A rapid, efficient and green procedure for transformation of alkyl halides/ tosylates to organochalcogens in water

Article abstract of DOI:10.1080/10426507.2017.1370592

A one-pot and efficient synthesis of dialkyl dichalcogenides (S, Se) in aqueous media under catalyst-free conditions using benzylic, allylic and primary halides with elemental sulfur and selenium has been developed. Also, this procedure was extended to preparation of trisulfides and triselenides from secondary and tertiary halides in same condition. In all cases, products can be obtained in good to excellent yield in short reactions time.

Full text of DOI:10.1080/10426507.2017.1370592

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: http://www.tandfonline.com/loi/gpss20
A Rapid, Efficient and Green Procedure for
Transformation of Alkyl Halides/Tosylates to
Organochalcogens in Water
Mohammad Soleiman-Beigi, Issa Yavari & Fatemeh Sadeghizadeh
To cite this article: Mohammad Soleiman-Beigi, Issa Yavari & Fatemeh Sadeghizadeh (2017):
A Rapid, Efficient and Green Procedure for Transformation of Alkyl Halides/Tosylates to
Organochalcogens in Water, Phosphorus, Sulfur, and Silicon and the Related Elements, DOI:
10.1080/10426507.2017.1370592
To link to this article: http://dx.doi.org/10.1080/10426507.2017.1370592
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A Rapid, Efficient and Green Procedure for Transformation of Alkyl Halides/ Tosylates to
Organochalcogens in Water
Mohammad Soleiman-Beigia, Issa Yavari b, Fatemeh Sadeghizadeh a
a Department of Chemistry, Basic of Sciences Faculty, Ilam University, P.O. Box 69315-516,
Ilam, Iran
E-mail: SoleimanBeigi@yahoo.com; m.soleimanbeigi@mail.ilam.ac.ir
b Department of Chemistry, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
E-mail: yavarisa@modares.ac.ir
Abstract: A one-pot and efficient synthesis of dialkyl dichalcogenides (S, Se) in aqueous media
under catalyst-free conditions using benzylic, allylic and primary halides with elemental sulfur
and selenium has been developed. Also, this procedure was extended to preparation of trisulfides
and triselenides from secondary and tertiary halides in same condition. In all cases, products can
be obtained in good to excellent yield in short reactions time.
Key words: dialkyldichalcogenides, trisulfide, triselenide, sulfur, selenium.
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INTRODUCTION
Recently, in organic synthetic methodology, avoiding the use of harmful/toxic solvents is a
highly challenging task. The aqueous-mediated reactions due to advantages such as safety,
simplicity, environmentally acceptable, height yield and no waste have attracted much attention
[1]. In general, water is considered as a ‘‘green solvent’’ for chemical reactions; it is cheap,
abundantly available, nontoxic, non-flammable and eco-friendly [2]. Significant surface tension,
high specific heat, high dielectric constant polarity and hydrogen bonding are unique physical
properties of water [3].
Organic dichalcogenides are used extensively in biological, organic synthetic and industrial
applications [4]. Several types of these compounds possess a wide spectrum of biological
properties, For instance, diselenides have been used as antioxidants, anti-ulcer, anti-
inflammatory and antitumor [5]. Also disulfides are essential moieties in biologically active
compounds such as enzymes, antibodies, peptides and hormones [6].
Much is known about the importance of organic trisulfides [7]. Trisulfide linkage is an
important functional group in esperamicin and tumor inhibitors calicheamicin [8], which are
members of the enediyne group of antibiotics [9]. Allyl methyl trisulfane [10], the mixed
trisulfide between cysteine and glutathione [11], and sporidesmin [12] are important natural
products that contain trisulfide bridges.
A traditional method for synthesis of diselenides derivatives is the reaction of elemental
selenium with various reducing agents to produce selenide (Se2-) or diselenide (−SeSe−) and then
reaction with alkyl/aryl halides or –pseudohalides [13]. Also, the oxidation of thiols with many
oxidating agents is a common synthetic method for the synthesis of organic disulfide and
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trisulfide compounds [14]. But, this method has disadvantages such as difficult work-ups and the
use of toxic, odorous and volatile thiols. To overcome these difficulties, attention has been
directed toward the synthesis of disulfides and trisulfides from aryl/alkyl halides in the presence
sulfur-transfer reagents [15]. Among these reagents, the use of sulfur powder has emerged as one
of the more important ones.
Considering the importance of environmentally friendly protocols in organic chemistry, we
wish to report the utilization of an aqueous media without the assistance of any phase transfer
catalyst for the simple, efficient synthesis of organochalcogens (S, Se). Thus in continuation of
our efforts on the synthesis of organochalcogen compounds [13a, 16], we report a simple, rapid
and efficient strategy for the domino synthesis dialkyl dichalcogonides and dialkyl
trichalcogonides from alkyl halides and alkyl tosylates using sulfur and selenium powders as
available and cost effective sources in present of KOH in water.
RESULTS AND DISCUSSION
The reaction of benzyl chloride (1a) with elemental selenium powder (2a) in the presence of
KOH was studied under normal atmospheric conditions in order to optimize the reaction
conditions in terms of amount of solvent, temperature, type and amount of base (Table 1, entry
1). A control experiment showed that the time of the reaction was dependent on quantity of water
used and the use of 0.5 mL water was the most effective, whereas increasing quantities of water
led to a decrease in the rate of the reaction (Table 1, entries 1,2). According to the results shown
in Table 1, lowering the temperature from 60 to room temperature led to reduced yield, while
increasing the temperature to 100 °C had no effect on the product yield (Table 1, entry 3, 4). The
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reaction did not proceed in the absence of a base, and among several bases screened, Potassium
hydroxide (KOH) with amount of 4 mmol was the best (Table 1, entry 5-11).
Thus, based on Table 1, the best reaction conditions were: 2 mmol of alkylhalide, 2 mmol of
elemental selenium powder and 4 mmol of KOH in water at 60 °C in air.
To explore further the utility of this method, several alkyl halides were reacted under the
optimized reaction conditions, as shown in Table 2, primary, benzylic and allylic halides were
efficiently treated with Se or S generating the corresponding diselenides and disulfides as only
product in good yields. We also extended our studies for the synthesis of organochalcogenides
from alkyl tosylate (Table 2). benzylic halides were worked fine with this procedure however
benzyl bromide was found somewhat reactive than other used alkyl halides (Table 2, entry 1,2,
14,15).
Furthermore, in this study we observed that the steric hindrance significantly affected the
numbers of S−S bonds in target products. Trisulfides (S−S−S) and triselenide (Se−Se−Se) are
obtained in the presence of secondary and tertiary alkyl halides such as iso-propylbromide and
tert-butylbromide, while primary alkyl halides yield disulfide derivatives (Scheme 2 and Table
2). This subject is another important feature of this method compared with reported methods
[17].
1
The structure of a number of products were deduced from their H NMR, 13C NMR
spectroscopic, GC-Mass spectrometric and UV visible spectroscopic. GC-Mass spectrum has
been used to determine of trichalcogenides or dichalcogenides. Information afforded from GC-
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MS show that secondary and tertiary halides formed trisulfides and triselenides, meanwhile
primary alkyl halides yielded disulfide and diselenide derivatives (Supplemental Materials,
Figures S 16, S 21, S 24 S 27). UV spectra for disulfide and trisulfide show that trisulfides have
an absorption at 365 nm while disulfides lack of this absorption. These results were confirmed by
thin layer chromatography at wave length at 365 nm (Figure S 7).
CONCLUSION
In summary, we have developed a simple, efficient and practical method for the preparation
of symmetrical organochalcogenides (dialkyl dichalcogenides and dialkyl trichalcogenides) from
various alkyl halides (and-OTs) and sulphur or selenium in water. Elements of green chemistry
include: accomplishment reaction in domino and one-pot condition, employing water as a
reaction medium instead of the usually used organic solvents, and utilization of environmentally
benign protocols. Short reaction times, easy work-up, high yields and exclusive product
formation are other advantages of our new procedure.
EXPERIMENTAL
The reactions were performed under normal atmosphere condition. Chemical reagents were
purchased from Sigma-Aldrich, Alfa Aesar or Merck and used as received without further
1
purification. H NMR and 13C NMR spectra were recorded in CDCl3 with tetramethylsilane
1
(TMS) as reference on a Bruker AMX 400 spectrometer operating at 400 MHz for for H NMR
and 100 MHz for 13C NMR. Evolution of the reaction, when indicated, was monitored by
analytical thin-layer chromatography using silica gel 60 F254 precoated plates (E. Merck).
Compounds were visualized by 365 nm light. Plate chromatography was performed on silica gel
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60 GF254 using EtOAc–hexane mixtures as the eluent. The absorption of the samples were
measured on JASCO V-570 UV-visible spectroscopy photometer. The Supplemental Materials
contains characterization information for the known products (Figures S 1 – S 25).
Symmetrical dialkyl disulfides and dialkyl diselenides synthesis; General Procedure
RX (2.0 mmol), S (0.064 g, 2.0 mmol) and KOH (0.224 g, 4 mmol) were added a flask
containing H2O (0.5 mL). The reaction mixture was stirred at 60°C under atmospheric conditions
until completion (30 min). Upon completion of the reaction, the mixture was extracted with
CH2Cl2 (3 × 5 mL) and the combined organic phase was dried over anhydrous Na2SO4, filtered,
and concentrated under reduced pressure. After, the residue was purified by plate
chromatography to afford the corresponding product. Diselenides were synthesized analogously
starting from selenium powder.
Symmetrical dialkyl trisulfides and dialkyl triselenides synthesis; General Procedure
In H2O (0.5 mL), RX (2.0 mmol), S (0.096 g, 3.0 mmol) and KOH (0.224 g, 4 mmol) were
added successively at 60 °C under atmospheric conditions until completion (30 min). The
progress of reaction was monitored by TLC. Upon completion of the reaction, the mixture was
extracted with CH2Cl2 (3 × 5 mL) and the combined organic phase was dried over anhydrous
Na2SO4. Then, crude diallyl trisulfides was obtained by plate chromatography (silica gel, n-
hexane–ethyl acetate, 20:1). Triselenides was synthesized analogously starting from selenium
powder.
ACKNOLEDGEMENT
Financial support from Ilam University research council is gratefully acknowledged.
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Table 1 Optimization of Reaction Conditiona
Entry
Base(mmol) H2O(xml) Time(min) Yield(%)
Temp
60
1
2
KOH (4)
KOH (4)
KOH (4)
KOH (4)
-
1
240
30
76
94
32
92
N0
62
94
47
34
65
58
60
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
3
25
120
30
4
100
60
5
120
120
30
6
60
KOH (2)
KOH (8)
7
60
8
60
KF/Al2O3
(4)
30
9
60
K2CO3 (4)
30
10
11
60
NaOH(4)
EtN3(4)
30
60
30
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Table 2 The Synthesis of dichalcogenides from alkyl halides (and tosylate)
Entry
RX
RZZR
Yield (%)
Ref
1
3a
3a
3a
3b
3b
3c
3d
3d
3e
3f
94%
97%
87%
90%
81%
95%
90%
82%
85%
83%
76%
18a
PhCH2Cl
PhCH2Br
PhCH2SeSeCH2Ph
PhCH2SeSeCH2Ph
2
18a
18a
13b
13b
-
3
PhCH2OTs
PhCH2SeSeCH2Ph
4
Ph(CH2)2Br
Ph(CH2)2OTs
Ph(CH2)3Br
CH3(CH2)3Br
CH3(CH2)3OTs
CH3(CH2)6Br
CH3(CH2)7Br
CH3(CH2)7OTs
Ph(CH2)2SeSe(CH2)2Ph
Ph(CH2)2SeSe(CH2)2Ph
Ph(CH2)3SeSe(CH2)3Ph
CH3(CH2)3SeSe(CH2)3CH3
CH3(CH2)3SeSe(CH2)3CH3
CH3(CH2)6SeSe(CH2)6CH3
CH3(CH2)7SeSe(CH2)7CH3
CH3(CH2)7SeSe(CH2)7CH3
5
6
7
13c
13c
13d
18b
18b
8
9
10
11
3f
12
13
14
4a
4a
4a
90%
92%
83%
16c
16c
16c
PhCH2Cl
PhCH2Br
PhCH2OTs
PhCH2SSCH2Ph
PhCH2SSCH2Ph
PhCH2SSCH2Ph
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15
16
4b
4b
87%
78%
16c
16c
Ph(CH2)2Br
Ph(CH2)2OTs
Ph(CH2)3Br
Ph(CH2)2SS (CH2)2Ph
Ph(CH2)2SS (CH2)2Ph
Ph(CH2)3SS (CH2)3Ph
CH3(CH2)2SS (CH2)2CH3
CH3(CH2)3SS (CH2)3CH3
CH3(CH2)3SS (CH2)3CH3
4c
91%
80%
16c
19b
17
4d
CH3(CH2)2Br
CH3(CH2)3Br
CH3(CH2)3OTs
18
19
4e
4e
4f
88%
76%
85%
19c
19c
19a
20
21
CH3(CH2)7Br
CH3(CH2)7SS (CH2)7CH3
CH3(CH2)7SS (CH2)7CH3
CH2=CHCH2SS CH2CH=CH2
CH3(CH2)7OTs
CH2=CHCH2Br
4f
80%
86%
19a
19b
22
23
4g
a Reaction conditions: various alkyl halides (2.0 mmol), sulfur or selenide (2 mmol), KOH(4.0 mmol) in 0.5 ml H2O 60 °C, 30
min.
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Scheme 1: The synthesis of dichalcogonides and trichalcogonides
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Scheme 2: Alkyl halide or alkyl tosylate (2.0 mmol), S or Se powder (3mmol) in 0.5 ml H2O. in
all reactions less than 10% of dialkyl disulfide and dialkyl diselenide was detected.
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