Oxidation of phenol catalyzed by immobilized phthalocyanine complexes

Article abstract of DOI:10.1016/j.mencom.2018.03.030

Immobilized phthalocyanine complexes of Co ⁱⁱ and Cu ⁱⁱ manifest higher catalytic activity in the oxidation of phenol with hydrogen peroxide than individual complexes.

Full text of DOI:10.1016/j.mencom.2018.03.030

Mendeleev
Communications
Mendeleev Commun., 2018, 28, 198–199
Oxidation of phenol catalyzed by immobilized phthalocyanine complexes
Yana B. Platonova,*a Aleksei S. Morozov,b,c Ivan D. Burtsev,a Yuliya S. Korostei,d
Vasilii Yu. Ionidi,e Boris V. Romanovskya and Larisa G. Tomilovaa,d
a Department of Chemistry, M. V. Lomonosov Moscow State University, 119991 Moscow, Russian Federation.
Fax: +7 495 939 0290; e-mail: knoposk@gmail.com
b Department of Biology, M. V. Lomonosov Moscow State University, 119991 Moscow, Russian Federation
c JSC ‘Advanced Medical Technologies’, 107045 Moscow, Russian Federation
d Institute of Physiologically Active Compounds, 142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 496 524 9508; e-mail: tom@org.chem.msu.ru
e D. V. Skobeltsyn Institute of Nuclear Physics, M. V. Lomonosov Moscow State University, 119991 Moscow,
Russian Federation
DOI: 10.1016/j.mencom.2018.03.030
R
R
OH
O
O
N
N
N
Immobilized phthalocyanine complexes of Coii and Cuii
manifest higher catalytic activity in the oxidation of phenol
with hydrogen peroxide than individual complexes.
N
N
H2O2, cat.
N
M
N
N
cat.
R
R
M = Co, R = But
M = Cu, R = SO3Na
Selective oxidation of phenols to quinones is a key stage in
the synthesis of vitamins and valuable synthetic precursors.1,2
Quinones are important intermediates in organic synthesis and
components of natural biologically active compounds.3–5 Among
Phthalocyanine complexes 2–4 were used as the catalysts to
oxidize phenol with hydrogen peroxide in aqueous medium
(Scheme 2).‡ The reaction progress was controlled by TLC. The
catalyst stability was monitored by absorption in the visible region.
When tert-butyl substituted cobalt phthalocyanine 1 was
used, hydrogen peroxide caused irreversible catalyst oxidation
resulting in its gradual destruction under homogeneous catalysis
the oxidants in question,6–13 the most popular are air oxigen
,
hydrogen peroxide, and tert-butyl hydroperoxide. Hydrogen per-
oxide being a ‘green’ oxidant (although currently more expensive
than molecular oxygen) can oxidize phenols under mild condi-
tions in the presence of a broad range of catalysts.6,14,15 Phthalo-
cyanine complexes of transition metals tested recently, especially
under photocatalytic oxidation conditions,16–21 were mainly used
as homogeneous catalysts. Such procedures have a number of
drawbacks, in particular, isolation and purification of products
are complicated.
In this study, we aimed at creating a heterogeneous catalyst
for the model oxidation of phenol using immobilized phthalo-
cyanine complexes on polymer supports with highly developed
surfaces. Several types of supports on which phthalocyanine com-
plexes were immobilized by adsorption from saturated solutions
and by covalent immobilization were investigated. Melamine
sponge, Nafen nanofibers and modified super cross-linked poly-
styrene PS-3 were selected as the supports. According to the low-
temperature nitrogen adsorption method (in BET approximation),
their specific surface areas were 800, 155 and 1100 m2 g–1,
respectively. Furthermore, we performed covalent immobiliza-
tion of cobalt(ii) 2-hydroxy-9(10),16(17),23(24)-tri-tert-butyl-
phthalocyanine 1 on styrene–divinylbenzene copolymer PS-7
activated by incorporation of chloromethyl groups and thus
obtained catalyst 2 (Scheme 1).†
But
But
N
N
N
N
N
KI, DIPEA, LiOH/DMF
Co
N
N
N
OH
But
1
But
But
N
N
N
N
Co
N
N
N
N
O
But
CH2
CH2Cl
CH2Cl
PS-7
2
Scheme 1
†
‡
Phthalocyanine immobilization procedure. A 0.5% solution of complex
Phenol oxidation procedure. The catalytic experiment was carried out
1 in DMF (0.3 ml), KI (10 mg), diisopropylethylamine (0.65 ml) and
LiOH·H2O (20 mg) were added to a mixture of PS-7 (a chloromethylated
styrene–divinylbenzene copolymer) (300 mg) in DMF (3 ml). The mix-
ture was kept at 110°C for 10 h. After that, the granules were filtered off
and sequentially washed with H2O, EtOH, acetone and toluene and then
dried in air.
at room temperature in a static reactor equipped with a magnetic stirrer
and an air-cooled condenser. Phenol (1 g) in H2O (10 ml), a phthalocyanine
catalyst (0.5 mol%) and a 37% aqueous H2O2 solution (1.5 ml) were
used in the reaction that was performed for 2 h. The reaction progress was
monitored by TLC. Upon reaction completion, the degree of conversion
and the yield of the target product were calculated.
© 2018 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
– 198 –

Mendeleev Commun., 2018, 28, 198–199
R
R
50
OH
O
O
N
M
N
40
H2O2,
cat. 2–4
N
N
30
20
10
0
N
N
N
N
1
2
R
R
1
2
3
4
5
3 M = Co, R = But
4 M = Cu, R = SO3Na
Cycles
Figure 3 Phenol conversion on catalysts: (1) cat. 4/melamine sponge, (2)
cat. 4/Nafen.
Scheme 2
conditions. To improve stability and activity of the catalyst, it
was immobilized, which caused increase in phenol conversion
(Figure 1).
1 and 2). UV-VIS spectroscopic data showed that complex 4
manifested high resistance to both the oxidant used in this process
and desorption from substrates. The enhanced resistance of
catalyst 4 to oxidation may be due to the presence of electron-
withdrawing substituents in the ligand, in contrast to 3 containing
We found that catalyst oxidation also occurred under hetero-
geneous catalysis conditions, however, it was much more slow.
According to Figure 1, immobilized phthalocyanines manifested
noticeably higher activity than individual complexes, though
phenol conversion was insufficient. In the case of covalently
immobilized on polystyrene catalyst 2, phenol conversion was
higher than in the case of the catalysts physically adsorbed on
various supports. Even traces of 1 were not detected in the reac-
tion media (UV-VIS control). Consequently, in the cases of both
the covalent immobilization on styrene–divinylbenzene copolymer
PS-7 and the application on the surface (melamine sponge, Nafen
nanofibers and modified super cross-linked polystyrene PS-3) by
adsorption, the catalyst leaching did not occur.
tert-butyl electron-donating groups. Based on our previous results 6
,
it can be stated that immobilized complex 4 is a more stable
catalyst than immobilized iron(iii) analogue of complex 3. This
allowed us to increase the yield of 1,4-benzoquinone and to
reduce the catalyst consumption.
In summary, solid supported sulfonated phthalocyanine com-
plexes seem promising catalysts for hydrogen peroxide oxidation
of phenol into benzoquinone. The studies of other phthalocyanine
complexes with ligands containing electron-withdrawing substi-
tuents for this catalytic oxidation are currently in progress.
To solve the problem of low catalyst stability under oxidizing
conditions, we tested H2O2-resistant sulfo-substituted copper
phthalocyanine 4. As phenol conversion was low in the presence
of this complex, we decided to place it on a heterogeneous support.
It appeared that adsorption on hydrophobic PS-3 polystyrene
was insufficient, since complex 4 was easily washed off with
water or other polar solvents. In the cases of melamine sponge
or Nafen fibers, the copper complex was perfectly adsorbed on
the support surface and was not washed off during the reaction.
With these catalysts, the phenol conversion considerably increased
in comparison with that in the presence of non-adsorbed complex 4
(Figure 2).
Catalyst recycling was demonstrated for the melamine sponge
or Nafen fiber supported complexes. The catalysts were separated,
washed with water and reused. After 5 cycles, their efficiency
remained practically unchanged (Figure 3).
It is of note that supported catalyst 4 provides higher phenol
conversion as compared with immobilized catalyst 3 (see Figures
This study was supported by the Russian Science Foundation
(grant no. 17-13-01197).
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Received: 7th July 2017; Com. 17/5303
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