Rapid oxidation of selenides, selenoxides, tellurides, and telluroxides with aqueous sodium hypochlorite

Article abstract of DOI:10.1080/10426500307909

A simple and convenient procedure for the rapid oxidation of a variety of selenides, selenoxides, tellurides, and telluroxides with aqueous sodium hypochlorite to selenones and tellurones, respectively, has been reported in dimethylformamide at ambient te

Full text of DOI:10.1080/10426500307909

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Phosphorus, Sulfur, and Silicon and the Related
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Rapid Oxidation of Selenides, Selenoxides, Tellurides,
and Telluroxides with Aqueous Sodium Hypochlorite
Jitender M. Khurana a , Bhaskar M. Kandpal a & Yogendra K. Chauhan a
a Department of Chemistry, University of Delhi, Delhi, India
Version of record first published: 27 Oct 2010.
To cite this article: Jitender M. Khurana, Bhaskar M. Kandpal & Yogendra K. Chauhan (2003): Rapid Oxidation of Selenides,
Selenoxides, Tellurides, and Telluroxides with Aqueous Sodium Hypochlorite, Phosphorus, Sulfur, and Silicon and the Related
Elements, 178:6, 1369-1375
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Phosphorus, Sulfur, and Silicon, 178:1369–1375, 2003
C
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print
DOI: 10.1080/10426500390200684
RAPID OXIDATION OF SELENIDES, SELENOXIDES,
TELLURIDES, AND TELLUROXIDES WITH
AQUEOUS SODIUM HYPOCHLORITE
Jitender M. Khurana, Bhaskar M. Kandpal,
and Yogendra K. Chauhan
Department of Chemistry, University of Delhi, Delhi, India
(Received October 14, 2002; accepted December 7, 2002)
A simple and convenient procedure for the rapid oxidation of a variety of
selenides, selenoxides, tellurides, and telluroxides with aqueous sodium
hypochlorite to selenones and tellurones, respectively, has been reported
in dimethylformamide at ambient temperature.
Keywords: Aq. sodium hypochlorite; selenides; selenoxides; tellurides;
telluroxides
The organic chemistry of the group 6a elements selenium and tellurium
has been actively investigated.1 Many organo selenium and tellurium
compounds are useful reagents or synthons in organic synthesis.2 The
chemistry of selenoxides and selenones is of particular interest owing
to their synthetic usefulness, their thermal instability (fragmentation
with olefin formation3), and their ability to stabilize adjacent anionic
centers.4 The chemistry of tellurium oxides is also important. Among
these, the oxidizing potential of di(p-methoxyphenyl) telluroxide5 and
c
di(p-methyloxyphenyl) tellurone,2b toward some functional groups
has been reported. As for synthesis, most of the earlier literature has re-
ported two step synthesis of diaryl,6 aryl alkyl,7 and dialkyl selenones.8
The methods are limited to some specific cases and many of them have
been the subject of controversy.7,9 Furthermore diaryl and dialkyl tel-
lurone, the tellurium analogues of the well known sulphones, are not
well defined compounds and have not received much attention. It is
The authors are thankful to UGC, New Grant for financial grant [Project No. F-12-
120/2001 (SR-I)] and BMK is grateful to CSIR, New Delhi, India for grant of Junior
Research Fellowship (JRF).
Address correspondence to Jitender M. Khurana, Department of Chemistry, Univer-
sity of Delhi, Delhi 110007, India. E-mail: jmkhurana@chemistry.du.ac.in
1369

1370
J. M. Khurana et al.
doubtful whether a compound corresponding to the formula R2TeO2
has ever been obtained in pure form.2 In view of the importance of
these compounds, we decided to investigate if inexpensive aq. sodium
hypochlorite solution10 could be used for the oxidation of selenides, se-
lenoxides, tellurides, and telluroxides.
RESULTS AND DISCUSSION
This is the first report on the rapid oxidation of a variety of selenides
(1) and selenoxides (2) to the corresponding selenones (3) and oxi-
dation of tellurides (4) and telluroxides (5) to the corresponding tel-
luroxides (6) in high yields with aq. sodium hypochlorite in dimethyl-
formamide at ambient temperature to the corresponding tellurones
in high yields at ambient temperature. First, oxidation of a variety
of diaryl, dibenzyl, aryl alkyl, and dialkyl selenides (1) and selenox-
ides (2) was carried out. The oxidations are complete in 5 min as
monitored by thin layer chromatography using a 1:10 molar ratio of
substrate to sodium hypochlorite (Eqs. 1 and 2). The reactions re-
quired careful quenching with minimum amount of acidified water to
afford high yields of selenones (3). Quenching with an excess of acid-
ified water and washing with excess water lowered the yields of the
(1)
(2)
product. Thus oxidation of various substituted aromatic and aliphatic
selenides (1), as well as selenoxides (2), was achieved successfully to
afford the corresponding selenones (3) in high yields under the opti-
mum reaction conditions. The optimum reaction conditions were found
using diphenyl selenide and diphenyl selenoxide as model substrates.
These results are listed in Table I. Oxidation of diphenyl selenide and
dibenzyl selenide was not complete with aq. sodium hypochlorite in
tetrahydrofuran, acetonitrile and dioxane even after prolonged reac-
tion times and with high molar ratio of substrate to NaOCl. Therefore

Rapid Oxidation of Selenides, Selenoxides, Tellurides and Telluroxides
1371
TABLE I Oxidation of Selenide and Selenoxides with aq. Sodium
Hypochloritea in DMF at Ambient Temperatureb
Selenone (3)
Selenone (3)
Substrate (1,2)
% yield
Substrate
% yield
1a Diphenyl selenide
79
1k p-methylphenyl-n-butyl
selenide
85
1b Dibenzyl selenide
1c Di(p-methylphenyl)
selenide
84
84
2a Diphenyl selenoxide
2b Dibenzyl selenoxide
77
69
1d Di(p-chlorophenyl)
selenide
1e Di(p-bromophenyl)
selenide
1f Di(p-methoxyphenyl)
selenide
1g Di(n-dodecyl) selenide
82
71
83
84
2c Di(p-methylphenyl)
selenoxide
2d Di(p-chlorophenyl)
slenoxide
2e Di(p-bromophenyl)
selenoxide
2f Di(p-methoxyphenyl)
selenoxide
76
84
83
80
1h Di(n-propyl) selenide
1i Di(n-butyl) selenide
1j p-methylphenyl-n-propyl
selenide
81
82
77
2g Di(n-butyl) selenoxide
2h Di(n-dodecyl) selenoxide
80
72
aReactions were carried out using 1:10 molar ratio of substrate to aq. NaOCl.
bReactions were complete in 5 min as monitored by TLC.
dimethylformamide is the solvent of choice for oxidation of selenides
and selenoxides.
The applicability of the reagent was then extended to investigate
the oxidation of different tellurides (4) and telluroxides (5) for which
not many oxidizing agents are known. As a result, we report herein
the rapid oxidation of various aromatic and aliphatic tellurides (4) and
telluroxides (5) with aq. sodium hypochlorite in dimethylformamide
at ambient temperature to the corresponding tellurones (6). The oxi-
dation of tellurides and telluroxides were also complete in 5 min us-
ing a 1:10 molar ratio of substrate to NaOCl at ambient temperature
(Eqs. 3 and 4). The tellurones (6) obtained in this process were pure and
(3)
(4)

1372
J. M. Khurana et al.
gave satisfactory spectroscopic data. Tellurones showed characteristic
fragmentation pattern and is line with sulfur and selenium analogs.
The fragmentation pattern is shown below (Scheme 1). Tellurides and
telluroxides also did not undergo oxidation with aq. sodium hypochlo-
rite in acletonitrile, tetrahydrofuran and dioxane. These results are
summarized in Table II.
SCHEME 1
The oxidation of selenides and tellurides when carried out with a
lower molar ratio of substrate to NaOCl showed the distinct forma-
tion of selenoxides and telluroxides, respectively, but the reactions
were not complete even after prolonged reaction times. Attempts to
carry out selective oxidation of selenides and tellurides to selenox-
ides and telluroxides, respectively, at low temperatures or under phase
transfer conditions were unsuccessful due to competing rapid oxida-
tion of selenoxides and telluroxides. We conclude that aq. sodium
hypochlorite is a simple and convenient oxidising reagent for the
TABLE II Oxidation of Tellurides and Telluroxides
with aq. Sodium Hypochlorite in DMF at Ambient
Temperature
Substrate (4,5)
Tellurone (6) % yield
4a Di(p-methoxyphenyl) telluride
4b Di(p-methylphenyl) telluride
4c Di(p-chlorophenyl) telluride
4d Di(p-bromophenyl) telluride
4e Di(n-butyl) telluride
81
78
78
76
87
68
85
5a Di(p-methylphenyl) telluroxide
5b Di(p-chlorophenyl) telluroxide

Rapid Oxidation of Selenides, Selenoxides, Tellurides and Telluroxides
1373
rapid oxidation of a variety of selenides, selenoxides, tellurides and
telluroxides.
EXPERIMENTAL
The melting points were determined on a Tropical Labequip appara-
tus and are uncorrected. IR were recorded on a Perkin Elmer FT-IR
Spectrum 2000 and NMR spectra were recorded on Hitachi FT-NMR
60 MHz, respectively. Mass spectra were recorded on Jeol JMSD 300
spectrometer using electron impact method (70 eV).
Starting Materials
Dimethylformamide (E. Merck) was used in all the reactions after dis-
tillation. Sodium hypochlorite (S. D. Fine) was used in all the reactions
after estimation11 by the reported procedure. Aromatic selenides were
prepared by slow addition of corresponding diazotized anilinium salt to
potassium selenide solution in an ice bath.12 Dibenzyl and aliphatic se-
lenides were obtained from the reaction of corresponding halides with
selenium and NaBH4.13 The reaction of elemental selenium with aryl
magnesium halide and then with alkyl halides yielded the correspond-
ing unsymmetrical selenides.14 Tellurides were prepared by the treat-
ment of sodium telluride with arenediazonium fluoroborates in DMF.15
Synthesis of selenoxides involved two-step preparations (1) bromine
addition to selenides to give selenide dibromide,9 and (2) alkaline hy-
drolysis of selenide dibromide to give selenoxides.6 Telluroxides were
made by a similar route.16
General Procedure
In a typical reaction, in a 25 mL R.B. flask mounted over a mag-
netic stirrer and fitted with an air condenser, was placed diphenyl se-
lenide (0.1 g, 0.4292 mmol) dissolved in 2 mL of DMF. 2.4 mL of aq.
sodium hypochlorite (1.76 M, 4.292 mmol) was added by stirring. The
reaction mixture was stirred magnetically at room temperature and
progress of the reaction was monitored by tlc using petroleum ether as
eluent. TLC of the reaction mixture showed complete disappearance
of starting material after 5 min. A new product having lower R f was
formed as observed by tlc (eluent: ethyl acetate) and was believed to
be diphenyl selenone by co-tlc. The reaction mixture was quenched af-
ter 15 min by dropwise addition of conc. HCl with stirring till a white
precipitate appeared, this was followed by addition of water (5–7 mL).
The solid was filtered at vacuum pump and dried under vacuum. The

1374
J. M. Khurana et al.
product was characterized by m.p. and spectral data. Reactions of other
aromatic selenides and tellurides were carried out in similar man-
ner. In case of aliphatic, unsymmetrical selenides, selenoxides and
aliphatic tellurides, telluroxides, the reaction mixture was extracted
with diethyl ether (2 15 mL) after acidification. The combined ethe-
real extract was dried over anhyd. MgSO4 and concentrated on a rotary
evaporator. The isolated products were identified by m.p. and spectral
data.
6a: Di(p-methoxyphenyl) tellurone (white solid), m.p. > 300 C (decom-
pose) lit. m.p. > 300 C (decompose);2b IR: 587, 699, 1065, 1177, 1253
(s), 1296, 1490 (s), 1583, 3431 (br) cm 1; NMR (CDCl3): 3.8 (s, 6H),
7.0–7.8 (br, 8H); m/e 375 (15), 342 (15), 267 (20), 148 (100), 104
(30), 77 (30).
6b: Di(p-methylphenyl) tellurone (white solid), m.p. 162–4 C; IR: 485
(s), 589 (s), 683 (s), 800 (s), 1063, 1185, 1392, 1490 (s), 1637, 3422.29
(br) cm 1; NMR: 2.3 (s, 6H), 7.2–7.8 (br, 8H); mass m/e 310 (40),
220 (40), 181 (100), 166 (50), 77 (25).
6c: Di(p-chlorophenyl) tellurone (white solid), m.p. 285–7 C; IR : 488
(s), 591 (s), 685 (s), 728 (s), 813 (s), 1009 (s), 1089 (s), 1383, 1474
(s), 1567, 1656, 3371 (br) cm 1; NMR: 7.0–7.6 (br, 8H); mass: m/e
351 (40), 240 (25), 221 (100), 111 (35), 77 (30).
6e: Di(n-butyl) tellurone (white solid), m.p. 177–80 C; IR: 543 (s), 654
(s), 890, 1090, 1463 (s), 1655, 3400 cm 1; NMR: 1.1 (t, 6H), 3.0 (m,
8H), 3.6 (t, 4H); mass: m/e 242 (10), 185 (10), 57 (80), 41 (100).
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