Potassium bromide or sodium chloride catalyzed acetoxyselenenylation of alkenes with diselenides and mCPBA

Article abstract of DOI:10.1016/j.cclet.2015.05.029

KBr or NaCl is found to be a good catalyst in Se-Se bond cleavage of diselenides in the present of the oxidant mCPBA. The electrophilic addition of the in situ generated reactive electrophilic selenium species PhSeX (X = Br, Cl) to alkenes in AcOH provides a convenient access to 2-acetoxy-1-selenides. Compared with other catalysts, KBr or NaCl is less expensive and more environment-friendly.

Full text of DOI:10.1016/j.cclet.2015.05.029

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Chinese Chemical Letters xxx (2015) xxx–xxx
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Chinese Chemical Letters
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Original article
Potassium bromide or sodium chloride catalyzed
acetoxyselenenylation of alkenes with diselenides and mCPBA
Hong-Wei Shi, Chen Yu, Jie Yan *
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310015, China
A R T I C L E I N F O
A B S T R A C T
Article history:
KBr or NaCl is found to be a good catalyst in Se–Se bond cleavage of diselenides in the present of the
oxidant mCPBA. The electrophilic addition of the in situ generated reactive electrophilic selenium species
PhSeX (X = Br, Cl) to alkenes in AcOH provides a convenient access to 2-acetoxy-1-selenides. Compared
with other catalysts, KBr or NaCl is less expensive and more environment-friendly.
ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
Received 11 March 2015
Received in revised form 19 April 2015
Accepted 19 April 2015
Available online xxx
Keywords:
Acetoxyselenenylation
Diselenide
Alkene
Catalysis
1
. Introduction
Organoselenium chemistry has developed as an important
the electrophilic phenylselenium cation is oxidation of diphenyl
diselenide with oxidants such as ammonium peroxydisulfate, m-
nitrobenzenesulfonyl peroxide, Pb(OAc)
4
, Ce(NH
4 2 3 6
) (NO ) and
2
+
+
synthetic tool in the hands of synthetic chemists since the
discovery of the selenoxide elimination in the early 1970s
Cu (Cu )/O systems [24–30]. However, the metal oxidants also
2
have toxicity and some oxidations require long reaction times or
high reaction temperatures, which limit the applications. There-
fore, the discovering of novel and convenient experimental
conditions to carry out the cleavage of Se–Se bond is a really
important target.
[
1–5]. Because of their synthetic applications [6] and biological
activities such as antitumor, antibacterial activities and other
properties [7–14], selenium compounds have been increasing in
importance in recent years. The introduction of organolseleno
groups into organic molecules has been widely studied, in which
the oxyselenenylation reaction is a very useful procedure for the
anti-l,2-addition of an organylseleno group and an oxygen
Recently, we have investigated the new acetoxyselenenylation of
alkenes with a catalytic amount of hypervalent iodine reagent. We
found that when the hypervalent iodine reagent was replaced by
inorganic haloid salts combined with the oxidant m-chloroperben-
zoic acid (mCPBA), the acetoxyselenenylation of alkenes was carried
out smoothly and efficiently with high regioselectivity and good
yields under mild conditions. In order to find cheaper and more
environment-friendly catalysts, we have focused our attention on
bromides and chlorides. Herein, we wish to report a novel and
convenient acetoxyselenenylation of alkenes with diselenides and
mCPBA using widely available KBr or NaCl as catalyst, and to the best
of our knowledge, this electrophilic addition of the in situ generated
reactive electrophilic selenium species PhSeX (X = Br, Cl) to alkenes
has not been previously reported.
2
substituent (HO, RO, RCO ) to an olefin [15–18]. In the electrophilic
addition, the most common selenenylating reagents PhSeX (X = Br,
Cl) are usually commercially available, or they are also prepared
from oxidative cleavage of diphenyl diselenide by halogens
[
19]. However, due to the toxic and moisture-sensitive nature of
PhSeX, nucleophilic halide anions are sometimes responsible for
some undesirable processes such as addition of the halide ion and
the decrease in stereoselectivity. To avoid the above drawbacks,
2 3 2 3
some novel alternative reagents such as PhSeO CCH , PhSeO CCF ,
N-phenylselenophtalimide and N-phenylselenosuccinimide have
been developed [20–23]. Since diphenyl diselenide is less
expensive and less toxic, a much simpler way for formation of
2. Experimental
*
Corresponding author.
A typical procedure for the catalytic acetoxyselenenylation of
E-mail address: jieyan87@zjut.edu.cn (J. Yan).
alkenes using KBr or NaCl as catalyst includes: In AcOH (AR, 99.5%,
http://dx.doi.org/10.1016/j.cclet.2015.05.029
1
001-8417/ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: H.-W. Shi, et al., Potassium bromide or sodium chloride catalyzed acetoxyselenenylation of alkenes
with diselenides and mCPBA, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.029

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2
H.-W. Shi et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
1
.5 mL), alkene 1a (0.6 mmol), diselenide 2a (0.2 mmol), KBr
obvious that KBr played a key role in the reaction. Then, the
acetoxyselenenylation of styrene with diphenyl diselenide and
mCPBA using 0.2 equiv. of Br as catalyst at r.t. for 3 h was optimized
(0.08 mmol) and mCPBA (0.4 mmol) were added successively. The
À
suspension mixture was vigorously stirred at r.t. for 3 h. Upon
completion, the reaction was quenched by addition of sat. aq
(Table 1). As shown in Table 1, with 13 mmol AcOH (0.75 mL), the
Na
was extracted with CH
phase was dried over anhydrous Na
under reduced pressure. The residue was then purified by TLC
technique (4:1 (v/v) petroleum ether/ethyl acetate) to furnish 2-
2
S
2
O
3
(2 mL), sat. aq Na
2
CO
(3Â 5 mL) and the combined organic
SO , filtered, and concentrated
3
(8 mL) and H
2
O (5 mL). The mixture
2 2 3 2
reaction was performed in CH Cl , CH CN, H O and EtOAc
2
Cl
2
respectively; although the amount of AcOH was reduced to half,
it was also greatly in excess, but the yields were not above 71%,
which meant that the reaction was more proper in neat AcOH
(entries 3–6). To reproduce this, the amount of AcOH was reduced to
2
4
acetoxy-1-selenenylation compounds 3a [31] in 90% yield.
3.0 equiv., and the reaction was carried out in CH
O respectively, only rather poor yields were determined (entries
7–9). When NaOAc was substituted for AcOH in CH CN, no desired
2 2 3
Cl , CH CN and
1
Colorless oil; H NMR (500 MHz, CDCl
3
):
d
7.52 (dd, 2H, J = 6.5,
H
2
2
5
2
1
.9 Hz), 7.39–7.30 (m, 5H), 7.30–7.24 (m, 3H), 5.96 (dd, 1H, J = 8.0,
3
.7 Hz), 3.40 (dd, 1H, J = 12.9, 8.0 Hz), 3.25 (dd, 1H, J = 12.9, 5.7 Hz),
product was observed (entry 10). In neat AcOH, several kinds of
bromide sources were studied. Among them, inorganic bromides
usually gave appreciable results and KBr was the most effective
while organic bromine compound led to lowyield (entries 1, 11–15).
13
3
.04 (s, 3H); C NMR (125 MHz, CDCl ): d170.0, 139.4, 133.1,
29.8, 129.1, 128.5, 128.4, 127.2, 126.6, 75.2, 33.4, 21.0; IR (film,
À1
cm ):
%
n
3061, 3033, 1742, 1371, 1236, 1020, 738, 698; MS (EI, m/z,
+
1
): 320 (M , 1.8), 261 (100).
Compared with mCPBA, other oxidants such as Oxone , TBHP,
NaBO
3
Á4H
2 2 2
O and H O usually resulted in moderate, or poor yields
3
. Results and discussion
(entries 1, 16–19). The appropriateamount of mCPBA was 1.0 equiv.,
and when it was absent, no product was observed (entries 1, 20–23).
Finally, the optimum amount of styrene was also determined, and at
1.5 equiv., it was the best choice (entries 21, 24–29).
To achieve the optimum reaction conditions, we first investigat-
ed the reaction of styrene (1a), diphenyl diselenide (2a) and oxidant
mCPBA in the presence of a catalytic amount of KBr in acetic acid at
r.t. When 0.2 equiv. of KBr was added to the mixture of 1.0 equiv. of
In the similar model, we have also optimized the acetoxyse-
lenenylation of styrene with diphenyl diselenide and mCPBA using
0.2 equiv. of Cl as catalyst in AcOH at r.t. The results showed that
À
2
a, 1.2 equiv. of mCPBA and 1.5 equiv. of 1a in acetic acid (1.5 mL)
and the mixture was stirred for3 h, the expected addition product 1-
4
among several chlorides such as KCl, NaCl, NH Cl and CuCl, the
phenyl-2-(phenylselanyl)ethyl acetate 3a was obtained in 83% yield
most effective chloride was NaCl. The optimum amounts of styrene
and mCPBA were 1.5 equiv. and 1.0 equiv., respectively, and the
proper reaction time was 5 h.
(Table 1, entry 1). As a control experiment, the yield of 3a was
observed at only 5% in the absence of KBr (entry 2). Therefore, it was
Table 1
Optimization of the acetoxyselenenylation of styrene using KBr as catalyst.
À
a
Entry
Styrene (equiv.)
Oxidant (equiv.)
Br (equiv.)
AcOH
Solvent
Yield (%)
1
2
3
4
5
6
7
8
9
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.0
1.1
1.2
1.3
1.4
1.8
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
mCPBA (1.2)
Oxone (1.2)
TBHP (1.2)
KBr (0.2)
–
1.5 mL
1.5 mL
0.75 mL
0.75 mL
0.75 mL
0.75 mL
3.0 equiv.
3.0 equiv.
3.0 equiv.
3.0 equiv.
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
1.5 mL
–
–
83
5
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
NaBr (0.2)
CH
CH
2
Cl
CN
2
63
66
35
71
10
11
0
3
2
H O
EtOAc
CH
CH
2
Cl
CN
2
3
2
H O
b
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
CH
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
3
CN
0
81
75
69
73
31
67
68
35
61
66
90
85
0
(C
CuBr (0.2)
NH Br (0.2)
CH (CH Br (0.2)
4 9 4
H ) NBr (0.2)
4
3
2 3
)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBr (0.2)
KBO
3
Á4H
2
O (1.2)
2 2
H O (1.2)
mCPBA (1.4)
mCPBA (1.0)
mCPBA (0.8)
–
mCPBA (1.0)
mCPBA (1.0)
mCPBA (1.0)
mCPBA (1.0)
mCPBA (1.0)
mCPBA (1.0)
80
80
83
84
86
89
a
Isolated yield.
b
3
.0 equiv. of NaOAc was added.
Please cite this article in press as: H.-W. Shi, et al., Potassium bromide or sodium chloride catalyzed acetoxyselenenylation of alkenes
with diselenides and mCPBA, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.029

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3
Table 2
Preparation of 2-acetoxy-1-selenenylation compounds 3.
.
a
a
Entry
1
1
2
3
Yield (%)
Entry
8
1
2
3
Yield (%)
b
b
PhSeSePh
90 (88)
2a
65 (54)
2a
b
b
2
2a
85 (79)
9
2a
94 (92)
b
3
4
2a
2a
72 (70)
10
11
2a
2a
44
62
b
81 (94)
b
5
6
7
a
2a
2a
2a
86
12
13
14
1a
1b
1f
(PhCH
2
Se)
2
71 (78)
2b
b
b
84 (83)
2b
2b
80 (79)
b
b
88 (86)
78 (78)
Isolated yields from Method 1.
Yields from Method 2.
b
Having established the optimum conditions, the acetoxysele-
nenylation of 1.0 equiv. of diselenides (1), 1.5 equiv. of alkenes (2)
and 1.0 equiv. of mCPBA with 0.2 equiv. of KBr in AcOH at r.t. for 3 h
Method 1), or with 0.2 equiv. of NaCl in AcOH at r.t. for 5 h
Method 2) was carried out, a series of corresponding 2-acetoxy-1-
selenenylation compounds (3) were obtained; the results are
summarized in Table 2.
As shown in Table 2, the reaction was compatible with most of
the studied alkenes except bicyclo[2.2.1]hept-2-ene (1j), which
provided the corresponding 2-acetoxy-1-selenenylation com-
pounds in good to excellent yields (entries 1–14). It was also
determined that the groups on the benzene ring, no matter
whether they were electron-donating or electron-withdrawing
groups, did not influence the yield (entries 2–7, 13, 14). When
treated under the same conditions, the addition to cyclohexene
A proposed catalytic cycle for the KBr or NaCl mediated
acetoxyselenenylation of alkenes is shown in Scheme 1. Thus, KBr
is first oxidized by mCPBA to molecular bromine, which reacts with
diselenide 2 to furnish the electrophilic reagent A. Then, the
following an electrophilic addition of the in situ generated active
ArSeBr to alkenes results in a cyclic intermediate B. After a
solvolysis of B in AcOH, the desired product 2-acetoxy-1-
selenenylation compound 3 as a single isomer is obtained via an
(
(
S
N
1 mechanism for the aromatic alkenes. When aliphatic alkenes
such as 1i and 1j are used as alkene substrates, the reaction
N
provides the trans single stereoisomers via an S 2 mechanism,
Se
Ar
Ar
Se
2
(
1i) and 1j proceeded in
stereoisomers were isolated with an excellent yield for 3i (entry
) and a poor yield for 3j due to the steric hinderance effect of the
a trans fashion and the single
Br
2
Ar-Se-Br
9
A
m-CBA
methylene group (entry 10). Compared with 2a, the dibenzyl
diselenide (2b), an aliphatic diselenide, also reacted easily with
alkenes, but the yields were slightly lower (entries 12–14). From
Table 2, it is obvious that the yields for most products 3 were
higher when KBr was used as catalyst as opposed to NaCl, so
the catalytic effect of KBr is better than NaCl in the acetoxy-
selenenylation of alkenes.
R
1
Ar
Se
AcO
AcOH
R
SeAr
3
R
B
m-CPBA
Br
Scheme 1. Proposed mechanism for the catalyzed acetoxyselenenylation.
Please cite this article in press as: H.-W. Shi, et al., Potassium bromide or sodium chloride catalyzed acetoxyselenenylation of alkenes
with diselenides and mCPBA, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.029

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H.-W. Shi et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
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429–434.
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Please cite this article in press as: H.-W. Shi, et al., Potassium bromide or sodium chloride catalyzed acetoxyselenenylation of alkenes
with diselenides and mCPBA, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.05.029