Ultrasonically activated oxidation of hydroquinones to quinones catalysed by ceric ammonium nitrate doped on metal exchanged K-10 clay

Article abstract of DOI:10.1055/s-2003-36824

We have accomplished the oxidation of hydroquinones to quinones in quantitative yields using catalytic quantity of ceric ammonium nitrate doped on various metal-exchanged K-10 clay, as a mild and efficient reagent, by ultrasonic activation. The exchanged cations examined were Fe³⁺, Cu²⁺, Ce⁴⁺ and K-10 clay itself. The best results were obtained using Fe³⁺-Mont. K-10 clay.

Full text of DOI:10.1055/s-2003-36824

1
98
SHORT PAPER
Ultrasonically Activated Oxidation of Hydroquinones to Quinones Catalysed
by Ceric Ammonium Nitrate Doped on Metal Exchanged K-10 Clay
a
a
b
O
V
xidation of Hydr
a
oquinones
t
s
o
Q
uinon
u
e
s
ndhara Singh,* Varinder Sapehiyia, Goverdhan L. Kad
a
School of Chemistry and Biochemistry, Thapar Institute of Engineering & Technology, Patiala 147004, India
Fax +91(175)393303; E-mail: vasun7@yahoo.co.in
b
Department of Chemistry, Punjab University, Chandigarh 160014, India
Received 4 September 2002; revised 20 November 2002
transition metal ions present in clay. The ion exchange in-
creases the metal ion content and hence enhances its activ-
ity. The nature of the ion also affects its reactivity and the
Abstract: We have accomplished the oxidation of hydroquinones
to quinones in quantitative yields using catalytic quantity of ceric
ammonium nitrate doped on various metal-exchanged K-10 clay, as
a mild and efficient reagent, by ultrasonic activation. The ex- ions also serve as excellent support materials.
3
+
2+
4+
changed cations examined were Fe , Cu , Ce and K-10 clay it-
Our rationale here was to try and take advantage of the
presence of easily reducible cations in clay which were in-
creased by ion exchange for generating the radical cations
and its acidity to promote the reaction using only catalytic
quantity of CAN. The efficient and harsh mixing system
due to ultrasonic activation further accelerates the reac-
tion. When the parent hydroquinone was oxidised with
3
+
self. The best results were obtained using Fe -Mont. K-10 clay.
3
+
Key words: ultrasound, Fe -Mont. K-10 clay, ceric ammonium ni-
trate, hydroquinones, quinones
The advantageous use of ultrasound irradiation technique
for activating various reactions proceeding via SET mech-
anism or radical route is well documented in the litera-
3+
CAN-doped Fe -Mont. K-10 clay under ‘silent’ (without
ultrasound) conditions, the reaction gave after 6 hours the
desired quinone in only 45% yield.
1
ture. One of the most notable oxidants among lanthanide
reagents is cerium ammonium nitrate (CAN), a one-elec-
tron oxidant whose chemistry is dominated by radical and
radical cation chemistry. It has been utilised extensively
Substituted quinones are not only present as common
units in natural products but also used as very useful inter-
mediates in organic synthesis. A wide variety of reagents
oxidise hydroquinones to quinones. Among the common
methods, the stoichiometric oxidation methods use chro-
2
for a variety of oxidative transformations. However, the
earlier work on Ce(IV) promoted oxidations was carried
out in strongly acidic media using stoichiometric to large
6
7
8
mium trioxide, sodium hypochlorite, iron(III) chloride,
3
excess of CAN. In continuation of our work on develop-
9
and silver oxide as oxidants. Catalytic oxidations using
ing new methodologies in organic synthesis using non-
conventional energy sources we herein report an effective
conversion of hydroquinones to quinones in quantitative
yields using ultrasonic activation in the presence of cata-
lytic quantity of CAN doped on various cation exchanged
K-10 montmorillonite clay as a mild catalyst (Scheme 1).
1
0
nitrogen oxides/O , alumina supported copper sulfate/
2
O2,11 and VO(acac) /O2 have been reported recently.
12
2
These methods require either stoichiometric amounts of
catalyst or tedious reaction conditions.
3
+
2+
4+
The cation (Fe , Cu , Ce ) exchanged K-10 clay were
prepared according to the method reported in the litera-
1
3
3+
ture. The best results were obtained with Fe -Mont. K-
0 clay and is given in Table 1 and was used in the oxida-
1
3
+
tion of all other derivatives (see Table 2). The Fe -Mont.
K-10 clay can be recycled after the reaction by washing
with water, and drying at 120 °C for 5 hours.
Simple Mont. K-10 clay did not work efficiently. Metal
3+
Scheme 1
ion content of Fe -Mont. K-10 clay was determined by an
electro-disperse X-ray microscope (EDX) connected to a
Environmental problems has led to an increased interest in
the study of heterogeneous reactions that involve solid re-
agents supported on high surface area inorganic materi-
Table 1 Variation in Yield of Quinone Using CAN Doped on Dif-
ferent Metal Ion Exchanged Clays
4
als. Clays and its modified forms are known to have
Lewis and Brönsted acid sites along with radical cation Entry
Catalyst
Yield (%)
5
centers in them. The radical cations are formed by the
2
+
1
Cu -Mont. K-10 Clay
55
70
98
4
+
2
Ce -Mont. K-10 Clay
Synthesis 2003, No. 2, Print: 31 01 03.
Art Id.1437-210X,E;2003,0,02,0198,0200,ftx,en;P04802SS.pdf.
3+
3
Fe -Mont. K-10 Clay
©
Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

SHORT PAPER
Ultrasonically Activated Oxidation of Hydroquinones to Quinones
199
3+
Table 2 Oxidation of Hydroquinone and its Derivatives to the Corresponding Quinones Catalysed by CAN-Doped Fe -Mont. K-10 Clay
Entry
Reactant
Producta
Yield
%)
Time
(min)
CAN (mmol/ Mp (°C)
mmol of Sub- Found
strate)
Reported
(
1
98
93
30
30
0.5
0.1
112
66
115
2
3
68–69
90
90
0.1
57–59
59
4
5
90
92
90
60
0.1
0.1
104
54
105–106.5
55–56
6
7
97
85
60
0.1
0.2
47
–
120
142
144–146
a
The products were purified by crystallisation from Et O, except for entry 4, which is purified from CHCl –toluene. All Products are known
2
3
1
and were characterised by spectral ( H NMR and IR) analyses.
Jeol scanning electron microscope. The Fe content in the croscope. CH
exchanged clay was found to be 13.83 wt% and in the
original clay 10.38 wt%.
Cl
was dried by distilling over P O . K-10 Montmo-
2 5
2
2
rillonite clay was purchased from Aldrich. Metal salts used were
purchased from S. D Fine Chemicals, India.
Preparation of Metal-Exchanged Clays
The metal exchanged clays were prepared by slowly adding the clay
1
H NMR spectra were recorded in CDCl or CCl on a 300 MHz
3
4
Bruker instrument using TMS as internal standard. IR spectra were
recorded on a Perkin Elmer 337 spectrometer. Branson Ultrasonic
cleaning bath model 3150 DTH was used in all the experiments. The
metal content of the clay was determined using electron-disperse X-
ray microscope (EDX) connected to a Jeol, scanning electron mi-
(1.0 g) to dilute solutions of CuCl
mL), and Ce(SO (0.25 M in 1 M H
and stirring for a period of 24 h. After exchange, suspensions were
filtered and washed with deionised H O to free from anions. The re-
sultant solids were dried on a thin bed at 120 °C for 12 h and ground
2
(1 M, 12.5 mL), FeCl
3
(1 M, 12.5
)
SO ,16.7 mL), respectively,
4
2
2
4
2
Synthesis 2003, No. 2, 198–200 ISSN 0039-7881 © Thieme Stuttgart · New York

2
00
V. Singh et al.
SHORT PAPER
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3
+
4+
2+
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(
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(
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1
2
2
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1
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2
1
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(
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edged.
2
3
(
(
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Synthesis 2003, No. 2, 198–200 ISSN 0039-7881 © Thieme Stuttgart · New York