Synthesis of bis(2-benzofuranyl) diselenides from 4-(2-hydroxyaryl)-1,2,3-selenadiazoles

Article abstract of DOI:10.1023/A:1020800401481

4-(2-Hydroxyaryl)-1,2,3-selenadiazoles obtained by the action of selenium(IV) oxide on o-hydroxyacetophenone semicarbazones are readily converted into the corresponding potassium benzofuran-2-selenolates via reaction with potassium carbonate. Oxidation of

Full text of DOI:10.1023/A:1020800401481

Russian Journal of General Chemistry, Vol. 72, No. 8, 2002, pp. 1282 1285. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 8, 2002,
pp. 1365 1368.
Original Russian Text Copyright
2002 by Petrov, Abramov, Androsov, Dehaen, Lyakhovetskii.
Synthesis of Bis(2-benzofuranyl) Diselenides
from 4-(2-Hydroxyaryl)-1,2,3-selenadiazoles
M. L. Petrov, M. A. Abramov, D. A. Androsov,
W. Dehaen, and Yu. I. Lyakhovetskii
St. Petersburg State Institute of Technology, St. Petersburg, Russia
Received December 26, 2000
Abstract 4-(2-Hydroxyaryl)-1,2,3-selenadiazoles obtained by the action of selenium(IV) oxide on
o-hydroxyacetophenone semicarbazones are readily converted into the corresponding potassium benzofuran-
2-selenolates via reaction with potassium carbonate. Oxidation of potassium benzofuran-2-selenolates with
iodine gives bis(2-benzofuranyl) diselenides in good yields.
Diaryl diselenides have long been known as
organic reagents which have found wide application
in organic synthesis, primarily in reactions with
carbanions [1]. As concerns related bis(benzofuranyl)
diselenides which are also potentially important
reagents for organic synthesis, only two furaldehyde
derivatives of bis(2- or 3-benzofuranyl) diselenides
were reported; they were obtained from 2- or 3-halo-
benzofuran-3(or 2)-carbaldehyde by the action of
sodium hydrogen selenide and subsequent oxidation
of the corresponding selenols with atmospheric
oxygen [2].
(IIb), and 4-(2-hydroxy-5-methylphenyl)-1,2,3-selena-
diazole (IIc).
1,2,3-Selenadiazoles having no substituent in
position 5 are known to decompose under the action
of strong bases (such as potassium ethoxide, butyl-
lithium, etc.). Their decomposition is accompanied by
evolution of nitrogen, leading to alkyneselenolates [6]
which are widely used in organic synthesis for pre-
paration of acetylenic selenides or in 1,3-anionic
cycloaddition and other cyclization reactions; the cor-
responding selenols are precursors of highly reactive
selenoketenes [7 12].
We recently reported on a new convenient proce-
dure for synthesizing hitherto unknown bis(2-benzo-
furanyl) diselenide [3]. The procedure is based on
decomposition of readily available 4-(2-hydroxy-
phenyl)-1,2,3-selenadiazole [4, 5] which was syn-
thesized by us previously. The present article gives
details of the synthesis of bis(2-benzofuranyl)
diselenides. By treatment with selenium(IV) oxide of
R
N
N
Se
H+
EtOK
N2
R
H
R
SeK
Se
Selenadiazoles IIa IIc readily undergo decomposi-
tion even in the presence of such a weak base as
potassium carbonate (Scheme 1). The final products,
potassium benzofuran-2-selenols VII are formed as
a result of multistep process: proton transfer in selena-
diazolylphenoxide ion III gives anion IV in which
the negative charge is localized on the heteroring;
anion IV decomposes with liberation of nitrogen
(which is typical of 4-substituted 1,2,3-selenadiazole
anions [6]) to give potassium alkyneselenolate V; the
subsequent proton transfer in V gives selenoketene
derivative VI; and the reaction is completed by intra-
molecular cyclization involving the phenolic hydroxy
group and the selenoketene fragment. The oxidation of
potassium benzofuran-2-selenolates VIIa VIIc with
iodine leads to formation of bis(2-benzofuranyl) di-
selenide (VIIIa), bis(6-methyl-2-benzofuranyl) di-
selenide (VIIIb), and bis(5-methyl-2-benzofuranyl)
diselenide (VIIIc) in good yields (Scheme 2).
2-hydroxyacetophenone,
2-hydroxy-4-methylaceto-
phenone, and 2-hydroxy-5-methylacetophenone semi-
carbazones Ia Ic in acetic acid we obtained, respec-
tively, 4-(2-hydroxyphenyl)-1,2,3-selenadiazole (IIa)
[5], 4-(2-hydroxy-4-methylphenyl)-1,2,3-selenadiazole
R1
R2
R1
R2
SeO2, AcOH
N
N
HO
H3C
HO
IIa IIc
NHCONH2
N
Se
Ia Ic
R1 = R2 = H (a); R1 = Me, R2 = H (b); R1 = H, R2 =
Me (c).
1070-3632/02/7208-1282$27.00 2002 MAIK Nauka/Interperiodica

SYNTHESIS OF BIS(2-BENZOFURANYL) DISELENIDES
1283
Scheme 1.
Scheme 2.
R2
R1
R1
R2
O
I2
VIIa VIIc
Se
Se
O
VIIIa VIIIc
HCl
O2
VIIa
SeH
Se
VIIIa
O
O
IX
X
VII, VIII, R1 = R2 = H (a); R1 = Me, R2 = H (b); R1 = H, R2 = Me (c).
An alternative procedure for synthesizing bis-
(2-benzofuranyl) diselenide (VIIIa) by neutralization
of potassium selenolate VIIa with hydrochloric acid,
followed by oxidation of the tautomeric mixture of
benzofuran-2-selenol (IX) and 3H-benzofuran-2-
selone (X) with atmospheric oxygen provides a con-
siderably lower yield of the target product (Scheme 2).
peaks whose isotope composition corresponds to the
expected one. Fragmentation of the molecular ions is
consistent with their structure. For example, the mole-
cular ion of VIIIa gives rise to two fragmentation
pathways. The first of these includes successive
expulsion of the selenium atoms, and the second
begins with cleavage of the Se Se bond to give
benzofuran-2-selenol (via hydrogen transfer) or 1,4-di-
selenine (Scheme 3). An analogous pattern is typical
of thermal transformations of diphenyl disulfide.
The structure of bis(2-benzofuranyl) diselenides
VIIIa VIIIc was confirmed by the data of 1H and 13
C
NMR and mass spectra. The IR spectra of diselenides
VIIIa VIIIc turned out to be low informative. The
expected Se Se stretching vibration band [13] is
EXPERIMENTAL
1
1
weak (453 cm ). In the H NMR spectra of VIIIa
VIIIc signals from aromatic protons are very similar
(in both position and splitting mode) to those ob-
served in the spectrum of 2-methylselenobenzofuran
[14]. The 3-H signal (furan ring) appears as a singlet
at 7.01 (VIIIa), 6.95 (VIIIb), and 6.93 ppm (VIIIc).
The corresponding signal of 2-methylselenobenzo-
furan is located at 6.8 ppm [14], and the 3-H signal
of bis(2-furyl) diselenide is observed at 6.63 ppm
The melting points were determined on a Boetius
device. The IR spectra were recorded on an IKS-29
spectrometer. The 1H and 13C NMR spectra were
obtained on a Bruker AMX-400 instrument at 400 and
100 MHz, respectively, using tetramethylsilane as
internal reference. The mass spectra were run on a
Kratos MS-890 high-resolution mass spectrometer
(70 eV, direct sample admission into the ion source
heated to 150 or 200 C). The m/z values are given
for the major 80Se isotope. The progress of reactions
was monitored by TLC on Silufol UV-254 plates;
spots were visualized with UV light and iodine vapor.
All the solvents used in this work were purified and
dehydrated by standard procedures.
1
[15]. The H NMR spectra of diselenides VIIIb and
VIIIc contain a singlet from the methyl protons at
2.44 and 2.5 ppm, respectively. The 13C chemical
shifts of VIIIa VIIIc almost coincide with those
reported for 2-methylselenobenzofuran [14] and di-
furyl diselenide [15].
Bis(2-benzofuranyl) diselenides VIIIa VIIIc show
in the mass spectra the corresponding molecular ion
4-(2-Hydroxy-4-methylphenyl)-1,2,3-selenadi-
azole (IIb) was synthesized as described in [5] for
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 8 2002

1284
PETROV et al.
Scheme 3.
+
O
Se
Se
Se, m/z 80
O
+
m/z 394
O
Se
m/z 314
O
Se, m/z 80
+
+
+
O
Se
O
SeH
O
O
O
Se
m/z 392
m/z 198
m/z 234
selenadiazole IIa [5] from 6.7 g of 2-hydroxy-4-
methylacetophenone semicarbazone (Ib), 15 ml of
glacial acetic acid, and 3.9 g of powdered sele-
nium(IV) oxide. Recrystallization from aqueous
ethanol gave 5.5 g (70%) of selenadiazole IIb as light
brown plates with mp 108 109 C, Rf 0.54 (CHCl3).
1H NMR spectrum (CDCl3), , ppm: 2.37 s (CH3),
6.8 d (5-H), 6.95 s (3-H), 7.53 d (6-H), 9.4 s [5-H in
equipped with a magnetic stirrer and reflux condenser
connected to a gas-washing bottle was protected from
light and charged with 0.4 g of 4-(2-hydroxyphenyl)-
1,2,3-selenadiazole (Ia), 5 ml of dry acetonitrile,
and 0.3 g of potassium carbonate. The mixture was
refluxed for 0.5 1 h under vigorous stirring until
gaseous products no longer evolved and initial selena-
diazole Ia disappeared (according to TLC, Rf 0.4,
eluent benzene). The mixture was cooled to 20 C,
and a solution of 0.22 g of iodine in 10 ml of aceto-
nitrile was added dropwise under vigorous stirring.
The bright cherry mixture became dark yellow. It was
stirred for 30 min, the solvent was removed on
a rotary evaporator, and the tarry residue was purified
by recrystallization from methanol. Yield of VIIIa
0.3 g (85%). Yellow crystals, mp 95 98 C, Rf 0.53
(eluent heptane CHCl3, 1:1). IR spectrum (5% solu-
2
selenadiazole, H Se satellites, J(H,77Se) = 40 Hz],
10.01 s (OH). 13C NMR spectrum (CDCl3), C, ppm:
21.31 (CH3), 113.55 (C1), 118.4 (C3), 121.3 (C5),
1
127.32 (C6), 136.7 [C5 in selenadiazole, J(CH) =
1
190 Hz, C Se satellites, J(C,77Se) = 135 Hz], 141.54
(C4), 155.46 (C2), 162.33 (C4, selenadiazole). Mass
spectrum, m/z (Irel, %): 240 (1.7) M+, 212 (8.7)
[M N2], 132 (100) [2-OH-4-CH3C6H3C CH]+.
Found, %: C 44.75, 44.91; H 3.43, 3.57. C9H8N2OSe.
Calculated, %: C 45.0; H 3.33.
1
tion in CHCl3), , cm : 3120, 3059, 2998, 2910,
1575, 1468, 1405,1340, 1300, 1230, 1158, 1145,
4-(2-Hydroxy-5-methylphenyl)-1,2,3-selenadi-
azole (IIc) was synthesized in a similar way from
6.7 g of 2-hydroxy-5-methylacetophenone semicarba-
zone (Ib), 15 ml of glacial acetic acid, and 3.9 g of
powdered selenium(IV) oxide. Recrystallization from
ethanol water gave 5.5 g (70%) of selenadiazole IIb
as light brown plates with mp 96 98 C, Rf 0.36
1
1109, 1033, 1005, 912, 873, 740, 602, 453. H NMR
spectrum (CDCl3), , ppm: 7.01 s (3-H), 7.24 t.d
(5-H), 7.34 t.d (6-H), 7.52 d (7-H), 7.55 d (4-H).
13C NMR spectrum (CDCl3), C, ppm: 111.24 (C7),
117.35 (C3), 120.86 (C4), 123.13 (C5), 125.7 (C6),
128.39 (C9), 143.08 (C2), 157.85 (C8). Mass spec-
trum, m/z (Irel, %): 394 (3.1) M+, 392 (3.0) [M 2H]+,
314 (3.4) [M Se]+, 234 (48.1) [M 2Se]+, 198 (52.8)
[benzofuran-2-selenol]+, 197 (86.3) [2-selenobenzo-
furan]+, 169 (34.4) [o-C6H4CHSe]+, 118 (100) [benzo-
furan]+, 91 (44.3) [C7H7]+. Found, %: C 46.97, 46.67;
H 2.92, 2.76. C16H10O2Se2. Calculated, %: C 46.70;
H 2.61. M 392.18.
1
(benzene). H NMR spectrum (CDCl3), , ppm: 2.34 s
(CH3), 7.03 d (5-H), 7.15 d (4-H), 7.45 s (6-H), 9.52 s
2
[5-H in selenadiazole, H Se satellites, J(H,77Se) =
40 Hz], 9.89 s (OH). 13C NMR spectrum (CDCl3),
,
C
ppm: 20.54 (CH3), 115.76 (C1), 117.89 (C3), 127.7
(C5), 129.3 (C6), 131.77 [C5 in selenadiazole,
1J(H,13C) = 190 Hz, C Se satellites, 1J(C,77Se) =
135 Hz], 137.44 (C4), 153.37 (C2), 162.26 (C4 in
selenadiazole). Mass spectrum, m/z (Irel, %): 240 (8.9)
M+, 212 (54.6) [M N2], 132 (100) [2-OH-5-CH3-
C6H3C CH]. Found, %: C 45.03, 44.88; H 3.51,
3.57. C9H8N2OSe. Calculated, %: C 45.0; H 3.33.
b. A flask equipped with a magnetic stirrer and
reflux condenser connected to a gas-washing bottle
was protected from light and charged with 0.5 g of
4-(2-hydroxyphenyl)-1,2,3-selenadiazole (Ia), 7 ml of
dry acetonitrile, and 0.36 g of potassium carbonate.
The mixture was refluxed for 0.5 1 h under vigorous
Bis(2-benzofuranyl) diselenide (VIIIa). a. A flask
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 8 2002

SYNTHESIS OF BIS(2-BENZOFURANYL) DISELENIDES
1285
stirring until gaseous products no longer evolved
and initial selenadiazole Ia disappeared (TLC, Rf 0.4,
eluent benzene). The mixture was cooled to 10 C
and neutralized with 6% hydrochloric acid, the gas-
washing bottle was removed, and the mixture was
refluxed for 30 min under vigorous stirring. It was
then cooled to 20 C, and extracted with chloroform
(3 5 ml). The organic layer was separated, washed
with calcined calcium chloride, and evaporated. The
residue was purified by column chromatography on
Chemapol L 40/100 m silica gel (150 25 mm;
eluent benzene heptane, 1:1), a fraction with Rf 0.7
(benzene heptane, 1:1) being collected. The yield of
pure diselenide VIIIa was 0.1 g (12%). The products
obtained as described in a and b were identical in
physical properties and spectral parameters.
[M 2H Se]+, 262 (15.3) [M 2Se]+, 211 (17.3)
[2-seleno-6-methylbenzofuran]+, 169 (20), 160 (34.5),
131 (13.6), 102 (48.5). Found, %: C 50.92, 51.20;
H 3.42, 3.60. C18H14O2Se2. Calculated, %: C 51.18;
H 3.32.
ACKNOWLEDGMENTS
This study was financially supported by the Rus-
sian Foundation for Basic Research (project no. 00-
03-32740).
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Bis(6-methyl-2-benzofuranyl) diselenide (VIIIb)
was synthesized as described above for compound
VIIIa using 0.48 g of 4-(2-hydroxy-4-methylphenyl)-
1,2,3-selenadiazole IIb, 15 ml of dry acetonitrile,
0.33 g of potassium carbonate, and 0.254 g of iodine
dissolved in 10 ml of acetonitrile. The tarry residue
was purified by column chromatography (20 3 cm)
using heptane chloroform as eluent. Yield of VIIIb
0.32 g (76%). Yellow crystalline substance, mp 115
1
118 C, Rf 0.68 (heptane CHCl3, 1:1). H NMR spec-
trum (CDCl3), , ppm: 2.5 s (CH3), 6.95 s (3-H),
7.08 d (5-H), 7.33 s (7-H), 7.42 d (4-H). 13C NMR
spectrum (CDCl3), C, ppm: 21.81 (CH3), 111.54 (C7),
117.51 (C3), 120.54 (C4), 124.62 (C5), 125.93 (C6),
136.25 (C9), 142.27 (C2), 158.3 (C8). Mass spectrum,
m/z (Irel, %): 422 (18.5) M+, 420 (58.2) [M 2H]+,
342 (20.1) [M Se]+, 340 (100) [M 2H Se]+, 262
(13.5) [M 2Se]+, 211 (18.7) [2-seleno-6-methyl-
benzofuran]+, 169 (24), 160 (45.8), 131 (11.5), 102
(53.7). Found, %: C 51.32, 51.21; H 3.39, 3.57.
C18H14O2Se2. Calculated, %: C 51.18; H 3.32.
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droxy-5-methylphenyl)-1,2,3-selenadiazole
(IIc),
15 ml of dry acetonitrile, 0.35 g of potassium carbo-
nate, and 0.267 g of iodine dissolved in 10 ml of
acetonitrile. The tarry residue was purified by column
chromatography (20 3 cm) using heptane chloro-
form as eluent. Yield of VIIIc 0.36 g (81%). Yellow
crystalline substance, mp 126 128 C (from benzene
1
heptane), Rf 0.55 (heptane CHCl3, 1:1). H NMR
spectrum (CDCl3), , ppm: 2.44 s (CH3), 6.93 s (3-H),
7.15 d (6-H), 7.33 s (4-H), 7.42 d (7-H). 13C NMR
spectrum (CDCl3), C, ppm: 21.29 (CH3), 110.87 (C7),
117.17 (C3), 120.75 (C4), 127.02 (C5), 128.44 (C6),
132.58 (C9), 143.01 (C2), 156.31 (C8). Mass spec-
trum, m/z (Irel, %): 422 (16.1) M+, 420 (54.3)
[M 2H]+, [M Se]+ 342 (17.2) [M Se]+, 340 (100)
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 8 2002