Synthesis and electrode properties of 19-membered azo- and azoxycrown ethers. Structure of dibenzo-19-azocrown-7

Article abstract of DOI:10.1016/j.tet.2005.09.133

19-Membered azo- and azoxycrown ethers have been synthesized by reductive macrocyclization of respective bis-(nitrophenoxy)oxaalkanes. The behavior of these compounds as ionophores in ion-selective membrane electrodes has been studied. The structure of th

Full text of DOI:10.1016/j.tet.2005.09.133

Tetrahedron 62 (2006) 149–154
Synthesis and electrode properties of 19-membered azo- and
azoxycrown ethers. Structure of dibenzo-19-azocrown-7
a
b
Anna M. Skwierawska,a, Jan F. Biernat and Victor Ch. Kravtsov
*
a
´
´
Department of Chemical Technology, Gdansk University of Technology, 80-952 Gdansk, Poland
bInstitute of Applied Physics, Academy of Science of Moldova, Kishinev, Republic of Moldova
Received 22 April 2005; revised 14 September 2005; accepted 29 September 2005
Available online 7 November 2005
Abstract—19-Membered azo- and azoxycrown ethers have been synthesized by reductive macrocyclization of respective bis-
(nitrophenoxy)oxaalkanes. The behavior of these compounds as ionophores in ion-selective membrane electrodes has been studied. The
structure of the 19-membered dibenzoazocrown ether has been determined.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
presentation of their properties in ion-selective membrane
electrodes.
The chromogenic system of azo dyes consists of a chain of
conjugated double bonds and azo group(s). An azo group
inserted into conjugated system causes a strong increase of
color intensity. Additionally azo compounds can exist in
two isomeric forms (Z and E) that make the system even
more interesting for physicochemical study especially if the
azo group forms part of a macrocyclic system.
2. Results and discussion
2.1. Synthesis
The presented synthesis of 19-membered azo- and azoxy-
crown ethers is a two-step reaction. 1,11-Bis(2-nitro-
phenoxy)-3,6,9-trioxaundecanes were obtained by reaction
of 2-nitrophenol or its derivatives with 1,11-dichloro-3,6,
9-trioxaundecane in dry dimethylformamide in the presence
of anhydrous potassium carbonate (compounds 1–3)
(Scheme 1).
So far, three procedures for azocrown ether synthesis
have been described. The first consists of alkylation of
2,20-hydroxyazobenzene.1 The second method utilizes
reduction of bis(2-nitrophenoxy)-oxaalkanes with sodium
or potassium stannite whereupon the azo bond is formed.2
This procedure allowed two main macrocyclic products to
be obtained with azo or azoxy groupings. According to
this reductive macrocyclization method, 10-, 13-, and
16-membered azo and azoxycrown ethers have been
synthesized.3–5 Finally, the third procedure consists of
nucleophilic substitution of difluoroazobenzene with
alcoholates, thiolates or diamines.6
In the next step, nitroderivatives 1–3 were reduced in water–
acetone with sodium or potassium stannite to produce
19-membered azo- and azoxycrown ethers. A remarkable
sodium template effect for azo compound formation was
noticed only in the case of reduction of compound 1. If
sodium hydroxide was used instead of potassium hydroxide
the yield of compound 4 increased almost twice. The yield
of macrocyclic products was lower than in the case of
13- and 16-membered compounds and more polymeric
products were formed. In addition, the separation of Z and E
isomers of 19-membered substituted azocrown ethers was
troublesome because of rapid isomerization; in some cases,
their geometry was ascribed considering significant
Preliminary studies have shown that 19-membered azo- and
azoxycrown ethers could be prepared by reductive
macrocyclization in a similar way to the 13- and
16-membered analogs.
The aim of this work was preparation of 19-membered
azocrown ethers, identification of their stereoisomers, and
1
Keywords: Azocrown; Azoxycrown ethers; Ion-selective membrane;
Thallium(I) selectivity.
differences in H NMR spectra. Surprisingly, compound 4
in the solid state and in solutions in chloroform, methanol
and acetone solution existed only in E form.
*
Corresponding author. Tel.: C48 58 3472288; fax: C48 58 3471949;
e-mail: skwieraw@chem.pg.gda.pl
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.09.133

150
A. M. Skwierawska et al. / Tetrahedron 62 (2006) 149–154
Compared to this cation, only the electrode response to
O
Ag(I) was higher for ionophores 4, 5, and 8. Furthermore,
electrodes based on compounds 4 and 5 showed high
thallium selectivity in the presence of many transition and
heavy metal cations like Pb(II), Hg(II), Zn(II) and Ni(II),
and alkali earth cations.
OH
O
O
Cl
O
NO2
1.
+
O
O
O
O2N
NO2
Cl
O
R
Thallium salts are extremely toxic. Thallium is obtained as a
side product in sulfuric acid manufacture and during lead
decontamination. Thallium can be delivered into human
body from contaminated air, water or food. Thallium
replaces potassium cations, thus causing deactivation of
some enzymes. Therefore, thallium distribution has to be
under strict control; the ion-selective membrane electrodes
based on 19-membered azo- and azoxycrown ethers
appeared as potentially useful for that purpose.
2.
R
R
1. R =H
2. R = t-butyl
3. R = phenyl
O
O
O
O
R
O
N
X
N
2.3. X-Ray structure
R
X = none
X = O
X-ray study reveals that in the crystal structure of 4 the
asymmetric part of unit cell contains two crystallographi-
cally independent molecules labeled A and B, Figure 2.
Both molecules are chemically equivalent and adopt E
geometry with aromatic moieties in trans-positions around
the –N]N– bond, but differ essentially in the conformation
of their polyether chains.
4. R = H
5. R = H
6. R = t-butyl
7. R = t-butyl
8. R = phenyl
9. R = phenyl
Scheme 1. Synthesis of 19-membered azo and azoxycrown ethers;
(1) K2CO3, DMF, 120 8C; (2) NaOH or KOH, SnCl2, water/acetone.
2.2. Membrane electrodes
The most frequently studied property of azo- and
azoxycrown ethers is their behavior in ion-selective
membrane electrodes. 13-Membered azocrown ethers are
selective toward sodium cations7 while 16-membered
compounds are potassium selective8 in membrane electro-
des. We expected that 19-membered derivatives should be
selective to larger cations. In a preliminary experiments
the ion-selective membrane electrodes doped with
19-membered azo- and azoxycrown ethers were selective
for the thallium(I) cation (Fig. 1).
2
Tl
Ag
H
Ag
1
0
Ag
Pb
K
Tl
Ag
Tl
Ag
Pb
Pb
K
Cs
Rb
NH4
Na
H
Hg
Zn
Ba
Cu
Ni
Co
Sr
Rb
NH4
Cs
Na
Hg
Li
Ba
Cu
Zn
Mg
Sr
K
Tl
K
Tl
Cs
Rb
NH4
Hg
H
Na
Ba
Li
Cu
Zn
Sr
Ca
Ni
H
K
Cs
Rb
NH4
H
Na
Pb
Hg
Li
-1
-2
-3
-4
-5
-6
Cs
Rb
NH4
Na
Pb
Hg
Zn
Li
Ba
Ni
Sr
Cu
Co
Ni
Co
Ca
Zn
Ba
Cu
Sr
Li
Co
Figure 2. Top and side view of molecules A and B in the structure of 4 with
atom numbering scheme.
Ni
Ca
Mg
Co
Ca
Mg
Mg
Ca
Mg
The torsion angles around the C–C bonds in the polyethylene
chain of A are gauche, and anti around C–O bonds, except
C(11A)–C(12A)–O(13A)–C(14A)Z74.58, which is gauche,
Table 1, and the conformation of the polyoxyethylene chain
units may be described as: a, a, Kg, a, a, g, a, a, Kg, a, a, g, g,
a, starting at the O(1A)–C(19A) bond. The sequence of two
gauche torsion angles form corner fragment9 at C(12A) atom
4
5
8
9
Blank
pot
Tl/X
Figure 1. Diagram of log K values of ion-selective membrane electrode
doped with azo- or azoxycrown ethers 4, 5, 8, or 9 compared to blank
electrode.

A. M. Skwierawska et al. / Tetrahedron 62 (2006) 149–154
Table 1. Selected valence and torsion angles (8) for 4 and selected bond lengths for 4
151
Angle
Molecule A
Molecule B
Angle
Molecule A
Molecule B
O(1)–C(2)–C(3)–O(4)
C(2)–C(3)–O(4)–C(5)
C(3)–O(4)–C(5)–C(6)
O(4)–C(5)–C(6)–O(7)
C(5)–C(6)–O(7)–C(8)
C(11)–C(12)–O(13)–C(14)
C(12)–O(13)–C(14)–C(15)
O(13)–C(14)–C(15)–N(16)
C(14)–C(15)–N(16)–N(17)
C(15)–N(16)–N(17)–C(18)
K67.9(8)
176.2(7)
K175.6(7)
74.6(8)
K177.0(7)
74.5(10)
K167.6(7)
K0.5(11)
137.1(7)
K58.5(9)
K77.0(9)
173.2(8)
179.1(8)
K177.1(8)
156.6(7)
K165.1(6)
K7.9(10)
150.9(7)
C(6)–O(7)–C(8)–C(9)
K161.2(8)
K77.3(10)
170.4(7)
172.1(8)
59.1(9)
160.0(7)
K8.7(9)
K166.7(6)
153.9(6)
K85.8(11)
72.2(11)
172.9(7)
K164.2(7)
K74.0(8)
140.8(7)
K3.2(11)
K149.5(7)
161.1(6)
O(7)–C(8)–C(9)–O(10)
C(8)–C(9)–O(10)–C(11)
C(9)–O(10)–C(11)–C(12)
O(10)–C(11)–C(12)–O(13)
N(16)–N(17)–C(18)–C(19)
N(17)–C(18)–C(19)–O(1)
C(18)–C(19)–O(1)–C(2)
C(19)–O(1)–C(2)–C(3)
170.7(6)
171.6(7)
Bond
Molecule A
Molecule B
Bond
Molecule A
Molecule B
O(1)–C(19)
O(1)–C(2)
C(2)–C(3)
C(3)–O(4)
O(4)–C(5)
C(5)–C(6)
C(6)–O(7)
O(7)–C(8)
C(8)–C(9)
1.362(8)
1.437(9)
1.496(10)
1.397(9)
1.394(8)
1.471(10)
1.402(9)
1.403(9)
1.462(11)
1.332(10)
1.416(10)
1.442(11)
1.459(10)
1.366(10)
1.386(10)
1.400(11)
1.385(10)
1.416(9)
1.384(11)
1.385(12)
1.362(12)
1.236(7)
1.426(8)
1.393(9)
1.404(10)
1.373(9)
1.398(10)
1.333(11)
1.374(10)
118.6(6)
107.6(7)
108.4(7)
1.357(9)
1.421(8)
1.483(10)
1.424(8)
1.389(10)
1.521(10)
1.350(10)
1.400(8)
1.449(11)
1.352(11)
1.457(10)
1.474(11)
1.441(8)
1.334(9)
1.375(10)
1.417(10)
1.359(10)
1.431(9)
1.396(10)
1.377(11)
1.376(11)
1.257(7)
1.425(9)
1.370(10)
1.401(9)
1.381(10)
1.370(11)
1.371(11)
1.387(10)
117.5(6)
108.5(6)
115.0(6)
C(5)–O(4)–C(3)
O(4)–C(5)–C(6)
O(7)–C(6)–C(5)
C(6)–O(7)–C(8)
O(7)–C(8)–C(9)
113.7(6)
108.3(7)
111.9(8)
113.5(7)
112.3(8)
112.7(9)
112.6(8)
109.7(8)
111.7(7)
120.4(7)
124.0(9)
117.1(7)
118.8(9)
120.7(8)
123.3(8)
115.9(7)
119.7(9)
118.9(9)
121.9(9)
119.9(10)
113.3(6)
114.7(6)
119.1(7)
123.7(7)
117.0(7)
123.3(8)
116.8(7)
119.9(7)
119.1(8)
121.0(8)
121.2(8)
119.5(8)
113.6(6)
108.6(7)
108.4(8)
115.3(7)
115.0(8)
113.1(8)
116.0(8)
107.1(7)
108.6(7)
116.0(6)
124.3(7)
116.4(7)
119.3(8)
120.6(7)
123.1(7)
115.9(8)
120.3(8)
118.2(8)
122.7(8)
118.9(8)
113.8(6)
112.3(6)
119.8(7)
122.4(6)
117.6(7)
123.7(7)
116.6(7)
119.7(8)
119.6(8)
121.2(8)
119.5(9)
120.1(8)
O(10)–C(9)–C(8)
C(9)–O(10)–C(11)
O(10)–C(11)–C(12)
C(11)–C(12)–O(13)
C(14)–O(13)–C(12)
O(13)–C(14)–C(27)
O(13)–C(14)–C(15)
C(27)–C(14)–C(15)
C(24)–C(15)–C(14)
C(24)–C(15)–N(16)
C(14)–C(15)–N(16)
C(25)–C(24)–C(15)
C(24)–C(25)–C(26)
C(27)–C(26)–C(25)
C(26)–C(27)–C(14)
N(17)–N(16)–C(15)
N(16)–N(17)–C(18)
C(23)–C(18)–C(19)
C(23)–C(18)–N(17)
C(19)–C(18)–N(17)
O(1)–C(19)–C(20)
O(1)–C(19)–C(18)
C(20)–C(19)–C(18)
C(19)–C(20)–C(21)
C(22)–C(21)–C(20)
C(21)–C(22)–C(23)
C(22)–C(23)–C(18)
C(9)–O(10)
O(10)–C(11)
C(11)–C(12)
C(12)–O(13)
O(13)–C(14)
C(14)–C(27)
C(14)–C(15)
C(15)–C(24)
C(15)–N(16)
C(24)–C(25)
C(25)–C(26)
C(26)–C(27)
N(16)–N(17)
N(17)–C(18)
C(18)–C(23)
C(18)–C(19)
C(19)–C(20)
C(20)–C(21)
C(21)–C(22)
C(22)–C(23)
C(19)–O(1)–C(2)
O(1)–C(2)–C(3)
O(4)–C(3)–C(2)
of macrocycle A. In macrocycle B one of the torsion angles
around C–C bond (O(4B)–C(5B)–C(6B)–O(7B)Z179.18) is
anti creating sequence of three anti torsion angles in the
polyether chain, which is unusual for azo-macrocycles. The
conformation of the polyether chain starting from O(1B)–
C(19B) is: a, a, Kg, Kg, a, a, a, Kg, g, a, a, Kg, a, a. The
series of torsion angles points to the presence of two corner
fragments in macrocycle B, at atoms C(3B) and C(8B).
Torsion angles around N16–N17 and bond lengths equal
adopt very similar values of 71.1(2) and 77.9(2)8,
respectively. These angles essentially exceed the corre-
sponding dihedral angles found in the relative small
sized 10-membered10 and 13-membered,11 or bigger
21-membered12 trans-isomers of azobenzocrown ethers
bearing 2,20-linked azobenzene moiety, where they are
in the range of 0–408. Interestingly, in the closest by size
20-membered azoazoxycrown13 the dihedral angles
between benzene residues of azo- and azoxybenzene
moieties equal 73.5 and 76.48, and agree well with the
values reported here for the 19-membered azomacrocycle.
˚
170.7(6) and 171.6(7)8, and 1.236(7) and 1.257(7) A,
respectively, for molecules A and B and had of common
values, Table 1.
3. Experimental
The heteroatoms of the macrocycle A cavity are roughly
coplanar and deviate from their mean plane in the range
˚
K0.200(4) – 0.229(4) A. In the case of macrocycle B, the
cavity is non-planar and the heteroatoms deviate from the
All materials and solvents used for synthesis were of
analytical reagent grade. Silica gel 60 (Merck) was used for
column chromatography. Preparative TLC glass plates
covered with Silica gel 60 F254 (Merck) were used for
˚
mean plane in the range from K0.761(5) to 0.480(4) A.
1
The benzene residues are located at different sides of the
mean plane in both molecules. Despite conformational
differences between the polyether chains, the dihedral
angles between aromatic residues in molecules A and B
final separation of crown ethers. H NMR spectra, all in
CDCl3, were taken on Varian instruments at 200 MHz and/
or 500 MHz. In the case of Z or E isomers of azocrown
ethers, the spectra were recorded immediately after

152
A. M. Skwierawska et al. / Tetrahedron 62 (2006) 149–154
dissolution of crystals or oil. IR and mass spectra
were recorded on AMD-604 and Genesis II (Mattson)
apparatus, respectively. Additionally, purity and identity of
macrocyclic compounds was established by elemental
analysis taken on an EAGER 200 apparatus. The mp
were uncorrected. 4-t-Butyl-2-nitrophenol and 4-phenyl-2-
nitrophenol were obtained according to literature data.9
3,6,9-trioxaundecane (5.8 g, 25 mmol), anhydrous potas-
sium carbonate (6.9 g, 50 mmol) and dimethylformamide
(15 mL). Yield of pure oily product was 16.5 g (60%).
Calculated for C28H41N2O9: [MCH peak] m/zZ549.2812.
Found: 549.2810. Anal. Calcd C 61.31, H 7.30, N 5.11.
Found C 61.28, H 7.31, N 5.10; dH (CDCl3, 200 MHz): 1.31
(18H, s); 3.64–3.69 (4H, m); 3.73–3.78 (4H, m); 3.89 (4H, t,
JZ4.6 Hz); 4.24 (4H, t, JZ5.1 Hz); 7.04 (2H, d, JZ
8.8 Hz); 7.52 (2H, dd, J1Z4.8 Hz, J2Z8.8 Hz); 7.82 (2H, d,
JZ2.5 Hz). Mass Spec (MeOH, ESC) m/z expected:
548.27. Found: 549.28 (MCH); IR (film) 2778, 1606,
1542, 1353, 1278, 1133, 1043, 938, 851, 746, 668 (cmK1).
3.1. Membrane electrodes and potentiometric
measurements
The preparation of membranes for ion-selective electrodes
was described earlier in detail.9 The standard composition
of membranes was: ionophore 10 mg, potassium tetrakis-
(4-chlorophenyl)borate 0.5 mg, poly(vinyl chloride) 50 mg,
and 2-nitrophenyl octyl ether 0.1 mL.
3.3.3. 1,11-Bis(4-phenyl-2-nitrophenoxy)-3,6,9-tri-
oxaundecane (3). Obtained analogously to 1 using:
4-phenyl-2-nitrophenol9 (10.8 g, 50 mmol), 1,11-dichloro-
3,6,9-trioxaundecane (5.8 g, 25 mmol), anhydrous potas-
sium carbonate (6.9 g, 50 mmol) and dimethylformamide
(15 mL). Crude compound 3 was purified by column
chromatography using chloroform as an eluent. Yield after
crystallization from 2-propanol was 17.6 g (60%). Mp
80–82 8C, yellow crystals. Calculated for C32H33N2O9:
[MCH peak] m/zZ589.2186. Found: 549.2188. Anal.
Calcd C 65.31, H 5.61, N 4.76. Found C 65.29, H 5.62, N
4.75; dH (CDCl3, 200 MHz): 3.67–3.72 (4H, m); 3.76–3.81
(4H, m); 3.91–3.96 (4H, m); 4.28–4.33 (4H, m); 7.17 (2H, d,
JZ8.7 Hz); 7.36–7.56 (10H, m); 7.71 (2H, dd, J1Z2.4 Hz,
J2Z8.7 Hz); 8.05 (2H, d, JZ2.3 Hz). Mass Spec (MeOH,
ESC) m/z expected: 588.21. Found: 589.22 (MCH); IR
(film) 2783, 1607, 1524, 1356, 1279, 1132, 1044, 940, 850,
746, 664 (cmK1).
3.2. X-Ray crystal structure determination
A single crystal of azocrown 4 was obtained by crystal-
lization from hexane. The data were collected at room
temperature on KUMA diffractometer using graphite-
monochromated Mo Ka radiation and were corrected for
Lorentz and polarization effects. The structure was solved
using direct methods and refined by full-matrix least squares
on F2.14 All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were placed in geometrically
calculated positions and refined using temperature factors
1.2 times those of their bonded carbon atoms. Crystal
data for 4: C20H24N2O5, MrZ372.41, monoclinic, P21/n,
˚
˚
˚
aZ14.976(3) A, bZ14.024(3) A, cZ18.577(4) A, bZ
3
3
˚
97.71(3)8, VZ3866(1) A , ZZ8, DcZ1.280 g/cm , mZ
0.92 cmK1, F(000)Z1584, qmaxZ25.568(K18%h%17,
0%k%17, 0%l%21), reflections collected 7435, indepen-
dent reflections 7203 (RintZ0.0566), goodness-of-fit on F2
SZ1.068. Final residuals (for 488 parameters) R1Z0.0633,
wR2Z0.1805 for 2657 reflections with IO2s(I), and R1Z
0.1724, wR2Z0.2164 for all data. Residual electron
3.3.4. Bis(benzo)-19-azocrown-7 (4) and bis(benzo)-
19-azoxycrown-7 (5). In the presence of potassium
hydroxide. Water (12 mL) was added dropwise to a
vigorously stirred mixture of dinitroderivative 1 (1.3 g,
3 mmol), stannous chloride dihydrate (2.9 g, 13 mmol),
potassium hydroxide (5.6 g) and acetone (15 mL). The
mixture was additionally vigorously stirred at 50 8C for 5 h.
Then the cooled mixture was diluted with water (10 mL)
and extracted with chloroform (3!50 mL). The organic
layer was dried over anhydrous MgSO4 and the solvent was
evaporated under reduced pressure. The crude product was
preliminarily chromatographed on a short silica gel column
using methylene chloride at the beginning and then
methylene chloride–acetone mixture (10/1) as eluents to
remove polymers and diacetone alcohol. The eluate was
evaporated and the residue was extracted with hot heptane
to isolate a mixture of compounds 4 and 5 that finally were
separated by preparative thin-layer chromatography. The
azocrown ether was crystallized from heptane to obtain E
isomer (56 mg, 5%), mp 114–116 8C. The azoxycrown ether
was obtained as yellowish oil (112 mg, 10%).
K3
˚
density: 0.432 and K0.244 eA
.
3.3. Syntheses.
3.3.1. 1,11-Bis(2-nitrophenoxy)-3,6,9-trioxaundecane
(1). A mixture of 2-nitrophenol (6.9 g, 50 mmol), 1,11-
dichloro-3,6,9-trioxaundecane (5.8 g, 25 mmol), anhydrous
potassium carbonate (6.9 g, 50 mmol) and dimethylforma-
mide (15 mL) was heated at 120 8C for 8 h. The mixture was
poured into water and the product was extracted with
chloroform. After evaporation of solvent, the residue
was purified by gradient column chromatography using
petroleum ether/chloroform solvent system. Yield of the
pure oily product was 14.8 g (68%). Calculated for
C20H24N2O9: [MCH peak] m/zZ437.1560. Found:
437.1562. Anal. Calcd C 55.04, H 5.50, N 6.42. Found C
55.0, H 5.48, N 6.41; dH (CDCl3, 200 MHz): 3.58–3.63 (4H,
m); 3.67–3.71 (4H, m); 3.82–3.88 (4H, m); 4.18–4.23 (4H,
m); 6.92–7.09 (4H, m); 7.42–7.51 (2H, m); 7.74 (2H, dd,
J1Z1.7 Hz, J2Z8.1 Hz); Mass Spec (MeOH, ESC) m/z
expected: 436.15. Found: 437.16 (MCH); IR (film) 2870,
1604, 1520, 1349, 1280, 1130, 936, 849, 746 (cmK1).
In the presence of sodium hydroxide. The synthesis was
performed analogously using an equivalent amount of
sodium hydroxide. After the reaction was completed, the
mixture was cooled and the precipitated sodium chloride
was filtered off and washed with toluene (2!25 mL). The
combined organic layers were dried over MgSO4 and
the solvents were evaporated under reduced pressure.
After separation of the crown ethers as above, the azocrown
ether was crystallized from heptane to afford E isomer
3.3.2. 1,11-Bis(4-tert-butyl-2-nitrophenoxy)-3,6,9-
trioxaundecane (2). Obtained analogously to 1 using:
4-tert-butyl-2-nitrophenol9 (9.8 g, 50 mmol), 1,11-dichloro-

A. M. Skwierawska et al. / Tetrahedron 62 (2006) 149–154
153
(200 mg, 18%), mp 116 8C. The azoxycrown ether was
obtained as yellowish oil (104 mg, 9%).
3.67–3.69 (4H, m); 3.90–3.93 (4H, m); 4.26–4.29 (4H, m);
7.00 (1H, d, JZ8.8 Hz); 7.04 (1H, d, JZ8.8 Hz); 7.34 (1H,
dd, J1Z2.4 Hz, J2Z8.8 Hz); 7.43 (1H, dd, J1Z2.4 Hz, J2Z
8.3 Hz); 7.66 (1H, d, JZ2.4 Hz); 8.03 (1H, d, JZ2.4 Hz).
Mass Spec (MeOH, ESC) m/z expected: 500.29. Found:
501.30 (MCH); IR (film) 2965, 2872, 1731, 1605, 1504,
1457, 1359, 1265, 1134, 942, 896, 819, 753 (cmK1).
Azocrown 4. Calculated for C20H25N2O5: [MCH peak]
m/zZ373.1763. Found: 373.1764. Anal. Calcd C 64.50, H
6.50, N 7.52. Found C 64.56, H 6.44, N 7.44; Mass Spec
(MeOH, ESC) m/z expected: 372.17. Found: 373.18 (MC
H); isomer E: dH (CDCl3, 500 MHz): 3.45–3.47 (4H, m);
3.59–3.61 (4H, m); 4.40 (4H, t, JZ4.4 Hz); 4.37 (4H, t, JZ
4.4 Hz); 7.02 (2H, d, JZ7.8 Hz); 7.33 (2H, dd, J1Z1.5 Hz,
J2Z7.8 Hz); 7.39 (2H, dt, J1Z1.5 Hz, J2Z7.32 Hz). IR
(film), nmax (cmK1) 2924, 2872, 1589, 1482, 1452, 1285,
1242, 1124, 1046, 938, 753.
3.3.6. Bis(4-phenylbenzo)-19-azocrown-7 (6) and
bis(4-phenylbenzo)-19-azoxycrown-7 (7). Water (8 mL)
was dropwise added to a vigorously stirred mixture of
dinitroderivative 3 (1.2 g, 2 mmol), stannous chloride
dehydrate (1.95 g, 8 mmol), sodium hydroxide (2.4 g) and
acetone (8 mL). The mixture was stirred at 55 8C
additionally for 4 h. After work-up as above the azocrown
ether was obtained as red oil, 83 mg (8%), mp 128–129 8C.
The azoxycrown ether was obtained as yellowish oil
(162 mg, 15%).
Azoxycrown 5. Calculated for C20H25N2O6: [MCH peak]
m/zZ389.1713. Found: 389.1712. Anal. calcd C 61.84, H
6.23, N 7.21. Found C 61.90, H 6.23, N 7.18; dH (CDCl3,
500 MHz): 3.59–3.62 (4H, m); 3.64–3.69 (4H, m); 3.90–3.93
(4H, m); 4.27–4.31 (4H, m); 7.04 (3H, m); 7.11 (1H, d, JZ
8.3 Hz); 7.32 (1H, dt, J1Z1.5 Hz, J2Z7.8 Hz); 7.42 (1H, dt,
J1Z1.5 Hz, J2Z8.8 Hz); 7.63 (1H, dd, J1Z1.5 Hz, J2Z
8.3 Hz); 8.05 (1H, dd, J1Z1.5 Hz, J2Z8.3 Hz); Mass Spec
(MeOH, ESC) m/z expected: 388.16. Found:389.17(MCH);
IR (film) 2957, 2917, 2874, 1600, 1521, 1486, 1453, 1351,
1261, 1107, 1056, 940, 850, 801,745, 672 (cmK1).
Azocrown 8. Calculated for C32H33N2O5: [MCH peak]
m/zZ525.2395. Found: 529.2398. Anal. calcd C 73.28, H
6.11, N 5.34. Found C 73.01, H 8.22, N 5.70.
Azocrown 8, isomer Z: dH (CDCl3, 500 MHz): 3.73–3.75 (6H,
m); 3.79–3.81 (2H, m)3.85(2H, t, JZ4.5 Hz);3.95(2H, t, JZ
4.5 Hz); 4.19 (2H, t, JZ4.5 Hz); 4.30 (2H, t, JZ4.5 Hz); 6.95
(2H, d, JZ8.8 Hz); 7.27 (2H, dd, JZ2.2 Hz);7.28–7.38 (10H,
m); 7.67 (2H, dd, J1Z2.2 Hz, J2Z8.8 Hz); These signals
ascribedtoformZ wereselectedfromspectrumofamixture of
isomers (around 50% E, and 50% Z).
3.3.5. Bis(4-tert-butylbenzo)-19-azocrown-7 (6) and
bis(4-tert-butylbenzo)-19-azoxycrown-7 (7). Water
(10 mL) was added drop by drop to vigorously stirred mixture
of dinitroderivative 2 (1.1 g, 2 mmol), stannous chloride
dihydrate (1.95 g, 8 mmol), sodium hydroxide (2.4 g) and
acetone (8 mL). The mixture was additionally stirred at 65 8C
for 4.5 h. The products were separated analogously to 4 and 5,
and finally purified by preparative thin-layer chromatography
using chloroform as mobile phase. The azocrown ether
crystallized in ‘mass’ as a mixture of isomers, 77 mg (8%),
mp 128–129 8C. The azoxycrown ether was obtained as
yellowish oil 100 mg (10%).
Azocrown 8, isomer E: dH (CDCl3, 500 MHz): 3.49–3.50
(2H, m); 3.63–3.64 (2H, m); 3.71–3.73 3.85 (4H, m);
3.90–3.92 (4H, m); 4.06 (2H, t, JZ4.8 Hz); 4.40 (2H, t, JZ
4.3 Hz); 7.11–7.15 (2H, m); 7.40–7.46 (6H, m); 7.48–7.52
(6H, m); 8.04 (2H, d, JZ2.2 Hz). Signals ascribed to this
form were selected from spectrum of a mixture of isomers
(75% E, and 25% Z). Mass Spec (MeOH, ESC) m/z
expected: 528.23. Found: 529.24 (MCH); IR (mixture of
isomers) (film) 2920, 2867, 1602, 1516, 1480, 1356, 1273,
1128, 1057, 942, 828, 758, 698 (cmK1).
Azocrown 6. Calculated for C28H41N2O5: [MCH peak]
m/zZ485.3015. Found: 485.3013. Anal. calcd C 69.40, H
8.32, N 5.78. Found C 68.95, H 8.27, N 5.74.
Azoxycrown 9. Calculated for C32H33N2O6: [MCH peak]
m/zZ541.2339. Found: 541.2335; (540.6) MS: m/eZ540.
Anal. calcd C 71.11, H 5.92, N 5.18. Found C 71.08, H
5.90, N 5.16; dH (CDCl3, 500 MHz): 3.63–3.64 (4H, m);
3.69–3.71 (4H, m); 3.94–3.97 (4H, m); 4.33–4.36 (4H, m);
7.14 (1H, d, JZ8.8 Hz); 7.20 (1H, d, JZ8.8 Hz);
7.31–7.37 (2H, m); 7.43–7.46 (4H, m); 7.57 (1H, dd,
J1Z2.4 Hz, J2Z8.8 Hz); 7.58–7.63 (4H, m); 7.66 (1H, dd,
J1Z2.4 Hz, J2Z8.8 Hz); 7.91 (1H, d, JZ2.0 Hz); 8.34
(1H, d, JZ2.4 Hz). Mass Spec (MeOH, ESC) m/z
expected: 540.23. Found: 541.23 (MCH); IR (film) 3016,
2925, 2872, 1606, 1517, 1478, 1456, 1278, 1136, 1055,
939, 890, 818, 757, 697 (cmK1).
Azocrown 6, isomer Z: dH (CDCl3, 500 MHz): 1.15 (18H,
s); 3.70–3.74 (8H, m); 3.86 (4H, t, JZ4.9 Hz); 3.98 (4H, t,
JZ4.9 Hz); 6.80 (2H, d, JZ8.8 Hz); 6.90 (2H, d, JZ
2.4 Hz); 7.15 (2H, dd, J1Z2.4 Hz, J2Z8.3 Hz).
Azocrown 6, isomer E: dH (CDCl3, 500 MHz): 1.35 (18H,
m); 3.50–3.52 (4H, m); 3.62–3.64 (4H, m) 3.89 (4H, t, JZ
4.4 Hz); 4.33 (4H, t, JZ4.4 Hz); 7.01 (2H, d, JZ8.8 Hz);
7.40 (2H, dd, J1Z2.4 Hz, J2Z8.3 Hz); 7.42 (2H, d, JZ
2.4 Hz). The signals ascribed to this form were selected
from spectrum of a mixture of isomers (around 75% E, and
25% Z). Mass Spec (MeOH, ESC) m/z expected: 484.29.
Found: 485.30 (MCH); IR (mixture of isomers) (film),
2960, 2870, 1601, 1497, 1461, 1395, 1360, 1260, 1134,
1053, 992, 938, 894, 815, 755 (cmK1).
4. Supplementary data
Azoxycrown 7. Calculated for C28H41N2O6: [MCH peak]
m/zZ501.2965. Found: 501.2967. Anal. calcd C 67.18, H
8.05, N 5.60. Found C 67.00, H 7.99, N 5.56; dH (CDCl3,
500 MHz): 1.34 (9H, s); 1.36 (9H, s); 3.62–3.65 (4H, m);
Crystallographic data for the structure reported in this paper
has been deposited with the Cambridge Crystallographic Data
Centre as Supplementary Publication No. CCDC 247296.
Copies of the data can be obtained free of charge from the

154
A. M. Skwierawska et al. / Tetrahedron 62 (2006) 149–154
6. Luboch, E.; Biedrzycka, A. Polish J. Chem. 2003, 77, 47–51.
7. (a) Luboch, E.; Biernat, J. F.; Muszalska, E.; Bilewicz, R.
Supramol. Chem. 1995, 5, 201–210. (b) Biernat, J. F.;
Luboch, E.; Skwierawska, A. M.; Bilewicz, A. R.;
Muszalska, E. Biocyber. Biomed. Eng. 1996, 16, 125–135.
(c) Luboch, E.; Biernat, J. F.; Kravtsov, V. Ch.; Simonov,
Yu. A. J. Incl. Phenom. 1998, 31, 109–118.
CCDC (12 Union Road, Cambridge CB2 1EZ, UK; Tel.: C44
1223 336 408; fax:C44 1223 336 003; e-mail:deposit@ccdc.
cam.ac.uk; www:http://ccdc.cam.ac.uk).
Acknowledgements
8. (a) Luboch, E.; Biernat, J. F.; Simonov, Y. A.; Dvorkin, A. A.
Tetrahedron 1998, 54, 4977–4990. (b) Pijanowska, D. G.;
Luboch, E.; Biernat, J. F.; Dawgul, M.; Torbicz, W. Sens.
Actuators B 1999, 58, 384–388. (c) Luboch, E.; Biernat, J. F.;
Simonow, Yu. A.; Kravtsov, V. Ch.; Bel’skii, V. K. Supramol.
Chem. 1999, 11, 109–118.
Financial support of this work from Gdansk University
of Technology, grant No. DS 014668/003 is kindly
acknowledged.
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