Macrocycles incorporating an endocyclic but non-sterically-hindering chelate: Synthesis and structural studies

Article abstract of DOI:10.1002/hlca.200790145

Two rings of different size have been prepared both incorporating a 3,3′-biisoquinoline (biiq) chelate. The biiq ligand bears phenyl groups at its 8- and 8′-positions, which provide it with an approximate crescent shape. The incorporation of the 8,8′-diar

Full text of DOI:10.1002/hlca.200790145

Helvetica Chimica Acta – Vol. 90 (2007)
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Macrocycles Incorporating an Endocyclic But Non-Sterically-Hindering
Chelate: Synthesis and Structural Studies
by Fabien Durola, Jean-Pierre Sauvage*, and Oliver S. Wenger
´
´
Laboratoire de Chimie Organo-Minerale, UMR 7177, Institut Le Bel, Universite Louis pasteur,
4rue Blaise Pascal, F-67070 Strasbourg Cedex
(phone: þ 33390-241-364; fax: þ 33390-241-368; e-mail: sauvage@chimie.u-strasbg.fr)
Two rings of different size have been prepared both incorporating a 3,3’-biisoquinoline (biiq)
chelate. The biiq ligand bears phenyl groups at its 8- and 8’-positions, which provide it with an
approximate crescent shape. The incorporation of the 8,8’-diaryl-3,3’-biisoquinoline motif in a ring leads
to an unusual situation. The complexing site of the macroring is unambiguously pointing towards the
inner part of the macrocycle, but, at the same time, it is not sterically hindered, due to the relatively large
distance between the coordinating site and the various organic groups belonging to the macrocyclic
structure. The synthesis of the two compounds is reported, as well as the X-ray structure of one of them,
which confirms the expected geometrical properties of the molecules.
Introduction. – The field of catenanes and rotaxanes has experienced a remarkable
development in the course of the last twenty years [1 – 3], in relation to the synthetic
challenge that the preparation of such compounds represents, and to their novel
properties, in particular, as controlled dynamic molecular systems, often referred to as
ꢀmolecular machinesꢁ [4]. The design and the preparation of the macrocyclic subunits,
components of such species, is thus essential, both in terms of preparation of the target
compounds, and as far as their properties are concerned. The use of transition metals as
templates has been particularly useful in the field of interlocking topologies [5], and we
would now like to report a new family of coordinating rings whose complexing
properties are novel, and which will be incorporated in catenanes and rotaxanes in the
future. These macrorings are also promising coordinating species in themselves and will
also be studied as such.
As already briefly discussed in a preliminary report [6], the design and the
preparation of coordinating rings incorporating an endocyclic but non-sterically-
hindering bidentate chelate of the aromatic polyimine family (1,10-phenanthroline or
2,2’-bipyridine) is far from trivial. As far as we are aware, most of the systems reported
so far contain a sterically congested coordination site, since the points of attachment of
the chelate are the positions ortho to the N-atoms and thus close to the transition-metal
centre to be complexed. The use of an 8,8’-diaryl-3,3’-biisoquinoline motif changes the
situation in a dramatic manner: with such a building block, the coordination site will be
located in the inner part of the ring. In addition, the distance between the two phenyl
rings borne by the ligand will be such that no or only very limited steric hindrance will
be experienced within the complex. We would now like to describe the synthesis of two
such biiq-containing rings as well as the crystal structure of one of them, which provides
ꢂ 2007 Verlag Helvetica Chimica Acta AG, Zürich

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convincing evidence that the coordination site is indeed endotopic but not particularly
congested from a steric viewpoint.
Results. – The target macrocyclic ligands are depicted in Fig. 1. Compound 1 is a 39-
membered ring, whereas 2 is a 41-membered ring. From the chemical structure of the
compounds, it is obvious that the biiq chelate will point towards the centre of the ring,
and that steric hindrance will not be important provided the other ligands of the
transition-metal complex are not too bulky.
Fig. 1. The two macrocyclic ligands described in the present report
The key starting compound used for the synthesis of both macrocycles is the chelate
8,8’-bis(4-methoxyphenyl)-3,3’-biisoquinoline (3) whose synthesis has been described
in a previous paper [7]. As shown in Scheme 1, the two 4-methoxyphenyl groups were
first deprotected in melted pyridinium chloride, at high temperature, to give the
diphenol compound 4 in a quantitative yield. To obtain a macrocycle by an
intramolecular double Williamson reaction from 4, it was necessary to have an end-
functionalized linear fragment. Brominated chains have been chosen because of their
better reactivity in nucleophilic substitutions than chlorinated ones, and due to their
better resistance to eliminations than iodinated ones. The length of the chain is
obviously a critical parameter. In fact, the dibrominated molecule obtained from the
hexakis(ethylene glycol) appeared to be too short (since only a bigger macrocycle
including two ligands and two chains has been analyzed), in spite of an apparently good
design predicted by CPK models. In addition, we decided to build these chains around
one central bisphenol A, or 2,2-bis(4-hydroxyphenyl)propane (5), in order to improve
their shape and rigidity, in prevision of the cyclization. As represented in Scheme 2, two
chains have been synthetized in such a way. The first one, 2,2-bis[4-(3-bromobut-
oxy)phenyl]propane (6), was obtained in one step by a double Williamson reaction
between bisphenol A and a large excess of 1,4-dibromobutane. The second
dibrominated chain was synthetized in two steps: first a double Williamson reaction
between bisphenol 5 and 2-(2-chloroethoxy)ethanol led to the diol 7, which was then

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Scheme 1. Demethylation Reaction Leading to Diphenol 4
Scheme 2. Formation of Brominated Chains
a) Cs2CO3, DMF, 608, 16 h, 48%. b) Cs2CO3, DMF, 908, 16 h; 4 0%.c) MsCl, Et3N, CH2Cl2, 08, 3 h,
followed by LiBr, acetone, reflux, 16 h; 82%.

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converted, according to a classical strategy [5], to the dibrominated chain 8, via a
dimesylated species.
As shown in Scheme 3, macrocycles 1 and 2 were obtained by an intramolecular
double Williamson reaction from the dibrominated chains 6 and 8, respectively, and
diphenol 4. To favor intramolecular reactions instead of intermolecular ones, these two
reactions were carried out in high-dilution conditions. Macrocycle 2 was obtained in a
much better yield than 1, certainly because of the longer and more flexible dibromo
Scheme 3. High-Dilution Reactions Leading to Macrocycles 1 and 2
a) Cs2CO3, DMF, 658, 75 h; 34%. b) Cs2CO3, DMF, 658, 60 h; 62%.

Helvetica Chimica Acta – Vol. 90 (2007)
1443
chain 8. As a matter of fact, the dibrominated chain 6, obtained from dibromobutane,
was the shortest that could undergo cyclization with diphenol 4, since a little shorter
dibromo chain, obtained from dibromopropane and bisphenol 5, has been tried before
without any result. However macrocycle 1, thanks to its rigidity, can be crystallized
from CH2Cl2 and (i-Pr)2O, which allowed structure determination by X-ray diffraction,
as shown in Fig. 2. From the molecular structure represented in Fig. 1, it is obvious that
the chelate is not sterically hindering but is endocyclic. In other words, the coordination
site always points towards the inner part of ring.
Fig. 2. Crystal structure of macrocycle 1
Conclusions. – In conclusion, two new macrocyclic compounds have been prepared
which incorporate a non-sterically-hindering but obviously endocyclic chelate. The
synthesis procedure relies on a double ether-forming reaction performed under
approximate high-dilution conditions. The largest cycle is a 41-membered ring obtained
in good yield (62%) from its two linear di-end-functionalized components. The
incorporation of the presently reported cyclic systems into catenanes and rotaxanes is
under way.
Experimental Part
General. The following chemicals were obtained commercially and were used without further
purification: 2,2-bis(4-hydroxyphenyl)propane (Lancaster), 1,4-dibromobutane (Aldrich), Cs2CO3
(Aldrich), 2-(2-chloroethoxy)ethanol (Aldrich), MsCl (Fluka), LiBr (Lancaster). Dry solvents were
obtained with suitable dessicants: CH2Cl2 from NaH, Et3N from KOH. All column chromatographies
(CC) were performed with Merck silica gel 60 (0.063 – 0.200 mm). 1H- and 13C-NMR spectra were

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recorded with a Bruker AVANCE-300 (300 MHz (1H)) spectrometer using deuterated solvent as the
lock. The spectra were collected at 258, and the chemical shifts were referenced to residual solvent H-
1
atoms as internal standards. H: CD2Cl2 5.32 ppm, (D6)DMSO 2.50 ppm. Mass spectra were obtained
with a VG ZAB-HF spectrometer (FAB) and a VG-BIOQ triple quadrupole in positive- or negative-ion
mode (ES-MS). Single-crystal X-ray diffraction experiments were carried out with a Kappa CCD
diffractometer using graphite-monochromated MoKa radiation (l ¼ 0.71073 Š). The SHELX-97
program was used for structure solution and refinement.
4,4’-(3,3’-Biisoquinoline-8,8’-diyl)diphenol (4). 8,8’-(4-Methoxyphenyl)-3,3’-biisoquinoline (3;
1.00 g, 2.13 mmol) and pyridinium chloride (ca. 10 equiv., 2.5 g) were mixed into a little flask and
heated to reflux in an adapted microwave oven for 10 min. Twice, the same quantity of pyridinium
chloride was added, and the mixture was heated to reflux again for 10 min. The mixture was dissolved in
dist. H2O (1 l) and then neutralized with NaOH to give a suspension of a pale yellow precipitate. After
filtration, compound 4 was quantitatively obtained without any purification (pale yellow solid; 940 mg,
100%). 1H-NMR ((D6)DMSO, 300 MHz): 9.35 (s, 2 H); 9.09 (s, 2 H); 8.15 (d, J ¼ 8.2, 2 H); 7.94( t, J ¼ 7.7,
2 H); 7.65 (d, J ¼ 7.0, 2 H); 7.45 (d, J ¼ 8.4, 4 H); 7.00 (d, J ¼ 8.4, 4 H). ES-MS: 441.1559 ([M þ 1]þ,
C30H21N2Oþ2 ; calc. 441.1598).
1,1’-Propane-2,2-diylbis[4-(4-bromobutoxy)benzene] (6). 4,4’-(Propane-2,2-diyl)diphenol (5; 2.28 g,
10 mmol), 1,4-dibromobutane (21.6 g, 12.1 ml, 100 mmol), and Cs2CO3 (3.9 g, 12 mmol) were mixed in
DMF (30 ml) and heated, with stirring, at 608 overnight. The solvent was evaporated, and the residue was
dissolved in CH2Cl2 (100 ml) and dist. H2O (100 ml). The org. phase was separated, and the aq. phase was
extracted twice with CH2Cl2. The combined org. phases were washed first with brine, then with dist. H2O.
The solvent was evaporated, and the residue was purified by CC (silica gel; CH2Cl2/pentane 1:4) to give 6
(2.38 g, 48%). Colorless solid. 1H-NMR (CD2Cl2, 300 MHz): 7.11 (d, J ¼ 8.6, 4H); 6.76 ( d, J ¼ 8.8, 4H);
3.95 (t, J ¼ 6.1, 4H); 3.49 ( t, J ¼ 6.6, 4H); 2.09 – 1.99 ( m, 4H); 1.94– 1.85 ( m, 4 H); 1.61 (s, 6 H). ES-MS:
514.102 ([M þ 18]þ, C23H34NO2Brþ2 ; calc. 514.096).
33,34-Dimethyl-24,29,39,44-tetraoxa-9,12-diazanonacyclo[43.2.2.220,23 ; 230,33.235,38.16,10.111,15.02,7.014,19]-
heptapentaconta-1(47),2,4,6(57),7,9,11(56),12,14,16,18,20,22,30,32,35,37,45,48,50,52,54-docosaene (1). A
mixture of 4 (500 mg, 1.14mmol) and 6 (576 mg, 1.16 mmol) in 300 ml of degassed DMF was introduced
in a high-dilution funnel fitted on a 2-l round-bottom flask containing Cs2CO3 (20 g, 0.06 mol) in
suspension in 1 l of degassed DMF. The vessel was heated at 658, and the mixture in the funnel was added
dropwise during 75 h. After further stirring for 30 h, the solvent was removed, and the residue was taken
up in CH2Cl2/H2O. The org. phase was separated, and the aq. phase was extracted twice with CH2Cl2. The
combined org. phases were washed first with brine, then with dist. H2O. The solvent was removed, and the
residue was mixed with 100 ml of CH2Cl2. The white product in suspension was removed by filtration
through a fritted-glass filter funnel with porosity 4, the solvent of the filtrate was evaporated, and the
residue was purified by CC (silica gel; CH2Cl2/MeOH 99 :1) to give 1 (297 mg, 34%). Yellow solid. In a
cristallization tube, with CH2Cl2 as a good solvent and heptane as a bad solvent, this compound gave one
single big yellow crystal. 1H-NMR (CD2Cl2, 300 MHz): 9.38 (s, 2 H); 8.37 (s, 2 H); 7.94 (d, J ¼ 8.2, 2 H);
7.77 (t, J ¼ 8.2, 2 H); 7.58 (d, J ¼ 8.2, 2 H); 7.46 (d, J ¼ 8.7, 4H); 7.15 ( d, J ¼ 8.9, 4H); 7.09 ( d, J ¼ 8.7, 4H);
6.81 (d, J ¼ 8.9, 4H); 4.26 ( t, J ¼ 6.2, 4H); 3.99 ( t, J ¼ 6.1, 4H); 2.02 – 1.95 ( m, 8 H); 1.59 (s, 6 H). ES-MS:
777.3757 ([M þ 1]þ, C53H49N2Oþ4 ; calc. 777.3692). Crystal-structure analysis of 1: C65H20Cl4N2O4, Mr ¼
1034.63, triclinic, a ¼ 13.6610(3), b ¼ 14.4330(3), c ¼ 14,8440(3) Š, a ¼ 103.7910(7)8, b ¼ 105.6240(9)8,
g ¼ 92.9520(7)8, V¼ 2716.35(10) Š3, T¼ 173(2) K, space group P1, Z ¼ 2, m(MoKa) ¼ 0.268 mmꢀ1, 24318
collected reflections, 15825 independent reflections (R(int) ¼ 0.029), final R indices R1 ¼ 0.089, wR2 ¼
0.3872 (there are two disordered CH2Cl2 molecules). CCDC-621657 contains the supplementary
crystallographic data for this paper. These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
2,2’-[Propane-2,2-diylbis(benzene-4,1-diyloxyethane-2,1-diyloxy)]diethanol (7). Compound 5 (2 g,
8.8 mmol), 2-(2-chloroethoxy)ethanol (3.3 g, 26.5 mmol), and Cs2CO3 (6 g, 18 mmol) were mixed in
DMF (30 ml) and heated, with stirring, at 908 overnight. The solvent was evaporated, and the residue was
dissolved in CH2Cl2 (100 ml) and dist. H2O (100 ml). The org. phase was separated, and the aq. phase was
extracted twice with CH2Cl2. The combined org. phases were washed first with brine, then with dist. H2O.
The solvent was evaporated, and the residue was purified by CC (silica gel; Et2O/EtOH 95 :5, 90 :10 and

Helvetica Chimica Acta – Vol. 90 (2007)
1445
80 :20) to give 7 (1.4g, 40%). Colorless oil. 1H-NMR (CD2Cl2, 300 MHz): 7.12 (d, J ¼ 8.8, 4H); 6.79 ( d,
J ¼ 9.0, 4H); 4.08 ( t, J ¼ 4.7, 4 H); 3.81 (t, J ¼ 4.7, 4 H); 3.72 – 3.66 (m, 4H); 3.63 – 3.59 ( m, 4 H); 1.61 (s,
6 H). ES-MS: 427.212 ([M þ 23]þ, C23H32NaOþ6 ; calc. 427.210).
1,1’-Propane-2,2-diylbis{4-[2-(2-bromoethoxy)ethoxy]benzene} (8). Compound 7 (1.4g, 3.5 mmol)
was dissolved in dry CH2Cl2 (150 ml). The soln. was cooled to ca. ꢀ 28 in an ice/salt mixture, then Et3N
(8 ml) was added. The subsequent addition of MsCl (1.3 g, 0.9 ml, 11 mmol) in CH2Cl2 (50 ml) was
conducted dropwise over a period of 1 h, under Ar. The soln. was then allowed to stir at 08 for 3 h. Dist.
H2O (50 ml) was then added dropwise over a period of 15 min, and the mixture was allowed to warm to
r.t. The org. phase was separated, and the aq. phase was extracted twice with CH2Cl2. The combined org.
phases were washed with dist H2O. The solvent was evaporated, and the residue was directly used without
further purification: it was dissolved in 50 ml of acetone with LiBr (3.3 g, 38 mmol), and the soln. was
heated to reflux overnight, under Ar. A white precipitate of lithium methanesulfonate appeared. The
solvent was evaporated, and the residue was dissolved in CH2Cl2 (100 ml) and dist. H2O (100 ml). The
org. phase was separated, and the aq. phase was extracted twice with CH2Cl2. The combined org. phases
were washed with dist. H2O. The solvent was evaporated, and the residue was purified by CC (silica gel;
Et2O/EtOH 98 :2) to give 8 (1.5 g, 82%). Yellow oil. 1H-NMR (CD2Cl2, 300 MHz): 7.12 (d, J ¼ 9.0, 4H);
6.79 (d, J ¼ 9.0, 4H); 4.08 ( t, J ¼ 4.7, 4 H); 3.81 – 3.87 (m, 8 H); 3.4 9 (t, J ¼ 6.1, 4H); 1.62 ( s, 6 H). ES-MS:
546.090 ([M þ 18]þ, C23H34Br2NOþ4 ; calc. 546.086).
35,35-Dimethyl-24,27,30,40,43,46-hexaoxa-9,12-diazanonacyclo[45.2.2.220,23.231,34.236,69.16,10.111,15
.
02,7.014,19]nonapentaconta-1(49),2,4,6(59),7,9,11(58),12,14,16,18,20,22,31,33,36,38,47,50,52,54,56-doco-
saene 2. A mixture of 4 (200 mg, 0.45 mmol) and 8 (258 mg, 0.49 mmol) in 120 ml of degassed DMF was
introduced in a high-dilution funnel fitted on a 1-l round-bottom flask containing Cs2CO3 (2.5 g,
7.7 mmol) in suspension in 250 ml of degassed DMF. The vessel was heated at 658, and the mixture in the
funnel was added dropwise during 60 h. After further stirring for 20 h, the solvent was removed, and the
residue was taken up with CH2Cl2/H2O. The org. phase was separated, and the aqueous phase was
extracted twice with CH2Cl2. The combined org. phases were washed first with brine, and then with dist.
H2O. The solvent was removed, and the residue was purified by CC (silica gel; CH2Cl2/MeOH 99 :1) to
1
give 2 (229 mg, 62%). Yellow solid. H-NMR (CD2Cl2, 300 MHz): 9.35 (s, 2 H); 8.39 (s, 2 H); 7.95 (d,
J ¼ 8.2, 2 H); 7.77 (t, J ¼ 8.2, 2 H); 7.57 (d, J ¼ 8.2, 2 H); 7.46 (d, J ¼ 8.9, 4H); 7.14– 7.09 ( m, 8 H); 6.78 (d,
J ¼ 8.9, 4H); 4.31 ( t, J ¼ 4.4, 4 H); 4.07 (t, J ¼ 4.6, 4 H); 3.94 – 3.86 (m, 8 H); 1.62 (s, 6 H). ES-MS:
809.3686 ([M þ 1]þ, C53H49N2Oþ6 ; calc. 809.3585).
´
Funding from the following institutions is gratefully acknowledged: the CNRS and the Region Alsace
(fellowship to F. D. ) and the Swiss National Science Foundation (fellowship to O. S. W.). Dr. A. De Cian
is acknowledged for the crystal-structure resolution, Dr. K. Rissanen and Dr. L. Russo for their helpful
work on structure refinement.
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Received May 22, 2007