Palladium on manganese ferrite: An efficient catalyst for one pot synthesis of primary amides from iodobenzene

Article abstract of DOI:10.1039/c4ra12827c

Amidation of aryl iodide in one pot is reported using Pd-MnFe₂O₄ as a catalyst. The catalyst was characterized by various techniques such as XRD, FEG-SEM, EDS, TEM, BET surface area and ICP AES. K₄[Fe(CN)₆]is used as a non toxic cyanation reagent for in situ generation of benzonitrile and hydrolyzed as soon as it formed. The catalyst was found to be efficient and can be used for several cycles without loss in activity. Good to excellent yields of primary amides were obtained.

Full text of DOI:10.1039/c4ra12827c

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DOI: 10.1039/C4RA12827C
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ARTICLE TYPE
Palladium on Manganese ferrite: an efficient catalyst for one pot
synthesis of primary amides from iodobenzene.
a
a
a
Vilas Gangadhar Jadhav , Jeevan Manohar Bhojane and Jayashree Milind Nagarkar*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
Amidation of aryl halide in one pot is reported using PdꢀMnFe O as a catalyst. The catalyst was
2
4
characterized by various techniques such as XRD, FEGꢀSEM, EDS, TEM, BET surface area and ICP
AES. K [Fe(CN) ]is used as non toxic cyanation reagent for in situ generation of benzonitrile and
4
6
hydrolyzed as soon as it formed . The catalyst was found to be efficient and can be used for several cycles
without loss in activity. Moderate to good yield of primary amides was obtained.
1
0
1
4
1
. Introduction.
in drug delivery and biomedical applications such as MRI .
Besides this, they are also found to be good support for transition
5
0
Primary amides are the most important functionality in
pharmaceuticals, natural products, agrochemicals and
biologically active molecules . Generally, primary amides are
synthesized either by reaction of carboxylic acid or its derivative
with ammonia or its equivalent . They are also synthesized by
different methodologies such as
aldoximes , reaction of aldehydes with ammonia , oxidation of
benzylic alcohols in presence of ammonia
oxidation of benzyl amines . Aminocarbonylation of aryl halide
by using carbon monoxide and ammonia or ammonia equivalent
is also reported as the efficient method for the synthesis of
primary amides. However, this process involves handling of toxic
15
metal catalysts . In particular, palladium supported on super
paramagnetic material is the most important heterogeneous
catalyst as it offers high surface area and easy separation. In
continuation of our work with metal nano particles supported on
1
ꢀ3
1
2
2
3
3
4
4
5
0
5
0
5
0
5
4
15b
55
super paramagnetic material , herein we report palladium
catalytic rearrangement of
6
7
nanoparticles (PdNPs) supported on MnFe
in one pot synthesis of primary amides
O and its application
2 4
8
and catalytic
9
5
gas and reduces its use at kilogram level . Aryl halides with
ammonia in presence of metal carbonyls also have been used for
the synthesis of primary amides, but it leads to release of toxic
carbon monoxide gas and also the metal carbonyl complexes are
1
0
volatile and unstable . Hydration of nitriles is an atom
economical process and numbers of catalytic methods have been
1
1
developed for nitrile synthesis . Hence preparation of nitriles as
an intermediate for amide synthesis is of great importance.
Nitriles are prepared by reaction of aryl halides with various
nitrile sources such as alkali cyanide, CuCN, TMSCN and
K [Fe(CN) ] salt in presence of transition metal catalyst. Among
4
6
these K [Fe(CN) ] is used as a less toxic and cheaper cyanide
4
6
1
2
source for cyanation of aryl halides .
Recently oxidation of benzyl amine to primary amide by using
9
c
Fig.1 General synthesis of primary amide.
OMSꢀ2 catalyst was reported . However, the reaction requires
very high pressure (6 bars) and temperature (160°C) and also
gives side products, where as we have reported general synthesis
of primary amides at mild reaction conditions using magnetically
retrievable catalyst.
Manganese ferrite (MnFe O ) nano crystals possess higher
2
4
6
0
magnetization as compared to magnetite, CoFe O and NiFe O
2 4 2 4
16
nanoparticles . Here we have carried out the tandem synthesis of
primary amide from iodobenzene via in situ generation of
benzonitrile in presence of DMSO: H O solvent system using Pd
2
Magnetically separable catalyst has attracted much attention in
the area of heterogeneous catalyst as it is easily separated by
external magnet and can be used several times without losing its
nano particles supported on MnFe O This is the first report of
2
4.
65
the application of the heterogeneous catalyst for the synthesis of
primary amide and that too using nontoxic nitrile source
1
3
activity . Super paramagnetic materials, spinnel ferrites MFe O
2
4
(M= Ni, Co, Zn,) are one of the important advance materials used
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K [Fe(CN) ] Very good yields of the desired products were
obtained.
4
6 .
3. Results and Discussion
XRD analysis showed peak at 2θ = 30.1, 35.14, 43.41, 54.601,
57.0671and 63.6651 which represent the Bragg reflections from
the (220), (311), (400), (422), (511) and (440) planes
respectively. The crystalline data matches with the JCPDS Card
No. (74ꢀ2403). Palladium peaks at 40, 46 θ values were not
observed because of the low loading of the palladium (Fig 2a).
Displacing value from XRD and TEM SEAD pattern is same and
found to be 2A°. (Fig. 3 c and d)
4
4
5
0
5
0
2
. Experimental
5
2.1 Catalyst preparation.
Catalyst was prepared by using ultrasound assisted
coprecipitation method. FeCl . 6H O (9.5 mmol, 50 mL) and
MnCl .4H O (4.4 mmol, 50 mL) solutions were added in 250 mL
round bottom flask followed by addition of 0.5 g KCl and PdCl2
(60 mg). This mixture was placed in ultrasound bath for 5 min.
Then pH of this mixture was adjusted at 12 by adding 3N NaOH
followed by heating at 60 °C for 30 min. The obtained catalyst
was filtered and washed with distilled water several times and
then by ethanol to remove water. The catalyst was dried under
vacuum at 60 °C for 24 h, and subsequently at 200°C for 4h.
3
2
2
2
1
0
The elemental analysis of PdꢀMnFe O was confirmed by EDS
2
4
analysis as shown in (fig.2 b). The distribution of elements in Pdꢀ
MnFe O4 was Mn =11.45%, Fe = 28.15%, O =59.31% and
2
Pd=1.09%.
1
5
2
.2 Characterization of material
The as synthesized catalyst was characterized by various
techniques such as Xꢀray diffraction (XRD), Field emission gun
Scanning electron microscopy(FEGꢀSEM),Transmission electron
microscopy (TEM), FTIR, ICPꢀAES analysis, BET surface area
The XRD analysis was performed on Shimadzu XRD 2400
instrument using Cu Kα radiation (λ= 1.5406 A°) with scanning
rate 2 degree per minute. TEM analysis was performed over
PHILIPS 2200 instrument. FEGꢀSEM analysis was performed on
TESCAN MIRA Instrument. The energy dispersive Xꢀray
spectral analysis (EDS) image was recorded with an Oxford
instrument at 10 kV. Beam intensity was kept high to get good
response by the detector. Inductively coupled plasma Atomic
Absorption spectrometry (ICP AES) analysis was performed on
ARCOS from M/s. Spectro, Germany. GC analysis is performed
over PerkinElmer Clarus 480 instrument. GCꢀMS Spectra
recorded over Shimadzu QPꢀ2010 Instrument. 1H and 13C NMR
spectra’s were recorded on Agilent 400MHz and 100MHz
instrument respectively.
2
0
25
30
Fig.3 FEG-SEM image a) fresh and b) reused catalyst after fifth
cycle. c) TEM image of catalyst and d) SEAD pattern.
5
6
6
5
0
5
FEGꢀSEM analysis shows highly crystalline morphology of the
catalyst. (Fig. 3 c)
The TEM image of PdꢀMnFe O NPs. (Fig.3 c) clearly indicates
2
4
that NPs are uniform in size with average particle size less than
5 nm. This is in accordance with the average crystallite size
4
obtained by using the Debye−Scherrer equation. The image also
exhibits that the Pd NPs on MnFe O are well dispersed. Pd NPs
2
4
size ranges from 2ꢀ10 nm.
From the N2 adsorption–desorption isotherm of Pd–MnFe O
2
4
NPs, the BET surface area of the particles was found to be
24.9346m2/g and the adsorption average pore width was 315 A°.
Single point surface area at P/Po = 0.254238207: 24.5190 m²/g
(Fig.2 Supporting Information)
35
2 4
Fig.2 a) XRD and b) EDS analysis of Pd-MnFe O
Reaction of iodobenzene with K [Fe(CN) ] was treated as a
4
6
2
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model reaction and various reaction parameters were optimized
reaction conditions. The product yield increased dramatically
for this reaction. Initially (1 mmol) of iodobenzene was treated 40 from 19% to 90% when temperature increased from 90°C to
with 0.25 mmol of K [Fe(CN) ] in the presence of PdꢀMnFe O
4
110°C whereas beyond 110°C no significant increase in the
product yield with increase in temperature was observed (Table 1
entry 13ꢀ15)
4
6
2
catalyst (30 mg, 1mol% Pd ), K CO as a base in DMF :H O
2
3
2
5
(1:1) solvent system, at 100°C, which offered 58 % yield of
benzamide (Table 1, entry 1) Series of experiments were
We also studied the effect of concentration of K [Fe (CN) ] salt
4
6
performed to optimize the various reaction parameters such as 45 on the product yield by increasing the amount from 0.1 mmol to
catalyst loading, solvent, base and temperature of the reaction.
Loading of the catalyst was also the important parameter and it
0.25 mmol. Conversion of aryl halide to benzonitrile was 100% at
0.25 mmol concentration of K [Fe(CN) ]. The reaction was also
4
6
1
1
2
0
5
0
was found that 1 mmol of the catalyst was enough to achieve the
maximum yield of the desired product (Table 1 entry 4). Solvent
study was the important part for this transformation. Various 50 amidation of iodobenzene was found to be 90 and 5 h
carried out at various time intervals and 100% conversion was
‡
obtained in 18 h. For optimized reaction TON and TOF for
−
1
.
solvent systems such as DMF: H O, DMSO: H O and NMP: H O
The applicability of the protocol was examined for various
substituted aryl iodides (Table 2). It was found that electron rich
substrate gave very good yield of the desired product.
2
2
2
were used out of which
a
55
Table 2. One pot synthesis of primary amides from aryl iodides .
Entry
1
Iodobenzene
Amide
Yield
90
Scheme 1. One pot synthesis of amide from iodobenzene
a
.
Table1. Optimization of reaction parameters
Pdꢀ
b
Temperature Yield
EntryMnFe2O4 Base
Solvent: H2O
°C
%
(
mol %)
1
2
3
4
5
6
7
8
9
0.5
0.5
0.5
1
1
1
2
3
1
1
1
1
1
1
1
1
1
1
K CO DMF:H O(1:1)
100
100
100
100
100
110
110
110
110
110
110
110
90
120
140
110
110
110
110
58
64
70
78
84
88
88
88
74
trace
trace
20
19
91
2
3
4
5
20
ꢀ
2
3
2
K CO NMP:H O(1:1)
2
3
2
K CO DMSO:H O(1:1)
2
3
2
K CO DMSO:H O(1:1)
2
3
2
K CO DMSO:H O(2:1)
2 3 2
K CO DMSO:H O(2:1)
2 3 2
K CO DMSO:H O(2:1)
2 3 2
K CO DMSO:H O(2:1)
2 3 2
Cs CO DMSO:H O(2:1)
2 3 2
88
90
1
1
1
0
1
2
TEA DMSO:H O(2:1)
2
DBU DMSO:H O(2:1)
2
KOH DMSO:H O(2:1)
2
1
3
K CO DMSO:H O(2:1)
2
3
2
1
1
1
1
1
1
4
5
6
7
8
9
K CO DMSO:H O(2:1)
2
3
2
K CO DMSO:H O(2:1)
90
ꢀ
2
3
3
3
2
K CO
H O
DMSO
2
2
K CO
2
ꢀ*
c
K CO DMSO:H O(2:1)
90
2
3
2
d
6
7
80
88
1
K CO DMSO:H O(2:1)
90
2
3
2
a
4 6
Reaction conditions: Aryl halide (1mmole), K [Fe(CN)] (0.25 mmole),
b
c
e
Time 12h, base (1.2 mmole), isolated yield., time 18 h. 24 h,
*benzonitrile 92%
2
3
3
5
0
5
DMSO:H O (2:1) was found to be the most suitable solvent
2
system for this transformation(Table1 entry 5). When reaction
was carried out in DMSO solvent only, benzonontrile was formed
(Table1 entry 17).
Iodobenzene was insitu converted to
8
9
90
88
benzonitrile by the cyanating reagent K [Fe(CN) ] which
4
6
immediately gets hydrated to benzamide in the presence of water.
The reaction was also carried out with various inorganic and
organic bases such as TEA, DBU, K CO , KOH and Cs CO , out
2
3
2
3
of which K CO was found to be the most efficient base giving
2
3
maximum yield of the benzamide (Table 1 entry 8). The reaction
was also carried out at various temperatures under optimized
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proceed further, which indicated that there is no leaching of
palladium during the reaction. We also carried out the ICP AES
analysis to test the recyclability of the catalyst for first and fifth
cycles which showed that the palladium leaching was below
detectable level (0.01 ppm).
1
1
0
1
90
78
25
1
00
8
6
4
2
0
0
0
0
O
O
NH2
1
2
84
O
1
2
3
4
5
Recycle
1
1
3
4
84
88
30
Fig 4. Recycle study of the catalyst.
I
1
5
85
81
F
1
6
a
Reaction conditions: Aryl halide (1mmole), K
4
[Fe(CN)
6
] (0.25 mmole),
Fig.5 Plausible Mechanism of the reaction.
b
1
2h, base (1.2 mmole), PdꢀMnFe
2
O
4
(30 mg, 1mol % Pd) isolated yield.
In case of pꢀNO iodobenzene electron withdrawing effect was 35 Plausible mechanism suggests that iodobenzene is oxidatively
2
5
more prominent givinng moderate yield of the desired products.
However, in mꢀNitro iodobenzene the yield was increased due to
minimum electron withdrawing effect. Results are summarized
in (Table 2. entry 6 and 12).
added to the catalyst and then in presence of K
gives benzonitrile which subsequently get hydrolyzed in
presence of water and catalyst to give primary amide.
4 6
[Fe(CN) ] salt
Donating substituents at ortho positions were well tolerated
giving good yield of the corresponding primary amides. We
further studied amidation of bromobenzene as well as
chlorobenzene and observed that bromobenzene gave only 20%
yield of the desired product where as cholrobenzene was
unreactive with optimized reaction conditions(Table 2 entry 2 and
3). Hehteroaryl iodide also gave good yield of corresponding
amide (Table 2 entry 16).
1
0
15
Heterogeneous test for the catalyst
We also examined the heterogeneous nature of the catalyst by hot
filtration test. The catalyst was separated from reaction mass after
half of the reaction time and the filtrate was stirred for required
time under same reaction conditions. The reaction did not
20
40
Fig.6 Magnetic separation of the catalyst a) before and b) after
applying external magnet.
4
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DOI: 10.1039/C4RA12827C
1
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In summary, we have developed the simple and practically
applicable protocol for the synthesis of primary amides from aryl
iodides. PdꢀMnFe2O4 is the first heterogeneous catalyst for such
transformation. Catalyst was found to be efficient for the
transformation of iodobenzenes to respective amides.
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Department of Chemistry, Institute of Chemical Technology, Matunga,
Bhojane,
J.
M.
Nagarkar,
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Mumbai – 400019, India. Fax: +91 22 33611020; Tel.: +91 22
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