Preparation and structure determination of 28-membered and 42-membered cyclic molecules linked with two or three disulfide bonds

Article abstract of DOI:10.1080/17415993.2011.640330

4,7-Diethylbenzo[1,2,3]trithioles (1a-1c), 4,8-diethylbenzo[1,2-d:4,5- d′]bis[1,2,3]trithiole (1d), and 6, 10-diethyl[1,2,3]trithiolo[h] benzopentathiepin (1d′) were treated with sodium borohydride and 0.5 equiv. of p-xylylene dibromide to produce bridged

Full text of DOI:10.1080/17415993.2011.640330

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Preparation and structure
determination of 28-membered and 42-
membered cyclic molecules linked with
two or three disulfide bonds
Takeshi Kimura a , Hayato Ichikawa b , Toshiyuki Fujio b , Yasushi
Kawai c & Satoshi Ogawa b
a Center for Instrumental Analysis, Iwate University, Morioka,
Iwate, 020-8551, Japan
b Department of Chemistry and Bioengineering, Iwate University,
Morioka, Iwate, 020-8551, Japan
c Nagahama Institute of Bio-Science and Technology, Nagahama,
Shiga, 526-0829, Japan
Published online: 05 Dec 2011.
To cite this article: Takeshi Kimura , Hayato Ichikawa , Toshiyuki Fujio , Yasushi Kawai & Satoshi
Ogawa (2012) Preparation and structure determination of 28-membered and 42-membered cyclic
molecules linked with two or three disulfide bonds, Journal of Sulfur Chemistry, 33:1, 17-25, DOI:
10.1080/17415993.2011.640330
To link to this article: http://dx.doi.org/10.1080/17415993.2011.640330
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Journal of Sulfur Chemistry
Vol. 33, No. 1, February 2012, 17–25
Preparation and structure determination of 28-membered and
42-membered cyclic molecules linked with two or three disulfide
bonds
Takeshi Kimuraa*, Hayato Ichikawab, Toshiyuki Fujiob, Yasushi Kawaic and Satoshi Ogawab
aCenter for Instrumental Analysis, Iwate University, Morioka, Iwate 020-8551, Japan; bDepartment of
Chemistry and Bioengineering, Iwate University, Morioka, Iwate 020-8551, Japan; cNagahama Institute of
Bio-Science and Technology, Nagahama, Shiga 526-0829, Japan
(Received 24 October 2011; final version received 9 November 2011)
4,7-Diethylbenzo[1,2,3]trithioles (1a–1c), 4,8-diethylbenzo[1,2-d:4,5-dꢀ]bis[1,2,3]trithiole (1d), and 6,
10-diethyl[1,2,3]trithiolo[h]benzopentathiepin (1dꢀ) were treated with sodium borohydride and 0.5 equiv.
of p-xylylene dibromide to produce bridged molecules 2a–2d with two thiol groups. On oxidation of
2a with iodine in the presence of triethylamine, 28-membered macrocycle 3a, linked with two disulfide
bonds, was obtained via a dimeric cyclization reaction, instead of a monomeric 14-membered macrocycle.
Compounds 2b–2d were similarly treated with iodine and triethylamine to give 28-membered macrocycles
3b–3d. In the case of the reaction of 2c, a trimeric reaction occurred to produce 42-membered macrocycle 4
together with 3c. The structures of the cyclic molecules were determined by NMR and mass spectrometry,
which was further supported by X-ray crystallographic analysis.
R
R
R
Et Et
R
Et
S
S
Et
Et
Et
Et
Et
S
S
R
R
S
S
R
R
I2 / Et3N
CH2Cl2
SH
HS
2R = SSS
R = H
S
R
S
R
Et
R
S
S
Et
R
R = SMe
2R = SC2H4S
Et Et
Keywords: macrocycle; disulfide; thiacrown; benzotrithiole and oxidation
*Corresponding author. Email: kimura@iwate-u.ac.jp
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2012 Taylor & Francis
http://dx.doi.org/10.1080/17415993.2011.640330
http://www.tandfonline.com

18 T. Kimura et al.
1. Introduction
Thiacrown ethers and thiacalixarenes have been attracted much attention because of their
molecular-recognition properties, inclusion of metal atoms, and functionalities of complexes pro-
duced (1–4). In addition, thiacrown ethers and thiacalixarenes show high affinity for heavy metals
such as mercury, silver, platinum, gold, and so on. So, these compounds have potential utility
to remove highly toxic metal ions or to recover important metals from industrially contaminated
water. In thiacrown ether ring systems, introducing one or more unsaturated linkages is effective to
control their structure, cavity size, and a number of metal atoms inserted, which could affect their
character as functional materials (5). Cis and trans bond systems, in particular, can dramatically
change the conformation and functionality of the molecule. In addition, while thiacrown ethers
and related compounds have been prepared from many types of substrates, the disulfide linkage
could be one of the useful key systems for construction of the desired molecules (6).
On the other hand, there are many reports with respect to the preparation, structure determi-
nation, biological activity, and electrochemical properties of benzo-annelated cyclic polysulfides
(7). In related studies, we recently described optical and electrochemical properties of thianthrenes
and phthalocyanines fused with one through four trithiole rings (8,9) and related molecules (10).
To prepare the macrocyclic compounds with sulfur functional groups, 5,6-bis(methylthio)-4,7-
diethylbenzo[1,2,3]trithiole (1a), 5,6-ethylenedithio-4,7-diethylbenzo[1,2,3]trithiole (1b), 4,7-
diethylbenzo[1,2,3]trithiole 2-oxide (1c), 4,8-diethylbenzo[1,2-d:4,5-dꢀ]bis[1,2,3]trithiole (1d),
and 6,10-diethyl[1,2,3]trithiolo[h]benzopentathiepin (1dꢀ) were reacted with sodium borohydride
and p-xylylene dibromide, and the dithiol derivatives 2a–2d, produced by these reactions, were
then oxidized with iodine in the presence of triethylamine. This process gave 28-membered
cyclic molecule 3a–3d with two disulfide bonds via dimeric cyclization reactions. In addition, 2c
afforded the 42-membered macrocyclic molecule 4 by an oxidative trimerization reaction. This
paper describes the preparation and structure determination of macrocyclic molecules 3a–3d and
4 connected by p-xylylendithio linkers and disulfide bonds.
2. Results and discussion
To prepare sulfur containing macrocyclic molecules, 1d with two trithiole rings (11) was ini-
tially treated with 1 equiv. of sodium borohydride and p-xylylene dibromide in the presence of
potassium carbonate in THF/methanol. However, an insoluble yellow material was immediately
produced in this reaction and hence we could not analyze the product. This insoluble mate-
rial could be produced by a random oligomerization reaction of the reactants. To simplify the
reaction system and to avoid the oligomerization reaction, 1a was utilized as a substrate with
only 0.5 equiv. of p-xylylene dibromide (Scheme 1). We previously reported that when 6,10-
dimethoxy[1,2,3]trithiolo[h]benzopentathiepin was treated with sodium borohydride and then
methyl iodide, 6,9-dimethoxybenzopentathiepin, with one methylthio and one thiol group, was
obtained as a major product (11a). Consequently, using a similar procedure, 1a was reduced with
sodium borohydride and then treated with 0.5 equiv. of p-xylylene dibromide to give dithiol deriva-
tive 2a, bridged by a xylylenedithio group, in 55% yield as a stable colorless powder (Scheme 1).
Compound 2a is soluble in chloroform, dichloromethane, and THF.
In the 1H NMR spectrum of 2a, there are two triplet and two quartet signals for the ethyl groups,
two singlet peaks for the two different methylthio groups, and two singlet signals for the CH2 and
aromatic p-xylylene protons. In addition, one singlet peak for two thiol groups was observed at
δ = 6.31 ppm.The IR spectrum showed the absorption of the thiol group at 2474 cm−1. Compound
2a is stable and oxidation of the thiol groups with oxygen did not proceed under air.

Journal of Sulfur Chemistry 19
Et
Et
Et
Et
Et
R
R
R
R
S
S
R
R
S
S
NaBH4, THF/EtOH
(X)n
Br
0.5 eq.
SH
HS
Br
Et
2a: 55%
2b: 80%
2c: 63%
1a: X = S, n = 1, R = SMe
1b: X = S, n = 1, 2R = SC2H4S
1c: X = SO, n = 1, R = H
2d: 74% (from 1d)
2d: 76% (from 1d')
1d: X = S, n = 1, 2R = SSS
1d': X = S, n = 3, 2R = SSS
Scheme 1. Preparation of dithiol derivatives 2a–2d.
Since 2a was obtained in moderate yield, 1b–1d were similarly treated with sodium boro-
hydride and then p-xylylene dibromide to produce the corresponding dithiol derivatives 2b–2d,
respectively (2b: 80%, 2c: 63%, and 2d: 74% from 1d and 76% from 1dꢀ). Compounds 2b–2d are
stable and soluble in chloroform, dichloromethane, and THF. 1H NMR spectra of these products
showed the anticipated signals for the ethyl, thiol, and xylylene groups. In addition, a multiplet
signal for the ethylenedithio groups was observed in the spectrum of 2b, and the spectrum of
2c showed the aromatic protons as an AB quartet. It also appears that the chemical shifts of the
singlet signal of the thiol groups were affected by the substituents next to the two ethyl groups;
2a: δ = 6.31 ppm, 2b: δ = 6.16 ppm, 2c: δ = 5.88 ppm, and 2d: δ = 6.00 ppm.
It was expected that two dithiol groups on the benzene rings of 2a–2d could be oxidized
to produce the disulfide bond. If the oxidative bond formation proceeds exclusively via an
intramolecular reaction between the two thiol groups, 2a–2d would produce 14-membered ring
macrocycles. To avoid intermolecular oligomerization of 2a–2d, dilute reaction conditions and a
mild oxidizing reagent were utilized for the disulfide formation. Thus, a dichloromethane solu-
tion of 2a was slowly dropped into a dichloromethane solution of triethylamine together with a
dichloromethane solution of iodine and the reaction mixture was stirred for 12 h at room temper-
ature (Scheme 2). With this procedure, intermolecularly dimerized 3a with two disulfide bonds
was surprisingly obtained in 42% yield as a colorless and powdery material after purification
with column chromatography and gel permeation chromatography (GPC). Compound 3a is sta-
ble under ambient conditions (room temperature and under 1 atm of air) and easily soluble in
chloroform, dichloromethane, and THF.
In the 1H NMR spectrum of 3a, we could observe two triplet and two quartet signals for the ethyl
groups, two singlet peaks for the methylthio groups, and two singlet peaks for the xylylene group
as expected (vida supra). In addition, the signal of the thiol group disappeared in the spectrum.
Interestingly, one ethyl group of 3a appeared at δ = 0.61 (t) and 2.86 (q) ppm, which is at a higher
magnetic field than that of 2a: δ = 1.10 (t) and 3.13 (q) ppm, suggesting that the ethyl groups of 3a
aremagneticallyshieldedbyaromaticringswhichisclearlyafunctionoftheconformationadopted
by the product. Meanwhile, two singlet signals for the xylylene protons were observed at δ = 4.12
(SCH2) and 7.57 (ArH) ppm, which are at lower magnetic field than that of 2a: δ = 3.90 (SCH2)
and 7.07 (ArH) ppm. Fast atom bombardment mass spectrometry (FABMS) measurement showed
a signal at m/z = 1360.13 [M+], which corresponds to the molecular ion peak of a dimerized
macrocycle. Therefore, the structure of compound 3a is a dimerized 28-membered ring system
instead of a monomeric 14-membered structure. The 14-membered macrocycle was not obtained
under the reaction conditions.
Compounds 2b–2d were also oxidized by a similar method as described above to produce
3b–3d (3b: 76%, 3c: 41%, and 3d: 15%), after purification with column chromatography and

20 T. Kimura et al.
GPC. Compound 3d was unstable compared with 3a–3c and easily produced an insoluble yellow
material. In the 1H NMR spectra of 3b–3d, signals for one of the ethyl groups were observed at
higher magnetic fields than those of 2b–2d. Furthermore, singlet peaks for the xylylene group of
3b–3d appeared at similar chemical shifts as those observed for 3a. These results suggested that
the structures of 3b–3d are similar to those of 3a. In addition, the molecular ion peak of 3c was
observed by FABMS measurement: m/z = 992.28 [M+], suggesting that 3c is a 28-membered
ring system.
R
R
R
Et Et
R
Et
S
S
Et
Et
Et
Et
Et
S
S
R
R
S
S
R
R
I2 / Et3N
CH2Cl2
SH
HS
2a-c
S
R
S
R
Et
R
S
S
Et
R
a: R = SMe
b: 2R = SC2H4S
c: R = H
Et Et
d: 2R = SSS
3a: 42%
3b: 76%
3c: 41%
3d: 15%
Scheme 2. Preparation of 28-membered macrocycles 3a–3d.
Compound3cproducedthinneedlecrystalsafterrecrystallizationanditsX-raycrystallographic
analysiswasperformedtodeterminethestructure(12). However, wecouldnotobtainasatisfactory
final R factor, and bond lengths and angles of the one of the ethyl groups show unusual values.
Nevertheless, we could verify the molecular structure and the results showed the dimerized 28-
membered ring system of 3c as described above, even though the structure refinement was not
sufficient. Unfortunately, theresultscouldnotbeimprovedbyusingothercrystals. Inthemolecule,
the two benzene rings of the xylylene groups are shown to be parallel to each other and separated
by a distance of 7.7 Å. The distance between the two disulfide bonds is 8.6 Å. In addition, the
molecular structure showed that one ethyl group exists above the adjacent benzene ring, which
gives rise to the higher magnetic field shift observed for one of the ethyl groups in the 1H NMR
spectrum of 3c.
On the other hand, it appeared that 2c afforded an additional cyclized product 4 as a color-
less powder in 10% yield together with 3c, after GPC purification. The results of GPC analysis
suggested that the molecular weight of this compound is larger than that of 3c. In the 1H NMR
spectrum of 4, we can observe two triplet signals (δ = 0.99 and 1.09 ppm) and two quartet signals
for the ethyl groups (δ = 2.57 and 2.79 ppm), two singlet peaks for the xylylene group (δ = 3.81
and 7.05 ppm), andAB quartet for the benzene rings. The signal of the thiol group was not observed
in the spectrum and the chemical shifts of the xylylene group appeared at slightly higher magnetic
fields than those of 3c. Finally, the molecular ion peak of 3c was obtained with an FABMS mea-
surement: m/z = 1488.46 [M+], which suggests that 4 is a trimerized 42-membered macrocyclic
molecule (Figure 1). On the other hand, we could not obtain 42-membered macrocyclic molecules
by the oxidation of 2a, 2b, and 2d.

Journal of Sulfur Chemistry 21
Et
S
Et
S
S
S
Et
Et
Et
Et
S
S
Et
Et
S
S
S
S
S
S
Et
Et Et
4
Et
Figure 1. The structure of 28-membered macrocycle 4.
To determine the electrochemical properties of the macrocycles, reduction potentials of 3b
and 3c were measured by cyclic voltammetry using Ag/AgNO3 as a reference electrode (solvent:
CH2Cl2, scan rate: 200 mV/s). Both compounds 3b and 3c showed one quasi-reversible reduction
potential; 3b: E1/2 = −1.22V and 3c: E1/2 = −1.22V. These potentials are similar to the value
for bis(2,5-diethylphenyl) disulfide: E1/2 = −1.22V. On the other hand, to measure the oxidation
potential of 3c, when the cyclic voltammetry was scanned from 0 to 2.0 V, the value of the
current was gradually increased after about 1.05 V but no peak potential was observed in the
voltammogram.
As a preliminary experiment, we treated 3c with excess amounts of silver trifluoroacetate in the
NMR tube (solvent: CDCl3/acetone-d6). The signals of 3c were broadened and changed to new
signals in the spectrum, suggesting that the silver complex of 3c was produced in the solution.
However, the signals in the spectrum become complex in several hours.
3. Conclusion
Cyclic polysulfides 1a–1dꢀ were treated with sodium borohydride and 0.5 equiv. of p-xylylene
dibromide to produce bridged molecules 2a–2d with two thiol groups. Oxidative dimerization
of 2a proceeded on treatment with iodine in the presence of triethylamine, which gave a 28-
membered macrocycle 3a linked with two disulfide bonds. Similar reactions of 2b and 2d with
iodine produced dimeric macrocycles 3b and 3d, respectively, while 2c afforded 28-membered
macrocycle 3c and 42-membered macrocycle 4 under the reaction conditions. Although 2a–
2d did not produce 14-membered macrocycles by oxidative intramolecular cyclization, these
molecules can be utilized as the building unit for 28-membered and 42-membered macrocycles.
The structures of the molecules were determined with NMR, FABMS, and X-ray crystallographic
analysis. The chemical shifts of the ethyl and xylylene groups were different for the 28-membered
and 42-membered macrocycles.

22 T. Kimura et al.
4. Experimental
4.1. General
NMR spectra were measured on Bruker DRX-400 andAVANCE-500 III spectrometers. IR spectra
were recorded using a JASCO FT-7300 spectrometer. Mass spectra were obtained using a JEOL
JMS-700 mass spectrometer. Elemental analyses were performed using a Yanako MT5 analyzer.
A JAI LC-908 model was used for GPC. A Hokuto Denko Co. Model HAB-151 apparatus was
employed for measuring oxidation potentials.
4.2. Redox potentials
All measurements were performed by cyclic voltammetry using Ag/AgNO3 (0.01 mol/l) as a
reference electrode, glassy carbon as a working electrode, and Pt as a counter-electrode (scan
rate: 200 mV/s). A solution of n-Bu4NClO4 in CH2Cl2 (0.1 mol/l) was used as an electrolyte.
The oxidation potential of ferrocene was observed at E1/2 = 0.09V by the apparatus without any
correction.
4.3. 5,6-Bis(methylthio)-4,7-diethylbenzotrithiole (1a) (13),
5,6-ethylenedithio-4,7-diethylbenzotrithiole (1b) (8), 4,7-diethylbenzotrithiole 2-oxide
(1c) (14), 4,8-diethylbenzo[1,2-d:4,5-dꢀ]bis[1,2,3]trithiole (1d) (11b), and
6,10-diethyl[1,2,3]-trithiolo[h]benzopentathiepin (1dꢀ) (10b)
Compounds 1a–1dꢀ were prepared by methods described previously.
4.4. Preparation of dithiol 2a
Compound 1a (321 mg, 1.0 mmol, in 50 ml of THF and 5 ml of EtOH) was treated with NaBH4
(1.2 equiv.) for 30 min and then p-xylylene dibromine (0.5 equiv.) was added to the solution. The
mixture was stirred at room temperature for 12 h. After treatment with aqueous HCl, the solvent
was evaporated and the aqueous solution was extracted with CH2Cl2. The extract was dried over
MgSO4 and the solvent was evaporated. The product was purified by column chromatography
(silica gel, CCl4) to produce 2a in 55% yield; colorless crystals; m.p. 178◦C; 1H NMR (400 MHz,
CDCl3) δ 1.10 (t, J = 7.4 Hz, 6H, CH3), 1.25 (t, J = 7.4 Hz, 6H, CH3), 2.35 (s, 6H, SCH3), 2.45
(s, 6H, SCH3), 3.13 (q, J = 7.4 Hz, 4H, CH2), 3.19 (q, J = 7.5 Hz, 4H, CH2), 3.90 (s, 4H, SCH2),
6.31 (s, 2H, SH), 7.07 (s, 4H, ArH); 13C NMR (101 MHz, CDCl3) δ 12.3, 14.5, 32.3, 32.4, 39.7,
129.2, 129.3, 134.9, 136.0, 137.1, 140.9, 143.00, 143.0321.7, 32.1, 141.7, 142.1, 142.7; IR (KBr)
2474 cm−1 (SH); MS (m/z) 682 (M+); Anal. Calcd for C32H42S8: C, 56.26; H, 6.20%. Found: C,
56.59; H, 6.12%.
4.5. Preparation of dithiol 2b
1
Yield: 80%; yellow crystals; m.p. 158.5◦C; H NMR (400 MHz, CDCl3) δ 1.08 (t, J = 7.5 Hz,
6H, CH3), 1.21 (t, J = 7.5 Hz, 6H, CH3), 2.99 (q, J = 7.5 Hz, 4H, CH2), 3.01 (q, J = 7.5 Hz, 4H,
CH2), 3.13–3.24 (m, 8H, CH2), 3.89 (s, 4H, SCH2), 6.16 (s, 2H, SH), 7.06 (s, 4H, ArH). Anal.
Calcd for C32H38S8: C, 56.59; H, 5.64%. Found: C, 56.12; H, 5.68%.

Journal of Sulfur Chemistry 23
4.6. Preparation of dithiol 2c
Yield: 63%; colorless crystals; m.p. 81–82◦C; 1H NMR (400 MHz, CDCl3) δ 1.09 (t, J = 7.4 Hz,
6H, CH3), 1.27 (t, J = 7.4 Hz, 6H, CH3), 2.66 (q, J = 7.4 Hz, 4H, CH2), 2.69 (q, J = 7.4 Hz, 4H,
CH2), 3.87 (s, 4H, SCH2), 5.88 (s, 2H, SH), 7.02 (s, 4H, ArH), 6.92, 7.07 (ABq, J = 7.9 Hz, 4H,
ArH); 13C NMR (126 MHz, CDCl3) δ 13.6, 15.8, 29.1, 29.2, 39.3, 124.9, 128.8, 129.0, 129.8,
136.4, 138.8, 140.3, 147.6; MS (m/z) 498 (M+); Anal. Calcd for C28H34S4: C, 67.42; H, 6.87%.
Found: C, 67.09; H, 6.85%.
4.7. Preparation of dithiol 2d
Method A: Compound 1dꢀ (1295 mg, 3.35 mmol, in 300 ml of THF and 300 ml of EtOH)
was treated with NaBH4 (127 mg, 3.35 mmol) for 30 min and p-xylylene dibromine (442 mg,
1.7 mmol) was added to the solution. The mixture was stirred at room temperature for 12 h. After
treatment with aqueous HCl, the solvent was evaporated and the aqueous solution was extracted
with CH2Cl2. The extract was dried over MgSO4 and the solvent was evaporated. Then the prod-
uct was purified by column chromatography (silica gel, n-hexane to n-hexane:CHCl3 = 2:1) to
produce 2d in 76% yield (871 mg).
Method B: Compound 1d (447 mg, 1.39 mmol, in 100 ml of THF and 100 ml of EtOH) was
similarly treated with NaBH4 and p-xylylene dibromide to produce 2d in 74% yield (351 mg);
yellow powder; m.p. 135–138◦C; 1H NMR (400 MHz, CDCl3) δ 1.07 (t, J = 7.5 Hz, 6H, CH3),
1.32 (t, J = 7.5 Hz, 6H, CH3), 2.78 (q, J = 7.5 Hz, 4H, CH2), 2.86 (q, J = 7.5 Hz, 4H, CH2),
3.88 (s, 4H, SCH2), 6.00 (s, 2H, SH), 7.06 (s, 4H, ArH); 13C NMR (101 MHz, CDCl3) δ 12.3,
14.5, 32.3, 32.4, 39.7, 129.2, 129.3, 134.9, 136.0, 137.1, 140.9, 143.00, 143.03. Anal. Calcd for
C28H30S10: C, 48.94; H, 4.40%. Found: C, 48.88; H, 4.22%.
4.8. Cyclization of 2a
A solution of 2a (137 mg, 0.2 mmol in 100 ml of CH2Cl2) was slowly dropped to a solution of Et3N
(0.56 ml, 0.4 mmol in 100 ml of CH2Cl2) together with a solution of I2 (51 mg, 0.2 mmol in 100 ml
of CH2Cl2). The reaction mixture was stirred for 12 h at room temperature. After treatment with
aqueous NaHSO3, the solution was dried over MgSO4 and the solvent was evaporated. Then the
product was purified by column chromatography (silica gel, n-hexane to n-hexane:CHCl3 = 1:1)
1
and GPC to produce 3a in 42% yield; 3a: colorless powder; m.p. 204◦C; H NMR (400 MHz,
CDCl3) δ 0.61 (t, J = 7.3 Hz, 12H, CH3), 1.27 (t, J = 7.3 Hz, 12H, CH3), 2.38 (s, 12H, SCH3),
2.46 (s, 12H, SCH3), 2.86 (q, J = 7.3 Hz, 8H, CH2), 3.52 (q, J = 7.3 Hz, 8H, CH2), 4.12 (s, 8H,
SCH2), 7.57 (s, 8H, ArH); 13C NMR (101 MHz, CDCl3) δ 15.5, 16.6, 21.7, 22.0, 29.0, 30.0, 42.4,
129.7, 136.2, 142.2, 143.8, 144.8, 145.8, 151.7, 153.6; FABMS m/z = 1360.13 [M+]. Anal. Calcd
for C64H80S16: C, 56.85; H, 6.36%. Found: C, 56.59; H, 6.12%.
4.9. Cyclization of 2b
3b: 76%; colorless crystals; m.p. 169–170◦C; 1H NMR (400 MHz, CDCl3) δ 0.71 (t, J = 7.3 Hz,
12H, CH3), 1.23 (t, J = 7.3 Hz, 12H, CH3), 2.71 (q, J = 7.3 Hz, 8H, CH2), 3.14–3.24 (m, 16H,
CH2), 3.33 (q, J = 7.3 Hz, 8H, CH2), 4.07 (s, 8H, SCH2), 7.52 (s, 8H, ArH); 13C NMR (101 MHz,
CDCl3) δ 14.0, 14.9, 26.8, 27.4, 30.6, 30.9, 42.5, 129.6, 134.6, 135.6, 136.3, 137.5, 140.8, 145.6,
146.9. Anal. Calcd for C64H72S16: C, 56.76; H, 5.36%. Found: C, 56.66; H, 5.42%.

24 T. Kimura et al.
4.10. Cyclization of 2c
To a solution of 2c (85.3 mg, 17 mmol, in 100 ml of CHCl3) was added Et3N (0.1 ml, 0.72 mmol)
and I2 (107 mg, 0.42 mmol). The mixture was stirred for 110 h. After treatment with aqueous
NaHSO3, the solvent was evaporated, and the aqueous solution was extracted with CHCl3. The
extract was dried with MgSO4 and the solvent was evaporated. Then the product was purified by
column chromatography (silica gel, n-hexane:CHCl3) and GPC to produce 3c in 41% (34.8 mg)
and 4 in 10% (8.2 mg); 3c: colorless powder; m.p. 206◦C (decomp.); 1H NMR (400 MHz, CDCl3)
δ 0.84 (t, J = 7.5 Hz, 12H, CH3), 1.24 (t, J = 7.5 Hz, 12H, CH3), 2.42 (q, J = 7.5 Hz, 8H, CH2),
3.00 (q, J = 7.5 Hz, 8H, CH2), 4.03 (s, 8H, SCH2), 7.07, 7.19 (ABq, J = 7.9 Hz, 4H, ArH), 7.39
(s, 8H); 13C NMR (126 MHz, CDCl3) δ 15.6, 16.2, 28.6, 29.1, 42.1, 129.3, 129.5, 130.1, 136.5,
140.3, 143.3, 147.2, 148.0; FABMS m/z = 992.28 [M+]. Anal. Calcd for C48H64S8: C, 67.69; H,
6.49%. Found: C, 67.37; H, 6.48%; 4: 1H NMR (500 MHz, CDCl3) δ 0.99 (t, J = 7.5 Hz, 18H,
CH3), 1.09 (t, J = 7.5 Hz, 18H, CH3), 2.57 (q, J = 7.5 Hz, 12H, CH2), 2.79 (q, J = 7.5 Hz, 12H,
CH2), 3.81 (s, 12H, SCH2), 7.05 (s, 12H), 7.07, 7.12 (ABq, J = 8.0 Hz, 6H, ArH); 13C NMR
(126 MHz, CDCl3) δ 15.3, 15.9, 28.5, 28.8, 42.0, 129.0, 129.2, 130.1, 136.4, 140.0, 142.3, 147.4,
147.8; FABMS m/z = 1488.46 [M+].
4.11. Cyclization of 2d
15%; yellow oil; 1H NMR (400 MHz, CDCl3) δ 0.84 (t, J = 7.3 Hz, 12H, CH3), 1.24 (t, J = 7.3
Hz, 12H, CH3), 2.59 (q, J = 7.4 Hz, 8H, CH2), 3.13 (q, J = 7.3 Hz, 8H, CH2), 4.00 (s, 8H, SCH2),
7.38 (s, 8H, ArH).
4.12. Reaction of 3c with CF3COOAg
1
Compound 3c was reacted with CF3COOAg in the NMR tube by using CDCl3/acetone-d6; H
NMR (500 MHz, CDCl3/acetone-d6) δ 1.08 (brs, 12H, CH3), 1.24 (t, J = 7.1 Hz, 12H, CH3),
2.53 (brs, 8H, CH2), 2.96 (brs, 8H, CH2), 4.13 (br, 8H, SCH2), 6.99 (brs, 8H), 7.40, 7.52 (ABq,
J = 7.9 Hz, 4H, ArH).
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