Solvent-controlled halo-selective selenylation of aryl halides catalyzed by Cu(II) supported on Al2O3. A general protocol for the synthesis of unsymmetrical organo mono- and bis-selenides

Article abstract of DOI:10.1021/jo401062k

Alumina-supported Cu(II) efficiently catalyzes selenylation of aryl iodides and aryl bromides by diaryl, dialkyl, and diheteroaryl diselenides in water and PEG-600, respectively, leading to a general route toward synthesis of unsymmetrical diaryl, aryl-alkyl, aryl-heteroaryl, and diheteroaryl selenides. A sequential reaction of bromoiodobenzene with one diaryl/diheteroaryl/dialkyl diselenide in water and another diaryl/diheteroaryl/dialkyl diselenide in PEG-600 in the second step produces unsymmetrical diaryl, diheteroaryl, or aryl-alkyl bis-selanyl benzene. A library of functionalized organo mono- and bis-selenides, including a potent biologically active molecule and a couple of analogues of bioactive selenides, were obtained in high yields by this protocol. The reactions are chemoselective and high yielding. The Cu-Al₂O ₃ catalyst is recycled for seven runs without any appreciable loss of activity.

Full text of DOI:10.1021/jo401062k

Article
pubs.acs.org/joc
Solvent-Controlled Halo-Selective Selenylation of Aryl Halides
Catalyzed by Cu(II) Supported on Al2O3. A General Protocol for the
Synthesis of Unsymmetrical Organo Mono- and Bis-Selenides
Tanmay Chatterjee and Brindaban C. Ranu*
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
S
* Supporting Information
ABSTRACT: Alumina-supported Cu(II) efficiently catalyzes sele-
nylation of aryl iodides and aryl bromides by diaryl, dialkyl, and
diheteroaryl diselenides in water and PEG-600, respectively, leading
to a general route toward synthesis of unsymmetrical diaryl, aryl−
alkyl, aryl−heteroaryl, and diheteroaryl selenides. A sequential
reaction of bromoiodobenzene with one diaryl/diheteroaryl/dialkyl
diselenide in water and another diaryl/diheteroaryl/dialkyl dis-
elenide in PEG-600 in the second step produces unsymmetrical
diaryl, diheteroaryl, or aryl−alkyl bis-selanyl benzene. A library of
functionalized organo mono- and bis-selenides, including a potent
biologically active molecule and a couple of analogues of bioactive
selenides, were obtained in high yields by this protocol. The
reactions are chemoselective and high yielding. The Cu-Al2O3
catalyst is recycled for seven runs without any appreciable loss of activity.
might be of high potential and interest. This prompted us to
develop an efficient and general method that should be
applicable for the synthesis of all types of organoselenides,
including unsymmetrical diaryl/diheteroaryl/aryl−alkyl mono-
and bis-selenides.
We recently reported the synthesis of diaryl/aryl−vinyl
selenides by the Cu nanoparticle catalyzed selenylation of aryl
iodides and vinyl bromides by Ph2Se2,11a CuFe2O4 nanoparticle
catalyzed coupling of organoboronic acids and diphenyl
diselenides,11b microwave-assisted reaction of aryl diazonium
fluoroborate and diselenides,11c and Cu-Al2O3-catalyzed elec-
trophilic substitutions in organoboranes, silanes, and stannanes
by PhSeBr.11d As a part of our continuing activities in this area,
we have observed a unique solvent-controlled selenylation of
aryl iodides in water and aryl bromides in PEG-600 by diaryl
diselenide using our recently developed Cu-Al2O3 catalyst11e
(Scheme 1).
INTRODUCTION
■
The organoselenium compounds are of continued interest
because of their potential biological activities, such as antiviral,
antihypertensive, antioxidant, antimicrobial, and anticancer
properties.1 A few representative molecules, such as com-
pounds 1 (human breast cancer cell growth inhibitor),1c
2
(thioredoxin reductase (TR) and glutathione reductase (GR)
inhibitor),1c 3 (antitumor agent),1d 4 (5-LOX (lipoxygenases)
inhibitor),1e and 5 (retinoic acid receptor (RAR) agonist, 10
times more potent than its sulfur analogue),1f,g are outlined in
Figure 1.They also play an important role in organic synthesis
as useful intermediates2 and catalysts.3 They have important
applications as materials, too.4 Thus, development of efficient
synthetic methods for these compounds is of much significance.
A number of methods have been reported during the past few
years. Transition-metal-catalyzed C−Se bond formation is one
of the most popular practices for the synthesis of organo-
selenides. Several metals, Pd,5 Ni,6 Fe,7 and Cu,8 have been
employed to catalyze the reaction of aryl halides/boronic acids
and selenol/PhSeNa/diphenyl diselenide for the synthesis of
aryl selenides. However, because of the instability and toxicity
of selenol or sodium selenate, the commercially available and
stable diphenyl diselenide is widely used. Although these
methods are quite satisfactory for the routine preparation of
diaryl selenides, the syntheses of unsymmetrical diheteroaryl
selenides and diaryl/diheteroaryl/aryl−alkyl bis-selenides were
not addressed. Morever, many of these procedures involve
hazardous solvents and high temperature. The diheteroaryl
sulfides were reported to be potential drug molecules9 and
useful material.10 Thus, it is likely that the selenide counterparts
RESULTS AND DISCUSSION
■
To standardize the reaction conditions, a series of experiments
were performed with variation of solvent, additive, temperature,
and time for a representative reaction of 4-methoxyphenyl
iodide and diphenyl diselenide in the presence of Cu-Al2O3 (5
mol %) and KOH. The results are summarized in Table 1. A
variety of solvents, including toluene, THF, DMF, NMP,
DMSO, DMC, and H2O, were studied. The best results in
Received: May 15, 2013
Published: June 20, 2013
© 2013 American Chemical Society
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Figure 1. Some biologically active organoselenides.
Scheme 1. Solvent Selective Selenylation of Iodo- and
Bromobenzene
Table 2. Standardization of Reaction Conditions for
Selenylation of Bromobenzene
a
entry
solvent
H2O
temp (°C)
time (h)
yield (%)
b
1
100
110
100
140
140
140
140
140
125
125
125
15
15
15
15
15
15
15
15
15
13
10
Table 1. Standardization of Reaction Conditions for
Selenylation of Iodobenzene
b
2
H2O
3
4
toluene
DMF
74
70
76
76
81
81
81
71
5
NMP
6
DMSO
DMSO
PEG-600
PEG-600
PEG-600
PEG-600
7
a
entry
solvent
additive
temp (°C)
time (h)
yield (%)
10
8
1
toluene
THF
DMF
NMP
DMSO
DMC
H2O
100
65
12
12
12
12
12
12
12
12
12
12
10
8
9
2
10
11
3
110
110
110
90
79
71
77
62
66
84
72
61
84
70
63
a
4
Yields refer to those of isolated pure products using 5 mol % catalyst.
25 mol % TBAB was used.
b
5
6
7
100
100
100
80
was carried out in PEG-600 at 125 °C in the presence of Cu-
Al2O3 and KOH for a certain period time as required for
completion (TLC). Standard workup and purification by
column chromatography provided the pure product.
8
H2O
TBAB
SDS
9
H2O
10
11
12
H2O
TBAB
TBAB
TBAB
TBAB
H2O
100
100
100
Several diversely substituted aryl and heteroaryl iodides
underwent reactions with aryl, heteroaryl, and alkyl diselenides
by this procedure to produce the corresponding diaryl, aryl−
heteroaryl, and aryl−alkyl selenides. The results are summar-
ized in Table 3.
H2O
b
13
H2O
10
a
Yields refer to those of isolated pure products using 5 mol % catalyst
b
loading. 4 mol % catalyst was used.
The reaction is highly chemoselective as Br on the phenyl
ring of aryl iodides remained inert during coupling with
diphenyl diselenide (Table 3, entries 12−17). Several
functionalities, such as OMe, NH2, CF3, CHO, COMe, NO2,
and CO2Et, were compatible under the reaction conditions. A
sterically hindered molecule, 2,6-dimethoxyiodobenzene,
underwent facile selenylation by this procedure (Table 3,
entry 3). The heteroaryl iodides containing 5-acetyl-2-
thiophenyl and 3-pyridinyl reacted with diphenyl diselenide
without any difficulty to provide the corresponding heteroaryl−
aryl selenides (Table 3, entries 10 and 11).
A wide range of substituted aryl- and heteroaryl bromides
reacted with aryl selenides by the procedure described above
(condition B) to furnish the corresponding diaryl and
heteroaryl−aryl selenides. The results are reported in Table 4.
The naphthyl bromides were equally reactive as phenyl
bromides (Table 4, entries 8 and 9) to provide the
corresponding selenides by this reaction. These compounds
terms of yield and time were achieved by carrying out the
reaction of 4-methoxyphenyl iodide in water at 100 °C in the
presence of TBAB for 10 h (Table 1, entry 11). Interestingly, 4-
methoxyphenyl bromide remained inert under these conditions.
However, optimization of the reaction conditions (Table 2)
revealed that selenylation of aryl bromide was successful in
PEG-600 at 125 °C for 13 h (Table 2, entry 10). DMF, NMP,
DMSO, and DMC are also quite effective for both the
reactions. However, H2O and PEG-600 were chosen for
reaction of aryl iodides and bromides, respectively, being more
efficient, cost-effective, and environmentally friendly. It is
worthwhile to note that two units of PhSe of Ph2Se2 are
consumed in this reaction.
Thus, in a typical reaction procedure, a mixture of aryl iodide
(1 mmol) and diaryl diselenide (0.5 mmol) was heated in water
at 100 °C in the presence of Cu-Al2O3, KOH, and TBAB for a
required period of time (TLC). For aryl bromides, the reaction
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Table 3. Cu-Al2O3-Catalyzed Selenylation of Aryl Iodides in
Water
Table 4. Cu-Al2O3-Catalyzed Selenylation of Aryl Bromides
in PEG-600
a b
,
ab
,
a
b
Yields refer to those of isolated pure products. 2 equiv (1 mmol) of
Ph2Se2 was used.
quinolinyl and thiazolyl moieties also underwent smooth
reactions (Table 4, entries 10−13). Interestingly, when 1
equiv of diphenyl diselenide was used, 2,5-dibromothiazole
provided one product selectively, keeping the 5-Br unaffected
(Table 4, entry 11). However, use of 2 equiv of diphenyl
diselenide provided the corresponding bis-selenide (Table 4,
entry 12). A potent bioactive molecule 2 (Figure 1), the
inhibitor of thioredoxin reductase (TR) and glutathione
reductase (GR), has been successfully obtained by this reaction
(Table 4, entry 14).8c,12 The aryl chlorides were not very
reactive under these reaction conditions. The yields of products
a
b
Yields refer to those of isolated pure products. 2 equiv (1 mmol) of
Ph2Se2 was used.
are of much importance, being analogues of 5-LOX inhibitor 4
(Figure 1). The sterically hindered 2,6-dimethylbromobenzene
reacted cleanly with di-4-methoxyphenyl diselenide (Table 4,
entry 4). Significantly, 1,4-dibromobenzene underwent ex-
clusive monoselenylation on treatment with diphenyl diselenide
(Table 4, entry 7). Several heteroaryl bromides bearing
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vary with the nature of the substituent on the phenyl ring of
aryl chloride.
Table 6. Synthesis of Unsymmetrical Heteroaryl−Heteroaryl
a
Selenides
The electron-withdrawing groups accelerated the reaction to
a great extent, pushing the yields to 54−55% (Table 4, entries 5
and 6), whereas the electron-donating group arrested the
selenylation completely (Table 4, entry 2). The unsubstituted
chlorobenzene, however, underwent the reaction marginally
(Table 4, entry 1).
The selenylation of styrenyl bromides proceeded efficiently
in water in the presence of TBAB by the same procedure as that
for aryl iodides. The results are presented in Table 5. The trans-
Table 5. Cu-Al2O3-Catalyzed Selenylation of Styryl Bromides
a
in Water
a
Yields refer to those of isolated pure products.
The solvent-controlled selective selenylation of iodo- and
bromobenzene prompted us to utilize this property for the
synthesis of unsymmetrical bis-selenides, not addressed earlier.
Thus, 1,4-bromoiodobenzene was reacted with diphenyl
diselenide in water, followed by reaction with dimethyl
diselenide in PEG-600, to produce the corresponding unsym-
metrical bis-selenide with phenyl and methyl units at two ends
(Scheme 2, compound A). Similarly, other bis-selenides, 1-(3-
(phenylselanyl)phenylselanyl)-4-methoxybenzene (Scheme 2,
compound B) and 1-(2-(methylselanyl)phenylselanyl)benzene
(Scheme 2, compound C), were also achieved starting from
1,3-bromoiodo- and 1,2-bromoiodobenzenes. The results are
outlined in Scheme 2. The synthesis of these unsymmetrical
bis-selenides is reported here for the first time and might be of
interest as useful material in analogy to the corresponding bis-
sulfide counterparts.10 Further, an arene bearing two different
heterocyclic units connected via a C−Se bond (Scheme 2,
compound D) is of much significance and may be worthy for
biological screening too. This procedure also provides the
scope for access to functionalized molecules starting with
suitably substituted aryl halides and diselenides.
a
Yields refer to those of isolated pure products.
In general, the reactions are clean and high yielding. The
products were obtained pure by a simple workup and
chromatography. Many of these selenides were not reported
earlier. Several useful functionalities and sensitive heterocyclic
moieties are compatible with this procedure.
For recyclability and reuse of the catalyst, after the reaction
was over, the reaction mixture was filtered to separate the
catalyst. The solid catalyst was then washed with diethyl ether
(5 × 3 mL), water (4 × 3 mL), and acetone (3 × 4 mL). The
solid was then dried at 100 °C for 8 h for further use. The
catalyst was recycled up to a seventh run without appreciable
loss of efficiency for the representative reaction of 4-iodoanisole
and diphenyldiselenide (Figure 2). The copper loading of the
catalyst after the seventh cycle was found to be 0.491 mmol/g
compared to 0.515 mmol/g in the fresh catalyst (as detected by
ICP-MS).
styrenyl bromides furnished trans-selenides (Table 5, entries 1
and 3), whereas cis-styrenyl bromides provided mixture of cis
and trans products with cis as the major constituent (Table 5,
entries 2 and 4), which is not unusual.11a Significantly, the bis-
vinyl bromide, 1,3-bis((E)-2-bromovinyl)benzene on reaction
with 3-pyridinyl diselenide produced only monoselenide even
when excess diselenide was employed (Table 5, entry 5). The
cinnamyl bromide also underwent facile selenylation (Table 5,
entry 6).
The reaction of a heteroaryl bromide with a diheteroaryl
diselenide proceeded well in PEG-600 under the same
conditions as those for aryl bromides. The results are
summarized in Table 6. The reactions of quinolinyl, pyridinyl,
and thiophenyl bromides with dipyridinyl and dithiophenyl
diselenides were performed successfully to provide the
corresponding unsymmetrical diheteroaryl selenides for the
first time. These selenides might be of much interest for
biological activity as the corresponding sulfides are highly
potent.9
To investigate the reaction mechanism, a series of experi-
ments were conducted. The X-ray photoelectron spectroscopic
(XPS) study of the fresh and used catalysts at the Cu 2p level
shows the 2p3/2 lines at 934.7 and 936.4 eV, respectively, with
characteristic shakeup features (Figure 3a,b).13 This clearly
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Scheme 2. Solvent-Controlled Differential Selenylation of Bromoiodobenzenes
On the other hand, the EPR (electron paramagnetic
resonance) spectra of the fresh, intermediate, and the used
copper catalysts were recorded for the solid sample at 77 K
(Figure 4). The g values of the fresh catalyst are g1 = 2.127, g2 =
2.028 and those of the used catalyst are g1 = 2.065, g2 = 2.012,
indicating a tetragonally distorted octahedral geometry for
Cu(II).14 The EPR spectral pattern of the intermediate
complex exhibited the g values as g1 = 2.058, g2 = 2.034, and
g3 = 2.011, which are indicative of an octahedral environment
with a rhombic distortion at the metal center.11d From these
experiments, it is evident that Cu remains in the +2 oxidation
state throughout the reaction cycle. On the other hand, to
check the possibility of a single electron transfer (SET) process
in the reaction pathway, we chose to use 1-(allyloxy)-2-
iodobenzene as a probe in a reaction with diphenyl diselenide
following experimental condition A. If the reaction would
follow the SET mechanistic process or the radical pathway,
then it will end up with the formation of the benzofuran
derivative, 2,3-dihydro-3-((phenylselanyl)methyl)benzofuran E
(Scheme 3).15 However, we did not observe formation of even
Figure 2. Recyclability of the Cu-Al2O3 catalyst.
indicates that Cu is in a +2 oxidation state before and after the
reaction (a slightly higher value of binding energy of Cu2+ in
the used catalyst may be due to the presence of the more
electronegative environment of the copper ions in the
postreaction phase).
Figure 3. XPS of Cu 2p3/2 for (a) fresh catalyst and (b) used catalysts.
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Scheme 4. Plausible Mechanism for Selenylation of Aryl
Halide
CONCLUSION
■
In conclusion, we have developed an efficient protocol for
solvent-controlled halo-selective selenylation of aryl iodides and
bromides by diaryl diselenides in water and PEG-600,
respectively, catalyzed by Cu(II)-Al2O3. A library of unsym-
metrical aryl−aryl, aryl−alkyl, aryl−heteroaryl, and diheteroaryl
mono- and bis-selenides, including a potent bioactive molecule
2, were easily achieved. The significant advantages of this
procedure are simple operation, no need for maintaining an
inert atmosphere and using dry solvents, chemoselectivity, high
yields, scaling up to multigram quantities, no use of ligands,
reaction in an environmentally acceptable medium, easy
accessibility, and recyclability of catalyst. To the best of our
knowledge, such a solvent-controlled selenylation and the
development of an efficient method for the synthesis of
unsymmetrical diheteroaryl selenides and organo bis-selenides
are reported for the first time. We believe that this will find
useful applications in the synthesis of organoselenides.
Figure 4. X-band EPR spectral patterns of Cu2+ in (a) fresh catalyst,
(b) intermediate complex, and (c) used catalyst.
Scheme 3. Selenylation Reaction of 1-(Allyloxy)-2-
iodobenzene to Check the SET Process
EXPERIMENTAL SECTION
■
General. The aryl and heteroaryl diselenides used in this reaction
were prepared following a reported procedure.19 Diphenyl diselenide
and dimethyl diselenide were purchased from a chemical supplier.
HRMS analysis was performed in a Qtof mass analyzer using the ESI
ionization method. Thin-layer chromatography was done using
a trace amount of compound E in the crude reaction mixture
(NMR), and compound F, (2-(allyloxy)phenyl)(phenyl)selane
(characterized satisfactorily by 1H NMR, 13C NMR, and
elemental analysis), was isolated in 93% yield (Scheme 3).
From this experiment, it is not unlikely to conclude that the
reaction is not following the SET mechanistic process, and
hence, Cu-assisted nucleophilic displacement16,17 of aryl halide
by diaryl diselenide is considered (Scheme 4).
We suggest that, first, KSeR′, generated in situ from R′-Se-
Se-R′ and KOH, interacts with the copper catalyst to give an
intermediate complex I giving rise to a rhombic distortion of
the copper(II) coordination geometry. In the next step, RX
combines with intermediate I to form a transient intermediate
II, where R interacts with the Se center, being assisted by the
Cu(II) species. The intermediate II subsequently collapses to
intermediate III with direct carbon selenium bond formation.
Elimination of R-Se-R′ from the coordination sphere of the
copper catalyst led to the formation of the product with the
regeneration of the catalyst. This type of mechanism was
reported earlier too.11e
commercial (MERCK) plates with silica gel 60 F254
.
General Experimental Procedure for the Cross-Coupling of
Aryl Halides and Diaryldiselenides. Representative Procedure
for the Reaction of 4-Iodoanisole and Diphenyldiselenide
(Table 3, Entry 2). A mixture of 4-iodoanisole (234 mg, 1 mmol),
diphenyldiselenide (156 mg, 0.5 mmol), KOH (84 mg, 1.5 mmol),
tetrabutylammonium bromide (TBAB) (80 mg, 0.25 mmol), and
Cu(II)-Al2O3 catalyst (97 mg, 5 mol %) in water (4 mL) was heated
with stirring at 100 °C under air for 10 h (TLC). The reaction mixture
was filtered to separate the solid catalyst, which was used for successive
cycles. The filtrate was extracted with Et2O (4 × 15 mL). The extract
was washed with water and brine and then dried (Na2SO4).
Evaporation of the solvent left the crude product, which was purified
by column chromatography over silica gel (60−120 mesh) (hexane/
diethyl ether 95:5) to afford pure (4-methoxyphenyl)(phenyl)selane
(221 mg, 84%) as a pale yellow liquid: Rf = 0.7 (hexane/diethyl ether
= 9:1); IR (neat) 3064, 2925, 2827, 1577, 1473, 1285 cm−1; 1H NMR
(500 MHz, CDCl3) δ 3.81 (s, 3H), 6.86 (d, J = 7 Hz, 2H), 7.18−7.21
(m, 3H), 7.33 (d, J = 7 Hz, 2H), 7.51 (d, J = 7 Hz, 2H); 13C NMR
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(125 MHz, CDCl3) δ 55.4, 115.3 (2C), 120.1, 126.6, 129.3 (2C),
131.1 (2C), 133.3, 136.6 (2C), 159.9. The spectroscopic data (1H and
13C NMR) are in good agreement with those reported for the
(4-Methoxyphenyl)(2,6-dimethylphenyl)selane (Table 4,
Entry 4): Colorless oil (221 mg, 76%); Rf = 0.7 (hexane/diethyl
ether = 9:1); IR (neat) 3061, 2922, 2831, 1594, 1565, 1481, 1396,
1280, 1136, 1025 cm−1; 1H NMR (500 MHz, CDCl3) δ 2.28 (s, 6H),
3.74 (s, 3H), 6.74 (d, J = 9 Hz, 2H), 7.08 (d, J = 9 Hz, 2H), 7.14 (d, J
= 8 Hz, 2H), 7.18 (d, J = 8 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ
24.6 (2C), 55.4, 115.1 (2C), 123.1, 128.0 (2C), 128.9 (2C), 131.1
(2C), 131.6, 143.5, 158.3; Anal. Calcd for C15H16OSe: C, 61.86; H,
5.54. Found: C, 61.81; H, 5.59.
(2-Methoxynaphthalen-1-yl)(phenyl)selane (Table 4, Entry
9): Pale yellow liquid (263 mg, 84%); Rf = 0.6 (hexane/diethyl ether =
9:1); IR (neat) 3396, 3057, 2924, 2841, 1620, 1591, 1575, 1502, 1475,
1265, 1066 cm−1; 1H NMR (500 MHz, CDCl3) δ 3.94 (s, 3H), 7.1 (d,
J = 7 Hz, 3H), 7.17 (d, J = 7 Hz, 2H), 7.35−7.38 (m, 2H), 7.48 (t, J =
8 Hz, 1H), 7.80 (d, J = 8 Hz, 1H), 7.95 (d, J = 9 Hz, 1H), 8.47 (d, J =
9 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 57.2, 113.6, 124.2, 125.7,
127.7, 127.9, 128.4, 129.0 (2C), 129.4 (2C), 129.8, 132.1, 133.3, 136.5,
136.7, 158.8. Anal. Calcd for C17H14OSe: C, 65.18; H, 4.50. Found: C,
65.15; H, 4.48.
authentic sample.11b This procedure was followed for all the reactions
listed in Table 3.
Representative Procedure for the Reaction of 4-Bromoani-
sole and Diphenyldiselenide (Table 4, Entry 2). The same
procedure as that in the previous experiment was followed in PEG-600
(4 mL), replacing water and in the absence of TBAB, allowing the
reaction to go for 13 h at 125 °C (TLC). Extraction and workup
provided pure (4-methoxyphenyl)(phenyl)selane (213 mg, 81%) as a
pale yellow liquid. This procedure was followed for all of the reactions
listed in Table 4. Although these procedures were described with a 1
mmol scale, 10 mmol scale reactions also provided uniform results.
All of these products listed in Tables 3 and 4 were properly
characterized. The known compounds were identified by comparison
of their spectra with those of authentic samples (see references in
Tables 3−5). The unknown compounds were characterized by their
1
spectroscopic data (IR, H and 13C NMR, and HRMS or elemental
analysis data), which are provided below in order of their entries in the
respective tables.
5-Bromo-2-(phenylselanyl)thiazole (Table 4, Entry 11): Pale
yellow liquid (261 mg, 82%); Rf = 0.6 (hexane/ethyl acetate = 9:1); IR
(neat) 3070, 2923, 2850, 1575, 1475, 1438, 1382, 993 cm−1; 1H NMR
(300 MHz, CDCl3) δ 7.36−7.44 (m, 3H), 7.59 (s, 1H), 7.71 (d, J = 5
Hz, 2H); 13C NMR (75 MHz, CDCl3) δ 110.2, 127.4, 129.7, 130.0
(2C), 135.5 (2C), 145.3, 159.2. HRMS Calcd for C9H6BrNSSe [M +
H]+: 319.8672. Found: 319.8637.
(2,6-Dimethoxyphenyl)(phenyl)selane (Table 3, Entry 3):
Yellow solid (220 mg, 75%); mp 75−77 °C; Rf = 0.55 (hexane/
diethyl ether = 9:1); IR (KBr) 3060, 2921, 2823, 1597, 1562, 1484,
1391, 1276, 1021 cm−1; 1H NMR (500 MHz, CDCl3) δ 3.78 (s, 6H),
6.62 (d, J = 8 Hz, 2H), 7.09−7.15 (m, 3H), 7.24 (d, J = 8 Hz, 2H),
7.34 (t, J = 8 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 56.4 (2C),
104.5 (2C), 125.6 (2C), 128.7 (2C), 129.7 (2C), 131.1, 132.9, 161.0
(2C). HRMS Calcd for C14H14O2Se [M + H]+: 295.0234. Found:
295.0232.
1-(5-(Phenylselanyl)thiophen-2-yl)ethanone (Table 3, Entry
10): Pale yellow liquid (250 mg, 89%); Rf = 0.65 (hexane/diethyl ether
= 9:1); IR (neat) 3055, 2921, 1734, 1575, 1491, 1476, 1350, 1022, 949
cm−1; 1H NMR (500 MHz, CDCl3) δ 2.50 (s, 3H), 7.19 (d, J = 4 Hz,
1H), 7.29−7.30 (m, 3H), 7.50−7.53 (m, 3H); 13C NMR (125 MHz,
CDCl3) δ 26.7, 128.3, 129.7 (2C), 130.7, 132.7 (2C), 132.9, 134.5,
136.8, 148.2, 189.8. Anal. Calcd for C12H10OSSe: C, 51.25; H, 3.58.
Found: C, 51.28; H, 3.54.
2,5-Bis(phenylselanyl)thiazole (Table 4, Entry 12): Yellow
gummy liquid (316 mg, 80%); Rf = 0.6 (hexane/ethyl acetate = 9:1);
1
IR (neat) 3072, 2921, 2865, 1573, 1475, 1425, 1392, 995 cm−1; H
NMR (300 MHz, CDCl3) δ 7.22−7.24 (m, 4H), 7.32−7.34 (m, 2H),
7.37−7.45 (m, 2H), 7.74 (d, J = 5 Hz, 2H), 7.80 (s, 1H); 13C NMR
(75 MHz, CDCl3) δ 121.6, 127.3, 127.5, 129.5 (2C), 129.9, 130.1
(2C), 130.8 (2C), 131.8, 135.9 (2C), 151.5, 165.0. Anal. Calcd for
C15H11NSSe2: C, 45.58; H, 2.81; N, 3.54. Found: C, 45.54; H, 2.85; N,
3.56.
2-(Phenylselanyl)thiazole (Table 4, Entry 13): Pale yellow
liquid (204 mg, 85%); Rf = 0.6 (hexane/ethyl acetate = 9:1); IR (neat)
1
3077, 2938, 2860, 1575, 1473, 1438, 1381, 991 cm−1; H NMR (500
(2-Bromophenyl)(methyl)selane (Table 3, Entry 14): Pale
yellow liquid (230 mg, 92%); Rf = 0.8 (hexane/diethyl ether = 9:1); IR
(neat) 3051, 2925, 1664, 1635, 1575, 1538, 1475, 1456, 1436, 1375,
1014, 744 cm−1; 1H NMR (300 MHz, CDCl3) δ 2.33 (s, 3H), 7.04 (t,
J = 7 Hz, 1H), 7.19- 7.28 (m, 2H), 7.49 (d, J = 8 Hz, 1H); 13C NMR
(75 MHz, CDCl3) δ 7.3, 124.1, 126.7, 127.9, 128.6, 132.7, 135.2. Anal.
Calcd for C7H7BrSe: C, 33.63; H, 2.82. Found: C, 33.66; H, 2.78.
(2-Bromo-5-methylphenyl)(phenyl)selane (Table 3, Entry
15): Yellow liquid (257 mg, 79%); Rf = 0.8 (hexane/diethyl ether =
9:1); IR (neat) 3055, 2918, 1660, 1631, 1575, 1558, 1506, 1474, 1456,
MHz, CDCl3) δ 7.33 (d, J = 4 Hz, 1H), 7.38−7.46 (m, 3H), 7.74 (d, J
= 8 Hz, 2H), 7.78 (d, J = 4 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ
122.2, 128.2, 129.4, 129.9 (2C), 135.2 (2C), 144.1, 157.8. HRMS
Calcd for C9H7NSSe [M + H]+: 241.9531. Found: 241.9537.
(E)-(4-Chlorostyryl)(4-methoxyphenyl)selane (Table 5, Entry
3): Light yellow solid (300 mg, 93%); mp 79−81 °C; Rf = 0.7
(hexane/diethyl ether = 9:1); IR (KBr) 3078, 2908, 2839, 1589, 1570,
1491, 1400, 1286, 1247, 1176, 1026 cm−1; 1H NMR (500 MHz,
CDCl3) δ 3.74 (s, 3H), 6.51 (d, J = 16 Hz, 1H), 6.80 (d, J = 8.5 Hz,
2H), 7.36 (d, J = 16 Hz, 1H), 7.10 (d, J = 8 Hz, 2H), 7.16 (d, J = 8 Hz,
2H) 7.43 (d, J = 8.5 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 55.4,
115.3 (2C), 118.8, 122.5, 127.1 (2C), 128.8 (2C), 131.1, 132.9, 135.8,
136.0 (2C), 160.0. Anal. Calcd for C15H13ClSe: C, 58.56; H, 4.26.
Found: C, 58.51; H, 4.29.
1
1436, 1015, cm−1; H NMR (300 MHz, CDCl3) δ 2.13 (s, 3H), 6.77
(s, 1H), 6.84 (d, J = 8 Hz, 1H), 7.37− 7.41 (m, 4H), 7.60- 7.64 (m,
4H); 13C NMR (75 MHz, CDCl3) δ 21.0, 120.8, 128.7, 128.8, 129.0,
129.9 (2C), 131.7, 132.5, 135.6, 135.8 (2C), 138.0. Anal. Calcd for
C13H11BrSe: C, 47.88; H, 3.40. Found: C, 47.84; H, 3.46.
Mixture of (Z)- and (E)-(4-Chlorostyryl)(4-methoxyphenyl)-
selane (Z:E = 65:35) (Table 5, Entry 4): Pale yellow solid (274 mg,
85%); Rf = 0.7 (hexane/diethyl ether = 9:1); IR (KBr) 3071, 2916,
2839, 1588, 1571, 1491, 1401, 1285, 1147, 1025 cm−1; 1H NMR (500
MHz, CDCl3) δ 3.72 (s, 3H), 3.73 (s, 3H), 6.65 (d, J = 10 Hz, 1H),
6.74−6.81 (m, 5H), 7.16−7.20 (m, 4H), 7.22−7.29 (m, 6H), 7.42−
7.45 (m, 4H); 13C NMR (125 MHz, CDCl3) δ 55.4, 55.5, 100.3,
110.2, 115.2 (2C), 115.5 (2C), 118.1, 121.9, 126.8, 127.1, 128.0, 128.6
(2C), 128.7 (2C), 128.9, 129.6 (2C), 132.3 (2C), 132.9 (2C), 134.5,
135.3 (2C), 135.9, 159.7, 159.8.
3-(3-((E)-2-Bromovinyl)styrylselanyl)pyridine (Table 5, Entry
5): Yellow oil (295 mg, 81%); Rf = 0.45 (hexane/ethyl acetate = 9:1);
IR (neat) 3062, 2925, 2841, 1581, 1563, 1469, 1421, 1271, 1141, 1035
cm−1; 1H NMR (500 MHz, CDCl3) δ 6.80 (d, J = 14 Hz, 1H), 6.96 (d,
J = 15.5 Hz, 1H), 7.07−7.13 (m, 2H), 7.21−7.30 (m, 5H), 7.53 (br s,
1H), 8.03 (d, J = 7.5 Hz, 1H), 8.89 (br s, 1H); 13C NMR (125 MHz,
CDCl3) δ 107.7, 115.9, 124.4, 125.8, 126.0, 126.4 (2C), 129.2, 129.4,
3-(4-Bromo-2-methylphenylselanyl)pyridine (Table 3, Entry
16): Pale yellow liquid (271 mg, 83%); Rf = 0.5 (hexane/ethyl acetate
= 9:1); IR (neat) 3039, 2920, 1724, 1566, 1461, 1404, 1377, 1195,
1029 cm−1; 1H NMR (500 MHz, CDCl3) δ 2.38 (s, 3H), 7.21 (s, 3H),
7.40 (s, 1H), 7.65 (s, 1H), 8.51 (s, 1H), 8.61 (s, 1H); 13C NMR (100
MHz, CDCl3) δ 22.4, 122.6, 124.6, 128.2, 129.3, 130.1, 133.4, 135.7,
140.0, 142.4, 148.3, 152.5. HRMS Calcd for C12H10BrNSe [M + H]+:
327.9232. Found: 327.9233.
3-(4-Bromo-2-methylphenylselanyl)thiophene (Table 3,
Entry 17): Colorless liquid (282 mg, 85%); Rf = 0.7 (hexane/diethyl
ether = 9:1); IR (neat) 3101, 2921, 1599, 1458, 1377, 1346, 1195,
1
1089, 1029, 846, 775 cm−1; H NMR (300 MHz, CDCl3) δ 2.37 (s,
3H), 6.94 (d, J = 8 Hz, 1H), 7.07 (dd, J1 = 5 Hz, J2 = 1 Hz, 1H), 7.12−
7.16 (m, 1H), 7.32 (d, J = 2 Hz, 1H), 7.36−7.39 (m, 1H) 7.41−7.42
(m, 2H); 13C NMR (75 MHz, CDCl3) δ 21.7, 120.7, 121.6, 127.3,
129.7, 130.0, 132.3, 132.4, 132.8 (2C), 140.0. Anal. Calcd for
C11H9BrSSe: C, 39.78; H 2.73. Found: C, 39.75; H, 2.76.
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Article
136.6, 136.7 (2C), 136.9, 139.8, 143.0. HRMS Calcd for C15H12BrNSe
[M + H]+: 365.9375. Found: 365.9389.
3-(Pyridin-3-ylselanyl)quinoline (Table 6, Entry 1): Yellow oil
cm−1; 1H NMR (300 MHz, CDCl3) δ 4.61−4.65 (m, 2H), 5.32 (dd, J1
= 12 Hz, J2 = 1.5 Hz, 1H), 5.49 (dd, J1 = 15 Hz, J2 = 1.5 Hz, 1H),
6.02−6.12 (m, 1H), 6.81−6.89 (m, 2H), 7.02 (dd, J1 = 7.5 Hz, J2 = 1.5
Hz, 1H), 7.17−7.22 (m, 1H), 7.36−7.40 (m, 3H), 7.64−7.67 (m, 2H);
13C NMR (75 MHz, CDCl3) δ 69.3, 111.9, 117.4, 121.8, 122.7, 127.5,
128.1, 128.3, 129.5 (2C), 130.7, 132.9, 135.6 (2C), 155.6. Anal. Calcd
for C15H14OSe: C, 62.29; H, 4.88. Found: C, 62.25; H, 4.90.
(259 mg, 91%); Rf = 0.2 (hexane/ethyl acetate = 9:1); IR (neat) 3446,
1
3031, 1616, 1558, 1490, 1463, 1404, 1352, 1126, 1012, 948 cm−1; H
NMR (300 MHz, CDCl3) δ 7.18−7.22 (m, 1H), 7.55 (t, J = 8 Hz,
1H), 7.68−7.79 (m, 3H), 8.07 (d, J = 8 Hz, 1H), 8.28 (s, 1H), 8.52 (s,
1H), 8.74 (s, 1H), 8.91 (s, 1H); 13C NMR (75 MHz, CDCl3) δ 123.9,
124.7, 127.4, 127.5, 128.6 (2C), 129.5, 130.2, 140.5, 140.6, 147.1,
148.9, 153.0, 153.5. HRMS Calcd for C14H10N2Se [M + H]+:
287.0078. Found: 287.0083.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
The copies of H NMR and 13C NMR spectra of all products
3-(Thiophen-2-ylselanyl)pyridine (Table 6, Entry 2): Colorless
listed in Tables 3−6 and in Schemes 2 and 3. This material is
available free of charge via the Internet at http://pubs.acs.org.
viscous liquid (201 mg, 84%); Rf = 0.4 (hexane/ethyl acetate = 9:1);
1
IR (neat) 3456, 3029, 1568, 1471, 1458, 1351, 1136, 993 cm−1; H
NMR (500 MHz, CDCl3) δ 7.05 (t, J = 4 Hz, 1H), 7.16 (m, 1H), 7.35
(d, J = 3 Hz, 1H), 7.48 (d, J = 6 Hz, 1H), 7.63 (d, J = 8 Hz, 1H), 8.42
(s, 1H), 8.59 (s, 1H); 13C NMR (125 MHz, CDCl3) δ 121.7, 124.4,
128.6, 130.8, 132.7, 137.6, 137.9, 147.9, 150.5. HRMS Calcd for
C9H7NSSe [M + H]+: 241.9531. Found: 241.9538.
AUTHOR INFORMATION
Corresponding Author
*E-mail: ocbcr@iacs.res.in.
Notes
■
3-(Thiophen-3-ylselanyl)pyridine (Table 6, Entry 3): Colorless
liquid (194 mg, 81%); Rf = 0.4 (hexane/ethyl acetate = 9:1); IR (neat)
The authors declare no competing financial interest.
1
3455, 3021, 1565, 1472, 1452, 1350, 1132, 990 cm−1; H NMR (300
MHz, CDCl3) δ 7.10 (d, J = 5 Hz, 1H), 7.15−7.19 (m, 1H), 7.36−
7.38 (m, 1H), 7.48−7.49 (m, 1H), 7.62−7.66 (m, 1H), 8.43 (d, J = 4
Hz, 1H), 8.56 (s, 1H); 13C NMR (75 MHz, CDCl3) δ 121.0, 124.4,
127.5, 130.2, 130.5, 132.7, 138.9, 147.4, 150.7. Anal. Calcd for
C9H7NSSe: C, 45.01; H, 2.94; N, 5.83. Found: C, 45.05; H, 2.96; N,
5.81.
1-(4-(Methylselanyl)phenylselanyl)benzene (Scheme 2,
Compound A): Yellow viscous liquid (264 mg, 81%); Rf = 0.65
(hexane/diethyl ether = 9:1); IR (neat) 3055, 2920, 2850, 1577, 1475,
1437, 1384, 1215, 1097 cm−1; 1H NMR (500 MHz, CDCl3) δ 2.47 (s,
3H), 7.16 (d, J = 8 Hz, 2H), 7.25−7.31 (m, 4H), 7.43 (d, J = 8 Hz,
3H); 13C NMR (125 MHz, CDCl3) δ 15.8, 111.7, 126.9, 127.2, 127.4
(2C), 129.4 (2C), 132.5 (2C), 134.2 (2C), 138.6. Anal. Calcd for
C13H12Se2: C, 47.87; H, 3.71. Found: C, 47.82; H, 3.74.
1-(3-(Phenylselanyl)phenylselanyl)-4-methoxybenzene
(Scheme 2, Compound B): Pale yellow liquid (317 mg, 76%); Rf =
0.55 (hexane/diethyl ether = 9:1); IR (neat) 3057, 2924, 2835, 1591,
1570, 1491, 1438, 1286, 1246, 1172, 1030 cm−1; 1H NMR (500 MHz,
CDCl3) δ 3.73 (s, 3H), 6.74−6.79 (m, 4H), 7.09−7.18 (m, 4H), 7.26
(t, J = 7 Hz, 2H), 7.33−7.42 (m, 1H), 7.45 (d, J = 8 Hz, 2H); 13C
NMR (125 MHz, CDCl3) δ 55.4, 115.2, 115.5 (2C), 120.1, 126.6
(2C), 129.2 (2C), 131.0 (2C), 133.3 (2C), 133.6 (2C), 136.6 (2C),
137.2, 159.9. Anal. Calcd for C19H16OSe2: C, 54.56; H, 3.86. Found:
C, 54.59; H, 3.82.
ACKNOWLEDGMENTS
■
We are pleased to acknowledge the financial support from
CSIR, New Delhi [Grant no. 01(2365/10/EMR-II], and DST,
New Delhi, for a J.C. Bose Fellowship to B.C.R. (Grant no. SR/
S2/JCB-11/2008) for this investigation. T.C. thanks CSIR for
his fellowship.
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Compound C): Yellow oil (231 mg, 71%); Rf = 0.6 (hexane/diethyl
ether = 9:1); IR (neat) 3051, 2935, 2831, 1575, 1482, 1430, 1375,
1
1220, 1095 cm−1; H NMR (500 MHz, CDCl3) δ 2.24 (s, 3H), 7.00
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3-(3-Methyl-4-(thiophen-3-ylselanyl)phenylselanyl)pyridine
(Scheme 2, Compound D): Pale yellow oil (302 mg, 74%); Rf = 0.5
(hexane/ethyl acetate = 9:1); IR (neat) 3386, 3099, 2921, 1739, 1566,
1
1461, 1404, 1348, 1193, 1083, 1031, 1012, 846 cm−1; H NMR (400
MHz, CDCl3) δ 2.34 (s, 3H), 6.91 (d, J = 8 Hz, 1H), 7.08−7.20 (m,
2H), 7.30 (s, 1H), 7.35−7.39 (m, 2H), 7.45−7.48 (m, 1H), 7.70 (d, J
= 12 Hz, 1H), 8.57 (s, 1H), 8.62 (s, 1H); 13C NMR (100 MHz,
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1573, 1471, 1440, 1379, 1274, 1240, 1132, 1101, 1018, 997, 921, 774
7152
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