Baeyer-Villiger oxidation of cyclohexanone by molecular oxygen with Fe-Sn-O mixed oxides as catalysts

Article abstract of DOI:10.1002/aoc.3314

Fe-Sn-O mixed oxides were synthesized and used as catalysts for Baeyer-Villiger oxidation of cyclohexanone, which showed both high catalytic activity and selectivity. X-ray powder diffraction and scanning electron microscopy suggested that the Fe-Sn-O catalysts had a tetragonal structure with a grain size of 29.3 nm. An ε-caprolactone yield as high as 98.8% was obtained in a small-scale experiment (5 mmol of cyclohexanone). In a scale-up test (20 mmol of cyclohexanone), the cyclohexanone conversion and ε-caprolactone yield were 96.7 and 96.5%, respectively. In addition, the catalysts can be reused five times without any major decline in catalytic activity.

Full text of DOI:10.1002/aoc.3314

Full Paper
Received: 27 November 2014
Revised: 11 February 2015
Accepted: 2 March 2015
Published online in Wiley Online Library: 30 April 2015
(wileyonlinelibrary.com) DOI 10.1002/aoc.3314
Baeyer–Villiger oxidation of cyclohexanone by
molecular oxygen with Fe–Sn–O mixed oxides
as catalysts
Yongli Ma, Zhengyong Liang*, Shuxiao Feng and Yadong Zhang*
Fe–Sn–O mixed oxides were synthesized and used as catalysts for Baeyer–Villiger oxidation of cyclohexanone, which showed both
high catalytic activity and selectivity. X-ray powder diffraction and scanning electron microscopy suggested that the Fe–Sn–O
catalysts had a tetragonal structure with a grain size of 29.3nm. An ε-caprolactone yield as high as 98.8% was obtained in a
small-scale experiment (5mmol of cyclohexanone). In a scale-up test (20 mmol of cyclohexanone), the cyclohexanone conversion
and ε-caprolactone yield were 96.7 and 96.5%, respectively. In addition, the catalysts can be reused five times without any major
decline in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.
Keywords: Baeyer–Villiger oxidation; molecular oxygen; cyclohexanone; Fe–Sn–O mixed oxides
In the study reported here, we prepared Fe–Sn–O mixed oxides
using a simple procedure. And the Fe–Sn–O catalysts were easily
Introduction
The Baeyer–Villiger (B-V) oxidation reaction, originating from the
1890s, provides a method for converting ketones to the corre-
sponding lactones or esters, which are important intermediates in
the chemical and drug industries.[1-7] However, traditional oxidants
used in B-V oxidation are generally peroxonitrates which might
erode the reaction equipment and pollute the environment.[6,8-10]
Therefore, environmentally friendly oxidants have attracted consid-
erable attention.[11,12]
separated from the reaction system. Further, the catalyst showed
good reusability and high catalytic ability for several other ketones.
It has been reported that the Fe–Sn–O catalyst has a higher activity
but a shorter lifetime.[26] But the Fe–Sn–O catalyst prepared in our
study can be reused five times without significant loss in activity
and selectivity.
With water being the only by-product, hydrogen peroxide has
been widely used as an environmentally friendly oxidant in organic
synthesis research. Lei et al.[13] reported that cyclohexanone could
be oxidized using hydrogen peroxide through a reaction catalyzed
by palygorskite-supported Sn complexes, affording the corre-
sponding ester with selectivity for the product of 90–99%. Corma
et al.[14] reported that tin–zeolite with 1.6wt% tin incorporated into
the framework showed high selectivity for the B-V oxidation of cy-
clohexanone by hydrogen peroxide. Both palygorskite (Mg, Al) sites
which are octahedrally coordinated can be easily exchanged.
Sn-exchanged palygorskite and Sn-exchanged Mg–Al hydrotalcite
are active and selective for the B-V oxidation of cyclic ketones with
H2O2.[15] However, H2O2 is not stable and the oxidizing capacity is
weak at low concentration, while at high concentration H2O2 is
dangerous and hard to obtain.
Another environmentally friendly oxidant is molecular oxygen,
with the advantages of safe, cheap, faster kinetics, higher yield,
higher active oxygen content, better reproducibility,[1,16-24] and so
on. The oxygen–aldehyde system with heterogeneous catalysis
has been extensively studied since 1990 by Kaneda et al.,[17] with
the oxidative cleavage of alkenes into carbonyl compounds on
RuO2–CH3CHO–O2. Zhou and co-workers[25] also reported that
cyclohexanone can be converted to the corresponding ester with
a yield of 71% over iron(III) meso-tetraphenylporphyrin chloride,
but the procedures for preparing the catalyst were complicated.
Experimental
Materials and Instrumentation
Tin(IV) chloride pentahydrate, iron(III) nitratenonahydrate, anhy-
drous sodium carbonate, 1,2-dichloroethane, benzaldehyde, chlo-
roform, cyclohexanone, cyclopentanone, phenylmethylketone,
butanone, methylisobutylketone and 4-methylcyclohexanone
(all of AR grade) were used as received without further purification.
A GC-9800 gas chromatograph equipped with a 30 m × 0.53 mm
SE-54 column was used to monitor and analyze the reaction
process. X-ray diffraction (XRD) patterns were obtained using a
Bruker AXS D8-Advance with monochromated high-intensity
Cu Kα radiation (λ = 0.15418). The scanning was performed from
10° to 80° at a rate of 12° minÀ1. Scanning electron microscopy
(SEM) images were obtained using a JSM1500F microscope. The
samples were treated by spraying with gold before observation.
*
Correspondence to: Yadong Zhang and Zhengyong Liang, School of
Chemical Engineering and Energy, Zhengzhou University, Science Road No.
100, Hi-Tech District, Zhengzhou 450001, Henan Province, China. E-mail:
zzuzhangyadong@126.com
School of Chemical Engineering Energy, Zhengzhou University, Science Road No.
100, Hi-Tech District, Zhengzhou 450001, Henan Province, China
Appl. Organometal. Chem. 2015, 29, 450–455
Copyright © 2015 John Wiley & Sons, Ltd.

Baeyer–Villiger oxidation of cyclohexanone
Catalyst Preparation
A mixed solution of SnCl4Á5H2O (0.03 mol) and Fe(NO3)3Á9H2O
(0.03mol) was added slowly into aqueous sodium carbonate (2M)
and sodium hydroxide (1 M) with vigorous stirring at 333 K. Then
the precipitation solution was stirred for another 2 h after the
dripping operation. Right after stirring the crystals were aged for
40 h at 333 K. Next, the precipitates were filtered and washed exten-
sively with deionized water to neutral. Then the brick-red precipi-
tates were dried at 373K in an air oven for 24 h, ground finely
and subsequently calcined at 1123 K for 5 h at a heating rate of
7 K minÀ1 in a muffle furnace. After the calcination, the mixed
oxides were cooled to room temperature in a vacuum desiccator
and thoroughly ground. Finally, the mixed oxides were treated
using ultrasound for 2 h. The resultant mixed oxides were desig-
nated as Fe-Sn-x-T1-t1 (x: molar ratio of Fe to Sn; T1: calcination
temperature; t1: calcination time).
Figure 1. (A) XRD patterns of (a) Fe2O3, (b) fresh catalyst and (c) SnO2.
(B) XRD patterns of (a) catalyst after using five times and (b) fresh catalyst.
Catalytic Experiments
The B-V oxidation reactions were carried out at 50 °C in a four-
necked flask containing 5 mmol of cyclohexanone, 15 mmol of
benzaldehyde and 20 ml of 1,2-dichloroethane. An amount of
90 mg of catalyst was added into the catalytic system. Dioxygen
was bubbled into the solution through a purpose-made glass tube
throughout the process. The reaction mixture was stirred for 4 h,
and then the catalysts were removed by filtration. The product
was determined using GC (GC-9800, 30 m × 0.32 mm SE-54 capillary
column) internal standard method, using toluene as the internal
standard, programmed heating and a flame ionization detector.
The temperatures of gasify room, column and detector were 260,
90 and 230 °C, respectively.
Results and Discussion
Characterization of Catalyst
The catalysts were analyzed using optical microscopy, SEM and XRD
methods. The diffraction patterns were identified by comparing
with the Joint Committee of Power Diffraction Standards (JCPP)
database.
XRD patterns of Fe2O3, SnO2 and the fresh catalyst are shown in
Fig. 1. Several typical peaks (2θ = 26.6°, 33.9°, 37.9°) of Fe–Sn–O
mixed oxides conform with the peaks of SnO2 in JCPP (PDF no.
71–0652). Another two typical peaks (2θ = 24.2°, 33.2°) correspond
to the peaks of Fe2O3 in JCPP (PDF no. 85–0987). Collectively, these
results suggest that the mixed oxides are composed of SnO2 and
Fe2O3. Furthermore, the typical peaks at 2θ = 26.6° and 33.9° are
assigned to the 110 and 101 planes of tetragonal SnO2.[27]
According to the Scherrer equation,[28,29] L = Kλ/β cos θ (K = 0.89,
λ = 0.15418 nm), the size of the nanocrystallites ranges from 15.1
to 51.1nm. And the mean size (L) of nanocrystallites is 29.3 nm.
The SEM images of the fresh catalyst (Fig. 2(a)) and the recycled
catalyst after five cycles (Fig. 2(b)) show that the catalysts have a
granular structure. And after five cycles, the main granular morphol-
ogy remains unchanged.
Figure 2. SEM images: (a) sample of fresh catalyst; (b) sample of catalyst
after using five times.
By comparison, without the presence of any catalyst, the cyclohex-
anone conversion and ε-caprolactone yield are only 79.0 and
74.7%, respectively (entry 12). Also, the yield obtained using
Fe2O3 is higher than that using SnO2, a possible reason being that
the valence state of the metal has an effect on the catalytic results.
When mixing different metal ions into the process of catalyst
preparation, the Fe–Sn–O mixed oxides result in a higher yield
of ε-caprolactone than other different mixed oxides (entries 2, 8,
9, 11). Thus, Fe-Sn-1:1-850-5 is a suitable catalyst.
Catalytic Activities of Fe–Sn–O Mixed Oxides
Experiments were conducted to compare the activity of Fe–Sn–O to
those of other catalysts prepared using the same method. As evi-
dent from Table 1, Fe-Sn-1:1-850-5 exhibits high activity (conver-
sion of 99.9%) and excellent selectivity (yield of 98.8%) (entry 2).
Appl. Organometal. Chem. 2015, 29, 450–455
Copyright © 2015 John Wiley & Sons, Ltd.
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Y. Ma et al.
Table 1. B-V oxidation of cyclohexanone catalyzed by heterogeneous
Table 3, cyclohexanone conversion of 94.9% and ε-caprolactone
yield of 93.4% (entry 2) are obtained. Further, the effects of various
factors on the reaction were investigated using single-factor tests.
catalystsa
Effects of solvent
Several organic solvents were used to analyze the influence of the
solvent. Results in Table 4 show that 1,2-dichloroethane gives the
best performance (entry 3) with the yield of ε-caprolactone being
95.3%, followed by acetonitrile (entry 2). The yields are only 13.4,
14.9 and 70.3% with 1,4-dioxane (entry 1), n-butyl alcohol (entry
5) and dichloromethane (entry 4), respectively. It is speculated
that the formation of hydrogen bonds between the oxygen atom
of 1,4-dioxane and the hydrogen atom of benzoic acid that is pro-
duced through the oxidation of benzaldehyde influences the first
step of the formation of protonated ligand of cyclohexanone. The
boiling point of dichloromethane is only 39.9°C, which cannot
reach the desired temperature required for the activation of mole-
cules. And when n-butyl alcohol is used as solvent, GC analysis
shows many peaks of by-products. It is possibly that the n-butyl
alcohol is oxidized by the oxygen primarily, and then oxidations
of the cyclohexanone cannot proceed without solvent. So the best
solvent is 1,2-dichloroethane.
Entry
Catalyst
Conversion (%)b
Yield (%)b
1
Fe-Sn-1:1-600-5
Fe-Sn-1:1-850-5
Fe-Sn-1:1-900-5
Fe-Sn-1:2-850-5
Fe-Sn-1:3-850-5
Fe-Sn-2:1-850-5
Fe2O3
93.5
99.9
94.5
95.3
94.5
96.7
97.3
91.2
90.0
89.8
67.8
79.0
91.0
98.8
86.7
90.3
91.2
89.7
89.9
90.8
87.6
86.8
41.3
74.7
2
3
4
5
6
7
8
Fe-Mg-1:1-850-5
Sn-Mg-1:1-850-5
SnO2
9
10
11
12
Al-Mg-1:1-850-5
Blank
aReaction conditions: cyclohexanone (5 mmol), benzaldehyde (3 eq.),
catalyst (90 mg), 1,2-dichloroethane (20 ml), O2 (20 ml minÀ1, 25 °C,
0.1 MPa).
bConversion and yield determined by GC.
Effects of solvent volume
To investigate the effect of the solvent volume, several experiments
were conducted with different volumes of 1,2-dichloroethane. As
evident from Table 5, the yield increases firstly and then reaches
an approximate constant with an increase of solvent volume
(entries 1–4). These results might be caused by the fluctuation of
the oxygen flow rate. In the reaction process, the benzaldehyde is
oxidized to benzoic acid. The benzoic acid, with a high melting
point of 122.13 °C, is easily crystallized in a small amount of
solvent. The oxygen vent might be plugged by the precipitate,
Table 2 summarizes the results of B-V oxidation of various ke-
tones over Fe-Sn-1:1-850-5. The catalyst shows excellent activity
in the oxidation of cyclic ketones, with yields of 98.8, 97.2 and
99.3% (entries 1–3). But the catalyst shows poorer performances
in the oxidation of aliphatic ketones, resulting in yilds of only
38.5 and 29.3% (entries 4, 5). This indicates that the size, shape
and the electron cloud distribution have a significant impact on lac-
tone yield. A trace of phenylmethylketone is obtained. It is possible
that the conjugation effect between the benzene ring and the car-
bonyl makes the structure stable and not easy to attack.
Table 3. Results of scale-up experimentsa
Entry
Catalyst
Conversion (%)b
Yield (%)b
Scale-up Experiments
1
2
3
Fe-Sn-1:1-850-5
Fe-Sn-1:1-850-5
Fe-Sn-1:1-850-5
94.7
94.9
94.6
93.4
93.4
93.3
Scale-up experiments were conducted in a 100ml glass flask. In a
typical reaction, 20mmol of cyclohexanone and benzaldehyde
(3eq.) were dissolved into a mixture of 40 ml of 1,2-dichloroethane
and 140 mg of catalyst was added. Afterwards dioxygen was
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
catalyst (140 mg), 1,2-dichloroethane (40 ml), O2 (30 ml minÀ1, 25 °C,
0.1 MPa), T2 = 55 °C, 5 h.
bConversion and yield determined by GC.
bubbled into the stirred solution at a steady rate of 30 ml minÀ1
.
The mixture was heated to 55 °C and stirred for 5 h. As evident from
Table 2. B-V oxidation of various ketones over Fe-Sn-1:1-850-5a
Table 4. B-V oxidation of cyclohexanone in various solventsa
Entry
R
R′
Conversion (%)b Yield (%)b
Entry
Solvent
Conversion (%)b
Yield (%)b
1
2
3
4
5
6
(CH2)2
(CH2)2
(CH2)3
(CH2)2
99.8
97.2
99.8
44.8
32.1
11.3
98.8
97.2
99.3
38.5
29.8
7.6
1
2
3
4
5
1,4-Dioxane
15.0
85.6
95.6
80.1
15.1
13.4
84.3
95.3
70.3
14.9
Acetonitrile
(CH2)2(CH)CH3 (CH2)2
1,2-Dichloroethane
Dichloromethanec
n-Butyl alcohol
(CH3)
(CH2)2CH(CH3)2
(CH2)CH3
(CH3)
CH3(CH2)
(CH)5C
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
catalyst (140 mg), O2 (30 ml minÀ1, 25 °C, 0.1 MPa), solvent (40 ml).
bConversion and yield determined by GC.
cT2 = 39.9 °C.
aReaction conditions: ketone (5 mmol), benzaldehyde (3 eq.), catalyst
(90 mg), 1,2-dichloroethane (20 ml), O2 (20 ml minÀ1, 25 °C, 0.1 MPa).
bConversion and yield determined by GC.
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Baeyer–Villiger oxidation of cyclohexanone
Table 5. B-V oxidation of cyclohexanone using various volumes of
Table 7. B-V oxidation of cyclohexanone using various rates of
solventa
dioxygena
Entry
Solvent (ml)
Conversion (%)b
Yield (%)b
Entry
Dioxygen rate (ml minÀ1
)
Conversion (%)b
Yield (%)b
1
2
3
4
5
6
0
20
25
30
35
40
Trace
89.6
94.7
95.7
93.4
92.3
Trace
86.3
94.3
95.6
93.0
92.0
1
2
3
4
5
15
20
25
30
35
75.7
89.9
96.7
96.5
96.6
75.4
89.5
96.3
96.4
96.4
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
O2 (25 °C, 0.1 MPa), 1,2-dichloroethane (30 ml), catalyst (120 mg),
T2 = 55 °C, 5 h.
bConversion and yield determined by GC.
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
catalyst (140 mg), O2 (30 ml minÀ1, 25 °C, 0.1 MPa), 1,2-dichloroethane,
T2 = 55 °C, 5 h.
bConversion and yield determined by GC.
Effects of temperature and reaction time
and then the yield decreases. Table 5 shows that the yield reaches a
maximization of 95.6% (entry 4) with a solvent volume of 30 ml.
The relationship between the temperature and the ε-caprolactone
yield was investigated using a series of B-V oxidation reactions,
which were carried out in 1,2-dichloroethane solvent with reaction
temperature (T2) varied from 45 to 65 °C, while the reaction time
(t2) ranged from 1 h to 5 h. The results are shown in Fig. 3. It is
obvious that initially the yield increases rapidly with reaction
time. However, the yield does not apparently increase after 4 h.
Furthermore, Fig. 3 also shows that the yield increases firstly as
T2 increases from 45 to 55 °C. The highest yield of 95.9% is
obtained at 55 °C for a reaction time of 4 h. However, as T2
increases from 55 °C, the yield tends to decrease. It is possible
that the solubility of oxygen in the solvent decreases as the
reaction temperature increases, consistent with Henry’s law.[30]
Therefore, the appropriate reaction time and temperature are
4 h and 55 °C, respectively.
Effects of catalyst dosage
Table 6 summarizes the effect of catalyst dosage on yield. It is clear
that the yield increases as the catalyst dosage increases from 80 to
120 mg (entries 1–4), reaching a maximum of 95.9%. Then the yield
remains about the same as the catalyst dosage increases further
(entries 4–6). This is because a certain amount of substrate requires
a proper amount of catalyst. Initially the contact between the reac-
tant molecules and the active centers of the catalyst is insufficient.
With an increase of the catalyst dosage, the amount of the active
centers increases. And the proper amounts of the active centers
are obtained with 120 mg of catalyst. Accordingly, the optimum
catalyst dosage is 120 mg.
Effects of dioxygen rate
Effects of molar ratio of benzaldehyde to cyclohexanone
The oxygen flow was adjusted from 15 to 35 mlminÀ1 to investi-
gate the effect of the oxygen flow rate. The results in Table 7
show that the conversion increases from 75.7% (entry 1) to
96.7% (entry 3) as the oxygen flow increases from 15 to
25 ml minÀ1. Then the conversion displays little variation as the
oxygen flow increases continually from 25 ml minÀ1 (entries 3–5).
The yield of ε-caprolactone reaches a maximum of 96.3% (entry 3).
To investigate the effect of the benzaldehyde in the reaction
system, several experiments were carried out with the molar ratio
of benzaldehyde to cyclohexanone ranging from 0:1 to 5:1. As
shown in Fig. 4, it is obvious that the ε-caprolactone yield increases
initially with the molar ratio and reaches a maximum yield of 96.3%
at 3:1. When the molar ratio increases from 3:1, the yield falls
slightly. It is evident that the appropriate molar ratio of benzalde-
hyde to cyclohexanone is 3:1.
Therefore, the optimum dioxygen rate is 25 ml minÀ1
.
Table 6. B-V oxidation of cyclohexanone using various catalyst
dosagesa
Entry
Catalyst dosage (g)
Conversion (%)b
Yield (%)b
1
2
3
4
5
6
80
100
110
120
130
140
85.6
90.1
94.7
96.0
95.9
95.9
85.4
89.8
94.3
95.9
95.6
95.7
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
O2 (30 ml minÀ1, 25 °C, 0.1 MPa), 1,2-dichloroethane (30 ml),
T2 = 55 °C, 5 h.
bConversion and yield determined by GC.
Figure 3. Effect of temperature on B-V oxidation of cyclohexanone.
Appl. Organometal. Chem. 2015, 29, 450–455
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Y. Ma et al.
Table 9. Results of B-V oxidation over recycled catalysta
Run
Conversion (%)b
Yield (%)b
1
2
3
4
5
96.6
95.9
94.6
94.7
93.5
96.5
95.3
94.1
94.0
93.4
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
catalyst (120 mg), T2 = 55 °C, 4 h, O2 (25 ml minÀ1, 25 °C, 0.1 MPa),
1,2-dichloroethane (30 ml).
bConversion and yield determined by GC.
Figure 4. Effect of molar ratio of benzaldehyde to cyclohexanone on B-V
oxidation of cyclohexanone.
Experiments Using Optimum Reaction Conditions
Several experiments were performed using the optimum condi-
tions. As evident from Table 8, a conversion of 96.7% and a yield
of 96.5% are obtained (entry 1). The similarly of results for the sev-
eral experiments indicated that the catalyst features a good repeat-
ability. Additionally, owing to the scale-up effect, the yield of the
scale-up experiment was lower than the yield of 98.8% of the
small-scale experiment. The temperature distribution, residence
time distribution and concentration distribution of a 100 ml glass
flask are different from those of a 50 ml glass flask. Also, the differ-
ence among the various experimental results data for the optimum
reaction conditions is within experimental errors.[31]
Scheme 1. Mechanism of B-V oxidation of cyclohexanone and benzaldehyde.
unchanged. So the results indicate that the catalysts are not
damaged in the reaction process.
B-V Oxidation with Recycled Catalyst
To investigate the catalytic activity of regenerated catalysts, we
removed the catalysts by filtration, followed by washing with 1,2-
dichloroethane and calcining at 573 K for 3 h, and then ultrasonic
treatment. Table 9 summarizes the results of B-V oxidation over
regenerated catalysts. It can be clearly seen that there is little loss
in catalytic activity of the regenerated catalysts. A conversion of
96.7% and a yield of 96.5% are obtained using the fresh catalyst
(entry 1). After four cycles, a yield of 94.0% is obtained (entry 4),
and a yield of 93.4% after five cycles (entry 5). Moreover, as the
XRD patterns show in Fig. 1(B), the typical peaks (2θ = 26.6°, 33.9°)
of the fresh catalyst and the regenerated catalyst are identical.
And from the SEM images of catalysts before and after use
(five times), the morphology of the catalysts basically remains
Possible Mechanism
Scheme. 1 depicts a plausible mechanism of the B-V oxidation of
cyclohexanone in the oxygen–benzaldehyde system. In the first
step, molecular oxygen is transferred through the catalysts to
oxidize the benzaldehyde into peroxybenzoic acid. In the second
step, the cyclohexanone adsorbed at an acid site of the catalyst is
attacked by PhCOOOÀ, and then a Criegee adduct is obtained after
the nucleophilic addition reaction. Finally, ε-caprolactone is formed
after the rearrangement of the Criegee adduct; simultaneously
benzoic acid is produced.
Conclusions
Table 8. Results obtained using optimum reaction conditionsa
In summary, novel Fe-Sn-1:1-850-5 was facilely prepared using
inexpensive materials. The catalysts showed high catalytic activity
for the B-V oxidation of cyclohexanone in an oxygen–benzaldehyde
system. In the small-scale experiments (5 mmol of cyclohexanone),
high catalytic activity (conversion of 99.9%) and selectivity (yield
of 98.8%) were obtained; in the scale-up tests (20 mmol of
cyclohexanone), the conversion and the yield were 96.7 and
96.5%, respectively. The effects of factors were investigated
through single-factor experiments, and the optimum reaction
conditions were found to be as follows: molar ratio of benzalde-
hyde to cyclohexanone, 3:1 (based on 20 mmol of cyclohexanone);
Entry
Catalyst
Conversion (%)b
Yield (%)b
1
2
3
4
Fe-Sn-1:1-850-5
Fe-Sn-1:1-850-5
Fe-Sn-1:1-850-5
Fe-Sn-1:1-850-5
96.6
96.5
96.7
96.6
96.5
96.4
96.5
96.4
aReaction conditions: cyclohexanone (20 mmol), benzaldehyde (3 eq.),
catalyst (120 mg), O2 (25 ml minÀ1
25 °C, 0.1 MPa), 1,2-
dichloroethane (30 ml), T2 = 55 °C, 4 h.
bConversion and yield determined by GC.
,
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Copyright © 2015 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2015, 29, 450–455

Baeyer–Villiger oxidation of cyclohexanone
dosage of Fe-Sn-1:1-850-5, 120 mg; oxygen flow, 25 ml minÀ1
volume of 1,2-dichloroethane, 30 ml; reaction time, 4 h; reaction
temperature, 55°C. From analysis of catalysts using XRD and SEM,
it was concluded that the original pattern of the catalysts was basi-
cally unchanged. And the catalysts can be reused five times with
only 3.1% loss of the yield, which decreased from 96.5 to 93.3%.
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Acknowledgments
We are grateful for the financial support of the Outstanding Person
Foundation of Henan (2010HASTIT037).
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