Novel oxime-palladacycle supported on clay composite as an efficient heterogeneous catalyst for Sonogashira reaction

Article abstract of DOI:10.1016/j.ica.2018.08.043

A novel supported catalyst formed by an oxime-derived palladacycle supported on clay OxPdCy@clay is synthesized and characterized. This palladium composite promotes the Sonogashira reaction of aryl iodides, bromides and chlorides with terminal alkynes in polyethylene glycol200 at 85 or 130 °C using 0.05–0.1 mol% of palladium loading under copper and phosphine free conditions. This supported palladacycle, OxPdCy@clay, showed a superior catalytic activity than dimeric oxime-palladacycles. Mechanistic studies about the heterogeneous or homogeneous nature of the catalyst show that catalyst is working mainly under heterogeneous conditions. This supported palladacycle OxPdCy@clay can be recycled by simple centrifugation and reused for at least nine consecutive runs with small decrease in activity.

Full text of DOI:10.1016/j.ica.2018.08.043

Accepted Manuscript
Research paper
Novel Oxime-palladacycle Supported on Clay Composite as an Efficient Het-
erogeneous Catalyst for Sonogashira Reaction
Mohammad Gholinejad, Neda Dasvarz, Carmen Nájera
PII:
S0020-1693(18)30888-0
https://doi.org/10.1016/j.ica.2018.08.043
ICA 18443
DOI:
Reference:
Inorganica Chimica Acta
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11 August 2018
24 August 2018
Please cite this article as: M. Gholinejad, N. Dasvarz, C. Nájera, Novel Oxime-palladacycle Supported on Clay
Composite as an Efficient Heterogeneous Catalyst for Sonogashira Reaction, Inorganica Chimica Acta (2018), doi:
https://doi.org/10.1016/j.ica.2018.08.043
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Novel Oxime-palladacycle Supported on Clay Composite as an Efficient Heterogeneous
Catalyst for Sonogashira Reaction
Mohammad Gholinejad,ab* Neda Dasvarz,a Carmen Nájerac*
aDepartment of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), P. O. Box
45195-1159, Gavazang, Zanjan 45137-66731, Iran. Email: gholinejad@iasbs.ac.ir
bResearch Center for Basic Sciences & Modern Technologies (RBST), Institute for Advanced
Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
cDepartamento de Química Orgánica and Centro de Innovación en Química Avanzada (ORFEO-
CINQA). Universidad de Alicante, Apdo. 99, E-03080-Alicante, Spain. Email: cnajera@ua.es
Abstract: A novel supported catalyst formed by an oxime-derived palladacycle supported on clay
OxPdCy@clay is synthesized and characterized. This palladium composite promotes the
Sonogashira reaction of aryl iodides, bromides and chlorides with terminal alkynes in
polyethylene glycol200 at 85 or 130 °C using 0.05-0.1 mol% of palladium loading under copper
and phosphine free conditions. This supported palladacycle, OxPdCy@clay, showed a superior
catalytic activity than dimeric oxime-palladacycles. Mechanistic studies about the heterogeneous
or homogeneous nature of the catalyst show that catalyst is working mainly under heterogeneous
conditions. This supported palladacycle OxPdCy@clay can be recycled by simple centrifugation
and reused for at least nine consecutive runs with small decrease in activity.
Keywords: Clay composite, Oxime-palladacycle, Sonogashira, Copper-free, PEG 200
1

1. Introduction
The Sonogashira reaction has proven to be a powerful methodology for the synthesis of alkynes
and conjugated enynes via reaction of aryl or alkenyl halides or triflates with terminal alkynes
[1–13]. In general, alkynes are versatile starting materials for the preparation of interesting
chemicals especially natural products, agrochemicals, and pharmaceutical compounds [14–17].
This alkynylation reaction can be performed either in the presence of copper as co-catalyst or
under copper-free conditions (the original Cassar–Heck version of this reaction) [1–13]. In spite
that the addition of copper can increase the efficiency of the reaction, formation of 1,3-diynes via
homocoupling of alkynes (Glaser reaction) is one of the most important disadvantages of Pd/Cu
catalyzed Sonogashira reaction[18–20]. In addition, a large excess of base, namely Et3N or
pyrrolidine, has to be used under copper catalysis. Consequently, using new palladium catalysts
for performing the Sonogashira reaction under efficient copper- and amine-free conditions is
highly desirable. Another important aspect is the low reactivity of aryl chlorides being still rather
challenging specially in the Sonogashira reaction.
Recently various homogeneous and heterogeneous Pd catalysts have been introduced for the
Sonogashira reaction under copper-free conditions [12-28]. Despite increased progress on the
higher efficiency and selectivity of most of the homogeneous catalysts, they suffer from
problems of separation of products and catalysts and also the recovery of Pd are the main
concerns for industrial applications. Among the different palladium catalysts used for different
coupling reactions, oxime-derived palladacycles showed excellent reactivity and selectivity [29–
46]. In the case of the Sonogashira reaction this process can be performed under Cu-free
conditions but only with aryl iodides and bromides as substrates [40,41]. In addition, associate
problems to the homogenous systems are still remained in these catalysts. For solving these
2

problems, in recent years, some studies have been made for heterogenization of the oxime-
derived palladacycles via their immobilization on different supports. Along this line, oxime
palladacycles supported on polymers[47–51], periodic mesoporous organosilica [52], magnetic
nanoparticles (Fe3O4) [53], silica [54], self-supported oxime palladacycles [55,56], phosphonium
[57] and fluorous tagged [58,59] and graphene oxide- [60] supported oxime-derived
palladacycles have been employed as heterogeneous catalysts in different cross-coupling
reactions.
Clay minerals with high surface area and ion exchange properties can be found widely in nature
and have been used as catalysts and as green supports for the stabilization of transition metal
catalysts. Natural untreated clays have low ability to use as the catalyst or support for
stabilizations of metals. However, in order produce high surface area, porosity, and thermal
stability, clay materials can be modified by various methods. In recent years, different methods
have been applied for modification of clay minerals and their subsequent application for
stablizations of transition metals and catalysis [61–64]. Regarding this subject, different clay
supported palladium catalysts have been synthesized and applied in several organic
reactions[65–79]. Rao and co-workers prepared water dispersible sheets of Mg-
phyllo(organo)silicates containing pendant amino ligands and used it for stabilization of Au, Ag,
Pd, and Pt nanoparticles [80]. However, to the best of our knowledge there is no report dealing
with clay supported oxime palladacycle and its application in coupling reactions. In continuation
of our interest in heterogeneous Sonogashira reaction [81-85] herein, we wish to report a new
catalyst based on an oxime-palladacycle supported on clay composite and its application as
efficient heterogeneous catalyst for copper, amine and phosphine-free Sonogashira reaction in
polyethylene glycol 200 (PEG 200).
3

2. Results and Discussion
For the preparation of the clay composite, the appropriate oxime derived from N-acryloyl-4-
aminoacetophenone was synthesized (Scheme 1). Thus, 4-aminoacetophenone was allowed to
react with acryloyl chloride in dry THF and the resulting acrylamide was treated with
hydroxylamine hydrochloride in the presence of ZnO as a catalyst. A clay composite containing
the thiol functional group 1 was prepared by reaction of MgCl2.6H2O with 3-mercaptopropyl
trimethoxysilane and NaOH in aqueous ethanol. The results of porosimetry revealed the BET
surface area of 68 m2g-1. Then, the resulted clay composite 1 was allowed to react with the oxime
via a thio-Michael addition giving the supported oxime 2. Finally, the clay supported oxime 2
was treated with Na2PdCl4 in the presence of sodium acetate in MeOH affording the desire final
clay oxime-palladacycle 3. This combination is referred to as OxPdCy@clay throughout the text
of this article. Loading of palladium on composite 3 was determined using atomic absorption
spectroscopy showing to be 0.025 mmol g-1.
4

Scheme 1. Steps for the preparation of OxPdCy@clay 3.
The presence of organic group in the structure of SH@Clay 1 was confirmed using
thermogravimetric analysis (TGA) which showed two step weight losses (Figure 1). The first
weight loss is related to water and physically adsorbed solvents and the second one is related to
the organic residues attached to the surface of the support. Also, thermogravimetric analysis of
the clay supported oxime 2 showed two main weight losses (Figure 1). It is worth mentioning
that an increase in the second weight losses is probably related to the added oxime unit which
increase loading of organic moiety.
Transmission electron microscopy (TEM) of the OxPdCy@clay 3, showed presence of clay
layers (Figure 2).
5

Figure 1. Thermogravimetric diagram of the SH@Clay 1 (red) and clay supported oxime 2
(green).
Figure 2. TEM images of OxPdCy@clay 3.
SEM image and resulting (Figure 3) elemental mapping study showed uniform distribution of the
elements and confirmed presence of C, Mg, N, O, Pd, S, and Si, elements in the structure of
OxPdCy@clay (Figure 4 a-g). Overly EDS-map image confirms almost uniform distribution of
Pd with little aggregation over the structure (Figure 4h)
6

Figure 3. SEM image of OxPdCy@clay 3.
7

Figure 4. EDS mapping images of clay OxPdCy@clay 3: a) C, b) Mg, c) N, d) O, e) Pd, f) S, g)
Si and h) total mapping of elements.
The X-ray photoelectron spectrum (XPS) of the clay supported oxime-palladacycle 3 for Mg 1s
region showed a single peak in position of 1303.6 eV, which fits well with MgO structure
8

(Figure 5a) [87]. Also, N 1s peak of palladium composite in nitrogen region can be differentiated
into two peaks at the BEs of 399.3 and 399.8 eV, which belong to nitrogen atoms in C-N and
C=N−OH species, respectively (Figure 5b) [88]. The analysis results of the Si 2p spectra
confirmed presence of binding energy of 101.3 eV and 102.2 eV which are related to Si-C or Si-
O-C and Mg-O-Si bonds respectively (Figure 5c) [89,90]. In Figure 5d, the dual peaks at 163.8
and 162.7 eV with an intensity ratio of 1:2 are due to spin orbit coupling and are characteristic of
S 2p1/2 and 2p3/2[91–93]. In addition, XPS of the composite in Pd region confirm Pd(II) is the
main oxidation state of the Pd in the composite. The results showed the presence of two intense
doublets at peaks at 337 and 342 eV related to Pd(II) corresponding to Pd 3d5/2 and Pd 3d3/2,
respectively (Figure 5e) [94]. Curve fitting results of the O 1s showed two peaks at 531.2 and
533.1 for the for the MgO and Si−O−Mg, respectively (Figure 5f) [90].
9

Figure 5. XPS spectrum of the OxPdCy@clay 3 in a) Mg, b) N and c) Si, d) S, e) Pd, f) O
regions.
Application of prepared supported oxime-derived palladacycle 3 in the Sonogashira alkynylation
reaction in the absence of copper as co-catalyst was next assessed. Initially, the reaction of
iodobenzene with phenylacetylene was selected as a model reaction and the effect of different
parameters such as solvent, catalyst loading, type of base and reaction temperature were studied
(Table 1). When 0.1 mol% of Pd loading and different solvents with DABCO as base at 85°C
were used, (Table 1, entries 1-6) tolane was obtained in high 92% yield in the case of DMF
(Table 1, entry 2). When K2CO3 was used as base in different solvents (Table 1, entries 7-9)
higher 95% yield was obtained in PEG 200 (Table 1, entry 8). Selecting DMF and PEG 200 as
10

solvents the reaction was carried out at 50 °C affording low yields (Table 1, entries 10 and 11).
By lowering the catalyst loading to 0.05 mol% (Table 1, entries 13-16), the yield of the reactions
using PEG 200 and K2CO3 did not changed and 96% yield was achieved (Table 1, entry 14). This
higher activity in polar solvents such as DMF and PEG 200 (Table 1, entries 2, 6, 8, 12 and 14)
is may attributed to high dispersion of the solid catalyst as well as solubility of organic substrate
and easier interaction of staring materials with active catalyst sites. Therefore, we select 0.05
mol% catalyst, PEG 200 as a solvent, K2CO3 as the base and 85°C as the most efficient and
optimized reaction conditions. It is worth mentioning that, polyethylene glycols (PEGs) and their
derivatives which have negligible vapor pressure, are known to be inexpensive, thermally stable,
recoverable, non-toxic compounds which serve as suitable media for environmentally friendly
and safe chemical reactions [95]. It should be noted that using similar oxime-palladacycle
supported on SiO2, OxPdCy@SiO2, as catalyst reactions gave lower yield than OxPdCy@clay
(Table 1, entry 17).
Table 1. Optimization of the reaction conditions for the reaction of the iodobenzene and
phenylacetylene.a
Entry Mol (%)
Solvent
H2O
Base
T(C) Yield (%)b
1
2
3
4
0.1
0.1
0.1
0.1
DABCO
DABCO
DABCO
DABCO
85
85
85
85
79
92
12
73
DMF
Toluene
1,4-Dioxane
11

5
0.1
0.1
CH3CN
PEG
H2O
DABCO
DABCO
K2CO3
85
85
85
85
85
50
50
85
85
85
85
50
85
82
87
24
95
5
6
7
0.1
8
0.1
PEG
DMF
DMF
PEG
DMF
PEG
PEG
DMF
PEG
PEG
K2CO3
9
0.1
K2CO3
10
11
12
13
14
15
16
17
0.1
DABCO
DABCO
DABCO
DABCO
K2CO3
6
0.1
14
90
71
96
10
20
73
0.05
0.05
0.05
0.05
0.05
0.05
K2CO3
K2CO3
K2CO3
aReaction conditions: iodobenzene (0.5 mmol), phenylacetylene (0.75 mmol), base (0.75 mmol),
solvent (1.5 mL).
bYield determined by GC.
cReactions using OxPdCy@SiO2
With the optimized reaction conditions in hand, the Sonogashira reaction of structurally different
aryl halides and terminal alkynes was studied (Table 2). Reactions of structurally different aryl
iodides, having electron-donating groups such as OMe and alkyl as well as and aryl iodides
bearing electron-withdrawing groups such as Cl, CN, and NO2, with aryl acetylenes, propargyl
alcohol and 1-octyne proceed well affording the corresponding internal alkynes in high to
12

excellent yields (Table 2, entries 1-16). Results indicated that reaction of sterically hindered 2-
iodotoluene and 2-iodocumene with phenylacetylene or propargyl alcohol took place in good
yields (Table 2, entries 7-9). Also, reaction of heterocyclic 2-iodothiophene proceed efficiently
and gave excellent isolated yields (Table 2, entries 10-11). Reactions of aryl iodides with
aliphatic alkynes such as propargyl alcohol and 1-octyne were performed well and desired
products were obtained in 87-92% yields (Table 1, entries 12-16).
Alkynylation reactions of aryl bromides were much slower than with iodides and our initial study
on reaction of 1-bromo-4-nitro benzene with phenylacetylene under optimized reaction
conditions afforded the corresponding alkyne only in 65% GC yield. Therefore, for improving
the low reactivity of aryl bromides, the loading of catalyst was increased to 0.1 mol% of Pd.
Under these reaction conditions aryl bromides substituted by electron-donating and electron-
withdrawing groups gave the corresponding alkynes in high yields (Table 2, entries 17-25). It
should be noted that the arylations of phenylacetylene performed with heterocyclic bromides
such as 5-bromopyrimidine and 2-bromopyridine took place efficiently affording the
corresponding products in 89% and 92% yield, respectively (Table 2, entries 21 and 22).
Reaction of 4-chloronitrobenzene under optimized reaction conditions and using 0.1 mol%
catalyst was sluggish. For that reasons, the reaction temperature was increased to 130 °C. Under
this reaction conditions 4-chloronitrobenzene, 4-chlorotoluene, 4-chloroanisole, and 4-
chloroacetophenone provided the resulting alkynes in moderate to excellent yields (Table 2,
entries 26-29).
Table 2. The reactions of structurally different aryl halides with alkynes in the presence of clay
supported oxime-palladacycle 3.a
13

Entry
1
Ar1
R2
Product
Yield(%)b
90
C6H5
I
2
3
4
5
6
C6H5
C6H5
C6H5
C6H5
C6H5
88
94c
96
92
92
MeO
Me
I
Me
CN
NO2
I
Me
Me
7
8
9
C6H5
88
85
83
C6H5
I
Me
OH
HOCH2
Me
14

10
11
C6H5
93
S
Me
4-MeC6H4
96c
S
12
13
14
HOCH2
HOCH2-
HOCH2
90
92
91
OH
OH
S
Cl
OH
I
15
16
17
CH3(CH2)5
CH3(CH2)5
C6H5
87
90
83c
S
Me
Me
Br
Me
Me
Br
18
C6H5
71
O
C
Me
19
20
C6H5
C6H5
90
91
CHO
O
C
H
Br
15

N
N
21
22
23
24
C6H5
88
C6H5
90
N
NO2
NO2
NO2
C6H5
90(53)d
91
Br
Br
Me
NO2
4-MeC6H4
CF3
CF3
25
C6H5
96c
NO2
COCH3
Me
NO2
26
27
28
29
C6H5
C6H5-
C6H5
C6H5
90c
84c
81c
61c
Cl
O
C
Me
Cl
Me
Cl
OMe
OMe
Cl
a Reaction condition: ArX (0.5 mmol), alkyne (0.75 mmol) K2CO3 (0.75 mmol), catalyst 3 (0.05
mol% Pd for ArI and 0.1 mol% Pd for ArBr and ArCl), reaction time 24 h for ArI and ArBr, and
48h for ArCl, under argon atmosphere.
16

b Isolated yields.
c GC yields.
dReaction was performed using OxPdCy@SiO2
Comparison activity of OxPdCy@clay (3) with reported oxime-palladacycles and also with some
other catalysts in common Sonogashira coupling reaction showed higher catalytic activity of
OxPdCy@clay in the most of cases.
Table 3. Comparative catalytic activity of OxPdCy@clay (3) with other reported catalysts in
Sonogashira reaction
Loading
[Pd mol%]
Yeild
[%]
Catalysis
T[C], t[h]
C,N,C-tridentate pincer carbene ligand[96]
87,1
1.8
0.2
94
98b
92
PS-supported palladacycle[97]
90, 72
100, 6
NCN-Pincer Palladium Complexes[98]
0.01
17

Palladacycle [Pd(k2-C,N-C¼(C6H5)-
C(Cl)CH2NMe2)(µ-Cl)]2 (1)[99]
80, 4
0.5
74c
99b
PEG-anchored carbapalladacyle[100]
150, 24
80, 0.3
5
2
2-Aminodiphenyl
phosphinite/Pd(OAc)2[101]
90
Ammonium tagged oxime
carbapalladacycle 5.[102]
80,12
140, 7
100, 7
80, 4-24
90, 6
0.047
0.5
0.05
1
90
96
Oxime-derived fluorous-tagged
palladacycle 1[58]
Fe3O4/oleic acid/Pd [103]
tetrakis-piperidine-4-ol/Pd/C[ref 21]
Pd–NHC@SP–PS [ref 22]
41c
82d
89b
85
1
C,N-palladacycle.[ref 24]
100, 3
0.1
a ArX: Iodobenzene
b ArX: 4-bromoacetophenone
c ArX: 2-bromopyridine
18

The recoverability and reusability of the palladium catalysts become a main factor from the point
of view of economic and environmental sustainability. For this purpose, the recyclability of the
catalyst was performed using the model reaction, iodobenzene and phenylacetylene under
optimized reaction conditions. By means of the GC analyses, yields of the reaction up to run 9
did not change and catalyst preserved its activity. However, the yield of the reaction decreased
slightly to 90% in run 10 and from run 10 to 12 the yield of the reaction significantly decreased
to 73%.These results indicated that this catalyst is recyclable for at least 9 consecutive runs with
only a very small decrease in activity (Figure 6).
Figure 6. Recycling of the catalyst 3 for the reaction of iodobenzene with phenylacetylene.
In order to find out why suddenly the yield was dropped after the nine cycle, the amount of Pd
leaching to reaction mixture in each cycle was measured by atomic absorption spectroscopy
(Figure 1 in supporting information). Results indicated that from run 1 to run 9 the amount of
leaching was increased slowly and around 20% of Pd was leached in run 9. However, after run 9,
Pd was leached intensely and in run 12, 52% of Pd was leached to the reaction mixture.
Therefore, it seems that leaching of Pd from solid catalyst and its loading decreasing is
responsible for dropping catalytic activity.
19

In order to get information about the nature of this catalysis, we studied hot filtration test for the
reaction of iodobenzene with phenylacetylene under the optimized reaction conditions. During
this test, the catalyst after 2 h of progress of the reaction (22% GC yield) was removed by
filtration and the filtrate was allowed to react for 24 h. GC analysis of the reaction after 24 h
showed only 38% GC yield. Usually positive hot filtration test results can be assumed as
evidence for homogeneous catalysis, whereas a negative hot filtration test does not certainly
show the emergence of heterogeneous catalysis due to possibility of fast deactivation or
redeposition of soluble active species. Therefore we used poly(vinylpyridine) (PVPy 2% cross-
linked) as a poising agent for soluble palladium species for the reaction of iodobenzene and
phenylacetylene. Results indicated that after addition of PVPy with a 200:1 molar ratio
(PVPy:Pd) the reaction rate decreased, although a 83% GC yield after 24 h was obtained. It is
suggested that “naked” molecular palladium species are examples of homogeneous catalysts that
should be affected by Hg(0), as a consequence of their lack of strong protecting ligands[104-
106]. Addition of Hg(0) to the reaction mixture in the presence of the starting reagents with a
200:1 molar ratio (Hg:Pd) was not significantly effect to the reaction and diphenylacetylene was
formed in a moderate yield of 65% after 24 h (Figure 7).
20

Figure 7. Reaction of iodobenzene and phenylacetylene: a) under optimized reaction conditions,
b) in the presence of PVP poisoning, c) in the presence of Hg(0), and d) hot filtration test.
Furthermore, TEM images of the catalyst after the 3rd run showed the presence of Pd
nanoparticles in the structure (Figure 8). These experiments indicated that this supported catalyst
is working mostly under heterogeneous conditions and same part of the catalysts leached and
produced Pd nanoparticles.
Figure 8. TEM images of reused catalyst after 3rd run.
Conclusions
21

In conclusion, we have prepared and characterized a new heterogeneous clay-supported oxime
palladacycle catalyst. This palladium composite showed higher catalytic activity in Sonogashira
reaction than the related dimeric palladacycles because not only aryl iodides but also aryl
bromides and chlorides can be efficiently used for the arylation of different terminal acetylenes.
Reactions proceed under green conditions, in the absence of phosphine ligands and copper co-
catalyst in polyethylene glycol 200 as an eco-friendly solvent at 85-130 °C. This catalyst can be
easily recovered by simple centrifugation and reused for at least nine cycles without detriment to
its catalytic activity. Different tests such as addition of PVP, hot filtration, and mercury support
that catalyst works mainly under heterogeneous conditions.
3. Experimental Section
3.1.Materials
All materials were purchased from Sigma-Aldrich, Acros and Merck Millipore. 1H NMR and 13C
NMR spectra were recorded at 400 MHz and 100 MHz, respectively on a Bruker Avance HD.
Chemical shifts are given on the δ-scale in ppm, and residual solvent peaks were used as internal
standards. Reactions were monitored by thin layer chromatography (TLC) using Merck silica gel
60F254 glass plate with 0.25 mm thickness. Column chromatography was carried out on silica
gel 60 Merck (230-240 mesh) in a 2 cm diameter column. The TEM and SEM images (EDX)
were captured with EOL JEM-2010 and JEOL JSM 840 respectively. Porosimetry analysis was
carried out with BEL, Belsorp max Instrument. XPS analyses were performed using a K-Alpha
spectrometer. BET surface area was measured using BEL, Belsorp maxInstrument.
3.2.General procedure for the preparation of N-(4-acetylphenyl)acrylamide:
22

4-Aminoacetophenone (3 mmol, 405 mg) was added to a flask containing dry THF (7 mL) and
the mixture was cooled to 0 °C in an ice bath. Then, acryloyl chloride (3.3 mmol, 0.25 mL) was
added slowly under argon followed by the adition of Et3N (4.2 mmol, 0.57 mL) and the reaction
mixture was stirred for 24 h at 25 °C. The resulting suspension was filtered off and the resulting
1
N-(4-acetylphenyl)acrylamide was obtained in 86% isolated yield and was characterized by H
NMR and 13C NMR.
3.3.General
procedure
for
the
preparation
of
N-[4-(1-
(hydroxyimino)ethyl)phenyl]acrylamide
To a flask containing N-(4-acetylphenyl)acrylamide (3 mmol, 0.57 g), a mixture of THF:CH3CN
(1:1) (6 mL) was added. Then, ZnO (6 mmol, 0.48 g) and NH2OH·HCl (12.9 mmol, 0.9 g) were
added and the mixture was heated at 60 °C during 48 h. The suspension was cooled to rt, filtered
off, and the filtrate was subjected to column chromatography using hexane and ethyl acetate as
eluents. Pure N-[4-(1-(hydroxyimino)ethyl)phenyl]acrylamide was obtained in 79% isolated
yield and characterized by 1H NMR,13C NMR and HRMS.
3.4.Synthesis of magnesium phyllo(organo)silicates having thiol group 1:
Clay having the thiol functional group 1 was synthesized following a described procedure[107].
3-Mercaptopropyltrimethoxysilane (10 mmol, 2.1 mL) was added to a solution of MgCl2·6H2O
(8.3 mmol, 1.68 g) in ethanol (50 mL). Then, an aqueous 0.05 M NaOH solution (10 mmol, 200
mL) was added quickly and the white suspension stirred for 24 h at room temperature. The
precipitated white solid was isolated by centrifugation, washed with water (3×50 mL) and
ethanol (1×50 mL) and dried at 65 °C in air.
3.5.General procedure for the preparation of clay supported oxime-palladacycle
23

Clay functionalized thiol group SH@Clay 1 (1 g) was sonicated in CH3CN (10 mL) for 5 min
and N-(4-(1-(hydroxyimino)ethyl)phenyl)acrylamide (3 mmol, 0.61 g) and Et3N (4 mmol, 0.56)
were added. The resulting mixture was stirred at 75 °C for 24 h at reflux under argon
atmosphere. Then, the mixture was subjected to centrifugation and the obtained solid was
washed with CH3CN (2×10 mL) and CH2Cl2 (10 mL) and dried at 100 °C in an oven. Finally,
the clay supported oxime (0.5 g) was sonicated in MeOH (5 mL) for 10 min and a solution of
Na2PdCl4 (0.017mmol, 6 mg) in MeOH (1 mL) and NaOAc (0.5 mmol, 41 mg) was added and
the mixture was stirred at room temperature for 72 h under argon atmosphere.
3.6.General procedure for the Sonogashira reaction
To a mixture of the catalyst 3 (20 mg containing 0.05 mol% Pd for aryl iodides and 40 mg
containing 0.1 mol% Pd for aryl bromides and chlorides), aryl halide (1 mmol), alkyne (1.5
mmol), and K2CO3 (1.5 mmol, 207 mg) was added PEG 200 (2 mL) under argon atmosphere.
The reaction mixture was stirred for the appropriate reaction time at 85 or 130 °C (see, Table 2).
The progress of the reaction was monitored by using gas chromatography. After completion of
the reaction, pure products were obtained by using column chromatography with hexane and
ethyl acetate as eluents.
Acknowledgements
The authors are grateful to Institute for Advanced Studies in Basic Sciences (IASBS) Research
Council and Iran National Science Foundation (INSF-Grant number of 95844587) for support of
this work. C. Nájera is also thankful to the Spanish Ministerio de Economia y Competitividad
24

(MINECO) (projects CTQ2013-43446-P and CTQ2014-51912-REDC), the Spanish Ministerio
de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) and Fondo
Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2016-76782-P and CTQ2016-
81797-REDC), the Generalitat Valenciana (PROMETEO2009/039 and PROMETEOII/
2014/017) and the University of Alicante.
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