Synthesis of diaryl selenides using electrophilic selenium species and nucleophilic boron reagents in ionic liquids

Article abstract of DOI:10.1039/c1gc15725f

We described herein the use of imidazolium ionic liquids [bmim]PF ₆ and [bmim]BF₄ in the selective, metal and catalyst-free synthesis of unsymmetrical diaryl selenides by electrophilic substitution in arylboron reagents with arylselenium halides (Cl and Br) at room temperature. This is a general substitution reaction and it was performed with arylboronic acids or potassium aryltrifluoroborates bearing electron-withdrawing or electron-donating groups, affording the corresponding diaryl selenides in good to excellent yields. The ionic liquid [bmim][PF₆] was easily recovered and utilized for further substitution reactions.

Full text of DOI:10.1039/c1gc15725f

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PAPER
Synthesis of diaryl selenides using electrophilic selenium species and
nucleophilic boron reagents in ionic liquids†
a
a
a
b
a
Camilo S. Freitas, Angelita M. Barcellos, Vanessa G. Ricordi, Jesus M. Pena, Gelson Perin,
a
a
a
Raquel G. Jacob, Eder J. Lenard a˜ o* and Diego Alves*
Received 20th June 2011, Accepted 19th July 2011
DOI: 10.1039/c1gc15725f
We described herein the use of imidazolium ionic liquids [bmim]PF
6
and [bmim]BF in the
4
selective, metal and catalyst-free synthesis of unsymmetrical diaryl selenides by electrophilic
substitution in arylboron reagents with arylselenium halides (Cl and Br) at room temperature.
This is a general substitution reaction and it was performed with arylboronic acids or potassium
aryltrifluoroborates bearing electron-withdrawing or electron-donating groups, affording the
corresponding diaryl selenides in good to excellent yields. The ionic liquid [bmim][PF
recovered and utilized for further substitution reactions.
6
] was easily
Introduction
sulfate in the electrophilic substitution reactions of organob-
orane, organosilanes and organostannanes by phenylselenium
bromide, providing a novel and efficient route to the synthesis
The versatility and applicability of organoselenium compounds
in organic chemistry is well described in a great number of
8a
of diaryl selenides.
1
2
reviews and books. Organoselenium compounds are attractive
In this sense, the development of environmentally benign
and clean synthetic methods for the synthesis of diarylse-
lenides, including those involving solvent-free or the use of
alternative solvents, has increased in recent years. In this
way, ionic liquids (ILs), especially those based on the 1,3-
dialkylimidazolium cation, constitute an interesting alternative
1
,2
synthetic targets because of their selective reactions, their
use as ionic liquids and in asymmetric catalysis,
3
1b,4
their
5
fluorescent properties and because of their interesting biological
6
activities. Many classes of organoselenium compounds have
been prepared and widely studied, and among them aryl- and
vinyl selenides are certainly the most applied compounds in
organic synthesis. Regarding the selenium species used as
starting material, the large number of methods to prepare
those compounds can be classified in two main categories: (a)
those that use electrophilic organoselenium and (b) those using
nucleophilic organoselenium species.
Alternatively, transition metal-catalyzed reactions of diaryl
diselenides with aryl halides or organoboron species has become
9
for organic reactions. Because their negligible vapor pres-
1
,2
sure, nonflammability, reasonable thermal stability, ease of
handling, potential for recycling product isolation or catalyst
recycling and, in some cases, rate acceleration and/or selectivity
improvements, they are regarded as environmentally friendly
1,2
9
green solvents. Ionic liquids were used as solvent in a range
10
10a
organic reactions, such as palladium-catalyzed reactions,
10b
10c
olefin metathesis and asymmetric synthesis, and have shown
enhanced reaction rates when compared with conventional
organic solvents.
7
a versatile tool for the synthesis of diaryl selenides. Generally
these transition metal-catalyzed reactions involve particularly
specific ligands, which may increase the cost and limit the
scope of applications. In recent years, electrophilic substitution
Recently, the use of ILs in the synthesis of organochalcogen
7d,8b,11
compounds has been described.
For example, vinylic
+
by ArSe in milder nucleophiles, such as boronic acids and
selenides were obtained by the reaction of phenylselenyl chloride
with vinylboronic acids or vinylboronic esters using [bmim][BF
esters, aryl siloxanes and aryl stannanes emerged as a good
strategy to synthesize diorganyl selenides. For example, Ranu
and co-workers described the use of alumina-supported copper
4
]
8
as solvent and the products were isolated in good yields and
8b
stereospecifity. However, to the best of our knowledge, no reac-
tions using aryl boronic acids or potassium aryltrifluoroborates
as substrate in these reactions have been described so far.
a
Laborat o´ rio de S ´ı ntese Org aˆ nica Limpa – LASOL, Universidade
Federal de Pelotas – UFPel, P.O. Box 354, 96010-900, Pelotas-RS,
Brazil. E-mail: diego.alves@ufpel.edu.br, lenardao@ufpel.edu.br;
Tel: +55 (53) 3275-7533
Results and discussion
b
Universidade de S a˜ o Paulo – USP, S a˜ o Paulo-SP, Brazil
In this sense and due to our interest on green protocols correlated
to the organochalcogen chemistry, we describe here the use
†
1
Electronic supplementary information (ESI) available. See DOI:
0.1039/c1gc15725f
12
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of imidazolium ionic liquids [bmim]BF
the synthesis of diaryl selenides by electrophilic substitution
in arylboron reagents with arylselenium halides (Cl and Br)
4
and [bmim]PF
6
in
7). The formation of the product was easily observed by the
change of the reaction color from dark orange to white (Fig. 1,
a → c).
(
Scheme 1).
Scheme 1 General scheme of reaction.
We initially focused our attention on the optimization of
the reaction conditions for the synthesis of 4-methoxyphenyl-
phenyl selenide 3a starting from electrophilic selenium species
and nucleophilic boron reagents in imidazolium ionic liquids
Fig. 1 Progress of the reaction between 1a and 2a in [bmim][PF ]: (a):
beginning of the reaction; (b): during the reaction (1 h); (c): at the end
of the reaction (2 h).
6
(
Table 1). Firstly, phenylselenium chloride 1a (0.3 mmol) was
reacted with 4-methoxyphenylboronic acid 2a (0.3 mmol) in
bmim][BF ] (0.6 mL) at room temperature under nitrogen
In order to demonstrate the efficiency of this protocol, we
explored the generality of our methodology by reacting other
arylboronic acids 2b–k with phenylselenium chloride 1a (Table
[
4
atmosphere. Under these conditions, the desired product 3a was
obtained in 86% (Table 1; entry 1). Aiming to improve the yield of
reaction, a variety of electrophilic selenium species were tested,
but no enhancement in yield was observed (Table 1; entry 1 vs.
2
). The results disclosed in Table 2 reveal that the reaction
worked well with a range of substituted arylboronic acids,
affording excellent yields of the desired diarylselenides. In a
general way, the reactions are little sensitive to the electronic
effect of the aromatic ring in the arylboronic acid. For example,
arylboronic acids containing electron-donating group (EDG) at
the aromatic ring gave a slightly higher yield than those bearing
electron-withdrawing group (EWG) and electron-neutral one
2
–4).
We observed that the nature of the ionic liquid was important
for the reaction success (Table 1; entries 1, 5–7). Phenylselenium
chloride 1a and arylboronic acid 2a was reacted with different
imidazolium ionic liquids, such as, [bmim][BF
4
], [bmmim][BF
], and to our satisfaction, using
], the corresponding product 3a was obtained in 95%
4
],
(Table 2, entries 1–4 vs. 5–10).
[
[
bmim][NTf
bmim][PF
2
] and [bmim][PF
6
When the reaction was performed with 2-naphthylboronic
6
acid 2k, the respective product 3k was obtained in high yield
Table 2; entry 11). In addition, the possibility of perform-
yield after 2 h (Table 1; entry 7). A decrease in the yield of product
a was observed when the reaction was performed in open
(
3
13
ing the reaction with other arylselenium chlorides was also
investigated. 4-Methoxyphenylboronic acid 2a was efficiently
reacted with a range of arylselenium chlorides containing
EDG and EWG at the aromatic ring, affording the respective
diarylselenides 3l–p in high yields (Table 2; entries 12–15).
atmosphere (Table 1; entry 8). When the reaction was carried
out using diphenyl diselenide instead of phenylselenium chloride
1a, no product 3a was obtained and the diphenyl diselenide was
recovered quantitatively (Table 1; entry 9).
In an optimized reaction, phenylselenium chloride 1a
13b
2
-Pyridylselenium chloride 1g was efficiently reacted with
(
0.3 mmol) was dissolved in [bmim][PF ] (0.6 mL) and reacted
6
arylboronic acid 2a giving the product 3q in good yield (Table
with 4-methoxyphenylboronic acid 2a (0.3 mmol) at room
temperature under nitrogen atmosphere during 2 h, yielding
2
; entry 16).
These reactions were also performed under focused microwave
4
-methoxyphenyl-phenylselenide 3a in 95% yield (Table 1; entry
irradiation. High levels of product formation were observed
in these experiments, and the best result was achieved after
irradiation at 50 C for 15 min, giving the desired diaryl selenides
a
Table 1 Reaction conditions optimization using arylboronic acid 2a
◦
in excellent yields (Table 2; entries 1, 3, 5–6, 10–11).
Furthermore, a study regarding the recovering and reusing
of the ionic liquid was also performed. After the reaction of
phenylselenium chloride 1a with 4-methoxyphenylboronic acid
Entry
X
Ionic liquid
Yield of 3a (%)
2
a in [bmim][PF
diethyl ether. The inferior, ionic liquid phase was separated
and dried under vacuum. The recovered [bmim][PF ] was used
6
] was complete, the product was extracted with
1
2
3
4
5
6
7
8
9
Cl
Br
Suc
Phthal
Cl
Cl
Cl
Cl
SePh
[bmim][BF
[bmim][BF
[bmim][BF
[bmim][BF
[bmmim][BF
[bmim][NTf
4
4
4
4
]
]
]
]
86
54
42
84
73
70
95
82
—
6
b
directly in the next cycle, maintaining its good level of efficiency
even after being reused four times (Fig. 2). Diarylselenide 3a was
obtained in 95%, 94%, 93%, 93%, and 92% yields after successive
cycles.
Additionally, the possibility of the reaction of electrophilic
selenium species with potassium aryltrifluoroborates in ionic
liquid was investigated. Thus, under our optimized reaction
conditions, phenylselenium chloride 1a (0.3 mmol) was reacted
with potassium 4-methoxyphenyltrifluoroborate 4a (0.3 mmol)
4
]
2
]
[bmim][PF
[bmim][PF
[bmim][PF
6
6
6
]
]
]
c
a
Reactions performed in the presence of selenium electrophile
(
0.3 mmol), arylboronic acid 2a (0.3 mmol) and ionic liquid (0.6 mL) at
b
room temperature under nitrogen atmosphere. 1.2 mL of [bmim][BF
4
]
c
was used. Reaction was performed in open atmosphere.
2
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a
Table 2 Scope and generality in the synthesis of diaryl selenides 3a–q using arylselenium chlorides 1a–g and arylboronic acids 2a–k
1
b
Entry
1
ArSeCl
Ar
Time (h)
2
Product
Yield (%)
95 (95)
2
1a
3
94
3
4
1a
1a
2
4
93 (94)
92
5
6
7
1a
1a
1a
4
6
6
89 (91)
86 (89)
85
8
9
1a
1a
6
6
92
90
1
1
0
1
1a
1a
4
5
75 (82)
91 (91)
1
1
2
3
4
4
91
86
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Table 2 (Contd.)
1
b
Entry
ArSeCl
Ar
Time (h)
4
Product
Yield (%)
1
1
1
4
5
6
89
96
84
3
3
1
7
3
89
a
Reactions performed in the presence of arylselenium chloride 1a–g (0.3 mmol), arylboronic acid 2a–k (0.3 mmol) in [bmim][PF
6
◦
] (0.6 mL) at room
b
temperature under nitrogen atmosphere. Yields in parenthesis correspond to reactions performed in a microwave reactor at 50 C for 15 min.
Table 3 Reaction conditions optimization using aryltrifluoroborate
a
4
a
Entry
X
Ionic liquid
Yield of 3a (%)
1
2
3
4
5
6
7
8
Cl
Br
Suc
Phthal
Br
Br
Br
Br
[bmim][PF
[bmim][PF
[bmim][PF
[bmim][PF
[bmim][BF
[bmmim][BF
[bmim][NTf
6
6
6
6
]
]
]
]
71
75
69
73
88
65
54
79
b
4
]
4
]
Fig. 2 Reuse of [bmim][PF ] in the synthesis of 3a.
6
2
]
c
4
[bmim][BF ]
a
Reactions performed in the presence of selenium electrophile
in [bmim][PF
6
] (0.6 mL) at room temperature and the product 3a
(0.3 mmol), potassium aryltrifluoroborate 4a (0.3 mmol) and ionic liquid
b
(
0.6 mL) at room temperature under nitrogen atmosphere. 1.2 mL of
was obtained in 71% isolated product yield (Table 3, entry 1). In
view of this satisfactory result, different electrophilic selenium
species and ionic liquids were tested aiming to increase the yield
of product 3a (Table 3).
c
[
6
bmim][PF ] was used. Reaction was performed in open atmosphere.
When the reaction was performed using phenylselenium
bromide 1i, an increase in the product yield was observed (Table
atmosphere, product 3a was formed in reduced yield (Table 3;
entry 8).
3
(
[
; entry 2). To our satisfaction, using phenylselenium bromide 1i
0.3 mmol), potassium 4-methoxyphenyltrifluoroborate 4a and
bmim][BF ] (0.6 mL) instead [bmim][PF ], the reaction proceeds
The scope of the reaction regarding the use of different
potassium aryltrifluoroborates was examined and excellent
results were obtained (Table 4). Diaryl selenides containing
both electron-donating (entries 1–4) and electron-withdrawing
groups (entries 6–10), were obtained in comparable yields, except
4
6
smoothly and 4-methoxyphenyl-phenylselenide 3a was obtained
in 88% yield after stirring for 3 h (Table 3; entry 5). Using
other ionic liquids, such as, [bmmim][BF
4
] and [bmim][NTf
2
],
3j (EWG = CF ) which was obtained in 73% yield (entry
3
a decrease in the yields are observed (Table 3; entries 6–7).
When the reaction of phenylselenium bromide 1i with potassium
10). Potassium naphthyltrifluoroborate 4k reacts efficiently with
phenylselenium bromide 1i furnishing product 3k in good yield
(Table 4; entry 11).
aryltrifluoroborate 4a in [bmim][BF
4
] was carried out in open
2
934 | Green Chem., 2011, 13, 2931–2938
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a
Table 4 Synthesis of diaryl selenides 3a–k using phenylselenium bromide 1i and aryltrifluoroborates 4a–k
1
Entry
1
Ar
Product
Yield (%)
88
2
85
3
4
86
86
5
6
7
85
84
81
8
9
86
82
1
1
0
1
73
84
a
Reactions performed in the presence of phenylselenium bromide 1i (0.3 mmol), potassium aryltrifluoroborate 4a–k (0.3 mmol) in [bmim][BF
4
]
(
0.6 mL) at room temperature under nitrogen atmosphere for 3 h.
Conclusions
very good results using both, arylboronic acids or potassium
aryltrifluoroborates as starting nucleophiles. Another benefit
of the described procedure is not being necessary the use
neither of metal nor catalyst, another green facet of this new
protocol is the recyclability of the solvent without any pre-
treatment.
In conclusion, imidazolium ionic liquids [bmim]BF
4
and
[
bmim]PF are very efficient to promote the selective synthesis
6
of unsymmetrical diaryl selenides in high yields under mild
conditions. By changing the anion in the ILs is possible achieve
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1
4
1
Experimental
4-Chlorophenyl-phenyl-selenide (3f) . H NMR (CDCl
3
,
4
7
1
1
1
00 MHz): d 7.46–7.44 (m, 2H); 7.36 (d, J = 8.0 Hz, 2H);
.28–7.26 (m, 3H); 7.21 (d, J = 8.0 Hz, 2H). C NMR (CDCl
00 MHz); d (ppm): 134.1, 133.5, 133.1, 130.6, 129.5, 129.4,
27.6. MS (relative intensity) m/z: 270 (15), 268 (36), 188 (100),
52 (27), 77 (22), 51 (18).
General
13
3
The reactions were monitored by TLC carried out on Merck
silica gel (60 F254) by using UV light as visualizing agent and
5
% vanillin in 10% H
spectra were recorded with Bruker DPX 200 and DPX 400 (200
and 400 MHz) instrument using CDCl as solvent and calibrated
using tetramethylsilane as internal standard. Chemical shifts are
2
SO
4
and heat as developing agents. NMR
14
1
2
-Chlorophenyl-phenyl-selenide (3g) . H NMR (CDCl
3
,
3
2
(
1
1
2
00 MHz): d 7.65–7.58 (m, 2H); 7.41–7.23 (m, 4H); 7.15–6.98
m, 2H), 6.91 (dd, J = 7.6, 1.9 Hz, 1H). C NMR (CDCl
00 MHz); d (ppm): 135.9, 133.9, 131.6, 131.0, 129.7, 129.4,
28.7, 128.2, 127.4, 127.3. MS (relative intensity) m/z: 270 (19),
13
3
1
reported in d (ppm) relative to (CH
3
)
4
Si for H and CDCl
3
for
1
3
C NMR. Coupling constants (J) are reported in Hertz. Mass
spectra (MS) were measured on a Shimadzu GCMS-QP2010
mass spectrometer. Microwave reactions were conducted using
a CEM Discover, mode operating systems working at 2.45 GHz,
with a power programmable from 1 to 300 W.
68 (41), 188 (100), 152 (32), 77 (19), 51 (19).
1
4
1
4-Bromophenyl-phenyl-selenide (3h) . H NMR (CDCl
3
,
400 MHz): d 7.46–7.44 (m, 2H); 7.34 (d, J = 8.4 Hz, 2H); 7.28–
.25 (m, 5H). C NMR (CDCl 100 MHz); d (ppm): 134.1,
1
3
7
3
General procedure for the reaction of electrophilic selenium
species with nucleophilic boron reagents
133.2, 133.0, 130.4, 130.3, 129.4, 127.6, 121.41. MS (relative
intensity) m/z: 314 (68), 312 (86), 234 (84), 232 (99), 152 (100),
1
16 (27), 77 (58), 51 (41).
In a Schlenk tube under nitrogen atmosphere containing ionic
1
5
1
liquid ([bmim][PF
boron reagent [ArB(OH)
sponding arylselenium halide (ArSeCl or ArSeBr) (0.3 mmol)
was added in one portion. The reaction mixture was allowed
to stir at room temperature for the time indicated in Table
6
] or [bmim][BF
4
]) (0.6 mL) and nucleophilic
K] (0.3 mmol), the corre-
2-Bromophenyl-phenyl-selenide (3i) . H NMR (CDCl3,
2
or ArBF
3
200 MHz): d 7.66–7.62 (m, 2 H), 7.52–7.38 (m, 4 H), 7.07–
7.00 (m, 2 H), 6.88–6.83 (m, 1 H). C NMR (CDCl 50 MHz);
d (ppm): 136.4, 136.2, 132.7, 130.4, 129.8, 128.9, 128.4, 127.8,
127.3, 123.4. MS (relative intensity) m/z: 312 (61), 232 (58), 207
1
3
3
2
and 4. After the reaction was complete, the products were
(27), 156 (22), 152 (100), 77 (50).
extracted into diethyl ether (3 ¥ 5 mL), dried over MgSO , and
4
1
6
1
3
-(Trifluoromethyl)phenyl-phenyl-selenide (3j) . H NMR
concentrated under vacuum. The residue was purified by column
chromatography on silica gel using ethyl acetate/hexanes as the
eluent.
(
7
1
(
CDCl , 400 MHz): d 7.67 (s, 1H); 7.53–7.44 (m, 4H); 7.31–
100 MHz); d (ppm): 135.1,
34.0, 133.2, 131.5 (q, J = 32.2 Hz), 129.6, 129.5, 129.4, 128.4
q, J = 3.8 Hz), 128.2, 123.7 (q, J = 272.8 Hz), 123.6 (q, J = 3.8
Hz). MS (relative intensity) m/z: 302 (55), 222 (100), 153 (16),
7 (35), 51 (24).
3
1
3
.26 (m, 4H). C NMR (CDCl
3
14
1
4
-Methoxyphenyl-phenyl-selenide (3a) . H NMR (CDCl
3
,
4
7
00 MHz): d 7.50 (d, J = 8.8 Hz, 2H); 7.33–7.31 (m, 2H); 7.21–
1
3
.16 (m, 3H); 6.84 (d, J = 8.4 Hz, 2H); 3.79 (s, 3H). C NMR
100 MHz); d (ppm): 159.7, 136.5, 133.2, 130.9, 129.1,
7
(CDCl
3
17
1
1
2
26.4, 119.9, 115.1, 55.2. MS (relative intensity) m/z: 264 (65),
62 (34), 184 (100), 153 (32), 65 (14).
2-Naphthyl-phenyl-selenide (3k) .
H
NMR (CDCl ,
200 MHz): d 7.98–7.97 (m, 1 H), 7.80–7.69 (m, 3 H), 7.53–7.43
m, 5 H), 7.27–7.24 (m, 3 H). C NMR (50 MHz, CDCl
ppm): 133.9, 132.8, 132.3, 132.0, 131.2, 130.4, 129.3, 128.7,
28.4, 127.7, 127.4, 127.3, 126.5, 126.2. MS (relative intensity)
m/z: 284 (24), 204 (100), 126 (11), 115 (19), 77 (11).
3
1
3
(
(
1
3
); d
14
1
2
-Methoxyphenyl-phenyl-selenide (3b) . H NMR (CDCl
3
,
2
00 MHz): d 7.61–7.56 (m, 2 H), 7.35–7.31 (m, 3 H), 7.24–7.14
1
3
(
m, 1 H), 6.97–7.74 (m, 3 H), 3.88 (s, 3 H). C NMR (100 MHz,
CDCl ); d (ppm): 156.9, 135.2, 131.2, 129.4, 128.6, 127.9, 127.8,
22.0, 121.6, 110.6, 55.9. MS (relative intensity) m/z: 264 (65),
62 (33), 184 (100), 169 (40), 141 (33), 77 (32).
3
14
1
1
2
4-Tolyl-4-methoxylphenyl-selenide (3l) . H NMR (CDCl3,
400 MHz): d 7.43 (d, J = 8.8 Hz, 2H); 7.26 (d, J = 8.0 Hz, 2H);
7.00 (d, J = 8.0 Hz, 2H); 6.79 (d, J = 8.8 Hz, 2H); 3.72 (s, 3H);
.25 (s, 3H). C NMR (CDCl 100 MHz); d (ppm): 159.4, 136.5,
135.6, 131.7, 129.9, 128.8, 120.8, 114.9, 55.1, 20.9. MS (relative
14
1
4
-Tolyl-phenyl-selenide (3c) . H NMR (CDCl
3
, 400 MHz):
1
3
2
3
d 7.38–7.32 (m, 4H); 7.23–7.16 (m, 3H); 7.04 (d, J = 8.5 Hz, 2H);
1
3
2
.33 (s, 3H). C NMR (CDCl
3
100 MHz); d (ppm): 137.6, 133.8,
intensity) m/z: 278 (65), 198 (100), 183 (43), 170 (33), 91 (32),
1
32.0, 130.1, 129.1, 126.8, 21.1. MS (relative intensity) m/z: 248
6
5 (22).
(
70), 246 (39), 168 (100), 153 (25), 91 (63), 65 (30).
1
4
1
1
4
1
2-Tolyl-4-methoxylphenyl-selenide
(3m) .
H
NMR
2
-Tolyl-phenyl-selenide (3d) . H NMR (CDCl
3
, 400 MHz):
(
CDCl
3
, 400 MHz): d 7.44 (d, J = 8.8 Hz, 2H), 7.14–7.06 (m,
3H), 6.99–6.95 (m, 1H), 6.83 (d, J = 8.8 Hz, 2H), 3.75 (s, 3H),
100 MHz); d (ppm): 159.7,
37.8, 136.5, 133.8, 130.7, 129.9, 126.5, 119.2, 115.2, 55.2, 21.8.
MS (relative intensity) m/z: 278 (71), 198 (100), 183 (37), 170
30), 91 (26), 65 (24).
d 7.40–7.38 (m, 2H); 7.35–7.32 (m, 1H); 7.27–7.17 (m, 5H);
.08–7.04 (m, 1H); 2.40 (s, 3H). C NMR (CDCl
d (ppm): 139.8, 133.6, 132.7, 131.7, 130.7, 130.2, 129.3, 127.7,
27.1, 126.7, 22.3. MS (relative intensity) m/z: 248 (72), 246 (37),
1
3
7
3
100 MHz);
1
3
2
1
.36 (s, 3H). C NMR (CDCl
3
1
1
68 (100), 153 (20), 91 (57), 65 (32).
(
14
1
Diphenyl-selenide (3e) . H NMR (CDCl
3
, 400 MHz): d
.46–7.44 (m, 4H); 7.24–7.21 (m, 6H). C NMR (CDCl
00 MHz); d (ppm): 132.9, 131.1, 129.3, 127.2. MS (relative
1
3
18
1
7
1
3
Bis-4-methoxylphenyl-selenide (3n) . H NMR (CDCl
400 MHz): d 7.26 (d, J = 8.9 Hz, 4H), 6.65 (d, J = 8.9 Hz,
3
,
1
3
intensity) m/z: 234 (30), 154 (100), 77 (20), 51 (17).
2H), 3.59 (s, 6H). C NMR (CDCl
3
100 MHz); d (ppm): 159.1,
2
936 | Green Chem., 2011, 13, 2931–2938
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1
2
34.4, 121.9, 114.8, 55.1. MS (relative intensity) m/z: 294 (71),
14 (100), 186 (42), 65 (17).
Notes and references
1
(a) G. Perin, E. J. Lenard a˜ o, R. G. Jacob and R. B. Panatieri, Chem.
1
4
1
Rev., 2009, 109, 1277; (b) D. M. Freudendahl, S. A. Shahzad and T.
T. Wirth, Eur. J. Org. Chem., 2009, 1649; (c) D. M. Freudendahl, S.
Santoro, S. A. Shahzad, C. Santi and T. Wirth, Angew. Chem., Int.
Ed., 2009, 48, 8409; (d) A. L. Braga, D. S. L u¨ dtke and F. Vargas,
Curr. Org. Chem., 2006, 10, 1921.
(a) T. Wirth, Organoselenium Chemistry, in Topics in Current
Chemistry, Springer-Verlag, Heidelberg, 2000, p. 208; (b) C. Paulmier,
Selenium Reagents and Intermediates in Organic Synthesis, in Or-
ganic Chemistry Series 4, ed. J. E. Baldwin, Pergamon Press, Oxford,
4
-Chlorophenyl-4-methoxylphenyl-selenide (3o) . H NMR
CDCl , 400 MHz): d 7.47 (d, J = 8.8 Hz, 2H); 7.21 (d, J =
.8 Hz, 2H); 7.14 (d, J = 8.8 Hz, 2H); 6.83 (d, J = 8.8 Hz,
(
3
8
2
1
1
3
H), 3.77 (s, 3H). C NMR (CDCl
3
100 MHz); d (ppm): 159.9,
36.6, 132.4, 132.0, 131.5, 129.1, 119.4, 115.2, 55.2. MS (relative
intensity) m/z: 298 (35), 296 (17), 218 (100), 203 (40), 175 (27),
3 (12).
2
6
1
986; (c) D. Liotta, Organoselenium Chemistry, Wiley, NewYork,
1
1
,2,3-(trimethyl)phenyl-4-methoxylphenyl-selenide (3p).
NMR (CDCl , 400 MHz): d 6.95 (d, J = 8.8 Hz, 2H), 6.83
s, 2H), 6.59 (d, J = 8.8 Hz, 2H), 3.58 (s, 3H), 2.33 (s, 6H), 2.16
H
1987; (d) F. A. Devillanova, Handbook Of Chalcogen Chemistry: New
Perspectives in S, Se and Te, Royal Society of Chemistry, Cambridge,
3
2
006.
(
(
3
(a) H. S. Kim, Y. J. Kim, H. Lee, K. Y. Park, C. Lee and C. S. Chin,
Angew. Chem., Int. Ed., 2002, 41, 4300; (b) E. J. Lenard a˜ o, J. O. Feij o´ ,
S. Thurow, G. Perin, R. G. Jacob and C. C. Silveira, Tetrahedron Lett.,
1
3
s, 3H). C NMR (CDCl
38.6, 130.6, 128.7, 127.8, 123.1, 114.8, 55.1, 24.2, 20.9. MS
relative intensity) m/z: 306 (100), 226 (54), 211 (22), 197 (78),
83 (18), 119 (25), 105 (12), 91 (40), 77 (25), 63 (8). HRMS calcd
18OSe: 306.0523. Found: 306.0528.
3
100 MHz); d (ppm): 158.0, 143.2,
1
(
1
2
009, 50, 5215; (c) E. J. Lenard a˜ o, E. L. Borges, S. R. Mendes, G.
Perin and R. G. Jacob, Tetrahedron Lett., 2008, 49, 1919; (d) E. J.
Lenard a˜ o, S. R. Mendes, P. C. Ferreira, G. Perin, C. C. Silveira and
R. G. Jacob, Tetrahedron Lett., 2006, 47, 7439; (e) S. Thurow, V. A.
Pereira, D. M. Martinez, D. Alves, G. Perin, R. G. Jacob and E. J.
Lenard a˜ o, Tetrahedron Lett., 2011, 52, 640; (f) E. E. Alberto, L. L.
Rossato, S. H. Alves, D. Alves and A. L. Braga, Org. Biomol. Chem.,
for C16
H
1
2
-Pyridyl-4-methoxylphenyl-selenide (3q).
H
NMR
(
CDCl
3
, 200 MHz): d 8.41 (ddd, J = 4.9, 1.9, 0.8 Hz, 1H);
.63 (d, J = 8.9 Hz, 2H); 7.36 (ddd, J = 7.5, 4.9, 1.9 Hz, 1H);
.01–6.88 (m, 4H), 3.83 (s, 3H). C NMR (CDCl 50 MHz);
d (ppm): 160.3, 159.8, 149.6, 138.2, 136.5, 123.3, 120.0, 117.6,
15.3, 55.2. MS (relative intensity) m/z: 265 (68), 264 (100), 262
63), 249 (21), 185 (25), 142 (15), 78 (59), 51 (32). HRMS calcd
11NOSe: 265.0006. Found: 265.0011.
2
011, 9, 1001.
7
7
4
5
(a) A. L. Braga, D. S. Ludtke, F. Vargas and R. C. Braga, Synlett,
2006, 1453; (b) A. L. Braga, F. Vargas, J. A. Sehnem and R. C. Braga,
J. Org. Chem., 2005, 70, 9021; (c) A. L. Braga, M. W. Paix a˜ o, D. S.
Ludtke, C. C. Silveira and O. E. D. Rodrigues, Org. Lett., 2003, 5,
13
3
1
(
2
1
635; (d) A. L. Braga, M. W. Paix a˜ o and G. Marin, Synlett, 2005,
975; (e) A. L. Braga, D. S. Ludtke, J. A. Sehnem and E. E. Alberto,
for C12
H
Tetrahedron, 2005, 61, 11664; (f) A. L. Braga, O. E. D. Rodrigues, M.
W. P a i x a˜ o, H. R. Appelt, C. C. Silveira and D. P. Bottega, Synthesis,
2
002, 2338.
General procedure to microwave reactions of phenylselenium
chloride 1a with arylboronic acids in [bmim][PF
(a) D. S. Rampon, F. S. Rodembusch, J. M. F. M. Schneider, I. H.
Bechtold, P. F. B. Gon c¸ alves, A. Merlo and P. H. Schneider, J. Mater.
Chem., 2010, 20, 715; (b) I. Samb, J. Bell, P. Y. Toullec, V. Michelet
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Tang, Y. Xing, P. Li, N. Zhang, F. Yu and G. Yang, J. Am. Chem.
Soc., 2007, 129, 11666.
6
]
In a 10 mL glass vial, under nitrogen atmosphere, equipped
with a small magnetic stirring bar, containing the appropriate
arylboronic acid (0.3 mmol) and [bmim][PF ] (0.6 mL) was
added PhSeCl 1a (0.3 mmol). The mixture was then irradiated
in a focused microwaves reactor (CEM Explorer) at 50 C, using
an irradiation power of 50 W. After stirring for 10 min, the
products were extracted into diethyl ether (3¥ 5 mL), dried
, and concentrated under vacuum. The residue was
purified by column chromatography on silica gel using ethyl
acetate/hexanes as the eluent.
6
6
7
(a) G. Mugesh, W. W. du Mont and H. Sies, Chem. Rev., 2001, 101,
2125; (b) C. W. Nogueira, G. Zeni and J. B. T. Rocha, Chem. Rev.,
◦
2
004, 104, 6255.
(a) I. P. Beletskaya and V. P. Ananikov, Chem. Rev., 2011, 111, 1596;
b) V. P. Ananikov, S. S. Zalesskiy and I. P. Beletskaya, Curr. Org.
(
over MgSO
4
Synth., 2011, 8, 2; (c) V. P. Reddy, A. V. Kumar, K. Swapna and
K. R. Rao, Org. Lett., 2009, 11, 951; (d) D. Singh, E. E. Alberto,
O. E. D. Rodrigues and A. L. Braga, Green Chem., 2009, 11, 1521;
(
e) D. Alves, C. G. Santos, M. W. Paix a˜ o, L. C. Soares, D. Souza,
O. E. D. Rodrigues and A. L. Braga, Tetrahedron Lett., 2009, 50,
Recycle of [bmim][PF
a with arylboronic acid 2a
6
] in the reaction of phenylselenium chloride
6635.
8
9
(a) S. Bhadra, A. Saha and B. C. Ranu, J. Org. Chem., 2010, 75, 4864;
1
(
3
b) G. W. Kabalka and B. Venkataiah, Tetrahedron Lett., 2002, 43,
703.
In a Schlenk tube under nitrogen atmosphere containing ionic
liquid [bmim][PF ] (0.6 mL) and 4-methoxyphenylboronic acid
a (0.3 mmol), phenylselenium chloride 1a (0.3 mmol) was added
in one portion. The reaction mixture was allowed to stir at
room temperature for 2 h. After the reaction was complete,
the products were extracted into diethyl ether (3¥ 5 mL), dried
(a) P. Wasserscheid and P. Welton, Ionic Liquids in Synthesis, Wiley-
VCH, Weinheim, 2003; (b) T. Welton, Chem. Rev., 1999, 99, 2071;
(c) J. Dupont, R. F. Souza and P. A. Z. Suarez, Chem. Rev., 2002,
6
2
1
02, 3667; (d) F. Rantwijk and R. A. Sheldon, Chem. Rev., 2007, 107,
757; (e) M. A. P. Martins, C. P. Frizzo, D. N. Moreira, N. Zanatta
2
and H. G. Bonacorso, Chem. Rev., 2008, 108, 2015; (f) H. Olivier-
Bourbigou, L. Magna and D. Morvan, Appl. Catal., A, 2010, 373,
over MgSO
ionic liquid phase, was separated and dried under vacuum. The
recovered [bmim][PF ] was used directly in the next cycle.
4
, and concentrated under vacuum. The inferior,
1.
1
0 (a) R. Singh, M. Sharma, R. Mamgain and D. S. Rawat, J. Braz.
Chem. Soc., 2008, 19, 357; (b) P. Sledz, M. Mauduit and K. Grela,
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2
004, 29, 3; (e) J. Muzart, Adv. Synth. Catal., 2006, 348, 275; (f) M.
Acknowledgements
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Binnemans, Chem. Rev., 2007, 107, 2592; (h) X. Han and D. W.
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The authors are grateful to FAPERGS (FAPERGS/PRONEX
0/0005-1 and 10/0027-4), CAPES, FINEP and CNPq for the
1
financial support.
This journal is © The Royal Society of Chemistry 2011
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1
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2
938 | Green Chem., 2011, 13, 2931–2938
This journal is © The Royal Society of Chemistry 2011