Epoxidation of vinyl cyanides by calcium hypochlorite under catalyst- and solvent-free conditions

Article abstract of DOI:10.1016/j.tetlet.2018.05.077

In this paper, epoxidation of a wide range of alkenes by calcium hypochlorite (Ca(OCl)₂) was investigated under catalyst- and solvent-free conditions. It was noticed that the highest yield was achieved with crushing, when the reaction was betwe

Full text of DOI:10.1016/j.tetlet.2018.05.077

Accepted Manuscript
Epoxidation of Vinyl Cyanides by Calcium Hypochlorite under Catalyst- and
Solvent-free Conditions
F. Mirhashemi, M.A. Amrollahi
PII:
S0040-4039(18)30702-0
https://doi.org/10.1016/j.tetlet.2018.05.077
TETL 50024
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Reference:
Tetrahedron Letters
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Please cite this article as: Mirhashemi, F., Amrollahi, M.A., Epoxidation of Vinyl Cyanides by Calcium Hypochlorite
under Catalyst- and Solvent-free Conditions, Tetrahedron Letters (2018), doi: https://doi.org/10.1016/j.tetlet.
2018.05.077
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Tetrahedron Letters
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Epoxidation of Vinyl Cyanides by Calcium Hypochlorite under Catalyst- and
Solvent-free Conditions
F. Mirhashemi, M. A. Amrollahi∗
Department of Chemistry, Yazd University, Yazd, Iran
ARTICLE INFO
ABSTRACT
Article history:
Received
In this paper, epoxidation of a wide range of alkenes by calcium hypochlorite (Ca(OCl)2) was
investigated under catalyst- and solvent-free conditions. It was noticed that the highest yield was
achieved with crushing, when the reaction was between vinyl cyanides and Ca(OCl)2. The
structure of the synthesized epoxides was confirmed by IR, 1H- and 13C-NMR and elemental
analysis. Short reaction times, the use of a simple experimental procedure, and reducing of
energy consumption are other important advantages of our work that could be mentioned too.
Received in revised form
Accepted
Available online
Keywords:
2009 Elsevier Ltd. All rights reserved.
Epoxidation
Calcium hypochlorite
Catalyst-free
Solvent-free
Crushing
Epoxides are an important class of organic compounds which
are widely used in organic reactions due to their properties such
as very useful balance between stability and reactivity resulting
from high ring strain.1 Epoxide derivatives have been found to be
good raw material for epoxy resin, paints, surfactant, polymers
and important intermediates for making valuable products in
organic synthesis.2-4 Furthermore, epoxides have been used as a
precursor and highly useful building block for the synthesis of
bioactive compounds in many reactions.5-8 Based on foregoing,
synthesis of epoxides from alkenes has attracted considerable
attention. For this purpose several methods have been reported
recently. For example, epoxidation of alkenes by
tetrabutylammonium monopersulfat in the presence of Mn (III)-
salen,9 by NaOCl and urea H2O2 in the presence of chiral
macrocyclicsalen Mn (III) complexes,10 by tert-butyl
hydroperoxide in the presence of oxidovanadium (IV)
tetradentate schiff base complex,11 by H2O2 in the presence of
manganese complex,12 and by H2O2 in the presence of Iron13 have
been reported. Epoxidation of alkenes were also carried out by
using of other reagents such as peroxybenzoic acid, peracids,
and catalysts. Thus, the introduction of new methods and /or
further work on technical improvements to overcome these
limitations is still needed.
Table 1. Comparative methods for the epoxidation of 2-
benzylidenemalononitrile
Entry
Oxidant
Conditions
Time
Yield
(%)
Ref
Catalyst/Solvent//Temp
(OC)
1
2
Hypochlorous
acid
-
-
[23]
[24]
acetonitrile/0-80
CHPa
24(h)
78
multifunctional
cinchona derived
thiourea/toluene/-20
catalyst-free/solvent-
free/crushing
3
Ca(OCl)2
20(min)
90
this
work
acumyl hydroperoxide.
NaIO4,
PhIO,
tert-butylhydroperoxide
(TBHP)
and
aldehyde/Oxone in the presence of appropriate catalyst.14-22
Epoxidation of 2-benzylidenemalononitrile was first reported in
In conjunction with our ongoing research program involving
the oxidation of 2-(methyl)malononitriles by Ca(OCl)2,25 in this
paper, we report an efficient, simple, green, facial and cost-
effective method for the epoxidation of vinyl cyanide derivatives
by Ca(OCl)2 under catalyst- and solvent-free conditions at room
temperature.
1967 (Table 1,
entry 1).23
Epoxidation of
2-
benzylidenemalononitrile was also reported by Meninno, et al. in
2015 (Table 1, entry 2).24 However, these methods for
epoxidation of 2-benzylidenemalononitrile and its derivatives
have not been entirely satisfactory and involve some
disadvantages such as long reaction times, use of organic
solvents and generally need expensive or non-available reagents
———
∗ Corresponding author: Tel.: 0098-353-821-0644; fax: 0098-353-821-0644; e-mail: mamrollahi@yazd.ac.ir

2
Tetrahedron
In our initial study, the reaction of 2-benzylidenemalononitrile
was confirmed the synthesis of 3-phenyloxirane-2,2-
dicarbonitrile (Scheme 1).
(1mmol) and Ca(OCl)2 was considered as a model reaction to
optimize the conditions. To find the best solvent, several solvents
such as H2O, EtOH, MeCN, and n-hexane were employed as
media. However, it was noticed that the highest yield was
achieved under solvent-free conditions with crushing the mixture
of 2-benzylidenemalononitrile and Ca(OCl)2 (Table 2, entry 5).
Similar reactions were then attempted in the presence of 0.5, 0.7,
0.8 and 1.0 mmol of Ca(OCl)2. The results show that the use of
0.8 mmol of Ca(OCl)2 under solvent-free conditions is sufficient
to push the reaction forward. Greater amounts of the oxidant had
no significant influence on the reaction time (Table 2, entry 6).
To scale-up the reaction, epoxidation was performed on the 2,
4, and 6 mmol scales under solvent-free conditions. The
obtained results indicate without changing reaction times
producing similar yields. Other oxidation reagents such as
anhydrous LiOCl, NaOCl, NaIO3, NaIO4, oxone and
trichloromelamin, were also used. No reaction occurred with
these oxidants under optimized conditions and only a 20 % yield
was obtained by anhydrous LiOCl (Table 2 entries 9-14). Finally,
we found that this reaction optimally proceeded by crushing 2-
benzylidenemalononitrile with Ca(OCl)2 and completed within
20 min to afford the corresponding products (2a-o) in high yields.
Scheme 1. Structure of 3-phenyloxirane-2,2-dicarbonitrile (2a)
Under optimized conditions, 3-aryloxirane-2-carbonitriles (2a-
o) were synthesized. In all cases, the reactions proceeded
efficiently under solvent- and catalyst-free conditions to afford
the corresponding products in high yields. The results are
summarized in Table 3. It can be observed that the process
tolerates both electron-donating and withdrawing substituent in
benzaldehyde. All the products were characterized by FT-IR,1H-
and 13C-NMR spectra, m.p. and elemental analysis.
Table 3. Epoxidation of vinyl cyanide by Ca(OCl)2 under
catalyst- and solvent-free conditions
Table 2. Optimization of the epoxidation reaction of 2-
benzylidenemalononitrile under various conditions
at room temperature
Entry
R1
R2
Product Time
(min)
Yield
(%)
Mp
(oC)
1
2
Ph
CN
CN
CN
CN
CN
2a
2b
2c
2d
2e
2f
20
120
120
120
130
150
120
120
30
90
89
89
86
79
75
98
99
91
93
90
87
81
99
99
30
51
87-89
128
4-F C6H4
4-Cl C6H4
4-Br C6H4
4-CH3 C6H4
3
4
129-130
75
5
6
4-OCH3 C6H4 CN
79
Entry
1
Oxidant (mmol)
Ca(OCl)2(0.8)
Conditions
H2O/r.t
Yield (%)
Trace
7
4-NO2 C6H4
2-NO2 C6H4
Ph
CN
2g
2h
2i
177
8
CN
128-129
Oil
Ca(OCl)2(0.8)
Ca(OCl)2(0.8)
Ca(OCl)2(0.8)
Ca(OCl)2(0.8)
Ca(OCl)2(1.0)
Ca(OCl)2(0.7)
Ca(OCl)2(0.7)
LiOCl (anhydrous)
NaOCl
EtOH/r.t
2
3
Trace
20
9
CO2Et
CO2Et
CO2Et
CO2Et
10
11
12
13
14
15
16
4-F C6H4
4-Cl C6H4
4-Br C6H4
2j
40
Oil
MeCN/r.t
2k
2l
90
70-72
94
n-Hexane/r.t
4
35
100
60
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
Solvent-free/crushing
5
90
4-CH3 C6H4 CO2Et
4-NO2 C6H4 CO2Et
2-NO2 C6H4 CO2Et
2m
2n
2o
-
63
120
90
128-130
61
6
90
7
85
Ph
CONH2
150
-
Reaction conditions: vinyl cyanide (1 mmol), (Ca(OCl)2 (0.8 mmol), solvent-
free.
8
60
9
20
It should be noted that the epoxidation reaction was also
carried out with some other alkenes such as cyclohexene, cis-
cyclooctene, styrene, α-methyl styrene, β-nitro styrene (E)-
Stilbene and indene under optimized conditions. In all these
cases, the product was not formed or formed in lower yields
(Table 4). By a comparison of the results in Table 3 with Table 4,
the reactions proceeded efficiently when the reaction was
between vinyl cyanides and Ca(OCl)2.
Trace
10
11
12
13
14
NaIO3
-
-
-
-
NaIO4
Oxone
Tricholoromelamin
The synthesized epoxide was characterized by IR, 1H- and
13C-NMR spectra, m.p. and elemental analysis. The IR spectrum
of 3-phenyloxirane-2,2-dicarbonitrile (2a) showed a strong band
at 1191 cm-1 related to stretching vibration of C-O bond. The
C=C stretching vibration of phenyl ring appeared at 1497 and
Table 4. Epoxidation of various alkenes by Ca(OCl)2 under
catalyst- and solvent-free conditions at room temperature
Entry
Alkenes
Cyclohexene
cis-cyclooctene
Styrene
Yield (%)
Trace
Trace
-
1
2
3
4
5
5
6
1605cm-1. The C
≡N stretching absorption band was also
observed at 2260cm-1. 1H-NMR spectrum of 2a exhibited a sharp
singlet (δ = 4.74 ppm) for 1H of the epoxide ring and a multiple
(δ = 7.45-7.57 ppm) for the 5H of phenyl group. The 13C-NMR
spectrum of 2a consisted of the signals at 41.8 and 65.8 ppm for
the C3 and C2 of the epoxide ring respectively, the signals at
110.3 and 111.7 ppm for the carbon atoms of the nitrile groups
and finally the peaks at 126.8-131.4 ppm for the carbon atoms of
phenyl ring. The elemental analysis of 2a showed the existing of
carbon (70.3%), hydrogen (3.4%) and nitrogen (16.5%) which it
α-methyl styrene
β-nitro styrene
(E)-Stilbene
Indene
-
Trace
Trace
Trace
Reaction conditions: alkene (1 mmol), Ca(OCl)2 (0.8 mmol), solvent-free,
crushing.
Although the mechanism of the reaction has not been
established experimentally, based on our experimental results

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observed in Tables 3 and 4, the formation of the product can be
rationalized as outlined in the Scheme 2
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2015, 17, 2042-2058. (b) Oloo, W. N.; W.; Que Jr, L. Acc. Chem.
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Scheme 2. The proposed mechanism for the epoxidation of vinyl
cyanides by Ca(OCl)2
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35.
In summary, we have developed an improved and convenient
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Ca(OCl)2 under catalyst- and solvent-free conditions. The
remarkable advantages of this method are simple experimental
procedure, short reaction times, high yields, and the ease of
product isolation.
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Typical procedure for the preparation of 3-phenyloxirane-
2,2-dicarbonitrile
2-Benzylidenemalononitrile (1mmol) and Ca(OCl)2 (0.8
mmol) were crushing in a mortar at room temperature for 20 min.
After completion of the reaction, the mixture was dissolved in
CH2Cl2 and filtered. The solvent of the resulting filtrate was
evaporated and a pure product was obtained by recrystallization
from ethanol with yield of 90%. The authenticity of the product
was established by the data of IR, 1H-NMR, 13C-NMR and
elemental analysis.
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92-101.
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Acknowledgments
The authors thank the Research Council of Yazd University for
the financial support.
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22. Zhang, J.; Biradar, A. V.; Pramanik, S.; Emge, T. J.; Asefa, T.; Li,
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References and notes
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4
Tetrahedron
Highlights
• The epoxidation of vinyl cyanides by
Ca(OCl)2 was investigated for the
first time.
• Ca(OCl)2 proved to be the best
oxidant for the epoxidation of vinyl
cyanides.
• The epoxide was not formed or
formed in lower yields by other
oxidants.

Graphical Abstract
Epoxidation of Vinyl Cyanides by Calcium
Hypochlorite under Catalyst- and Solvent-
free Conditions
F. Mirhashemi, M. A. Amrollahi∗
15 examples
75–99% yield
room temperature
solvent- and catalyst-free
O
R2
CN
R2
Ca(OCl)2
Crushing
R1
R1
CN
2a-o
1a-o
R1 = Ph, 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 4-CH3C6H4, 4-OCH3C6H4, 4-NO2C6H4, 2-NO2C6H4
R2 = CN, CO2Et, CONH2