Magnetic copper ferrite nanoparticles/TEMPO catalyzed selective oxidation of activated alcohols to aldehydes under ligand- and base-free conditions in water

Article abstract of DOI:10.1039/c4ra14152k

A novel, effective and sustainable strategy for the synthesis of aldehydes has been developed using inexpensive, readily available, oxygen-stable and recyclable CuFe₂O₄ nanoparticles as the catalyst. The corresponding substituted aldehydes were obtained in moderate to good yields by aerobic oxidation of aromatic alcohols in water under dioxygen atmosphere. Importantly, a ligand or a base was not necessary. The catalyst was completely recoverable with an external magnet and could be reused six times without significant loss of catalytic activity.

Full text of DOI:10.1039/c4ra14152k

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DOI: 10.1039/C4RA14152K
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ARTICLE TYPE
Magnetic Copper Ferrite Nanoparticles/TEMPO Catalyzed Selective
Oxidation of Activated Alcohols to Aldehydes under Ligand- and Base-
Free Conditions in Water
†
a
a
a
b
a
a
a
a
Xiao Zhu, Daoshan Yang,* Wei Wei, Min Jiang, Lulu Li, Xiangbing, Zhu, Jinmao You, and Hua Wang*
5
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
A novel, effective and sustainable strategy for the synthesis of
aldehydes has been developed using inexpensive, readily
transition metal catalyst, ligand together with strong base
conditions, metal contamination in the end products and
undesirable stoichiometric oxidants, which should still impede
their applications on a large scale. Therefore, a more green and
effective process is needed.
5
5
6
0
5
0
available,
oxygen-stable
and
recyclable
CuFe O4
2
1
0
nanoparticles as the catalyst. The corresponding substituted
aldehydes were obtained in moderate to good yields by
aerobic oxidation of aromatic alcohols in water under
dioxygen atmosphere. Importantly, a ligand or a base was not
necessary. The catalyst was completely recoverable with an
external magnet and could be reused six times without
significant loss of catalytic activity.
In view of the principles of green chemistry, the proposal of
reaction conditions, media and catalysts, is still challenging in the
9
current chemistry. Since catalysis has a tremendous impact on
“green chemistry”, optimization of existing chemical
1
5
transformations together with the development of practical,
environmentally friendly processes depend greatly on
10
improvement of catalyst performance. Recently, heterogeneous
catalysts have attracted much attention in organic transformations
due to their interesting reactivity as well as for economic and
environmental reasons. Particularly, a large number of recyclable
Introduction
Direct conversion of primary alcohols to the corresponding
1
aldehydes is still a pivotal reaction in organic synthesis. In
11
2
2
3
3
0
5
0
5
traditional oxidation processes, the oxidation of alcohols is
accomplished by use of stoichiometric amounts of inorganic
supported catalytic systems have been developed. For example,
Li and coꢀworkers reported an efficient palladium on graphene
oxidants such as CrO , KMnO , SeO , hypervalent iodine
3
4
2
2
65 catalyst for the selective oxidation of aromatic alcohols to
9f
compounds and toxic heavy metal salts. Unfortunately, these
oxidants might lead to the formation of quantities of unfriendly
waste in the environment such as nonꢀrecoverable toxic byꢀ
products, and large volumes of solid waste. In recent years,
corresponding carbonyl compounds. Very recently, Garcia’s
group developed an elegant work for the oxidative transformation
catalyzed by metalꢀorganic frameworks with the assistance of
12
TEMPO (2, 2, 6, 6ꢀtetramethylꢀ1ꢀpiperidinyloxy). Excellent as
these works are, the small size of catalyst particles might often
make their separation and recycling difficult, and the efficiency
of the recovered catalyst might be somewhat reduced as a result
of a filtration step.
3
4
5
transition metals such as Pd, Au, Cu, etc., or their
corresponding metal complexes have been widely applied in the
aerobic alcohol oxidation. As a pioneering work, Nakazawa and
coꢀworkers recently reported a first ironꢀcatalyzed method for
7
0
6
aerobic oxidation of alcohols to aldehydes. Nonꢀmetalcatalytic
Recently, magnetic nanoparticles (MNPs) have emerged as
systems for this oxidation transformation have also been attract 75 ideal catalysts or supports, and have been extensively used in
7
much attention, In 2014, Jahn and coꢀworkers reported that
TEMPO/tꢀBuONO system can catalyze primary and secondary
alcohols to the corresponding aldehydes and ketones,
organic transformations because of their easy preparation, large
surface area ratio, high dispersion property in organic solvents
and efficient separation by using an external magnet and without
8
13
respectively. However, in some cases, most of these methods
the need for filtration step.
Among all the magnetic
might suffer from some drawbacks such as the rarity and price
80 nanoparticles, copper(II) ferrite (CuFe O ) nanoparticles have
2 4
emerged as a powerful and excellent catalyst for many organic
transformations. Furthermore, from the viewpoint of green
a
14
The Key Laboratory of LifeꢀOrganic Analysis and Key Laboratory of
Pharmaceutical Intermediates and Analysis of Natural Medicine, School
of Chemistry and Chemical Engineering, Qufu Normal University, Qufu
2
chemistry, replacement of conventional hazardous organic
solvents by safe and green reaction media has always been a
thread in the sustainable chemistry. There is no doubt that, water
can be considered as an attractive solvent, because it is easily
available, nonꢀtoxic and environmentally friendly in the world.
Besides that, water is also known to enhance the reaction rates
4
0
73165, Shandong,China. Eꢀmail: yangdaoshan@tsinghua.org.cn;
85
huawang_qfnu@126.com;
b
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical
Biology (Ministry of Education), Department of Chemistry, Tsinghua
University, Beijing 100084, People_s Republic of China
4
5
1
5
†
Electronic Supplementary Information (ESI) available: Experimental
and to affect the selectivity of a lot of organic transformations.
details. See DOI: 10.1039/b000000x/
90 In addition, for economical and environmental reasons, there is
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DOI: 10.1039/C4RA14152K
an increasing demand for the use of dioxygen as an ideal oxidant
for many oxidation reactions due to its abundance, low cost and
nontoxicity. In continuation of our endeavors to develop
Initially, phenylmethanol (1a) was selected as the model
substrate to optimize the reaction conditions, including the choice
of solvent, temprature and the amount of TEMPO under a
dioxygen atmosphere (Table 1). Firstly, a range of solvents such
1
6
CuFe O ꢀcatalyzed organic transformations, we herein report a
2
4
5
green, practical and efficient CuFe O ꢀcatalyzed aerobic 40 as H O, Toluene, DMF, DMSO and THF were investigated in the
2
4
2
oxidation of aromatic alcohols to aldehydes by using
environmentally benign water as the solvent under dioxygen
atmosphere. Notably, when we were performing these studies,
Lipshutz and his coworkers reported an elegant example of the
presence of 0.1 equiv of CuFe O nanoparticles and 6.25 mol %
TEMPO (2,2,6,6ꢀTetramethylpiperidine 1ꢀoxyl) (relative to
2
4
amount of 1a) under dioxygen atmosphere (entries 1ꢀ5), H O and
2
THF gave the highest yield among the solvents tested (entry 1
10
direct oxidation of activated alcohols to aldehydes or ketones 45 and 5 ), and we chose the most green and environmentally
17
using CuBr/TEMPO as the catalyst using water as the solvent.
friendly water as the solvent. The reason might be the optimum
oxygen solubility of water. Besides that, the hydrogen bonding
interaction between water and alcohols which could active the
Results and Discussion
The copper(II) ferrite nanoparticles were prepared according to
alcohols can not be excluded. We attempted different temperature
the literature procedure, and were characterized by Xꢀray 50 (compare entries 1, 6ꢀ8), and 100 C was optimal. The yield was
1
8
o
15
diffraction (Fig. 1). The energyꢀdispersive Xꢀray spectroscopy
shows that the spheres are composed of Cu, Fe and O, as
expected (Fig 1, ESI†). Moreover, the diffraction patterns of all
the peaks are in agreement with the standard XRD pattern
not significantly improved when the reaction time was prolonged
to 48h, at 30°C, 60°C and 90°C respectively. The reaction yield
decreased when the amount of TEMPO was lowered (entries1, 9ꢀ
10). Control experiments confirmed that the desired
(
JCPDS34ꢀ0425), so are the ones after three usages. Also, as can 55 benzaldehyde was not formed in the absence of the catalyst
20
be seen from the SEM and TEM images, the CuFe O4
nanoparticles could remain well in a similar state, even after third
cycles. (Fig 2 and Fig 3).
(entries 11), and it gave a moderate yield under air atmsphere.
Considering the importance of bases and ligands in the traditional
Cu/TEMPO oxidative systems, we added 2.0 mmol KOH in the
standard reaction system, however, the reaction efficiency was
not obviously enhanced. The reason might be the large surface
area ratio of CuFe O , and make it easy to coordinate with
2
60
2
4
alcohol and TEMPO without bases and ligands(see scheme 1,
plausible mechanism) . As a result, the optimized reaction
conditions were identified as using CuFe O4 nanoparticles(10
2
o
65
mol%), TEMPO (1.25 mol%), H O (2mL) at 100 C under
2
dioxygen atmosphere.
a
Table 1 Optimization of the reaction conditions
25
Fig. 1 XRD spectrum of native CuFe O catalyst. (b) XRD
2
4
3
spectrum of reused CuFe O catalyst after th cycle
2
4
o
b
Entry
Solvent
Temp ( C)
Yield (%)
1
2
3
4
5
6
7
8
9
H
2
O
100
100
100
100
100
30
95
Toluene
DMSO
DMF
40
[
[
f]
f]
–
–
THF
92
[
f]_[g]
[
H
2
H
2
H
2
O
O
O
–
g]
60
75, 76
83, 88
75
[g]
90[
Fig. 2 (a) SEM images of the fresh CuFe O nanoparticles. (b)
2
4
c]
th
H O
100
2
30
SEM image of the CuFe O nanoparticles after 3 cycle.
2 4
[d]
1
1
1
1
0
1
2
3
H
2
H
2
H
2
H
2
O
O
O
O
100[
80
e]
[f]
100
–
[h]
100
100
64
87
[i]
a
Reaction conditions: Benzyl alcohol (1a; 2 mmol), catalyst (0.1 mmol),
b
70
TEMPO (0.125 mmol), H O (2 mL), under O atmosphere. Isolated yield.
2
2
c
d
e
f
TEMPO (0.025 mmol). TEMPO (0.05 mmol). No catalyst. Noti
g
h
detected. The reaction time prolonged to 48h. Under air atmosphere.
2
.0 mmol KOH was added.
As shown in Table 2, the scope of substrates was investigated,
Fig. 3 (a) TEM image of the fresh CuFe O nanoparticles. (b) 75 and all the examined substrates provided the corresponding
2
4
th
TEM image of the CuFe O nanoparticles after 3 cycle.
aldehydes in moderate to good yields. For substituted aromatic
alcohols, the substrates containing electronꢀwithdrawing groups
2
4
35
2
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exhibited higher reactivity than the others. For example, a low
yield of the oxidative product (49%) was obtained from (4ꢀ
nitrophenyl)methanol (Table 2, entry 4). Thiophenꢀ2ꢀylmethanol
1
0
96%
72%
(
1m) was a good substrate in this transformation, and afforded
corresponding aldehyde in 62% yield. In addition, 3ꢀphenylpropꢀ
ꢀenꢀ1ꢀol (1n) was also tolerated in this transformation, thus
5
2
11
generating 2n in 85% yield (Table 2, entry 14). Although primary
alcohols showed high reactivity, unfortunately, secondary
benzylic alcohols were poor substrates (Table 2, entry 15). The
cascade reactions could tolerate some functional groups such as
methyl, nitro, ether, CꢀF bond, CꢀCl bond and CꢀBr bond, which
could be used for further transformations at the substituted
positions.
1
0
1
2
79%
1
1
3
4
62%
85%
a,b,
2 4
Table 2 CuFe O ꢀcatalyzed synthesis of aldehydes from alcohols
1
5
1
5
trace
Entry
1
1
2
Yield (%)
a
Reaction conditions: the substituted alcohols (1a; 2 mmol), CuFe
0.2 mmol), TEMPO (0.125mmol), H O(2 ml), 100 °C, 24 h, under O
Isolated yield
2
O
2
.
4
b
(
2
95%
.
We also studied the recyclability of the catalyst. For this, we
investigated the CuFe O ꢀcatalyzed oxidation of phenylmethanol
2
2
3
0
5
0
2
4
(
1a) to benzaldehyde (2a) under the optimized conditions. After
2
3
79%
86%
completion of the reaction, the reaction mixture was cooled to
room temperature, and the catalyst was magnetically separated
from the reaction mixture (Fig. 4), washed ethanol/acetone and
o
dried at 100 C for 2 h and then used directly for further catalytic
reactions. The catalyst showed no significant loss of activity after
six cycles as illustrated in Fig. 5. This illustrate a promising
approach from sustainable and practical chemistry viewpoints.
Then, We investigated the leaching of metal from the CuFe O
2
4
4
5
6
49%
87%
84%
nanoparticles. After completion of the reaction, the filtrate was
tested by the AES (Atomic Emission Spectroscopy) technique, it
was found that the leaching of Cu and Fe in three consecutive
cycles was ≤ 0.5 ppm.
CH OH
2
Br 1f
35
Fig. 4 CuFe O after oxidation reaction dispersed (a); magnetic
separation of the catalyst at ambient temperature with a NdꢀFeꢀB
based magnet (b)
2
4
7
8
94%
80%
9
66%
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(0.25 mmol, 39 mg), and aromatic alcohols (2) (2 mmol). The
reaction was performed at 100 ℃ for 24 h under dioxygen
atmosphere in the sealed tube. After being cooled to room
temperature, the mixture was extracted with ethyl acetate (3×10
mL). The combined organic layer was concentrated, and the
residue was purified by flash chromatography on silica gel
4
4
5
5
0
5
0
5
(eluent: petroleum ether/ethyl acetate = 30:1 to 20:1) to afford the
target product (2a-2n).
Recycling of the catalyst: After completion of the
reaction, the magnetic nanoparticles were recovered by using a
NdꢀFeꢀB based magnet and the organic solvents containing the
products collected with a pipet. The recovered catalyst was
Fig. 5 Yields from recycled copper (II) ferrite catalyst
o
washed with ethanol and then acetone, and was dried at 120 C in
The control experiments reveal that TEMPO and CuFe O are
2
4
an oven for 2 h to provide the recycling CuFe O about 46.2 mg.
5
0
5
0
indispensable parts of this efficacious catalytic system (entries 1
and 9ꢀ11, Table 1). Although the mechanism for the present
oxidation pathway is not yet clear, according to the previous
report a proposal mechanism would be herein presented (Scheme
2
4
20
Benzaldehyde (2a). Eluent petroleum ether/ethyl acetate (30:1).
Yield 95% (201 mg from 216 mg starting material). H NMR
1
(
CDCl , 400 MHz, ppm) δ 10.0 (s, 1H), 7.87 (d, 2H, J = 8.0 Hz),
3
1
3
7.66 (t, 1H, J = 8.0 Hz), 7.51 (d, 2H, J = 8.0 Hz). C NMR
1
). First, TEMPO coordinate to the CuFe O nanoparticles to lead
2 4
(
4
CDCl , 200 MHz, ppm) δ 192.5, 136.4, 134.5, 129.7, 129.0.
-Chlorobenzaldehyde (2b). Eluent petroleum ether/ethyl
1
1
2
to complex A. Subsequently, Species A in combination with
alcohols lead to the formation of the species B (In CuFe O , Cu is
3
20
2
4
acetate (20:1). Yield 79% (221 mg from 284 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.99 (s, 1H), 7.83
60 (d, 2H, J = 8.0 Hz), 7.52 (d, 2H, J = 8.0 Hz). C NMR (CDCl3,
2
present as Cu(II) in the crystal lattice, So alcohols and TEMPO
might be coordinate to Cu(II), which is consistent with the
1
3
13
5b,19a
previous reports
), which was considered as the intermediate
00 MHz, ppm) δ 190.8, 140.9, 134.7, 130.9, 129.5.
species in the present catalytic system. Intramolecular transfer of
the α and βꢀhydrogen would afford aldehydes, CuFe O , and
20
4
-Methoxybenzaldehyde (2c). Eluent petroleum ether/ethyl
2
4
acetate (25:1). Yield 86% (234 mg from 276 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.89 (s, 1H), 7.84
(d, 2H, J = 8.0 Hz), 7.01 (d, 2H, J = 8.0 Hz), 2.89 (s, 3H).
NMR (CDCl , 200 MHz, ppm) δ 190.8, 164.6, 132.0, 130.0,
1
4
(
NMR (CDCl , 400 MHz, ppm) δ 10.18 (s, 1H), 8.42 (d, 2H, J =
8
ppm) δ 190.3, 151.2, 140.1, 130.5, 124.3.
4
acetate (30:1). Yield 87% (209 mg from 244 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.96 (s, 1H), 7.82
TEMPOH. TEMPOH was oxidized by dioxygen to TEMPO and
1
19b
water. Further investigations on the more detailed mechanism
are ongoing.
3
1
3
6
7
7
8
8
9
5
0
5
0
5
0
C
3
14.4, 55.6.
-nitrobenzaldehyde (2d). Eluent petroleum ether/ethyl acetate
20
1
30:1). Yield 49% (148 mg from 306 mg starting material). H
3
13
.0 Hz), 8.10 (d, 2H, J = 8.0 Hz). C NMR (CDCl , 200 MHz,
3
20
-Methylbenzaldehyde (2e). Eluent petroleum ether/ethyl
1
3
1
3
(d, 2H, J = 8.0 Hz), 7.43 (d, 2H, J = 8.0 Hz), 2.42 (s, 3H).
C
NMR (CDCl , 200 MHz, ppm) δ 193.1, 145.7, 134.5, 130.2,
1
4
acetate (30:1). Yield 84% (309 mg from 372 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.97 (s, 1H), 7.54
(d, 2H, J = 8.0 Hz), 7.68 (d, 2H, J = 8.0 Hz). C NMR (CDCl ,
3
2
Scheme 1 Plausible mechanism
3
27.7, 21.9.
-Bromobenzaldehyde (2f).
20
Eluent petroleum ether/ethyl
Experimental Section
1
3
13
General experimental procedures
00 MHz, ppm) δ 191.0, 135.1, 132.4, 131.0, 129.7.
25
30
35
All reagents and solvents were obtained from commercial
suppliers and used without further purification. Flash
chromatography was performed on silica gel (200 ~ 300 mesh).
17
3
,5-Dimethoxybenzaldehyde
(2g).
Eluent
petroleum
ether/ethyl acetate (20:1). Yield 94% (315 mg from 336 mg
starting material). H NMR (CDCl , 400 MHz, ppm) δ 9.88 (s,
1
2
3
1
3
1
13
H and C NMR data were recorded at 400 and 100 MHz on a
13
H), 6.99 (s, 2H), 6.68 (s, 1H), 3.83 (s, 6H). C NMR (CDCl3,
BRUKER 400 spectrometer. Chemical shifts (δ) are expressed in
00 MHz, ppm) δ 191.8, 161.2, 138.4, 107.1, 107.0, 55.6.
parts per million (ppm) coupling constants (J) are in Hz. Proton
21
-Bromobenzaldehyde (2h).
Eluent petroleum ether/ethyl
1
13
and carbon magnetic resonance spectra ( H NMR and C NMR)
were recorded using tetramethylsilane (TMS) in the solvent of
acetate (25:1). Yield 80% (293 mg from 370 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.99 (s, 1H), 8.04
1
3
1
CDCl3 as the internal standard ( H NMR: TMS at 0.00 ppm,
(s, 1H), 7.84 (d, 1H, J = 8.0 Hz), 7.77 (d, 1H, J = 8.0 Hz), 7.45 (t,
1
3
CDCl at 7.28 ppm; C NMR: CDCl at 77.0 ppm).
13
3
3
1
1
H, J = 8.0 Hz). C NMR (CDCl , 200 MHz, ppm) δ 190.7,
3
General procedure for synthesis of aldehydes
38.0, 137.3, 132.4, 130.6, 128.4, 123.4.
2
a-2n: A 25 mL Schlenk tube was charged with a magnetic
stirrer and H O (2.0 mL). CuFe O (0.2 mmol, 47.8 mg), TEMPO
2
2
4
4
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4
-(Trifluoromethyl)benzaldehyde (2i). Eluent petroleum
of Shandong Province Higher Educational Science and
Technology Program (J13LD14), and the Scientific Research
Foundation of Qufu Normal University (BSQD 2012021).
ether/ethyl acetate (30:1). Yield 66% (230 mg from 352 mg
starting material). H NMR (CDCl , 400 MHz, ppm) δ 10.13 (s,
1
1
3
13
H), 8.04 (d, 2H, J = 8.0 Hz), 7.84 (d, 2H, J = 8.0 Hz). C NMR
Notes and references
5
(CDCl , 200 MHz, ppm) δ 191.1, 138.7, 135.8 (d, J = 26.1 Hz),
3
1
3
31.1, 129.9, 126.1(d, J = 4.1 Hz).
-Methoxybenzaldehyde (2j). Eluent petroleum ether/ethyl
60 1. R.A. Sheldon, I.W.C.E. Arends, A. Dijksman, Catalysis Today., 2000,
57,157ꢀ166.
2
0
2
. (a) M. Hudlicky, Oxidation in Organic Chemistry, ACS Monograph
Series, American Chemical Scociety, Washington, DC, 1990; (b) J.
March, Advanced Organic Chemistry: Reactions, Mechanisms, and
Structure, 4th edn, John Wiley & Sons, New York, 1992.
acetate (20:1). Yield 96% (261 mg from 276 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.98 (s, 1H), 7.47ꢀ
7.45 (m, 2H), 7.40 (s, 1H), 7.20ꢀ7.18 (m, 1H), 3.87 (s, 3H).
NMR (CDCl , 200 MHz, ppm) δ 192.1, 160.2, 137.9, 130.1,
1
3
acetate (20:1). Yield 72% (285 mg from 400 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 9.98 (s, 1H), 7.64ꢀ
7
1
1
3
1
3
1
1
2
2
3
3
0
5
0
5
0
5
C
6
7
7
5
0
5
3
3. For selected examples, see: (a) G. J. ten Brink, I. W. C. E. Arends, R. A.
Sheldon, Science., 2000, 287, 1636ꢀ1639; (b) M. S. Sigman, D. R.
Jensen, Acc. Chem. Res., 2006, 39, 221ꢀ229; (c) C. Liu, S. Tang, A. Lei,
Chem. Commun., 2013, 49, 1324ꢀ1326; (d) G. F. Zhang, Y. Wang, X.
Wen, C. R. Ding, Y. Li, Chem. Commun., 2012, 48, 2979ꢀ2981.
23.5, 121.5, 112.2, 55.5.
-Phenoxybenzaldehyde (2k). Eluent petroleum ether/ethyl
1
3
4. For selected examples, see: (a) B. T. Guan, D. Xing, G. X. Cai, X. B.
Wan, N. Yu, Z. Fang, L. P. Yang, Z. J. Shi, J. Am. Chem. Soc., 2005,
.61 (m, 2H), 7.54ꢀ7.49 (m, 2H), 7.42ꢀ7.38 (m, 2H), 7.33ꢀ7.29 (m,
H), 7.20 (t, 1H, J = 8.0 Hz), 7.07 (t, 1H, J = 8.0 Hz). C NMR
13
1
27, 18004ꢀ18005; (b) H. Miyamura, R. Matsubara, Y. Miyazaki and S.
Kobayashi, Angew. Chem., Int. Ed., 2007, 46, 4151ꢀ4154; (c) B.
Karimi, F. K. Esfahani, Adv. Synth. Catal., 2012, 354, 1319ꢀ1326.
. For selected examples, see: (a) Z. Lu, T. Ladrak, O. Roubeau, J. van
der Toorn, S. J. Teat, C. Massera, P. Gamez, J. Reedijk, Dalton Trans.,
2009, 3559ꢀ3570; (b) J. M. Hoover, B. L. Ryland, S. S. Stahl, J. Am.
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(CDCl , 200 MHz, ppm) δ 191.6, 158.4, 156.2, 138.1, 130.5,
3
1
30.1, 124.7, 124.6, 124.2, 119.5, 118.2.
5
4-Fluorobenzaldehyde (2l). Eluent petroleum ether/ethyl acetate
1
(30:1). Yield 79% (196 mg from 252 mg starting material). H
NMR (CDCl , 400 MHz, ppm) δ 9.97 (s, 1H), 7.91 (d, 2H, J =
8
ppm) δ 167.5 (d, J = 10.1 Hz), 132.9, 132.6 (d, J = 26.1 Hz),
116.3(d, J = 3.1 Hz).
Thiophene-2-carbaldehyde (2m). Eluent petroleum ether/ethyl
acetate (20:1). Yield 62% (139 mg from 228 mg starting
material). H NMR (CDCl , 400 MHz, ppm) δ 10.01 (s, 1H),
7
3
1
3
80
.0 Hz), 7.21 (d, 2H, J = 8.0 Hz). C NMR (CDCl , 200 MHz,
3
6. M. Kamitani, M. Ito, M. Itazaki, H. Nakazawa, Chem. Commun., 2014,
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3
4
112ꢀ4113; (c) L. Wang, J. Li, H. Yang, Y. Lv, S. Gao, J. Org. Chem.,
1
3
.87ꢀ7.83 (m, 2H), 7.29 (t, 1H, J = 4.0 Hz). C NMR (CDCl3,
2012, 77, 790ꢀ794.
200 MHz, ppm) δ 183.2, 144.2, 136.2, 135.5, 128.6.
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1
7
1
(b) M. B. Gawande, P. S. Brancoa, R. S. Varma, Chem. Soc. Rev., 2013,
(30:1). Yield 85% (224 mg from 268 mg starting material). H
4
2, 3371ꢀ3393; (c) D. Wang, Didier Astruc, Chem. Rev., 2014, 114,
NMR (CDCl , 400 MHz, ppm) δ 9.73 (s, 1H), 9.71 (s, 1H), 7.59ꢀ
3
6
949ꢀ6985 and references therein.
7
.57 (m, 4H), 7.47ꢀ7.44 (m, 6H), 6.75 (d, 1H, J = 8.0 Hz); 6.70 (d,
1
0. Y. Wang, X. Wang, M. Antonietti, Angew. Chem. Int. Ed., 2012, 51,
1
3
1H, J = 8.0 Hz). C NMR (CDCl , 200 MHz, ppm) δ 193.7, 95 68ꢀ89.
3
1
1. For selected examples, see: (a) T. Mallat, A. Baiker, Chem. Rev., 2004,
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52.8, 134.0, 131.3, 129.1, 128.6, 128.5.
1
Couclusions
A. Dijksman, Acc. Chem. Res., 2002, 35, 774ꢀ781; (c) K. Mori, T. Hara,
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magnetic copper ferrite nanoparticleꢀcatalyzed method for
aerobic oxidation of primary alcohol to aldehyds. The method is
of the following advantages: (a) oxygenꢀstable and recyclable
4
0
1
37, 177ꢀ185.
copper ferrite nanoparticle as the catalyst; (b) environmentally 105 12. A. Dhakshinamoorthy, M. Alvaro, H. Garcia, ACS Catal., 2011, 1,
4
8ꢀ53.
friendly water as the solvent; (c) without addition of any base,
ligand or additive; (d) easy workup procedure; (e) outstanding
tolerance of functional groups. All these results meet the
requirements of green and sustainable chemistry, so the present 110
method will attract much attention in academic and industrial
fields. Further studies to catalyze other chemical reaction with
copper(II) ferrite magnetic nanoparticles are ongoing.
1
3. (a) L. M. Rossi, N. J. S. Costa, F. P. Silva, R. Wojcieszak, Green
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5
14. For selected examples, see: (a) S. Yang, C. Wu, H. Zhou, Y. Yang, Y.
1
1
15
20
Zhao, C. Wang, W. Yang, J. Xu, Adv. Synth. Catal., 2013, 355, 53ꢀ58;
5
0
Acknowlegement
(b) A. Dandia, A. K. Jain, S. Sharma, RSC Advances., 2013, 3, 2924ꢀ
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1
934; (c) S. M. Baghbanian, M. Farhang, RSC Adv., 2014, 4, 11624ꢀ
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The authors gratefully acknowledge the financial support from
the National Natural Science Foundation of China (Nos.
117ꢀ125. (e) Zhang, R.; Liu, J.; Wang, S.; Niu, J.; Xia, C.; Sun, W.
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Kundu, D.; Chatterjee, T.; Ranu, B. C. Adv. Synth. Catal. 2013, 355,
2
1302110, 21302109 and 21375075), the Taishan Scholar
Foundation of Shandong Province, the Natural Science
Foundation of Shandong Province (ZR2013BQ017), the Project
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