Metal–organic framework MOF-199-catalyzed direct and one-pot synthesis of thiols, sulfides and disulfides from aryl halides in wet polyethylene glycols (PEG 400)

Article abstract of DOI:10.1080/17415993.2017.1329427

A highly porous metal–organic frame work Cu₃ BTC₂ (copper(II)-benzene-1,3,5-tricarboxylate) that is known as MOF-199 was synthesized from the reaction of 1,3,5-benzenetricarboxylic acid and Cu(OAc)₂·H₂O by a solvothermal method and characterized by several techniques including FT-IR, XRD, EDX and scanning electron microscopy. The MOF-199 used as an efficient catalyst for one-pot synthesis of thiols by domino reactions of aryl halides and thiourea, and subsequently conversion to aryl alkyl sulfides and diaryl disulfides in polyethylene glycols (PEGs). A variety of aryl alkyl sulfides can be obtained in good to excellent yields in a relatively short reaction time and in the presence of the trace amount of catalyst. Also, the catalyst can be separated from the reaction mixture by decanting, and be reused without significant degradation in catalytic activity.

Full text of DOI:10.1080/17415993.2017.1329427

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
Metal–organic framework MOF-199-catalyzed
direct and one-pot synthesis of thiols, sulfides and
disulfides from aryl halides in wet polyethylene
glycols (PEG 400)
Mohammad Soleiman-Beigi, Fatemeh Sadeghizadeh & Ali Basereh
To cite this article: Mohammad Soleiman-Beigi, Fatemeh Sadeghizadeh & Ali Basereh (2017):
Metal–organic framework MOF-199-catalyzed direct and one-pot synthesis of thiols, sulfides and
disulfides from aryl halides in wet polyethylene glycols (PEG 400), Journal of Sulfur Chemistry,
DOI: 10.1080/17415993.2017.1329427
To link to this article: http://dx.doi.org/10.1080/17415993.2017.1329427
Published online: 29 May 2017.
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Date: 31 May 2017, At: 23:09

JOURNAL OF SULFUR CHEMISTRY, 2017
https://doi.org/10.1080/17415993.2017.1329427
Metal–organic framework MOF-199-catalyzed direct and
one-pot synthesis of thiols, sulfides and disulfides from aryl
halides in wet polyethylene glycols (PEG 400)
Mohammad Soleiman-Beigi, Fatemeh Sadeghizadeh and Ali Basereh
Department of Chemistry, Ilam University, Ilam, Iran
ABSTRACT
ARTICLE HISTORY
Received 24 November 2016
Accepted 6 May 2017
A highly porous metal–organic frame work Cu3 BTC2 (copper(II)-
benzene-1,3,5-tricarboxylate) that is known as MOF-199 was syn-
thesized from the reaction of 1,3,5-benzenetricarboxylic acid and
Cu(OAc)2·H2O by a solvothermal method and characterized by sev-
eral techniques including FT-IR, XRD, EDX and scanning electron
microscopy. The MOF-199 used as an efficient catalyst for one-pot
synthesis of thiols by domino reactions of aryl halides and thiourea,
and subsequently conversion to aryl alkyl sulfides and diaryl disul-
fides in polyethylene glycols (PEGs). A variety of aryl alkyl sulfides
can be obtained in good to excellent yields in a relatively short
reaction time and in the presence of the trace amount of catalyst.
Also, the catalyst can be separated from the reaction mixture by
decanting, and be reused without significant degradation in catalytic
activity.
KEYWORDS
Metal–organic framework;
1,3,5-benzenetricarboxylic
acid; Cu(OAc)2·H2O; aryl alkyl
sulfides; polyethylene glycols
Introduction
Organosulfurs are important compounds that exist widely in many biologically and phar-
maceutically active molecules [1,2]. Especially, aryl alkyl thioether moieties have been used
in the treatment of diseases such as Parkinson’s, Alzheimer’s, immune and inflammatory,
diabetes, and HIV [3,4].
The formation of carbon–sulfur bonds have been widely examined and generally
transition-metal-catalyzed coupling have been used for its formation [5–7]. For the first
time, Migita et al. [8] reported carbon–sulfur bond formation by reaction between thiol
and aryl halide in the presence of Pd (PPh3)4 as a catalyst. In recent years palladium, nickel,
CONTACT Mohammad Soleiman-Beigi
soleimanbeigi@yahoo.com
Department of Chemistry, Ilam University,
PO Box 69315-516, Ilam, Iran
Supplemental data for this article can be accessed here. https://doi.org/10.1080/17415993.2017.1329427
© 2017 Informa UK Limited, trading as Taylor & Francis Group

2
M. SOLEIMAN-BEIGI ET AL.
cobalt, copper and iron salts have been used as catalysts for carbon–sulfur bond formation
[9–13]. However, due to some disadvantages such as the use of specially designed ligands,
high-temperature, high amount of metal catalyst and harmful organic solvents, a search to
find better catalysts has been undertaken [14].
Recently, for the sustainable development of any catalytic process, heterogeneous cat-
alysts have been highly employed for chemical transformations because of their ease of
recovery, recycling that decreases undesired toxic wastes, and E-factor [15].
The direct use of volatile thiols is a common synthetic method for synthesis of
organosulfur compounds [16]. However, the use of toxic, odorous and volatile thiols is con-
sidered a disadvantage of this method. To overcome these difficulties, attention has been
directed toward the synthesis of organosulfur compounds using sulfur-transfer reagents
instead of thiols [17–19]. Among these reagents, thiourea is used as an inexpensive, non-
toxic, odorless, commercial available and eco-friendly in situ S-source to produce aryl
(alkyl) thiolate in synthetic reactions [20–22].
In continuation of our efforts on the synthesis of organosulfur compounds [23–27], we
wish to report the utilization of an efficient heterogeneous copper-based catalyst without
the assistance of any ligands for the synthesis of aryl alkyl sulfides.
During the last decade, metal–organic frameworks (MOFs) have been widely investi-
gated as exquisite materials due to their potential applications in several fields [28–31].
Because of the presence of both organic and inorganic parts in these porous mate-
rials, MOFs show several benefits such as high surface areas, tuneable pore sizes,
processing facility, flexibility and structural diversity [32–35]. In catalysis processes,
MOFs have been used as solid catalysts or catalyst support for wide ranges of organic
transformations [36]. Specifically, microporous Cu3BTC2 (copper (II)-benzene-1,3,5-
tricarboxylate) is a copper-based MOF that was first reported in 1999 by Williams
and co-workers [37] and also named as HKUST-1. Furthermore, the MOF described
herein, namely MOF-199, has been employed widely as heterogeneous catalyst for
Friedel–Crafts alkylation and acylation, oxidation, alkene epoxidation, hydrogenation,
Suzuki cross-coupling, Knoevenagel condensation, aldol condensation and aza-Michael
condensation [38–44].
In this paper, we report, for the first time, the application of a recoverable and reusable
nanoporous metal–organic framework (MOF-199) as an efficient heterogeneous catalyst
for the synthesis of aryl alkyl sulfides without the need for addition of external ligand
other than the effect imparted by PEG (400) as a green solvent and eco-friendly media.
High yields were obtained and the MOF-199 catalyst was easily isolated from the reac-
tion mixture by simple filtration and reused without significant degradation in activity
(Scheme 1).
Scheme 1. The synthesis of sulfides, thiols and disulfides.

JOURNAL OF SULFUR CHEMISTRY
3
Results and discussion
To start to optimize the reaction conditions such as amount of catalyst, temperature,
type and amount of base and type of solvent, initially, the reaction between iodobenzene,
thiourea and benzyl chloride in the presence MOF-199 as a catalyst, KOH as a base in wet
PEG (400) at 130°C under an inert atmosphere was studied as a model reaction for the
synthesis of unsymmetrical sulfides (Scheme 2).
The reaction was carried out in two steps: in the first step, potassium benzene thio-
late was generated and synthesized by a domino reaction of phenyl iodide (1 mmol) with
thiourea (3 mmol) in the presence of 4 mg of MOF-199 and 3 mmol of KOH at 130°C under
an N2 atmosphere. In the second step, benzyl chloride (1.1 mmol) was added into the reac-
tion mixture for the synthesis of benzyl phenyl sulfides. (Scheme 2, Table 1). According
to the results shown in Table 1, by employing 3 mg of catalyst, a conversion of 61% was
achieved after 13.5 h for both steps. When the amount of MOF was increased to 4 mg, the
yield of product (benzyl phenyl sulfide) increased to 96% after 4.5 h for both steps (Table 1,
entries 2–4). Then, in studies that screened the effect of solvent on the progress of reaction,
wet PEG (400) was found most effective than other examined solvents including dimethyl
formamide (DMF), toluene, ethanol and water (Table 1, Entries 3, 5–8).
Temperature effects on the rate of reaction were studied. The reaction was carried out at
100°C, 115°C and 130°C, respectively. It was found the increase in temperature up to 130°C
led to an increased yield and rate of the reaction (Table 2, entries 1–4). Also, influence of the
base identity and amount on the progress of reaction was examined. KOH with 3 mmol was
found to impart a strong effect on the reaction yields (Table 2, entries 5–10). Furthermore,
the reaction did not proceed in the absence of a base.
After the optimized reaction conditions were established, a variety of aryl and alkyl
halides were examined to explore the scope of this reaction. It can be seen from Table 3 that
both bromo and iodo aryl halides could be transformed into corresponding product quite
efficiently. Iodo aryl compounds are similarly effective and produced desired products
under the optimized reaction conditions (Table 3). Interestingly, good yields were observed
Scheme 2. Reaction for optimization of condition of reaction.
Table 1. Optimization of the reaction conditions.a
Entry
Solvent
Amount of MOF-199 (mg)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
PEG
PEG
PEG
PEG
DMF
Toluene
Ethanol
Water
–
3
4
5
4
4
4
4
24
13.5
4.5
4.5
16
24
24
24
N. R
61
96
96
75
30
Trace
Trace
aReaction conditions: PhI (1.0 mmol), thiourea (3 mmol), KOH (3 mmol), benzyl chloride (1.1 mmol), at 130°C under N2.

4
M. SOLEIMAN-BEIGI ET AL.
Table 2. Optimization of the type and amount base and temperature.a
Entry
Temp. (°C)
Amount of base (mmol)
Time (h) both step
Yield (%)
1
2
3
4
5
6
7
8
9
25
80
KOH (3)
KOH (3)
KOH (3)
KOH (3)
–
KOH (1)
KOH (2)
KOH (4)
KF/Al2O3 (3)
K2CO3(3)
24
24
24
4.5
24
24
4.5
4.5
24
24
Trace
56
75
115
130
130
130
130
130
130
130
96
N. R.b
Trace
56
95
66
53
10
aReactionconditions: PhI (1.0 mmol), thiourea(3 mmol), MOF (4 mg), benzylchloride(1.1 mmol), in2 mlPEG/H2O(20:1)and
under N2.
bNo reaction.
Table 3. MOF-199 catalyzed; the direct synthesis of unsymmetrical sulfides from aryl halides and alkyl
halides.
Entry
ArX
RX
Product
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
PhI
PhI
PhI
PhI
PhI
PhCH2Cl
Ph(CH2)2Br
Ph(CH2)3Br
CH3(CH2)2Br
CH3(CH2)7Br
PhCH2Cl
Ph(CH2)2Br
Ph(CH2)3Br
PhCH2Cl
Ph(CH2)2Br
Ph(CH2)3Br
PhCH2Cl
Ph(CH2)2Br
Ph(CH2)3Br
PhCH2Cl
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
5l
5m
5n
5o
5p
5q
1.5
3
2
4
4
1.5
3
4
4
5
96
84
80
90
87
90
85
80
86
82
77
91
84
80
93
84
73
2-MePh-I
2-MePh-I
2-MePh-I
4-MePh-I
4-MePh-I
4-MePh-I
4-CF3Ph-Br
4-CF3Ph-Br
4-CF3Ph-Br
1-Naphthyl-I
1-Naphthyl-I
1-Naphthyl-I
9
10
11
12
13
14
15
16
17
7
5.5
6.5
8
4
5
Ph(CH2)3Br
CH3(CH2)3Br
5
Note: The products were identified by spectroscopic techniques NMR, GC-Mass spectral data and melting points and
comparison to authentic samples [45].
Scheme 3. Synthesis of asymmetrical sulfides catalyzed by MOF-199.
in the case of p-trifluoromethyl bromobenzene reactions with alkyl halides (Table 3, entry
11–13). The first alkyl halides tested worked well with this procedure, however, benzyl
chloride was found more reactive than other used alkyl halides (Scheme 3).
As expected, the reaction takes place in two steps via a thiolate (ArS−K+) intermedi-
ate. In order to isolate aryl thiols, reaction of aryl iodides with thiourea under optimized
reaction conditions were investigated. After completion of reactions (3 h), the reactions
mixtures were neutralized with acidic solution (HCl 10%) and thiol derivatives were iso-
lated and characterized (Scheme 4). In this procedure, only aryl thiols were observed and

JOURNAL OF SULFUR CHEMISTRY
5
Scheme 4. Synthesis of aryl thiols, catalyzed by MOF-199.
Scheme 5. Synthesis of symmetrical diaryl disulfides catalyzed by MOF-199.
isolated in PEGs. While, as shown in Table 1, with this procedure benzyl phenyl sul-
fides were obtained in DMF and Toluene in 75% and 30% yields, respectively; without
observation and separation of thiols as intermediates.
This procedure also was successfully examined with regard to synthesis of symmet-
rical diaryl disulfides from aryl halides under optimized reaction conditions. Symmet-
rical diaryl disulfides were prepared from aryl halides after self-oxidation of thiolates
(intermediates) at long reactions time (20 h; Scheme 5).
Catalytic studies
Synthesis and characterization of MOF-199
In this work, the MoF-199 was prepared via a solvothermal method using copper (II)
acetate monohydrate and 1,3,5-benzenetricarboxylic acid in DMF [46].
The material was then characterized using a variety of different techniques; results were
in good agreement with the literature [47]. The (FT-IR) spectra (Figure 1(a)) exhibited
characteristic peak due to the water molecules at wave number 3446 cm−1. Carbonyl group
of benzenetricarboxylic acid and the double bonds of benzene were resonated at 1625 and
1444 cm−1, respectively.
The synthesized MoF-199 were analyzed by using energy-dispersive EDX (Figure 1(b)).
As shown in Figure 1(b), the characteristic peak of Cu showed well that the organic frame-
work was successfully incorporation with Cu metal the crystallinity of the MOF-199 was

6
M. SOLEIMAN-BEIGI ET AL.
a
b
c
d
Figure 1. (a) FT-IR spectra for the MOF-199, (b) EDX spectrum of the MOF-199, (c) X-ray powder
diffractogram for the MOF-199 and (d) SEM micrograph for the MOF-199.

JOURNAL OF SULFUR CHEMISTRY
7
Table 4. Comparison of catalysts activity in sulfide synthesis.
Catalyst
Cul
Cu2O
CuCl2
Cu(OAc)2
MOF-199
Yield (%)
Time (h)
63
24
48
24
71
24
76
24
96
4.5
examined by powder X-ray diffraction (XRD) (Figure 1(c)). The strong and sharp reflec-
tion peaks in XRD pattern prove the crystalline nature of the prepared MoF nanoparticles.
Also, the morphology of the MoF-199 was investigated by scanning electron microscopy
(SEM, Figure 1(d)).
To confirm the advantage of MoF-199 as heterogeneous catalyst rather than usual cop-
per salts for the synthesis of unsymmetrical sulfides from aryl halides and alkyl halides,
to mixture of iodobenzene (1 mmol), thiourea (3 mmol), KOH (3 mmol) and 1.1 mmol of
benzyl chloride was added 10 mol% copper salts such as CuI, CuCl2, Cu2O and Cu (OAc)2
(Table 4). After the completion of these reactions, we obtained benzyl phenyl sulfide with
yields 63%, 48%, 71% and 76% using CuI, Cu2O, CuCl2 and Cu (OAc)2 in 24 h, respectively.
Also, Notably, Firouzabadi and co-workers [20] previously employed CuI as catalyst for the
same reaction with K2CO3 and PEG under N2 and afforded 80 yield of benzyl phenyl sul-
fide in 24 h. This result shows that MOF-199 is an effective catalyst for the synthesis of
unsymmetrical sulfides compared with homogeneous copper catalysts.
The reusability of catalysts is an important advantage in modern catalyst research. Thus
we have studied the possibility of recycling of the catalyst in the reaction of iodobenzene
with benzyl chloride and thiourea in polyethylene glycol. Figure 2 shows the yield of five
consecutive cycles for the preparation of unsymmetrical sulfide. At the end of the pro-
cess, the catalyst was separated from the reaction mixture by simple decantation, and then
washed with copious amounts of n-hexane to remove any physisorbed reagents. The sam-
ple was dried at 160°C for 3 h. Then, fresh substrate was added to the recovered MoF-199
catalyst without any activation and employed for the next reaction. The catalytic activity
was studied for five successive times and it showed a similar activity (Figure 2).
Figure 2. Catalyst recycling studies. Reaction conditions: (a) PhI (1.0 mmol), MOF-199 (4 mg), thiouea
(3 mmol), KOH (3 mmol), benzylchloride (1.1 mmol), temp. 130°C in 2 ml PEG/H2O (20:1) under N2.

8
M. SOLEIMAN-BEIGI ET AL.
Figure 3. X-ray powder diffractogram of (a) MoF-199 and (b) recovered MOF-199.
Figure 4. FT-IR spectra of (a) MoF-199 (b) recovered MOF-199.
To confirm the recoverability and reusability of the MOF-199 in the benzyl phenyl sul-
fide reaction, the nature of the recovered catalyst was investigated by FT-IR and XRD
pattern (Figures 3 and 4). FT-IR and XRD pattern of recovered catalyst show that the cata-
lyst can be recycled five times with maintain its crystallinity and structure during the course
of the reaction.
Conclusions
In conclusion, in this article we have employed a recyclable, porous catalyst for one-pot syn-
thesis of unsymmetrical sulfides and symmetrical diaryl disulfides. The catalyst was also

JOURNAL OF SULFUR CHEMISTRY
9
successfully applied for isolation of aryl thiols as an intermediate in the first step in PEG.
The use of a small amount of catalyst, easily available reagents, ligand-free reaction condi-
tions, a faint odor procedure, short reaction times and high yields are the main advantages
of this procedure.
Experimental
Synthesis of MOF-199
For the synthesis of MoF-199, Benzenetricarboxylic acid (500 mg, 2.38 mmol) was dis-
solved in 12 ml of N,N-dimethylformamide (DMF), C2H5OH and H2O (with ratio
DMF:C2H5OH : H2O = 1:1:1) next a mixture of Cu (OAc)2·H2O (860 mg, 4.31 mmol)
in 12 ml of the same solvent was added and the resulting mixture stirred. Then, Triethy-
lamine (0.5 ml) was added to the reaction mixture, which was stirred for 24 h. The product
was collected by filtration, washed twice with DMF (25 ml) and finally dried.
Unsymmetrical sulfides synthesis; typical experimental procedure
MOF-199 (4 mg) were added to solution of iodobenzene (1.0 mmol), thiourea (0.228 g,
3.0 mmol) and KOH (0.168 g, 3 mmol) in 2 ml PEG/H2O (20:1).The reaction continued
at 130°C under N2 conditions until production of thiolate salt as intermediate after 3.
Then 1.1 mmol benzylchloride was added to mixed reaction and the reaction continued
at 130°C under atmospheric conditions. After completion of the reaction [about 10 h; TLC
(EtOAc/hexane, 1:20) monitoring. CH2Cl2 (20 ml) was added and the mixture was washed
with H2O (2 × 15 ml). The combined organic fractions dried (Na2SO4) and concentrated
under reduced pressure. The residue was purified by preparative chromatography [silica
gel, hexane/EtOAc, 20:1] to give the product.
The synthesis of arylthiols: typical experimental procedure
A mixture of iodobenzene (1.0 mmol), thiourea (0.228 g, 3.0 mmol), KOH (0.168 g,
3 mmol) and MOF-199 (4 mg) was added to a flask containing 2 ml PEG/H2O (20:1).The
reaction continued at 130°C under N2 conditions until production of thiolate salt as
intermediate after 3 h. After cooling and neutralizing reaction mixture by adding acidic
solutions (10 ml, HCl 10%), CH2Cl2 (20 ml) was added to mixture. Then organic layer
was removed and evaporated to give the crude product, which was purified by preparative
chromatography (silica gel, n-hexane–ethyl acetate, 20:1).
Symmetrical diaryl disulfides synthesis: general experimental procedure
The prepared catalyst (4 mg) was added to a mixture of aryl halide (1.0 mmol), thiourea
(0.228 g, 3.0 mmol) KOH (0.168 g, 3.0 mmol) in 2 ml PEG/H2O (20:1) at 130°C under
atmospheric conditions until completion (20 h). The progress of the reaction was moni-
tored by TLC. After removal of solvent, the residue was purified by chromatography (SiO2;
hexane/AcOEt 20: 1) to give the crude diaryl disulfides.

10
M. SOLEIMAN-BEIGI ET AL.
Disclosure Statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by the Ilam University Research Council.
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