Synthesis, structure, and complexing property of p-tert-butylcalix[4]arene 1,3-digallate

Article abstract of DOI:10.1021/ol9913993

(figure presented) p-tert-Butylcalix[4]arene 1,3-digallate, which contains a nonbonded close contact between galloyl groups, was synthesized and its structure was determined by dynamic ¹H NMR and X-ray crystallography. The electronic spectra showed that a new absorption band of the complexes appeared at a longer wavelength region upon adding Ag⁺ ion. This spectral shift was explained in terms of the interaction between the facing galloyl groups of the lower rim of the calixarene framework.

Full text of DOI:10.1021/ol9913993

ORGANIC
LETTERS
2000
Vol. 2, No. 6
779-781
Synthesis, Structure, and Complexing
Property of p-tert-Butylcalix[4]arene
1,3-Digallate
Eisaku Nomura,* Asao Hosoda, and Hisaji Taniguchi
Industrial Technology Center of Wakayama Prefecture,
60 Ogura, Wakayama 649-6261, Japan
nomura@wakayama-kg.go.jp
Received December 24, 1999
ABSTRACT
p-tert-Butylcalix[4]arene 1,3-digallate, which contains a nonbonded close contact between galloyl groups, was synthesized and its structure
1
was determined by dynamic H NMR and X-ray crystallography. The electronic spectra showed that a new absorption band of the complexes
appeared at a longer wavelength region upon adding Ag+ ion. This spectral shift was explained in terms of the interaction between the facing
galloyl groups of the lower rim of the calixarene framework.
Considerable attention has been paid to the synthesis and
properties of functionalized calixarenes because of their
potential utility as molecular receptors and ionophores.1 The
design of calixarenes containing the desired properties
requires the control of their conformation, which possibly
is achieved by the use of intramolecular hydrogen-bonding
interactions between substituents on the calixarene skeleton.2
Gallic acid is a component of plant tannin3 and exhibits a
variety of chemical and biological properties that include
pharmacological activity4 and also binding to protains5 and
metal ions.6 Three hydroxyl groups of gallic acid play an
important role in these propaties.4,5 On the basis of these
backgrounds, we thought that the introduction of gallic acids
into the lower rim of p-tert-butylcalix[4]arene may serve to
stabilize the conformation of the calixarene through hydrogen
bonding and act as a binding site toward guest molecules or
ions. We now report the synthesis of p-tert-butylcalix[4]arene
1,3-digallate and its binding property toward metal ions in
connection with the conformation.
(1) (a) Gutsche, C. D. Calixarenes, Monographs in Supramolecular
Chemistry; Stoddart, J. F., Ed.; The Royal Society of Chemistry: Cambridge,
1989. (b) Gutsche, C. D. Calixarenes ReVisited, Monographs in Supra-
molecular Chemistry; Stoddart, J. F., Ed.; The Royal Society of Chemis-
try: Cambridge, 1998. (c) Calixarenes: A Versatile Class of Macrocyclic
Compounds; Bo¨hmer, V., Ed.; Kluwer Academic Publishers: Dordrecht,
1991.
(2) (a) Nomura, E.; Takagaki, M.; Nakaoka, C.; Uchida, M. Taniguchi,
H. J. Org. Chem. 1999, 64, 3151. (b) Rudkevich, D.; Hilmersson, M. G.;
Rebek, J. J. J. Am. Chem. Soc. 1997, 119, 9911. (c) Scheerder, J.; Vreekamp,
R. H.; Engbersen, J. F. J.; Verboom, W.; v. Duynhoven, J. P. M.; Reinhoudt,
D. N. J. Org. Chem. 1996, 61, 3476.
Calixarene 2 was prepared by the reaction of p-tert-
butylcalix[4]arene 1 (1.54 mmol) with O-acetylgalloyl
chloride (12.4 mmol) in CH2Cl2 in the presence of triethyl-
amine (12.4 mmol).7 Calixarene 2 was obtained as prisms
in 87% yield. Deacetylation of 2 with NH2NH2‚H2O or
(4) Economic and Medicinal Plant Research, Vol. 5; Wagnner, H.,
Farnsworth, N. R., Eds.; Academic Press: New York, 1991.
(5) Okuda, T. Mori, K.; Hatano, T. Chem. Pharm. Bull. 1985, 33, 1424.
(6) Okuda, T.; Mori, K.; Shiota, M.; Ida, K. Yakugaku Zasshi 1982, 102,
735.
(3) Plant Polyphenols; Hemingway, R. W., Laks, P. E., Eds.; Plenum
Press: New York, 1992.
10.1021/ol9913993 CCC: $19.00 © 2000 American Chemical Society
Published on Web 02/16/2000

Scheme 1a
a Reagents and conditions: (i) ClCOC6H2(OAc)3, Et3N, CH2Cl2,
rt, 5 h; (ii) H2NNH2‚H2O, CH3CN, rt, 30 min; (iii) aqueous NH3,
CH3CN, rt, 2 h.
Figure 2. Temperature dependence of chemical shifts for the OH
protons of 3a (400 MHz, THF-d8).
and then upfield until reaching -70 °C. This signal separated
into two signals which appeared at 8.64 (Hb) and 8.32 (Hc)
ppm at -100 °C. The aromatic proton signals of the galloyl
groups were also observed as two separated signals at 8.24
and 7.13 ppm at -100 °C. The separated upfield signal of
the Hc proton suggests that the OHc group is situated at a
position which is affected by the ring current effect associated
with the facing galloyl group. The Hd proton also shifted
downfield by 1.74 ppm upon cooling from 20 to -100 °C.
This suggests that the OHd group forms a hydrogen bond
with the neighboring ether oxygen atom8 (see later).
aqueous NH3 in MeCN at room temperature gave 3a and
3b in 76 and 40% yields, respectively (Scheme 1). The
structures of all the compounds were established by NMR
and elemental analyses.
The H NMR spectrum of 3a in THF-d8 at 20 °C was
simple, as shown in Figure 1. A pair of singlet signals arising
1
When 3a was recrystallized from acetone, prism crystals
which include acetone molecules inside the crystals were
obtained, and on standing the crystals changed gradually from
clear to opaque crystals upon losing acetone molecules. The
crystal structure of 3a was determined by a single-crystal
X-ray analysis (Figure 3).9 Calixarene 3a was found to have
a cone conformation with a C2 symmetry and to form a 1:5
clathrate with acetone molecules. Four acetone molecules
are captured in the channel of the crystal lattice, and one
acetone molecule is held inside the molecular cavity of 3a
with the CH3 group pointing into the cavity.10 The acetone
molecule within the cavity exists in a position where a
CH3-π interaction between one of the CH3 groups of acetone
and the aromatic ring of the calixarene could be present.11
In fact, the CH3 carbon of acetone is situated at a distance
of 3.54(4) Å above the center of the phenyl ring of 3a. There
are two intramolecular OH‚‚‚O hydrogen bonds between the
phenolic hydroxyl groups of the calixarene ring and the
Figure 1. 1H NMR spectrum (400 MHz) of 3a in THF-d8 at 20
°C.
from the tert-butyl protons and a pair of doublet signals from
the ArCH2Ar methylene protons strongly suggest that 3a has
a C2 symmetry and a cone conformation.8 The Hb and Hc
proton signals gave the same resonance at 8.36 ppm. This
indicates that the galloyl groups in 3a undergoes rapid
rotation on a NMR time scale at 20 °C. The chemical shifts
of the OH proton signals of the galloyl groups and the
calixarene skeleton varied with loss of temperature (Figure
2). The signal arising from the Hb and Hc protons at 8.36
ppm at 20 °C shifted downfield upon cooling to -40 °C
(9) Crystal data for C58H64O12‚5(C3H6O). 3a: M ) 1243.54, tetragonal,
a ) b ) 13.9382(3) Å, c ) 35.3234(8) Å, V ) 6862.4(3) Å3, T ) -100
°C, space group P41212 (No. 92), Z ) 4, µ(Cu KR) ) 6.89 cm-1, Dc )
1.204 g cm-3, 69324 reflections measured, 1216 unique (Rint ) 0.039),
residuals of R ) 0.069 and Rw ) 0.102 were obtained from the 2652
reflections with I > 2.00σ(I) and 408 variable parameters used in the
refinement.
(10) Calixarene-acetone clathrates, see: Ungaro, R.; Pochini, A.;
Andreetti, G. D.; Sangermano, V. J. Chem. Soc., Perkin Trans. 2 1984,
1979.
(11) For CH3-π interactions between the methyl groups of the host and
the aromatic moiety of pyridine, see: Andreetti, D.; Ori, O.; Ugozzoli, F.;
Alfieri, C.; Pochini, A.; Ungaro, R. J. Inclusion Phenom. 1988, 6, 523.
(7) For a similar selective esterification, see: See, K. A.; Fronczek, F.
R.; Watson, W. H.; Kashyap, R. P.; Gutsche, C. D. J. Org. Chem. 1991,
56, 7256.
(8) Mogck, O.; Bo¨hmer, V.; Furguson, G.; Vogt, W. J. Chem. Soc.,
Perkin Trans. 1 1996, 1711.
780
Org. Lett., Vol. 2, No. 6, 2000

Å. The OHc group is placed in a position where significant
nonbonded contacts are observed between the OHc group
and the aromatic ring of the galloyl groups facing each other,
1
which is consistent with the model predicted from the H
NMR spectral data. The hydroxyl oxygen O(6) is situated
in a position which is 3.247(7) Å above the least-squares
plane of the facing phenyl ring of the galloyl group. This
interaction makes it possible to exert an OH-π interaction.13
In the solid state, it can be assumed that hydrogen bonding
between the OH group of the galloyl group and the acetone
molecule is preferred.
The interaction with metal ions was evaluated by means
of electronic spectra. Figure 4 shows the electronic spectra
Figure 4. Electronic spectra of 3a in EtOH in the presence of
metal nitrates. [3a] ) 1.0 × 10-5 mol dm-3, [M(NO3)n] ) 1.0 ×
10-3 mol dm-3
.
of 3a in ethanol solutions in the presence of several metal
nitrates. Upon adding Mg+, Ca+, and Al3+ ions, the absor-
bances at around 280 nm decreased with slight bathochromic
shifts and new absorption bands appeared at around 340,
330, and 315 nm, respectively. Furthermore, upon adding
Ag+ ion, the absorbance changed markedly and a new strong
band was observed at around 420 nm. On the other hand,
when the monoester 3b was used, such a spectral change
was not observed upon adding Ag+ ion. These spectral
changes for 3a are thought to arise from the structure of the
calixarene in which the facing galloyl groups are located in
a position of nonbonded close contact.
Figure 3. Top (a) and side (b) views of the X-ray crystallographic
structure of 3a (30% probability). Hydrogen atoms have been
omitted for clarity. In the top view, acetone molecules in the channel
of the crystal latice have been omitted for clarity. Close contacts
(Å): C(20)‚‚‚C(20*), 3.30(1); O(1)‚‚‚O(2), 2.871(5); O(6)‚‚‚O(8),
2.760(7); O(4)‚‚‚O(9), 2.74(1); O(5)‚‚‚O(5*), 3.224(8). For example,
O(1*) and O(2*) are related to O(1) and O(2), respectively, by
2-fold symmetry.
Acknowledgment. This research was performed through
Special Coordination Funds for Promoting Science and
Technology (Leading Research Utilizing Potential of Re-
gional Science and Technology) of the Science and Technol-
ogy Agency of the Japanese Government.
proximal ether O atoms in which the O(1)‚‚‚O(2) distance
is 2.871(5) Å. These hydrogen bonds were found for many
1,3-substituted calix[4]arenes.12 The four hydroxyl groups
of the galloyl groups form intermolecular hydrogen bonds
with four acetone molecules, and the distance of O(6)‚‚‚O(8)
is 2.760(7) Å and that of O(4)‚‚‚O(9) is 2.74(1) Å. There is
weak hydrogen bonding between the OHa groups of facing
galloyl groups, and the distance of O(5)‚‚‚O(5*) is 3.224(8)
Supporting Information Available: Experimental details
for compounds prepared and crystallographic data and
structure refinement details for 3a. This material is available
free of charge via the Internet at http://pubs.acs.org
OL9913993
(12) (a) Bo¨hmer, V.; Ferguson, G.; Gallagher, J. F.; Lough, A. J.;
Mckervey, M. A.; Madigan, E.; Moran, M. B.; Fhillips, J.; Williams, G. J.
Chem. Soc., Perkin Trans. 1 1993, 1521. (b) Collins, E. M.; Mckervey, M.
A.; Madigan, E.; Moran, M. B.; Owens, M.; Ferguson, G.; Harris, S. J. J.
Chem. Soc., Perkin Trans. 1 1991, 3137.
(13) For OH-π interaction between H2O and aromatic π electrons, see:
Atwood, J. L.; Hamada, F.; Robinson, K. D.; Orr, G. W.; Vincent, R. L.
Nature 1991, 349, 683.
Org. Lett., Vol. 2, No. 6, 2000
781