Transamidation of carboxamides with amines over nanosized zeolite beta under solvent-free conditions

Article abstract of DOI:10.1016/j.catcom.2016.04.004

A highly efficient approach to transamidation of carboxamides with amines over nanosized zeolite beta under solvent-free conditions has been successfully demonstrated. Transamidation of a variety of amides with amines produced the respective N-alkyl amides in moderate to excellent yields.

Full text of DOI:10.1016/j.catcom.2016.04.004

Catalysis Communications 81 (2016) 29–32
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Catalysis Communications
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Short communication
Transamidation of carboxamides with amines over nanosized zeolite
beta under solvent-free conditions
Durgaiah Chevellaa, Naresh Mameda a,b, Swamy Perakaa,b, Srujana Kodumuri a,
Rammurthy Banothu a,b, Narender Namaa,b,
⁎
a
I&PC Division, CSIR-IICT, Hyderabad 500 007, India
b
Academy of Scientific and Innovative Research, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A highly efficient approach to transamidation of carboxamides with amines over nanosized zeolite beta under
solvent-free conditions has been successfully demonstrated. Transamidation of a variety of amides with amines
produced the respective N-alkyl amides in moderate to excellent yields.
Received 8 January 2016
Received in revised form 31 March 2016
Accepted 9 April 2016
© 2016 Elsevier B.V. All rights reserved.
Available online 13 April 2016
Keywords:
Amides
Amines
Heterogeneous catalysts
Transamidation
Zeolites
Amide bond is one of the most important linkages in nature and also
they have been intensively investigated in organic synthesis [1–3]. Fur-
thermore, it represents a significant functional group that has ubiqui-
tous applications in natural products, pharmaceuticals, fine chemicals
and polymers [4]. In general, substituted amides are synthesized by
the coupling of carboxylic acid derivatives with amines or aryl/alkyl ha-
lides with primary amides [5–6]. However, these procedures have some
drawbacks, such as the lability of the activated acid derivatives and te-
dious experimental procedures [7]. Alternatively, some name reactions
(i.e., Ritter [8], Schmidt [9], Beckmann [10], Ugi [11], Wolff [12], etc.)
and metal catalyzed reactions have been developed for their synthesis
[13–16].
However, reactions of amide group with nucleophiles usually re-
quires harsh reaction conditions due to the poor electrophilic character
of the amide group, which makes the transamidation of amides with
amines, an alternative and attractive method for obtaining the
substituted amides. Amides are relatively inert when compared with
other acyl donors and therefore uncatalyzed transamidation reactions
require forcing conditions [17–18]. Y. L. Khmelnitsky et al. reported
the enzyme-mediated transamidation, but it requires highly evolved
enzymes, long reaction times and limited scope [19]. To overcome
these drawbacks, new homogeneous [20–24] and heterogeneous
[25–30] catalysts have been recently reported. In present days, environ-
mental and economical considerations have raised strong interest in
redesigning commercially important processes to avoid the use of
harmful reagents and the generation of toxic waste. In this regard, het-
erogeneous catalysts can play a key role in the development of eco-
friendly processes in petroleum chemistry and production of chemicals.
Unfortunately, most of the heterogeneous methods suffer from one or
more disadvantages such as limited substrate scope, harsh reaction con-
ditions, need of a solvent and strong base. Considering these, the devel-
opment of environmentally benign and efficient transamidation
approach towards the synthesis of higher amides is still challenging.
Zeolites are uniform microporous crystalline materials and have
widespread applications both in petroleum and fine chemical industries
due to their unique physical and chemical properties, such as uniform
channel size, large internal surface area, unique molecular shape selec-
tivity, strong acidity and good thermal/hydrothermal stability. Zeolite
Hβ has received much attention because of the large available micro-
pore volume, large-pore channel system and the presence of active
sites in different concentrations that are useful in a number of acid-
catalyzed reactions. However, zeolites often show inadequate activity
and/or fast deactivation because of poor diffusion efficiency [31]. The
slow transport in the zeolite micropores leads to unwanted secondary
side reactions or slow reaction rates. In order to get additional benefits
from the unique sorption and shape-selectivity effects in the micro-
pores, the diffusion path length in the micropores should be extremely
small.
Nanozeolites are a type of zeolites which have narrow particle size
distributions with sizes of less than 200 nm. Reducing the particle size
from micrometer to nanometer scale, leads to a significant change in
⁎
Corresponding author at: I&PC Division, CSIR-IICT, Hyderabad 500 007, India.
E-mail address: narendern33@yahoo.co.in (N. Narender).
http://dx.doi.org/10.1016/j.catcom.2016.04.004
1566-7367/© 2016 Elsevier B.V. All rights reserved.

30
C. Durgaiah et al. / Catalysis Communications 81 (2016) 29–32
Table 1
Table 3
Optimization of reaction conditions for the transamidation of benzamide with
Transamidation of benzamide with different amines over nanosized zeolite beta.a
benzylamine.a
Entry
R
Yieldb (%)
1
2
3
4
5
6
7
8
4-MeOC6H4
4-MeC6H4
4-FC6H4
4-ClC6H4
2-ClC6H4
4-BrC6H4
1Me-Ph
2-Napthyl
3-C5H4N
2-C4H3O
2-C4H3S
CH2-Ph
91
93
96
97
90
96
45
62
92
60
62
65
60
62
58
Entry
Catalyst
Temp °C
Yieldb (%)
1
2
3
4
5
6
7
8
HZSM (40)
H-mordenite
HY
NaY
Hβ
MCM-41
Montmorillonite K10
Absence of catalyst
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
Nanosized zeolite beta
135
135
135
135
135
135
135
135
135
100
120
140
135
135
135
135
135
26
57
36
8
72
49
56
25
92
46
70
92
78c
88d
93e
68f
40g
9
10
11
12
13
14
15
9
10
11
12
13
14
15
16
17
Cyclohexyl
C5H11
C15H31
a
Reaction conditions: benzamide (1 mmol), amines (2 mmol), nanosized zeolite beta
(100 mg), 135 °C, 24 h.
b
Isolated yields were calculated based on benzamide.
a
Reaction conditions: 1a (1 mmol), 2a (2 mmol), catalyst (100 mg), 135 °C, 24 h.
Isolated yields.
2a (1 mmol).
2a (1.5 mmol).
2a (2.5 mmol).
Catalyst (50 mg).
Catalyst (25 mg).
b
c
d
e
f
simple and efficient method for the transamidation of amides with
amines over nanosized zeolite beta under solvent-free conditions. To
the best of our knowledge, nanosized zeolite beta catalyzed
transamidation has been not yet reported. Nanosized zeolite beta was
prepared according to the procedure described in our earlier report,
which was systematically characterized by various spectroscopic tech-
niques (SEM, TEM, XRD, FT-IR, MAS-NMR, NH3-TPD and 27Al NMR) [35].
In the initial investigation, the reaction of benzamide with
benzylamine (2 equiv.) was selected as a model system to find out the
best reaction conditions. In order to choose the best catalyst first, the re-
action was subjected with various zeolites, MCM-41 and montmorillon-
ite K10 at 135 °C (Table 1, entries 1–7). Among the various catalysts
investigated, Hβ zeolite exhibited the best catalytic activity and afforded
g
material characteristics and their applications in catalysis and adsorp-
tion. The number of atoms in the unit cell increases as particle size de-
creases and therefore, nanozeolites have large external surface area.
The diffusion path lengths also shortened in nanozeolites as compared
to that in the conventional micrometer zeolites [32–34].
In continuation of our efforts towards the development of novel and
eco-friendly synthetic protocols using zeolites [35] herein, we report a
Table 2
Transamidation of carboxamides with benzylamine over nanosized zeolite beta.a
Entry
R
Yieldb (%)
1
2
3
4
5
6
7
8
Ph
92
72
94
74
73
82
65
65
68
93
82
65
98
68
96
98c
99c
99c
4-MeOC6H4
3-MeOC6H4
4-MeC6H4
3-MeC6H4
4-BrC6H4
2-ClC6H4
4-NO2C6H4
3-NO2C6H4
3-CF3C6H4
PhCHCH
2-C4H3S
2-C5H4N
3-C5H4N
2,5-C4H3N2
H
9
10
11
12
13
14
15
16
17
18
CH3
C2H5
a
Reaction conditions: amides (1 mmol), benzylamine (2 mmol), nanosized zeolite beta (100 mg), 135 °C, 24 h.
Isolated yields were calculated based on amide.
Reactions were carried out at 100 °C.
b
c

C. Durgaiah et al. / Catalysis Communications 81 (2016) 29–32
31
Table 4
in moderate to excellent yields under similar conditions (Table 3). Acti-
vating groups present on aromatic ring of benzylamine yielded the re-
spective products in 91% and 93% yields, respectively (Table 3, entries
1 and 2). Halo substituted benzylamines such as, 4-fluorobenzylamine,
4-chlorobenzylamine, 2-chlorobenzylamine and 4-bromobenzylamine
afforded the corresponding secondary amides in 90–97% yields
Transamidation of benzamide with benzylamine — reusability of the catalysta.
Entry
Cycle
Yieldb (%)
(Table
3,
entries
3–6).
1-Phenylethylamine
and
1-
1
2
3
4
First
92
91
91
88
napthylmethylamine provided the corresponding products in 45% and
62% yields, respectively (Table 3, entries 7 and 8). Heteroaromatic
amines such as, 3-picolylamine, furfurylamine and 2-
thiophenemethylamine gave the desired products in 60–92% yields
(Table 3, entries 9–11). In the case of 2-phenethylamine, the corre-
sponding product was obtained in 65% yield (Table 3, entry 12). Further,
we also investigated the aliphatic primary amines with benzamide and
afforded the respective products in good yields (Table 3, entries 13–15).
The catalyst (nanozeolite) was easily separated from the reaction
mixture by simple filtration. Further, recycling of catalyst was carried
out by performing the reaction of benzamide with benzylamine under
standard reaction conditions and the reused catalyst showed consistent
activity even after fourth cycle of reuse (Table 4). The catalyst was
highly crystalline before and after the reaction, which was confirmed
by XRD (see the ESI Fig. S1).
Based on the literature reports [29,31–33], the plausible reaction
mechanism for the transamidation of carboxamides with amines over
nanosized zeolite beta is illustrated in Scheme 1. It is assumed that
amide is adsorbed on the Bronsted acid sites of zeolite, which subse-
quently reacts with amine followed by elimination of ammonia yields
the desired transamidation product.
In summary, an effective and green protocol for the transamidation
of carboxamides with amines over nanosized zeolite beta under
solvent-free conditions has been successfully developed. Notable ad-
vantages offered by this method are absence of organic solvent, broad
substrate scope, high atom economy, use of non-hazardous and reus-
able catalysts, higher yields of the desired products and simple work-
up procedure, which makes it an attractive and useful alternative to
the existing methods.
Second
Third
Fourth
a
Reaction conditions: benzamide (1 mmol), benzylamine (2 mmol), nanosized zeolite
beta (100 mg).
b
Isolated yields.
the corresponding secondary amide in 72% yield (Table 1, entry 5). Fur-
ther, to improve the yield of 3a, we examined the reaction with
nanosized zeolite beta under similar conditions, which produced
much higher yield (92%) as compared to other catalysts (Table 1,
entry 9).
Once nanosized zeolite beta was found as the best catalyst, the influ-
ence of the reaction temperature was studied. By varying the tempera-
ture from 135 to 100 °C, a gradual decreasing in yield (92 to 46%) was
observed and further increase in temperature did not have any account-
able effect on the yield (Table 1, entries 9–12). Next, we studied the ef-
fect of mole ratio of benzamide to benzylamine from 1:1 to 1:2.5 under
the similar conditions, which had a considerable effect on the product
yield (Table 1, entries 13–15). The present reaction was also conducted
with different amounts of catalyst and it was revealed that 100 mg of
catalyst gave the best results (Table 1, entries 9 and 16–17). In the ab-
sence of catalyst, the corresponding product was obtained in lower
yield (25%) (Table 1, entry 8). As can be seen from the above presented
results, the optimized reaction conditions to acquire the highest yield
for this transamidation reaction are 1:2 mol ratio of benzamide to
benzylamine at 135 °C over nanosized zeolite beta (100 mg).
Toexplorethescopeandlimitationsofthepresentsystemundertheop-
timizedconditions,avarietyofamideswerereactedwithbenzylamine,
furnishedmoderatetoexcellentyieldsofthecorrespondingsecondaryam-
ideswithhighdegreeoffunctionalgrouptolerance(Table2).Inordertode-
terminetheinfluenceofsubstitutiononthearomaticringofbenzamide
with this reagent system, we have carried out the reaction of different
substitutedbenzamideswithbenzylamine.Activatinggroupspresenton
aromaticringofbenzamideaffordedgoodtoexcellentyieldsoftherespec-
tivesecondaryamides(Table2,entries2–5).Deactivatinggroupspresent
onthearomaticringofbenzamideyieldedmoderatetoexcellentyieldsof
the corresponding secondary amides (Table 2, entries 6–10).
Cinnamamidereactedsmoothlyandfurnishedthecorrespondingproduct
in82%yield(Table2,entry11).Heteroarylamidessuchas,thiophen-2-
carboxamide,picolinamide,nicotinamideandpyrazine-2-carboxamide
alsoprovidedthecorrespondingproductsin65–98%yields(Table2entries
12–15).Further,weexaminedthetransamidationofaliphaticprimaryam-
ideswithbenzylamine,whichgavetherespectiveproductsinexcellent
yields(Table2,entries16–18).
We thank the CSIR Network project CSC-0123 for financial support.
Ch. D. and M.N. thank the CSIR and. P.S., K.S. and B. R. the UGC, India
for a fellowship.
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2016.04.004.
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