One-pot Metal-free Synthesis of Benzyl Alkyl Sulfides

Article abstract of DOI:10.1080/10426507.2014.919295

The synthesis of sulfides is important in various fields. This paper reports an efficient, odorless, and viable protocol for the base-mediated synthesis of benzyl alkyl sulfides using thiourea. The reactions were carried out under transition-metal-free co

Full text of DOI:10.1080/10426507.2014.919295

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Phosphorus, Sulfur, and Silicon and the
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One-Pot Metal-Free Synthesis of Benzyl
Alkyl Sulfides
Xiaogang Lua, Hongmei Wanga, Runli Gaoa & Chengxin Peia
a State Key Laboratory of NBC Protection for Civilian, Beijing
102205, China
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To cite this article: Xiaogang Lu, Hongmei Wang, Runli Gao & Chengxin Pei (2014): One-Pot Metal-
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Phosphorus, Sulfur, and Silicon, 190:1–8, 2015
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2014.919295
ONE-POT METAL-FREE SYNTHESIS OF BENZYL
ALKYL SULFIDES
Xiaogang Lu, Hongmei Wang, Runli Gao, and Chengxin Pei
State Key Laboratory of NBC Protection for Civilian, Beijing 102205, China
GRAPHICAL ABSTRACT
Abstract The synthesis of sulfides is important in various fields. This paper reports an
efficient, odorless, and viable protocol for the base-mediated synthesis of benzyl alkyl sul-
fides using thiourea. The reactions were carried out under transition-metal-free conditions,
showing yields of asymmetric sulfides higher than 80%. Tertiary alkyl halides and aryl halides
do not react with thiourea under formation of the corresponding isothiouronium salts; however,
5-bromopyrimidine and 2-bromopyrimidine lead to yields of 79.2% and 87.6%, respectively.
This method is of significant importance from the both environmental and economic, green
chemistry points of view.
Keywords Asymmetric sulfides; thiourea; metal-free reaction
INTRODUCTION
There are a great number of natural and synthetic sulfur-containing compounds,
some of which play a crucial role in the synthesis of drugs such as penicillin, sulfon-
amides, cephalosporins, and vitamin B1. Moreover, sulfides are useful in many other fields
including in pesticides, dyes, organic optoelectronic materials, synthase inhibitors, and
herbicides.1–5
The formation of C S bonds is very important in the synthesis of thioethers that
are of biological, pharmaceutical, and material science interest. During the past few
decades, the generation of C S bonds, especially Caryl S bonds involving an SNAr
reaction,6 the coupling reaction,7 and electrophilic substitution reaction of activated aryl
halides and thiols8 has received considerable attention. Among them, catalysts based
on transition metals are widely used in the formation of Caryl S bonds by directly
coupling aryl halides with thiols. Pd,9 Ni,10,11 Cu,12,13 and Fe14,15 have been successfully
applied to the synthesis of aryl sulfides. However, there still exist some challenges
in these reactions. For example, the use of highly volatile, environmentally
harmful, and foul-smelling thiols is not desirable, especially in large-scale production
Received 24 March 2014; accepted 23 April 2014.
Address correspondence to Hongmei Wang, State Key Laboratory of NBC Protection for Civilian, Beijing
102205, China. E-mail: hmwang2@163.com; wang.hm401@gmail.com
1

2
X. LU ET AL.
processes. It becomes more and more unacceptable with respect to increasing environ-
mental problems. Therefore, it is necessary to develop robust, simple, and sustainable
procedures.
It is known that thiourea is an attractive starting material due to its low cost and
ease of availability. Recently, it has been found that thiols can be replaced by thiourea,
which is odorless and non-toxic, as a sulfur source for the formation of C S bonds.16,17
Although these pioneering studies provided highly promising strategies for the prepa-
ration of thioethers, the development of more efficient, environmentally benign, and
simple processes that are viable to diverse products such as asymmetric thioethers remains
challenging.
Herein, we report a novel and efficient route for the synthesis of asymmetric sulfides.
The direct sulfonation of (bromomethyl)benzene with thiourea and a series of alkyl halides
in DMF at 100◦C yields asymmetric thioethers.
RESULTS AND DISCUSSION
(Bromomethyl)benzene, 1-bromohexane, and thiourea were selected as a model
system to optimize the reaction conditions, the results of which are summarized in
Table 1. First, we investigated the effect of solvents and bases. DMF is found to be
considerably superior to DMSO, THF, EtOH, acetone, and acetonitrile (Table 1, En-
tries 1–7). The results also indicate that the nature of the base has a pronounced im-
pact on the reaction. Potassium carbonate leads to a better yield than cesium carbonate,
potassium hydroxide, potassium ortho-phosphate, calcium oxide, and sodium carbonate
(Table 1, Entries 2, 6, 10–13). Potassium hydroxide in DMSO forms a superbasic medium
that allows cross-coupling reactions between aryl halides with various sulfur-, oxygen-,
and nitrogen-based nucleophiles under transition metal-free conditions.18 We conducted
a similar reaction (Table 1, Entry 2); however, only a 74% yield was obtained. The
reaction temperature also plays an important role in the reaction. The coupling pro-
ceeds slowly at 40◦C, yielding only a little product even after 8 h (Table 1, Entry 7);
however, the yield increased when the temperature was increased to 100◦C, (Table 1,
Entry 13).
Furthermore, copper(I) iodide, copper(I) chloride, iron(III) chloride, and Pd(PPh3)3
were used as ligands to catalyze the reaction (Table 1, Entries 14–27). The results reveal that
the yields decrease compared to the use of potassium carbonate alone. Therefore, the optimal
conditions can be concluded as follows: thiourea (1.2 equiv.), (bromomethyl)benzene (1.0
equiv.), and alkyl bromide (1.1 equiv.), potassium carbonate as the base without any metal
catalysts. The best solvent is DMF; the optimum reaction temperature is 100◦C; and the
ideal reaction time is 8 h.
To investigate the generality and scope of the proposed protocol, reactions using a
series of organic halides were explored. As summarized in Table 2, we found that alkyl
halides can be easily transformed into their corresponding thioethers with yields higher than
80% at 100◦C. The short-chain primary alkyl halides are more reactive substrates compared
with those containing long chains because the reaction of primary alkyl halides with thiourea
undergoes a mechanism of bimolecular nucleophilic substitution (SN2) in which less steric
hindrance results in higher reaction rates. High yields were also obtained when secondary
alkyl halides including bromocyclopentane and bromocyclohexane were used as the reac-
tants (Table 2, Entries 5–11). However, tertiary alkyl halides and aryl halides do not react

METAL-FREE SYNTHESIS OF BENZYL ALKYL SULFIDES
of the reaction conditions for the synthesis
3
Table 1 Optimization
of
asymmetric
thioethersa
Entry
Catalyst
Ligand
Base
Solvent
Reaction temperature/◦C
Yieldb(%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
K2CO3
KOH
EtOH
DMSO
Acetone
THF
Acetonitrile
DMF
50
80
45
45
50
80
40
60
80
100
100
100
100
50
50
50
50
100
100
100
100
100
100
100
100
100
100
78
74
36
0.4
0.25
49
27
74
82
50
88
87
95
53
62
88
81
90
82
85
73
74
81
77
62
14
62
K2CO3
K2CO3
K2CO3
Cs2CO3
K2CO3
K2CO3
K2CO3
K3PO4
CaO
Na2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
DMF
DMF
DMF
DMF
DMF
DMF
DMF
EtOH
EtOH
EtOH
EtOH
DMF
DMF
DMF
DMF
DMF
CuI
CuCl
Pd(PPh3)3
FeCl3
FeCl3
L1
L1
L2
L2
L3
L4
L2
L3
CuI
CuI
CuI
DMF
DMF
DMF
DMF
FeCl3
FeCl3
FeCl3
DMEDA
TMEDA
DMF
aGeneral reaction conditions: (bromomethyl)benzene (1.0 mmol), thiourea (1.2 mmol), 1-bromohexane
(1.1 mmol), catalyst (0.1 mmol), ligand (0.1 mmol), and 3 equiv. base in solvent (5 mL) for 8 h. bGC
yield.
with thiourea to produce isothiouronium salts, because of steric hindrance and electronic
effects, respectively (Table 2, Entries 12 and 16). Interestingly, 5-bromopyrimidine and
2-bromopyrimidine lead to much better yields of 79.2% and 87.6%,respectively (Table 2,
Entries 13 and 14).

4
X. LU ET AL.
Table 2 Reactions of benzyl bromide with thioureas and alkyl halides Under Optimized Condi-
tionsa
Entry
1
Halide
Product Formula
Product No
Yieldb (%)
87.6
n-C12H25Br
4a
2
3
n-C8H17Br
4b
4c
87.1
92.3
4
5
4d
4e
96.2
88.1
6
7
4f
95.4
85.3
4g
8
9
4h
4i
80.6
91.8
(Continued on next page)

METAL-FREE SYNTHESIS OF BENZYL ALKYL SULFIDES
5
Table 2 Reactions of benzyl bromide with thioureas and alkyl halides under optimized conditionsa (continued)
Entry
10
Halide
Product Formula
Product No
Yieldb (%)
88.4
4j
11
12
4k
4l
89.8
0
13
14
15
16
4m
4n
4o
87.6
79.2
85.6
0
4p
aGeneral reaction conditions: (Bromomethyl)benzene (1.0 mmol), thiourea (1.2 mmol), alkyl bromide
(1.1 mmol), and 3 equiv. K2CO3 in DMF at 100◦C for 8 h.bIsolated yield.
We propose a general pathway for the reaction, which is shown in Scheme 1. The
simultaneous reaction of thiourea with a mixture of two different alkylating agents selec-
tively yields asymmetric thioethers as the main products. This may be explained by the
fact that, by far, the most reactive halide benzyl bromide reacts with thiourea first and,
in the following step, the less reactive halide leads to the formation of the benzyl alkyl
thioether.

6
X. LU ET AL.
Scheme 1
CONCLUSION
In conclusion, we have identified an efficient, odorless, and viable protocol for the
one-pot metal-free synthesis of benzyl alkyl thioethers. The most reactive halide benzyl
bromide reacts with thiourea first and, in the following step, the less reactive halide leads to
the formation of the benzyl alkyl thioether. The optimal conditions are as follows: thiourea
(1.2 equiv.), (bromomethyl)benzene (1.0 equiv.), and the alkyl bromide (1.1 equiv.) are
dissolved in DMF, potassium carbonate is added as the base and the reaction is run at
100◦C for 8 h. Under optimal conditions, yields of asymmetric thioethers higher than 80%
have been achieved.
EXPERIMENTAL
Materials and Methods
1H and 13C NMR spectra were recorded on a Bruker Advance III spectrometer at
400 MHz (1H) and 100 MHz (13C) in CD3OD using TMS as the internal standard. Chemical
shifts δ are reported in ppm, coupling constants J in Hertz. GC/MS Analyses were performed
on a Polaris Q GC/MS instrument. All products are compounds that have been reported
in the literature and were identified by comparing their spectra with those reported. All
chemicals were commercially available and used without further purification.
Typical Procedure for the Reaction of Benzyl Bromide with Alkyl
Halides and Thiourea
Benzyl bromide (1 mmol), alkyl halide (1.1 mmol), thiourea (1.2 mmol), and K2CO3
(3 mmol) were added to 5 mL of DMF at 100◦C. The reaction was stopped after the con-
sumption of the benzyl bromide, which was monitored by gas chromatography (GC). Then,

METAL-FREE SYNTHESIS OF BENZYL ALKYL SULFIDES
7
the reaction mixture was diluted with de-ionized water and extracted with CH2Cl2. The
combined organic extracts were dried over anhydrous MgSO4, filtered, and concentrated by
rotary evaporation to generate a crude product. Purification by silica gel chromatography
eluting with n-hexane afforded pure thioethers.
Characteristic Data of Compounds
Benzyl(dodecyl)sulfane (4a). Colorless oil. 256 mg (0.876 mmol, 87.6% yield). 1H
NMR: δ 7.32–7.17 (m, 5H), 3.69 (s, 2H), 2.38 (t, J = 7.3 Hz, 2H), 1.56–1.47 (m, 2H), 1.28
(m, 18H), 0.90 (t, J = 6.8 Hz, 3H); 13C NMR: δ 140.27, 129.94, 129.35, 127.80, 36.93,
33.09, 32.11, 30.78, 30.72, 30.64, 30.50, 30.32, 30.28, 29.86, 23.76, 14.48; HRMS (EI)
calcd. for [C19H32S + H]+ requires m/z 292.2225, found 291.7474.
1
Benzyl(octyl)sulfane (4b). Colorless oil. 206 mg (0.871 mmol, 87.1% yield). H
NMR: δ 7.78–6.87 (m, 5H), 3.69 (s, 2H), 2.41–2.36 (t, J = 7.3 Hz, 2H), 1.58–1.48 (m, 2H),
1.28 (s, 10H), 0.91 (t, J = 6.9 Hz, 3H); 13C NMR: δ 138.85, 128.59, 128.00, 126.45, 35.65,
31.66, 30.82, 29.01, 28.95, 28.56, 24.43, 22.39, 13.20; HRMS (EI) calcd. for [C15H24S +
H]+ requires m/z 236.1599, found 235.9009.
1
Benzyl(hexyl)sulfane (4c). Colorless oil. 190 mg (0.923 mmol, 92.3% yield). H
NMR: δ 7.31–7.16 (m, 5H), 3.66 (s, 1H), 2.40–2.32 (t, J = 7.3 Hz, 2H), 1.55–1.46 (m,
2H), 1.36–1.17 (m, 6H), 0.88 (t, J = 7.0 Hz, 3H); 13C NMR: δ 140.13, 129.89, 129.31,
127.75, 36.95, 32.52, 32.13, 30.27, 29.54, 23.59, 14.46; HRMS (EI) calcd. for [C13H20S +
H]+ requires m/z 208.1286, found 207.8443.
1
Benzyl(pentyl)sulfane (4d). Colorless oil. 187 mg (0.964 mmol, 96.4% yield). H
NMR: δ 7.32–7.15 (m, 5H), 3.67 (s, 2H), 2.36 (t, J = 7.4 Hz, 2H), 1.57–1.46 (m, 2H),
1.35–1.22 (m, 4H), 0.87 (t, J = 7.1 Hz, 3H); 13C NMR: δ 140.15, 129.89, 129.31, 127.76,
36.93, 32.09, 30.00, 23.28, 14.38; HRMS (EI) calcd. for [C12H18S + H]+ requires m/z
194.1129, found 193.9804.
Benzyl(isopentyl)sulfane (4e). Colorless oil. 171 mg (0.881 mmol, 88.1% yield). 1H
NMR: δ 7.32–7.15 (m, 5H), 3.67 (s, 2H), 2.40–2.34 (m, 2H), 1.60 (dq, J = 13.3, 6.7 Hz,
1H), 1.40 (m, 2H), 0.84 (d, J = 6.6 Hz, 6H); 13C NMR: δ 140.12, 129.91, 129.30, 127.76,
39.39, 36.89, 30.07, 28.43, 22.68; HRMS (EI) calcd. for [C12H18S + H]+requires m/z
194.1129, found 194.1001.
Benzyl(isobutyl)sulfane (4f). Colorless oil. 172 mg (0.954 mmol, 95.4% yield). 1H
NMR: δ 7.32–7.16 (m, 5H), 3.67 (s, 2H), 2.27 (d, J = 6.8 Hz, 2H), 1.73 (m, 1H), 0.93 (d,
J = 6.7 Hz, 6H); 13C NMR: δ 140.22, 129.95, 129.32, 127.79, 41.33, 37.36, 29.32, 22.35;
HRMS (EI) calcd. for [C11H16S + H]+ requires m/z 180.0973, found 179.9579.
Benzyl(sec-butyl)sulfane (4g). Colorless oil. 154 mg (0.853 mmol, 85.3% yield). 1H
NMR: δ 7.25 (m, 5H), 3.71 (s, 1H), 2.55 (m, 1H), 1.60–1.43 (m, 2H), 1.21 (d, J = 6.8 Hz,
3H), 0.92 (t, J = 7.4 Hz, 3H); 13C NMR: δ 140.32, 129.87, 129.32, 127.72, 42.10, 35.63,
30.51, 21.06, 11.61; HRMS (EI) calcd. for [C11H16S + H]+ requires m/z 180.0973, found
179.9659.
Benzyl(cyclohexyl)sulfane (4h, 4i). Colorless oil. 166 mg (0.806 mmol, 80.6%
1
yield), 189 mg (0.918mmol, 91.8% yield). H NMR: δ 7.30–7.15 (m,5H), 3.65 (s, 1H),
2.37–2.33 (m, 1H), 1.54–1.45 (m, 2H), 1.35–1.19 (m, 6H), 0.87 (t, J = 7.0 Hz, 2H); 13C
NMR: δ 140.09, 129.88, 129.29, 127.74, 36.96, 32.51, 32.14, 30.26, 29.54, 23.58, 14.49;
HRMS (EI) calcd. for [C13H18S + H]+ requires m/z 206.1129, found 207.8443.
Benzyl(cyclopentyl)sulfane (4j). Colorless oil. 170 mg (0.884 mmol, 88.4% yield).
1H NMR: δ 7.34–7.16 (m, 5H), 3.72 (s, 1H), 2.94 (p, J = 6.8 Hz, 1H), 1.99–1.85 (m,
2H), 1.74–1.67 (m, 2H), 1.59–1.42 (m, 4H); 13C NMR: δ 140.39, 130.51, 129.86, 129.33,

8
X. LU ET AL.
127.72, 44.24, 37.12, 34.52, 25.74; HRMS (EI) calcd. for [C12H16S + H]+ requires m/z
192.0973, found 191.9162.
Benzyl(cyclohexylmethyl)sulfane (4k). Colorless oil. 198 mg (0.898 mmol, 89.8%
yield). 1H NMR: δ 7.31–7.16 (m, 5H), 3.66 (s, 1H), 2.27 (d, J = 6.8 Hz, 2H), 1.79 (m, 2H),
1.69 (m, 3H), 1.44–1.33 (m, 1H), 1.28–1.08 (m, 3H), 0.88 (m, 2H); 13C NMR: δ 140.28,
129.96, 129.32, 127.78, 39.79, 38.81, 37.51, 33.89, 27.51, 27.21; HRMS (EI) calcd. for
[C14H20S + H]+ requires m/z 220.1286, found 219.8657.
2-(Benzylthio)pyrimidine (4m). Colorless oil. 177 mg (0.876 mmol, 87.6% yield).
1H NMR: δ 8.46 (d, J = 4.9 Hz, 2H), 7.37 (d, J = 7.2 Hz,2H), 7.26–7.13 (m, 3H), 6.98
(t, J = 4.9 Hz, 1H), 4.37 (s, 1H); 13C NMR: δ 172.81, 158.49, 138.82, 129.97, 129.39,
128.13, 117.98, 35.86; HRMS (EI) calcd. for [C11H10N2S+ H]+ requires m/z 202.0565,
found 201.9377.
1
5-(Benzylthio)pyrimidine (4n). Yellow oil. 87 mg (0.43 mmol, 79.2% yield). H
NMR: δ 8.92 (s, 1H), 8.60 (s, 2H), 7.29–7.17 (m, 5H), 4.19 (s, 1H); 13C NMR: δ 159.10,
156.80, 137.85, 130.05, 129.64, 128.61, 38.94; HRMS (EI) calcd. for [C11H10N2S+ H]+
requires m/z 202.0565, found 201.8482.
(E)-Benzyl(styryl)sulfane (4o). White solid. 193 mg (0.856 mmol, 85.6% yield). 1H
NMR: δ 7.45–7.11 (m, 10H), 6.83 (d, J = 15.6 Hz, 0.5H), 6.48 (d, J = 15.6 Hz, 0.5H),
6.38 (d, J = 11.0 Hz, 0.5H), 6.31 (d, J = 11.0 Hz, 0.5H), 4.01 (d, J = 8.3 Hz, 2H).(E:Z
= 1:1); 13C NMR: δ 139.37, 139.11, 138.51, 138.48, 130.03, 129.96, 129.68, 129.61,
129.55, 129.40, 129.12, 128.59, 128.26, 128.19, 127.86, 127.55, 127.51, 126.53, 126.37,
125.87, 40.09, 37.84; HRMS (EI) calcd. for [C15H14S + H]+ requires m/z 226.0816, found
225.8458.
REFERENCES
1. Shang, J.; Wang, W. M.; Li, Y. H.; Song, H. B.; Li, Z. M.; Wang, J. G. J. Agricul. Food Chem.
2012, 60, 8286-8293.
´
2. Banach, A.; Scianowski, J.; Ozimek, P. Phosphorus, Sulfur, Silicon Relat. Elem. 2013, 189,
274-284.
3. Mokhtary, M.; Lakouraj, M. M.; Niaki, M. R. Phosphorus, Sulfur, Silicon Relat. Elem. 2012,
187, 321-326.
4. Youssef, M. S. K.; Ahmed, R. A. Phosphorus, Sulfur, Silicon Relat. Elem. 2006, 181, 1123-1199.
5. Wan, L. S.; Li, J. W.; Ke, B. B.; Xu, Z. K. J. Am. Chem. Soc. 2012, 134, 95-98.
6. Campbell, J. R. J. Org. Chem. 1964, 29, 1830-1833.
7. Van Bierbeek, A.; Gingras, M. Tetrahedron Lett. 1998, 39, 6283-6286.
8. Ham, J.; Yang, I.; Kang, H. J. Org. Chem. 2004, 69, 3236-3239.
9. Ferna´ndez-Rodr´ıguez, M. A.; Hartwig, J. F. Chem. Eur. J. 2010, 16, 2355-2359.
10. Cristau, H. J.; Chabaud, B.; Chene, A.; Christol, H. Synthesis 1981, 1981, 892-894.
11. Xu, X. B.; Liu, J.; Zhang, J. J.; Wang, Y. W.; Peng, Y. Org. Lett. 2013, 15, 550-553.
12. Suzuki, H.; Abe, H.; Osuka, A. Chem. Lett. 1980, 1363-1364.
13. Ma, D.; Geng, Q.; Zhang, H.; Jiang, Y. Angew. Chem. Int. Ed. 2010, 49, 1291-1294.
14. Correa, A.; Carril, M.; Bolm, C. Angew. Chem. Int. Ed. 2008, 47, 2880-2883.
15. Wu, J. R.; Lin, C. H.; Lee, C. F. Chem. Commun. 2009, 4450-4452.
16. Firouzabadi, H.; Iranpoor, N.; Gholinejad, M. Adv. Synth. Catal. 2010, 352, 119-124.
17. Firouzabadi, H.; Iranpoor, N.; Gholinejad, M.; Samadi, A. J. Mol. Catal. A: Chem. 2013, 377,
190-196.
18. Yuan, Y.; Thome, I.; Kim, S. H.; Chen, D.; Beyer, A.; Bonnamour, J.; Zuidema, E.; Chang, S.;
Bolm, C. Adv. Synth. Catal. 2010, 352, 2892-2898.