Synthesis and structure of novel disulfide(trisulfide)-containing thiophenes

Article abstract of DOI:10.1080/00397910600978101

A novel trisulfide-containing thiophene, 1,5-dihydrothieno[3,4-e][1,2,3] trithiepine (5), and a disulfide analogue, 1,4-dihydrothieno[3,4-d][1,2]dithiine (4), were designed and synthesized. All the compounds were characterized by FT-IR, NMR, Raman, MS, an

Full text of DOI:10.1080/00397910600978101

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Synthesis and Structure of Novel
Disulfide(trisulfide)‐Containing Thiophenes
Shi‐Ren Deng a , Tao Wu b , Gao‐Qiang Hu a , Dan Li b , Yun‐Hong Zhou a &
Zao‐Ying Li a
a Department of Chemistry, Wuhan University, Wuhan, China
b Department of Chemistry, Shantou University, Shantou, China
Published online: 25 Jul 2007.
To cite this article: Shi‐Ren Deng , Tao Wu , Gao‐Qiang Hu , Dan Li , Yun‐Hong Zhou & Zao‐Ying Li (2007):
Synthesis and Structure of Novel Disulfide(trisulfide)‐Containing Thiophenes, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 37:1, 71-78
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Synthetic Communicationsw, 37: 71–78, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600978101
Synthesis and Structure of Novel
Disulfide(trisulfide)-Containing Thiophenes
Shi-Ren Deng
Department of Chemistry, Wuhan University, Wuhan, China
Tao Wu
Department of Chemistry, Shantou University, Shantou, China
Gao-Qiang Hu
Department of Chemistry, Wuhan University, Wuhan, China
Dan Li
Department of Chemistry, Shantou University, Shantou, China
Yun-Hong Zhou and Zao-Ying Li
Department of Chemistry, Wuhan University, Wuhan, China
Abstract: A novel trisulfide-containing thiophene, 1,5-dihydrothieno[3,4-e][1,2,3]-
trithiepine (5), and a disulfide analogue, 1,4-dihydrothieno[3,4-d][1,2]dithiine (4),
were designed and synthesized. All the compounds were characterized by FT-IR,
NMR, Raman, MS, and elemental analysis, some of which were confirmed by
single-crystal structure analysis. The designed molecules have potential usage as the
cathode material for batteries.
Keywords: alkylbromination, disulfide, methylation, thioesterification, thiophene,
trisulfide
Received in Japan April 9, 2006
Address correspondence to Zao-Ying Li, Department of Chemistry, Wuhan Univer-
sity, Wuhan 430072, China. E-mail: zyliwuc@whu.edu.cn
71

72
S-.R. Deng et al.
Organodisulfide compounds have been introducted as a new organic cathode
material in lithium batteries because of their high specific energy.[1] A series
of compounds[2,3] having S-S groups within the molecules are being
considered as energy storage materials, whereby energy exchange occurs
based on the reversible polymerization–depolymerization process
(2SH $ S-S). At the same time, polythiophene (PTh) and its derivatives[4]
have been investigated intensely because of their interesting electrical and
electronic properties and relatively good environmental stability, which
makes them good candidates for the cathode material of lithium secondary
batteries.[5] According to our previous studies and related references,[6–8]
when a six-membered cycle containing S-S bond was introduced as an
electrode material into the backbone of some kind of conducting polymer,
the compound was expected to have some excellent behaviors, such as
enhanced redox process and prolonged cyclic life.
For this article, we designed, synthesized, and characterized a new
trisulfide-containing thiophene derivative and a disulfide analogue, both
with a condensed aliphatic ring containing a trisulfide(disulfide) bond at the
3,4-position of thiophene ring. Its high disulfide density and intramolecular
S-S bonds can lead to high effectivity as a potential battery material.[6]
The total synthesis for target compounds 1,4-dihydrothieno[3,4-d]
[1,2]dithiine (4) and 1,5-dihydrothieno[3,4-e][1,2,3]trithiepine (5) is
achieved in three steps starting from 3,4-dibromo-thiophene (1) as outlined
in Scheme 1. First, the starting material 1 was converted to 3,4-dimethyl-
thiophene(2) in 88% yield, which was modified from Tamao’s Grignard
coupling reaction.[9] In contrast, we gave up on our attempt to methylate 1
by n-butyllithium, followed by dimethylsulfate.[10] Although its reaction
time was shorter than the Grignard’s, the reaction conditions was too
rigorous, especially its low temperature (2788C). When it slightly raised to
270 to 2608C, some complicated by-products, such as 2,3,4-trimethyl-
thiopene and 2,3,5-trimethyl-thiopene, would appear, which seriously lower
the product’s yield. These by-products can de determined by 1H NMR
analysis of the crude product.
Scheme 1. Synthesis of compound 4 and 5.

Disulfide(trisulfide)-Containing Thiophenes
73
The alkylate 2 was then brominated to 3,4-bis-bromomethyl-thiophene
(3) by N-bromosuccinimide (NBS) in the presence of BPO (benzoyl
peroxide) in 33% yield. This bromination reaction was only mentioned in
the literature,[11] without detailed description.
Finally, the bromide 3 was converted to target molecules 4 and 5. This
process was accomplished via two steps. First, an intermediate (sodium
alkylthiosulfate) was yielded by reaction of compound 3 and Na2S2O3, and
the intermediate was then directly converted to disulfide and trisulfide by
the oxidation of I2, without any purification. Sodium alkylthiosulfate[12–14]
(Bunte salts) has been reported as a generally used reagent to form a
disulfide compound by reaction with iodine or hydrogen peroxide. In this
case, we completed the reaction with iodine, but hydrogen peroxide did not
work. Furthermore, not only disulfide but also trisulfide was synthesized in
one pot, which has not been reported in the literature under similar reaction
circumstances.
Both of the target compounds were characterized by 1H NMR analysis. It
is noteworthy that the spectrum of disulfide 4 shows all four methylene
protons to be equivalent, by virtue of rapid conformational interchange. In
contrast, the four methylene protons of the larger trisulfide ring in the trithie-
pine (5) appeared as an AB quartet, indicating a higher degree of rigidity
of the conformational isomers. Its NMR signals were similar to other
trisulfide-containing molecules.[15]
Raman spectroscopy has always been a powerful research tool to charac-
terize sulfur-rich compounds, because they give very intense Raman spectra
because the valence electrons in S-S bonds are highly polarizable.[16] In this
work, the S-S stretching vibrations of compounds 4 and 5 in Raman spectra
were observed at 503 and 478 cm21 respectively.
We successfully grew single crystals of compounds 3, 4, and 5 from
CHCl3/C2H5OH and submitted them to X-ray crystallography. Their
single-crystal analysis data confirmed their molecular structures. The
ORTEP drawing of the three compounds are shown in Figs. 1–3,
respectively.
In conclusion, a three-step synthesis in 18% total yield of a novel
trisulfide-containing thiophene, 1,5-dihydrothieno[3,4-e][1,2,3]trithiepine
(5), and a disulfide analogue, 1,4-dihydrothieno[3,4-d][1,2]dithiine (4),
have been developed. During the synthesis of target compounds,
Grignard coupling reaction accomplished the methylation instead of
n-butyllithium and dimethylsulfate, to ensure the purity and conversion
yield. Furthermore, we synthesized trisulfide and disulfide compounds in
one pot through an intermediate (Bunte salts), which has not been
reported in relevant literature. The single-crystal structures of three
compounds, 3, 4, and 5, were reported. When the designed molecule is
polymerized, it has potential to be used as the cathode material of
secondary lithium batteries. The corresponding research work on polymer-
ization is under way.

74
S-.R. Deng et al.
Figure 1. ORTEP drawing of the molecular structure of 3, CCDC reference number
256418.
Figure 2. ORTEP drawing of the molecular structure of 4, CCDC reference number
267119.

Disulfide(trisulfide)-Containing Thiophenes
75
Figure 3. ORTEP drawing of the molecular structure of 5, CCDC reference number
264691.
EXPERIMENTAL SECTION
General
3,4-Dibromo-thiophene (1) was purified under reduced-pressure distillation;
N-bromosuccinimide (NBS) was recrystallized from H2O. Other commercially
available reagents were used without further purification, unless otherwise
noted. All solvents used for extractions or reactions were dried according
to standard procedures and kept over molecular sieves. Dichloro[1,3-
bis(diphenylpgosphino)propane]nickel[17] (Ni(dppp)Cl2) and methylmagne-
sium iodide[18] (MeMgI) were prepared according to literature procedures.
Melting points were taken on a micro-melting apparatus and are uncor-
rected. NMR spectra were obtained on Varian Mercury-VX 300 spec-
trometers. Spectra were recorded in CDCl3, using TMS as internal standard
1
at 300 MHz for H and 125 Hz for 13C at 298 K if not stated otherwise;
d values are given in parts per million (ppm), and coupling constants are
reported in Hertz. FT-IR spectra were recorded on a Shimadzu infrared spec-
trophotometer (values in centimeters21). Raman spectra were recorded on a
Nexus 670 spectrophotometer. Mass spectra were obtained on a Thermo
Finnigan Trace MS Plus. The elemental analyses were measured with a
Finnigan Flash 1112 Series EA. The crystal data were collected with a
Bruker AXS Smart 1000 CCD. Chromatographic separations were
performed using silica gel 60 (200–300 mesh).

76
S-.R. Deng et al.
3,4-Dimethyl-thiophene (2)
3,4-Dibromo-thiophene (1) (10.4 g, 43.0 mmol) and [(Ni(dppp)Cl2)] (0.15 g
0.3 mmol) was dissolved in 70 mL of dry ether then the above mixture was
dropped into a solution of methylmagnesium iodide (17.0 g, 102 mmol) in
70 mL of ether at 08C under an N2 atmosphere for 30 min. After the
addition, the mixture was refluxed for 20 h. The resulting mixture was
treated with 50 mL of HCl (2 N) in an ice bath to remove the excess
MeMgI, and the organic layer was then washed with H2O (2 ꢀ 70 mL) and
dried over MgSO4. Removal of the solvent gave a light yellow oil residue,
which was purified using silica-gel chromato-
graphy (petroleum ether) to give 4.2 g (88%) of 2 as a yellow odorous oil: bp
1
143–1448C (lit.[10] bp 1448C); H NMR (CDCl3) d 6.88 (s, 2H, a-H), 2.16
(s, 6H, Ar-CH3); FT-IR (neat) 3090 (nAr-H), 2922, 2860, 1444 (nC-H) cm21
.
3,4-bis-Bromomethyl-thiophene (3)[11]
The compound 2 (3.0 g, 26.7 mmol), N-bromosuccinimide (9.5 g, 53.4 mol),
and benzoyl peroxide (0.25 g, 1 mmol) were refluxed in 120 mL of CCl4 for
5 h. After the mixture was filtered, the succinimide was washed with CCl4
(2 ꢀ 10 mL). Then the organic solution was combined and concentrated
under reduced pressure. The red-brown oil thus obtained was crystallized
1
from CCl4 to give 2.4 g (33%) of white crystals: mp 83–84 8C; H NMR
(CDCl3) d 7.35 (s, 2H, s, 2H, a-H), 4.63 (s, 4H, Ar-CH2); FT-IR(KBr)
3091, 3028 (n Ar-H), 2924, 1422 (n C-H) cm21
.
1,4-Dihydrothieno[3,4-d][1,2]dithiine (4) and
1,5-Dihydrothieno[3,4-e][1,2,3]trithiepine (5)
The compound 3 (2.7 g, 10.0 mmol) and sodium thiosulphate (4.96 g,
20.0 mmol) were dissolved in 80 mL of EtOH/H2O (1 : 1). The mixture was
refluxed with stirring until the solution was homogeneous. The iodine was
then added in small portions until the color remained. Then a sodium
bisulfite solution was added to remove the excess iodine. After filtration,
the brown-black precipitation was extracted by 100 mL of boiling CHCl3;
then the organic solution was washed with water (2 ꢀ 50 mL) and dried
over MgSO4. Evaporation of the solvent left a yellow solid residue, which
was purified using silica-gel chromatography (petroleum ether/chloroform
10:3) to give 0.66 g (38%) of 4 and 0.50 g (24%) of 5.
Compound 4 was a white solid: mp 91–928C (lit.[19] 92–938C); 1H NMR
(CDCl3) d 7.03 (s, 2H, a-H), 4.05 (s, 4H, Ar-CH2); 13C NMR (CDCl3) d 132.1,
121.9, 33.4; FT-IR (KBr) 3077, 2897, 1363, 1229 cm21; Raman 503 (n
)
S-S

Disulfide(trisulfide)-Containing Thiophenes
77
cm21; MS(EI) 174[M]þ; anal. for C6H6S3 calcd.: C, 41.34; H, 3.47; S, 55.19,
Found: C, 41.56; H, 3.52; S, 54.92.
Compound 5 was a white solid: mp 105–1068C; 1H NMR (CDCl3) d 7.07
(s, 2H, a-H), 4.36 (AB pattern, Dd ¼ 0.12 ppm, J ¼ 15 Hz, 4H, Ar-CH2);
13C NMR (CDCl3) d 141.0, 125.3, 44.3; FT-IR (KBr) 3074, 2924, 1399,
1226 cm21; Raman 478(nS-S) cm21; MS(EI) 206[M]þ; anal. for C6H6S4
calcd: C, 34.92; H, 2.93; S, 62.15. Found: C, 34.98; H, 3.02; S, 62.04.
X-Ray Crystallographic Data
The crystal structures of compounds 3, 4, and 5 were determined, using data
collected at 293 K with Mo Ka radiation on a Bruker AXS CCD diffract-
ometer. The structures were solved by direct methods (SHELXS-97) and
refined using full-matrix least-squares on F2.
Complete crystallographic data (excluding structure factors) have been
deposited at the Cambridge Crystallographic Data Centre under the
reference numbers CCDC 256418, CCDC 267119, and CCDC 264691.
Copies of the data can be obtained, free of charge, on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK (fax: þ44-1223-336033 or
e-mail: deposit@ccdc.cam.ac.uk).
ACKNOWLEDGMENT
We gratefully acknowledge financial support from the National Natural
Science Foundation of China (No. 29833090).
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