Radical low-temperature oxidation of dibenzyl sulfide with the triphenylbismuth-tert-butyl hydroperoxide system

Article abstract of DOI:10.1007/s11172-008-0152-2

The reaction of Ph₃Bi with Bu^tOOH in a mole ratio of 1: 3 in hydrocarbon solvents affords the η²-peroxo complex of triphenylbismuth Ph₃Bi(η²O₂) which oxidizes the C-H bonds of the methylene group of dibenzyl sulfide. The reaction proceeds via the radical mechanism with the formation of intermediate unstable sulfur-containing hydroperoxide. Its decomposition is accompanied by the C-S bond cleavage, resulting in benzaldehyde.

Full text of DOI:10.1007/s11172-008-0152-2

1
206
Russian Chemical Bulletin, International Edition, Vol. 57, No. 6, pp. 1206—1208, June, 2008
Radical lowꢀtemperature oxidation of dibenzyl sulfide
with the triphenylbismuth—tertꢀbutyl hydroperoxide system
V. A. Dodonov, E. A. Zaburdaeva, E. N. Chelebaeva, and V. A. Kuropatovb
a
a
a
aN. I. Lobachevsky Nizhny Novgorod State University,
2
3 prosp. Gagarina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831) 462 3085. Eꢀmail: zaea4@rambler.ru
b
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
4
9 ul. Tropinina, 603600 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831) 466 1497. Eꢀmail: viach@iomc.ras.ru
t
The reaction of Ph Bi with Bu OOH in a mole ratio of 1 : 3 in hydrocarbon solvents affords the
3
2
2
η ꢀperoxo complex of triphenylbismuth Ph Bi(η O ) which oxidizes the C—H bonds of the methylꢀ
3
2
ene group of dibenzyl sulfide. The reaction proceeds via the radical mechanism with the formation of
intermediate unstable sulfurꢀcontaining hydroperoxide. Its decomposition is accompanied by the
C—S bond cleavage, resulting in benzaldehyde.
2
Key words: dibenzyl sulfide, η ꢀperoxo complexes, triphenylbismuth, tertꢀbutyl hydroperoxide,
oxidation, radical mechanism, benzaldehyde, organobismuth compounds.
Oxygen activation on metallic centers of transition and
Scheme 2
nontransition metals in lowꢀtemperature (20 °C) oxidaꢀ
tion is one of the most important problems of organic
catalysts. Metalꢀcontaining compounds of the
t
t
1,2
ozonide type (Bu O) MOOOBu (n = 3, M = Al;
n–1
2
,3
2
Peroxo complex 1 and the ozonides mentioned above
are efficient lowꢀtemperature oxidants of C—H bonds4
featuring by the reaction conditions and, especially, by
the final products. Dioxygen coordinated on the metal
atom acts as a direct oxidant.
The purpose of the present work is to obtain comparꢀ
ative data on the reactivity of the peroxide derivatives of
bismuth and aluminum in the lowꢀtemperature (20 °C)
oxidation of the C—H bonds in the benzyl group usꢀ
ing dibenzyl sulfide and ethylbenzene as examples.
n = 4, M = Ti ) and the bismuth η ꢀperoxo complex
2
4,5
Ph Bi(η ꢀO ) (1) serve as the sources of electronꢀexꢀ
3
2
cited dioxygen. Ozonides are formed upon the reaction of
the corresponding metal tertꢀbutoxides with tertꢀbutyl
hydroperoxide 2 in a mole ratio of 1 : 2, whereas
2
η ꢀperoxo complex 1 is formed due to the thermal deꢀ
composition of di(tertꢀbutylperoxy)triphenylbismuth 3
at room temperature. Compound 3 is a product of
the reaction of triphenylbismuth (4) with hydroperoxide
4
,5
2
in a mole ratio of 1 : 3 (Scheme 1).
The choice of Bn S is due to the fact that, on the one hand,
2
no oxidation products of the benzylic C—H bonds
were observed upon its interaction with ozonides
Scheme 1
t
t
6
(
Bu O) MOOOBu (n = 3, M = Al; n = 4, M = Ti). On
n–1
7
the other hand, it is known that the oxidation of this
sulfide with oxygen, under the conditions of radio freꢀ
quency discharge or irradiation with a Xe—Hg lamp senꢀ
sibilized by zinc tetraphenylporphine, results in its deꢀ
struction at the C—S bond to benzaldehyde.
Experimental
Solvents (analytical and reagent grade) were purified as follows:
benzene and ethylbenzene were distilled over P O (stored above
η2ꢀPeroxo complex 1 selectively oxidizes the methylꢀ
2
5
ene groups of alkanes to form carbonyl groups via the
metallic sodium) and chlorobenzene was distilled and stored over
Na SO . Dibenzyl sulfide (pure grade) was recrystallized from
radical mechanism4 (Scheme 2).
,5
2
4
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1183—1185, June, 2008.
066ꢀ5285/08/5706ꢀ01206 © 2008 Springer Science+Business Media, Inc.
1

Radical oxidation of dibenzyl sulfide
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 6, June, 2008
1207
ethanol. Triphenylbismuth (4) was synthesized according to a
companied by selfꢀheating of the reaction mixture and
8
known procedure. The synthesis and properties of aluminum triꢀ
completed within 1 h.
2
tertꢀbutoxide were described previously. tertꢀButyl hydroperoxide
Taking into account the earlier data1,4 on the oxidaꢀ
9
t
(
2) was synthesized by a known procedure, providing Bu OOH
tion of the C—H bonds of hydrocarbons by the 4—2 and
with an active oxygen content of 99.5—99.8%.
5
—2 systems via the radical mechanism, we assume that
tertꢀButyl alcohol was identified on an LKhMꢀ80 chromatoꢀ
graph at 80 °C on a 3000 mm column packed with dinonyl phthaꢀ
late (30%) on Chromaton NꢀAWꢀDMCS. Benzaldehyde and aceꢀ
tophenone were analyzed at 110—120 °C on a 2400 mm column
with 10% Reoplexꢀ400 on Inerton AWꢀDMCS. Biphenyl and
benzyl benzoate were identified at 240 °C on a 2000 mm column
packed with 5% SEꢀ30 on Inerton AW. Helium served as the
carrier gas.
the primary act of Bn S oxidation is the abstraction of the
2
hydrogen atom from the methylene group of the substrate
(Scheme 3).
Scheme 3
The determination of Bn S and Ph Bi (4) was carried out on
2
3
a Knower liquid chromatograph equipped with a UV spectrophoꢀ
tometer using a 150 mm column packed with Serapon SGX C18.
The calculation was performed by the internal normalization method.
Carbonyl compounds were transformed into their 2,4ꢀdinitroꢀ
phenylhydrazones, which were identified by TLC using Silpearl on
the aluminum foil (Silufol UVꢀ254) as the sorbent and benzene as
the eluent.
The ESR spectrum was recorded on a Bruker ER200DꢀSRC
spectrometer equipped with an ER 4105 DR double resonator and
an ER 4111 VT thermocontrolling unit. Diphenylpicrylhydrazyl was
used as the standard in the determination of the g factor.
The mass spectrum was obtained on a Hewlett—Packard mass
spectrometer combined with an HPꢀ5890 gas chromatograph, an
HPꢀ5972 massꢀselective detector, and a working station equipped
with a software and the NIST98.L and WILEY 138.L massꢀspectral
databases Ultraꢀ2 (25 000 mm column of the HPꢀ5MS type, injecꢀ
tor temperature 280 °C).
The ESR method using 2ꢀmethylꢀ2ꢀnitrosopropane
(MNP) as a spin trap was used to identify assumed radiꢀ
cal 6. The analysis was carried out in chlorobenzene in
the temperature interval from +25 to –60 °C. The signals
(
Fig. 1) of the spinꢀadduct of MNP with the phenyl raꢀ
dical
(aN = 1.23 mT, a2HM = 0.09 mT, a3HO,P
=
2
0
.21 mT, g = 2.0060,10 (aN = 1.54 mT) ) formed by the
t
Reaction of Bn S with the Ph Bi (4)—Bu OOH (2) system.
2
3
reaction of compound 3 and di(tertꢀbutyl)nitroxyl radiꢀ
Hydroperoxide 2 (6.4 mmol) and Bn S (2.1 mmol) were added to
2
a solution of compound 4 (2.1 mmol) in benzene (14 mL). The
reaction mixture was kept for 1 day at ~20 °C, after which the solvent
and volatile reaction products were condensed into a trap cooled
cal , which is the product of MNP selfꢀreduction
under irradiation (аN = 1.54 mT),2 were identified
at –13 °C. The intermediate formation of the phenyl radiꢀ
cal is also indicated by the presence of biphenyl (5—11%;
reaction in benzene) or chlorobiphenyl (qualitativeꢀ
ly identified by GLC, reaction in chlorobenzene) in
t
with liquid nitrogen. The volatile fraction contained Bu OH
5.2 mmol) and PhCHO (0.5 mmol). The solid residue in the flask
(
was washed with THF, and the solution was decanted. The GLC
method showed PhCНO (0.5 mmol), Ph (0.1 mmol), and benzyl
2
benzoate (0.1 mmol). Unreacted Bn S (0.8 mmol) and compound 4
2
(0.6 mmol) were identified by liquid chromatography.
Results and Discussion
The oxidation of Bn S was carried out by the systems
2
4
—2 and aluminum triꢀtertꢀbutoxide (5)—2 in ethylbenꢀ
zene and "unoxidizable" solvents (benzene and chloꢀ
robenzene) at room temperature and the ratio of compoꢀ
nents chosen earlier by the study of the oxidation of
4
,5
1,2,4
the C—H bonds of hydrocarbons: 1 : 3 and 1 : 2,
respectively.
0
.4 mT
The reaction of Bn S with the 4—2 system in benzene
2
affords benzaldehyde and benzyl benzoate in 51 and 5%
yields, respectively. A similar reaction in ethylbenzene
afforded benzaldehyde (31%) and acetophenone (oxidaꢀ
tion product of the solvent, 14%). The reaction of Bn2S
with the 5—2 system in benzene and ethylbenzene gave
sulfone Bn SO in 99% yield, and the reaction was acꢀ
t
Fig. 1. ESR spectrum recorded in the Bn S—Ph Bi—Bu OOH
2
3
(1 : 1 : 3) system in the presence of 2ꢀmethylꢀ2ꢀnitrosopropane in
chlorobenzene at –13 °C (the sample was degassed).
2
2

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Russ.Chem.Bull., Int.Ed., Vol. 57, No. 6, June, 2008
Dodonov et al.
the reaction mixture. No radical 6 was found. Perhaps, the
radical pair that formed interacts in the solvent cage with a
higher rate than radical 6 interacts with the spin trap.
Sulfurꢀcontaining hydroperoxide 7 was not isolated in
the individual state. It is most likely that it readily decomꢀ
poses with the C—S bond cleavage to benzaldehyde and
benzylmercaptane. The latter, as well known,11 is easily
oxidized, under mild conditions, at the sulfur atom by
References
1
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3
hydrogen peroxide or a CuCl —air system to unstable
2
(Engl. Transl.)].
sulfenic acid and dibenzyl disulfide, which was qualitaꢀ
tively found by mass spectrometry combined with chroꢀ
matography. We also identified benzyl thiolbenzoate
4
. V. A. Dodonov, E. A. Zaburdaeva, N. V. Dolganova, L. P.
Stepovik, T. I. Zinov´eva, Zh. Obshch. Khim., 1997, 67, 988
[Russ. J. Gen. Chem., 1997, 67 (Engl. Transl.)].
PhC(O)SCH Ph, which is the product of radical ketonꢀ
ization of the methylene group of the benzyl fragment of
the starting sulfide (сf. Scheme 2).
5. T. I. Zinov´eva, N. V. Dolganova, V. A. Dodonov, I. G. Prezhꢀ
bog, Izv. Akad. Nauk, Ser. Khim., 1998, 681 [Russ. Chem. Bull.,
2
1
998, 47, 659 (Engl. Transl.)].
6
. V. A. Dodonov, E. A. Zaburdaeva, L. P. Stepovik, Izv. Akad.
Nauk, Ser. Khim., 2004, 1663 [Russ. Chem. Bull., Int. Ed.,
In addition, the reaction products always contain
highꢀboiling compounds, presumably the corresponding
benzyl thiosulfinate and benzyl thiosulfonate, which are
2
004, 53, 1729].
7
8
. E. J. Corey, C. Ouannes, Tetrahedron Lett., 1976, 4263.
. K. A. Kocheshkov, A. P. Skoldinov, N. N. Zemlyanskii, Metody
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ganoelement Chemistry. Stibium, Bismuth], Nauka, Moscow,
1976, p. 402 (in Russian).
7
formed due to the transformations of sulfenic acid.
Differences in chemiselectivity that appear in the oxiꢀ
dation of dibenzyl disulfide by the 4—2 and 5—2 systems
are caused by the method of generation of electronꢀexcitꢀ
ed dioxygen on the metal atom. Dioxygen coordinated on
the aluminum atom oxidizes the sulfur atom of the sulꢀ
fide with the intermediate formation of thiadioxirane,6
9. V. Karnozhitskii, Organicheskie perekisi [Organic Peroxides],
Izd. Inostr. Lit., Moscow, 1961, 156 (in Russian).
10. V. E. Zubarev, Metod spinovykh lovushek [Method of Spin Traps],
Izd. Mosk. Gos. Univ., Moscow, 1984, 188 (in Russian).
which is further transformed into sulfone. We assume
1
1. S. Hauptmann, I. Eraefe, H. Remane, Organische Chemie, VEB
Deutscher Verlag für Grundstoffindustrie, Leipzig, 1976.
2. S. Wallenhauer, D. Leopold, K. Seppelt, Inorg. Chem., 1993,
2, 3948.
2
that dioxygen of η ꢀperoxo complex 1 is more strongly
retained in the coordination sphere of bismuth in the form
of the ligand.12
1
3
The authors are grateful to V. A. Utsal´ for help in
mass spectrometric studies.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 08ꢀ03ꢀ
9
7050ꢀr_povolzh´e).
Received July 27, 2007;
in revised form March 20, 2008