Direct synthesis of 2-aryl-1,3-benzoselenazoles by reaction of bis(2-aminophenyl) diselenides with aryl aldehydes using sodium metabisulfite

Article abstract of DOI:10.1016/j.tet.2012.11.091

We present here a general and easy method for the synthesis of several 2-aryl-1,3-benzoselenazoles from the reaction of bis(2-aminophenyl) diselenides with different aryl aldehydes, promoted by the non-toxic inorganic reducing agent sodium metabisulfite (Na₂S₂O₅) in DMSO at 120 °C. This efficient method furnishes in high yields the corresponding 2-aryl substituted 1,3-benzoselenazoles and tolerates a range of substituents at the aryl ring of aldehydes. The use of focused microwave irradiation decreases drastically the reaction time from 48 to 2 h.

Full text of DOI:10.1016/j.tet.2012.11.091

Tetrahedron 69 (2013) 1316e1321
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Direct synthesis of 2-aryl-1,3-benzoselenazoles by reaction of
bis(2-aminophenyl) diselenides with aryl aldehydes using sodium
metabisulfite
C aꢀ tia Schwartz Radatz , Diego Alves ,*, Paulo Henrique Schneider
a
b
a,
*
a
Instituto de Química, Universidade Federal do Rio Grande do Sul, UFRGS, PO Box 15003, 9150-970 Porto Alegre, RS, Brazil
LASOL, CCQFA, Universidade Federal de Pelotas, UFPel, PO Box 354, 96010-900 Pelotas, RS, Brazil
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 October 2012
Received in revised form 26 November 2012
Accepted 27 November 2012
Available online 5 December 2012
We present here a general and easy method for the synthesis of several 2-aryl-1,3-benzoselenazoles from
the reaction of bis(2-aminophenyl) diselenides with different aryl aldehydes, promoted by the non-toxic
ꢀ
inorganic reducing agent sodium metabisulfite (Na
2
S
2
O
5
) in DMSO at 120 C. This efficient method
furnishes in high yields the corresponding 2-aryl substituted 1,3-benzoselenazoles and tolerates a range
of substituents at the aryl ring of aldehydes. The use of focused microwave irradiation decreases dras-
tically the reaction time from 48 to 2 h.
Keywords:
Ó 2012 Elsevier Ltd. All rights reserved.
1,3-Benzoselenazoles
Diselenides
Aldehydes
Heterocycles
Reducing agent
1. Introduction
via the phenylselenourea intermediate (Eq. 1, Scheme 1). More re-
cently, 2-thio-organyl-1,3-benzoselenazoles were prepared in
moderated yields from 2-halophenyl isothiocyanates in reactions
1
Substituted benzoheteroazole units, particularly benzoxazoles,
benzothiazoles2 and benzimidazoles, are privileged heterocyclic
systems because of their great reactivities, notable chemical prop-
erties and biological activities. Specially, the synthesis of 2-
substituted 1,3-benzothiazoles has attracted much attention not
only in synthetic chemistry but also in medicinal and industrial
3
using firstly n-BuLi and elemental selenium, and furtheralkyl halides
(Eq. 2, Scheme 1).
6
e
2
fields. Their different applications range from antitumoral, antidi-
abetic and antituberculotics agents, to chemiluminescent and pho-
tosensitizer agents.2 Therefore, diverse synthetic methods have
g,4
5
been developed for the synthesis of these compounds. However, in
6
the case of selenium analogues, there are few reports on the
preparation of the 2-substituted benzoselenazoles and this kind of
6
c
heterocyclic compounds despite their potential importance. In-
terest in the chemistry and application of different selenium-
7
containing compounds as potential pharmaceuticals, new mate-
8
9
10
rials, ionic liquids and catalysts has expanded rapidly during the
last years. For example, selenium-containing heterocycles, including
1
,3-selenazoles11 have biological activities7,12 and some 1,3-
benzoselenazole derivatives are used as cyanine dyes.
13
In the context of the synthesis of 1,3-benzoselenazoles, Sashida
and co-workers6d synthesized 2-amino-1,3-benzoselenazoles by the
copper-catalyzed reaction of 2-iodoanilines with isoselenocyanates
*
Corresponding authors. E-mail address: paulos@iq.ufrgs.br (P.H. Schneider).
Scheme 1. Synthesis of 2-substituted-1,3-benzoselenazoles.
0
040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.11.091

C.S. Radatz et al. / Tetrahedron 69 (2013) 1316e1321
1317
In other study, Kambe and co-workers described the synthesis
Table 1
Optimization of the reaction conditions
of 1,3-benzoselenazoles having a heteroatom substituent at the 2-
position by the copper-catalyzed reaction of 2-halophenyl iso-
cyanides with elemental selenium and heteroatom nucleophiles
6c
(
Eq. 3, Scheme 1). In addition, these authors described the syn-
thesis of 2-phenyl-1,3-benzoselenazoles by nickel-catalyzed cross-
coupling reaction of thus-formed 2 arylthio-1,3-benzoselenazole
with PhMgBr.6c One of the most simple protocol for the synthesis
Entry
Diselenide (equiv)
Na
2
S
2
O
5
(equiv)
Time (h)
Yield (%)a
1
2
3
4
5
6
0.5
0.5
0.5
0.5
1.0
0.5
0.5
1.0
1.0
1.0
1.0
1.0
0.5
1.0
72b
24
48
72
48
48
48
n.d.
64
91
90
92
69
10
of 2-aryl-1,3-benzoselenazole ring is the reaction of zinc bis(o-
6
a
aminophenylselenolate) with acid chlorides. Consequently, the
development of a simple and direct methodology for the synthesis
of 2-aryl-1,3-benzoselenazoles, remains a significant challenge in
heterocyclic chemistry.
c
7
Recently, a straight approach for the synthesis of 2-aryl-1,3-
benzothiazoles was described, where the reaction of substituted
bis(2-aminoaryl) disulfides and aryl aldehydes was promoted by
a
Yields are given for pure isolated products.
Reaction was performed at room temperature.
Reaction was performed on air atmosphere.
b
c
14
sodium metabisulfite (Na
2 2 5
S O ). Besides, this inexpensive and
non-toxic inorganic salt can also be used in the synthesis of ben-
14
15
to 1.0 equiv did not alter the yield of the reaction (Table 1, entry 5).
On the other hand, when the reaction was performed using
0.5 equiv of Na S O , product 3a was obtained in moderate 69%
yield (Table 1, entry 6). Finally, we conducted the reaction under air
atmosphere and only 10% yield of product 3a was obtained con-
firming that the presence of inert atmosphere is essential for the
reaction (Table 1, entries 3 vs 7).
zothiazoles, benzimidazoles and in chlorotelluration of terminal
alkynes.16 This fact and according to our continuous interest in the
17
2
2 5
synthesis of organoselenium compounds, prompted us to explore
another approach for the synthesis of substituted 2-aryl-1,3-
benzoselenazoles from bis(2-aminophenyl) diselenides and aryl
2 2 5
aldehydes, using Na S O in DMSO under conventional heating or
focused microwave irradiation (Scheme 1).
In an optimized reaction, bis(2-aminophenyl) diselenide 1a
(
0.5 equiv) was reacted with 4-nitrobenzaldehyde 2a (1.0 equiv)
2
. Results and discussion
using Na
2
S
2
O
5
(1.0 equiv) and DMSO (3.0 mL), under nitrogen at-
ꢀ
mosphere at 120 C during 48 h, afforded 2-(4-nitrophenyl)-1,3-
benzoselenazole 3a in 91% yield.
Our procedure begins with the synthesis of the starting material
bis(2-aminophenyl) diselenide 1a, which was performed according
to a procedure recently described by Braga and co-workers.
Treating 2-iodoaniline with n-BuLi, subsequent trapping of the
lithium anion with elemental selenium and potassium ferrocyanide
oxidation, affords the corresponding diselenide 1a in 88%
After optimization, the reaction of different bis(2-aminoaryl)
diselenides 1a,b with a range of aryl aldehydes 2aeh was in-
vestigated to check the versatility of the protocol, and the results
are summarized in Table 2. In general, all reactions proceeded
smoothly furnishing the desired products in good yields.
Several aryl aldehydes were reacted with bis(2-aminophenyl)
diselenide 1a furnishing the corresponding 2-aryl-1,3-benzo-
selenazoles 3aej in moderate to excellent yields (Table 2, entries
18
yield (Scheme 2).
Table 2
Scope of the direct synthesis of 2-aryl-1,3-benzoselenazoles prompted by sodium
metabisulfite
Scheme 2. Synthesis of bis(2-aminophenyl) diselenide 1a.
Having obtained the diselenide 1a, we concentrated our efforts
on the synthesis of the target molecules. Our initial studies were
focused on the development of an optimum set of reaction condi-
tions. The reaction between bis(2-aminophenyl) diselenide 1a and
Entry
1
Diselenide
Aldehyde
Product (yield)a
4
-nitrobenzaldehyde 2a was selected as a model reaction, using
3
a (91%)
Na
2
S
2
O
5
as the reducing agent and DMSO as solvent.
1a
2
a
In
a
first experiment, bis(2-aminophenyl) diselenide 1a
(
0.5 mmol), 4-nitrobenzaldehyde 2a (1.0 mmol), Na
2 2 5
S O
(
1.0 mmol), were reacted in DMSO (3.0 mL) at room temperature
2
3
4
1a
and under these conditions, even after 72 h, no formation of the
product was observed (Table 1, entry 1). When the reaction tem-
perature was increased to 120 C for 24 h the reaction proceeded
smoothly, furnishing the desired substituted 2-phenyl-1,3-
benzoselenazole 3a in 64% yield (Table 1, entry 2). To our delight,
raising the reaction time to 48 h, afforded the desired product 3a in
excellent yield (Table 1, entry 3). Furthermore, when the reaction
was performed in 72 h, no change in the yield was observed
3
b (88%)
2b
ꢀ
1a
1a
3c (76%)
2
c
(Table 1, entry 4).
Using the best conditions of temperature and time, we next
investigated some parameters regarding the stoichiometry. At first
we observed that increasing the amount of diselenide 1a from 0.5
3
d (80%)
2
d
(continued on next page)

1318
C.S. Radatz et al. / Tetrahedron 69 (2013) 1316e1321
Table 2 (continued )
In order to compare the steric effects, reactions were performed
Product (yield)a
with aldehydes containing hydroxyl group in para and ortho posi-
tions and to our satisfaction, good yields were obtained in both
cases, demonstrating that sterically demanding ortho substituent
did not affect the reaction course (Table 2, entries 3, 4). When the
benzaldehyde was used, the desired product 2-phenyl-1,3-
benzoselenazole 3e was obtained in 83% yield (Table 2, entry 5).
To expand the synthetic scope of this protocol, we carried out the
reactions using bis(2-amino-4-chlorophenyl) diselenide 1b. In-
terestingly, despite electron-withdrawing nature of the chloride
group in the diselenide 2b, the yields of 2-aryl-1,3-benzoselenazoles
were not greatly reduced and the reactions worked well using al-
dehydes 2a and 2e (Table 2, entries 9, 10).
Entry
5
Diselenide
Aldehyde
1a
1a
1a
3
e (83%)
2
e
6
7
8
9
3f (68%)
2f
Over recent years, it has been shown that the organic reactions
19
can be influenced also by microwave irradiation (MW). In all these
cases, the authors demonstrated that the use of MW irradiation can
considerably decrease the reaction time often accompanied
3
g (62%)
2
g
19,20
with increase of the product yields.
Therefore, the synthesis
of 2-aryl-1,3-benzoselenazoles from the reaction of bis(2-amino-
phenyl) diselenide 1a with aryl aldehydes promoted by
1a
Na
2 2 5
S O was evaluated also under focused microwave irradiation
2
h
3h (88%)
(Table 3).
2a
2e
Table 3
Optimization of the reaction conditions under microwave irradiation
3
i (89%)
1
b
10
1b
3
j (80%)
a
Yields are given for pure isolated products.
ꢀ
Yield (%)a
Entry
Temperature ( C)
Time (h)
1
2
3
4
5
6
120
180
200
120
120
120
1.0
1.0
1.0
1.5
2.0
2.5
60
60
61
76
90
90
1
e8). Upon analysis of Table 2, it can be verified that the electronic
effects on the aldehyde moiety seems to have a significant influence
on the product yield. For example, aldehydes with electron-
withdrawing groups at the aromatic ring gave better results than
those with electron-donating groups (Table 2, entries 1, 2 and 8
vs 6e7). This can be explained by the activation of the carbonyl
group of the aldehyde by electron-withdrawing groups, facilitating
the nucleophilic attack of the nitrogen atom of the amine, to form
the intermediate imine (see the plausible reaction mechanism,
Fig. 1).
a
Yields are given for pure isolated products.
At first, reaction of diselenide 1a (0.15 equiv) with aryl alde-
hyde 2a (0.3 equiv) using Na S O (0.3 equiv) and DMSO (0.7 mL)
as solvent was performed under microwave irradiation at 120
2
2 5
ꢀ
C
and product 3a was formed in 60% yield after 1.0 h (Table 3, entry
Fig. 1. Plausible reaction mechanism for the formation of 2-aryl-1,3-benzoselenazole 3.

C.S. Radatz et al. / Tetrahedron 69 (2013) 1316e1321
1319
1
). This temperature was measured with an IR sensor on the outer
To demonstrate the generality of MW experiments, we prepared
a series of benzoselenazoles 3aeh undermicrowave irradiation (Table
4). In most cases, the reactions proceeded smoothly to give desired
product in good to excellent yields. A structurally diverse range of aryl
aldehydes were converted to corresponding benzoselenazoles in
good yields (Table 4, entries 1e8). The resultsdepicted inTable 4 show
that the use of MW irradiation (Method B) is better than conventional
heating (Table 2, Method A), furnishing the corresponding products in
comparable yields but in very short reaction time.
surface of the reaction vial. Encouraged by this result, we decided
to explore the benefits of fast heating of the microwave irradiation
and performed some experiments under different temperatures.
Unfortunately, increasing the temperature to 180 and 200 C, did
not produce significant changes in the yields of desired product 3a
ꢀ
(
Table 3, entries 2, 3). After that, we fixed the temperature in
ꢀ
120 C and investigate if the time could improve the success of the
reaction. When the reaction was carried out in 1.5 h the benzo-
selenazole 1a was obtained in 76% yield (Table 3, entry 4). To our
satisfaction, by increasing the reaction time to 2.0 h we observe
a significative improvement, and the desired product was ob-
tained in excellent 90% yield (Table 3, entry 5). Extending the time
to 2.5 h did not influence the yield (Table 3, entry 6).
After optimization, the reaction between bis(2-aminophenyl)
diselenide 1a and a set of different aldehydes was investigated to
check the versatility of the protocol, and the results are summa-
rized in Table 4.
On the basis of these results and on previous reports about the
14
use of an oxidizing media, a possible mechanism for the synthesis
of 2-aryl-1,3-benzoselenazole can be proposed (Fig. 1). We believe
that the amino group of bis(2-aminophenyl) diselenide 1 initially
reacts with the aryl aldehyde 2 to form the imine diselenide com-
pound denoted A. To confirm our hypothesis we performed a con-
trol experiment and this compound A could be observed and
1
confirmed by H NMR analysis. Next, the SeeSe bond was cleaved
$ꢁ
2ꢁ
14d
by the radical anion SO2 generated form S O
by heating, to
2
5
afford the intermediates B and C. The intermediate B can be
reoxidized to starting imine diselenide A, and the radical C un-
dergoes to the intramolecular cyclocondensation leading to the
aminyl radical D. Finally, further oxidation of intermediate D pro-
vides the target product 3.
Table 4
Scope of the direct synthesis of 2-aryl-1,3-benzoselenazoles prompted by sodium
metabisulfite using MW Irradiation
3. Conclusion
Entry
1
Aldehyde
Product (yield)
Yield (%)a
90
In conclusion, we have presented here an efficient methodology
for the direct synthesis of substituted 2-aryl-1,3-benzoselenazoles
in moderated to excellent yields. The condensations of bis(2-
aminophenyl) diselenides with a range of substituted aryl alde-
hydes were promoted by the non-toxic inorganic reducing agent
3
a
2
a
ꢀ
sodium metabisulfite in DMSO at 120 C. Another benefit of the
described procedure is that the protocol minimizes the energy
demands and the reaction time could be reduced from 48 to only
2 h using focused MW irradiation. Furthermore, studies of photo-
physical properties of the synthesized compounds are in progress
in our laboratory.
2
3
90
80
3
b
2
b
4
4
. Experimental section
.1. General remarks
3
c
2
c
The sodium metabisulfite (Na
Reagen and used without further purifications. Dimethylsulfoxide
2
S
2
O
5
)
was purchased from
Ò
4
5
6
84
79
67
(
DMSO) was obtained from Sigma Aldrich and dried through clas-
21
2
d
3d
sical method. The reactions were monitored by thin-layer chro-
matography (TLC) and column chromatography was performed
using Merck silica gel (230e400 mesh). Nuclear magnetic reso-
nance spectra were obtained on Varian Inova 300 and Bruker 400
spectrometer. Chemical shifts are given in parts per million (
are referenced from tetramethylsilane (TMS) in H NMR spectra
3
e
d
) and
2
e
1
13
3 3 2
and from CDCl or (CD ) CO in C NMR spectra. ATR/FTIR spectra
were recorded on a Varian FTIR-640 spectrometer. Low-resolution
mass spectra were obtained with a Shimadzu GCeMS-QP5050
mass spectrometer interfaced with a Shimadzu GC-17A gas chro-
matograph equipped with a DB-17 MS capillary column. The Mi-
crowave experiments were conducted using a CEM Discover, mode
operating systems working at 2.45 GHz, with a power pro-
grammable from 1 to 300 W.
3f
2
f
7
8
60
92
3
g
2
g
4
2
.2. General procedure for the synthesis of substituted
-phenylbenzoselenazoles
The appropriatebis(2-aminoaryl) diselenide 1a or 1b (0.5 mmol),
2
h
3h
substituted aryl aldehyde 2aeh (1.0 mmol) and Na
2 2 5
S O (1.0 mmol)
a
Yields are given for pure isolated products.
were dissolved in anhydrous DMSO (3 mL). The resulting reaction

1320
C.S. Radatz et al. / Tetrahedron 69 (2013) 1316e1321
ꢀ
mixture was stirred under nitrogen atmosphere at 120 C for 48 h.
After this time, the mixturewas cooled to room temperature, diluted
J¼8.1 Hz); 7.93e7.97 (m, 3H); 7.51 (t, 1H, J¼7.3 Hz); 7.29-7.35 (m,
13
3H); 2.44 (s, 3H). C NMR (75.5 MHz, CDCl
3
) d: 173.2, 156.5, 142.2,
with saturated aq NH
4
Cl (20 mL) and washed with ethyl acetate
and
138.8, 134.2, 130.4, 126.9, 125.7, 125.4, 125.3, 128.6, 22.2. IR (KBr) n:
þ
(
3ꢂ20 mL). The organic phase was separated, dried over MgSO
4
1604, 1490, 1432, 1305, 1220, 937, 815, 754. MS m/z: 273 m/z (M ).
Anal. calcd for C14 11NSe (273.01): C 61.77, H 4.07, N 5.15; found: C
61.64, H 4.00, N 5.06.
concentrated under vacuum. The residue was purified by flash
chromatography on silica gel using hexanes/AcOEt (95:5) as eluent
to give substituted 2-phenylbenzoselenazoles 3aej.
H
4
.2.8. 2-(3,4-Difluorophenyl)benzo[d][1,3]selenazole (3h). Yield:
ꢀ
1
4
.2.1. 2-(4-Nitrophenyl)benzo[d][1,3]selenazole (3a). Yield: 0.277 g
0.260 g (88%); yellow solid; mp 94e97 C. H NMR (300 MHz,
CDCl
: 8.14 (d, 1H, J¼8.0 Hz); 7.91e7.98 (m, 2H); 7.73e7.78 (m,
1H); 7.54 (t, 1H, J¼7.8 Hz); 7.30e7.40 (m, 2H). C NMR (75.5 MHz,
CDCl 171.7, 156.1, 154.5 (d,
CeF¼12.9 Hz), 153.0 (d,
ꢀ
1
(
91%); yellow solid; mp 147e148 C. H NMR (300 MHz, CDCl
3
)
d:
3
) d
13
8
.27 (d, 2H, J¼8.7 Hz); 8.10 (d, 3H, J¼8.7 Hz); 7.92 (d,1H, J¼8.0); 7.47
13
(
1
t, 1H, J¼7.5 Hz); 7.32 (t, 1H, J¼7.6 Hz). C NMR (75.5 MHz, CDCl
3
)
d:
3
)
d
:
J
69.9, 156.2, 149.6, 142.1, 139.6, 129.3, 127.6, 126.9, 126.2, 125.7,
25.0. IR (KBr) : 1592, 1521, 1342, 1211, 1141, 943, 854, 769. MS m/z:
Se (303.98): C 51.50, H
J
CeF¼13.2 Hz), 151.1 (d, JCeF¼12.9 Hz), 149.7 (d, JCeF¼12.9 Hz),
1
3
2
n
145.2, 139.1, 130.4 (d, JCeF¼77.4 Hz), 126.9 (d, JCeF¼76.6 Hz), 125.6
04 m/z (Mþ). Anal. calcd for C13
8 2 2
H N O
(d, JCeF¼10.9 Hz), 118.6 (d, JCeF¼18.0 Hz), 117.3 (d, JCeF¼19.0 Hz). IR
.66, N 9.24; found: C 51.97; H 2.63; N 9.30.
(KBr)
n
: 1606, 1500, 1427, 1309, 1268, 1106, 977, 757, 634. MS m/z:
þ
2
95 m/z (M ). Anal. calcd for C13
H
7
F
2
NSe (294.97): C 53.08, H
4
.2.2. 2-(4-Bromophenyl)benzo[d][1,3]selenazole (3b). Yield: 0.296 g
2.40, N 4.76; found: C 55.07, H 2.48, N 4.13.
ꢀ
1
(
88%); white solid; mp 124e126 C. H NMR (300 MHz, CDCl
3
)
d: 8.01
(
2
d,1H, J¼8.1 Hz); 7.84 (d,1H, J¼8.0 Hz); 7.78 (d, 2H, J¼8.2 Hz); 7.52 (d,
4.2.9. 5-Chloro-2-(4-nitrophenyl)benzo[d][1,3]selenazole (3i). Yield:
13
ꢀ
1
H, J¼8.3 Hz); 7.41 (t, 1H, J¼7.2 Hz); 7.24 (t, 1H, J¼7.3 Hz). C NMR
: 171.6, 156.3, 139.0, 135.7, 132.9, 130.0, 127.2,
0.301 g (89%); yellow solid; mp 158e160 C. H NMR (300 MHz,
CDCl
: 8.26 (d, 2H, J¼8.8 Hz); 8.08 (d, 2H, J¼8.3 Hz), 8.06 (s, 1H);
7.81 (d, 1H, J¼8.5 Hz); 7.28 (dd, 1H, J¼8.4 Hz, J¼2.1 Hz). C NMR
(75.5 MHz, CDCl : 171.3, 156.7, 149.4, 141.3, 137.2, 133.2, 128.9,
(
75.5 MHz, CDCl
3
)
d
3
) d
13
1
1
26.2,126.1,125.6,125.5. IR (KBr)
064, 937, 825, 752. MS m/z: 337 m/z (M ). Anal. calcd for C13
n
: 1510,1475,1432,1392,1303,1216,
þ
8
H BrNSe
3
) d
(
336.90): C 46.32, H 2.39, N 4.16; found: C 46.68, H 2.30, N 5.65.
126.8,125.9,125.4,124.6. IR (KBr)
MS m/z: 338 m/z (M ). Anal. calcd for C13
n
: 1598,1515,1340,1068, 848, 611.
ClN Se (337.94): C
þ
H
7
2 2
O
4
.2.3. 4-(Benzo[d][1,3]selenazol-2-yl)phenol (3c). Yield: 0.209
g
46.25, H 2.09, N 8.30; found: C 50.34, H 2.76, N 6.70.
ꢀ
1
(
(
76%); dark orange solid; mp 212e213 C. H NMR (400 MHz,
CD CO)
: 9.04 (s, 1H); 7.93 (d, 1H, J¼8.0 Hz); 7.86 (d, 1H,
3
)
2
d
4.2.10. 5-Chloro-2-phenylbenzo[d][1,3]selenazole (3j). Yield: 0.234 g
ꢀ
1
J¼8.0 Hz); 7.81 (d, 2H, J¼8.6 Hz); 7.35 (t, 1H, J¼7.3 Hz); 7.17 (t, 1H,
(80%); yellow solid; mp 138e140 C. H NMR (300 MHz, CDCl
3
) d:
13
J¼7.2 Hz); 6.86 (d, 2H, J¼8.6 Hz). C NMR (100 MHz, (CD
3 2
) CO) d:
8.09 (d, 1H, J¼2.0 Hz); 7.98e8.01 (m, 2H), 7.83 (d, 1H, J¼8.4 Hz),
1
3
1
72.4, 161.1, 156.7, 138.4, 130.2, 128.6, 126.9, 125.7, 125.5, 124.7,
7.45e7.52 (m, 3H), 7.29 (dd, 1H, J¼8.4 Hz, J¼2.1 Hz). C NMR
(75.5 MHz, CDCl : 175.2, 164.4, 157.4, 136.9, 136.5, 133.1, 132.1,
129.8, 128.7, 126.2, 125.3. IR (KBr)
116.6. IR (KBr)
n
: 3434, 1604, 1484, 1432, 1292, 1218, 1172, 833, 756.
3
) d
þ
MS m/z: 275 m/z (M ). Anal. calcd for C13
H 3.31, N 5.11; found: C 56.60, H 2.80, N 5.05.
H
9
NOSe (274.98): C 56.95,
n
: 1625, 1477, 1427, 1255, 1062,
þ
883, 759, 686. MS m/z: 293 m/z (M ). Anal. calcd for C13
H
8
ClNSe
(292.95): C 53.36, H 2.76, N 4.79; found: C 53.22, H 2.19, N 4.80.
4
.2.4. 2-(Benzo[d][1,3]selenazol-2-yl)phenol (3d). Yield: 0.220
g
ꢀ
1
(
80%); white solid; mp 128e130 C. H NMR (300 MHz, CDCl
3
)
d:
4.3. General procedure for the synthesis of substituted
2-phenylbenzoselenazoles under microwave irradiation
1
1
2.57 (s, 1H); 8.01 (d, 1H, J¼8.1 Hz); 7.92 (d, 1H, J¼8.1 Hz); 7.55 (d,
H, J¼7.8 Hz); 7.49 (t, 1H, J¼7.7 Hz); 7.31e7.41 (m, 2H); 7.09 (t, 1H,
1
3
J¼8.3 Hz); 6.95 (t, 1H, J¼7.7 Hz). C NMR (75.5 MHz, CDCl
3
)
d
: 174.7,
In a 10 mL glass vial equipped with a small magnetic stirring bar,
the bis(2-aminophenyl) diselenide 1a (0.15 mmol), substituted aryl
157.9, 154.2, 136.4, 133.5, 130.8, 127.4, 126.6, 125.3, 124.4, 120.4,
1
19.9, 118.4. IR (KBr)
n
: 3448, 1616, 1581, 1483, 1384, 1263, 1201, 798.
2 2 5
aldehyde (0.3 mmol) and Na S O (0.3 mmol) were dissolved in
anhydrous DMSO (0.7 mL) and the vial was tightly sealed with an
þ
MS m/z: 275 m/z (M ). Anal. calcd for C13
H
9
NOSe (274.98): C 56.95,
H 3.31, N 5.11; found: C 54.40, H 3.26, N 5.36.
aluminum/Teflon crimp top. The mixture was then irradiated in
a microwave reactor (CEM Explorer) for 2.0 h at 120 C (tempera-
ꢀ
4
.2.5. 2-Phenylbenzo[d][1,3]selenazole (3e). Yield: 0.215 g (83%);
ture was measured with an IR sensor on the outer surface of the
reaction vial), using an irradiation power of 100 W and pressure of
17.2 bar (the ramp temperature rate was 35 s). After the reaction
was complete, the reaction mixture was diluted with saturated aq
ꢀ
1
yellow solid; mp 114e116 C. H NMR (300 MHz, CDCl
1
3
) d: 8.03 (d,
H, J¼8.1 Hz); 7.91e7.94 (m, 2H); 7.84 (d, 1H, J¼7.9 Hz); 7.40e7.42
13
(
1
m, 4H); 7.22 (t, 1H, J¼7.5 Hz). C NMR (75.5 MHz, CDCl
3
) d: 173.2,
65.4, 156.4, 138.9, 136.8, 131.7, 129.7, 128.6, 127.0, 125.9, 125.5. IR
NH
4
Cl (20 mL) and washed with ethyl acetate (3ꢂ20 mL). The or-
(
KBr)
n
: 1587, 1552, 1510, 1479, 1430, 1299, 1216, 939, 763. MS m/z:
ganic phase was separated, dried over MgSO
4
and concentrated
þ
2
5
59 m/z (M ). Anal. calcd for C13
H
9
NSe (258.99): C 60.48, H 3.51, N
under vacuum. The residue was purified by flash chromatography
on silica gel using hexane/AcOEt (95:5) as eluent, yielding the
products.
.43; found: C 60.09, H 3.07, N 5.35.
4
.2.6. 2-(4-Methoxyphenyl)benzo[d][1,3]selenazole (3f). Yield: 0.196 g
ꢀ
1
(68%); orange solid; mp 122e124 C. H NMR (300 MHz, CDCl
3
)
d:
Acknowledgements
7
.97 (d, 1H, J¼8.1 Hz); 7.81e7.89 (m, 3H); 7.38 (t,1H, J¼7.3 Hz); 7.19 (t,
13
1
H, J¼7.5 Hz); 6.90 (d, 2H, J¼8.5 Hz); 3.80 (s, 3H). C NMR (75.5 MHz,
: 172.7, 162.6, 156.6, 138.7, 130.2, 129.7, 126.9, 125.4, 125.0,
15.0, 56.2. IR (KBr) : 1600,1496,1434,1259,1168,1024, 831, 765. MS
m/z: 289 m/z (M ). Anal. calcd for C14 11NOSe (289.00): C 58.34, H
.85, N 4.86; found: C 58.12, H 3.48, N 4.67.
We are grateful to the CAPES, CNPq, INCT-CMN and FAPERGS
(PRONEM 11/2024-9) for financial support. C.S.R. thanks CNPq for
her Ph.D. fellowship.
3
CDCl ) d
1
n
þ
H
3
Supplementary data
4
.2.7. 2-p-Tolylbenzo[d][1,3]selenazole (3g). Yield: 0.169 g (62%);
Electronic Supplementary data (ESI) available: experimental
ꢀ
1
1
13
yellow solid; mp 78e80 C. H NMR (300 MHz, CDCl
3
)
d: 8.13 (d, 1H,
procedures, details H and
C NMR, IR and mass spectra.

C.S. Radatz et al. / Tetrahedron 69 (2013) 1316e1321
1321
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2012.11.091.
L. V.; Almeida, P.; Lynch, D. E. CrystEngComm 2011, 13, 1333; (c) Conley, N. R.;
Dragulescu-Andrasi, A.; Rao, J.; Moerner, W. E. Angew. Chem., Int. Ed. 2012, 51, 1.
. (a) Kim, H. S.; Kim, Y. J.; Lee, H.; Park, K. Y.; Lee, C.; Chin, C. S. Angew. Chem.,
Int. Ed. 2002, 41, 4300; (b) Lenard a~ o, E. J.; Feij oꢀ , S.; Thurow, J. O.; Perin, G.;
Jacob, R. G.; Silveira, C. C. Tetrahedron Lett. 2009, 50, 5215; (c) Lenard a~ o, E. J.;
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