A facile and convenient method for synthesis of thiiranes under mild condition using phase transfer catalyst

Article abstract of DOI:10.13005/ojc/290454

A mild and efficient process for preparation of thiiranes with KSCN in water at room temperature using a catalytic amount of 1,4- bis(triphenylphosphonium)-2-butene dichloride is described.

Full text of DOI:10.13005/ojc/290454

ISSN: 0970-020 X
CODEN: OJCHEG
013, Vol. 29, No. (4):
Pg. 1657-1660
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
2
www.orientjchem.org
A Facile and Convenient Method for Synthesis of Thiiranes
under Mild Condition Using Phase Transfer Catalyst
MARYAM GORJIzADEH* and MOzHGAN AFSHARI
Department of Chemistry, Shoushtar Branch, Islamic Azad University,
Shoushtar Iran, 64517-41117, Iran.
*
Corresponding author E-mail: gorji80@yahoo.com
http://dx.doi.org/10.13005/ojc/290454
(Received: October 31, 2013; Accepted: November 15, 2013)
ABSTRACT
A mild and efficient process for preparation of thiiranes with KSCN in water at room
temperature using a catalytic amount of 1,4-bis(triphenylphosphonium)-2-butene dichloride is
described.
Key words: Epoxide; thiirane; 1,4-bis(triphenylphosphonium)-2-butene dichloride;
Phase transfer catalysts.
1
2
13
INTRODUCTION
complexes and cyanuric chloride have been used
for the conversion of oxiranes to thiiranes. However
many of these methods suffer from using strongly
acidic or oxidizing conditions, undesirable side
reactions, long reaction time, high temperature, use
of organic solvents and desulfuration of the resulting
thiirane to the olefin.
Epoxides are among the most useful
synthetic intermediates towards the synthesis of
many biologically active compounds and a large
1
variety of reagents are known for the ring opening
2
of these compounds. Their electrophilic reactions
with different nucleophilic anions have been an
3
interesting subject in organic synthesis. Of these
Thetoxicandvolatilenatureofmanyorganic
solvents, particularly chlorinated hydrocarbons, that
are widely used in organic synthesis have posed a
serious threat to the environment. Consequently
methods that successfully minimize their use are
the focus of much attention. Water as a solvent is
safe, economical and environmentally benign. In
view of the advantages of using water as a solvent,
we explored the synthesis of various types of
thiiranes from oxiranes and potassium thiocyanate
in presence of 1,4-bis(triphenylphosphonium)-2-
anions, the reaction of thiocyanate ion with epoxides
has been widely studied and is a suitable method
for the preparation of thiiranes. Other reagents such
4
5
6
as phosphine sulfide, methylbenzothiazol-2-thione,
7
and dimethylthio formamide have been reported to
produce thiiranes from oxiranes. Usually with these
sulfurating agents, several different Lewis acids such
as RuCl , BiCl and TiO(CF COO) or a protic
acid like TFA or oxalic acid have been employed
14
8
9
10
3
3
3
2
5
11
as catalysts. More recently the b-cyclodextrin

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GORJIꢀADEH & AFSHARI, Orient. J. Chem., Vol. 29(4), 1657-1660 (2013)
13
butene dichloride as an efficient PTC in water at 6.3 (m, 2H), 7.7-8.0 (m, 30H). C NMR, (CDCl3): ´
room temperature.
= 20.7, 120.8, 132.15, 134.2, 137.01, 140.17. Anal.
Calcd: C, 73.055; H, 5.5396; P, 9.5421. found: C,
Phase transfer catalysts (PTCs) are 73.9599; H, 5.5469; P, 9.5531%.
1
5
powerful reagents in chemical transformations,
the characteristics of which include mild reaction Conversion of oxiranes to thiiranes: General
conditions, safety, operational simplicity and Procedure
selectivity. PTCs are often used in nucleophilic
The epoxide (1 mmol), potassium
displacement reactions to facilitate reactions thiocyanate (1 mmol), BTPBDC (0.2 mmol) and
between organic reactants and ionic inorganic salts. water (10 mL) were stirred at room temperature for
Although many phase transfer catalysts are known, an appropriate time. The progress of each reaction
Phosphonium salts are practically important and was monitored by TLC. The reaction mixture was
used in many of organic reactions.
extracted with diethylether (3×10 mL). The organic
solution was concentrated in vacuo, the resulting
product was directly charged on a small silica gel
EXPERIMENTAL
6
0 (0.2-0.5 mm) column 25 Cm and eluted with a
1
All products were characterized by H mixture of ethylacetate and n-hexane (1:4) to afford
13
NMR, C NMR, IR and by comparison with authentic the pure thiirane.
6
,9,16-18
samples
. The IR spectra were recorded on
1
13
Bomem FT-IR spectrometer. H NMR and
C
RESULTS AND DISCUSSION
NMR spectra were taken on a 400 MHz Broucker
spectrometer.The C, H, P analyses were performed
1,4-bis(triphenylphosphonium)-2-butene
by the microanalytical service of research institute dichloride [BTPBDC] was easily prepared by reacting
of petroleum industry (N. I. O. C). Melting points 1,4-dichlorobutene with triphenylphosphine in
were measured on a mettler FP5 apparatus. 1,4- chloroform under reflux condition (Scheme 1). The
bis(triphenylphosphonium)-2-butene dichloride was reaction is very clean and phase transfer catalyst
prepared and other chemicals were purchased from can be easily precipitated in acetone.
the Merck chemical company Darmstadt, Germany.
The purity determination of the products and reaction
We examined the catalytic ability of
monitoring were accomplished by TLC on polygram BTPBDC for conversion of epoxides to thiiranes.
SILG/UV 254 plates.
Therefore, phenyl glycidyl ether (1 mmol) was
reacted with potassium thiocyanate (1 mmol) in
Preparation of 1,4-Bis(triphenylphosphonium)- the presence of BTPBDC in different solvents. The
2-butene Dichloride (BTPBDC)
results were clearly shown water was the best solvent
To a solution of 1,4-dichlorobutene (0.625g, among those tested. TLC analysis was showed at
5
mmol) in CHCl (10 mL) in a 50 mL round-bottomed room temperature, conversion was completed after
3
flask equipped with a magnetic stirrer and a reflux 2.5 h and corresponding thiirane was produced in
condenser was added triphenylphosphine (2.62g, 87% isolated yield. According to obtained results,
1
0 mmol). The reaction mixture was refluxed on this catalyst acted very effciently and it was observed
a water bath for 2.5 h. The solution was cooled to that only 0.2 M equivalent of the catalyst is enough to
room temperature and then, while vigorously stirred, convert different epoxides carrying electron donating
diethylether was added dropwise until an oily product or with-drawing groups to their corresponding
separated. The ether was removed by decantation thiiranes in high isolated yields (Scheme 2, Table
and acetone (40 mL) was added.Stirring the acetone 1).
solution for 40 min afforded a white precipitate which
was filtered, washed with acetone (20 mL) and dried.
It is noteworthy that no evidence for the
Yield 2.596g (80%), m.p. 278-279 °C. IR (KBr):Å formation of olefins as by-product of the reaction
=
1
3053(m), 2755(w), 1613(m), 1575(s), 1478(s), was observed. In organic solvents; the reaction did
437(s), 1258(s), 754(s), 693(s), 556(s) Cm-1. H not complete after 3 h and was contaminated by diol
1
NMR(CDCl3): ´ = 5.7 (dd, JPH=15.7, JHH=8, 4H), and thiocyanohydrine formation. In the absence of

GORJIꢀADEH & AFSHARI, Orient. J. Chem., Vol. 29(4), 1657-1660 (2013)
1659
Table 1: Reaction of different epoxides with KSCN using BTPBDC as catalyst
Entry
Substrate
Product(s)a
Time(h) Yieldb(%)
O
S
Ph
Ph
1
2
2.5
2.5
87
87
O
S
PhOCH2
PhOCH2
S
O
ClCH2
ClCH2
3
4
5
6
3
2
3
92
O
O
S
CH
2
=CHCH
2
OCH
2
CH
2
=CHCH
2
OCH
2
85
S
(
CH
3
)
2
CHOCH
2
(CH
3
)
CHOCH
2
2
91
O
S
CH (CH ) CH OCH
CH (CH ) CH OCH
3 2 2
3
2
2
2
2
2
2
2.5 89
CH
3
S
3
O
O
O
2
H C
2
H C
7
8
O
O
2
3
95
93
O
S
CH
3
CH
2
3 2
CH CH
S
O
9
3.5 85
a
Products were identifed by compared of their physical and spectral data with those of authentic
samples.
catalyst, the conversion of oxiranes was very slow
and the yields were also very low (20% in 6 h). It is
believed that BTPBDC can catalyze the formation
of thiiranes from epoxides in the aqueous phase
in two ways. Firstly by swelling in the aqueous
media it can act as phase transfer catalyst for
the the epoxides, and can therefore provide the
necessary microenvironment for the water-soluble
the epoxides for the reactions to occur. Secondly,
the phosphonium functionalities on these catalyst
can interact as a Lewis acid with the oxygens of the
epoxides to facilitate the attack of the thiocyanate
anion as the nucleophile. It is worthy to note that
the reaction medium was almost neutral, sensitive
functionalities such as carbon-carbon double bonds
remain intact.
-
nucleophile, that is, SCN , to be in the vicinity of
+
CHCl3
+
Cl
Cl + 2 PPh3
PPh3
Cl-
PPh3
2
Reflux
Scheme 1
O
S
KSCN, H O, r.t.
2
BTPBDC
R
R
Scheme 2

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GORJIꢀADEH & AFSHARI, Orient. J. Chem., Vol. 29(4), 1657-1660 (2013)
In conclusion, we have developed a economical and environmental points of view, use of
novel, eco-friendly, and efficient protocol for water as solvent is favorable than organic solvents.
the synthesis of thiiranes with KSCN using 1,4-
bis(triphenylphosphonium)-2-butene dichloride as
a catalyst. This method offers several advantages
including mild reaction conditions, high conversions,
ACKNOWLEDGEMENTS
We are grateful to the Islamic Azad
short reaction times and high isolated yields. It can University Shoushtar Branch for support of this
be emphasized that the reaction is clean and from work.
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