Synthesis of 2,3-bis-organochalcogenyl-benzo[b]chalcogenophenes promoted by Oxone

Article abstract of DOI:10.1039/c9nj00526a

We report here an alternative and tunable metal-free synthesis of benzo[b]chalcogenophenes via the electrophilic cyclization of 2-functionalized chalcogenoalkynes promoted by Oxone. The use of mild reaction conditions, efficiency and generality are characteristics of this new approach, which was suitable to convert different diselenides and 2-functionalized chalcogenoalkynes into a total of twenty-two 2,3-bis-organochalcogenyl-benzo[b]chalcogenophenes, eighteen of which were synthesized for the first time. The new compound 2-(butylselanyl)-3-(phenylselanyl)benzofuran was used as a substrate in the Pd-catalyzed reaction with phenylacetylene to access the Sonogashira's coupling derivative in good yield.

Full text of DOI:10.1039/c9nj00526a

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Chem., 2019, DOI: 10.1039/C9NJ00526A.
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Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
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Synthesis of 2,3-bis-organylchalcogenyl-
benzo[b]chalcogenophenes promoted by Oxone®
Received 00th January 2019,
Accepted 00th January 2019
Gelson Perin,*a Liane K. Soares,a Paola S. Hellwig,a Marcio S. Silva,a José S. S. Neto,a Juliano A.
Roehrs,b Thiago Barcellosc and Eder J. Lenardão*a
DOI: 10.1039/x0xx00000x
We report here an alternative and tunable metal-free synthesis of benzo[b]chalcogenophenes via the electrophilic
cyclization of 2-functionalized chalcogenoalkynes promoted by Oxone®. The use of mild reaction conditions, efficiency and
generality are characteristics of this new approach, which was suitable to convert different diselenides and 2-
www.rsc.org/
functionalized chalcogenoalkynes into
a total of twenty-two 2,3-bis-organochalcogenyl-benzo[b]chalcogenophenes,
eighteen of them were synthesized for the first time. The new compound 2-(butylselanyl)-3-(phenylselanyl)benzofuran
was used as a substrate in the Pd-catalyzed reaction with phenylacetylene to access the Sonogashira’s coupling derivative
in good yield.
organoselanyl-naphthalenes by the carbocyclization of
alkynols15 and in the metal-free synthesis of diorganyl
selenides from boronic acids.16
Introduction
Among the chalcogenides, those that are part of heterocycles
The use of potassium peroxymonosulfate (Oxone®) as an
oxidizing agent in organic synthesis has increased in the last
years. Oxone® is stable under various conditions, it is simple to
handle and environmentally safe, thus being a promising non-
toxic alternative to the chemical industry.1 Oxone® is a
commercially available triple salt (2KHSO5.KHSO4.K2SO4) having
50% of active oxidant/mol (the anion peroxymonosulfate,
or are connected to a heterocycle, are of great importance due
to their application in electrochemistry,17 biochemistry,18
materials science19 and in organic synthesis.20 In particular,
benzo[b]chalcogenophenes are a class of compounds of
increasing interest, once they can be used in the preparation
of semiconductor materials,21 optical devices,22 film
transistors23 and solar cells.24 Moreover, these compounds
have promising pharmacological applications,25 and are found
in various worldwide commercialized drugs.26
HSO5 ) and is used in classical functional group oxidations,2
−
rearrangements,3 cross-coupling,4 epoxidation of olefins,5
protection and deprotection6 and in the preparation of
As a consequece of the versatility of this class of compounds,
heterocyclic
compounds,
as
benzimidazoles
and
there are
a number of methodologies to synthesize
benzoxazoles,7 indenochromenes,8 imidazoles,9 pyrazoles10
and pyridines.11
benzo[b]chalcogenophenes,27 which include the use of
hypervalent iodine species,28 transition metal-catalysis,29
radical intramolecular cyclization,30 intramolecular nucleophilic
addition,31 electrophilic cyclization of chalcogenoalkynes using
I2, ICl, Br2, NBS, PhSeCl and PhSeBr32 or the generation of the
electrophilic species in situ from diorganyl diselenides or
The versatility of Oxone® was explored in the synthesis of
organochalcogen compounds, especially organosulfur ones,12
while the synthesis of the organoselenium analogues was less
investigated.13 In the last years, our group started the studies
on the reactivity of organoselenium compounds front to
Oxone®.14-16 It was observed that an electrophilic species of
selenium is formed in situ under mild conditions, which was
used in the synthesis of β-methoxy- and β-hydroxy-selenides
from styrenes,14 in the ultrasound-promoted synthesis of 2-
33
disulfides in the presence of FeCl3 and the addition of
selenium tetrahalides (SeCl4 or SeBr4) to aryl- and
diarylalkynes.34
Despite the recent advances in the synthesis of
benzo[b]chalcogenophenes, many of the current protocols are
not atom-economic and, in some cases, the participation of
transition metal catalysts is involved. There is still an important
restriction with respect to the pendent chalcogen groups at
the heterocyclic ring: the number of general protocols to
access benzo[b]chalcogenophenes 2,3-difunctionalized with
different organochalcogen groups is limited and just a few
authors have explored the synthesis of the corresponding
nucleous 2- or 3-functionalized.32b,f,i,33a,35,36 In the case of the
a. LASOL-CCQFA, Universidade Federal de Pelotas – UFPel; P.O. Box 354, 96010-900,
Pelotas, RS, Brazil. http://wp.ufpel.edu.br/lasol; gelson_perin@ufpel.edu.br (G.
Perin) and lenardao@ufpel.edu.br (E. J. Lenardão).
b. Instituto Federal Sul-Rio-Grandense, Campus Pelotas - Praça Vinte de Setembro
96015-360, RS, Brazil.
c. Laboratory of Biotechnology of Natural and Synthetic Products – Universidade de
Caxias do Sul – UCS, 95070-560, Caxias do Sul, RS, Brazil.
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: Figures of the NMR spectra
of all the prepared compounds. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
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atmosphere, affording the desired product 3a in 75% yield
DOI: 10.1039/C9NJ00526A
after 24 h (Table 1, entry 1). When the amount of diphenyl
synthesis
of
2,3-dichalcogen-substituted
View Article Online
benzo[b]chalcogenophenes by electrophilic cyclization, there is
only one general methodology described by Zeni and co-
workers in 2009 to access benzo[b]furans,32c and one to access
benzo[b]selenophenes, developed by Perin and co-workers in
201732h (Scheme 1, ‘Previous Works’). Therefore, considering
the importance of functionalized benzo[b]chalcogenophenes,
it is still necessary to develop new convenient and single step
methodologies to access this class of compounds.
diselenide 2a was reduced to 0.250 mmol (2.0 equiv), 0.190
(1.5 equiv) and 0.140 mmol (1.1 equiv), 3a was obtained in
61%, 40% and 55% yields, respectively (Table 1, entries 2-4).
o
Following, experiments #2 and #3 were repeated, but at 78 C
(refluxing ethanol) instead of at room temperature, aiming to
increase the yield of 3a (Table 1, entries 5 and 6). In both
cases, the expected product 3a was obtained in higher yield
and lower reaction time compared to the room temperature
experiments, i.e., 71% after 30 min (Table 1, entry 5) and 66%
yield after 20 h (Table 1, entry 6). It’s important to consider
that, despite only half of the PhSeSePh 2a can be incorporated
to the final product 3a, once the PhSe- 2a’ counterpart would
be necessary for the removal of the propyl group bonded to
the sulfur atom in 1a (see mechanism, below), forming PhSePr,
which can be recovered at the end of the reaction. Fortunately, by
using a small excess of diphenyl diselenide 2a (0.275 mmol; 2.2
equiv), the product 3a was obtained in 83% yield after 30 min
(Table 1, Entry 7).
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Herein, we describe the efficient electrophilic cyclization of
chalcogenoalkynes 1 (Z = S), 4 (Z = O) and 6 (Z = Se) to prepare
2,3-bis-organylchalcogenyl-benzo[b]chalcogenophenes 3 (Z =
S), 5 (Z = O) and 7 (Z = Se) using an electrophilic selenium
species generated in situ by the reaction of diorganyl
diselenides 2 with Oxone® (Scheme 1).
Previous works:
2
2
Y
R
2YY
R
E
R
R
E+
FeCl3
ref. 33a
R
R
ref. 32b,f,i
O
Z
1
Z
R
; R = R2 = aryl, alkyl; R1 = alkyl
O S Se Y Se S Te
Z
=
=
,
,
;
=
,
,
E
I2, ICl, PhSeBr, PhSeCl, Br2, NBS
Table 1 Optimization of reaction conditions for synthesis of 3a.a
Y
R
E
E
Se
C6H5
Se
C6H5
+
E+
E+
Oxone®
solvent, Ar
Y
Y
R
=
R
Se
C6H5
)
2
Se
C6H5
ref. 32h
ref. 32c
Se
O
1
Z
R
Z
Se
=
Z
O
S
=
2a
temperature
S
3a
1
1a
Y
S Se
E
,
; R = aryl, alkyl; R = alkyl; = I2, PhSeBr, Br2
#
Oxone®
(mmol)
2a
Solvent
T (°C)
Time
(h)
Yield
3a (%)b
This work:
(mmol)
2
Se
R
Oxone®
ethanol
Y
R
1
2
0.750
0.750
0.750
0.750
0.750
0.750
0.750
0.500
0.375
0.250
0.250
0.250
0.140
0.250
0.250
0.250
0.250
0.250
0.375
0.250
0.190
0.140
0.250
0.190
0.275
0.275
0.275
0.275
0.190
0.140
0.140
0.275
0.275
0.275
0.275
0.275
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
ethanol
25
25
24
24
24
24
0.5
20
0.5
0.5
0.5
0.5
0.5
1.5
1.5
2.5
2
75
61
2
2SeSe
2
Y
R
R
R
+
Ar, reflux
0.5-7.0 h
Z
1
Z
R
3
25
40
, R1 = C3H7
=
or
3 Z
:
S
=
1 Z
:
S
Y
S
Se
=
=
4
25
55
5 Z = O
:
, R1 = CH3 R = R2 = alkyl, aryl
4 Z
:
O
5
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
90
71
7 Z Se
:
=
6 Z Se
:
=
, R1 = C4H9
6
66
Scheme 1 Previous works on the synthesis of 3-functionalized and 2,3-
difunctionalized benzo[b]chalcogenophenes and benzo[b]furans and
our general protocol to the synthesis of 2,3-bis-organochalcogenyl-
7
83
8
80
9
72
benzo[b]chalcogenophenes
and
benzo[b]furans.
10
11
12
13
14
15
16
17
18
95
82
Results and discussion
83
62
Our initial attempts were aimed in the development of a
general protocol with green features for the synthesis of
benzo[b]chalcogenophenes. For that, our optimization studies
were focused on the reduction of reagent quantities and in the
use of a eco-friendly solvent. The role of the stoichiometry of
the reagents, the temperature and solvent was examined and
the results are presented in Table 1. Initially, 1-(2-
phenylselenanylethynyl)-2-propylsulfanylbenzene 1a and
diphenyl diselenide 2a were chosen as starting materials to
acetonitrile
PEG-400
glycerol
DCM
82
73
80
2
36
reflux
60
24
24
traces
NR
H2O
a
Reaction conditions: 1-(2-phenylselenanylethynyl)-2-propylsulfanyl-
benzene 1a (0.250 mmol); diphenyl diselenide 2a; Oxone® and solvent
(4.0 mL) under Ar atmosphere. b Isolated yields. NR = no reaction.
establish the best reaction conditions for the synthesis of 2,3- After fixing 2.2 equiv as the optimal quantity of PhSeSePh 2a,
the amount of Oxone® was evaluated (Table 1, entries 8-10).
To our satisfaction, when 1.0 equiv of Oxone® (0.250 mmol)
was used, the expected product 3a was obtained in 95% yield
after 30 min (Table 1, Entry 10). In the sequence, different
bis(phenylselanyl)benzo[b]thiophene 3a. A mixture of alkyne
1a (0.250 mmol), diphenyl diselenide 2a (0.375 mmol; 3.0
equiv), and Oxone® (0.750 mmol; 3.0 equiv) in ethanol (4.0
mL) was stirred at room temperature under argon
2 | J. Name., 2012, 00, 1-3
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amounts of diselenide 2a (1.5 equiv and 1.1 equiv) were used Diselenides containing electron-releasing groups,VlieikweAr2ticble (ORn1lin=e
1
DOI: 10.1039/C9NJ00526A
in the presence of 1.0 equiv of Oxone®, however, a decrease in CH3) and 2c (R = CH3O) were more reactive than the electron-
yields to 82% and 83%, respectively was observed (Table 1, poor analogues, affording the respective products 3b and 3c in
entries 11 and 12). When the amount of both, Oxone® and 78% and 46% yields after 2 h and 2.5 h, respectively. The low
diphenyl diselenide 2a was diminished to 0.140 mmol (Table 1, yield of compound 3c could be attributed to its instability
entry 13), the compound 3a was obtained in 62% yield after under the reaction conditions. The presence of electron-
1.5 h of reaction.
withdrawing substituents decreased the reactivity of the diaryl
Finally, a study on the influence of the solvent in the reaction diselenide and 2d (R1 = Cl) and 2e (R1 = F) required a slightly
was performed. When acetonitrile was used, the desired longer reaction time to deliver acceptable yields of 3d and 3e,
product 3a was obtained in 82% yield after 2.5 h of reaction which were isolated in 80% and 79% yields after 4 h and 7 h,
under reflux (Table 1, entry 14). Using PEG-400 (at 90 °C), the respectively. The aliphatic dibutyl diselenide 2f was
desired 2,3-bis(phenylselanyl)benzo[b]thiophene 3a was successfully used as substrate in the reaction, affording the
obtained in 73% yield after 2 h (Table 1, entry 15). Glycerol respective product 3h in 80% yield after 3.5 h.
was not a good solvent for this reaction, affording the product
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3a in only 36% yield after 2 h at 80 oC (Table 1, entry 16). Only Table 3 Synthesis of benzo[b]furans 5a-g promoted by Oxone®.a,b
Se
Ar
trace amounts of 3a was observed using DCM, while no
reaction was observed when H2O was used as the solvent
(Table 1, entries 17 and 18). Thus, the best reaction condition
was stablished as stirring a mixture of alkyne 1a (0.250 mmol),
diphenyl diselenide 2a (0.275 mmol), and Oxone® (0.250
mmol) in ethanol (4.0 mL) for 30 min under reflux and argon
inert atmosphere (Table 1, entry 10).
Y
R
Oxone®, Ar
ethanol, reflux
Y
+
SeSe
2
Ar
Ar
O
R
O
7 examples
5a-g
4a Y Se
:
=
=
4b Y
:
S
R
R
Table 2 Synthesis of benzo[b]thiophenes 3a-k promoted by Oxone®.a,b
Se
Se
1
Se
R
Y
R
S
Se
Oxone®, Ar
ethanol, reflux
O
1
O
Y
R
+
1SeSe
2
R
R
S
S
1a-d
11 examples
3a-k
5a
5b
5c
: R = H, 0.5 h, 85%
: R = Cl, 4.0 h, 68%
: R = F, 2.5 h, 71%
5d
5e
5f
: R = H, 0.5 h, 89%
: R = CH3O, 1.5 h, 42%
: R = Cl, 2.0 h, 84%
Y
S Se
,
=
R1
Se
Se
Se
O
Se
S
Se
Se
S
R
5g
: 2.0 h, 70%
3h
: 3.5 h, 80%
R1
R
a
Reactions performed in the presence of alkyne 4 (0.250 mmol),
Se
1
3a
: R = R = H, 0.5 h, 95%
diorganyl diselenide 2 (0.275 mmol), ethanol (4.0 mL), Oxone® (0.250
mmol) under Ar atmosphere at reflux temperature. b Isolated yields.
1
S
3b
: R = H, R = CH3, 2.0 h, 78%
1
S
3c
: R = H, R = CH3O, 2.5 h, 46%
1
3d
: R = H, R = Cl, 4.0 h, 80%
Afterward, the reactivity of alkynes with different chalcogen-
groups at the alkyne pendent group in the reaction with
diphenyl diselenide 2a was investigated. The presence of the
electron-withdrawing group in the aromatic ring of the
selenoalkyne derivative 1b (R = F), decreased the reactivity,
and a long reaction time of 7 h was necessary to afford the
product 3g in 83% yield. The electron-rich selenoalkyne 1c (R1
= CH3) was a more reactive substrate, giving the expected
product 3h in 73% yield after 2 h. These results show that the
reaction is sensible to electronic effects acting both in the
diaryl diselenides 2 and in the selenoalkynes 1 and in a similar
way. Following, the reactivity of thioalkyne 1d (YR = SC6H5) in
the reaction with diphenyl diselenide 2a under our optimal
conditions, and the respective product 3i was obtained in 93%
yield after 0.5 h. Thioalkyne 1d reacted equally well with bis(4-
1
3e
: R = H, R = F, 7.0 h, 79%
1
3i
3j
: R = H, 0.5 h, 93%
1
3f
: R = 4-F, R = H, 7.0 h, 83%
1
: R = CH3O, 3.5 h, 70%
1
3g
: R = 4-CH3, R = H, 2.0 h, 73%
1
3k
: R = Cl, 2.0 h, 65%
a Reactions performed in the presence of alkyne 1 (0.250 mmol), diorganyl
diselenide 2 (0.275 mmol), ethanol (4.0 mL), Oxone® (0.250 mmol) under Ar
b
atmosphere
at
reflux
temperature.
Isolated
yields.
Once the best conditions were determined for the synthesis of
2,3-bis(phenylselanyl)benzo[b]thiophene 3a, the scope and
limitations of the methodology were explored by reacting
different 1-(2-arylselenanylethynyl)-2-propylsulfanylbenzenes
1a-d with a variety of diorganyl diselenides 2a-f and the results
are showed in Table 2. The presence of substituents in the
phenyl ring of the diselenide 2 negatively affects the reaction.
methoxyphenyl) diselenide 2c (R1
= OCH3) and bis(4-
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chlorophenyl) diselenide 2d (R = Cl), affording the expected by 2,3-bis-phenylselenobenzo[b]furan 5a (3%)V,iewuAnrtriceleaOcntleinde
products 3j and 3k in 70% and 65% yields after 3.5 h and 2 h, diphenyl ditelluride 8 (86%) and selenDoOalI:k1y0n.1e0349a/C9(N4%J0)05a2n6dA
respectively (Table 2).
diphenyl diselenide 2a (7%) (see Figure S47 in the Supporting
Next, the reactivity of 1-(2-phenylselanylethynyl)-2- Information for experimental details and GC chromatograms).
methoxybenzene 4a front to several diorganyl diselenides 2 Still interested in obtaining organotelluro-functionalized
was evaluated, yielding the desired benzo[b]furans 5a-c in benzo[b]furans, we examined the possibility of using [(2-
moderate to good yields in up to 4 h of reaction (Table 3). methoxyphenyl)ethynyl](phenyl)tellane 4c and diphenyl
Similarly to the observed in the syntheses of the diselenide 2a as substrates in the electrophilic cyclization.
benzo[b]thiophenes 3, the best result was obtained using Unfortunately, this condition also led to the di-selenylated
PhSeSePh 2a (85% yield, 0.5 h of reaction), with bis(4- benzo[b]furan 5a in 43% after 1.5 h of reaction, while diphenyl
chlorophenyl)- and bis(4-fluorophenyl) diselenides 2d and 2e diselenide 2a was detected in 12%. In this case, also were
affording the expected benzo[b]furans 5b and 5c in 68% and observed selenoalkyne 4a (2%) and diphenyl ditelluride 8 (44%
71% yields after 4 h and 2.5 h of reaction (Table 3). The of the crude mixture). This could be attributed to the greater
protocol was successfully extended to phenylthioalkyne 4b (Y = stability of product 5a compared to the Te-substituted
S), which reacted with diselenides 2a (R = H) and 2d (R = Cl) to analogue (see Figure S48 in the Supporting Information for
afford the respective benzo[b]furans 5d and 5f in 89% and 84% experimental details and GC chromatograms).
yields, after 0.5 h and 2 h of reaction, respectively. The To complete the evaluation of the versatility of our protocol,
presence of the strong electron-donor methoxy group in the the reactivity of different diselenides 2 with 2-butylselanyl
diselenide 2c (R = OCH3) caused a drastic reduction in the functionalized phenylselenoalkyne 6, aiming to obtain
reactivity, and the respective benzo[b]furan 5e was obtained different benzo[b]selenophenes 7, was examined. As it can be
in only 42% yield. The versatility of this protocol was seen in Table 4, the presence of electron-releasing methyl
demonstrated in the cyclization of the butylselenoalkyne 4c in group in the phenyl ring in the diselenide positively influenced
the presence of diselenide 2a under the standard conditions, the reactivity, and 2b (R = CH3) reacted with 6 to afford the
giving the expected benzo[b]furan 5g in 70% yield after 2 h of expected benzo[b]selenophene 7b in 94% yield after 2 h.
reaction (Table 3). It is important to point out that the Unsubstitued diphenyl diselenide 2a and the electron-poor
benzo[b]furans 5 were more unstable when compared to the diselenides 2d (R = Cl) and 2e (R = F) afforded around the
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thiophenes and selenophenes analogues.
respective products 7a, 7c and 7d in 73%, 75% and 71% yields
after 3 h of reaction.
Table
Oxone®.a,b
4
Synthesis of benzo[b]selenophenes 7a-d promoted by In order to prove the potential of benzo[b]chalcogenophenes
as precursors to more complex molecules, 2-(butylselanyl)-3-
(phenylselanyl)benzo[b]furan 5g was subjected to
Sonogashira cross-coupling with phenylacetylene 9.37 The
expected coupling product, 2-(phenylethynyl)-3-
Se
Se
Ar
a
Oxone®, Ar
ethanol, reflux
SeSe
2
Ar
Ar
+
Se
Se
Se
6
4 examples
7
(phenylselanyl)benzo[b]furan 10 was obtained in 50% yield
after 24 h of reaction (Scheme 2).
Se
Se
9
Se
Se
Se
Se
Se
7a
Se
7b
2 h, 94%
PdCl2(P(C6H5)3)2
Cu(OAc)2.H2O
Se
(C2H5)3N, DMF
24 h, 80 °C
3 h, 73%
O
O
10
50%
F
Cl
5g
Se
Se
Scheme 2 Pd-catalized Sonogashira cross-coupling reaction.
Se
Se
Se
7c
3 h, 75%
Se
7d
3 h, 71%
Aiming to collect evidences to understand the reaction
pathway, some control experiments involving the reaction of
thioalkyne 1a and diphenyl diselenide 2a were performed
(Scheme 3). Firstly, the reaction was conducted presence of
radical inhibitors 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)
and benzene-1,4-diol (hydroquinone) under the standard
conditions and the expected product 3a was isolated in 73%
and 58% yields, respectively (Scheme 3, Eq. I). These outcomes
suggest that the reaction pathway involves, at least in part,
free radical intermediate. In order to verify the role of each
constituent salt of Oxone® in the formation of the electrophilic
species of selenium, a second set with five control experiments
was conducted. The reaction of 1a and 2a was performed
a Reactions performed in the presence of alkyne 6 (0.250 mmol), diorganyl
diselenide 2 (0.275 mmol), ethanol (4.0 mL), Oxone® (0.250 mmol) under Ar
b
atmosphere
at
reflux
temperature;
Isolated
yields.
Based on the results obtained and in order to extend the scope
of this methodology, we tested the reactivity of the
selenoalkyne 4a toward diphenyl ditelluride 8 to access the
corresponding 2-phenylseleno-3-phenyltellurobenzo[b]furan.
However, after 1.5 h of reaction, none of the expected product
was observed (GC/MS), and the crude mixture was composed
4 | J. Name., 2012, 00, 1-3
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2-
using KHSO4, NaHSO4, K2SO4 and Na2SO4 and a 1:1 mixture of
KHSO4 and K2SO4 (2 equiv) instead Oxone® (Scheme 3, Eq. II). In
all the reactions, the product 3a was not detected, indicating
that potassium peroxymonosulfate (KHSO5) probably is the
active oxidant in this reaction, responsible by the cleavage of
the Se-Se bond in the diselenide.
nucleophilic species present in the reaction medium (SO4
,
View Article Online
-
HSO4 ) to form the expected product 3a. DOI: 10.1039/C9NJ00526A
Conclusions
In summary, we have demonstrated for the first time the
9
selective
and
modular
synthesis
of
new
Se
C6H5
Se
C6H5
10
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benzo[b]chalcogenophenes (O, S, Se) by the simple reaction
between diorganyl diselenides and 2-organylchalcogen-
functionalized chalcogenoalkynes promoted by Oxone®. The
same strategy can be used to prepare the title compounds
with a diversity of substituent patterns selectively in the
absence of transition metal and by a mild and simple protocol.
Under these conditions, it was possible to obtain twenty-two
2,3-bis-organochalcogen- benzo[b]chalcogenophenes (eighteen
new ones) in good to excellent yields, contributing to expand
the range of applications of Oxone® in the organoselenium
chemistry.
standard conditions
radical scavenger
(I)
Se
C6H5
S
3a
S
hidroquinone = 56%
TEMPO = 77%
1a
+
Se
C6H5
SeSe
C6H5
C6H5
2-
HSO4- or SO4
2a
(II)
Se
C6H5
-
HSO4 /SO42- (1:1)
S
ethanol, reflux, 12 h
3a
not formed
Scheme 3 Eq. I: Reactions in the presence of radical scavengers; Eq. II:
Reactions using the salts present in Oxone®.
Experimental
Formation of the electrophiles:
Oxone
= HOOSO3K + ½KHSO4 + ½K2SO4
General remarks
a) Ionic mechanism:
KSO4
+
The reactions were monitored by thin TLC sheets ALUGRAM® Xtra
SIL G/UV254. For visualization, TLC plates were either placed under
UV light, stained with iodine vapor and 5% vanillin in 10% H2SO4 and
heat. Column chromatography was performed using Merck Silica
Gel (pore size 60 Å, 230-400 mesh). Carbon-13 nuclear magnetic
resonance (13C NMR) and hydrogen nuclear magnetic resonance
spectra (1H NMR) were obtained on Bruker Avance III HD
spectrometers at 100 MHz at 400 MHz, respectively. Spectra were
recorded in CDCl3 solutions. Chemical shifts are reported in ppm,
referenced to tetramethylsilane (TMS) as the internal reference for
1H NMR and the solvent peak of CDCl3 for 13C NMR. Coupling
constants (J) are reported in Hertz and chemical shift (δ) in ppm.
Abbreviations to denote the multiplicity of a particular signal are s
(singlet), d (doublet), dd (doublet of doublet), ddd (doublet of
doublet of doublets), dt (doublet of triplets), t (triplet), quint
(quintet), sext (sextet), and m (multiplet). Low-resolution mass
spectra (MS) were measured on a Shimadzu GC-MS-QP2010 mass
spectrometer. The high-resolution atmospheric pressure chemical
ionization (APCI-QToF) analyses were performed on a Bruker
Daltonics micrOTOF-Q II instrument operating in the positive ion
detection mode. For data acquisition and processing, Compass 1.3
for micrOTOF-Q II software (Bruker Daltonics, USA) was used.
Melting point (m.p.) values were measured in a Marte PFD III
instrument with a 0.1 °C precision. The Oxone® was purchased from
Sigma-Aldrich. The 2-functionalized chalcogenoalkynes 1, 4 and 6
were previously prepared as described by Zeni and co-workers,32c
with small modifications.
- KSO4
Se Se
C6H5
C6H5
Se
Se
C6H5
OSO3K +
C6H5 OH
SeSe
2a
C6H5
C6H5
+
HO OSO3K
A
B
OH
active
electrophilic
species
b) Radical mechanism:
Se
Se
C6H5
C6H5
Se
Se
C6H5
OSO3K
OH
OSO3K
SET
+
+
Se
C6H5SeOH
C6H5
OSO3K +
C6H5
OH
A
B
2a
active
electrophilic
species
Activation of intermediate B:
KSO4
KHSO4
H2O
Se
C6H5
OSO3K +
Se
Se
C6H5 OH
C6H5 OH2
A
active
B
B'
active
electrophilic
species
electrophilic
species
Cyclization step:
Se
C6H5
- KSO4
- H2O
Se
C6H5
Se
C6H5
Se
Se
A
C6H5
or
OSO3K
OH2
Se
C6H5
C6H5
S
S
S
Se
C6H5
+
3a
C
(nC3H7)nNu
Nu-n
1a
B'
-2
Nu = HSO4-, SO4
Scheme
4
Proposed mechanism for the synthesis of
benzo[b]thiophene 3a.
Thus, based on the control experiments and in previous reports38
on reactions involving the oxidation of diselenides with persulfate
anion,39 the following plausible mechanism for the formation of 3a
from 1a and 2a is proposed (Scheme 4). Firstly, the reaction of
potassium peroxymonosulfate (KHSO5) with diselenide 2a
affords two electrophilic selenium species, A and B. Because
the reaction works partially in the presence of radical
scavengers (Scheme 3, Eq. I) two mechanisms are involved in
the formation of A and B: an ionic and a radical (SET) one. The
intermediate B is activated in the acidic medium to form B‘, a
strong electrophile. In the cyclization step, alkyne 1a reacts
with A to release sulfate anion and with the protonated
species B‘, releasing water and forming the sulfonium
intermediate C. Then, intermediate C undergoes an attack by
General procedure for the synthesis of benzo[b]thiophenes 3,
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benzo[b]furans 5 and benzo[b]selenophenes 7 promoted by 3-[(4-Fluorophenyl)selanyl]-2-(phenylselanyl)benzo[b]thiophene
View Article Online
1
DOI: 10.1039/C9NJ00526A
Oxone®
3e: Yield: 0.092 g (79%); yellow solid, m.p. 67-68 °C. H NMR (CDCl3,
In a two-necked round-bottomed flask under argon atmosphere,
equipped with magnetic stirring and reflux system, it was added a
solution of the appropriate diorganyl dichalcogenide 2 (0.275
mmol) in ethanol (3.0 mL). After, Oxone® (2KHSO5.KHSO4.K2SO4,
MW = 307 g.mol-1; 0.25 mmol; 0.077 g) was added and the reaction
mixture was stirred at room temperature for 10 min. Then, a
solution of the alkyne 1, 4 or 6 (0.25 mmol) in ethanol (1.0 mL) was
added dropwise. The resulting mixture was refluxed under stirring
for the time required to consume the starting material 1, 4 or 6 (the
reaction progress was monitored by TLC). After that, saturated
aqueous NH4Cl (3.0 mL) was added and the product was extracted
with ethyl acetate (2x 20.0 mL), dried over MgSO4, filtered, and
concentrated under vacuum. The residue was then purified by
silica-gel chromatography with hexane as the eluent.
400 MHz)  (ppm) = 7.76 (ddd, J = 7.8, 1.3 and 0.7 Hz, 1H), 7.66
(ddd, J = 7.8, 1.3 and 0.7 Hz, 1H), 7.64-7.62 (m, 2H), 7.36-7.22 (m,
7H), 6.87-6.83 (m, 2H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 161.9,
(d, J = 246.3 Hz), 141.6, 141.5, 140.3, 134.8, 132.3 (d, J = 7.9 Hz),
129.5, 129.0, 128.8, 125.9 (d, J = 3.1 Hz), 125.0, 124.5, 123.7, 122.3,
121.7, 116.3 (d, J = 21.6 Hz). MS (rel. Int.) m/z: 464 (M+, 78.5), 307
(100.0), 288 (79.3), 208 (52.4), 77 (12.8). HRMS: Calculated mass for
C20H13FSSe2 [M]+: 463.9052, found: 463.9053.
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2-[(4-Fluorophenyl)selanyl]-3-(phenylselanyl)benzo[b]thiophene
3f: Yield: 0.096 g (83%); yellow oil. 1H NMR (CDCl3, 400 MHz) 
(ppm) = 7.78-7.75 (m, 1H), 7.69-7.62 (m, 3H), 7.36-7.23 (m, 5H),
7.16-7.14 (m, 3H), 7.04-6.98 (m, 1H). 13C NMR (CDCl3, 100 MHz) 
(ppm) = 163.4 (d, J = 248.4 Hz), 141.7, 141.4, 137.5 (d, J = 8.2 Hz),
134.9, 131.6, 129.9, 129.5, 129.2, 126.4, 125.1, 124.5, 123.8, 123.5
(d, J = 3.5 Hz), 121.7, 116.8 (dd, J = 21.8 and 5.8 Hz). MS (rel. Int.)
m/z: 464 (M+, 85.7), 307 (73.4), 289 (100.0), 208 (51.7), 77 (11.2).
HRMS: Calculated mass for C20H13FSSe2 [M]+: 463.9052, found:
463.9053.
2,3-bis(Phenylselanyl)benzo[b]thiophene 3a: Yield: 0.106 g (95%);
yellow solid; m.p. 70-72 °C. 1H NMR (CDCl3, 400 MHz)  (ppm) =
7.77-7.75 (m, 1H), 7.68-7.64 (m, 3H), 7.39-7.23 (m, 7H), 7.18-7.14
(m, 3H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 141.6, 141.5, 140.5,
134.9, 131.6, 129.8, 129.5, 129.2, 129.0, 128.8, 126.4, 125.0, 124.4,
123.9, 121.7, 121.7. MS (rel. Int.) m/z: 446 (M+, 5.1), 288 (14.1), 207
(14.1), 165 (3.3), 44 (100.0). HRMS: Calculated mass for C20H14SSe2
[M]+: 445.9147, found: 445.9146.
3-(Phenylselanyl)-2-(4-tolylselanyl)benzo[b]thiophene 3g: Yield:
1
0.084 g (73%); yellow oil. H NMR (CDCl3, 400 MHz)  (ppm) = 7.74
(ddd, J = 8.0, 1.3, 0.7 Hz, 1H), 7.68-7.64 (m, 1H), 7.60-7.57 (m, 2H),
7.29-7.21 (m, 5H), 7.18-7.14 (m, 4H), 2.37 (s, 3H). 13C NMR (CDCl3,
100 MHz)  (ppm) = 141.8, 141.3, 139.3, 135.5, 131.7, 130.4, 129.8,
129.6, 129.2, 126.3, 125.1, 124.9, 124.2, 123.6, 121.6, 120.6, 21.3.
MS (rel. Int.) m/z: 460 (M+, 46.0), 303 (42.8), 288 (100.0), 208 (55.0),
77 (10.3). HRMS: Calculated mass for C21H16SSe2 [M]+: 459.9303,
found: 459.9302.
2-(Phenylselanyl)-3-(4-tolylselanyl)benzo[b]thiophene 3b: Yield:
0.090 g (78%); white solid, m.p. 114-115 °C. 1H NMR (CDCl3, 400
MHz)  (ppm) = 7.77 (d, J = 7.8 Hz, 1H), 7.66-7.63 (m, 3H), 7.38-7.22
(m, 5H), 7.19 (d, J = 8.0 Hz, 2H), 6.97 (d, J = 8.0 Hz, 2H), 2.24 (s, 3H).
13C NMR (CDCl3, 100 MHz)  (ppm) = 141.7, 141.5, 140.0, 136.4,
134.8, 130.3, 130.0, 129.5, 129.2, 128.8, 127.7, 124.9, 124.3, 123.9,
122.3, 121.6, 21.0. MS (rel. Int.) m/z: 460 (M+, 51.7), 303 (59.6), 288
(100.0), 208 (46.0), 77 (8.2). HRMS: Calculated mass for C21H16SSe2
[M]+: 459.9303, found: 459.9286.
3-(Butylselanyl)-2-(phenylselanyl)benzo[b]thiophene 3h: Yield:
1
0.085 g (80%); yellow oil. H NMR (CDCl3, 400 MHz)  (ppm) = 7.88
(ddd, J = 8.0, 1.4 and 0.7 Hz, 1H), 7.67-7.64 (m, 3H), 7.39-7.24 (m,
5H), 2.82 (t, J = 7.4 Hz, 2H), 1.60 (quint, J = 7.4 Hz, 2H), 1.4 (sext, J =
7.4 Hz, 2H), 0.86 (t, J = 7.4 Hz, 3H). 13C NMR (CDCl3, 100 MHz) 
(ppm) = 142.2, 141.5, 138.3, 134.6, 134.5, 129.5, 128.6, 124.7,
124.2, 123.8, 122.7, 121.7, 32.6, 28.8, 22.8, 13.5. MS (rel. Int.) m/z:
426 (M+, 64.2), 288 (100.0), 210 (74.3), 208 (42.5), 77 (9.4). HRMS:
Calculated mass for C18H18SSe2 [M]+: 425.9460, found: 425.9463.
3-[(4-Methoxyphenyl)selanyl]-2-(phenylselanyl)benzo[b]thiohene
3c: Yield: 0.055 g (46%), brown solid; m.p. 82-83 °C. 1H NMR (CDCl3,
400 MHz)  (ppm) = 7.81 (ddd, J = 8.0, 1.4 and 0.8 Hz, 1H), 7.64-7.62
(m, 3H), 7.35-7.22 (m, 7H), 6.73-6.69 (m, 2H), 3.72 (s, 3H). 13C NMR
(CDCl3, 100 MHz)  (ppm) = 159.0, 141.73, 141.70, 139.1, 134.7,
132.9, 129.5 (overlapped 2 signals), 128.7, 124.9, 124.4, 124.0,
123.5, 121.7, 121.5, 115.0, 55.2. MS (rel. Int.) m/z: 476 (M+, 54.4),
319 (100.0), 317 (53.1), 286 (41.1), 208 (39.2). HRMS: Calculated
mass for C21H16OSSe2 [M]+: 475.9252, found: 475.9238.
3-(Phenylselanyl)-2-(phenylsulfanyl)benzo[b]thiophene 3i: Yield:
0.092 g (93%); yellow solid, m.p. 56-57 °C. 1H NMR (CDCl3, 400 MHz)
 (ppm) = 7.81-7.77 (m, 1H), 7.70-7.66 (m, 1H), 7.47-7.44 (m, 2H),
7.32-7.25 (m, 7H), 7.16-7.13 (m, 3H). 13C NMR (CDCl3, 100 MHz) 
(ppm) = 144.6, 141.3, 140.4, 134.3, 131.9, 131.6, 130.0, 129.3,
129.2, 128.3, 126.4, 125.1, 125.0, 124.3, 121.9, 121.8. MS (rel. Int.)
m/z: 398 (M+, 59.0), 289 (78.9), 240 (100.0), 208 (37.2), 183 (14.4),
77 (32.9). HRMS: Calculated mass for C20H14S2Se [M]+: 397.9702,
found: 397.9703.
3-[(4-Chlorophenyl)selanyl]-2-(phenylselanyl)benzo[b]thiophene
3d: Yield: 0.096 g (80%); yellow solid, m.p. 101-102 °C. 1H NMR
(CDCl3, 400 MHz)  (ppm) = 7.73 (d, J = 7.4 Hz, 1H), 7.69 (d, J = 7.4
Hz, 1H), 7.66-7.63 (m, 2H), 7.38-7.25 (m, 5H), 7.17-7.10 (m, 4H). 13
C
NMR (CDCl3, 100 MHz)  (ppm) = 141.5, 141.4, 140.9, 134.9, 132.5,
131.1, 129.8, 129.5, 129.3, 128.9, 128.8, 125.1, 124.5, 123.6, 121.7,
121.3. MS (rel. Int.) m/z: 480 (M+, 39.3), 322 (17.7), 288 (100.0), 208
(41.9), 44 (15.0). HRMS: Calculated mass for C20H13ClSSe2 [M]+:
479.8757, found: 479.8745.
3-[(4-Methoxyphenyl)selanyl]-2-
(phenylsulfanyl)benzo[b]thiophene 3j: Yield: 0.075 g (70%); yellow
1
solid, m.p. 70-72 °C. H NMR (CDCl3, 400 MHz)  (ppm) = 7.85-7.83
6 | J. Name., 2012, 00, 1-3
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(m, 1H), 7.66-7.64 (m, 1H), 7.43-7.40 (m, 2H), 7.34-7.31 (m, 3H), 3-[(4-Chlorophenyl)selanyl]-2-(phenylsulfanyl)benzo[b]furan 5e:
View Article Online
7.28-7.25 (m, 4H), 6.72-6.68 (m, 2H), 3.70 (s, 3H). 13C NMR (CDCl3, Yield: 0.087 g (84%); yellow solid, m.p. 67-68 °C. H NMR (CDCl3,
1
DOI: 10.1039/C9NJ00526A
100 MHz)  (ppm) = 159.0, 143.0, 141.4, 140.5, 134.7, 133.2, 131.4, 400 MHz)  (ppm) = 7.80-7.78 (m, 1H), 7.68-7.66 (m, 1H), 7.46-7.44
129.2, 128.0, 125.0, 124.9, 124.4, 124.0, 121.8, 121.2, 114.9, 55.2. (m, 2H), 7.35-7.24 (m, 6H), 7.17-7.12 (m, 3H). 13C NMR (CDCl3, 100
MS (rel. Int.) m/z: 428 (M+, 91.5), 348 (52.0), 319 (100.0), 288 (49.5),
240 (76.4). HRMS: Calculated mass for C21H16OS2Se [M]+: 427.9808,
found: 427.9803.
MHz)  (ppm) = 156.3, 153.2, 133.1, 133.0, 132.1, 130.3, 130.2,
129.3, 129.26, 128.7, 127.6, 125.9, 123.7, 121.0, 112.2, 111.6. MS
(rel. Int.) m/z: 416 (M+, 100.0), 272 (81.4), 225 (60.2), 197 (72.1),
165 (41.0). HRMS: Calculated mass for C20H13ClOSSe [M]+: 415.9541,
found: 415.9543.
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3-[(4-Chlorophenyl)selanyl]-2-(phenylsulfanyl)benzo[b]thiophene
3k: Yield: 0.070 g (65%); yellow solid; m.p. 87-88 °C. 1H NMR (CDCl3,
400 MHz)  (ppm) = 7.78-7.75 (m, 1H), 7.69-7.67 (m, 1H), 7.45-7.43 3-[(4-Methoxyphenyl)selanyl]-2-(phenylsulfanyl)benzo[b]furan 5f:
(m, 2H), 7.35-7.28 (m, 5H), 7.20-7.09 (m, 4H). 13C NMR (CDCl3, 100 Yield: 0.043 g (42%); white solid, m.p. 86-87 °C. 1H NMR (CDCl3, 400
MHz)  (ppm) = 145.0, 141.2, 140.4, 134.2, 132.6, 132.0, 131.5, MHz)  (ppm) = 7.48-7.15 (m, 11H), 6.78-6.65 (m, 2H), 3.73 (s, 3H).
13C NMR (CDCl3, 100 MHz)  (ppm) = 159.3, 156.2, 151.5, 134.1,
133.7, 130.4, 129.7, 129.2, 127.2, 125.7, 123.4, 121.2, 119.9, 114.9,
114.4, 111.4, 55.2. MS (rel. Int.) m/z: 412 (M+, 82.9), 303 (100.0),
275 (66.0), 225 (23.7), 165 (33.0). HRMS: Calculated mass for
C21H16O2SSe [M]+: 412.0036, found: 412.0039.
129.8, 129.4, 129.3, 128.4, 125.2, 125.1, 124.1, 121.9, 121.6. MS
(rel. Int.) m/z: 432 (M+, 62.7), 323 (21.7), 286 (41.2), 240 (100.0),
207 (38.2), 164 (20.3), 44 (13.3). HRMS: Calculated mass for
C20H13ClS2Se [M]+: 431.9312, found: 431.9303.
2,3-bis(Phenylselanyl)benzo[b]furan 5a:32c Yield: 0.091 g (85%);
1
yellow oil. H NMR (CDCl3, 400 MHz)  (ppm) = 7.52-7.49 (m, 2H), 2-(Butylselanyl)-3-(phenylselanyl)benzo[b]furan 5g:32c Yield: 0.072
1
7.45 (dt, J = 8.2 and 0.9 Hz, 1H), 7.41 (ddd, J = 7.8, 1.4 and 0.7 Hz,
1H), 7.31-7.27 (m, 3H), 7.26-7.19 (m, 4H), 7.17-7.12 (m, 3H). 13C
g (70%); yellow oil. H NMR (CDCl3, 400 MHz)  (ppm) = 7.41 (d, J =
8.1 Hz, 1H), 7.32 (d, J = 7.5 Hz, 1H), 7.24-7.07 (m, 7H), 3.01 (t, J = 7.4
NMR (CDCl3, 100 MHz)  (ppm) = 157.2, 150.7, 132.8, 130.6, 130.4, Hz, 2H), 1.65 (quint, J = 7.4 Hz, 2H), 1.34 (sext, J = 7.4 Hz, 2H), 0.81
(t, J = 7.4 Hz, 3H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 157.0, 152.0,
132.1, 131.1, 129.9, 129.1, 126.4, 124.4, 123.4, 120.8, 120.2, 110.9,
32.8, 27.8, 22.7, 13.5. MS (rel. Int.) m/z: 410 (M+, 65.2), 273 (78.1),
242 (14.2), 194 (100.0), 164 (15.4).
130.3, 129.4, 129.2, 128.9, 127.8, 126.6, 125.3, 123.5, 120.9, 113.6,
111.4. MS (rel. Int.) m/z: 427 (M+, 5.0), 273 (57.9), 245 (82.5), 165
(100.0), 77 (23.1).
3-[(4-Chlorophenyl)selanyl]-2-(phenylselanyl)benzo[b]furan
5b:
Yield: 0.079 g (68%); yellow oil. 1H NMR (CDCl3, 400 MHz)  (ppm) = 2,3-bis(Phenylselanyl)benzo[b]selenophene 7a:32h Yield: 0.090 g
7.51-7.39 (m, 4H), 7.32-7.09 (m, 9H). 13C NMR (CDCl3, 100 MHz)  (73%); yellow solid, m.p. 95-98 °C. 1H NMR (CDCl3, 400 MHz) 
(ppm) = 157.2, 134.2, 132.9, 131.7, 130.4, 129.5, 129.4, 129.3, (ppm) = 7.79 (d, J = 8.0 Hz, 1H), 7.76-7.72 (m, 2H), 7.66 (d, J = 8.0
129.2, 128.0, 126.7, 125.5, 123.6, 121.0, 120.8, 111.5. MS (rel. Int.) Hz, 1H), 7.40-7.24 (m, 6H), 7.17-7.12 (m, 4H). 13C NMR (CDCl3, 100
m/z: 464 (M+, 47.8), 272 (100), 245 (62.5), 165 (75.7), 77 (13.7).
HRMS: Calculated mass for C20H13ClOSe2 [M]+: 463.8985, found:
463.8979.
MHz)  (ppm) = 143.9, 142.0, 136.0, 131.57, 131.56, 129.64, 129.61,
129.5, 129.4, 129.2, 126.3, 125.6, 125.2, 124.6, 124.2, 121.5. MS
(rel. Int.) m/z: 494 (M+, 50.3), 334 (100.0), 207 (37.7), 77 (20.6), 44
(16.1).
3-[(4-Fluorophenyl)selanyl]-2-(phenylselanyl)benzo[b]furan
5c:
Yield: 0.079 g (71%); yellow oil. 1H NMR (CDCl3, 400 MHz)  (ppm) = 2-(Phenylselanyl)-3-(4-tolylselanyl)benzo[b]selenophene 7b: Yield:
7.54-7.40 (m, 4H), 7.33-7.13 (m, 7H), 6.97-6.91 (m, 1H), 6.87-6.82 0.119 g (94%); yellow solid, m.p. 95-98 °C. 1H NMR (CDCl3, 400 MHz)
(m, 1H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 162.2 (d, J = 246.6 Hz),  (ppm) = 7.81-7.75 (m, 2H), 7.67 (d, J = 8.0 Hz, 1H), 7.46-7.42 (m,
157.2, 150.5, 135.6, 133.0 (d, J = 7.4 Hz), 132.7, 130.4, 129.4, 127.9, 1H), 7.39-7.35 (m, 2H), 7.30-7.15 (m, 5H), 7.00 (d, J = 8.0 Hz, 2H),
2.26 (s, 3H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 145.5, 144.0,
142.0, 136.3, 136.0, 130.5, 130.0, 129.6, 129.5, 127.6, 125.5, 125.2,
124.6, 124.2, 121.8, 110.0, 21.0. MS (rel. Int.) m/z: 508 (M+, 69.8),
351 (64.9), 336 (100), 256 (64.2), 77 (12.6). HRMS: Calculated mass
for C21H16Se3 [M]+: 507.8748, found: 507.8750.
126.7, 125.4, 124.9 (d, J = 3.3 Hz), 123.5, 120.8, 116.4 (d, J = 22.1
Hz), 111.5. MS (rel. Int.) m/z: 448 (M+, 57.7), 273 (56.0), 263 (73.7),
245 (80.5), 165 (100.0). HRMS: Calculated mass for C20H13FOSe2
[M]+: 447.9281, found: 447.9283.
3-(Phenylselanyl)-2-(phenylsulfanyl)benzo[b]furan 5d:32c Yield:
0.085 g (89%); yellow solid, m.p. 43-44 °C. 1H NMR (CDCl3, 400 MHz)
3-[(4-Chlorophenyl)selanyl]-2-
 (ppm) = 7.44 (dt, J = 8.3 and 0.8 Hz, 1H), 7.40 (ddd, J = 7.8, 1.4 and (phenylselanyl)benzo[b]selenophene 7c: Yield: 0.099 g (75%);
0.7 Hz, 1H), 7.35-7.30 (m, 4H), 7.24-7.13 (m, 8H). 13C NMR (CDCl3,
1
yellow solid, m.p. 101-102 °C. H NMR (CDCl3, 400 MHz)  (ppm) =
100 MHz)  (ppm) = 156.2, 152.7, 133.2, 130.7, 130.3, 130.1, 129,2 7.77-7.74 (m, 3H), 7.69 (d, J = 7.9 Hz, 1H), 7.47-7.36 (m, 3H), 7.31-
7.13 (m, 6H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 146.5, 143.7,
142.0, 136.1, 132.4, 130.9, 129.7, 129.6, 129.4, 129.24, 129.17,
125.31, 125.29, 124.7, 124.4, 120.9. MS (rel. Int.) m/z: 526 (M+,
(overlapped 2 signals), 129.18, 127.4, 126.8, 125.8, 123.5, 121.2,
112.7, 111.4. MS (rel. Int.) m/z: 382 (M+, 100.0), 273 (47.4), 245
(78.4), 225 (68.8), 165 (78.6).
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
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Journal Name
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Yoshimura, M. S. Yusubov and V. V. Zhdankin, Tetrahedron
14.1), 336 (39.9), 256 (27.3), 207 (100.0), 96 (15.6). HRMS:
Calculated mass for C20H13ClSe3 [M]+: 525.8208, found: 525.8209.
View Article Online
Lett., 2016, 57, 4254.
DOI: 10.1039/C9NJ00526A
3
a) Z. Li and R. Tong, J. Org. Chem., 2016, 81, 4847; b) J. P. Y.
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I. Ramakrishna, V. Bhajammanavar, S. Mallik and M. Baidya,
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Hardcastle, Org. Lett., 2003, 5, 2123; b) H. Tian, X. She, J. Xu
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3-[(4-Fluorophenyl)selanyl]-2-
(phenylselanyl)benzo[b]selenophene 7d: Yield: 0.091 g (71%);
yellow solid, m.p. 81-82 °C. 1H NMR (CDCl3, 400 MHz)  (ppm) =
7.80-7.74 (m, 3H), 7.68 (ddd, J = 7.9, 1.0, 0.6 Hz, 1H), 7.46-7.42 (m,
1H), 7.39-7.35 (m, 2H), 7.31-7.28 (m, 3H), 7.20-7.15 (m, 1H), 6.91-
6.86 (m, 2H). 13C NMR (CDCl3, 100 MHz)  (ppm) = 161.9 (d, J =
246.0 Hz), 145.8, 143.8, 142.1, 136.0, 132.01 (d, J = 7.7 Hz), 129.7,
129.5, 129.4, 129.2, 125.4, 125.2 (d, J = 3.5 Hz), 124.73, 124.66,
124.3, 116.4 (d, J = 21.9 Hz). MS (rel. Int.) m/z: 510 (M+, 100.0), 355
(78.3), 337 (60.1), 256 (62.3), 180 (24.1). HRMS: Calculated mass for
C20H13FSe3 [M]+: 509.8507, found: 509.8512.
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K. R. Reddy, P. Kannaboina and P. Das, Asian J. Org. Chem.,
2017, 6, 534.
U. Daswani, N. Dubey, P. Sharma and A. Kumar. New J.
Chem. 2016, 40, 8093.
Procedure for the Sonogashira cross-coupling between 5g and 937
To a Schlenk vial containing the mixture of 2-(butylselanyl)-3-
(phenylselanyl)benzo[b]furan 5g (0.102 g, 0.25 mmol), PdCl2(PPh3)2
(10 mol%), phenylacetylene (4 equiv) and Et3N (4.0 equiv) dissolved
in DMF (3.0 mL), was added Cu(OAc)2.H2O (20 mol%). The system
was then heated (oil bath) for 24 h at 80 °C under stirring and then
cooled to ambient temperature. The crude reaction mixture was
diluted with ethyl acetate (20 mL) and then washed with saturated
solution of NH4Cl (3X 15 mL). The organic phase was separated,
dried over MgSO4, filtered, and concentrated under vacuum. The
residue was then purified by silica-gel chromatography with hexane
as the eluent.
10 M. Kashiwa, Y. Kuwata, M. Sonoda and S. Tanimori,
Tetrahedron, 2016, 72, 304.
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Ravinder, Tetrahedron Lett., 2016, 57, 5596.
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Wadgaonkar, Res. Chem., Intermed., 2017, 43, 6875; b) K. N.
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Green Chem., 2014, 16, 3125; d) M. A. Zolfigol, K. Niknam, M.
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Rosati, J. Org. Chem., 1995, 60, 8412.
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E. J. Lenardão and C. Santi, Eur. J. Org. Chem., 2018, 1224.
15 G. Perin, D. R. Araujo, P. C. Nobre, E. J. Lenardão, R. G. Jacob,
M. S. Silva and J. A. Roehrs, Peer J. 2018, 6, e4706.
2-(Phenylethynyl)-3-(phenylselanyl)benzo[b]furan 10:33b Yield:
0.047 g (50%); yellow oil. 1H NMR (CDCl3, 400 MHz)  (ppm) = 7.56-
7.54 (m, 2H), 7.49 (d, J = 8.3 Hz, 1H), 7.45-7.43 (m, 3H), 7.38-7.35
(m, 4H), 7.26-7.19 (m, 4H). 13C NMR (CDCl3, 100 MHz)  (ppm) =
154.7, 142.4, 131.8, 130.9, 130.3, 129.7, 129.3, 129.2, 128.4, 126.8,
126.2, 123.7, 121.6, 121.1, 111.4, 110.6, 98.4, 79.1. MS (rel. Int.)
m/z: 374 (M+, 24.8), 294 (100), 293 (28.0), 163 (10.0), 77 (5.3).
16 G. Perin, D. Alves, L. F. B. Duarte, J. S. S. Neto and M. S. Silva,
Synlett, 2018, 29, 1479.
17 a) Shahjad, R. Bhargav, D. Bhardwaj, A. Mishra and A. Patra,
Macromol. Chem. Phys., 2017, 218, 1700038, b) Y. Wei, Y.
Tao, Z. Kong, L. Liu, J. Wang, W. Qiao, L. Ling and D. Long,
Energy Storage Materials, 2016, 5, 171; c) J. Wei, D. Meng, L.
Zhang and Z. Wang, Chem Asian J., 2017, 12, 1879.
Conflicts of interest
There are no conflicts to declare.
18 a) T. J. Peglow, R. F. Schumacher, R. Cargnelutti, A. S. Reis, C.
Luchese, E. A. Wilhelm and G. Perin, Tetrahedron Lett., 2017,
58, 3734; b) L. F. B. Duarte, R. L. Oliveira, K. C. Rodrigues, G.
T. Voss, B. Godoi, R. F. Schumacher, G. Perin, E. A. Wilhelm,
C. Luchese and D. Alves, Bioorg. Med. Chem., 2017, 25, 6718;
c) G. Padilha, P. T. Birmann, M. Domingues, T. S. Kaufman, L.
Savegnago and C. C. Silveira, Tetrahedron Lett., 2017, 58,
985; d) S. F. Fonseca, N. B. Padilha, S. Thurow, J. A. Roehrs, L.
Savegnago, M. N. Souza, M. G. Fronza, T. Collares, J. Buss, F.
K. Seixas, D. Alves and E. J. Lenardão, Ultrason. Sonochem.,
2017, 39, 827; e) D. Velasquez, C. Quines, R. Pistóia, G. Zeni
and C. W. Nogueira, Physiol. Behav., 2017, 170, 100.
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2017, 493, 77; b) D. Zhang, M. Wang, X. Liu and J. Zhao, RSC
Adv., 2016, 6, 94014; c) T. Ma, Q. Zhao, J. Wang, Z. Pan and J.
Chen, Angew. Chem. Int., 2016, 55, 6428; d) A. Cetin, C.
Istanbulluoglu, S. O. Hacioglu, S. C. Cevher, L. Toppare and A.
Cirpan, Polym. Sci. Part A: Polym. Chem., 2017, 55, 3705; e)
Y.-C. Pao, C.-T. Yang, Y.-Y. Lai, W.-C. Huang, C.-S Hsu and Y.-J.
Acknowledgements
The authors are grateful to CNPq and FAPERGS for the
financial support. This study was financed in part by the
Coordenação de Aperfeiçoamento de Pessoal de Nível
Superior - Brasil (CAPES) - Finance Code 001. CNPq is also
acknowledged for fellowships to G.P. and E.J.L..
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New Journal of Chemistry
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View Article Online
DOI: 10.1039/C9NJ00526A
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Regioselective synthesis of benzo[b]chalcogenophenes promoted by
Oxone®
Gelson Perin,*a Liane K. Soares,a Paola S. Hellwig,a Marcio S. Silva,a José S. S. Neto,a Juliano A. Roehrs,b
Thiago Barcellosc and Eder J. Lenardão*a
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2
Se
R
Y
R
Oxone®
2SeSe
2
Y
R
2
+ R
R
ethanol, Ar
reflux, 0.5-7 h
22 examples
Z
1
Z
R
42-95% yield
1
3 Z
:
:
S
=
5 Z = O
:
1 Z
S
Y
S Se
or
:
=
, R = C3H7
=
1
4 Z = O
:
, R = CH3 R, R2 = alkyl, aryl
7 Z Se
=
1
6 Z Se
:
=
, R = C4H9