Exfoliation effect of PEG-type surfactant on Pd supported GO (SE-Pd(nanoparticle)/GO) in cascade synthesis of amides: A comparison with Pd(nanoparticle)/rGO

Article abstract of DOI:10.1016/j.molcata.2016.02.024

In the presence investigation, a cascade method for the synthesis of primary amides is discussed by the catalysis of Pd supported onto graphene oxide (Pd/GO) nanosheets. Also, the effect of different polyethyleneglycol-type (PEG-type) polyethers including PEG-300, P123 and F127 on the catalytic activity of Pd/rGO is studied in the the reaction of aldehyde and hydroxylamine hydrochloride to give benzamide. Addition of PEG-type polyethers played an important role in raising the catalytic power of Pd(nanoparticle)/GO by exfoliation of GO sheets. The present paper introduces Pd(nanoparticle)/GO as first Pd supported GO for the synthesis of primary amides through this method. This catalyst was highly active, efficient, tolerant, and environmentally benign in one-pot conditions with recyclability at least for 8 runs. Also, this study suggests the prevailing catalytic activity of Pd(nanoparticle)/GO rather to Pd(nanoparticle)/rGO in a comparitive experiment.

Full text of DOI:10.1016/j.molcata.2016.02.024

Accepted Manuscript
Title: Exfoliation effect of PEG-type surfactant on Pd
supported GO (SE-Pd(nanoparticle)/GO) in cascade synthesis
of amides; a comparison with Pd(nanoparticle)/rGO
Author: Sadegh Rostamnia Esmail Doustkhah Behzad
Zeynizadeh
PII:
S1381-1169(16)30058-9
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.02.024
MOLCAA 9790
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
25-1-2016
17-2-2016
20-2-2016
Please cite this article as: Sadegh Rostamnia, Esmail Doustkhah, Behzad
Zeynizadeh, Exfoliation effect of PEG-type surfactant on Pd supported GO
(SE-Pd(nanoparticle)/GO) in cascade synthesis of amides; a comparison
with Pd(nanoparticle)/rGO, Journal of Molecular Catalysis A: Chemical
http://dx.doi.org/10.1016/j.molcata.2016.02.024
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Exfoliation effect of PEG-type surfactant on Pd supported GO (SE-Pd(nanoparticle)/GO) in
cascade synthesis of amides; a comparison with Pd(nanoparticle)/rGO
Sadegh Rostamnia, * Esmail Doustkhah, Behzad Zeynizadeh b,*
a,
a,b
a
Organic and Nano Group (ONG), Department of Chemistry, Faculty of Science, University of
Maragheh, PO Box 55181-83111, Maragheh, Iran. Tel:+98(421) 2276066; Fax: +98(421)
2276066; Email: rostamnia@maragheh.ac.ir; srostamnia@gmail.com
b
Department of Chemistry, Faculty of Science, Urmia University, Urmia 57159-165, Iran.
Tel:+98(441)2972035; Fax: +98(441) 2753172; Email: bzeynizadeh@gmail.com
Graphical abstract
Research highlights



Exfoliation of Pd supported GO (SE-PdNP/GO).
Graphene oxide as advanced support for Pd.
A cascade method for the synthesis of primary amides.
1

Abstract
In the presence investigation, a cascade method for the synthesis of primary amides is discussed
by the catalysis of Pd supported onto graphene oxide (Pd/GO) nanosheets. Also, the effect of
different polyethyleneglycol-type (PEG-type) polyethers including PEG-300, P123 and F127 on
the catalytic activity of Pd/rGO is studied in the the reaction of aldehyde and hydroxylamine
hydrochloride to give benzamide. Addition of PEG-type polyethers played an important role in
raising the catalytic power of Pd(nanoparticle)/GO by exfoliation of GO sheets. The present paper
introduces Pd(nanoparticle)/GO as first Pd supported GO for the synthesis of primary amides
through this method. This catalyst was highly active, efficient, tolerant, and environmentally
benign in one-pot conditions with recyclability at least for 8 runs. Also, this study suggests the
prevailing catalytic activity of Pd(nanoparticle)/GO rather to Pd(nanoparticle)/rGO in a
comparitive experiment.
Keywords: Cascade amidation; Pd(nanoparticle)/GO; reduced graphene oxide; polyethers;
exfoliation.
Introduction
Amide functional groups are placed within a vast range of crucial organic materials including
polymers, peptides, protein, and pharmaceutical compounds [1]. Synthesis of amides by traditional
procedures through the reaction of carboxylic acids (or their activated derivatives such as
chlorides, anhydrides or esters) and amine, could be inconvenient and unselective in a total
synthesis or a densely functionalized compounds. Hence, many other methods are developed [2-
4
]. Among them and based on “green chemistry” desire, cascade-type and tandem amidation
processes are the considerable part of recent developments. Their easier economical processing,
2

costly-reasonable and available starting materials are the advantages to others. Some catalysts are
developed for efficient synthesis of amides [5-8]. However, most of the catalysts could not be
recovered and reused for next times. Recently we developed copper grafted SBA-15 as a recyclable
catalyst in amidation reaction using aldehydes, hydroxylamine hydrochloride in a basic condition
[9]. Now, due to the fact that basic condition is not suitable for silica structure of SBA-15 support,
we aimed to extend our research area to new types of catalytic systems based on Pd which can be
produced and stabilized by efficient carbon-based materials such as graphene oxide (GO) and
reduced graphene oxide (rGO) nanosheets.
Pd-based heterogeneous nanocatalysts [10] is of our interests which are previously developed by
our group [11-15]. Pd based nanocatalysts are generally used in C-C and X-C (X = N, S, O)
coupling reactions such as C-N bond coupling (e.g. primary amide and arylhalide) [16]. However,
there are few reports that a Pd-based material has catalyzed the synthesis of primary amides
through the condensation of hydroxylamine hydrochloride and benzaldehyde in a cascade method.
On the other side, Pd-based catalysts suffer from aggregation and deactivation in each run [17-19].
Necessity of Pd species engagement with a suitable ligand or support is inevitable in order to obtain
an efficient, recyclable, and atom efficient catalyst [20-24].
Pd/carbon based materials are promising catalysts in Pd-catalyzed reaction from the point view of
their recyclability, high yield of production and stability of the catalyst in harsh acid/base
conditions [25]. Due to suitable interaction of Pd species with carbon based structures, Pd
deposition happens on the surface of carbon based materials. Bulkier types of Pd/carbon catalysts
may suffer from higher catalytic amount of Pd/carbon and their lower recyclability and therefore
earlier aggregation of Pd species [26-28]. Deposition of Pd on graphene oxide (Pd/GO) and
reduced graphene oxide (Pd/rGO) are of efficient methods rather to other Pd/carbon based catalysts
3

[
29-32]. However in comparison, rGO and Pd/rGO nanosheets exhibit more tendency to self-
assembly rather to GO and Pd/GO in relatively higher concentrations and temperatures especially
in H O. This may restrict the efficiency of Pd/rGO in some cases by decreasing the catalytic
2
surface area. Recently in our group, we have established the study of Pd/GO and Pd/rGO
exfoliation by surfactant and their catalytic activity in the presence of various surfactants. In this
work, we found that addition of poly ethyleneglycol-type (PEG-type) polyetheric surfactant during
the catalysis of Pd(nanoparticle)/rGO makes a remarkable change in the catalytic activity.
Transition metal-catalysed rearrangement of aldoxime to amide, which is usually catalyzed by
transition metal ions such as Cu [33], Zn [34], Ru [35], Rh [36], and Au [37], is a strategy of
primary amide synthesis. In the present paper, we have studied the catalytic activity of Pd
supported GO in the presence of different PEG-type polyethers. In this cascade method, synthesis
of primary amides from simple aromatic aldehydes and hydroxyl amine were accomplished. To
the best of our knowledge, this is the first report of a Pd supported catalyst in the synthesis of
primary amides through this reaction pathway. Homogeneous Pd(OAc) salt is the only Pd-based
2
catalyst for the direct conversion of benzaldehyde to benzamide [38]. Hence, we applied PEG-type
polyethers for intense exfoliation of Pd/GO to acquire homogeneous behaviour on this catalyst
while keeping itself a recoverable and reusable catalyst.
Results and Discussion
Catalyst synthesis and characterization
Synthesis of the catalyst, Pd(nanoparticle)/GO, was achieved by oxidizing the graphitic carbon to
graphene oxide following our method [13, 15]. Then, in the presence of ultrasonic irradiation (for
exfoliation of GO), Pd species were supported onto GO sheets. For the synthesis of
4

Pd(nanoparticle)/rGO, the reduction of GO and Pd ions were performed through addition of
NaBH as a reductant. However after reduction, tendency towards aggregation of graphene sheets
4
was high. Sonication of the solution before addition of Pd source has a drastic effect on the uniform
distribution of Pd particles onto surface of well exfoliated graphene sheets. On the other hand,
using ultrasonic irradiation during the reaction for long-time reactions is restricted and is not
suitable. Therefore to keep the Pd(nanoparticle)/GO and Pd(nanoparticle)/rGO sheets exfoliated,
we used polyethers to stabilize the exfoliation state of these sheets. For example, the obtained
Pd(nanoparticle)/GO was kept exfoliated by surfactant of F127, to produce SEF127
Pd nanoparticle /GO. A general synthetic pathway for the synthesis of SEF127-Pd(nanoparticle)/GO
is illustrated in Scheme 1.
-
(
)
To characterize the physicochemical properties of the Pd(nanoparticle)/GO, FTIR spectroscopy,
X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy
(
TEM), X-ray analysis (SEM-EDS) and atomic absorption spectroscopy (AAS) were applied. To
2
+
our surprize, supporting Pd leads to reduction and supporting of Pd nanoparticles on the surface
of GO as observed by SEM and TEM images. Accordingly, in this material, Pd nanoparticles are
dispersed on the surface of GO nanosheets. The estimated average particle size of deposited Pd
nanoparticles by SEM and TEM is around 15-22 nm (Figure 1 and Figure 2). The particle size
histogram of Pd(nanoparticle)/rGO shows that particle size ranged from 14 nm to 23 nm (Fig. 1b
and Fig. 2b).
Fig. 3a shows the XRD patterns of Pd(nanoparticle)/rGO and Pd(nanoparticle)/GO. SEM-EDS of
Pd(nanoparticle)/GO is also shown in this figure. SEM-EDS analysis was performed to confirm
the composition of the as-prepared products (Figure 3b). Accordingly, a wide peak around 2θ =
5

2
4o could be assigned to rGO sheets [39], which in the case of Pd(nanoparticle)/GO, the wide peak
o
can be observed around 2θ = 10 . A peak around 2θ = 10° can be also assigned to GO sheets in
Fig 3a. The EDS analysis, the elemental analysis, confirms the existence of elements Pd, C and O
in Pd(nanoparticle)/GO.
Comparison of FTIR spectrum of Pd(nanoparticle)/rGO and Pd(nanoparticle)/GO exhibits the
formation and preservation of rGO chemical structure after Pd supporting. In FTIR of
-1
Pd(nanoparticle)/rGO, a broad band at 3431 cm may be attributed to the hydroxyl and carboxylic
-1
-1
groups. A peak at 1108 cm can be assigned to C-O bonds. A peak at 1574 cm is owing to C=O
-1
bonds. Some peaks in the range of 2870-2969 cm relates to the existence of aliphatic C-H bonds
which are generated following to reduction of some groups in GO (Figure 4).
Catalyst tests
For cascade amidation, as expected, we needed for well-exfoliation of Pd(nanoparticle)/GO sheets
followed by excellent catalysis. Thus, we chose three types of PEG-type polyethers to exfoliate
Pd(nanoparticle)/GO sheets during the catalysis, which includes triblock copolymers of PEO-
PPO-PEO (P123 and F127) and pure polyethylene glycol (PEG-300). The only difference between
P123 and F127 is in their number of monomers, in which F127 (average number of monomers =
265) has a longer chain compared to P123 (average number of monomers = 110). And the main
difference between PEG-300 with two of P123 and F127 is that the later ones have propylene at
the middle and ethylene at both sides while in the case of PEG-300, a homopolymer of ethylene
oxide with 300 monomers can be found.
The presence of propylene causes to produce a hydrophobicity at the middle (propylene motif) of
P123 and F127 and different micellar behaviours in aqueous phase while PEG-300 doesn’t have
6

such property [40]. Regarding to these differences, they were added to solution of
Pd(nanoparticle)/GO to monitor their impact on exfoliation and catalytic behaviour of
Pd(nanoparticle)/GO sheets in the amidation of benzaldehyde under the similar conditions.
Pd(nanoparticle)/GO sheets tend to aggregate and self-assemble in the absence of ultrasonic (US)
or any additive. These three polyethers can well-exfoliate the Pd(nanoparticle)/GO sheets in the
absence of any reactants which are similar, while in the presence of reactants and other additives,
F127 acted well both in exfoliation and catalytic activity. This result shows that the higher number
of monomers rather to P123 has a drastic effect on the obtained results. Also in the case of PEG-
300, which their number are near, in spite of well-exfoliation of Pd(nanoparticle)/GO sheets it
shows that the middle hydrophobic block of F127 and side blocks’ hydrophilicity have made a
balance in hydrophobicity and hydrophilicity of the reaction media which indeed both are
indispensable (Fig. 5).
In the presence of these three selected exfoliating agents, Pd(nanoparticle)/rGO was also put into
examination. To our surprise, these polyethers had no remarkable exfoliating effect on the Pd
supported reduced graphene oxide sheets at higher temperature. We observed that the higher
temperature enhances the interactions of rGO sheets and polyethers are not capable of dominating
these interactions. Therefore, we set aside the further study of Pd(nanoparticle)/rGO catalytic
behaviours in the amidation reaction.
Once investigation on the exfoliation effect of Pd(nanoparticle)/GO was accomplished, we studied
the other effective parameters on the catalytic behaviour of Pd(nanoparticle)/GO in the presence
of F127 (F127 surfactant exfoliated Pd(nanoparticle)/GO = SEF127-Pd(nanoparticle)/GO). Scheme
1
indicates a general route to manufacture and use of catalyst in the amidation syntheses. The
7

amidation reaction in this work is a cascade-type method for converting the benzaldehyde to
benzamide. In this case, hydroxylamine hydrochloride is added to aldehyde and oxime forms
initially. Then after a required reaction time, it converts to benzamide. And hence, we have
developed the chemistry of primary amide synthesis by the catalysis of Pd nanoparticles which are
supported onto GO sheets.
All reactions were optimized by benzaldehyde and NH OH.HCl as model reaction. Our attempt
2
was to engage our catalytic system (SEF127-Pd(nanoparticle)/GO) for the synthesis of primary
amides. Several parameters including base, solvent, and reaction time and temperature were
carefully examined on this reaction. Some of them are represented in Table 1. In this optimization,
DMSO indicates excellent results compared to other solvents during 48 h. K
2
CO
3
and Cs
2
CO had
3
mutual effect on the reaction yield. Therefore owing to economical reason, K
2
CO
3
was preferred.
Once investigation of this matter, we studied the other effective parameters on the catalytic
behavior of Pd(nanoparticle)/GO in the presence of F127 (F127 surfactant exfoliated Pd/GO =
SEF127- Pd(nanoparticle)/GO). Scheme 1 indicates a general route to manufacture and use of
catalyst in the amidation syntheses. The amidation reaction in this work is a cascade-type method
for converting the benzaldehyde to benzamide. In this case, hydroxylamine hydrochloride is added
to aldehyde and oxime forms initially. Then after a required reaction time, it converts to
benzamide. And hence, we have developed the chemistry of primary amide synthesis by the
catalysis of Pd nanoparticles which are supported onto GO sheets.
All reactions were optimized by benzaldehyde and NH OH.HCl as model reaction. Our attempt
2
was to engage our catalytic system (SEF127- Pd(nanoparticle)/GO) for the synthesis of primary
amides. Several parameters including base, solvent, and reaction time and temperature were
carefully examined on this reaction. Some of them are represented in Table 1. In this optimization,
8

DMSO indicates excellent results compared to other solvents during 48 h. K
2
CO
3
and Cs
2
CO
3
had
mutual effect on the reaction yield. Therefore owing to economical reasons, K
2
CO
3
was preferred.
After finding the optimized conditions, other derivatives of primary amides were synthesized
according to the optimized conditions. Accordingly, DMSO was selected as optimized solvent,
F127 as a superior exfoliating agent and K
2
CO as the suitable base. Thus, other derivatives of
3
o
benzamide were synthesized at 120 C during 48-54 h (Table 2). Good to excellent yields of
products were obtained using aromatic aldehydes bearing electron-donating (Table 2, entry 2-5)
or electron-withdrawing (Table 2, entry 6-10) functional groups. Ortho-substituted aryl aldehydes
(Table 2, entry 11) gave comparably lower isolated yields than those of para-substituted
compounds, which can be attributed to steric effects. Similar results were obtained with the
reactions of heteroaromatic aldehydes including thiophene-2-carbaldehyde (Table 2, 12).
F127 was found to be more versatile and efficient for this system and therefore, all
Pd(nanoparticle)/rGO exfoliations during the amidation reactions were performed by F127. The
2
+
yields were comparable with that of homogenous Pd which is previously reported [38]. This
comparison indicate a competitable results of the heterogeneous catalyst against homogeneous Pd
species.
It is to be noted here that for iodine derivative of benzaldehyde, when we performed the reaction
with p-iodobenzaldehyde under the optimized conditions, the main product was homo-coupled
biaryl compound (Scheme 3).
Recyclability study of Pd(nanoparticle)/GO in amidation with benzaldehyde and NH OH as
2
representative for other derivatives were investigated in further step. This investigation
9

demonstrated that the catalyst except F127 has ability to be recovered and reused at least for 8
runs. Figure 6 exhibits obtained yields in each run for each method and 8th run TEM image in
2
+
which the major ratio of Pd ions has been reduced converted to aggregated Pd nanoparticles. As
a result, the related decrease in yields after several runs can be attributed to aggregation of Pd
nanoparticles and subsequently, its catalytic deactivation. Atomic absorptions spectroscopy (AAS)
results also reveals no significant leaching of Pd (less than 10 wt% from total amount of Pd in
Pd/GO) from the surface of graphene oxide.
Due to the fact that there are few reports for these reactions with palladium and we haven’t
investigated the exact mechanism of amidations, we have speculate a possible mechanism for this
process. On the other hand, there are some mechanistic studies and reports that can reinforce our
proposed mechanisms [17, 41, 42]. The mechanism (see SI) indicate two possible pathways to
amide products. In the previous reports, it is claimed that because the labeled oxygen atom on
hydroxyl amine finally appears at carbonyl oxygen of the product, amide, the pathway of
mechanism is majorly pass through path 2, where a cyclic intermediate forms [43]. This proposed
mechanism is mostly for transition metal catalyzed conversion of aldoxime to primary amide.
Also, the catalytic system was compared by other catalysts in this cascade amidation of
benzaldehyde with hydroxylamine hydrochloride (Table 3). This study demonstrated that SEF127
-
Pd(nanoparticle)/GO has superior activity rather to other types of Pd supported catalysts. Based
on this test, Pd(nanoparticle)/GO was more active than Pd(nanoparticle)/rGO which can be due to
the fast aggregation of rGO sheets at higher temperature in the presence of reactants. Aggregation
cause to entrapment of Pd between rGO sheets. In this study, there was 94% of the reactant
10

conversion in which the only 4% of it stopped in aldoxime which shows a higher selectivity
towards the product.
Conclusion
Pd(nanoparticle)/GO as a first Pd-supported nanocatalyst was applied in the cascade synthesis of
amides through the reaction of aromatic aldehyde and NH OH.HCl in oxime formation and then
2
beckman rearrangement in one-pot conditions. GO sheets were highly exfoliated during the
catalysis through various polyethers and converted to a highly dispersive heterogeneous
nanocatalysts. Among polyethers, F127 acted better in the results and exfoliation behaviour. This
catalytic system was successfully applied as a relaively green, recyclable, and efficient system
incascade primary amide synthesis and single-pot amidation. Cascade reactions were
advantageous to their non-cascade corresponding reactions. Some possible mechanisms were
proposed for cascade amidation of aromatic aldehydes.
Experimental
Experimental and Catalyst Characterization
All reagents were purchased from Merck (Germany), Fluka (Switzerland) and Sigma-Aldrich and
used without further purification. A multi-wave ultrasonic generator (Sonicator-3000; Misonix
Inc., Farmingdale, NY, USA), equipped with a converter/transducer and titanium oscillator (horn).
GC analyses was recorded on GC Chrom (Teif Gostar Faraz Co., Iran)
11

Preparation of SE- Pd(nanoparticle)/GO
Graphite oxide was prepared from graphite according to the Hummers method [45]. Briefly,
graphite was oxidized by treating with KMnO
4
and NaNO
3
in concentrated H
2
SO to form graphite
4
oxide, and 2 g of the obtained graphite oxide was exfoliated into graphene oxide (GO) by 400 mL
of water under sonication for 2 h. The conductivity of GO sheets after sonication was 5700 S.cm-
1.
After sonication, a solution of PdCl (0.12 g in 5 mL saline solution) was added to mixture in
2
the presence of ultrasonic irradiation for 2h. The purified Pd(nanoparticle)/GO (2 g) was quickly
dispersed in F127/DMSO solution for further use as the catalyst [2 g Pd(nanoparticle)/GO in 50
mL pure DMSO in the presence of polyether (6 wt%)]. The amount of Pd loaded on GO sheets
was measured by AAS which was 3.8 wt%.
Preparation of SE-Pd(nanoparticle)/rGO
Synthesis of SE-Pd(nanoparticle)/rGO was achieved according to SE-Pd(nanoparticle)/GO
procedure except GO was first reduced to rGO by required amount of NaBH . After separation
4
and washing rGO, it was applied for Pd supporting and the dispersion was prepared according to
procedure of SE-Pd(nanoparticle)/GO.
General procedure for synthesis of primary amides from aldehyde
In a typical method, benzaldehyde (1.0 mmol), hydroxylamine hydrochloride (1.5 mmol),
potassium carbonate (2.5 mmol) and 0.5 mL of as-prepared SEF127- Pd(nanoparticle)/GO in DMSO
were added to reaction media in the presence of 1.5 mL DMSO. The reaction was allowed to stir
at 120 °C. Upon reaction completion, the catalyst was separated by centrifuge and the organic
residue was extracted with dichloromethane and evaporated under reduced pressure. The organic
12

residue was purified by column chromatography. All yields were reported based on isolated
1
13
amount. All products are known and identified by H-NMR, C-NMR spectrum and physical
properties.
Acknowledgement
The authors would like to thanks for financial support from Iran National Science Foundation
(
INSF).
Supplementary data
Supplementary Information (SI) of this article can be found, in the online version, at
www.elsevier.com.
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16

Fig. 1. SEM image (a), Binary-SEM (b) and reflected/zoomed SEM Pd(nanoparticle)/GO and its
d) particle size histogram.
(
Fig. 2. TEM image (a) and its particle size histogram (b).
1
7

Fig. 3. XRD patterns of Pd(nanoparticle)/GO and Pd(nanoparticle)/rGO (a). SEM-EDX of
Pd(nanoparticle)/GO (b).
Fig. 4. FTIR spectra of Pd(nanoparticle)/GO and Pd(nanoparticle)/rGO.
1
8

Fig. 5. Effect of surfactant type and amount on the catalytic activity of Pd(nanoparticle)/GO in
amidation of benzaldehyde (1 mmol) and hydroxylamine hydrochloride (1.5 mmol), potassium
o
carbonate (2.5 mmol) and 0.7 mol% Pd at 100 C during 48 h in 2 mL DMSO mixture.
th
Fig. 6. a) TEM image of Pd(nanoparticle)/GO after 8 run. b) Recyclability study of
Pd(nanoparticle)/GO in amidation with benzaldehyde (5 mmol) and NH
2
OH.HCl (7.5 mmol) and
K
2
CO (12.5 mmol) in the presence of Pd(nanoparticle)/GO /F127 [Pd (0.7 mol%) and F127 (6
3
o
wt%)] during 48 h at 120 C.
1
9

[Pd]cat.
O
Cascade Pd-catalyzed rearrang.
This work
metal-catalyzed rearrang.
NH2
R
OH
[Pd, Rh]cat.
O
N
step 1
step 2
R
H
R
H
O
Acid
R
Beckmann rearrang.
N
H
H
Scheme 1. Rearrangements of oximes to amides and cascade amidation.
Scheme 2. Preparation and application of SEF127-Pd(nanoparticle)/GO.
2
0

Scheme 3. Application of p-iodobenzaldehyde for amidation test.
21

Table 1. Investigation of SEF127- Pd(nanoparticle)/GO for optimizations.
Solvent a
DMSO
Toluene
Time (h) T ( C) Yield (%) b
o
Entry Base
1
2
3
4
5
6
7
8
9
K
K
K
2
2
2
CO
CO
CO
3
3
44
48
100
100
48
80
83
Trace
70
82
90
130
100
130
120
100
100
120
120
3
H
2
O
Na
2
CO
3
DMSO
DMSO
DMSO
DMSO/H
DMSO/H
DMSO/H
K
2
CO
Cs CO
KOH
Cs CO
CO
3
2
3
48
91
2
2
2
O
O
O
72
34
2
3
72
74
c
K
2
3
72
71
a)
The solvents in this section were first used in the dispersion of Pd/GO and then used in the
reactions. b) Isolated yields. c) 0.5 mL of dispersed SEF127- Pd(nanoparticle)/GO (containing 0.7
mol% of Pd and 6 wt% of F127) was used per 1 mmol of benzaldehyde, 1.5 mL DMSO was added
in entry 9 (Other conditions include 1 mmol of benzaldehyde, 1.5 mmol of NH
2
OH.HCl, and the
amount of base for each reaction test is 2.5 mmol).
22

Table 2. Synthesis of primary benzamides under the catalysis of SEF127- Pd(nanoparticle)/GO. a
Entry
Substrate
Product
Time (h)
Yield (%)
1
4
8
8
90
2
3
4
80
85
48
4
5
4
8
4
87
85
5
6
7
8
48
48
48
92
90
84
9
48
86
10
11
12
48
50
48
61
74
81
a
Reaction conditions include 1 mmol of benzaldehyde, 1.5 mmol of NH
2
OH.HCl, 2.5 mmol of
K
2
CO
3
, 0.5 mL water dispersed SEF127- Pd(nanoparticle)/GO (Pd, 0.7 mol% and F127, 6 wt%) in
o
the presence of 1.5 mL DMSO at 120 C.
23

Table 3. Catalytic comparison of Pd species in the amidation.a
Time
h)
Conv.
(%)
70
90
94
Yield
(%)b
50
70
90
Entry
Catalyst
Ref.
(
1
2
3
4
Pd/C (10 wt%)
SBA-15/PrEn-Cu
SEF127-Pd/GO
SEF127-Pd/rGO
10
10
72
72
[44]
[44]
This workc
This work
92
35
a
b
c
Reaction is under optimum conditions. Isolated yields. Similar to preparation procedure of
SEF127-Pd/rGO.
24