Photoswitchable calix[4]arenes bearing dihydroacridine substituents at the upper rim

Article abstract of DOI:10.1016/j.tet.2007.06.126

Eight new calix[4]arene host molecules bearing acridinium or the corresponding dihydroacridine substituents have been prepared. ¹H NMR and electrochemical studies reveal that the acridinium substituents block the host cavity. Both photochemical

Full text of DOI:10.1016/j.tet.2007.06.126

Tetrahedron 63 (2007) 10778–10787
Photoswitchable calix[4]arenes bearing dihydroacridine
substituents at the upper rim
*
Lutz Grubert and Werner Abraham
Institute for Chemistry, Humboldt-University Berlin, Brook-Taylor-Street 2, D-12489 Berlin, Germany
Received 26 April 2007; revised 30 May 2007; accepted 4 June 2007
Available online 20 July 2007
Abstract—Eight new calix[4]arene host molecules bearing acridinium or the corresponding dihydroacridine substituents have been prepared.
1H NMR and electrochemical studies reveal that the acridinium substituents block the host cavity. Both photochemical and chemical switch-
ing between acridinium and dihydroacridine hosts are demonstrated.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
Calixarenes1 are an important class of building blocks for
O
supramolecular assemblies2 and molecular recognition,
hν
CH3O
and are widely used as receptors for inorganic cations3 and
Δ
N
N
I
anions,4 as well as organic cations5 and neutral compounds.6
Molecular recognition arises from different forces acting
upon complementary faces of the calixarene host and the
guest inside the cavity. Endo-cavity inclusion complexes
with organic cations such as quaternary ammonium ions
and the iminium and tropylium ions may be favored by cat-
ion–p-interaction and p-stacking.7 Switchable hosts such as
calixarenes and resorcarenes, which are able to change their
structures in response to an external stimulus, are of partic-
ular interest.8–10 A photoswitchable resorc[4]arene based on
[4+4] cycloaddition of anthracene has been studied recently
by means of single-molecule force spectroscopy.11 As illus-
trated by this system, inputs in the form of photons have at
least two advantages. (1) Waste products are not formed.
(2) Molecules immobilized on a surface are addressable.
II
Figure 1. The photoswitch acridane/acridiniummethoxide.
solvent.12,13 It may be noted that I (lmax 320, 285 nm) and
II (lmax 425 nm) represent a photochromic system (Fig. 1).
Due to the planarity of the acridinium ion formed from the
acridane compound, we anticipated that strong interactions
would occur between two acridinium units bound to the up-
per rim of a cone calix[4]arene. Examination of CPK space
filling models in addition to model calculations indicated
that the acridinium ring should be strongly twisted relative
to the aryl group of the calixarene, so that one part should
be oriented into the cavity.
We became interested in introducing a photoswitch into
calix[4]arenas, which could reversibly alternate between a
partially closed and an open cavity. Concomitantly, as the
structure interchanges between electron donor and acceptor
character, the electronic properties at the upper rim should
change drastically. The system 9-alkoxy acridane (dihydro-
acridine) of the type I, which undergoes photoheterolysis in
the photoexcited state to give an acridinium salt II (Fig. 1),11
was expected to match these requirements. In protic solvents
(alcohols), the system is reset by attack of the alkoxide on
the acridinium ion. The rate constant of this thermal back
reaction is strongly dependent on the properties of the
Here we report the synthesis and conformation of calix[4]-
arenes substituted at the upper rim with acridane and acridi-
nium units.
Photochemical experiments have been performed in order to
explore the reversibility of the switching process.
2. Results and discussion
2.1. Synthesis
2.1.1. Acridinium calix[4]arenes. Both calix[4]arenes with
a cone conformation and a fixed 1,3-alternate conformation
were converted into acridinium substituted compounds. The
syntheses are outlined in Schemes 1 and 2.
Keywords: Calixarene; Acridinium salts; Acridanes; Photoswitch.
* Corresponding author. Tel.: +49 30 2093 7348; fax: +49 30 2093 7266;
e-mail: abraham@chemie.hu-berlin.de
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.06.126

L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
10779
CH3
CH3
N+
CH3
N+
i
BuLi
N+
O
ii
Br
Br
N
CH3
iii NH4PF6
+
O
O
O
O
O
O
-
-
O
O
O
O
PF6
O
2 PF6
O
2
1
3
30%
Scheme 1. Synthesis of calixarenes 2 and 3 having a cone conformation.
25%
N+
N+
i
2 BuLi, - 78 °C
N
Br
Br
O
ii 2
O
O
O
O
O
O
iii NH4PF6
THF
O
O
−
2 PF6
O
O
O
O
O
O
n
n
5a n = 1
5b n = 2
5c n = 3
4a n = 1
4b n = 2
4c n = 3
Scheme 2. Synthesis 1,3-alternate calixcrowns 5.
The initial acridane compounds were converted to the acri-
dinium compounds due to the acidic conditions that pre-
vailed during the column chromatography. The yield of the
disubstituted compound 3 can be increased with longer reac-
tion times. To create hosts with two binding sites and a
nearly square cavity, the 1,3-alternate calixcrowns 5 were
synthesized (Scheme 2). For purpose of comparison, com-
pound 6 (Scheme 3) was also studied.
2.1.2. Acridane calix[4]arenes. In the presence of K2CO3,
nucleophiles such as methanol and ethanol converted
the acridinium calixarenes to the corresponding acridane
RO
OR
N
O
N
N
OR
N
RO
O
O
ROH/K2CO3
ROH/K2CO3
O
3
5a-5c
O
O
O
O
O
O
O
O
n
7
7a: R = Me
7b: R = Et
8a: n = 0, R = Me
9a: n = 1, R = Me
9b: n = 1, R = Et
10a: n = 2, R = Me
10b: n = 2, R = Et
OMe
OMe
MeOH/K2CO3
OMe
-
PF6
N+
N
6
11
Scheme 3. Syntheses of acridane calix[4]arenes and of a model acridane.

10780
L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
8.03
N+
7.27
N+
8.63
8.46
6.72
8.06
N+
7.85
7.93
8.24
8.45
8.28
7.81
6.99
6.19
N+
N+
OMe
8.55
8.46
7.97
O
O
5.86
8.08
O
O
_
PF6
8.10
8.57
8.26
O
O
O
7.84
8.35
-
O
O
2 PF6
O
O
O
O
-
_
O
O
N+
2 PF6
PF6
O
O
n
6
2
5a-5c
3
Scheme 4. Proton resonances of acridinium compounds (curved arrows mark NOE’s).
compounds 7–9 (Scheme 3). The model compound 6 was
similarly converted into 11.
2.2.2. Acridane calix[4]arenes. The molecular structure of
7 (Fig. 2) revealed by a crystal structure determination14
shows that an open cavity results when the acridinium
substituents are converted to acridanes. Only one set of
four signals was observed for the proton resonances of the
acridane units (Scheme 5).
2.2. Conformation
1
2.2.1. Acridinium calix[4]arenes. The H NMR spectrum
of the monofunctionalised calixarene 2 showed four reso-
nances typical of the flanking phenyl group protons of the
acridinium unit. However, in the spectra of the calix[4]-
arenes 3 and 5 with two substituents at the upper rim, two
such sets were observed, one set closely matching that of
the model compound 6 but the other showing distinct upfield
shifts (Scheme 4), though these were smaller for the 1,3-
alternate calixarenes 5 than for the cone 3. ROESY measure-
ments showed that a given acridinium ring was associated
with both sets of resonances. This finding clearly demon-
strated that one part of the acridinium unit points to the inner
p-basic sphere of the calixarene cavity, which shields the
acridinium protons of the inserted phenyl ring. The protons
of the outer ring showed slight downfield shifts due to their
location at the edge of the aromatic core. Even in the rela-
tively open cone conformation of 3, it appears that rotation
about the bond from the acridinium unit to the calixarene
phenyl ring is slow on the NMR time scale and thus, in
both 3 and 5, the acridinium units block the calixarene cav-
ity. In 5, there is little evidence that the crown binding site is
significantly influenced by any effects of the acridinium
substituents.
3.50
0.6
7.15
N
N
1.16
7.3
3.23
O
O
O
3.09
1.26
7.02
O
7.43
O
3.71
3.46
3.6
O
O
7.18
O
O
6.87
O
O
3.7
Scheme 5. Proton resonances (CD3CN, d, ppm) of the acridane calix[4]-
arene 5c and NOE’s (curved arrows) observed in its ROESY spectrum.
2.3. Equilibrium in methanol solution
Acridanes are ionogenic compounds in protic solvents
(Scheme 6) although the equilibrium involved has not
been studied previously.
R
R
OMe
MeOH
+ MeO- (1)
N
R
N+
R
OMe
(2)
MeOH +
+ HPF6
N+
N
-
PF6
R = calix[4]arene
Scheme 6. Equilibria observed in methanol solution.
The first equation describes the dissociation of acridanes in
methanol solution. The higher stability of the acridinium
Figure 2. Molecular structure for calixarene 7 in the solid state.

L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
10781
Table 1. UV–vis absorption maxima and the acridane concentration at the
equilibrium in methanol solution
6. However, in calixarenes 3 and 5 the first acridinium sub-
stituent was reduced at a similar potential as measured for 2,
but the reduction of the second acridinium unit could only be
accomplished at a potential 0.2 V more negative (Scheme 7).
This indicates that the acridinium radical formed in the first
reduction step interacts with the remaining acridinium unit.
Compound
lmax of the
acridinium [nm]
% Acridane
at equilibrium
7a
8a
9a
10a
5a
5b
5c
449
430
449
451
436
449
451
26
84
49
17
35
7
2.4.2. Acridane calix[4]arenes. The cyclic voltammogram
of the model compound 11 exhibited an oxidation wave at
0.92 V, which showed a peak separation consistent with re-
versibility only at scan rates above 10 V sꢀ1. This we attri-
bute to the initial one-electron oxidation being followed by
loss of methoxy radical and the formation of an acridinium
ion. To support this assumption the electrochemical reaction
was performed at a constant anode potential slightly more
positive than the oxidation peak potential. The total charge
consumption of 1 F molꢀ1 resulted in the conversion of the
acridane into the corresponding acridinium salt.
3
compounds leads to their formation according to equilibrium
(1) in Scheme 6. The concentrations of the acridane com-
pounds in methanol solution at equilibrium with the corre-
sponding acridinium species are given in Table 1. Ethanol
produces quite different equilibria, while 10b gives 83%
acridinium at equilibrium in methanol, it gives only 8% in
ethanol.
The redox behavior of the calixarene 10a was similar to that
of 11 but the peak observed at 0.87 V remained irreversible
in character even at a scan rate of 100 V sꢀ1. Current mea-
surements showed the peak to correspond to a two-electron
process, with both acridane sites being oxidized at the same
potential to give the acridinium calixarene 5. Thus, unlike
calixarene 3, 10a undergoes essentially independent reac-
tions at the two sites (Scheme 8).
The acridinium calixarenes react only to a small extent with
methanol to give the corresponding acridane (Eq. 2 in
Scheme 6). Therefore the equilibrium has to be displaced
by adding K2CO3 in the synthesis of acridane calixarenes.
The steric strain present in the acridinium calix[4]arenes 3
and 5a–5c is manifested in the different concentrations of
the acridane compounds obtained from 7–9 at equilibrium
(1) in methanol solution (Table 1).
2.5. Switching cycle
The shorter chain at the lower rim results in more steric
strain at the upper rim and, therefore, more acridane is
present at equilibrium (8a in Table 1). Also the acridinium
calixarene 5a forms in methanol solution more acridane at
equilibrium than 5b and 5c because the steric strain is
reduced due to the conversion into the acridane.
2.5.1. Photoreaction. All the acridane compounds investi-
gated undergo photoheterolysis in protic solvents by excita-
tion with 313 nm light, giving the corresponding acridinium
compounds. Spectra recorded after consecutive irradiations
showed two or three isosbestic points indicating a single-
step reaction (Fig. 3).
2.4. Electrochemistry
The lifetime of the generated acridinium alcoholate depends
strongly on the solvent. For example, the lifetime of the
acridinium ethanolate 5c EtOꢀ is 123 s in methanol, 13 min
in ethanol, and 50 min in a mixture of acetonitrile and etha-
nol 1:1. The acridane calixarenes are completely recovered
in the thermal reaction (see Scheme 9).
2.4.1. Acridinium calix[4]arenes. 9-Arylacridinium ions
combine donor and acceptor units within one entity. Thus,
in the excited state, long-lived charge separated states
can be formed by intramolecular electron transfer.15 Since
acridinium species usually undergo reversible reduction pro-
cesses, cyclic voltammetry was used to explore the electron
acceptor properties of the acridinium calixarenes, in partic-
ular to see if the proximity of the two acridinium substituents
at the upper rim influenced the redox properties. Comparison
of the peak potentials of compounds 2 and 6 indicated only
a slight influence of the calixarene scaffold on the reduction
properties. The acridinium unit within the calixarene 2 was
shifted by ꢀ50 mV (ꢀ0.74 V vs ꢀ0.69 V) relative to that in
2.5.2. Chemical switching. The acridane calixarenes can
also be converted into acridinium ions by addition of acids
such as trifluoroacetic acid. The back reaction reverting to
the acridane compounds can be performed upon addition
of a base such as di-iso-propylethylamine or NaHCO3
(Scheme 9) or K2CO3 as in the syntheses. Complexation
studies of the acridane and acridinium hosts are currently
in progress.
N+
N+
N+
N
N
N
-0.66 V
-0.60 V
-0.86 V
-0.79 V
O
O
O
O
O
O
O
O
O
O
O
O
Scheme 7. Two different reduction steps in compound 3.

10782
L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
N+
MeO
N+
MeO
OMe
OMe
N
N
O
O
N
N
Pt electrode
O
O
O
MeCN/Bu4NPF6
O
O
O
O
O
O
- 2 e
- 2 MeO
O
O
O
O
O
-
2 PF6
O
O
O
O
O
O
O
O
O
O
O
Scheme 8. Electrochemical oxidation of 10a.
solvents were dried according to standard procedures. Com-
pound 4b was synthesized according to the literature.16 Col-
umn chromatographies (CC) were carried out on 200 mesh
silica gel (Merck). Melting points (mp) were determined
with a Boetius heating microscope. ESI mass spectroscopy
was carried out on LTQ FT, Finnigan MAT (Bremen, Ger-
many) equipped with an electrospray ion source (Thermo
Electron). NMR spectra were recorded on a Bruker DPX
300 (300 MHz), a Bruker Advance 400 (400 MHz), and
a Bruker AMX 600 (600 MHz) instruments. The proton sig-
nals were attributed to the different subunits with the aid of
two-dimensional NMR spectroscopy, such as C–H COSY,
H–H COSY, and ROESY. UV–vis measurements were per-
formed with a Shimadzu UV 2101 PC spectrometer. Irradi-
ation of the calixarene solutions were carried out with
a conventional mercury arc (HBO 500 or HBO 200) com-
bined with a cut-off filter of 300 nm or metal interference
filters. The thermal reactions were followed by UV–vis
spectroscopy using the kinetics-program of the spectro-
meter. The absorption decay curves at the wavelength of
360 nm were analysed by nonlinear regression fits (Origin
6.0, Microcal Software, Inc.). The relative concentrations
of the acridane calixarenes and the acridinium calixarenes
at equilibrium in methanol solution were determined by
the absorbance at 450 nm (only the acridinium compound
absorbs light) before and after addition of trifluoroacetic
acid.
Figure 3. UV–vis spectra recorded after consecutive irradiation periods
(10 s to 8 min) of calixarene 10b in 1-propanol solution (3.7ꢂ10ꢀ5 M).
3. Conclusions
4.2. Synthesis
Calix[4]arenes bearing two acridane units at the upper rim
can be switched reversibly to the corresponding acridinium
compounds by photochemical followed by thermal reactions
and by thermal reactions alone. The acridinium units are
positioned in close proximity and are twisted relative to
the calixarene phenyl group to which they are attached,
thus blocking the cavity. In contrast, the acridane units are
bound with an sp3 carbon at the calixarene scaffold, and
accordingly, the cavity is more open. Photochemical and
thermal reactions thus provide a means of switching between
a closed and an open conformation.
4.2.1. 11,23-Dibromo-25,27-dibenzyloxy-26,28-bis-
(propyloxy)calix[4]arene (1). NaH (1.6 g, 60% in paraffin
wax, 40 mmol) was added to 11,23-dibromo-25,27-
dihydroxy-26,28-bis(propyloxy)calix[4]arene17
(6.66 g,
10 mmol) dissolved in a mixture of THF (200 mL) and
DMF (30 mL). After stirring at room temperature for 1 h,
benzylbromide (8.5 g, 40 mmol) in THF (15 mL) was added
dropwise. The mixture was stirred for 2 h at room tempera-
ture and for 1 h at reflux. After cooling, HCl (1 M, 50 mL)
was added. The separated organic phase was washed with
water (50 mL), dried, and evaporated in vacuo. The remain-
ing residue was treated with methanol to provide 1 (7.1 g,
84%), mp 162–165 ꢁC. Anal. Calcd for C48H46Br2O4
(846.69): C, 68.09; H, 5.48; Br, 18.87. Found: C, 68.32; H,
5.69; Br, 18.60. 1H NMR (400 MHz, CDCl3, TMS):
d¼7.42 (m, 4H, –OCH2–C6H5), 7.34 (m, 6H, –OCH2–
C6H5), 6.85 (d, J¼7.0 Hz, 4H, H-4, 6, 16, 18), 6.78 (t,
J¼7 Hz, 2H, H-5, 17), 6.55 (s, 4H, H-10, 12, 22, 24), 4.82
4. Experimental
4.1. General
Commercially available chemicals and solvents (UVASOL,
Merck) were used as received unless otherwise noted;

L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
10783
MeO
OMe
N
O
N
O
O
O
O
O
O
hν
Δ
O
O
N
N+
MeO
N+
OMe
O
N
O
protic solvents
O
O
O
O
-
O
2 MeO
O
O
O
O
O
O
O
O
O
O
O
N+
MeO
N+
OMe
N
O
N
O
O
O
O
O
H+
+ MeOH
O
O
O
-H+
O
O
O
O
O
O
O
O
O
Scheme 9. Switching between an acridane calix[4]arene and the corresponding acridinium calix[4]arene.
(s, 4H, OCH2–C6H5), 4.34 (d, J¼13 Hz, 4H, H-2, 8, 14, 20),
3.74 (m, 4H, –OCH2CH2CH3), 3.05 (d, J¼13 Hz, 4H, H-2,
8, 14, 20), 1.66 (m, 4H, –OCH2CH2CH3), 0.64 (t, J¼7 Hz,
6H, –OCH2CH2CH3). 13C NMR (100 MHz, CDCl3, TMS):
d¼157.0 (C-25, C-27), 154.1 (C-26, C-28), 137.2, 136.6
(C-1, 9, 13, 21), 135.2, 130.6, 129.3, 128.8, 128.2, 128.1,
122.6, 115.4 (C-11, 23), 76.7 (–OCH2CH2CH3), 31.0 (C-2,
8, 14, 20), 22.9 (–OCH2CH2CH3), 9.7 (–OCH2CH2CH3).
water was neutral. The yellow solid was dissolved in methanol
and treated with NH4PF6. The resulting solid was isolated,
and washed with chloroform in order to dissolve compound
2. The insoluble solid was purified by CC (acetonitrile, aque-
ous solution of NH4PF6 (5%) 20:1) to provide 3 (1.36 g,
40%), mp 245–250 ꢁC. Anal. C76H68F12N2O4P2 (1363.33);
HRMS (ESI): [MꢀPFꢀ6 ]+ calcd for C76H68F6N2O4P:
1217.4821, found: 1217.4843; [Mꢀ2PFꢀ6 ]2+ calcd
for C76H68N2O4: 536.2589, found: 536.2586. 1H NMR
(600 MHz, CD3CN, TMS): d¼acridinium: 8.55 (d, J¼
4.2.2. 11,23-Di-(N-methylacridinium-9-yl)-25,27-dibenz-
yloxy-26,28-bis(propyloxy)calix[4]arene bishexafluo-
rophosphate (2) and 11-(N-methylacridinium-9-yl)-
25,27-dibenzyloxy-26,28-bis(propyloxy)calix[4]arene
hexafluorophosphate (3). A solution of 1 (2.1 g, 2.5 mmol)
in dry THF (150 mL) was cooled to ꢀ78 ꢁC. A solution of
butyllithium (BuLi) (3.8 mL, 1.6 M in hexane, 5.7 mmol)
in THF (6 mL) was added dropwise. The reaction mixture
was stirred at ꢀ78 ꢁC for 0.5 h. N-Methylacridone (1.1 g,
5.25 mmol) was added. The reaction mixture was slowly
warmed to room temperature under argon. After stirring
for 8 h at room temperature water (10 mL) was added. The
mixture was filtered and the solvent removed in vacuo.
The crude product was washed with water until the wash
3
3
4
9 Hz, 2H, H-5), 8.46 (ddd, J¼9 Hz, J¼8 Hz, J¼1 Hz,
2H, H-6), 8.26 (dd, 3J¼9 Hz, 4J¼1 Hz, 2H, H-8), 7.97
(ddd, 3J¼9 Hz, 3J¼8 Hz, 4J¼1 Hz, 2H, H-7), 7.85 (d,
3
4
J¼9 Hz, 2H, H-4), 6.99 (dt, J¼9 Hz, J¼1 Hz, 2H, H-3),
3
4
6.19 (t, J¼8 Hz, 2H, H-2), 5.86 (dd, J¼8 Hz, J¼1 Hz,
2H, H-1); calixarene: 7.68 (d, J¼7 Hz, 4H, bzl-ortho),
7.51 (t, J¼7 Hz, 4H, bzl-meta), 7.47 (t, J¼7 Hz, 2H, bzl-
para), 7.22 (d, J¼8 Hz, 4H, H-4, 5, 16, 18), 6.80 (t,
J¼8 Hz, 2H, H-5, 17), 6.75 (s, 4H, H-10, 12, 22, 24), 4.98
(s, 4H, bzl-CH2), 4.75 (d, J¼13 Hz, 4H, H-2, 8, 14, 20 axial),
3.98 (m, 4H, –OCH2CH2CH3), 3.47 (d, J¼13 Hz, 4H, H-2,
8, 14, 20 equatorial), 1.81 (m, 4H, –OCH2CH2CH3), 0.63
(t, J¼7.5 Hz, 6H, –OCH2CH2CH3). 13C NMR (100 MHz,

10784
L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
CDCl3, TMS) d¼160.3 (C, 2C), 157.1 (C, 2C), 156.9 (C,
2C), 140.9 (C, 2C), 139.7 (C, 2C), 140.9 (CH, 2C), 136.5
(C, 2C), 136.3 (C, 4C), 135.4 (CH, 2C), 135.0 (C, 4C),
132.4 (CH, 2C), 130.7 (CH, 2C), 129.6 (CH, 4C), 129.3
(CH, 2C), 128.8 (CH, 2C), 128.2 (CH, 4C), 127.7 (CH,
2C), 125.3 (CH, 2C), 125.2 (C, 2C), 124.6 (C, 2C), 123.2
(C, 2C), 122.8 (CH, 2C), 117.9 (CH, 2C), 116.5 (CH,
2C), 78.0 (2C, –OCH2CH2CH3), 76.6 (2C, –OCH2C6H5),
38.2 (N+–CH3), 30.3 (CH2, 4C, C-2, 8, 14, 20), 22.5
(–OCH2CH2CH3), 8.6 (–OCH2CH2CH3). The chloroform
solution containing the calixarene 2 was evaporated. The re-
maining solid was purified by CC (acetonitrile, aqueous so-
lution of NH4PF6 (5%) 20:1) to provide more 3 (0.31 g, 9%)
and 2 (0.65 g, 25%) as orange crystals, mp 240–242 ꢁC.
Anal. C62H58F6NO4P (1026.12); HRMS (ESI): [MꢀPFꢀ6 ]+
calcd for C62H58NO4: 880.4366, found: 880.4343. 1H
NMR (400 MHz, CDCl3, TMS): d¼acridinium: 8.45 (m,
2H, H-4, 5), 8.28 (m, 2H, H-3, 6), 8.06 (m, 2H, H-1, 8),
7.81 (m, 2H, H-2, 7); calixarene: 7.58 (m, 6H), 7.41 (m,
12H), 7.17 (d, J¼7.5 Hz, 2H, H-4, 18), 7.00 (d, J¼7.5 Hz,
2H, H-6, 16), 6.75 (t, J¼7.5 Hz, 2H, H-5, 17), 6.63 (s, 2H,
H-10, 12), 6.47 (d, J¼7.5 Hz, 2H, H-22, 24), 6.13 (t, J¼
7.5 Hz, 1H, H-23), 4.90 (s, 2H, –OCH2C6H5), 4.70 (s, 2H,
–OCH2C6H5), 4.66 (s, 3H, N+–CH3), 4.62 (d, J¼12.8 Hz,
2H, H-8, 14), 4.53 (d, J¼7.5 Hz, 2H, H-2, 20), 3.85 (m, 4H,
–OCH2CH2CH3), 3.30 (d, J¼12.8 Hz, 2H, H-8, 14), 3.24 (d,
J¼7.5 Hz, 2H, H-2, 20), 1.68 (m, 4H, –OCH2CH2CH3),
0.53 (t, 6H, –OCH2CH2CH3). 13C NMR (100 MHz, CDCl3,
TMS): d¼157.4 (C), 150.4 (CH), 141.3 (C), 137.9 (CH),
137.8 (CH), 136.6 (C), 135.6 (C), 134.8 (C), 133.6 (C),
130.9 (CH), 129.6 (CH), 129.4 (CH), 128.8 (CH), 128.2
(CH), 128.1 (CH), 128.0 (CH), 127.2 (CH), 126.0 (C), 122.2
(CH), 122.0 (CH), 117.9 (CH), 77.7 (–OCH2C6H5), 77.5
(–OCH2C6H5), 76.3 (–OCH2CH2CH3), 38.2 (N+–CH3), 30.3
(–OCH2CH2CH3), 22.4 (CH2), 8.6 (–OCH2CH2CH3).
4.2.4. 11,23-Dibromo-25,27-dihydroxy-26,28-bis(propyl-
oxy)calix[4]arene crown-5, 1,3-alternate (4c). 11,23-Di-
bromo-25,27-dihydroxy-26,28-bis(propyloxy)calix[4]arene
(3.33 g, 5 mmol) and Cs2CO3 (6 g, 18.5 mmol) suspended in
MeCN (800 mL) were reacted under Ar with tetraethylene
glycol ditosylate (3.25 g, 5.5 mmol). The violet suspension
was stirred for 12 h at reflux and 12 h at room temperature.
The solvent was evaporated in vacuo. The remaining residue
was treated with HCl (10%, 150 mL) and dichloromethane
(150 mL). The organic phase was separated, washed with
water, and dried (MgSO4). After removal of the solvent in
vacuo, the solid residue was treated two times with methanol
(75 mL) to give 4c, 3.75 g (82%), mp 153–158 ꢁC. Anal.
Calcd for C46H56Br2O9 (912.76): C, 60.53; H, 6.18. Found:
C, 60.92; H, 6.06. 1H NMR (400 MHz, CDCl3, TMS):
d¼7.11 (s, 4H, H-10, 12, 22, 24), 7.10 (d, 4H, H-4, 6, 16,
18), 6.76 (t, 2H, H-5, 17), 3.71–3.55 (m, 36H, H-2, 8,
14, 20, CH2-crown and –OCH2CH2CH3), 1.65 (m, 4H,
–OCH2CH2CH3), 0.98 (t, 6H, –OCH2CH2CH3). 13C NMR
(100 MHz, CDCl3, TMS): d¼156.4 (C-25, C-27), 155.1
(C-26, C-27), 135.6 (C-1, 9, 13, 21), 132.8 (C-3, 7, 15,
19), 132.6 (C-10, 12, 22, 24), 130.5 (C-4, 6, 16, 18), 122.1
(C-5, C-17), 114.7 (C-11, C-23), 73.2 (–OCH2CH2CH3),
71.2, 71.1, 71.0, 70.9, 70.8, 70.5 (each 2C, CH2-
crown), 36.4 (C-2, 8, 14, 20), 23.4 (–OCH2CH2CH3), 10.6
(–OCH2CH2CH3).
4.3. Calix[4]arenes 5a–5c: general procedure
Compound 4 (2.5 mmol) was dissolved in dry THF
(150 mL). n-BuLi (1.6 M in n-hexane, 3.75 mL, 6 mmol)
was added dropwise at ꢀ78 ꢁC under an argon atmosphere.
After stirring for 0.5 h N-methylacridone (1.09 g) in THF
(50 mL) was added dropwise. After warming the solution
to room temperature, stirring was continued for 3 h. The re-
action was quenched with water (1 mL). The solvent was
evaporated in vacuo and the residue was dissolved in meth-
anol (150 mL). The solution was then treated with NH4PF6
(2 g). After stirring for 0.5 h, the solvent was removed in va-
cuo. The resulting solid was three times washed with water
and then three times with methyl-tert-butylether (MTBE,
150 mL). The crude products were purified by CC (aceto-
nitrile, aqueous NH4PF6 solution). In order to remove com-
plexed NH4PF6, the acridinium calixarenes were converted
to the corresponding acridanes. Therefore the solid obtained
after chromatography was dissolved in acetonitrile (50 mL)
and ethanol (4 mL) and K2CO3 (0.3 g) was added. The sus-
pension was stirred overnight. The solid was filtered and the
solvent was evaporated in vacuo. The remaining solid was
treated with dry chloroform (20 mL). The suspension was
filtered and the solvent was removed in vacuo. The remain-
ing solid was dissolved in acetonitrile (50 mL). The acridi-
nium salt was precipitated by addition of HPF6 (0.2 mL).
4.2.3. 11,23-Dibromo-25,27-dihydroxy-26,28-bis(propyl-
oxy)calix[4]arene crown-7, 1,3-alternate (4a). 11,23-Di-
bromo-25,27-dihydroxy-26,28-bis(propyloxy)calix[4]arene
(3.33 g, 5 mmol) and Cs2CO3 (6 g, 18.5 mmol) suspended in
MeCN (800 mL) were reacted under Ar with hexaethylene
glycol ditosylate (2.75 g, 5.5 mmol). The violet suspension
was stirred for 12 h at reflux and 12 h at room temperature.
The solvent was evaporated in vacuo. The remaining residue
was treated with HCl (10%, 150 mL) and dichloromethane
(150 mL). The organic phase was separated, washed with
water, and dried (MgSO4). After removal of the solvent in
vacuo, the solid residue was treated two times with methanol
(75 mL) to give 4a, 2.4 g (58%), mp 212–228 ꢁC. Anal.
Calcd for C42H48Br2O7 (824.65): C, 61.17; H, 5.87. Found:
1
C, 60.62; H, 5.84. H NMR (400 MHz, CDCl3, TMS): d¼
7.15 (s, 4H, H-10, 12, 22, 24), 7.05 (d, J¼7.3 Hz, 4H,
H-4, 6, 16, 18), 6.84 (t, J¼7.3 Hz, 2H, H-5, H-17), 3.82–
3.75 (m, 8H, 4ꢂCH2-crown), 3.51 (m, 8H, 4ꢂCH2-crown),
3.43 (t, 4H, –OCH2CH2CH3), 3.20 (m, 4H, CH2-calixarene),
3.13 (m, 4H, CH2-calixarene), 1.28 (m, 4H, –OCH2CH2CH3),
0.76 (t, 6H, –OCH2CH2CH3). 13C NMR (100 MHz, CDCl3,
TMS): d¼156.9 (C-25, C-27), 155.1 (C-26, C-27), 136.2
(C-1, 9, 13, 21), 133.7 (C-3, 7, 15, 19), 132.1 (C-10, 12,
22, 24), 129.6 (C-4, 6, 16, 18), 122.7 (C-5, C-17), 115.0
(C-11, C-23), 72.5 (–OCH2CH2CH3), 72.0, 70.4, 70.0,
68.9 (each 2C, CH2-crown-7), 37.8 (C-2, 8, 14, 20), 22.4
(–OCH2CH2CH3), 10.1 (–OCH2CH2CH3).
4.3.1. 11,23-Di-(N-methylacridinium-9-yl)-25,27-di-
hydroxy-26,28-bis(propyloxy)calix[4]arene-crown-5,
1,3-alternate bishexafluorophosphate (5a). Compound
5a was purified by CC (acetonitrile, aqueous solution of
NH4PF6 (2.5%) 20:1); yellow crystals, 0.215 g (8%), mp
204–205 ꢁC. Anal. C70H70F12N2O7P2 (1341.28); HRMS
(ESI): [MꢀPFꢀ6 ]+ calcd for C70H70F6N2O7P: 1195.4824,
found: 1195.4822; [Mꢀ2PFꢀ6 ]2+ calcd for C70H70N2O7:
1
525.2592, found: 525.2593. H NMR (600 MHz, CD3CN,

L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
10785
TMS): d¼acridinium: 8.70 (d, J¼9.3 Hz, 2H, H-5), 8.48 (t,
J¼9.3 Hz, 2H, H-6), 8.30 (d, J¼9.3 Hz, 2H, H-4), 8.27 (d,
J¼7.8 Hz, 2H, H-8), 7.96 (t, J¼7.8 Hz, 2H, H-7), 7.87 (d, J¼
7.6 Hz, 2H, H-1), 7.50 (m, 2H, H-3), 6.54 (t, J¼7.6 Hz,
2H, H-2), 4.89 (s, 6H, N+–CH3); calixarene: 7.58 (s, 4H,
H-10, 12, 22, 24), 7.51 (d, J¼7.4 Hz, 4H, H-4, 6, 16, 18),
7.12 (t, J¼7.4 Hz, 2H, H-5, 17), 4.08 (d, 2J¼15.7 Hz,
4H, H-2, 8, 14, 20), 4.04 (d, 2J¼15.7 Hz, 4H, H-2, 8,
14, 20), 3.78 (m, 4H, –OCH2CH2CH3), 1.51 (m, 4H,
–OCH2CH2CH3), 0.48 (t, 6H, –OCH2CH2CH3); crown:
4.36 (m, 4H), 3.96 (m, 4H), 3.85 (m, 4H), 3.82 (m, 4H).
13C NMR (100 MHz, CD3CN, TMS): d¼161.0 (C, 2C),
158.8 (C, 2C), 156.6 (C, 2C), 142.2 (C, 2C), 141.5 (C,
2C), 139.0 (CH, 2C), 137.7 (CH, 2C), 135.9 (C, 4C),
135.5 (C, 4C), 134.6 (CH, 4C), 131.8 (CH, 4C), 131.0
(CH, 2C), 130.9 (CH, 2C), 128.2 (C, 2C), 128.0 (CH,
2C), 127.0 (CH, 2C), 126.4 (C, 2C), 125.3 (C, 2C), 123.4
(CH, 2C), 118.8 (CH, 2C), 118.4 (CH, 2C), 75.7
(–OCH2CH2CH3), 71.3 (CH2, 2C), 70.9 (CH2, 2C), 70.7
(CH2, 2C), 70.1 (CH2, 2C), 39.1 (N+–CH3), 36.8 (C-2, 8,
14, 20), 23.4 (–OCH2CH2CH3), 8.6 (–OCH2CH2CH3).
H-10, 12, 22, 24), 6.95 (t, 2H, H-5, 17), 3.72 (m, 4H, H-2,
8, 14, 20), 3.62 (m, 4H, H-2, 8, 14, 20); crown: 4.10 (m,
4H, 2ꢂCH2), 3.99 (m, 4H, 2ꢂCH2), 3.88 (m, 4H, 2ꢂCH2),
3.82 (m, 12H, 6ꢂCH2); ether: 3.77 (m, 4H, –OCH2CH2CH3),
1.61 (m, 4H, –OCH2CH2CH3), 0.60 (t, 6H, –OCH2CH2CH3).
13C NMR (75 MHz, CD3CN, TMS): d¼162.7 (C), 160.1
(C), 157.9 (C), 142.6 (C), 141.6 (C), 139.8 (CH), 137.2
(CH), 136.3 (C), 135 (CH), 133.9 (C), 132.8 (CH), 132.5
(CH), 132.2 (CH), 128.7 (CH), 127.1 (CH), 126.9 (C),
126.8 (C), 125.7 (C), 123.4 (CH), 119.3 (CH), 117.3 (CH),
77.1 (–OCH2CH2CH3), 74.0, 71.7, 71.6, 71.5, 71.3 (CH2-
crown), 39.7 (N+–CH3), 36.7 (CH2-calixarene), 24.4
(–OCH2CH2CH3), 9.8 (–OCH2CH2CH3).
4.3.4. 9-(4-Methoxyphenyl)-10-methyl-acridinium hexa-
fluorophosphate (6). Compound 6 was described in the lit-
erature.18 However, experimental details and analytical data
were not given. Compound 6 is, therefore, included. Butyl-
lithium (1.6 M in hexane) (2 mL, 3.2 mmol) in THF solution
(8 mL) was added dropwise to 4-bromoanisole (0.56 g,
3 mmol) dissolved in dry THF (50 mL) at ꢀ78 ꢁC. After
stirring for 0.5 h, N-methylacridone (0.630 g, 3 mmol) was
added. After warming the solution to room temperature, stir-
ring was continued for 1 h. The reaction was quenched with
water (5 mL). The solvent was evaporated in vacuo and the
residue was dissolved in acetonitrile (75 mL). The solution
was then treated with NH4PF6 (1 g). After stirring for
0.5 h, the solvent was removed in vacuo. The resulting solid
was three times washed with water. The crude product
was purified by CC (methanol/acetonitrile/aqueous 10%
NH4PF6 solution, 10:10:1.5) to afford yellow crystals,
0.51 g, 38%, mp 237–239 ꢁC. Anal. Calcd for C21H18F6NOP
(445.35): C, 56.64; H, 4.07; N, 3.15. Found: C, 56.70; H,
4.10; N, 3.45. 1H NMR (400 MHz, CD3CN, TMS):
d¼8.57 (d, 2H, H-1, 8), 8.35 (dt, 2H, H-2, 7), 8.10 (dd,
2H, H-4, 5), 7.84 (t, 2H, H-3, 6), 7.46 (d, 2H, C6H4OCH3),
7.27 (d, 2H, C6H4OCH3), 4.79 (s, 3H, –OCH3), 3.95 (s,
3H, N+–CH3). 13C NMR (100 MHz, CD3CN, TMS):
d¼161.7 (C), 161.0 (C), 141.3 (C), 138.2 (CH), 131.6
(CH), 130.1 (CH), 127.3 (CH), 126.0 (C), 124.7 (C), 118.1
(CH), 114.0 (CH), 55.1 (–OCH3), 38.3 (N+–CH3).
4.3.2. 11,23-Di-(N-methylacridinium-9-yl)-25,27-dihydr-
oxy-26,28-bis(propyloxy)calix[4]arene-crown-6, 1,3-
alternate bishexafluorophosphate (5b). Compound 5b was
purified by CC (acetonitrile, aqueous solution of NH4PF6
(2.5%) 20:1); orange crystals, 0.245 g (10%), mp 216–
218 ꢁC. Anal. C72H74F12N2O8P2 (1385.33); HRMS (ESI):
[MꢀPFꢀ6 ]+ calcd for C72H74F6N2O8P: 1239.5087, found:
1239.5012; [Mꢀ2PFꢀ6 ]2+ calcd for C72H74N2O8: 547.2722,
found: 547.2711. 1H NMR (600 MHz, CD3CN, TMS):
d¼acridinium: 8.64 (d, J¼9.3 Hz, 2H, H-5), 8.45 (dd, J¼
9.3, 9.0 Hz, 2H, H-6), 8.25 (d, J¼8.8 Hz, 2H, H-8), 8.12 (d,
J¼9.3 Hz, 2H, H-4), 7.93 (d, J¼8.0 Hz, 2H, H-1), 7.90 (t,
J¼8.8, 9.0 Hz, 2H, H-7), 7.35 (t, J¼9.3, 8.3 Hz, 2H, H-3),
6.60 (t, J¼8.0, 8.3 Hz, 2H, H-2), 4.78 (s, 6H, N+–CH3);
calixarene: 7.44 (s, 4H, H-10, 12, 22, 24), 7.39 (d, 4H,
H-4, 6, 16, 18), 7.02 (t, 2H, H-5, 17), 4.15 (m, 4H, H-2, 8,
14, 20), 3.95 (m, 4H, H-2, 8, 14, 20); crown: 3.88–3.83 (m,
16H, 8ꢂCH2), 3.80 (m, 4H, 4ꢂCH2), 3.73 (m, 4H,
–OCH2CH2CH3), 1.51 (m, 4H, –OCH2CH2CH3), 0.50 (t,
6H, –OCH2CH2CH3). 13C NMR (100 MHz, CD3CN,
TMS): d¼158.9 (C), 156.9 (C), 141.4 (C), 140.6 (C), 138.4
(CH), 136.2 (CH), 134.9 (C), 133.9 (CH), 131.2 (CH),
131.1 (CH), 130.9 (CH), 127.4 (CH), 126.0 (CH), 125.6
(C), 124.6 (C), 122.1 (CH), 118.1 (CH), 117.4 (CH), 75.5
(–OCH2CH2CH3), 72.1, 70.6, 70.4, 70.1, 69.9 (CH2-crown),
38.4 (N+–CH3), 35.9 (C-2, 8, 14, 20), 23.0 (–OCH2CH2CH3),
8.4 (–OCH2CH2CH3).
4.4. Calix[4]arenes 7–10: general procedure
The alcohol (1 mL) and K2CO3 (0.1 g) were added to the
acridinium compounds 3–6 (0.1 mmol) in dry acetonitrile
(10 mL). The suspension was stirred until decolorization
of the solution (2–12 h). After filtration the solvent was
removed in vacuo. The remaining residue was treated with
chloroform (10 mL) and then filtered. The filtrate was evap-
orated in vacuo to yield a solid that was used without further
purification.
4.3.3. 11,23-Di-(N-methylacridinium-9-yl)-25,27-dihydr-
oxy-26,28-bis(propyloxy)calix[4]arene-crown-7, 1,3-
alternate bishexafluorophosphate (5c). Compound 5c was
purified by CC (acetonitrile, aqueous solution of NH4PF6
(10%) 20:1); 0.5 g (14%)) yellow crystals, mp 203–205 ꢁC.
Anal. C74H78F12N2O8P2 (1429.39); HRMS (ESI): [MꢀPFꢀ6 ]+
calcd for C74H78F6N2O9P: 1283.5349, found: 1283.5367;
[Mꢀ2PFꢀ6 ]2+ calcd for C74H78N2O9: 569.2853, found:
569.2851. 1H NMR (600 MHz, CD3CN, TMS): d¼
acridinium: 8.63 (d, 2H, H-5), 8.46 (t, 2H, H-6), 8.24 (d,
2H, H-8), 8.06 (d, 2H, H-4), 8.03 (d, 2H, H-1), 7.93 (t, 2H,
H-7), 7.27 (t, 2H, H-3), 6.72 (t, 2H, H-2), 4.75 (s, 6H, N+–
CH3); calixarene: 7.45 (d, 4H, H-4, 6, 16, 18), 7.38 (s, 4H,
4.4.1. 11,23-Di-(10-methoxy-9,10-dihydro-9-methyl-acri-
din-9-yl)-25,27-dibenzyloxy-26,28-bis-(propyloxy)-
calix[4]arene (7). Colorless needles from acetone, 100 mg
(90%), mp 144 ꢁC, Anal. C78H74N2O6 (1135.46); HRMS
(ESI): [MꢀOCH3]+ calcd for C77H71N2O5: 1103.5363,
found: 1103.5367; [Mꢀ2CH3]2+ calcd for C76H68N2O4:
1
536.2590, found: 536.2589. H NMR (400 MHz, CDCl3,
TMS): d¼acridane: 7.34 (m, 4H, H-3, 6), 7.26 (m 4H,
H-1, 8), 7.08 (d, J¼8.0 Hz, 4H, H-2, 8), 6.98 (t, J¼8.0 Hz,
4H, H-4, 5), 3.57 (s, 6H, –OCH3), 2.91 (s, 6H, –NCH3);

10786
L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
calixarene: 7.32 (m, 4H, ortho –OCH2C6H5), 7.28 (m,
6H, –OCH2C6H5), 7.06 (s, 4H, H-10, 12, 20, 24), 6.15 (t,
2H, J¼7.5 Hz, H-5, 17), 5.91 (d, 4H, J¼7.5 Hz, H-4, 6,
16, 18), 5.21 (–OCH2C6H5), 4.15 (d, J¼13.3 Hz, 4H, H-2,
8, 14, 20), 3.53 (t, J¼7.0 Hz, 4H, –OCH2CH2CH3),
2.90 (d, J¼13.3 Hz, 4H, H-2, 8, 14, 20), 1.76 (m, 4H,
–OCH2CH2CH3), 0.99 (t, J¼7.5 Hz, 6H, –OCH2CH2CH3).
13C NMR (100 MHz, CDCl3, TMS): d¼155.2 (C), 154.5
(C), 141.6 (C), 141.4 (C), 138.2 (C), 136.5 (C), 133.1 (C),
130.4 (CH), 128.4 (CH), 128.1 (CH), 127.7 (CH), 127.6
(CH), 127.3 (CH), 124.8 (C), 122.0 (CH), 119 (CH), 112.0
(CH), 78.9 (–OCH2CH2CH3), 75.3 (–OCH2C6H5), 51.0
(–OCH3), 33.6 (–NCH3), 31.4 (C-2, 8, 14, 20), 23.4
–OCH2CH2CH3), 10.9 (–OCH2CH2CH3).
(93%), mp 155–160 ꢁC. Anal. C76H84N2O10 (1185.52);
HRMS (ESI): [M+K+]+ calcd for C76H84KN2O10:
1223.5763, found: 1223.5703; [MꢀOC2H5]+ calcd for
C74H79N2O9: 1139.5785, found: 1139.5737. 1H NMR
(400 MHz, CD3CN, TMS): d¼acridane: 7.43 (dd, J¼
9.3 Hz, 4H), 7.31 (m, 4H), 7.11 (m, 4H), 7.01 (t, J¼
9.3 Hz, 4H), 3.49 (s, 6H, –NCH3), 3.08 (q, J¼7.1 Hz, 4H,
–OCH2CH3), 1.18 (t, J¼7.1 Hz, 6H, –OCH2CH3); calix-
arene: 7.14 (d, J¼8.0 Hz, 4H, H-4, 6, 16, 18), 7.09 (s, 4H,
H-10, 12, 20, 24), 6.82 (t, J¼8.0 Hz, 2H, H-5, 17), 3.64
(m, 8H, –CH2), 3.25 (m, 4H, –OCH2CH2CH3), 1.17 (m,
4H, –OCH2CH2CH3), 0.61 (t, 6H, –OCH2CH2CH3); crown:
3.71 (m, 6H), 3.65 (m, 12H), 3.57 (m, 6H). 13C NMR
(75 MHz, CD3CN, TMS): d¼acridane: 141.0 (C-4a, 5a),
129.1 (C-1, 8), 128.3 (C-3, 6), 125.2 (C-1a, 8a), 120.1
(C-2, 7), 112.5 (C-4, 5), 58.4 (–OCH2CH3), 33.2 (–NCH3),
15.0 (–OCH2CH3); calixarene: 143.9 (C-11, 23), 136.1
(C-1, 9, 13, 21), 132.5 (C-3, 7, 15, 19), 130.4 (C-4, 6,
16, 18), 128.4 (C-10, 12, 20, 24), 120.4 (C-5, 17),
73.4 (–OCH2CH2CH3), 37.4 (C-2, 8, 14, 20), 22.2
(–OCH2CH2CH3), 9.3 (–OCH2CH2CH3); crown: 73.0 (2C,
CH2), 70.3 (2C, CH2), 70.2 (2C, CH2), 70.0 (4C, CH2).
4.4.2. 11,23-Di-(10-methoxy-9,10-dihydro-9-methyl-acri-
din-9-yl)-25,27-dihydroxy-26,28-bis-(propyloxy)calix[4]-
arene-crown-5, 1,3-alternate (8a). Colorless crystals,
100 mg (90%), mp 188–190 ꢁC, Anal. C72H76N2O9
(1113.41); HRMS (ESI): [M+K+] calcd for C72H76KN2O9:
1151.5188, found: 1151.5187; [MꢀOCH3]+ calcd for
C71H73N2O8: 1081.5367, found: 1081.5372; [M+K+ꢀOCH3]2+
calcd for C71H73KN2O9: 560.2502, found: 560.2504;
[Mꢀ2CH3]2+ calcd for C70H70N2O7: 525.2592, found:
525.2593. 1H NMR (400 MHz, (CD3)2CO, TMS): d¼
7.49–6.49 (m, 26H), 3.94–3.36 (m, 40H), 1.28 (m, 4H),
0.68 (t, 6H). 13C NMR (100 MHz, CDCl3, TMS): d¼157.9
(C), 153.5 (C), 144.2 (C), 141.2 (C), 135.9 (C), 132.3 (C),
130.6 (CH), 129.6 (CH), 128.9 (CH), 128.3 (CH), 124.3
(C), 121.5 (CH), 120.4 (CH), 112.1 (CH), 78.4 (C), 73.8
(–OCH2CH2CH3), 73.7, 70.8, 70.7, 70.0 (CH2-crown),
51.3 (–OCH3), 37.7 (CH2-cailxarene), 33.5 (–NCH3), 22.8
(–OCH2CH2CH3), 9.7 (–OCH2CH2CH3).
4.4.5. 11,23-Di-(9,10-dihydro-9-methyl-10-methoxy-acri-
din-9-yl)-25,27-dihydroxy-26,28-bis-(propyloxy)calix[4]-
arene-crown-7, 1,3-alternate (10a). Colorless crystals,
102 mg (85%), mp 140–142 ꢁC. Anal. C76H84N2O11
(1201.51); HRMS (ESI): [MꢀOMe]+ calcd for C75H81N2O10:
1169.5891, found: 1169.5861; [Mꢀ2-OMe]2+ calcd for
C74H78N2O9: 569.2853, found: 569.2849. 1H NMR
(400 MHz, (CD3)2CO, TMS): d¼acridane: 7.44 (dd, J¼
7.8 Hz, 4H, H-1, 8), 7.35 (dt, J¼7.0 Hz, 4H, H-3, 6), 7.19
(d, J¼7.0 Hz, 4H, H-4, 5), 7.05 (t, J¼7.8 Hz, 4H, H-2, 7),
3.56 (s, 6H, –NCH3), 3.01 (s, 6H, O–CH3); calixarene:
7.13 (d, J¼7.3 Hz, 4H, H-4, 6, 16, 18), 7.08 (s, 4H, H-10,
12, 22, 24), 6.85 (t, J¼7.3 Hz, 4H, H-5, 17), 3.75 (d,
4.4.3. 11,23-Di-(10-methoxy-9,10-dihydro-9-methyl-acri-
din-9-yl)-25,27-dihydroxy-26,28-bis-(propyloxy)calix[4]-
arene-crown-6, 1,3-alternate (9a). Colorless crystals,
97 mg (84%), mp 149–151 ꢁC. Anal. C74H80N2O10
(1157.46); HRMS (ESI): [M+Na+]+ calcd for
C74H80N2NaO10: 1179.5711, found: 1179.5636; [MꢀOCH3]+
2
2J¼15.8 Hz, 4H, H-2, 8, 14, 20), 3.71 (d, J¼15.8 Hz, 4H,
H-2, 8, 14, 20), 3.22 (m, 4H, –OCH2CH2CH3), 1.06 (m,
4H, –OCH2CH2CH3), 0.60 (t, 6H, –OCH2CH2CH3); crown:
3.68–3.59 (m, 20H), 3.32 (m, 4H). 13C NMR (100 MHz,
(CD)3CO, TMS): d¼acridane: 142.1 (C-4a, 5a), 130.0
(C-1, 8), 128.6 (C-3, 6), 125.4 (C-1a, 8a), 121.1 (C-2, 7),
113.4 (C-4, 5), 51.3 (–OCH3), 33.9 (–NCH3); calixarene:
158.4 (C-25, C-27), 154.9 (C-26, C-27), 145.0 (C-11, 23),
138.7 (C-1, 9, 13, 21), 135.8 (C-3, 7, 15, 19), 131.0
(C-4, 6, 16, 18), 129.2 (C-10, 12, 20, 24), 122.8 (C-5,
17), 73.7 (–OCH2CH2CH3), 38.5 (C-2, 8, 14, 20), 23.4
(–OCH2CH2CH3), 10.4 (–OCH2CH2CH3); crown: 71.4
(2C, CH2), 71.3 (2C, CH2), 71.2 (2C, CH2), 71.1 (2C,
CH2), 70.8 (2C, CH2), 70.1 (2C, CH2).
1
calcd for C73H77N2O9: 1125.5629, found: 1125.5562. H
NMR (400 MHz, (CD3)2CO, TMS): d¼acridane: 7.52 (d,
4H, J¼7.8 Hz, H-1, 8), 7.41 (t, 4H, J¼7.8 Hz, H-3, 6),
7.24 (d, 4H, J¼7.8 Hz, H-4, 5), 7.12 (t, 4H, J¼7.8 Hz,
H-2, 7), 3.62 (s, 6H, –N–CH3), 3.09 (s, 6H, –OCH3); calix-
arene: 7.29 (d, 4H, J¼7.5 Hz, H-4, 6, 16, 18), 7.19 (s, 4H,
H-10, 12, 20, 24), 6.94 (t, 2H, J¼7.5 Hz, H-5, 17), 3.86
(m, 4H, H-2, 8, 14, 20), 3.70 (m, 4H, H-2, 8, 14, 20); crown:
3.79 (br s, 20H); ether: 3.38 (m, 4H, –OCH2CH2CH3),
1.25 (m, 4H, –OCH2CH2CH3), 0.72 (t, 6H, 3J¼7.5 Hz,
–OCH2CH2CH3). 13C NMR (100 MHz, (CD3)2CO, TMS):
d¼acridane: 141.2 (C-4a, 5a), 129.1 (C-1, 8), 128.1 (C-3,
6), 124.3 (C-1a, 8a), 120.1 (C-2, 7), 112.4 (C-4, 5), 50.3
(–OCH3), 32.9 (–NCH3); calixarene: 135.3 (C-1, 9, 13,
21), 132.5 (C-3, 7, 15, 19), 130.0 (C-4, 6, 16, 18), 128.2
(C-10, 12, 20, 24), 121.4 (C-5, 17), 73.0 (–OCH2CH2CH3),
37.4 (C-2, 8, 14, 20), 22.4 (–OCH2CH2CH3), 9.3
(–OCH2CH2CH3); crown: 70.5 (4C, CH2), 69.8 (2C, CH2),
69.7 (2C, CH2), 69.1 (2C, CH2).
4.4.6. 11,23-Di-(10-ethoxy-9,10-dihydro-9-methyl-acri-
din-9-yl)-25,27-dihydroxy-26,28-bis-(propyloxy)calix[4]-
arene-crown-7, 1,3-alternate (10b). Beige crystals, 117 mg
(95%), mp 136–139 ꢁC. Anal. C78H88N2O11 (1229.57);
HRMS (ESI): [M+K+]+ calcd for C78H88KN2O11:
1267.6025, found: 1267.5995; [MꢀOEt]+ calcd for
C76H83N2O10: 1183.6048, found: 1183.6017; [Mꢀ2-OEt]2+
calcd for C74H78N2O9: 569.2853, found: 569.2851. 1H
NMR (400 MHz, CD3CN, TMS): d¼acridane: 7.42 (d,
4H, H-1, 8), 7.31 (t, 4H, H-3, 6), 7.12 (d, 4H, H-4, 5), 7.01
(t, 4H, H-2, 7), 3.48 (s, 6H, N–CH3), 3.08 (q, 4H,
O–CH2CH3), 1.25 (t, 6H, O–CH2CH3); calixarene: 7.17
4.4.4. 11,23-Di-(10-ethoxy-9,10-dihydro-9-methyl-acri-
din-9-yl)-25,27-dihydroxy-26,28-bis-(propyloxy)calix[4]-
arene-crown-6, 1,3-alternate (9b). Beige crystals, 110 mg

L. Grubert, W. Abraham / Tetrahedron 63 (2007) 10778–10787
10787
€
Comprehensive Supramolecular Chemistry; Vogtle, F., Ed.;
Pergamon: Oxford, 1996; Vol. 2, pp 103–142; (d) Ikeda, A.;
Shinkai, S. Chem. Rev. 1997, 97, 1713–1734.
(d, 4H, H-4, 6, 16, 18), 7.08 (s, 4H, H-10, 12, 22, 24), 6.88
(t, 2H, H-5, 17), 3.70–3.55 (m, 32H, 8ꢂCH2 and 12ꢂCH2-
crown), 3.24 (m, 4H, –OCH2CH2CH3), 1.15 (m, 4H,
–OCH2CH2CH3), 0.60 (t, 6H, –OCH2CH2CH3). 13C NMR
(100 MHz, (CD)3CO, TMS): d¼acridane: 141.9 (C-4a,
5a), 130.1 (C-1, 8), 128.7 (C-3, 6), 126.1 (C-1a, 8a), 121.0
(C-2, 7), 113.3 (C-4, 5), 59.1 (–OCH2CH3), 33.9 (–NCH3),
16.0 (–OCH2CH3); calixarene: 158.5 (C-25, C-27), 154.9
(C-26, C-27), 145.4 (C-11, 23), 135.9 (C-1, 9, 13, 21),
133.8 (C-3, 7, 15, 19), 131.1 (C-4, 6, 16, 18), 129.1 (C-10,
12, 20, 24), 122.8 (C-5, 17), 73.9 (–OCH2CH2CH3),
38.6 (C-2, 8, 14, 20), 23.5 (–OCH2CH2CH3), 10.5
(–OCH2CH2CH3); crown: 71.5 (2C, CH2), 71.4 (2C, CH2),
71.3 (2C, CH2), 71.2 (2C, CH2), 70.8 (2C, CH2), 70.1 (2C,
CH2).
€
2. Wang, L.; Vysotsky, M. O.; Bogdan, A.; Bolte, M.; Bohmer, V.
Science 2004, 304, 1312–1314.
3. Ikeda, A.; Shinkai, S. J. Am. Chem. Soc. 1994, 116, 3102–3110.
4. Steed, J. W.; Atwood, J. L. Supramolecular Chemistry; Wiley-
VCH: Chichester, UK, 2000.
5. Abraham, W. J. Incl. Phenom. Macrocycl. Chem. 2002, 43,
159–174.
6. Gutsche, C. D.; Alam, I. Tetrahedron 1988, 4689–4694.
7. Orda-Zgadzaj, M.; Wendel, V.; Fehlinger, M.; Ziemer, B.;
Abraham, W. Eur. J. Org. Chem. 2001, 1549–1561.
8. Azov, V. A.; Diederich, F.; Lill, Y.; Hecht, B. Helv. Chim. Acta
2003, 86, 2149–2155.
9. Azov, V. A.; Schlegel, A.; Diederich, F. Angew. Chem., Int. Ed.
2005, 44, 4635–4638.
10. Gottschalk, T.; Jaun, B.; Diederich, F. Angew. Chem., Int. Ed.
2007, 46, 260–264.
4.4.7. 9,10 Dihydro-9-methoxy-9-(4-methoxyphenyl)-10-
methyl-acridine (11). Colorless crystals, 70 mg (94%),
mp 137–140 ꢁC. Anal. C22H21NO2 (331.42); HRMS (ESI):
[M+Na+]+ calcd for C22H21NNaO2: 354.1467, found:
354.1462; [MꢀOCH3]+ calcd for C21H18NO: 300.1388,
found: 300.1381. 1H NMR (400 MHz, CDCl3, TMS)
d¼7.28 (dt, 2H, H-1, 8), 7.25 (dd, 2H, H-3, 6), 7.14 (d,
2H, C6H4OCH3), 7.12 (d, 2H, H-4, 5), 6.90 (dt, 2H, H-2,
7), 6.74 (d, 2H C6H4OCH3), 3.73 (s, 3H, OCH3), 3.50 (s,
3H, OCH3), 2.97 (s, 3H, –NCH3). 13C NMR (100 MHz,
CDCl3, TMS) d¼158.1 (p-C6H4OCH3), 142.2 (ipso-
C6H4OCH3), 141.2 (C-4a, 5a), 129.5 (o-C6H4OCH3),
128.5 (C-1, 8), 127.6 (C-3, 6), 124.8 (C-1a, 8a), 120.4
(m-C6H4OCH3), 113.2 (C-2, 7), 112.4 (C-1, 8), 78.5 (C-9),
55.4 (–C6H4OCH3), 51.4 (–OCH3), 36.7 (–NCH3).
€
11. Schafer, C.; Eckel, R.; Ros, R.; Mattay, J.; Anselmetti, D.
J. Am. Chem. Soc. 2007, 129, 1488–1489.
12. Grigor’eva, M.; Ivanov, V. L.; Kuzmin, M. G. Zh. Org. Khim.
1981, 17, 423–428.
€
13. Abraham, W.; Buck, K.; Orda-Zgadzaj, M.; Schmidt-Schaffer,
S.; Grummt, U.-W. Chem. Commun. 2007, 3094–3096.
14. Unfortunately, only very thin needles (0.5ꢂ0.05ꢂ0.05 mm)
could be obtained. The quality of the refinement therefore
did not allow the exact determination of bond angles and
bond lengths. However, the chemical constitution of the com-
pound could unambiguously be determined.
15. Fukuzumi, S.; Kotani, H.; Ohkubo, K.; Ogo, S.; Tkachenko,
N. V.; Lemmetyinen, H. J. Am. Chem. Soc. 2004, 126, 1600–
1601.
16. Timmerman, P.; Weidmann, J.-L. K.; Jolliffe, A.; Prins, L. J.;
Reinhoudt, D. N.; Shinkai, S.; Frish, L.; Cohen, Y. J. Chem.
Soc., Perkin Trans. 2 2000, 2077–2090.
17. Casnati, A.; Pochini, A.; Ungaro, R.; Ugozzoli, F.; Arnaud, F.;
Fanni, S.; Schwing, M.-J.; Egberink, R. J. M.; de Jong, F.;
Reinhoudt, D. N. J. Am. Chem. Soc. 1995, 117, 2767–2777.
18. (a) Lee, I.; Chow, K.; Kreevoy, M. J. Am. Chem. Soc. 2002,
124, 7755–7761; (b) Goubitz, K.; Reiss, C. A.; Heijdenrijk,
Acknowledgements
Financial support provided by Deutsche Forschungsgemein-
schaft is gratefully acknowledged.
References and notes
1. (a) Gutsche, C. D. Calixarenes; Royal Society of Chemistry:
Cambridge, England, 1989; (b) Calixarenes: A Versatile
D. Acta Crystallogr., Sect. C 1990, 46, 1081–1084;
(c) Kreevoy, M. M.; Lee, I. Z. Naturforsch. 1989, 44a,
418–426.
€
Class of Macrocyclic Compounds; Vicens, J., Bohmer, V.,
Eds.; Kluwer: Dordrecht, 1991; (c) Pochini, A.; Ungaro, R.