Heterogeneous Beckmann rearrangements catalyzed by a sulfonated imidazolium salt of phosphotungstate

Article abstract of DOI:10.1007/s10562-012-0939-5

The heteropolyanion-based ionic liquid (IL) material [MIMPS] ₃PW₁₂O₄₀, propane sulfoacid-functionalized imidazolium salt of phosphotungstate, was used as a solid catalyst for liquid-phase Beckmann rearrangements of ketoximes in the presence of zinc chloride. The resultant liquid-solid biphasic rearrangement reaction of cyclohexanone oxime shows a high yield 83 % with good recyclability. The testing of control catalysts, reaction conditions, oxime substrates, and recycling property were carried out and the results are discussed. Graphical Abstract: The heteropolyanion-based ionic liquid (IL) material [MIMPS]₃PW ₁₂O₄₀, propane sulfoacid-functionalized imidazolium salt of phosphotungstate, was used as a solid catalyst for liquid-phase Beckmann rearrangements of ketoximes in the presence of zinc chloride. The resultant liquid-solid biphasic rearrangement reaction of cyclohexanone oxime shows a high yield 83% with good recyclability. The testing of control catalysts, reaction conditions, oxime substrates, and recycling property were carried out, and the results are discussed.[Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-012-0939-5

Catal Lett (2013) 143:193–199
DOI 10.1007/s10562-012-0939-5
Heterogeneous Beckmann Rearrangements Catalyzed
by a Sulfonated Imidazolium Salt of Phosphotungstate
Xuan Zhang
•
Dan Mao
•
Yan Leng
•
Yu Zhou Jun Wang
•
Received: 1 September 2012 / Accepted: 8 November 2012 / Published online: 27 November 2012
Ó Springer Science+Business Media New York 2012
Abstract The heteropolyanion-based ionic liquid (IL)
material [MIMPS] PW O , propane sulfoacid-function-
conducted in either vapour or liquid phase [3]. For a vapour
phase reaction, solid acid catalysts including boric acid, silica–
alumina and zeolite demand a high reaction temperature to
exhibit good activities, which has drawbacks of quick deacti-
vation and highly energy-consuming [4]. Therefore, a low-
temperature liquid-phase rearrangement has attracted much
research interest. Oleum has been used as the catalyst/medium
for rearrangement of cyclohexanone oxime, giving a high yield
of e-caprolactam, but the system shows disadvantages of heavy
corrosion and a large amount of by-product ammonium sul-
phate [5]. To overcome these problems, great efforts have been
made, including the use of acetonitrile [6, 7], ionic liquids (ILs)
[8, 9] and critical water [10, 11] as effective solvents.
3
12 40
alized imidazolium salt of phosphotungstate, was used as a
solid catalyst for liquid-phase Beckmann rearrangements
of ketoximes in the presence of zinc chloride. The resultant
liquid–solid biphasic rearrangement reaction of cyclohex-
anone oxime shows a high yield 83 % with good recycla-
bility. The testing of control catalysts, reaction conditions,
oxime substrates, and recycling property were carried out
and the results are discussed.
Keywords Ionic liquid Á Beckmann rearrangement Á
Cyclohexanone oxime Á Caprolactam Á Phosphotungstate
Ionic liquids are well-known solvents/catalysts due to
structural versatility, high thermal stability, alterable solu-
bility, and negligible volatility [12–14]. Various Lewis
acidic ILs, such as of AlCl , TiCl , SnCl , BF , PCl , and
1
Introduction
3
4
4
3
5
Beckmann rearrangements are a class of very important organic
reactions that convert oximes into amides [1]. Rearrangement of
cyclohexanone oxime has been applied in petrochemical
industry to synthesize e-caprolactam, a precursor of nylon-6 [2].
Various catalysts are used for Beckmann rearrangements
POCl , have used as catalysts for Beckmann reaction [9, 15].
3
Also, Brønsted acidic IL catalysts are employed for this
reaction. For example, Guo et al. [16] used caprolactam-
based Brønsted acidic ILs as solvents/catalysts to synthesize
e-caprolactam without reporting catalyst recycling proper-
ties. Liu et al. [17] developed an active recyclable sulfoacid-
tethered di-imidazolium IL catalyst for converting aromatic
oximes in the presence of zinc chloride; nevertheless, the
catalyst was inactive for the substrate of acetoxime. Turgis
et al. [5] prepared a reusable IL with sulfonic acid-func-
tionalized cation and hydrogen sulfate anion, and revealed
that the Brønsted acidity of sulfoacid groups in cation was
responsible for Beckmann reaction, but the good activity
could be observed only when the IL was used in an excess
amount with respect to oxime.
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-012-0939-5) contains supplementary
material, which is available to authorized users.
X. Zhang Á D. Mao Á Y. Zhou Á J. Wang (&)
State Key Laboratory of Materials-oriented Chemical
Engineering, College of Chemistry and Chemical Engineering,
Nanjing University of Technology, Nanjing 210009,
People’s Republic of China
e-mail: junwang@njut.edu.cn
Heteropolyacids (HPAs) are widely applied catalysts
for organic transformations, but seldom used for Beck-
mann rearrangement [18]. The few examples include the
Y. Leng
School of Chemical and Material Engineering, Jiangnan
University, Wuxi 214122, People’s Republic of China
123

1
94
X. Zhang et al.
SiMCM41-supported phosphotungstic acid catalyst for the
vapour phase synthesis of e-caprolactam [19] and the HPA
cesium salt catalyst for liquid-phase rearrangement of aromatic
oximes [20]. Noticeably, organic IL-cation salts of HPAs
usually have high melting points due to the large volume and
high valence of HPA-anions [21, 22], and these HPA–IL ionic
compounds are novel catalytic materials [23]. Recently, we
have prepared a series HPA–IL catalysts for organic reactions
with a magnetic stirrer and a condenser. Then, the reaction
was controlled to proceed for 1–6 h at 90 °C. At the end of
the reaction, the resulting mixture was cooled and the liquid
phase was decanted for analysis. When using MeCN, DMF,
1,4-dioxane, and toluene as the solvents, respectively, the
systems were heterogeneous throughout the reaction pro-
cesses. However, the solvent ethanol caused a homogeneous
reaction at the working temperature, and after reaction with
the reaction mixture cooled down to room temperature the
catalyst deposited. Quantitative analyses for the reacted
solution the solid catalyst removed were conducted with
Shimadzu GC-2014 equipped with a FID detector and a
capillary column (SE-30; 50 m 9 0.25 mm 9 0.3 lm).
Every amide product from the rearrangement of an oxime
substrate was confirmed in the gas chromatogram by the
corresponding pure amide compound. For the Beckmann
rearrangement of cyclohexanone oxime, only cyclohexa-
none derived from the deoximation of cyclohexanone oxime
was detected as the by-product besides the major rearrange-
ment product e-caprolactam. The conversion of cyclohexa-
none oxime (Conv. %) and selectivity for e-caprolactam
[24–30]. Typically, we synthesized and characterized a
IL-cation phosphotungstate [MIMPS] PW O : [3-(1-methyl
3 12 40
imidazolium-3-yl)propane-1-sulfonate] PW O [24]. Con-
3 12 40
sidering the Brønsted acidity, solid nature, and insolubility of
this organic HPA salt in this study, we try it as the catalyst for
Beckmann rearrangement (Scheme 1). Various control cata-
lysts, reaction conditions, and substrates are investigated.
OH
O
N
3-
N
N
SO H 3PW12O
3
40
NH
[
MIMPS] PW12O40
3
°
ZnCl , MeCN, 90 C, 1 h
2
(Sel. %) were calculated as Conv. % = (mol e-caprolac-
tam ? mol cyclohexanone) / mol initial cyclohexanone
oxime. Selectivity % = mol e-caprolactam / (mol e-capro-
lactam ? mol cyclohexanone). For Beckmann rearrange-
ments of other oxime substrates, the GC yields for amide
products were obtained by adding the internal standard
cyclohexane.
2
Experimental
2
.1 Preparation of [MIMPS] PW O and Control
3 12 40
Catalysts
Preparation and characterization for phosphotungstate salts
of sulfonated IL-cations have been reported in our previous
work [24]. For preparing [MIMPS] PW O , methylimid-
3
12 40
3 Results and Discussion
azole (0.11 mol) and 1,3-propane sulfone (0.1 mol) were
dissolved in anhydrous toluene (25 mL), with a stirring at
3.1 Beckmann Rearrangement of Cyclohexanone
Oxime over Various Heteropolyanion-based ILs
Catalysts
5
0 °C for 24 h under nitrogen atmosphere. The resulting
white precipitate (MIMPS) was filtered and washed with
diethyl ether and then dried in vacuum. Then, MIMPS
(
(
0.06 mol) was added to an aqueous solution of H PW O
3
Cyclohexanone oxime is used as a probe molecule to
examine the feasibility of the heteropolyanion-based ILs
catalysts for Beckmann rearrangements in the presence of
12 40
0.02 mol), and the mixture was stirred at room temperature
for 24 h. Finally, water was removed in vacuum to give
MIMPS] PW O as a solid. [3-(1-Methylimidazolium-3-yl)
[
ZnCl . The results are summarized in Table 1. Without any
2
3
12 40
propane-1-sulfonate] PW O
3
and [MIMPS] HPW O
12 40
catalyst, the reaction gave no product (entry one), while
12 40
2
were prepared with controlled molar ratios of cation and anion.
Other control samples of [3-butyl-1-methylimidazolium]3
PW O , [(3-sulfonic acid)propylpyridinium] PW O , and
ZnCl alone did not show any catalytic activity (entry two).
2
The catalyst [MIMPS] PW O gave a low conversion of
12 40
3
12
40
3
12 40
cyclohexanone oxime 22 % in the absence of ZnCl (entry
2
[
(3-sulfonic acid)propyltriethylammonium] PW O were also
3
three). The classical pure HPA catalyst H PW O in the
12 40
12 40
3
prepared accordingly, which are designated as [BMIM] PW
3
presence of ZnCl gave a conversion 89 % and selectivity
2
12
O , [PyPS] PW O ,and [TEAPS] PW O , respectively.
12 40
83 % (entry four). Interestingly, with both [MIM-
PS] PW O and ZnCl , the system exhibited a full con-
40
3
12 40
3
3
12 40
2
2
.2 Procedures for Beckmann Rearrangement
Reactions
version 100 % with a high selectivity for e-caprolactam
83 % (entry five). Cyclohexanone, derived from deoxi-
mation of cyclohexanone oxime, is the only by-product
Oxime (2 mmol), catalyst (0.2 mmol), ZnCl (0.2–0.6 mmol),
2
detected by GC. The observation that ZnCl acts as a
2
and 5 mL solvent were added into a 25 mL round-bottom flask
cocatalyst is consistent with previous reports [7, 31].
1
23

Heterogeneous Beckmann rearrangements
195
Table 1 Beckmann rearrangement of cyclohexanone oxime over
various HPA–IL catalysts in the presence of ZnCl
1
00
2
9
8
0
0
Entry
Catalyst
Conv./ %
Sel./ %
a
1
Non-catalyst
Trace
Trace
22
–
b
2
ZnCl
2
–
70
c
3
[MIMPS]
3
PW12
O
40
40
45
83
83
83
84
–
6
5
0
0
4
5
6
7
8
9
3
H PW12
O
40
89
[MIMPS]
3
PW12O
100
95
[MIMPS]2.5
H0.5PW12
O
40
40
[MIMPS]
[BMIM]
[PyPS]
[TEAPS]
2
HPW12
PW12
PW12
PW12
O
40
86
Conversion of cyclohexanone oxime
Selectivity forε- caprolactam
3
2
0
0
3
O
40
Trace
89
3
O
40
74
76
1
0
20
30
40
50
60
1
0
3
O
40
90
Reaction time/min
Reaction conditions: cyclohexanone oxime 2 mmol, catalyst
0
a
.2 mmol, ZnCl
2
0.6 mmol, MeCN (solvent) 5 mL, 90 °C, 1 h
Without [MIMPS] 40 and ZnCl
, without [MIMPS] PW12
With [MIMPS] 40, without ZnCl
Fig. 1 Effect of reaction time on Beckmann rearrangement of
cyclohexanone oxime
3
PW12
O
2
b
c
With ZnCl
2
3
O
40
3
PW12O
2
100
9
8
0
0
When the loading of the sulfoacid-tethered cation
MIMPS in phosphotungstate salts was reduced, the
resultant samples, [MIMPS]2.5H0.5PW O and [MIMPS]2
70
12
40
HPW O , showed gradually lower conversions down to
12 40
60
8
6 % (entries six and seven). One may thus draw that the
acidity of the sulfonic acid groups in the cation moiety must
have acted as the active centers for the rearrangement. This is
further confirmed by the data in entry eight that the non-
sulfonic acid counterpart, [BMIM] PW O , was inactive.
50
40
Conversion of cyclohexanone oxime
Selectivity forε-caprolactam
30
3
12 40
Moreover, pyridinium- and ammonium-based analogues,
PyPS] PW O and [TEAPS] PW O (entries nine and
5
0
60
70
80
90
o
100
110
[
3
12 40
3
12 40
Temperature/ C
ten), presented lower conversion and selectivity than the
imidazolium-based [MIMPS] HPW O . The higher
2
12 40
Fig. 2 Effect of reaction temperature on Beckmann rearrangement of
cyclohexanone oxime
activity of the latter may stem from the additional acidity of
2
-position hydrogen of the imidazole ring [32].
more created basic e-caprolactam product should at least
contaminate at part of the strong acidic sites and thus
remarkably, hindered the side reaction of deoximation.
Effect of reaction temperature is shown in Fig. 2. As
reaction temperature rose from 50 to 90 °C, both conver-
sion and selectivity increased significantly. A full conver-
sion was got at 90 °C. At the higher temperature 110 °C,
the conversion 100 % could be obtained within a shorter
time 45 min. Nevertheless, a lower selectivity for e-cap-
rolactam was observed, mostly due to the formation of
condensation products from ketone by the deoximation at
such a high temperature [33]. Therefore, 90 °C is selected
as the optimal temperature.
3
.2 Influence of Reaction Conditions
for Rearrangement of Cyclohexanone Oxime
over [MIMPS] PW O
3
12 40
Figure 1 shows the influence of reaction time on conver-
sion and selectivity for Beckmann rearrangement of
cyclohexanone oxime over the HPA–IL catalyst [MIMPS]3
PW O . It can be seen that the conversion increased
1
2 40
quickly at early reaction period, and then reached to 100 %
at 1 h. The selectivity for e-caprolactam showed a same
trend as the conversion, attaining a constant high value
8
3 % after 45 min. At the early reaction stage, the lower
selectivity for e-caprolactam is due to the formation of a
considerable amount of cyclohexanone caused by deoxi-
mation reaction on fresh acidic sites; afterwards, more and
Influence of the amount of cocatalyst ZnCl added in
2
reaction is displayed in Fig. 3. When the reaction pro-
ceeded without ZnCl , very low conversion 22 % and low
2
123

1
96
X. Zhang et al.
selectivity 45 % were detected. With increasing the
one). The fact that MeCN tends to exhibit a better result in
Beckmann rearrangement has been observed by other
researchers [7, 8, 17]. The previous study [7] has revealed
that a polar solvent is more favourable to this reaction. As
an aprotic polar solvent with strong nucleophilicity, MeCN
facilitates the reaction mostly by stabilizing the reaction
intermediates such as N-protonated oxime [39]. On the
other hand, Shiju et al. [20] have found that the solvents
with higher dielectric constants may accelerate the 1,2-H
shift of N-protonated oxime into O-protonated oxime by
reducing the energy barrier of the transition state. This
proposal also explains the much better reaction result in
MeCN solvent with the highest dielectric constant.
amount of ZnCl up to 0.6 mmol, both conversion and
2
selectivity increased, where a full conversion of cyclo-
hexanone oxime was attained. A further increase of ZnCl2
to 1 mmol led to only a slight increase in selectivity by
3
%. Thus, the preferential amount of ZnCl is 0.6 mmol,
2
and in this case, the molar ratio of [MIMPS] PW O to
12 40
3
ZnCl is 1:3.
2
In the previously proposed mechanism for the rear-
rangement of cyclohexanone oxime catalyzed by an acidic
catalyst, the nitrogen of cyclohexanone oxime is first pro-
tonated by the Brønsted acid site of catalyst with the cre-
ation of the nitrilium intermediate [34], then O-protonated
oxime is generated from the 1,2-H-shift route by the proton
transfer from nitrogen to oxygen [35, 36]. On the other
hand, coordination of a Lewis acid to a Brønsted acid has
been revealed to increase significantly the original acidity
of the latter [37]. It is thus suggest that the co-catalytic
However, in Table 2, another aprotic polar solvent DMF
(entry two) gave a low conversion, though it has a very
high dielectric constant. This phenomenon is suggested to
associate with its unnegligible basicity that should some-
what neutralize the acidic catalyst and therefore hinder the
catalytic activity [16, 40]. Moreover, it is understandable
that 1,4-dioxane and toluene presented low conversions
(entries three and four), considering their extremely low
dielectric constants. In addition, toluene actually made the
catalyst inactive, which relates to its nonpolar property,
causing a mass transfer problem in the resulting liquid–
liquid–solid triphasic system. On the other hand, the protic
solvents like ethanol with a moderate dielectric constant is
not a suitable solvent for this reaction, as also reported
previously [39] despite its polar nature. It is true that
ethanol only led to a low activity over the present
[MIMPS] PW O catalyst (entry five). Ethanol has a
function of the Lewis acid ZnCl is to increase the overall
2
acidity of the reaction system catalyzed by the Brønsted
acidic [MIMPS] PW O , promoting the protonation
3
12 40
route with comparatively a high activation energy [38].
Additionally, the previous study [7] conjuncted the form of
a reaction intermediate of seven-ring nitrilium cation from
the chelation of ZnCl with the nitrogen of cyclohexanone
2
oxime, which may also be helpful to understand the
co-catalytic function of ZnCl herein.
2
Table 2 lists the reaction results of Beckmann rear-
rangement of cyclohexanone oxime in various solvents,
plus the polar property and dielectric constant of the sol-
vents. As seen, MeCN was found to be the most suitable
solvent due to the highest conversion and selectivity (entry
3
12 40
weaker nucleophilicity than MeCN, which may be the
major reason for its low conversion.
Table 2 Influence of solvents on Beckmann rearrangement of
100
3 40
cyclohexanone oxime catalyzed by [MIMPS] PW12O
a
Entry Solvent
Polarity
Dielectric
b
constant
Conv./ Sel./
%
%
8
0
0
0
0
1
2
3
MeCN
DMF
1,4-
Aprotic
polar
37.5
36.7
2.2
100
83
6
4
2
Aprotic
polar
7
71
50
Aprotic
polar
17
Dioxane
4
5
Toluene
EtOH
Nonpolar
2.0
0
–
Conversion of cyclohexanone oxime
Selactivity for -caprolactam
Protic
polar
24.5
10
83
0.0
0.2
0.4
0.6
0.8
1.0
Cyclohexanone oxime 2 mmol, catalyst 0.2 mmol, ZnCl
solvent 5 mL, 90 °C, 1 h
2
0.6 mmol,
Dosage of ZnCl /mmol
2
a
Referring to Philip G. Jessop (2011) Green Chem 13:1391
b
Fig. 3 Effect of amount of cocatalyst ZnCl
rangement of cyclohexanone oxime
2
on Beckmann rear-
Referring to Ronchin L, Vavasori A, Bortoluzzi M (2008) Catal
Commun 10:251
1
23

Heterogeneous Beckmann rearrangements
197
3
.3 Recycling of Catalyst [MIMPS] PW O
3
Such an interpretation was also revealed by Du’s work
[40]. Additionally, the contamination of the catalyst
acidic sites by the residue of the basic substrate cyclo-
hexanone oxime cannot be excluded, because of the lar-
12 40
for Beckmann Rearrangement of Cyclohexanone
Oxime
-
1
Since [MIMPS] PW O is a solid heterogeneous catalyst
3 12 40
gely enhanced band at 1,638 cm
for C=N on the
for Beckmann rearrangement of cyclohexanone oxime, it
can be easily recovered from a reacted mixture. However,
recycled catalyst. To improve the recycling stability of
the present catalytic system remains a further work.
ZnCl is partially dissolved in acetonitrile and is totally
2
washed away during a recovery operation. Therefore, cat-
alytic reusability of [MIMPS] PW O was tested with
3.4 Beckmann Rearrangement of Various
Ketoxime Substrates Catalyzed
3
12 40
adding fresh ZnCl in recycling intervals, as shown in
2
Fig. 4. It can be seen that, compared to the fresh catalyst, a
substantial decrease in conversion was observed in the
second and third runs. However, the conversion was stable
in after runs, showing a considerable value above 53 %.
Additionally, whatever the recycling numbers, very steady
selectivity was found.
by [MIMPS] PW12O40–ZnCl
3 2
To explore the scope of Beckmann rearrangement cata-
lyzed by [MIMPS] 40 and ZnCl , various ketoximes
PW12
O
3
2
substrates were examined. As indicated in Table 3, higher
yields 88–98 % were obtained for aromatic ketoximes
(entries 1–4) than the yield 83 % for cyclohexanone oxime
(entry five). Compared to previous results over the catalysts
of caprolactam-based Brønsted acidic IL [16], binucleate-
Figure 5 illustrates the IR results for [MIMPS]3
PW O . Similar to the fresh catalyst, the recycled one
1
2 4
showed four featured bands for Keggin phosphotungstate-
-
1
anion at 1,079, 979, 896, and 806 cm
[24]. For the
SO
ion, [6] and cyanuric chloride [7], the present catalyst
[MIMPS] 40 offers a comparative yield with aro-
3
H functionalized imidazolium IL [17], cyclopropenium
cation moiety MIMPS, the bands at 1,230, 1,172, and
-
21 cm appeared for the sulfonic group, with simulta-
1
6
PW12O
3
-
neous occurrence of 1,617 cm for the vibration of C=C
1
matic ketoximes and a higher yield with alkyl ketoximes,
even under milder conditions. In addition, our catalyst
gave meliorative yields with the inert substrates cyclo-
pentanone oxime (19 %) and acetone oxime (8 %)
(entries six and seven), and increasing the reaction time
up to 6 h resulted in higher yields (74 and 18 %), which
is in contrast to the fact that the early effort could not
convert the two inert substrates [17]. This again evidences
-
1
and 1,638 cm for C=N. The IR comparison suggests a
quite durable structure of [MIMPS] PW O in this
3
12 40
Beckmann reaction. However, the characteristic vibrations
-
1
for the product molecule e-caprolactam (3,412 cm for
-
1
N–H and 1,400 cm
for C–N) also appeared on the
recycled [MIMPS] PW O . It is thus deduced that the
3 12 40
contamination of the active acidic sites by the involved
basic e-caprolactam molecules may account for the
decreases of conversion in the early two recycling runs.
the high catalytic activity of [MIMPS]
Beckmann reactions.
PW12O40 for
3
1
400
Conversion of cyclohexanone oxime
100
Selectivity for ε-caprolactam
b
a
9
8
7
6
5
0
0
0
0
0
3
412
1
617 979 806
638 1079 896
6
21
1
4000
3500
3000
2500
2000
1500
1000
500
0
1
2
3
4
Wavenumbers/cm-1
Recycle times
Fig. 4 Catalytic recycling of [MIMPS]
rearrangement of cyclohexanone oxime
3
PW12O40 for Beckmann
Fig. 5 IR spectra of (a) fresh [MIMPS]
[MIMPS] 40 after five runs
3
PW12O40 and (b) recycled
3
PW12O
123

1
98
X. Zhang et al.
Table 3 Beckmann
rearrangements of various
substrates catalyzed by
a
Entry
1
Oxime substrate
Amide product
Yield /%
OH
N
O
[
3 2
MIMPS] PW12O40–ZnCl
Ph
98
88
88
95
Ph
N
H
Ph
Ph
Ph
OH
O
N
2
3
4
Ph
N
H
OH
N
H
N
O
MeO
MeO
OH
H
N
N
O
O N
O2N
2
OH
O
N
N
5
NH
83
OH
OH
O
b
6
7
NH
19 (74 )
Reaction conditions: Oxime
2
0
mmol, [MIMPS]
.2 mmol, ZnCl 0.6 mmol,
3 40
PW12O
2
O
MeCN 5 ml, 90°C, 1 h
N
b
a
8 (18 )
GC yield
N
H
b
6
h
4
Conclusions
4. Ko Y, Kim MH, Kim SJ, Seo G, Kim MY, Uh YS (2000) Chem
Commun 829
5
. Turgis R, Estager J, Draye M, Ragaini V, Bonrath W, Leveque
JM (2010) ChemSusChem 3:1403
The heteropolyanion-based IL [MIMPS] PW O con-
3 12 40
taining propane sulfoacid-functionalized imidazolium cat-
ion and Keggin phosphotungstate anion is revealed to be
highly efficient catalyst for Beckmann rearrangement with
6. Srivastava VP, Patel R, Yadav G, Yadav LDS (2010) Chem
Commun 46:5808
7
. Furuya Y, Ishihara K, Yamamoto H (2005) J Am Chem Soc
27:11240
. Vilas M, Tojo E (2010) Tetrahedron Lett 51:4125
1
ZnCl as the cocatalyst. Ten mol percentage IL catalyst
2
8
with 30 mol % ZnCl well converts cyclohexanone oxime
2
9. Peng J, Deng Y (2001) Tetrahedron Lett 42:403
10. Boero M, Ikeshoji T, Liew CC, Terakura K, Parrinello M (2004)
J Am Chem Soc 126:6280
or aromatic oximes to corresponding amides within 1 h at
9
0 °C. With a longer reaction time 6 h, the catalyst is even
1
1. Ikushima Y, Hatakeda K, Sato O, Yokoyama T (2000) J Am
Chem Soc 122:1908
12. Song HY, Li Z, Chen J (2012) Catal Lett 142:81
active for the inert substrates cyclopentanone oxime and
acetone oxime. As a solid heterogeneous catalyst, [MIMPS]3
PW O can be easily recovered after reaction, showing a
13. Zhao D, Wu M, Kou Y, Min E (2002) Catal Today 74:157
1
2 40
1
1
1
4. Dupont J, Souza RF, Suarez PAZ (2002) Chem Rev 102:3667
5. Zicmanis A, Katkevica S, Mekss P (2009) Catal Commun 10:614
6. Guo S, Du Z, Zhang S, Li D, Li Z, Deng Y (2006) Green Chem
considerably high activity after five recycling runs of the
rearrangement of cyclohexanone oxime.
8
:296
Acknowledgments The authors thank greatly the National Natural
Science Foundation of China (No. 21136005).
17. Liu X, Xiao L, Wu H, Li Z, Chen J, Xia C (2009) Catal Commun
10:424
1
1
8. Qiao Y, Hou Z (2009) Curr Org Chem 13:1347
9. Maheswari R, Shanthi K, Sivakumar T, Sankarasubbier N (2003)
Appl Catal A 248:291
References
2
2
0. Shiju NR, Williams HM, Brown DR (2009) Appl Catal B 90:451
1. Bourlinos AB, Raman K, Herrera R, Zhang Q, Archer LA,
Giannelis EP (2004) J Am Chem Soc 126:15358
1
2
. Blatt AH (1933) Chem Rev 12:215
. Luedeke VD (1978) In: Mcketta JJ (ed) Encyclopedia of chem-
ical processing and design. Marcel Dekker, New York
. Smith MB, March J (2001) Advanced organic chemistry, 5th edn.
Wiley, New York
22. Ge HQ, Leng Y, Zhou CJ, Wang J (2008) Catal Lett 124:324
23. Chaturvedi D (2011) Curr Org Chem 13:1347
24. Leng Y, Wang J, Zhu D, Ren X, Ge H, Shen L (2009) Angew
Chem Int Ed 48:168
3
1
23

Heterogeneous Beckmann rearrangements
199
2
2
2
2
2
3
3
5. Leng Y, Wang J, Zhu D, Wu Y, Zhao P (2009) J Mol Catal A
13:1
6. Zhang W, Leng Y, Zhu D, Wu Y, Wang J (2009) Catal Commun
1:151
7. Zhang W, Leng Y, Zhao P, Wang J, Zhu D, Huang J (2011)
Green Chem 13:832
8. Leng Y, Wang J, Zhu D, Zhang M, Zhao P, Long ZH, Huang J
32. Dupont J, Spencer J (2004) Angew Chem Int Ed 43:5296
33. Cheng SB, Xu BQ, Wang DQ (1996) Chin J Catal 17:281
34. Hill RK, Conley RT, Chortyk OT (1965) J Am Chem Soc 87:24
35. Ronchin L, Bortoluzzi M, Vavasori A (2008) J Mol Theochem
858:46
36. Nguyen MT, Raspoet G, Vanquickenborne LG (1997) J Am
Chem Soc 119:2552
37. Zhang X, Li J, Wang XH, Cao FH (2009) Energy Fuels 23:4640
38. Ronchin L, Vavasori A, Bortoluzzi M (2008) Catal Commun
10:251
3
1
(2011) Green Chem 13:1636
9. Leng Y, Wang J, Zhu D, Shen L, Zhao P, Zhang M (2011) Chem
Eng J 173:620
0. Zhao P, Leng Y, Zhang M, Wang J, Wu Y, Huang J (2012) Chem
Commun 48:5721
1. Pi HJ, Dong JD, An N, Du W, Deng WP (2009) Tetrahedron
39. Wang XG, Chen CC, Chen X, Mou Y, Cheng S (2005) Appl
Catal A 281:47
40. Du Zh, Li Z, Gu Y, Zhang J, Deng Y (2005) J Mol Catal A
237:80
6
5:7790
123