Synthesis, electrochemical and intramolecular charge-transfer properties of 'calix[4]arene-acceptor' diad and triad derivatives

Article abstract of DOI:10.1016/j.tet.2003.11.090

Calix[4]arenes substituted with various acceptor moieties (naphthoquinone (NQ), tetracyanoanthraquinodimethane (TCNAQ)) have been synthesized. In these derivatives the three-dimensional structure of calix[4]arene acts as a weak electron donor (D), connected via a linear sigma spacer to one or two electroactive acceptor (A) units. The electrochemical behavior of these derivatives has been studied by cyclic voltammetry. The UV-Vis spectrum of the TCNAQ triad (A-D-A, 13) reveals the presence of a weak intramolecular charge transfer absorption band.

Full text of DOI:10.1016/j.tet.2003.11.090

Tetrahedron 60 (2004) 1643–1650
Synthesis, electrochemical and intramolecular charge-transfer
properties of ‘calix[4]arene-acceptor’ diad and triad derivatives
*
Cheng-Chu Zeng and James Y. Becker
Department of Chemistry, Ben-Gurion University of the Negev, PO Box 653, Beer-Sheva 84105, Israel
Received 4 July 2003; revised 6 November 2003; accepted 27 November 2003
Abstract—Calix[4]arenes substituted with various acceptor moieties (naphthoquinone (NQ), tetracyanoanthraquinodimethane (TCNAQ))
have been synthesized. In these derivatives the three-dimensional structure of calix[4]arene acts as a weak electron donor (D), connected via
a linear sigma spacer to one or two electroactive acceptor (A) units. The electrochemical behavior of these derivatives has been studied by
cyclic voltammetry. The UV–Vis spectrum of the TCNAQ triad (A–D–A, 13) reveals the presence of a weak intramolecular charge transfer
absorption band.
q 2003 Elsevier Ltd. All rights reserved.
1
0
1
. Introduction
conjugation. For example, binaphthalene with a dihedral
angle ranging from 60 to 1208 as a nonplanar spacer (3 in
1
11
12
Based on Aviram and Ratner’s theoretical proposal of
molecular systems containing a covalent linkage between
electron donor and acceptor units, D–s–A (‘D’ represents
electron donor and ‘A’ stands for electron-acceptor), much
attention has been paid to the design and synthesis of
systems with potential ability for intramolecular charge
transfer. The covalent linkage between TTF and TCNQ
moieties has proved to be a great challenge due to the
difficult synthetic route and problems with purification.
As an alternative, systems with other acceptor groups, such
as quinone, C , pyridinium and viologen cations, have
6
been studied. Recently, Bryce and co-workers reported the
first readily available, analytically pure and stable TTF–s–
TCNAQ and TCNAQ–s–TTF–s–TCNAQ derivatives
Scheme 1) and spiro-cycle (2 in Scheme 1) as a spiro-
conjugation were prepared to achieve increased
dimensionality.
1
3
Calixarenes have attracted widespread interest in recent
years due to their unique combination of properties and
structure. Their preparation is remarkably simple; they can
be readily modified at both lower or upper rim; abound of
conformers and well-defined hydrophobic and hydrophilic
regions make calixarenes suitable hosts for neutral and ionic
species. Tetranitrotetrapropoxycalix[4]arenes with electron-
accepting nitro and electron-donating propoxy substituents
have been used as supramolecular materials with second-
2
,3
4
5
6
7
0
8
b
1
4
order nonlinear optical properties.
(
e.g., 1 in Scheme 1) by attaching TTF (via a sigma spacer)
to moderate acceptor (TCNAQ¼teteracyanoanthraquinone-
dimethane) moiety. Compared with TCNQ, the weaker
acceptor TCNAQ adopts a ‘butterfly’ conformation which
suppresses the rapid formation of intermolecular charge-
transfer complexes during the combination reaction of
TCNAQ and functionalized TTF derivatives. On the other
hand, TCNAQ still has a reasonably high electron affinity.
In the present study we report the synthesis, spectral and
redox properties of novel TCNAQ diad 9, and triads 13
(involving TCNAQ) and 16 (involving naphthoquinone,
NQ), based on calyx[4]arene scaffold. In these systems, the
three-dimensional calix[4]arene framework is used as a
weak electron donor (phenol units) functionalized at the
lower rim by different number of pendant tails bearing
electron-accepting groups (TCNAQ or NQ). The properties
of these new compounds have been investigated by cyclic
voltammetry and UV–Vis spectroscopy.
In order to obtain improved electrically conducting
materials, an increase of dimensionality has also proved to
be of a priority in TTF and TCNQ chemistry. A promising
9
strategy is to design nonplanar materials, and to use spiro-
2. Results and discussion
Keywords: Calix[4]arene-sigma-acceptor; Tetracyanoanthraquino-
dimethane; Napthoquinone; Intramolecular charge transfer; Cyclic
voltammetry.
2.1. Synthesis and NMR spectroscopy
*
Corresponding author. Tel.: þ972-8-6461197; fax: þ972-8-6472943;
The synthesis of TCNAQ-containing calix[4]arene deriva-
tives is outlined in Schemes 2 and 3. Calix[4]arene 4 was
e-mail address: becker@bgumail.bgu.ac.il
0040–4020/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2003.11.090

1644
C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
Scheme 1. Selected examples of D–s–A diads and a D–s–A–s–D triad.
2 2 2 2
Scheme 2. (i) BrCH COOEt/CsF, DMF (67%); (ii) NaOH, EtOH/water, reflux (54%); (iii) SOCl , reflux (quant.); (iv) pyridine/CH Cl , rt (48%).

C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
1645
Scheme 3. (i) BrCH
8%, respectively).
2
COOEt/K
2
CO , CH
3
3
CN, reflux (75%); (ii) NaOH, EtOH/water, reflux (70%); (iii) SOCl
2
, reflux (quant.); (iv) pyridine/CH
2
Cl
2
, rt (36 and
4
converted into the corresponding monoacetate 5 and
diacetate 10, respectively, by alkylation with an excess of
ethylbromoacetate. The acetates were hydrolyzed to
carboxylic acids by refluxing with NaOH in ethanol,
followed by acidification with 50% H SO . Compounds 6
and 11 were subsequently converted to the corresponding
acid chlorides 7 and 12. Condensation with 2-hydroxy-
methyl-TCNAQ (8) in the presence of pyridine, at room
temperature, gave the desired TCNAQ diad 9 and triad 13.
Similarly, condensation with hydroxymethyl-NQ (15)
afforded triad 16.
Basically, calix[4]arenes exist in four conformers: cone,
partial cone, 1,2-alternate and 1,3-alternate. Their structure
1
can be easily distinguished by characteristic H NMR
patterns of the ArCH Ar methylene protons. For example,
2
cone, partial cone, 1,2-alternate and 1,3-alternate will
exhibit a pair of doublets, two pairs of doublets, one singlet
2
4
1
5
and a pair of doublet, and one singlet, respectively. The
structure of compounds 9 and 13 were characterized using
1
13
H and C NMR spectroscopy. For triad 13, the presence of
two doublets of the CH bridging groups (at 3.30 and
4.32 ppm) with geminal coupling constants of 13.4 Hz and
2

1646
C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
Table 1. Oxidation and reduction potentials of calix[4]arenes and related
compounds
because its H NMR spectrum shows one pair of AB
doublets.
a
(
1)
(2)
2E 1/2
Compound
2E 1/2
p
E (ox)
2.2. Electrochemical properties by cyclic voltammetry
9
0.34
0.33
0.34
—
—
0.70
0.69
—
—
—
—
—
1.27
1.56
1.52
1.39
—
1.56
1.57
—
1
1
1
5
1
1
3
4
0
The electrochemical behavior of the redox-active com-
pounds, namely diad 9 and triads 13 and 16 have been
studied at room temperature, by cyclic voltammetry (CV)
and compared with related derivatives, such as calix[4]arene
derivatives 5 and 10, acetoxymethyl-TCNAQ (14) and
naphthoquinone derivative (15). The results are summarized
in Table 1 and a typical CV is shown in Figure 1.
5
6
1.35
a
Concentration of substrates: 1 mM; electrolyte: 0.1 M Bu
Cl ; working electrode: glassy carbon; scan rate: 100 mV/s; reference
electrode: Ag/AgCl.
4 4
NClO /CH2-
2
1
3
3
1.8 ppm in C NMR, is clear evidence for a cone
1
6
1
conformation. In contrast, the H NMR spectrum of the
monoalkylated diad 9 is more complicated and quite
different from its precursors 5 or 6. The chemical shifts of
3
.25–3.55 ppm are attributed to four bridging methylene
equatorial protons, four doublets with integration of 1:1:1:1
and coupling constants of 13.4, 13.5, 14.3, 13.5 Hz, respec-
tively. This information shows that the four methylene
groups are nonequivalent, having different chemical
environments. This is also proved by the four carbon
signals at 32.78, 32.99, 33.98 and 33.99 ppm observed in the
Upon scanning anodically, diad 9 exhibits one well defined
irreversible oxidation wave at 1.52 V (vs. Ag/AgCl),
attributed to the oxidation of the phenol units of calix[4]-
arene. The measured value of oxidation potential of 9 is
slightly less positive (1.52 vs. 1.57 V) than those of
calix[4]arene 5, indicating that there is only a small
influence of the chemically linked TCNAQ moiety on the
oxidation of the phenol units, but in opposite to the expected
direction (any kind of interaction between the phenol units
and the TCNAQ electron acceptor moiety should result in a
higher oxidation potential). The cathodic scan affords one
quasi-reversible wave at E1/2¼20.33 V, similar to the value
obtained for acetoxymethyl TCNAQ 14. It seems that there
is no effect of the covalently bonded calix[4]arene unit on
1
3
C NMR spectrum. On the other hand, the four bridging
methylene axial protons exhibit poorly defined signals and
there are multiple signals for the methylene protons adjacent
1
to the benzene rings. Dynamic H NMR was also used to
confirm the structure. When the temperature increased to
3
53 K, the bridging methylene axial protons also gave four
doublets with coupling constants of 13.4, 13.9, 13.4,
4.3 Hz. The precise reason for such phenomena is unclear,
1
although it may be due to steric interactions between the
calix[4]arene moiety and the TCNAQ side chain, which
may lead to a spatial distortion of the four phenyl units.
Apparently, triad 16 is also in the cone conformation
Figure 1. Cyclic voltammogram of triad 13 in 0.1 M But
4
ClO
4
–CH Cl
2
2
solution, at glassy carbon (GC); Scan rate: 100 mV/s. (Only small variations were
obtained upon using Pt instead of GC or replacing the solvent by acetonitrile.).

C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
1647
the reduction of the TCNAQ moiety. The voltammogram of
triad 13 shows a similar pattern to that of diad 9, with a
quasi-reversible couple E1/2¼20.34 V, but with an irre-
versible oxidation wave at significantly less positive
potential, 1.39 V. Here there is a clear influence of the
chemically linked TCNAQ unit on the oxidation of the
phenol units (again, opposite to the anticipated direction)
but no influence of the calixarene moiety on the reduction of
the TCNAQ units. As for triad 16, with two planar NQ
moieties, this compound gives an irreversible oxidation
wave at 1.35 V, similar to the behavior of triad 13, but
two quasi-reversible redox couples at 20.69 and 21.56 V.
Apparently, there is no effect upon reduction at the first
redox couple compared with 15. However, there is an effect
on the second redox wave that becomes more negative by
receptors for charged or neutral guest molecules. Such
host–guest interaction can be controlled and detected
electrochemically when organic, organometallic or inor-
ganic redox-active centers are incorporated into calix[4]-
arene framework. For example, ferrocenium, cobaltocenium
0
2þ
and tri(2,2 -bipyridyl)ruthenium(II) ([Ru(bpy) ] ) moieties
3
were combined with calix[4]arene to recognize cations,
2
0
anions and neutral species. Calixquinone receptors have
been found to enhance electrostatic affinity to cations when
the quinone moiety is reduced to its dianion. Similarly, in
the case of a quinone-bridged calix[6]arene, in which the
2
1
quinone unit is quite rigid, it was found that the reduction
potential of the quinone moiety is negatively shifted in
comparison with reference compounds without the calixar-
ene macrocycle. The newly synthesized compounds 9, 13
and 16, with redox-active TCNAQ and NQ moieties, could
potentially act as electrochemical sensors for cations when
electrostatic interaction is switched on by reduction of
the acceptor unit(s). As far as we know, so far, no NQ or
TCNAQ unit has been chemically bound to any calixarene
skeleton, as ionophore. Therefore, the electrochemical
behavior of TCNA Q-calixarene diad 9 and triad 13,
which have stronger acceptor units than 16, have been
studied in the presence of various metallic cations by CV,
2
90 mV. This is again in the opposite direction to what
would have been expected, because if any kind of
interaction (e.g., hydrogen bonding) exists between the
anion radical of the NQ moiety in 16 and the phenol units of
the calixarene framework, then the second reduction step
should be less negative, namely, easier to reduce.
In summary, it seems that no significant change was
detected in the reduction of diad 9 and triad 13 with respect
to 14; however, an effect was found in the case of the second
reduction step of 16, compared with 15. Both triads 13 and
1
UV–Vis and H NMR spectroscopy. Surprisingly, CV
experiments (1 mM substrate, in CH Cl –0.1 M But ClO )
2
2
4
4
1
6 show better donor ability than 5 and 10, exhibiting shifts
of the above compounds with metal ions of various ionic
þ þ
in the oxidation potentials of the phenol units to less positive
potentials by almost 170 mV compared with the ‘free’
calixarene derivatives (5 and 10); a smaller variation
radii and charges, such as perchlorate salts of Li , Na ,
2
þ
2þ
Mg and Ba , have shown little changes in the volt-
ammograms, indicating that the electrostatic effects
between the metal ions studied and the reduced TCNAQ
(
,40 mV) is observed in diad 9. The reason(s) behind
1
this unexpected phenomenon, where acceptor units
attached covalently to calix[4]arene skeleton cause the
phenol units to be oxidized more easily, is not clear at this
stage.
moiety in 9 is very weak. Also, the H NMR spectra did not
change upon addition of alkali metal perchlorate to
solutions of 9 and 13 in CD OD. This indicates that binding
3
is probably not taking place in this case. Often the phenolic
groups at the lower rim of calixarenes are hydrogen bonding
to one another, thus reducing their ability for cations
binding. In conclusion, we have found no evidence for
cation binding or sensing using NMR or electrochemical
methods. At present, it is not clear at which stage receptors 9
and 13 fail.
Previously it has been concluded by controlled potential
8
a,17
coulometric analysis
that the number of electrons
involves in the reduction of TCNAQ is 2. Therefore, it is
reasonable to also assume that the reduction wave in the CV
of 9 corresponds to two-electron transfer process leading to
the corresponding dianion. Similarly, the reduction of 13
consists of four electrons, yielding the corresponding
tetraanion. The presence of only one single four-electron
reduction wave in 13 indicates that both tetracyano-9,10-
anthraquinodimethane moieties behave independently and
that each is simultaneously reduced to its dianion. This
behavior suggests that the calix[4]arene ‘holds’ the two
TCNAQ units spatially separated preventing any possible
interaction between them. Similar observations have also
been found in other TCNAQ triad systems with different
2.3. UV–Vis spectra
It is well known that calix[4]arene derivatives bearing
nitriles on the upper rim and alkoxy groups on the lower rim
1
4b
present nonlinear optical (NLO) properties.
Compared
with other NLO-phores consisting of a single p-conjugated
system, calix[4]arene can contain up to four D–p–A
moieties in one molecule. When the four D–p–A units are
symmetrically oriented in one direction (cone confor-
mation), the molecular hyperpolarizability (b) value is
about three times higher than the value of a derivative with
one D–p–A unit. Compounds 9 and 13 could be regarded
as D–s–A systems, in which the TCNAQ moiety is the
acceptor and the calix[4]arene unit is the donor. Similar to
D–p–A systems, the number of D–s–A units might be
important for the expression of charge transfer (CT)
prosperities. Indeed, as evidenced by its UV–Vis spectra,
triad 13 which contains two D–s–A units, exhibits a weak
and broad absorption band in the 420–580 nm region, in
dichloromethane, in addition to the usual TCNAQ and
calix[4]arene absorption bands (Fig. 2), whereas diad 9
1
1,18
spacers.
1
The case of naphthoquinone derivatives 15 and
6 is different. They both exhibit two redox couples,
formally involving 1e transfer each, to electro-generate the
corresponding anion radical and dianion. However, the ratio
of the current amplitudes between the two reduction
processes is not equal to unity because of fast disproportio-
nation of the anion radical, making the ratio usually greater
than unity in favor of the first redox couple, depending on
1
9
scan rate.
As mentioned above, calixarene derivatives are widely used
in supramolecular chemistry for the construction of various

1648
C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
Figure 2. UV–VIS spectrum of compounds (1.4 mM) 13 (a) and 9 (b) in dichloromethane.
which contains only one TCNAQ moiety does not show a
CT band under the same conditions. A mixture of 1:2 molar
ratios of a TCNAQ derivative 14 and a calix[4]arene
derivative 10 does not exhibit a similar absorption band
under the same conditions. Also, the intensity of the
absorption band of 13 shows a dependence on concentration
that is expected for an intramolecular charge transfer
process. It is noteworthy that to date, a similar phenomenon
lower rim of the calix[4]arene scaffold impose a rigid cone
conformation in 13, so that the four benzene rings that
are oriented in the same direction symmetrically, some-
how leading to a spatial interaction between the phenols and
the TCNAQ units (which could lie outside the calixarene
cone), resulting in intramolecular charge-transfer band.
Another possible reason (suggested by a referee) is that a
single TCNAQ moiety is able to arrange itself under-
neath the calixarene ring, whereas in compound 13,
the presence of two TCNAQ moieties will not allow
this. Consequently at least one of the TCNAQs must be
outside the cone of the calixarene ring, and therefore be in a
position to form a charge transfer interaction with the aryl
rings.
8
of intramolecular charge transfer property was reported
only for TCNAQ systems in which the two TCNAQ
moieties are chemically linked through a conjugated
vinylene bridge to the donor (see compound 3 in Scheme
4
e
1
). However, there is an example of such a phenomenon in
a rigid system involving TTF-s-quinone diad in which the
A and D units are spatially close to each other but lack a
conjugation between them. Therefore, the CT phenomenon
observed in 13, which is not a rigid molecule and has two
TCNAQ moieties connected by s bonds to the calixarene
framework, is unique. To try to explain the observation of
intramolecular CT in this system seems to be a difficult task.
Possibly, the two bulky TCNAQ substituents attached to the
Triad 16, which also possesses two D–s–A units like in 13,
and also has a cone conformation, does not show a charge
transfer band. In this case it is not surprising because the
electron accepting property of the NQ unit in 16 is quite
weak relative to TCNAQ in 13, as evidenced by their
corresponding reduction potentials (Table 1).

C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
1649
Finally, it can be concluded that the relative strength of
donor–acceptor affinity, the number of D–s–A units and
the specific orientation of the pending electron accepting
group relative to the calixarene framework, maybe among
other properties too, could play important roles in the
intramolecular charge transfer process that takes place in
molecules of type 13.
was dissolved in 15 mL of dry dichloromethane and was
added dropwise a solution of 2-hydroxy-TCNAQ (38.4 mg,
1.1 mmol for 7 or 77 mg, 2.2 mmol for 12) at room
temperature and followed by pyridine (1.1 mmol for 7 or
2.2 mmol for 12) in 5 mL of dry dichloromethane. The
reaction mixture was stirred for 12 h and the solvent was
removed under reduced pressure. The residue was dissolved
in CHCl (20 mL) and washed with water (20 mL). The
3
separated organic layer was dried over MgSO . After the
4
3
. Conclusion
evaporation of solvent, the crude product was purified by
column chromatography on silica gel eluting with a mixture
of petroleum ether and ethyl acetate with a gradient increase
of ethyl acetate to give products 9 and 13 as a yellow
powders.
Novel TCNAQ (diad 9 and triad 13) and NQ (triad 16)
derivatives covalently linked to the lower rim of calix[4]-
arenes have been synthesized. Of the three derivatives, only
the UV–Vis spectrum of 13 shows an intramolecular charge
transfer band. The redox properties of these derivatives have
been investigated using CV measurements and all of them
show a clear one irreversible oxidation wave corresponding
to the phenolic groups. The TCNAQ derivatives exhibit one
quasi-reversible reduction wave whereas the NQ derivative
has two. Electrochemical cation recognition has also been
studied for 9 and 13 but no binding or sensing was observed.
4.1.1. Monoacid 6. Yield: 55% (white powder). Mp: .
1
270 8C (decomposed); H NMR (DMSO-d
): 1.11 (s, 9H,
6
t-Bu), 1.14 (s, 18H, t-Bu), 1.16 (s, 9H, t-Bu), 3.45 (d, 4H,
J¼13.6 Hz, ArCH Ar), 4.06 (d, 2H, J¼14.3 Hz, ArCH Ar),
4.34 (d, 2H, J¼12.9 Hz, ArCH Ar), 4.74 (s, 4H, CH O),
7.03 (s, 2H, Ar-H), 7.12 (s, 2H, Ar-H), 7.19 (s, 2H, Ar-H),
2
2
2
2
1
3
7.24 (s, 2H, Ar-H), C NMR (CDCl
3.79, 33.90, 34.03 (C(CH3)3 and (ArCH Ar), 71.84
): 30.96, 31.20, 31.70,
3
3
2
(OCH ), 125.11, 125.55, 126.04, 127.55, 127.84, 128.56,
133.76, 142.72, 143.05, 147.66, 150.60, 171.22 (CvO). IR
2
4
. Experimental
2
1
(
KBr): n¼3300–2500 (br), 1765, 1480 cm . HRMS for
All melting points were measured with a melting point
apparatus and are uncorrected. IR spectra were recorded as
C H O
46 58 6
: found, (Mþ1)¼707.4290 (calc. 707.4312).
1
13
KBr pellets. H and C NMR spectra were recorded with a
1
4.1.2. Compound 9. Yield: 48% (yellow powder). Mp:
1
2
00 MHz spectrometer (200 MHz H frequency, 50 MHz
1
C frequency) or 500 MHz spectrometer (500 MHz H
272–274 8C. H NMR (CDCl
9H, t-Bu), 1.28 (s, 9H, t-Bu), 1.34 (s, 9H, t-Bu), 3.28 (d, 1H,
J¼13.4 Hz, ArCH Ar), 3.38 (d, 1H, J¼13.5 Hz, ArCH Ar),
3.44 (d, 1H, J¼14.3 Hz, ArCH Ar), 3.53 (d, 1H, J¼13.5 Hz,
ArCH Ar), 4.11–4.71 (br, m, 6H, ArCH Ar and
ArOCH CO), 5.51 (s, 2H, ArTCAQ-CH O), 6.65 (s, br, 1H,
3
): 0.95 (s, 9H, t-Bu), 1.10 (s,
1
3
1
3
frequency, 125 MHz C frequency). Chemical shifts are
given as values (internal standard: TMS). Cyclic volt-
ammograms were measured by Princeton Applied Research
Potentiostat/Galvanostat Model 273A equipped with
electrochemical analysis software. A one-compartment
cylindrical cell, containing 0.1 M Bu NClO in dichloro-
2
2
2
2
2
2
2
Ar-OH), 6.83 (d, 1H, J¼2.43 Hz, Ar-H), 6.84 (d, 1H, J¼
1.84 Hz, Ar-H), 6.85 (d, 1H, J¼2.38 Hz, Ar-H), 7.04 (d, 2H,
J¼2.44 Hz, Ar-H), 7.06 (d, 1H, J¼2.40 Hz, Ar-H), 7.10
(d, 2H, J¼2.0 Hz, Ar-H), 7.17 (s, br, 1H, Ar-OH), 7.22 (s,
br, 1H, Ar-OH), 7.62–7.77 (m, 3H, ArTCAQ-H), 8.11–8.35
4
4
methane (or acetonitrile), and a glassy carbon (GC) working
electrode, Pt wire counter electrode and Ag/AgCl (in 2 M
NaCl) reference electrode, were employed. Solvents were
chemically pure and purified by standard procedures.
1
3
(m, 3H, ArTCAQ-H), 8.44(s, 1H, ArTCAQ-H), C NMR
(CDCl ): 30.89, 31.15, 31.40, 31.59 (C(CH ) ), 32.78,
3 3 3
2
2
23
8a
24
25
8b
26
Compounds 4, 5, 8, 10 11, 14 and 15 were
synthesized according to literature procedures. Compound 6
32.99, 33.99, 33.98 (ArCH
(C(CH ), 65.46 (ArOCH
(CN), 113.12 (CN), 160.10 (C(CN)
2
Ar), 34.08, 34.24, 34.36, 34.53,
)
), 71.98 (ArTCAQ-CH O), 112.87
2
3
3
2
2
5
was prepared similar to a known procedure, by refluxing a
suspension of 5 (2 moles) in ethanol (30 mL)–water
20 mL), containing NaOH (50 moles), for 24 h. The cooled
solution was acidified to pH¼1 by 50% sulphuric acid. The
resulting precipitate was isolated, washed with water, dried
under vacuum and recrystallized from ethanol–water to
give a white powder, in 55% yield.
2
), 168.40 (CvO).
2
1
IR (KBr): n¼3437, 2965, 2230(CN), 1750, 1480 cm
.
for
þ
(
MALDI-TOF
N
(Mþ1) for C67 (calc. 1024.257).
MS:
m/z
1045.38(MþNa )
C
H
66
O
6
Na. HRMS MS: m/z¼1023.970: found, for
67
4
H N O
67 4 6
4.1.3. Compound 13. Yield: 36% (orange powder). Mp:
1
206–208 8C; H NMR (CDCl ): 0.95 (s, 18H, t-Bu), 1.31
3
4.1. General procedure for the synthesis of compound 9
and 13
(s, 18H, t-Bu), 3.30 (d, 4H, J¼13.26 Hz, ArCH
(d, 4H, J¼13.4 Hz, ArCH Ar), 4.74 (s, 4H, CH OAr), 5.42
s, 4H, Ar CH OCO), 6.80 (s, 4H, Ar-H), 7.07 (s,
2
Ar), 4.33
2
2
(
TCAQ
2
A mixture of monoacid 6 (710 mg, 1 mmol) or diacid 11
4H, Ar-H), 7.15 (s, 2H, Ar-OH), 7.68–8.25 (m, 12H,
1
3
(
764 mg, 1 mmol) and an excess of SOCl2 (40 mmol,
.9 mL) was stirred under reflux for 3 h. The solvent was
distilled off, the residue was dissolved in anhydrous CH Cl
ArTCAQ-H), 8.42 (d, 2H, ArTCAQ-H), C NMR (CDCl
31.08 (C(CH ), 31.82 (ArCH Ar), 34.05 (C(CH ), 65.69
(OCH ), 72.28 (OCH ), 112.98 (CN), 113.22 (CN), 125.50,
3
):
2
3
)
3
2
)
3 3
2
2
2
2
(
5 mL) and the solvent was again evaporated under reduced
125.96, 127.17, 127.73, 127.94, 129.87, 130.21, 130.85,
131.77, 132.38, 132.55, 140.83, 142.16, 147.56, 149.45,
pressure. This procedure was repeated twice to remove all
traces of thionyl chloride. The resulting solid (acyl chloride
7
150.54, 160.00 (C(CN)
), 160.27 (C(CN) ), 168.37
2
2
2
1
or 12) was then dried in a high vacuum for 1 h. The solid
(CvO). IR (KBr): n¼2950, 2230 (CN), 1757, 1487 cm
.

1650
C.-C. Zeng, J. Y. Becker / Tetrahedron 60 (2004) 1643–1650
þ
MALDI-TOF
MS:
m/z¼1420.37
(MþNa )
for
of Chemistry: Cambridge, UK, 1989. (b) B o¨ hmer, V. Angew.
Chem., Int. Ed. Engl. 1995, 34, 713.
C H N O Na. HRMS MS: m/z¼1397.542: found, for
9
0 76 8 8
(
Mþ1) for C H N O (calc. 1397.596).
14. (a) Kenis, P. J. A.; Noordman, O. F. J.; Sch o¨ nherr, H.; Kerver,
E. G.; Snellink-Ru e¨ l, B. H. M.; van Hummel, G. J.; Harkema,
S.; van der Vorst, C. P. J. M.; Hare, J.; Picken, S. J.;
Engbersen, J. F. J.; van Hulst, N. F.; Vancso, G. J.; Reinhoudt,
D. N. Chem. Eur. J. 1998, 4, 1225. (b) Kelderman, E.;
Heesink, G. J. T.; Derhaeg, L.; Verbiest, T.; Klaase, P. T. A.;
Verboom, W.; Engbersen, J. F. J.; van Hulst, N. F.; Clays, K.;
Persoons, A.; Reinhoudt, D. N. Adv. Mater. 1993, 5, 925.
15. (a) Gutsche, C. D.; Iqbal, M.; Nam, K. S.; See, K.; Alam, I.
Pure Appl. Chem. 1988, 60, 483. (b) Iqbal, M.; Mangiafico, T.;
Gutsche, C. D. Tetrahedron 1987, 43, 4917. (c) Gutsche, C. D.
Calixarenes. Royal Society of Chemistry: Cambridge, 1989.
16. Gong, S.-L.; Wang, W.; Chen, Y.-Y.; Meng, L.-Z.; Wan, T.
New J. Chem. 2002, 26, 1827.
9
0 76 8 8
4.1.4. Compound 16. Yield: 48% (dark brown powder).
1
Mp: 130 8C (decomposed); H NMR (CDCl ): 0.93 (s, 18H,
3
t-Bu), 1.27 (s, 18H, t-Bu), 3.30 (d, 4H, J¼13.2 Hz,
ArCH Ar), 4.34 (d, 4H, J¼13.2 Hz, ArCH Ar), 4.83
2
2
(
s, 4H, CH OAr), 5.36 (s, 4H, Ar
2
CH O), 6.75 (s,
2
Quinone
4
7
3
6
1
1
H, Ar-H), 6.95 (s, 4H, ArQuinone-H), 7.02 (s, 4H, Ar-H),
1
3
.81–8.06 (m, 6H, ArQuinone-H); C NMR (CDCl3):
0.87(C(CH ) ), 31.57(ArCH Ar), 33.74(C(CH3)3),
5.59(OCH CO), 72.24(COOCH2), 168.55(COOCH2),
3
3
2
2
84.47(Naphthoquinone). IR (KBr): n¼1757, 1675,
485 cm2 ; MALDI-TOF MS: m/z 1127.39 (MþNa ) for
1
þ
þ
C H O Na, 1143.37(MþK ) for C H O K.
7
0
72 12
70 72 12
1
1
1
2
7. Kini, A. M.; Cowan, D. O.; Gerson, F.; Mockel, R. J. Am.
Chem. Soc. 1985, 107, 556.
8. Herranz, M. A.; Gonz a´ lez, S.; P e´ rez, I.; Mart ´ı n, N.
Tetrahedron 2001, 57, 725.
References and notes
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(
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. (a) Prato, M.; Maggini, M.; Giacometti, C.; Scorrano, G.;
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(
b) Llacay, J.; Veciana, J.; Vidal-Gancedo, J.; Bourdelande,
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1
999, 657. (d) Mart ´ı n, N.; S a´ nchez, L.; Illescas, B.; P e´ rez, I.
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´
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6
. Goldenberg, L. M.; Becker, J. Y.; Levi, O. P-T.;
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9
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