57Cl3N6Pt3 þsolvate, trigonal, R3 (no. 148), a¼b¼
Acknowledgements
This research was supported in part (A. V. C.) by the Nether-
lands Research School Combination Catalysis (NRSC-C),
(P. A. C.) the Natural Sciences and Engineering Research
Council of Canada (NSERC), and (H. P. D., A. M. M. and
A. L. S.) by the Council for Chemical Sciences of the Nether-
lands Organisation for Scientific Research (CW-NWO).
22.6133(4), c¼25.8840(6) ꢃ, V¼11462.8(4) ꢃ3, Z¼6, 2qmax
¼
558. Of the 43247 reflections measured, 5861 were unique, 4754
with I>2s (I), Rint ¼0.06, R(F) [I>2s (I)]¼0.0355, wR(F2)¼
0.0858, S¼1.04, Drmin/Drmax ¼ ꢀ1.41/1.23 e ꢃꢀ3. CCDC 249318
contains the supplementary crystallographic data for this pa-
per. These data can be obtained free of charge via www.ccdc.
cam.ac.uk/conts/retrieving.html (or from the CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK; fax: þ44 1223 336033;
e-mail: deposit@ccdc.cam.ac.uk).
References and Notes
[1] a) E. C. Constable, Coordination Chemistry of Macrocy-
clic Compounds, Academic, San Diego, CA, 1999;
b) L. F. Lindoy, The Chemistry of Macrocyclic Ligand
Complexes, Cambridge University Press, Cambridge,
UK, 1992.
[2] a) P. L. Anelli, N. Spencer, J. F. Stoddart, J. Am. Chem.
Soc. 1991, 113, 5131–5133; b) R. A. Bissell, E. Cordova,
A. E. Kaifer, J. F. Stoddart, Nature 1994, 369, 133–137;
c) J. O. Jeppesen, J. Perkins, J. Becher, J. F. Stoddart, An-
gew. Chem. Int. Ed. 2001, 40, 1216–1221.
[3] C. P. Collier, G. Mattersteig, E. W. Wong, Y. Luo, K.
Beverly, J. Sampaio, F. M. Raymo, J. F. Stoddart, J. R.
Heath, Science 2000, 289, 1172–1175.
[4] C. P. Collier, E. W. Wong, M. Belohradsky, F. M. Raymo,
J. F. Stoddart, P. J. Kuekes, R. S. Williams, J. R. Heath,
Science 1999, 285, 391–394.
[5] a) D. B. Amabilino, J. F. Stoddart, Chem. Rev. 1995, 95,
2725–2829; b) F. M. Raymo, J. F. Stoddart, Chem. Rev.
1999, 99, 1643–1663; c) A. R. Pease, J. O. Jeppesen,
J. F. Stoddart, Y. Luo, C. P. Collier, J. R. Heath, Acc.
Chem. Res. 2001, 34, 433–444.
Crystal Structure Analysis of [7a(BPh4)3] 10
[7a(BPh4)3] 10 was obtained by an exchange reaction from
[7a(BF4)3] 9 and NaBPh4 in acetone. Colorless plates were ob-
tained after recrystallization in acetone/Et2O. Intensity data
were collected for a single crystal (0.27ꢁ0.15ꢁ0.06 mm) on
a Nonius KappaCCD diffractometer with rotating anode
(Mo Ka, l¼0.71073 ꢃ) at 150 K, to a maximum resolution
of 2qmax ¼558. Of the 109149 reflections measured, 38222
were unique, 24201 with I>2s (I) (Rint ¼0.058). An absorption
correction was applied using the multi-scan technique with
PLATON/MULABS (m¼2.548 mmꢀ1, 0.705–0.856 transmis-
sion range).[26a] The structure was solved by automated Patter-
son methods using DIRDIF99,[27] and refined on F2 by least-
squares procedures using SHELXL97.[28] Structure validation
and molecular graphics preparation were performed with the
PLATON package.[26b] C111H174N9O6Pt3 ·3 (C24H20B), Mr ¼
¯
[6] a) J. A. Harnisch, R. J. Angelici, Inorg. Chim. Acta 2000,
300–302, 273–279; b) H. L. Anderson, J. K. M. Sanders,
3273.49, triclinic, P1 (no. 2), a¼18.9296(1), b¼20.6363(1),
c¼22.4100(2) ꢃ, a¼80.4058(3), b¼86.3821(3), g¼
Adv. Synth. Catal. 2005, 347, 447–462
asc.wiley-vch.de
ꢁ 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
461

DEDICATED CLUSTER
FULL PAPERS
Alexey V. Chuchuryukin et al.
J. Chem. Soc. Perkin Trans. 1. 1995, 29, 2223–2229 and
references cited therein.
might increase the yield of 7f; a) H. Pettersson-Fasth,
S. W. Riesinger, J. E. Bꢅckvall, J. Org. Chem. 1995, 60,
6091–6096; b) H. Sajiki, K. Hirota, Tetrahedron 1998,
54, 13981–13996.
[7] a) H. P. Dijkstra, M. D. Meijer, J. Patel, R. Kreiter,
G. P. M. van Klink, M. Lutz, A. L. Spek, A. J. Canty, G.
van Koten, Organometallics 2001, 20, 3159–3168;
b) H. P. Dijkstra, C. A. Kruithof, N. Ronde, R. van de
Coevering, D. J. Ramon, D. Vogt, G. P. M. van Klink,
G. van Koten, J. Org. Chem. 2003, 68, 675–685; c) I. P.
Beletskaya, A. V. Chuchuryukin, H. P. Dijkstra,
G. P. M. van Klink, G. van Koten, Tetrahedron Lett.
2000, 41, 1081–1085.
[18] K. J. Ivin, J. C. Mol, Olefin Metathesis and Metathesis
Polymerization, Academic Press, San Diego, CA, 1997.
[19] Grubbsꢀ first-generation catalyst: a) S. J. Miller, H. E.
Blackwell, R. H. Grubbs, J. Am. Chem. Soc. 1996, 118,
9606–9614; b) T. R. Hoye, H. Zhao, Org. Lett. 1999, 1,
169–171; c) T. R. Hoye, H. Zhao, Org. Lett. 1999, 1,
1123–1125.
[8] a) R. R. Schrock, A. H. Hoveyda, Angew. Chem. Int. Ed.
2003, 42, 4592–4633; b) H. E. Blackwell, D. J. OꢀLeary,
A. K. Chatterjee, R. A. Washenfelder, D. A. Bussmann,
R. H. Grubbs, J. Am. Chem. Soc. 2000, 122, 58–71;
c) T. M. Trnka, R. H. Grubbs, Acc. Chem. Res. 2001, 34,
18–29; d) P. Schwab, M. B. France, J. W. Ziller, R. H.
Grubbs, Angew. Chem. Int. Ed. 1995, 34, 2039–2041;
e) Handbook of Metathesis (Ed.: R. H. Grubbs), Wiley-
VCH, Weinheim, 2003.
[9] a) E. B. Bauer, J. Ruwwe, F. A. Hampel, S. Szafert, J. A.
Gladysz, J. M. Martꢄn-Alvarez, T. B. Peters, J. C. Bohling,
T. Lis, Chem. Commun. 2000, 2261–2262 and references
cited therein; b) T. Shima, F. Hampel, J. A. Gladysz, An-
gew. Chem. Int. Ed. 2004, 43, 5537–5540.
[20] Grubbsꢀ second-generation catalyst: a) S. S. Kinderman,
J. H. van Maarseveen, H. E. Shoemaker, H. Hiemstra,
F. P. J. T. Rutjes, Org. Lett. 2001, 3, 2045–2048; b) J. Wag-
ner, L. M. Martin Cabrejas, C. E. Grossmith, C. Papa-
georgiou, F. Senia, D. Wagner, J. France, S. P. Nolan, J.
Org. Chem. 2000, 65, 9255–9260; c) A. Fꢂrstner, O. R.
Thiel, L. Ackermann, H.–J. Schanz, S. P. Nolan, J. Org.
Chem. 2000, 65, 2204–2207; d) J. Huang, E. D. Stevens,
S. P. Nolan, J. L. Peterson, J. Am. Chem. Soc. 1999, 121,
2674–2678; e) M. Scholl, T. M. Trnka, J. P. Morgan,
R. H. Grubbs, Tetrahedron Lett. 1999, 40, 2247–2250;
f) D. Bourgeois, A. Pancrazi, S. P. Nolan, J. Prunet, J. Or-
ganometal. Chem. 2002, 643–644, 247–252.
[21] S. E. Lehman, J. E Schwendeman, P. M. OꢀDonnell, K. B.
[10] M. Weck, B. Mohr, J.-P. Sauvage, R. H. Grubbs, J. Org.
Chem. 1999, 64, 5463–5471.
Wagener, Inorg. Chem. Acta. 2002, 345, 190–198.
´
[22] E. Thorn-Csanyi, J. Dehmel, H.-D. Luginsland, J. U.
[11] G. Rapenne, C. Dietrich-Buchecker, J.-P. Sauvage, J. Am.
Chem. Soc. 1999, 121, 994–1001.
[12] J. Stahl, J. C. Bohling, E. B. Bauer, T. B. Peters, W. Mohr,
J. M. Martꢄn-Alvarez, F. Hampel, J. A. Gladysz, Angew.
Chem. Int. Ed. 2002, 41, 1872–1876.
Zilles, J. Mol. Cat. A, 1997, 115, 29–35.
[23] D. Joe, L. E. Overman, Tetrahedron Lett. 1997, 38, 8635–
8638.
[24] For an example on photoswitchable dendritic hosts, see:
A. Archut, G. C. Azzellini, V. Balzani, L. De Cola, F.
Vçgtle, J. Am. Chem. Soc. 1998, 120, 12187–12191.
[25] For an example of an 68-membered, 20 O-containing
host with multiple (4) cations, see: P. R. Ashton,
M. C. T. Fyfe, P. T. Glink, S. Menzer, J. F. Stoddart,
A. J. P. White, D. J. Williams, J. Am. Chem. Soc. 1997,
119, 12514–12524.
[26] a) A. L. Spek, J. Appl. Cryst. 2003, 36, 7–13; b) P. van der
Sluis, A. L. Spek, Acta Cryst. 1990, A46, 194–201.
[27] P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bos-
man, S. Garcꢄa-Granda, R. O. Gould, J. M. M. Smits,
C.Smykalla, The DIRDIF99 Program System; Technical
Report of the Crystallography Laboratory, University
of Nijmegen, The Netherlands, 1999.
[13] H. P. Dijkstra, A. Chuchuryukin, B. M. J. M. Suijker-
buijk, G. P. M. van Klink, A. M. Mills, A. L. Spek, G.
van Koten, Adv. Synth. Catal. 2002, 344, 771–780.
[14] C. W. Bird, Transition Metal Intermediates in Organic
Synthesis, Academic Press: New York 1967, 69.
[15] a) A. V. Chuchuryukin, H. P. Dijkstra, B. M. J. M. Suij-
kerbuijk, R. J. M. Klein Gebbink, G. P. M. van Klink,
A. M. Mills, A. L. Spek, G. van Koten, Angew. Chem.
Int. Ed. 2003, 42, 228–230; b) A. V. Chuchuryukin,
H. P. Dijkstra, B. M. J. M. Suijkerbuijk, R. J. M. Klein
Gebbink, G. P. M. van Klink, A. M. Mills, A. L. Spek,
G. van Koten, Russ. J. Org. Chem. 2003, 39, 422–429.
[16] A. Fꢂrstner, A. Leitner, Angew. Chem. Int. Ed. 2003, 42,
308–311.
[17] Use of PtO2
[28] G. M. Sheldrick, SHELXL97, University of Gçttingen,
Germany, 1997.
[17a]
as hydrogenation catalyst or of a nitro-
gen-containing base as inhibitor for the side reaction[17b]
462
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Adv. Synth. Catal. 2005, 347, 447–462