Oxidation of 2-aminophenol with molecular oxygen and hydrogen peroxide catalyzed by water soluble metalloporphyrins

Article abstract of DOI:10.1016/j.molcata.2012.06.002

5,10,15,20-Tetrakis-(p-sulfonatophenyl)porphinatocobalt(II) and 5,10,15,20-tetrakis-(p-sulfonatophenyl)porphinatomanganese(III) chloride have been used as catalysts for the oxidative coupling of 2-aminophenol to 2-aminophenoxazine-3-one with molecular oxygen and hydrogen peroxide. The effects of pH and concentration of catalysts, hydrogen peroxide and oxygen on the oxidation reaction and yield of 2-aminophenoxazine-3-one have been studied. The oxidation of 2-aminophenol with molecular oxygen catalyzed by cobalt(II) tetra(4-sulfophenyl)porphyrin involves a hydrogen atom abstraction from 2-aminophenol by cobalt(II) superoxo species. UV-vis analysis indicated that oxomanganese(IV) is the active species in the oxidation of 2-aminophenol with hydrogen peroxide and manganese(III)tetra(4-sulfophenyl)porphyrin.

Full text of DOI:10.1016/j.molcata.2012.06.002

Journal of Molecular Catalysis A: Chemical 363–364 (2012) 148–152
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Oxidation of 2-aminophenol with molecular oxygen and hydrogen peroxide
catalyzed by water soluble metalloporphyrins
Sahar H. El-Khalafy∗, M. Hassanein
Chemistry Department, Faculty of Science, Tanta University, Tanta 31527, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
5,10,15,20-Tetrakis-(p-sulfonatophenyl)porphinatocobalt(II) and 5,10,15,20-tetrakis-(p-sulfonato-
phenyl)porphinatomanganese(III) chloride have been used as catalysts for the oxidative coupling
of 2-aminophenol to 2-aminophenoxazine-3-one with molecular oxygen and hydrogen peroxide.
The effects of pH and concentration of catalysts, hydrogen peroxide and oxygen on the oxidation
reaction and yield of 2-aminophenoxazine-3-one have been studied. The oxidation of 2-aminophenol
with molecular oxygen catalyzed by cobalt(II) tetra(4-sulfophenyl)porphyrin involves a hydrogen
atom abstraction from 2-aminophenol by cobalt(II) superoxo species. UV–vis analysis indicated that
oxomanganese(IV) is the active species in the oxidation of 2-aminophenol with hydrogen peroxide and
manganese(III)tetra(4-sulfophenyl)porphyrin.
Received 18 April 2012
Received in revised form 30 May 2012
Accepted 5 June 2012
Available online 15 June 2012
Keywords:
Catalytic oxidation
2-Aminophenol
Metalloporphyrins
2-Aminophenoxazine-3-one
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
silica [15–17] have been reported also as catalysts for the oxidative
coupling of OAP.
The oxidation of organic substrates with molecular oxygen
and hydrogen peroxide under mild conditions is of great inter-
est for industrial and synthetic processes both from an economical
and environmental point of view [1–3]. The oxidative coupling
of 2-aminophenol (OAP) to 2-amino-3H-phenoxazine-3-one (APX)
through catalytic activation of dioxygen by transition metal com-
plexes (Scheme 1) has been considered as one of the important
reactions [4–17]. The enzyme phenoxazinone synthase is involved
in the last stages of the biosynthesis of actinomycin D, a natu-
rally occurring antibiotic, which is used clinically for the treatment
of Wilm’s tumor, gestational choriocarcinoma and other tumors
[18–20].
Synthetic metalloporphyrins have been widely used as catalysts
for a great variety of oxidation reactions [21–42].
We now report the oxidation of 2-aminophenol with molecular
oxygen and hydrogen peroxide catalyzed by 5,10,15,20-
tetrakis-(p-sulfo-natophenyl)porphinatocobalt(II) CoTPPS and
5,10,15,20-tetrakis-(p-sulfonatophenyl)porphinatomanganese(III)
chloride MnTPPS. To the best of our knowledge, this is the first
report on the oxidation of 2-aminophenol using metalloporphyrins
as catalysts.
2. Experimental
Transition metals and complexes such as copper salts [4],
forroxime(II) [5], dioximatomanganese(II) [6] and manganese(II)
isoindoline based complexes have been reported as phenoxazi-
none synthase models [7] for the oxidative coupling of OAP. Cobalt
salts [8], cobalt(II) salen [9,10] bis-(dimethyl-glyoximato) cobalt(II)
complexes [11] and cobalt(II) phthalocyanine derivatives [12,13]
have been used as catalysts for the oxidative coupling of OAP.
TEMPO (2,2,6,6-tetramethyl-1-pipridinloxyl) initiated oxidation of
OAP has been reported by Speier and co-workers [14]. Transi-
tion metal complexes immobilized on polymers and mesoporous
2.1. Materials and reagents
2-Aminophenol (Aldrich) and aqueous hydrogen peroxide
solution (30.0% by weight; Merck) were used as received.
5,10,15,20-Tetrakis-(p-sulfonatophenyl)porphyrin (TPPS) was pre-
pared based on a literature procedure [43] and its metallation
with cobalt chloride and manganese chloride was carried out as
described previously [44]. Doubled distilled deionized water was
used in all reactions.
2.2. Measurements
Spectrophotometric measurements were carried out on Shi-
madzu 3101 UV-vis Spectrometer.
∗
Corresponding author. Tel.: +20 1007276665; fax: +20 403344352.
E-mail address: saharelkhalfy@hotmail.com (S.H. El-Khalafy).
1381-1169/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2012.06.002

S.H. El-Khalafy, M. Hassanein / Journal of Molecular Catalysis A: Chemical 363–364 (2012) 148–152
149
N
NH2
NH2
OH
Catalyst
3H2O
3/2 O2
2
+
+
O
O
APX
Scheme 1.
2.3. Oxidation reactions
0.12
0.10
0.08
0.06
0.04
0.02
2.3.1. General procedure for the oxidation of OAP with O2
catalyzed by Co(II)TPPS
Oxidation reactions were carried out by stirring 100 ml of an
aqueous reaction mixture containing 5 vol% methanol in a 250-ml
round bottomed flask attached to a gas buret. All reactions were
carried out at 40 ◦C and at constant oxygen pressure. Low partial
pressure of oxygen was obtained by using of oxygen/nitrogen mix-
ture at 1 atm total pressure. The pH of the medium was adjusted
to 9.0 using borate buffer. The reaction mixture was extracted with
diethyl ether (50 ml) and the extract was tested by TLC (Merck)
using CHCl3–MeOH mixture (20:1 by volume) as eluent, which
showed the presence of APX along with unreacted OAP. The organic
layer was then washed with dilute aqueous sodium hydroxide solu-
tion (10%; 50 ml), dried with anhydrous Na2SO4 and the ether was
evaporated to give the product.
7.0
7.5
8.0
8.5
9.0
9.5
10.0
pH
2.3.2. Oxidation of 2-aminophenol with H2O2 catalyzed by
Mn(III)TPPS
Fig. 1. Effect of pH on the rate of auto-oxidation of OAP. All reactions were carried
out at 40 ◦C and dioxygen pressure of 730 mmHg with magnetic stirring of 2 mmol
of OAP dissolved in 5.0 ml of methanol and 1.5 × 10−5 of Co(TPPS). The volume of
reaction mixture was maintained at 100 ml. The pH 7.0 was adjusted using a mixture
of Na2HPO4 and HCl. The pH was adjusted to 8.0 and 9.0 by using sodium borate and
HCl mixture and the pH was adjusted to 10.0 using NaHCO3 and NaOH mixture.
A mixture of OAP (0.296 g; 2.7 mmol), Mn(III)TPPS (5.40 mg;
4.9 × 10−3 mmol) and H2O2 (1 ml; 10 mmol) in water (30 ml) was
stirred at room temperature for 4.5 h. The pH of the mixture was
adjusted to 8.0 using borate buffer. The reaction was worked up as
reported in Section 2.3.1.
increased with increasing the concentration of 2-aminophenol to
1.5 × 10−3 M and then leveled off.
3. Results and discussion
A double reciprocal Lineweaver plot (Fig. 4) showed that the
rate fit Michealis–Menten kinetic model [45,46] for saturation of
catalyst site with increasing concentration of 2-aminophenol.
The effect of partial pressure of molecular oxygen on the
auto-oxidation of OAP was investigated by using oxygen/nitrogen
mixture to obtain reduced partial pressure of 1 atm total pressure
3.1. Oxidation of 2-aminophenol with dioxygen catalyzed by
Co(II)TPPS
The catalytic activity of water soluble Co(II)TPPS was inves-
tigated in the oxidation of OAP with dioxygen. The rate of
2-aminophenol consumption was determined by measuring the
amount of dioxygen using a gas buret. After a short induction
period, the volume of dioxygen consumed was linear with time,
indicating a zero-order dependence on the concentration of the
substrate. Oxidation of OAP under standard conditions of pH = 9.0
and slightly less than 1 atm of dioxygen gave within 2 h APX (65%)
and unreacted OAP. The zero-order rate constant kobs calculated
from the plots of the oxygen consumption with time shows that
the oxidation reaction of OAP catalyzed by Co(II)TPPS is three times
faster than oxidation of OAP in the absence of catalyst.
0.20
0.16
0.12
0.08
Data in Fig. 1 illustrate the effect of pH in the range 7.0–11.0 on
the rate constant kobs for the auto-oxidation of OAP. The decreases
in reaction rate at pH values higher than 9 indicates that the o-
aminophenoxide anion is not the active species [13].
The data in Fig. 2 show the effect of Co(II)TPPS concentration on
the rate constant kobs of the oxidation reaction. The rate constant
kobs increased linearly with increasing catalyst concentration from
0.75 × 10−5 M to 3.35 × 10−5 M.
0.04
The temperature dependence of the rate constant kobs from 30
to 60 ◦C gave an Arrhenius activation energy of 10.84 kJ/mol.
The dependence of the rate constant kobs of oxidation reac-
tion on the concentration of OAP was investigated in the
range (0.5–2.5) × 10−3 M (Fig. 3). The reaction rate constants kobs
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040
-1
104 [Co(TPPS)] mol L
Fig. 2. The dependence of the rate constant kobs on Co(TPPS) concentration. For
reaction conditions, see Fig. 1.

150
S.H. El-Khalafy, M. Hassanein / Journal of Molecular Catalysis A: Chemical 363–364 (2012) 148–152
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0.0
0.5
1.0
1.5
2.0
2.5
0
100
200
300
400
500
600
700
103[OAP] mol-1
PO2 (mmHg)
Fig. 3. The dependence of rate constant on 2-aminophenol concentration. For reac-
Fig. 5. The dependence of rate constant in the oxidation of 2-aminophenol on dioxy-
tion conditions, see Fig. 1.
gen pressure. For reaction conditions, see Fig. 1.
35
30
25
20
15
10
5
14
12
10
8
6
4
2
0
0
1
2
3
4
5
6
7
0.4
0.8
1.2
1.6
2.0
103 1/[OAP] mol-1
L
1/PO2(mmHg)
Fig. 6. Lineweaver–Burk plot of the data in Fig. 5.
Fig. 4. Lineweaver–Burk plot of the data in Fig. 3.
Table 1
Effect of pH on the oxidation of 2-aminophenol with H2O2 catalyzed by Mn(TPPS).a
on the reaction mixture. Similarly the observed rate constants kobs
depend on the partial pressure of molecular oxygen for saturation
of catalyst site as shown in Figs. 5 and 6.
pH
APX %
7
8
9
40
62
55
21
3.2. Oxidation of OAP with H2O2 catalyzed by Mn(III)TPPS
10
a
A mixture of OAP (0.296 g; 2.7 mmol), Mn(III)TPPS (5.40 mg; 4.9 × 0−3 mmol) and
H2O2 (1 ml; 10 mmol) in water (30 ml) was stirred at room temperature for 4.5 h at
the indicted pH. The pH of the reactions was adjusted from 7 to 10 as reported in
footnote of Fig. 1.
Oxidation of 2-aminophenol with H2O2 in aqueous medium at
room temperature (pH = 8.0) catalyzed by Mn(III)TPPS gave APX in
62% yield along with unreacted OAP after 4.5 h. The conversion was
very low (10%) when no catalyst was used under similar reaction
conditions.
The effect of reaction parameters such as pH, concentration of
catalyst, OAP and H2O2 on the yield of APX has been investigated.
Table 1 shows that the yield of APX was sensitive to pH of the
reaction medium. The conversion was high at pH 8 and decreased
as the pH increases, which might be due to formation of the cat-
alytically inactive ␮-oxo dimer of the MnTPPS at high pH values
[44].
Table 2
Effect of catalyst concentration on the oxidation of 2-aminophenol with H2O2 cat-
alyzed by Mn(TPPS).a
[Mn(TPPS)] (10−6 M)
APX %
–
10
35
62
70
3.2
4.9
10.6
a
For reactions conditions, see footnote a of Table 1. All reactions were carried out
The effect of catalyst concentration on the yield of APX is shown
in Table 2.
at pH 8.

S.H. El-Khalafy, M. Hassanein / Journal of Molecular Catalysis A: Chemical 363–364 (2012) 148–152
151
H
H
N
NH2
O
O
N
NH2
-2H+, -2e
O2
OAP
OH
NH
OH
O
-2H+
-2e
BQMI
O2
N
NH2
O
O
APX
Scheme 2.
Table 3
LCoII OAP
LCoII
+ OAP
Effect of [OAP] and [H2O2] on the oxidation of 2-aminophenol catalyzed by
Mn(TPPS).a
LCoIII OAPO2
LCoII OAP + O2
Entry
[Mn(TPPS)] (10−6 M)
H2O2 (mmol)
[OAP] (10−3 M)
APX %
1
2
3
4
5
4.9
4.9
4.9
4.9
4.9
5
10
20
10
10
2.7
2.7
2.7
1.35
5.4
50
62
44
74
29
NH2
LCoIII OAPO2
.
+
LCoII
+ HO2
O.
a
For reactions conditions, see footnote of Table 1. All reactions were carried out
at pH 8.
NH2
O.
NH2
NH
O
2
+
The yield of APX was high (70%) when the concentration of
Mn(III)TPPS was 10.62 × 10−6 M.
OH
The effect of variation of H2O2 concentration on the yield of
APX is shown in Table 3. The yield of APX increased from 50 to 62%
(Entries 1 and 2) when the concentration of H2O2 was increased
from 5 to 10 mmol. Further increases of the H2O2 concentration led
to a decrease in the yield of APX and an unidentified side products
was obtained. This could be due to degradation of Mn(III)TPPS at
higher concentration of H2O2.
BQMI
L: TPPS
Scheme 3.
(Scheme 3) [11,12]. The cobalt superoxo adduct reacts with 2-
aminophenol by abstracting H-atom forming 2-aminophenoxyl
radical which disproportionate leading to the key intermediate o-
benzo-quinone monoimine (Scheme 3).
The efficiency of Mn(III)TPPS as a catalyst in the oxidation of OAP
to APX was also evaluated at different concentrations of OAP at pH
8.0 (Table 3, Entries 2, 4, and 5). The best yield of APX was obtained
at catalyst/OAP ratio equal to 1/270 (Entry 4). The oxidation reac-
tion carried out at higher concentration of OAP gave lower yield of
APX (Entry 5). This could be due to the decrease in molar ratio of
oxidant and catalyst to OAP in the reaction mixture.
It is well known that o-benzoquinone monoimine (BQMI)
is the key intermediate in the oxidative coupling of OAP to
APX [6–8,14,15]. The overall reaction requires several oxidative
dehydrogenation steps involving OAP, molecular oxygen and o-
benzoquinone monoimine as reactants to produce APX (Scheme 2).
Cobalt superoxo adduct is known to be the active species in
the auto-oxidation of phenols catalyzed by cobalt(II) complex of
tetraphenyl-porphyrin [47]. Based on the results of the observed
rate dependence on 2-aminophenol concentration and pressure of
molecular oxygen, the proposed mechanism of auto-oxidation of
OAP catalyzed by Co(II)TPPS probably involves a superoxo deriva-
tive containing one 2-aminophenol molecule in the axial ligand
High valent oxomanganese intermediate is known to be the
active species in the oxidation of organic compounds with oxidants
such as peroxides, potassium monopersulfate and iodosylbenzene
catalyzed by Mn(III)porphyrins [36,48–51]. In order to identify the
nature of the oxo-manganese species in the oxidation reaction of
OAP with H2O2 catalyzed by Mn(III)TPPS, the oxidation reaction
was analyzed by UV–vis spectrophoto-meter. The UV–vis spec-
tra illustrated in Fig. 7 was obtained upon mixing OAP, deionized
water, buffer, Mn(III)TPPS and H2O2 consecutively. As can be seen
in Fig. 7a, the maximum absorbance observed at 468 nm as a typical
soret band of Mn(III)TPPS[51] was gradually decreased and the gen-
eration of a new broad band at 425 nm which gradually increased,
indicating the formation of oxomanganese(IV)TPPS species [49].
This oxomanganese(IV) derivative was stable up to the end of the
oxidation reaction of 2-aminophenol (Fig. 7b–h). Kamp and Lind-
say Smith reported also that the oxomanganese(IV) was the active
NH2
NH2
+
HO Mn (III)TPPS
+ O=Mn (IV) TPPS
O.
OH
Scheme 4.

152
S.H. El-Khalafy, M. Hassanein / Journal of Molecular Catalysis A: Chemical 363–364 (2012) 148–152
[5] T.M. Simándi, L.I. Simándi, M. Györ, A. Rockenbauer, A. Gömöry, Dalton Trans.
(2004) 1056.
3
2
1
0
[6] I.Cs. Szigyártó, T.M. Simándi, L.I. Simándi, L. Korecz, N. Nagy, J. Mol. Catal. A:
Chem. 251 (2006) 270.
[7] J. Kaizer, G. Baráth, R. Csonka, G. Speier, L. Korecz, A. Rockenbauer, L. Párkányi,
J. Inorg. Biochem. 102 (2008) 773.
[8] L.I. Simándi, S. Németh, N. Rumelis, J. Mol. Catal. 42 (1987) 357.
[9] F. Benedini, G. Galliani, M. Nali, B. Rindone, S. Tollari, J. Chem. Soc., Perkin Trans.
II (1963) 1985.
[10] K. Maruyama, T. Moriguchi, T. Mashino, A. Nishinaga, Chem. Lett. (1996)
819.
[11] L.I. Simándi, T.M. Barna, L. Korecz, A. Rockenbauer, Tetrahedron Lett. 34 (1993)
717.
[12] Z. Szeverényi, E.R. Milaeva, L.I. Simándi, J. Mol. Catal. 67 (1991) 251.
[13] M. Hassanein, M. Abdo, S. Gerges, S. El-Khalafy, J. Mol. Catal. A: Chem. 287
(2008) 52.
[14] J. Kaizer, R. Csonka, G. Speier, J. Mol. Catal. A: Chem. 180 (2002) 91.
[15] A.B. Zaki, M.Y. El-Sheikh, J. Evans, S.A. El-Safty, Polyhedron 19 (2000) 1317.
[16] S.A. El-Safty, J. Evans, M.Y. El-Sheikh, A.B. Zaki, Colloid Surf. A: Physicochem.
Eng. Aspects 203 (2002) 217.
[17] M.R. Maurya, S. Silkarwar, T. Joseph, S.B. Halligudi, J. Mol. Catal. A: Chem. 236
(2005) 132.
[18] M. Homma, A.F. Graham, Biochim. Biophys. Acta 61 (1962) 642.
[19] E. Frei, Cancer Chemother. Rep. 58 (1974) 49.
[20] U. Hollstein, Chem. Rev. 74 (1974) 625.
[21] J.T. Groves, T.E. Nemo, R.S. Myers, J. Am. Chem. Soc. 101 (1979) 1032.
[22] B. Meunier, Chem. Rev. 92 (1992) 1411.
[23] D. Mansuy, P. Battioni, J.P. Battioni, Eur. J. Biochem. 184 (1989) 267.
[24] D. Mansuy, Pure Appl. Chem. 59 (1987) 759.
[25] J.R. Lindsay Smith, in: R.A. Sheldon (Ed.), Metalloporphyrins in Catalysis Oxi-
dation, Marcel Deckker, New York, 1994 (Chapter 11).
[26] D. Mansuy, Coord. Chem. Rev. 125 (1993) 129.
[27] B.A. Arndtsen, R.G. Bergamm, T.A. Mobley, T.H. Petreson, Acc. Chem. Res. 28
(1995) 154.
a : at 0 min
b : after 26 min
c : after 44 min
d : after 54 min
e : after 60 min
f : after 120 min
g : after 150 min
h : after 270 min
h
g
f
e
a
d
c
b
300
400
500
600
Wavelength (nm)
Fig. 7. UV–vis absorption spectra after mixing of Mn(TPPS) (8.5 × 10−6 M), 2-
aminophenol (8.5 × 10−3 M), borax buffer (pH adjusted to 8) and H2O2 (0.08 M).
species in the oxidation of phenols by potassium monopersulfate
and manganese(III)tetra(N-methyl-2-pyridyl)porphyrin [36]. The
oxomanganese(IV)TPPS species reacts with OAP by abstracting H-
atom forming the 2-aminophenoxyl radical as shown in Scheme 4
[36]. The 2-aminophenoxyl radical then disproportionate leading
to the key intermediate o-benzoquinone monoimine and its further
conversion into the product APX.
[28] K.A. Jorgensen, Chem. Rev. 89 (1989) 431.
[29] B. Meunier, in: R.A. Sheldon (Ed.), Metalloporphyrins in Catalysis Oxidation,
Marcel Dekker, New York, 1994, p. 133 (Chapter 5).
[30] M. Hassanein, S. Gerges, M. Abdo, S. El-Khalafy, J. Mol. Catal. A: Chem. 240
(2005) 22.
[31] X.Y. Wang, R.J. Moterkaitis, A.E. Martell, Inorg. Chem. 23 (1984) 271.
[32] M. Forstin-Rio, D. Pujot, C. Bied-Charreton, M. Perree-Fauvet, A. Gaudemer, J.
Chem. Soc., Perkin Trans. 1 (1984) 1971.
[33] B. De Vismes, F. Bedioui, J. Devynck, C. Bied-Charreton, M. Perree-Fauvet, Nou-
veau J. Chem. 10 (1986) 81.
4. Conclusions
[34] E. Tarnaud, M. Forstin-Rio, C. Bied-Charreton, J. Mol. Catal. 72 (1992) 181.
[35] N. Colclough, J.R. Lindsay Smith, J. Chem. Soc., Perkin Trans. 2 (1994) 1139.
[36] N.W.J. Kamp, J.R. Lindsay Smith, J. Mol. Catal. A: Chem. 113 (1996) 131.
[37] H. Saleem, L.S. Kerry, Appl. Biol. Chem. Biotechnol. 845 (1997) 63.
[38] M. Fukushima, K. Tatsumi, J. Mol. Catal. A: Chem. 245 (2006) 178.
[39] H. Zeng, Q. Jian, Y. Zhu, X. Yan, X. Liang, H. Hu, Q. Liu, W. Lin, C.J. Guo, Porphyrins
Phthalocyanines 10 (2006) 96.
[40] C.W. Carter, Biochem. J. 22 (1928) 575.
[41] R. Gerdes, O. Bartels, G. Schneider, D. Worhle, G. Schulz-Ekloff, Int. J. Photoen-
ergy 1 (1999) 1.
The water soluble cobalt(II) tetra-(p-sulfophenyl)porphyrin
was proven to be an efficient catalyst for the oxidation
of 2-aminophenol with molecular oxygen to produce 2-
aminophenoxazine-3-one. A mechanism On the basis of kinetic
data was proposed assuming ternary complex formation between
catalyst, substrate and oxygen. The oxidation of 2-aminophenol
with hydrogen peroxide to 2-aminophenoxazine-3-one has
been found to be efficiently catalyzed by manganese(III)tetra(4-
sulfophenyl)porphyrin.
[42] M. Hassanein, S. Gerges, M. Abdo, S. El-Khalafy, J. Mol. Catal. A: Chem. 268
(2007) 24.
[43] T.S. Srivastava, M. Tsutsui, J. Org. Chem. 83 (1973) 2103.
[44] H. Turk, W.T. Ford, J. Org. Chem. 56 (1991) 2103.
[45] L. Michlaelis, M.L. Menten, Biochem. Z. 49 (1913) 333.
[46] H. Lineweaver, D. Burk, J. Am. Chem. Soc. 56 (1934) 658.
[47] X.-Y. Wang, R.J. Motekaitis, A.E. Martell, Inorg. Chem. 23 (1984) 271.
[48] W. Nam, I. Kim, M.H. Lim, H.J. Choi, J.S. Lee, H.G. Jang, Chem. Eur. J. 8 (2002)
2067.
The UV–vis spectra showed that the active intermediate in pro-
cess might be oxomanganese(IV)porphyrin.
References
[49] Z. Li, C.-G. Xia, C.-Z. Xu, Tetrahedron Lett. 44 (2003) 9229, and references
therein.
[50] Z. Li, C.-G. Xia, J. Mol. Catal. A: Chem. 214 (2004) 95.
[51] H.-J. Zhang, Y. Liu, Y. Lu, X.-S. He, X. Wang, X. Ding, J. Mol. Catal. A: Chem. 787
(2008) 80.
[1] R. Hage, A. Lienke, Angew. Chem. 118 (2006) 212.
[2] N. Duran, E. Esposito, Appl. Catal. B 28 (2000) 83.
[3] G. Strukul (Ed.), Catalytic Oxidation with Hydrogen Peroxide as Oxidant,
Kluwer, Dordrecht, 1992.
[4] T. Horváth, J. Kaizer, G. Speier, J. Mol. Catal. A: Chem. 215 (2004) 9.