Khurana and Nand
907
Table 1. Oxidation of sulfides, selenides, and tellurides with aq. sodium hypochlorite to dioxides, supported on silica gel, under micro-
wave exposure.
Entry
1
2
3
4
Substrate
Diphenyl sulfide
Dibenzyl sulfide
Di(n-dodecyl) sulfide
Product
Time (min)
Yield (%)
93
80
82
87
Diphenyl sulfone8,10b,10c,10e
10
10
9
Dibenzyl sulfone8,10b,10e
Di(n-dodecyl)sulfone8,10b,10e
Benzyl phenyl sulfide
Benzyl phenyl sulfone8,10b,10e
9
5
6
7
8
Phenyl n-propyl sulfide
n-Dodecyl phenyl sulfide
p-Chlorophenyl phenyl sulfide
p-Bromophenyl phenyl sulfide
m-Chlorophenyl phenyl sulfide
Diphenyl selenide
Phenyl n-propyl sulfone8,10b,10e
n-Dodecyl phenyl sulfone8,10b,10e
p-Chlorophenyl phenyl sulfone8,10b,10e
p-Bromophenyl phenyl sulfone8,10b,10e
m-Chlorophenyl phenyl sulfone8,10b,10e
Diphenyl selenone7g,10b,10d,10e
10
10
10
10
10
5
6
6
6
7
82
83
84
81
80
91
88
86
86
89
80
79
76
77
9
10
11
12
13
14
15
16
17
18
Dibenzyl selenide
Dibenzyl selenone7g,10b,10d,10e
Di(p-bromophenyl) selenide
Di(p-methylphenyl) selenide
Di(p-methoxyphenyl) selenide
Di(p-methylphenyl) telluride
Di(p-methoxyphenyl) telluride
Di(p-bromophenyl) telluride
Methyl phenyl telluride
Di(p-bromophenyl) selenone7g,10b,10d,10e
Di(p-methylphenyl) selenone7g,10b,10d,10e
Di(p-methoxyphenyl) selenone7g,10b,10d,10e
Di(p-methylphenyl) tellurone7g,10b,10d,10e
Di(p-methoxyphenyl) tellurone7g,10b,10d,10e
Di(p-bromophenyl) tellurone7g,10b,10d,10e
Methyl phenyl tellurone7g,10b,10d,10e
5
7
6
6
Note: Reactions were carried out using 3 mL of aq. NaOCl (0.65 mol/L) per mmol of substrate.
for 10 min. The progress of the reaction was monitored by
TLC using petroleum ether as eluent, which showed com-
plete disappearance of staring material after 10 min and for-
mation of a new product having lower Rf (eluent: ethyl
acetate), which was believed to be diphenyl sulphone by
co-TLC. The reaction mixture was cooled to room tempera-
ture and the product was extracted with dichloromethane
(2 ꢀ 5 mL). The combined dichloromethane extract was
dried over anhyd. Na2SO4, filtered, and concentrated to af-
ford 0.22 g (93%) of pure diphenyl sulfone as white solid
identified by its mp 126 8C (lit.10b mp 128 8C), superimpos-
white solid obtained was identified to be diphenyl sulfoxide
(0.18 g, 82%) by mp 70 8C (lit.10e mp 71 8C), superimpos-
able IR, and 1H NMR spectra. Oxidation of selenides and tel-
lurides was carried out in a similar fashion using 0.36 mol/L
aq. NaOCl solution.
Results and discussion
We report herein an efficient, mild, and rapid method for
the selective oxidation of chalcogenides (sulfides, selenides,
and tellurides) to the corresponding monoxides (sulfoxides,
selenoxides, and telluroxides) or the corresponding dioxides
(sulfone, selenone, and tellurone) with inexpensive aq. so-
dium hypochlorite under microwave irradiation. Diphenyl
sulfide was chosen as a model substrate for optimization.
Oxidation of diphenyl sulfide was attempted with aq. NaOCl
(0.65 mol/L) on different inorganic solid supports, e.g., neu-
tral, acidic, and basic alumina; silica gel and montmorillonite
K10 by adsorbing the substrate; and aq. sodium hypochlorite
on solid support followed by exposing the reaction mixture
to microwave irradiation (100 W). Oxidations on silica gel
gave diphenyl sulfone in high yields (93%) in shorter time
unlike other supports, which required longer reaction times
and (or) gave reaction mixtures. Diphenyl selenide and
di(p-methylphenyl) telluride also underwent oxidation to di-
phenyl selenone and di(p-methylphenyl) tellurone, respec-
tively, under the same reaction conditions but required even
shorter exposure to microwaves. Oxidation in the absence of
solid support was incomplete, and a mixture of monoxide
and dioxide was obtained. Subsequently, oxidation of vari-
ous substituted aromatic and aliphatic sulfides, selenides,
and tellurides was carried out with aq. sodium hypochlorite
on silica gel solid support after exposure to microwaves to
give the corresponding sulfones, selenones, and tellurones
in high yields (eq. [1], Table 1).
1
able IR, and H NMR spectra.
General procedure for the oxidation of chalcogenides to
monoxides
In a typical experiment, diphenyl sulfide (0.2 g, 1.074 mmol)
is dissolved in dichloromethane (3 mL) and adsorbed over
neutral alumina (1.2 g). Aqueous sodium hypochlorite (1
mL, 0.65 mol/L) was added and mixed thoroughly in a
beaker. The reaction mixture was inserted in an alumina
bath (20 g of neutral alumina) and placed in a microwave
oven (Model No.OM-9925-E, 800 W, 2450 MHz) and irra-
diated at 100 W for 3 min. After cooling for 1 min, another
1 mL of aq. sodium hypochlorite solution (0.65 mol/L) was
added, and the mixture was stirred with a glass rod and irra-
diated again for 3 min. The progress of the reaction was
monitored by TLC using petroleum ether as eluent. TLC
showed complete disappearance of the starting material after
6 min and formation of a product having lower Rf (eluent:
ethyl acetate), which was believed to be diphenyl sulfoxide
by co-TLC. The reaction mixture was cooled to room tem-
perature and the product was extracted with dichlorome-
thane (2 ꢀ 5 mL). The combined dichloromethane extract
was dried over anhyd. Na2SO4, filtered, and concentrated.
The product was purified by column chromatography on
silica gel using petroleum ether/ethyl acetate as eluent. The
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