Research in Chemistry and Environment

Sagar et al. Int. J. Res. Chem. Environ. Vol. 4 Issue 4 (93-100) October 2014
International Journal of
Research in Chemistry and Environment
Available online at: www.ijrce.org
ISSN 2248-9649
Research Paper
Beckmann Rearrangement of Keto-oximes to Amides using Sisal-DCT
under Reflux Condition
Deshpande Anitha S., Chamle Sadhana N., Yadav Manjusha V., *Sagar Ashok D.
School of Chemical Sciences, Swami Ramanand Teerth Marathwada University
Dnyanteerth, Vishnupuri, Nanded-431606, (M.S.), INDIA
(Received 30 June 2014, Accepted 15 July2014)
Abstract: Efficient conversion of ketoximes to amides by conventional Beckmann’s rearrangement reaction is presented
using 2, 4, 6-trichloro-1, 3, 5-triazine (TCT) supported over inexpensive and renewable Sisal under reflux condition. A
variety of ketoximes were converted to corresponding amides into good to excellent yields.
Keywords: Amide, Beckmann’s Rearrangement, Ketoxime, 2, 4, 6-Trichloro-1, 3, 5-triazine, Sisal-DCT.
© 2014 IJRCE. All rights reserved
out at high reaction temperature, strong Bronsted acid
and dehydrating media, leads to the formation of
byproduct and serious corrosion problems [13]. Undesired
sulphate was formed as byproduct when Beckmann
Rearrangement takes place in presence of oleum as
catalyst [14]. Therefore, it is essential to develop new
sulphate free methods for Beckmann rearrangement
under
mild
conditions.
The
representative
catalysts/reagents used for the Beckmann rearrangements
are Propylphosphonic anhydride (T 3P®)[15], Ph3P/ I2 [16],
RuCl3[17], 2, 4, 6-Trichloro-1, 3, 5-triazine(TCT) [18,20],
Sulfamic acid/Zinc chloride[19], Triphosphazene (PNT)[21],
Yb(OTf)3[22], Bis (2-oxo-3-oxazolidinyl)phosphonic
chloride[23] Diethyl chlorophosphate[24], In(OTf)3 [25],
Non-zeolitic Nb-based catalysts[26], [RhCl(cod)]2[27],
Iodine[28], HgCl2[29], Copper(II) acetate [30], p-TSAZNCl2[31], Al-MCM-41 (Molecular sieves)[32], TsCl[33],
Chlorosulfonic acid[34], Chloral[35], Sulfamic acid[36],
Anhydrous oxalic acid[37], 2, 4, 6-Trichloro-1, 3, 5triazine [38], Phosphoratedd compounds (PCl5, POCl3,
P2O5)[39], B2O3[40], 1-Chloro-2,3-diphenylccylopropenium
ion[41], HMPT[42], BF3-OEt2[43], AlCl3[44], Sulphonyl
Chloride[45].
Introduction
The Beckmann rearrangement, named after the
German chemist Ernst Otto Beckmann (1853–1923), is
an acid catalyzed rearrangement of an oxime of aldehyde
or ketone to an amide [1-3]. The reaction is highly stereo
specific. The resulting amides are highly used for the
commercial preparation of polyamides, synthetic fibers,
various natural products and synthetic intermediates for
medicinal compounds [4]. Cyclic oximes yield lactams.
The formation of ε-caprolactum starting from
cyclohexanone through intermediate cyclohexanone
oxime [5] is one of the most important applications of the
Beckmann rearrangement, as ε-caprolactum is the
feedstock in the production of Nylon-6. Another
important application of this reaction involves the
commercial process for the production of Nylon-6 and
Nylon-12. By implementation of different organo
catalysts, there are many catalytic methods in liquid
phase [6], vapour phase, [7 - 11] and in ionic liquids [12] have
been reported. The milder conditions developed were
essentially related to activating the oxime by using acidic
reagents.
Organic chemists continue to explore novel
synthetic methods involving new reagents and catalysts
to carry chemical transformations. One of them is to carry
out reactions on the surface of solids or solid supported
reagents. Some of the catalysts used are toxic, corrosive
and having cost effectiveness on industrial utilization. For
the Beckmann rearrangement, more efficient and less
toxic catalytic methods having functional group tolerance
is highly desirable. During the rearrangement, the
cleavage of C–C bond and formation of C–N bond
occurs. Generally, Beckmann rearrangement was carried
Some of the above catalysts used for Beckmann
rearrangement are corrosive, toxic, costly and rare
availability therefore found less utilization for industrial
purposes. Investigation of more efficient method for the
Beckmann’s rearrangement by using less toxic, low cost
and renewable catalyst is desirable. Recently,
organocatalyst for the Beckmann rearrangement has
mostly attracted the researchers’ attention for its
efficiency in catalytic activity and easy to handle during
the rearrangement. 2, 4, 6-Trichloro-1, 3, 5-triazine
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(TCT), [34] as organocatalyst, was reported to be a highly
efficient catalyst for the Beckmann rearrangement by
Ishihara and his co-workers.
The environmental regulations and process safety continue to drive the industry to develop solid acids to
replace liquid acid processes. In continuation of our research work, we are reporting the conversion of ketoximes to
amides by using Sisal supported 2, 4-Trichloro-1, 3, 5-triazine (Sisal-DCT) in presence of zinc chloride as a co-catalyst
(Scheme I).
Cl
Cl
Sisal
N
OH
N
Cl
N
NaHCO3, 0 30o C
N
Cl
Sisal
- HCl
O
N
N
Cl
Sisal-DCT
(Sisal Triazine ether)
Scheme I: Preparation of catalyst.
Various ketoximes undergo Beckmann rearrangement reaction using Sisal-DCT as a catalyst in presence of zinc
chloride affording corresponding amides. Ketoxime I was refluxed at 60oC with Sisal-DCT (10 Wt. %) in presence of
zinc chloride (2 Wt. %) and acetonitrile (5 mL) which result the corresponding amides II (Scheme II).
OH
N
R1
Sisal-DCT+ ZnCl2
HN
o
CH3CN, Reflux 60 C
R1
R2
O
R2
I
II
R1& R2= Alkyl, Aryl
Scheme II: Transformation of Ketoxime to Amide
Methods and Material: All chemicals were purchased
from Merck, Fluka, Aldrich fine chemicals and used as
they were received. Distilled solvents were used.
heating alcohol was distilled off and cold water (10 mL)
was added to the reaction mixture which were placed for
about 10 min. Oxime was crystallized out slowly which
was recrystallized from boiling alcohol. Colourless
needle like shining crystals were obtained and the purity
of oxime was checked by TLC and melting point.
Measurements: Products were characterized by
comparison of their spectral and physical data with
authentic samples. IR spectra were obtained using a
Shimadzu FT-IR spectrophotometer. Mass spectra were
determined on a Shimadzu GCMS-QP 1000 EX
instrument. 1H NMR spectra were recorded on a Bruker
Avance Dpx-250.
Procedure for the preparation of amides: The mixture
of ketoxime I (2 mmol), Sisal-DCT (10 Wt. %) and zinc
chloride (2 Wt. %) in acetonitrile (10 mL) was refluxed at
60oC. The progress of the reaction was monitored by
TLC. After completion of the reaction, the reaction
mixture was just filtered to remove catalyst and solvent
was evopourated to get crude product. The crude product
was extracted with dichloromethane (2 ×10 mL). The
combined organic layer was washed with water (2 ×10
mL). The organic layer was dried over anhydrous sodium
sulphate, filtered and the solvent was evaporated under
reduced pressure. The crude product II so obtained was
purified by column chromatography over silica gel (ethyl
acetate: pet ether, 9:1, v/v).
General Procedure
Procedure for the preparation of catalyst: Sisal is
extracted with methanol using soxhlet extraction
assembly for 20 hours. Further it was dried and soaked in
acetonitrile. A mixture of 2 mmol of sodium bicarbonate
and 2 mmol of 2, 4, 6- trichloro-1, 3, 5-triazine was
added to the soaked Sisal and constantly stirred for half
an hour at 30oC. Then 5 mL of distilled water was added
and stirring was continued for another 30 minutes on
magnetic stirrer. The solution was decanted. The catalyst
was finally washed with 10 mL of acetone and utilized
for organic transformations.
Results and Discussion
Initially benzophenone oxime (2 mmol) and
Sisal-DCT (10 Wt. %) was refluxed at 60oC in presence
of dichloromethane as a solvent and the reaction was
monitored by TLC. It was observed that the rate of
product formation was initially slow which was increased
by addition of small quantity of zinc chloride (2 Wt. %)
as a co-catalyst. For the optimization of reaction
Procedure for the preparation of oxime of an
aldehyde / ketone: A ketone / aldehyde (0.5 g), hydroxyl
amine hydrochloride (0.5 g), ethanol (0.5mL) and
pyridine (0.5mL) were taken in a 100 mL round bottom
flask and refluxed on water bath for 45-60 min. After
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Sagar et al. Int. J. Res. Chem. Environ. Vol. 4 Issue 4 (93-100) October 2014
found to be a suitable solvent for the Beckmann’s
rearrangement.
conditions, the same reaction was carried out in presence
of different solvents (Table 1) under different
temperatures and concluded that acetonitrile at 60o C was
Table 1
Effect of different solvents for transformation of benzophenone oxime to Benzanilide
S. No.
1
2
3
4
5
Temperature (oC)
50
90
60
60
60
Solvent
Dichloromethane
Water
Ethanol
Acetonitrile
Methanol
Time (hrs.)
6
15
6
3
6
Table 2
Transformations of Various Ketoximes to Amides Using Sisal-DCT /ZnCl2
S. No.
Amide a II
Ketoxime I
OH
H
N
N
Reaction Time(hr.)
Yield b (%)
3
90
3
89
1.5
90
2
90
3
80
3
89
2
85
1
O
OH
H
N
N
2
O
MeO
MeO
OH
H
N
N
3
O
O2N
O2N
OH
H
N
N
4
O
OH
OMe
OMe N
H
N
5
O
OH
H
N
N
6
O
HO
HO
OH
Br
N
Br
H
N
7
O
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OH
H
N
N
8
O
91
2.5
89
3
92
3
85
3
75
3
85
H
N
OH
N
9
3
O
Cl
Cl
NOH
N
O
10
O
NOH
N
11
N
O
OH
N
12
OH
N
13
H
N
O
Reaction conditions:
ketoxime (2mmol), catalyst Sisal-DCT (10 wt %), ZnCl2 (2 Wt %) refluxed at 60oC in presence of acetonitrile,
a
product confirmed from physical and spectral analysis,
Yield b= Maximum yield of the reaction product.
HNMR spectra of Benzanilide
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HNMR spectra of p-Tolylacetamide
IR spectra of Benzanilide
IR spectra of p-Tolylacetamide
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Mass spectra of Benzanilide
Mass spectra of p-Tolylacetamide
For the study of scope and generality, the
reaction was carried by taking various oximes of ketone
(Table 2) in presence of acetonitrile to get corresponding
amides. Further it was observed that, the Beckmann
rearrangement reaction containing electron withdrawing
substituents (entry 3, 7, 9) on the aromatic ring in the
ketoximes, completed relatively faster than that of
ketoximes containing electron donating groups (entry 2,
5, 6, 8, 12). The cyclohexanone oxime was smoothly
converted to ε-caprolactam in excellent yield (entry 10).
Acknowledgement
We are very grateful to UGC, New Delhi for
providing necessary laboratory facilities.
Spectral data of selected compounds:
1. Benzanilide (entry1)
IR: 3342 (– NH –), 1655 (– CONH –)
1
H NMR: 7.13 –7.88 (m, 11H, Ar–H and -NH)
Mass: 198 (M+1, 100%)
Elemental analysis: Calc. for M.F.: C13H11NO (M.W. =
197), C= 79.16%, H=5.62%, O= 8.11%, N=7.10%
Found: C=79.13%, H= 5.60 %, O= 8.10% N=7.09%.
Conclusion
Sisal-DCT catalyst is non-irritating in nature and
could be easily synthesized or reactivated simply by the
reaction of a renewable Sisal biopolymer with 2, 4, 6Trichloro-1, 3, 5-triazine (TCT). It was found to be an
effective catalytic method for the Beckmann
rearrangement. Sisal-DCT and ZnCl2 promotes clean and
efficient rearrangement of variety of ketoximes to
corresponding amides under mild conditions in excellent
yield of the products.
2. N-p-Tolylacetamide (entry 8)
IR: 3272 (– NH –), 1662 (- CONH –)
1
H NMR: 2.16(3H, s, -COCH3), 2.31(3H, s, Ar-CH3),
7.11 –7.35 (m, 5H, Ar–H and -NH),
Mass: 150 (M+)
Elemental analysis: Calc. for M.F.: C9H11NO (M.W. =
150), C= 72.46%, H=7.43%, O= 10.72%, N=9.39%
Found: C=72.44%, H= 7.58 %, O= 10.70% N=9.38%.
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16. Xu F., Wang N.G., Tian Y.P., Chen Y.M., Liu W.C.,
Synthesis of amides using Ph3P/I2, Synthetic
Communications, 42(23), 3532 ( 2012)
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