Synthesis, structure, and complexation behavior of 14- and 28-membered partially unsaturated thiacrown ethers

Article abstract of DOI:10.1002/hc.20678

Partially unsaturated 14- and 28-membered thiacrown ethers, 3 and 4, which possess alternating Z-carbon - carbon double bonds and propylene chains, were synthesized by stepwise reactions. The crystal structure of larger cyclic compound 4 was determined by

Full text of DOI:10.1002/hc.20678

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Heteroatom Chemistry
Volume 22, Number 3/4, 2011
Synthesis, Structure, and Complexation
Behavior of 14- and 28-Membered Partially
Unsaturated Thiacrown Ethers
Toshio Shimizu, Satoru Komatsuzaki, and Kazunori Hirabayashi
Department of Chemistry, Graduate School of Science and Engineering,
Tokyo Metropolitan University, Minami-Ohsawa, Hachioji, Tokyo 192-0397, Japan
Received 8 September 2010
also isolated and their complexation behavior was
ABSTRACT: Partially unsaturated 14- and 28-
studied [5–8]. Thiacrown ethers that possess both
membered thiacrown ethers, 3 and 4, which pos-
saturated and unsaturated bonds in their ring sys-
sess alternating Z-carbon–carbon double bonds and
tems are also interesting compounds on compar-
propylene chains, were synthesized by stepwise reac-
ison of their conformation, electrochemical prop-
tions. The crystal structure of larger cyclic compound
erties, and complexation behaviors with those of
4 was determined by X-ray crystallographic analy-
the corresponding saturated or unsaturated com-
sis. 14-Membered thiacrown ether 3 was found to
pounds. Among the thiacrown ethers that possess
be more easily oxidized electrochemically than larger
both saturated and unsaturated bonds, some 14-
cyclic compound 4 and the corresponding saturated
membered cyclic compounds that possess alternat-
system. Compounds 3 and 4 isomerized at tempera-
ing Z-carbon–carbon double bonds and propylene
tures exceeding 100◦C in solution to give cyclic com-
chains are known [9–15]. However, larger cyclic
pounds with E-olefin moieties but were stable at 80◦C
compounds featuring this system have not been syn-
in solution. Compound 3 formed 1:1 complexes with
thesized so far. Recently, we succeeded in synthesiz-
silver and copper ions, and 4 formed 1:2 complexes
ing a 28-membered partially unsaturated thiacrown
mainly in solution. A complex of 3 with mercury(II)
ether along with a smaller one. We report herein the
chloride was isolated, and its crystal structure was de-
synthesis and crystal structures of the partially un-
ꢀ
C
termined by X- ray analysis.
2011 Wiley Periodicals,
saturated thiacrown ethers, as well as their thermal
and complexation behaviors.
Inc. Heteroatom Chem 22:287–293, 2011; View this article
online at wileyonlinelibrary.com. DOI 10.1002/hc.20678
RESULTS AND DISCUSSION
Synthesis of Partially Unsaturated
Thiacrown Ethers
INTRODUCTION
Following the synthesis of the first thiacrown ether
by Meadow and Reid [1], thiacrown ethers of vari-
ous sizes have been synthesized [2–4]. Unsaturated
thiacrown ethers, of which all sulfur atoms are
connected by carbon–carbon double bonds, were
First of all, direct synthesis was attempted.
When disodium cis-ethenedithiolate and 1,3-
dibromopropane were stirred in acetonitrile so-
lution, a seven-membered cyclic product, (Z)-3,7-
dithiacycloheptene [16,17], was obtained together
with a trace amount of the 1:2 adduct but the desired
larger thiacrown ether was not obtained. Therefore,
a stepwise synthesis was examined. The reaction
of cis-ethenedithiolate with 2 equiv of 3-bromo-1-
propanol in acetonitrile gave diol 1 (Scheme 1).
287
Dedicated to Professor Kin-ya Akiba on the occasion of his 75th
birthday.
Correspondence to: Toshio Shimizu; e-mail: shimizu-toshio@
tmu.ac.jp.
c
ꢀ
2011 Wiley Periodicals, Inc.

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
288 Shimizu, Komatsuzaki, and Hirabayashi
S
S
S
S
OH
OH
S
SNa
SNa
S
Br
OH
+
MeCN
15.05
S
(2 eq)
4.06
S
S
1 (75%)
S
SNa
, Additive
S
S
OTs
OTs
TsCl, Et3N
CH2Cl2
SNa
DMF
4.16
3.95
3.86
2 (73%)
S
S
S
S
S
S
S
S
S
S
+
FIGURE 1 Crystal structure of 4. Hydrogen atoms are
S
2
3
˚
omitted for clarity. C(sp ) S: 1.75–1.76 A; C(sp )–S: 1.81–
◦
◦
S
˚
1.82 A; C S C: 99.5–100.3 ; S C C S: 0.6–1.0 .
3
4
Yield (%)
X-ray crystallographic analysis (Fig. 1). The X-ray
analysis showed that all of the olefin moieties have
the Z-geometry, and the bond lengths, bond an-
gles, and dihedral angles are almost normal. It was
also found that the molecule has a slender struc-
ture, and the atomic distance between the farthest
Additive
3
4
3.8
5.8
4.5
7.0
2.5
1.5
12.4
16.0
7.8
14.0
8.2
Na2CO3
K2CO3
Cs2CO3
AgBF4
AgOTf
˚
sulfur atoms is 15.05 A, which is nearly twice that
of a 14-membered compound 3 [11]. The packing
6.6
structure also showed a columnar structure. The dis-
tance between the stacked molecules is 5.23 A, and
˚
SCHEME 1 Synthesis of partially unsaturated thiacrown
ethers.
the atomic distances between sulfur atoms of neigh-
˚
boring molecules are 3.86–4.16 A, which are slightly
After transformation of the hydroxyl group into
tosylate, the reaction of 2 with cis-ethenedithiolate
in dimethylformamide (DMF) solution afforded de-
sired partially unsaturated 28-membered thiacrown
ether 4, together with a small amount of 14-
membered thiacrown ether 3. Compound 3 was pre-
viously synthesized by the reduction of the corre-
sponding cyclodiyne by Gleiter and co-workers [11].
In acetonitrile solution, however, the reaction did
not proceed. Expecting the template effect, the re-
actions were examined in the presence of several
salts, such as sodium carbonate, potassium carbon-
ate, cesium carbonate, silver tetrafluoroborate, and
silver triflate. However, no remarkable improvement
of the yield was observed. In these reactions, no 21-
membered cyclic product was detected.
longer than twice the van der Waals radii of sulfur.
Electrochemistry of Partially Unsaturated
Thiacrown Ethers
Partially unsaturated thiacrown ethers 3 and 4
showed irreversible cyclic voltammograms (Fig. 2).
The potential was scanned at 100 mVs−1 versus
Fc/Fc+ toward negative and back again. Two oxi-
dation peaks were observed for each macrocycle;
compound 3 showed oxidation peaks at 0.35 and
0.79 V, and larger cyclic system 4 showed peaks at
0.52 and 0.87 V. These results indicate that smaller
partially unsaturated thiacrown ether 3 is more eas-
ily oxidized than the larger one perhaps because
the delocalization of the resulting cation effectively
takes place in the 14-membered cyclic system by in-
tramolecular interaction between the sulfur atoms.
The oxidation potentials of saturated thiacrown
ether 5 [18,19] were observed at 0.77 and 1.08 V un-
der the same conditions, and it was found that the
Crystal Structure of Partially Unsaturated
Thiacrown Ether
The crystal structure of 28-membered partially un-
saturated thiacrown ether 4 was determined by
Heteroatom Chemistry DOI 10.1002/hc

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Synthesis, Structure, and Complexation Behavior of 14- and 28-Membered Thiacrown Ethers 289
14-membered partially unsaturated thiacrown ether
3 was more easily oxidized than the corresponding
saturated 5. A similar trend was also observed in the
case of 4; 28-membered saturated thiacrown ether 6
[20] showed two oxidation peaks at 0.73 and 1.02 V.
mined by X-ray analysis (Fig. 4). Larger partially
unsaturated thiacrown ether 4 also reacted at tem-
peratures exceeding 100◦C, and the formation of Z-
1
E-isomerized products was confirmed by H NMR
measurements. However, the reaction was compli-
cated, probably due to the existence of many double
bonds in the molecule, and only a trace amount of
E,Z,Z,Z-isomer 10 was obtained.
S
S
S
S
S
S
S
S
10
Thermal Stability and Isomerization of Partially
Unsaturated Thiacrown Ethers
To examine the molecular strains of the Z, Z-,
E, Z-, and E, E-isomers of 14-membered partially
unsaturated thiacrown ethers 3, 7, and 8, a theo-
retical study was carried out. As a model molecule
for comparison, 1,2-bis(ethylthio)ethene was calcu-
lated. The results showed that the E-isomer of the
model molecule was more stable than the Z-isomer
by 1.9 kcal mol−1. In the case of the 14-membered
cyclic compounds, E, E-isomer 8 was found to be
more stable than Z, Z-isomer 3 by 3.8 kcal mol−1,
and E, Z-isomer 7 was also more stable than 3 by
1.6 kcal mol−1. These values correspond well to the
results of calculation for the model molecules, indi-
cating that all of the isomers of the 14-membered
cyclic compound have strain-free geometries. The
crystal structures of 3 [11] and 7 also support this
result.
When the thermal stability of 3 was examined
in a nuclear magnetic resonance (NMR) tube,
Z-E-isomerization of the olefin moieties was ob-
served upon heating. Compound 3 was stable at 80◦C
but gradually decomposed at temperatures exceed-
ing 100◦C in dimethyl sulfoxide (DMSO)-d6 to show
1
new signals on the H NMR spectra assignable to
Z-E-isomerized products 7 and 8 and ring-reduced
seven-membered cyclic compound 9. The changes
1
in the H NMR spectra of the olefin protons of 3
are shown in Fig. 3. At 140◦C, the isomerization re-
action was accelerated and E, Z-isomer 7 was ob-
tained up to 60% yield. Trace amounts of the isomers
were isolated by silica-gel chromatography, and the
1
structures were assigned on the basis of H and 13C
NMR spectra. The structure of 7 was finally deter-
Complexation Behavior of Partially Unsaturated
Thiacrown Ethers
In the cases of corresponding saturated 14- and 28-
membered thiacrown ethers, silver complexes have
been obtained [21–23]. We also examined the com-
plexation of 3 and 4 with silver ion using silver triflu-
oroacetate and tetrafluoroborate in several solvents.
However, no complex of 3 and 4 was obtained as the
sole product. In solution, however, changes in the
chemical shifts were observed on their 1H NMR spec-
tra. Therefore, titration experiments for the com-
plexation of 3 and 4 with silver ion were carried
0
3
0.79
0.87
4
0.35
0.52
0.5
1
out in solution. The H signals of 3 and 4 shifted to
lower field with the addition of silver trifluoroacetate
in acetone−d6. Job’s plots of the complexation of 3
and 4 with silver trifluoroacetate are shown in Fig. 5;
the chemical shifts of protons for sp3-carbons neigh-
boring sulfur atoms were used for the plots. The
1.5
1
0
Potential (V)
FIGURE 2 Cyclic voltammograms of 3 and 4 in acetonitrile.
Heteroatom Chemistry DOI 10.1002/hc

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
290 Shimizu, Komatsuzaki, and Hirabayashi
140oC
3
S
DMSO-d6
S
S
S
S
S
S
S
S
S
S
S
+
+
9
7
8
S
S
3
0 h
4 h
FIGURE
4
Crystal structure of 7. C(sp2) S: 1.72–
3
◦
˚
˚
3 + 7
1.83 A; C(sp ) S: 1.78–1.82 A; C S C: 98.8–106.3 ;
S C C S(E-olefin): 171.9◦; S C C S(Z-olefin): −1.9◦.
7
8
1.6
1.2
0.8
0.4
0
(a) 3
15 h
9
35 h
6.4
6.2
6.0
5.8
ppm
100
0
0.25
0.5
0.75
1
(%)
[3] / {[CF3CO2Ag]+[3]}
3
80
60
40
20
7
(b) 4
1.2
0.8
0.4
0
8
9
0
0
10
20
30
40
Time (h)
FIGURE 3 Thermal Z-E-isomerization of partially unsatu-
rated thiacrown ether 3 at 140◦C.
0
0.25
0.5
0.75
1
[4] / {[CF3CO2Ag]+[4]}
FIGURE 5 Job’s plots of (a) 3 and (b) 4 with silver trifluo-
roacetate in acetone-d6.
results indicate that 14-membered thiacrown ether 3
forms a 1:1 complex with silver trifluoroacetate, and
larger thiacrown ether 4 affords a 1:2 complex in
acetone solution; these results are similar to those of
the corresponding saturated systems obtained from
the titration plots. Similar results were obtained in
acetonitrile-d3 solution. It was also found that com-
pound 3 formed a 1:1 complex with copper(II) tri-
fluoromethanesulfonate, and 4 gave a 1:2 complex
mainly in acetone-d6 solution.
3 afforded stable 1:2 complex 11. The crystal struc-
ture was determined by X-ray analysis. The crystal
structure demonstrated that two sulfur atoms coor-
dinate to a mercury atom, as shown in Fig. 6; this
structure is similar to that for the mercury complex
of corresponding saturated 14-membered thiacrown
ether 5 [24].
In the complexation with mercury(II) chloride,
14-membered partially unsaturated thiacrown ether
Heteroatom Chemistry DOI 10.1002/hc