Poly (methyl methacrylate)-graphene oxide supported palladium catalyst: A ligand free protocol for Suzuki and Heck coupling reaction in water medium

Article abstract of DOI:10.1080/00397911.2018.1515365

A green and efficient approach for the ligand free Suzuki–Miyaura and Mizoroki–Heck C–C cross coupling reaction using low palladium loaded Graphene oxide-polymer composite catalyst has been described. High yields, easy work-up, easy availability and handling, eco-friendly and reusability of the catalysts are the main aspects of the present method. The simplicity of the entire sequence has made the protocol meritorious as a reasonable contribution to the existing methods in the field of substituted biphenyls and olefins. The supported heterogeneous catalyst was characterized using HRTEM, ICP-AES, PXRD, XPS, TGA, and FT-IR spectroscopy.

Full text of DOI:10.1080/00397911.2018.1515365

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
Poly (methyl methacrylate)-graphene oxide
supported palladium catalyst: A ligand free
protocol for Suzuki and Heck coupling reaction in
water medium
Puja Basak & Pranab Ghosh
To cite this article: Puja Basak & Pranab Ghosh (2018): Poly (methyl methacrylate)-graphene
oxide supported palladium catalyst: A ligand free protocol for Suzuki and Heck coupling reaction in
water medium, Synthetic Communications, DOI: 10.1080/00397911.2018.1515365
To link to this article: https://doi.org/10.1080/00397911.2018.1515365
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https://doi.org/10.1080/00397911.2018.1515365
Poly (methyl methacrylate)-graphene oxide supported
palladium catalyst: A ligand free protocol for Suzuki and
Heck coupling reaction in water medium
Puja Basak and Pranab Ghosh
Department of Chemistry, University of North Bengal, Darjeeling, West Bengal, India
ABSTRACT
ARTICLE HISTORY
Received 9 May 2018
A green and efficient approach for the ligand free Suzuki–Miyaura
and Mizoroki–Heck C–C cross coupling reaction using low palladium
loaded Graphene oxide-polymer composite catalyst has been
described. High yields, easy work-up, easy availability and handling,
eco-friendly and reusability of the catalysts are the main aspects of
the present method. The simplicity of the entire sequence has made
the protocol meritorious as a reasonable contribution to the existing
methods in the field of substituted biphenyls and olefins. The sup-
ported heterogeneous catalyst was characterized using HRTEM, ICP-
AES, PXRD, XPS, TGA, and FT-IR spectroscopy.
KEYWORDS
Aqueous medium; GO-
PMMA-Pd catalyst; Heck
reaction; ligand free;
Suzuki–Miyaura coupling
GRAPHICAL ABSTRACT
Heck Coupling
•
•
•
Ligand free reaction
Water medium
Highly recyclable
Catalyst
Suzuki Coupling
GO-PMMA
Supported
Palladium Catalyst
Introduction
Heterogeneous palladium catalyzed C–C cross coupling reactions have attracted much
attention over past two decades. As a representative of this class of reaction, Suzuki and
Heck coupling are most significant because biaryl moieties and substituted olefins are
present in pharmaceuticals,[1–4] wide range of natural products such as alkaloids and
many agrochemicals and biologically active compounds.[2,5] Although homogeneous
catalyst offers excellent result, they have some drawbacks because of difficult separation
procedure that often contaminates the products. However, most of them employ differ-
ent types of ligands such as sterically hindered trialkyl phosphines, triarylphosphines,[6]
N-heterocyclic carbenes,[7] based Pd (II) complexes. Use of these ligands is unenviable
CONTACT Pranab Ghosh
pizy12@yahoo.com
Department of Chemistry, University of North Bengal, Darjeeling,
West Bengal, India.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2018 Taylor & Francis Group, LLC

2
P. BASAK AND P. GHOSH
because they are toxic and moisture sensitive. However, with growing interest towards
greener reactions, ligand free solid supported heterogeneous catalysts are in demand.
They have the advantage of enhanced synthetic efficiency and operational simpli-
city.[8–11] Previous reports include the immobilization of Pd on activated carbon,[12] pol-
ymers,[13,14] zeolites,[15] mesoporous carbon,[16] silica, alumina or titania.[17,18]
In the recent years, graphene oxide (GO) has attracted much attention owing to its
wide range of application in different fields such as fuel cells,[19] nanocomposite materi-
als,[20–23] and electronic devices.[24] GO has two dimensional layered sheets with several
oxygen containing functional groups like epoxy, hydroxy, carbonyl, carboxyl, etc.
Palladium nanoparticles supported on graphene and graphene derivatives enlarge the
surface area of the composite,[25] increasing the distance between the sheets. Utilising
this phenomenon, catalytic activity of GO-Pd/SGO-Pd,[25,26] Pd NPs supported on sin-
gle layer-GO[27] and polyamine modified GO-Pd[28] have been successfully tested in
Suzuki–Miyaura coupling. Reports regarding GO–supported palladium catalyst using
ethanol at refluxed condition,[29] and GO-supported NHC-Palladium catalyst using
aqueous-organic mixed solvents[7] are very scanty. In some cases, it is reported that,[7,29]
the activity of GO-supported palladium catalyst reduces gradually due to the agglomer-
ation and leaching of metal nanoparticles (NPs). In view of that and to overcome the
drawbacks of the previously reported protocols, we have developed a new GO-based
heterogeneous catalyst and employed it in Suzuki–Miyaura and Mizoroki–Heck reac-
tion. The reaction conditions are mild and the catalyst can be recycled for five runs
without significant loss in its catalytic activity.
Preliminary studies on polymer supported GO has revealed significant increase in
mechanical and thermal properties of the composite.[30–33] Driven by this fact, the idea
of a new solid support, which allows better stability, easy recovery of products and sim-
ple separation procedure is hypothesized. Poly (methyl methacrylate) [PMMA] is a non-
conductive polymer and its composite with GO enhances the thermal stability of the
material. Based on the above perspective, our present explorative work involves the
deposition of Pd NPs on GO-PMMA composite through in situ polymerization of
MMA. Wielded by the environmental concerns, water is selected as solvent instead of
hazardous solvents such as DMF, DMA, NMP, etc. Utility of GO enhances the thermal
stability of poly (methyl methacrylate)[34,35] and Pd NPs are strongly immobilized in
between the layers of graphene oxide–PMMA composite.[24,29] To the best of our know-
ledge, GO-PMMA supported Pd catalyst has not been employed in Suzuki and Heck
coupling reactions. Simpler reaction conditions, ligand free protocol, low Pd content
and tolerance to wide range of functional groups are the salient features of our work.
Results and discussion
The morphology of the catalyst (GO-PMMA-Pd) was analyzed by transmission electron
microscope (TEM). The micrograph and particle size distribution curve of in situ pre-
pared GO-PMMA-Pd catalyst is represented in Figure 1. The TEM images show the
mono dispersed palladium without agglomeration on the GO-PMMA-sheet during in
situ polymerization of MMA. The average size of the Pd NPs has been determined from
the TEM images and was found to be around 4.8 nm.

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3
Figure 1. TEM image of GO-PMMA-Pd composite catalyst (a) at 50 nm (b) at 20 nm (c) at 2 nm (d)
Particle size distribution curve of GO-PMMA-Pd catalyst.
The catalyst life is a factor that can control the economic viability of industrial proc-
esses and as a consequence high thermal resistance of a catalyst support is found to be
suitable for different kinds of thermal reaction.[36]
Thermogravimetric Analysis (TGA) of the solid support has been analyzed for several
samples with different wt % of GO loading as shown in Figure 2. It is very interesting
to observe that composite with the lowest wt % of GO exhibited maximum thermal sta-
bility (Fig. 2).
The catalyst was subjected to powder X-ray diffraction (XRD) for composition ana-
lysis (Fig. 3). Three sharp peaks at around 2h ¼ 40.1ꢀ, 46.6ꢀ and 68.9ꢀ represents the
crystalline planes (111), (200) and (220), respectively, in fcc structure of Pd.[29] However
the intensity of (111) plane is higher than (200) and (220) plane. The absence of strong
[37]
GO peak at 2h ¼ 10.63ꢀ
and the appearance of characteristic broad PMMA peak at
2h ¼ 14.8ꢀ indicated the formation of GO-polymer composite. The FTIR spectrum of
GO has a peak at 1735 cmꢁ1 which is assigned to the carbonyl stretching frequency.
The FT-IR peak of PMMA at 1148 cmꢁ1 is associated with the stretching vibration of
the C–O bond in the C–O–C moiety, whereas the peak at 1731 cmꢁ1 is due to the
acrylate carbonyl groups. FT-IR spectrum (Fig. 4) revealed that the resultant GO-
PMMA-Pd composite catalyst contained several functional groups like –OH
(3454 cmꢁ1) and C=O (1731 cmꢁ1). Therefore, it has a strong tendency to readily

4
P. BASAK AND P. GHOSH
Figure 2. TGA results of (B) 2 wt% (C) 5 wt% (D) 10 wt% GO in PMMA.
Figure 3. XRD pattern of GO-PMMA-Pd composite catalyst.
interact with metal ions by hydroxyl and carboxyl group. It is considered that the bond
between Pd and GO-PMMA can be formed through some physical/chemical interac-
tions such as Vander Waals force, H-bonding and other bonds.[38] The shift of other
stretching frequencies also points towards the association of PMMA with GO (Fig. 4).
Furthermore, a hump obtained at around 2h ¼ 23ꢀsuggests the presence of reduced gra-
phene oxide (RGO).[39] Hence, it can be concluded that a small amount of GO has
been converted into RGO when HCOOH was employed. GO-PMMA-Pd catalyst was
further characterized by XPS, as shown in Figure 5. High-resolution XPS spectrum was
corrected with reference to the carbon 1 s peak at 284.8 eV shown in Figure 5(b).

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5
(f)
(e)
(d)
(c)
(b)
(a)
4000
3200
2400
1600
800
−1
Wavenumber (cm
)
Figure 4. Comparison of FT-IR spectra of (a) GO (b) GO-PMMA (c) GO-PMMA-Pd (d) PMMA-Pd (e)
PMMA and (f) recycled catalyst after fifth run.
The binding energies of Pd 3d at 335.87 and 341.2 eV for GO-PMMA-Pd corresponded
to the Pd0 Pd 3d5/2 and Pd 3d3/2, respectively. Thus, the presence of metallic Pd in the
composite is confirmed (Fig. 5(c)).
Leaching of metal from the heterogeneous GO-PMMA support was examined by hot
filtration test as described in the literature.[40] After 1 h completion of reaction, the
reaction mixture was filtered to separate out the catalyst and HPLC was carried out with
the obtained filtrate (38% conversion). The ICP-AES analysis of the filtrate showed the
absence of any palladium. The filtrate was then heated for another 4 h at 90 ꢀC without the
addition of catalyst and the corresponding HPLC pattern (Fig. 6) did not show any
noticeable conversion which implied that metals are not getting leached from the solid
GO-PMMA support during first 1 h of the reaction.
The Pd content was found to be 5.559 wt% in this heterogeneous catalyst. The recyc-
lability of the catalyst was tested for Suzuki coupling reaction and the catalyst was
recyclable for five consecutive runs without significant drop in activity. The sudden
drop in Pd content ( Fig. 7) after the fifth run may be attributed to the leaching of Pd
from the catalyst. The development of recoverable catalyst is one of the indispensable
principles of the green synthetic organic chemistry and the key purpose of this study
was to place a recyclable catalyst for Suzuki and Heck reaction in aqueous medium.
Initially, for screening the reaction, phenylboronic acid and 4-iodo anisole has been
chosen as the model substrates in presence of GO-PMMA-Pd catalyst. The favorable
condition of the reaction was achieved by varying the parameters such as catalyst load-
ing, solvent, time, base and temperature. Finally the protocol was optimized by using
water as solvent, K2CO3 as base and catalyst loading (0.3 mol % Pd) in 6 mg of

6
P. BASAK AND P. GHOSH
(a)
Pd3d
C1s
O1s
1000
800
600
400
200
Binding Energy (eV)
(b) C1s
(c) Pd3d
3d
5/2
3d
3/2
350
345
340
335
330
325
292
288
284
280
276
Binding Energy (eV)
Binding Energy (eV)
Figure 5. (a) Full-range XPS spectrum of GO-PMMA-Pd catalyst. C 1s peak at 284.8 eV shown in (b).
In (c) the binding energies of Pd 3d at 335.87 and 341.2 eV for GO-PMMA-Pd corresponded to the
Pd0 Pd 3d5/2 and Pd 3d3/2, respectively.
Figure 6. Comparison of normal time profile with hot filtration test. Conversions ( 2%) at different
time intervals for each plot were measured by HPLC.

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7
100
80
60
40
20
0
90
88
87
86
81
68
1st
2nd
3rd
4th
5th
6th
Number of runs
Figure 7. Recycling efficiencies of GO-PMMA-Pd catalyst for Suzuki coupling reaction.
Table 1. Optimization of reaction parameters for Suzuki reaction based on the result of the following combination in
the protocola.
Entry
Solvent
Base
Pd loading (mol% )
Additive
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
DMF
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
Cs2CO3
Et3N
0.1
0.1
0.2
0.2
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.5
Bu4NBr
Bu4NBr
Bu4NBr
Bu4NBr
SDS
Bu4NBr
Bu4NBr
Bu4NBr
Bu4NBr
Bu4NBr
CTAB
1
2
3
3
4
4
6
6
6
4
6
4
24
12
42
29
63
58
72
90
76
75
78
62
72
52
25c
86d
DMSO
Water
Ethanol
Water
Water
Water
Water
Water
Water
Water
Water
Water
Water
9
10
11
12
13
14
KOH
K2CO3
K2CO3
K2CO3
K2CO3
TMAI
Bu4NBr
Bu4NBr
aReaction of 4-Iodo anisole (1 mmol), Phenyl boronic acid (1.5 mmol), Pd loading (0.3 mol%), K2CO3 (1 mmol), TBAB
(10 mol%), water (2 mL) at 90 ꢀC;
bIsolated yields.
cRoom temperature reaction;
dTemp of the reaction 100 ꢀC.
GO-PMMA-Pd catalyst at 90 ꢀC (Table 1). In order to enhance the yield of 4-methoxy-
1,10 biphenyl in water, different surfactants were employed in the study (Table 1). It is
established that the yield of the product can be improved by increasing the reaction
time. We started increasing the reaction time by keeping all parameters similar and
found that the best yield is achieved in 4 h of reaction (Table 1, entry 6). However,
ortho-substituted compounds require longer reaction time.
The synthetic efficacy of this catalyst in water mediated Suzuki coupling reaction was
conducted with a number of different aryl halides and arylboronic acids under optimized
condition (Table 2, entries 1–16). The electron withdrawing aryl iodides and bromides
gave excellent yields of corresponding products (entries 3, 6 and 8). Although relatively
longer reaction time was required for electron donating aryl iodides and bromides but each
of them offered an excellent yield of products (entries 1–2 and 4–5). The aryl chlorides
gave only trace amount of the corresponding product even after 24 h of exertion of
reaction. The arylboronic acids with methoxy, methyl, nitro groups were rapidly converted
to their corresponding products at high to moderate yield at 90 ꢀC as shown in Table 2
(entries 9, 15 and 16).

8
P. BASAK AND P. GHOSH
Table 2. GO-PMMA-Pd catalyzed Suzuki reaction of different aryl halides with phenyl boronic acida.
GO-PMMA-Pd catalyst
X
(HO)2B
+
R1
R2
R2
water ,K2CO3, TBAB
90OC
R1
Time
(h)
Yieldb
(%)
Entry
Aryl halide
Boronic acid
Products
OCH3
B(OH)2
1.
OCH3
4
90
I
OCH3
B(OH)2
B(OH)2
2.
3.
4
2
88
92
OCH3
I
NO2
NO2
CH3
I
CH3
B(OH)2
B(OH)2
B(OH)2
4.
5.
6.
6
6
86
84
93
I
CH3
CH3
Br
COCH3
COCH3
1.5
Br
OCH3
CH3
B(OH)2
OCH3
CH3
7.
4
85
Br
NO2
B(OH)2
8.
3
89
NO2
Br
continued

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9
Table 2. Continued.
B(OH)2
CH3
9.
H3C
OCH3
4
86
I
OCH3
B(OH)2
10.
6
_
58
S
Br
S
OCH3
B(OH)2
11.
12.
No reaction
Nil
N
I
CH3
B(OH)2
CH3
6
79
Br
Cl
B(OH)2
B(OH)2
Br
Br
13.
14.
15.
No reaction
_
Nil
35c
88
24
4
4
CH3
16.
71
NO2
aReaction of aryl halide (1 mmol), Phenyl boronic acid (1.5 mmol), palladium loading (0.3 mol%), K2CO3 (1 mmol), TBAB
(10 mol%), water (2 mL) at 90 ꢀC.
bIsolated yields.
cReaction temperature 120 ꢀC.
The above success in Suzuki coupling reaction prompted us to look for such expect-
ancy in Heck coupling reaction too. The Heck reaction was optimized by varying the
reaction parameters temperature, solvent, base, catalyst loading (Table 3). In that
instance, 4-iodo anisole was successfully coupled with methyl acrylate in presence of
TBAB and 0.2 mol% Pd in GO-PMMA-Pd catalyst at 100 ꢀC. All types of aryl halides

10
P. BASAK AND P. GHOSH
Table 3. Optimization of reaction parameters of Heck reactiona.
Entry
Solvent
Base
Temp (ꢀC)
Pd-loading (mol%)
Time (h)
Yield (%)b
1
2
3
4
5
6
DMF
K2CO3
K2CO3
Et3Nd
K2CO3
K2CO3
K2CO3
120
100
100
100
80
0.1
0.1
0.2
0.2
0.3
0.3
4
5
5
4
5
75c
72
80
Water
Water
Water
Water
Water
85
78
Rt
24
25e
aReaction of 4-Iodo anisole(1 mmol), methyl acrylate (2 mmol), Pd loading (0.2 mol%), K2CO3 (1 mmol), TBAB (10 mol%),
water 3 mL.
bIsolated yields.
csolvent was DMF.
dtriethyl amine was used as base.
eroom temperature.
gave good to excellent yield, which indicates the high efficiency of this heterogeneous
catalyst (Table 4) in Heck coupling too.
Figure 7 represents the recyclability of the GO-PMMA-Pd catalyst for Suzuki cou-
pling reaction upto the sixth run. The reduction of yield after fifth run could be due to
the leaching of Pd NPs from GO-PMMA surface. The palladium content after fifth run
was confirmed by ICP-AES and it was found to be 1.357 wt%. However, when the reac-
tion was performed with only PMMA-Pd0, a drastic change in yield was observed from
88% to 56% in second run. This observation clearly indicated that presence of GO in
the composite plays a vital role to improve the catalytic ability of GO-PMMA-
Pd system.
Experimental
Materials and physical measurements
Palladium (II) acetate 99.98% was purchased from Sigma Aldrich. Graphite powder,
H2O2 (solution 30%), 98.5% pure methyl methacrylate were purchased from commercial
supplier. The morphology of the catalyst (GO-PMMA-Pd) was analyzed by TEM,
(Model: JEM-2100, accelerating voltages 60–200 KV in 50 V steps; resolution: 1.9 Å to
1.4 Å). Inductively coupled plasma spectroscopy (ICP) was analyzed on ARCOS,
Simultaneous ICP spectrometer (SPECTRO analytical instruments GmbH, Germany).
Powder XRD data and X-ray photoelectron spectroscopy (XPS) was obtained from
Bruker D8 Advanced X-ray Powder Diffractometer (Cu Ka radiation, k ¼ 1.54 Å) and
an XPS instrument (Omicron: Serial no. 0571) respectively. NMR spectra were taken in
1
CDCl3 using a Bruker AV–300 spectrometer operating for H at 300 MHz and for 13C
at 75 MHz. Splitting patterns of protons were described as s (singlet), d (doublet), t
(triplet), br (broad) and m (multiplet). Chemical shifts were reported in parts per mil-
lion (ppm) relative to TMS as internal standard.
General procedure for preparation of GO-PMMA-supported Pd catalyst
Initially for the preparation of catalyst 20 mg of GO was suspended in 20 mL of toluene.
The slurry was then dispersed through ultrasonication for 60 min. After ultrasonication
methyl methacrylate was injected to a well dispersed solution of GO. Benzoyl peroxide

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Table 4. Reaction of aryl halides with different vinyl compoundsa.
Y
X
GO-PMMA-Pd catalyst
R
R
+
Y
water, K2CO3,TBAB
°
100 C
Time
(h)
Yieldb
Entry
Aryl halides
Olefins
Product
(%)
O
I
I
I
OCH3
O
1
4
4
6
85
O
H3CO
H3CO
H3CO
H3CO
O
O
O
2
3
83
84
O
O
H3CO
O
O
O
O
H3CO
O
O
I
OCH3
OCH3
4
4
88
O
O
NO2
NO2
Br
5
6
5
5
90
79
O
I
H3CO
H3CO
I
7
8
4
4
80
84
Br
H3COC
H3COC
aReaction of aryl halide (1 mmol), vinyl compound (2 mmol), GO-PMMA-Pd catalyst (0.2 mol%), K2CO3 (1 mmol), TBAB
(10 mol%), water 3 mL.
bIsolated yields.

12
P. BASAK AND P. GHOSH
Scheme 1. Preparation of GO-PMMA-Pd catalyst.
(BZP, 0.1 mol%) was added to initiate the polymerization of methyl methacrylate
(MMA). The resulting mixture was then stirred well at 90 ꢀC for 4 h. The temp of the
solution was maintained at 90 ꢀC. Stirring was continued for another 3 h followed by
the addition of 40 mg Pd(OAc)2 and 100 mg of HCOOH as shown in Scheme 1. The
dark brown precipitate instantly turned into black after the addition of HCOOH. The
obtained residue was washed several times with water and residual solvent was shuffled
off by rotary evaporator, and dried at 60 ꢀC.
Procedure for cross coupling of 4-iodo anisole and phenyl boronic acid using
GO-PMMA-Pd catalyst
A 25 mL RB was charged with 4-iodo anisole (1.0 mmol), phenylboronic acid
(1.5 mmol), GO-PMMA-Pd catalyst (0.3 mol % Pd), K2CO3 (1 mmol), TBAB (10 mol %)
and 2 mL water. The mixture was allowed to stir at 90 ꢀC for an appropriate time
(Table 1) and the extent of the reaction was monitored by thin layer chromatography
(TLC). After the completion of the reaction, the reaction mixture was extracted by ethyl
acetate (2 ꢂ 25 ml) and washed with water repeatedly. The catalyst was filtered off and
washed several times with ether and water (1:1) until no significant product was
obtained in the wash. The recovered catalyst was reused for the next coupling experi-
ment. The reaction mixture was dried over anhydrous Na2SO4, concentrated in vacuum
and purified by column chromatography on silica gel 60–120 mesh using petroleum
ether as eluent to obtain pure product. The catalyst recovered after fifth run was sub-
1
jected to ICP-AES for Pd content analysis. The isolated products were analyzed by H
NMR and 13C NMR spectroscopy.
1
4-methoxy-1,10 biphenyl[41]: H NMR (CDCl3, 300 MHz) d 3.85 (s, 3H), 6.98 (d, 2 H,
J ¼ 6.9 Hz), 7.238–7.319 (1 H, m), 7.397 (d, 2 H, J ¼ 7.8 Hz), 7.511–7.564 (m, 4 H,
J ¼ 8.7 Hz); 13C NMR
d
55.37, 114.22, 126.68, 126.76, 128.18, 128.75,
133.80, 140.85,159.16.
General procedures for the heck coupling reactions
A mixture of 4-iodo anisole (1 mmol), methyl acrylate (2 mmol), GO-PMMA-Pd catalyst
(0.2 mol % Pd), K2CO3 (1 mmol), TBAB (10 mol %) and 3 ml water was stirred under
100 ꢀC. The reaction took significant time for completion (Table 3) and the progress of
the reaction was monitored by TLC. After completion, the reaction mixture was
extracted with ethyl acetate and washed with water repeatedly. The combined organic
mixture was dried over anhydrous NaSO4 and purified by column chromatography
using petroleum ether/ethyl acetate as eluent to afford pure product. The catalyst was
separated and washed for several times with ether and water. The recovered catalyst was

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13
1
used in next cycles and the isolated products were characterized by H and 13C NMR
spectroscopy.
(E)-methyl 3-(4-methoxyphenyl) acrylate[42]
126.57, 130.13, 144.31, 161.11, 166.91.
:
13C NMR d 51.27, 55.29, 114.33, 115.03,
Conclusion
A greener protocol using ligand free GO-PMMA-Pd catalyst is proposed. The prepared
catalyst was characterized by different spectroscopic and microscopic techniques. The
newly made catalyst effectively generates different C–C cross coupled product even at a
very low Pd content in high yields at optimal condition. The simple operational proced-
ure, easy removal of catalyst, reusability of the catalyst and environmentally benign pro-
cess are the most significant and outwit factors of our proposed scheme in comparison
to the existing protocols.
Acknowledgments
The authors thank IIT Bombay for ICP-AES analysis, IACS Kolkata for PXRD analysis and XPS
analysis, NEHU (SAIF) for TEM analysis.
Funding
One of the authors (PB) is thankful to council of scientific and industrial research (CSIR), NEW
DELHI, INDIA, New Delhi for financial support.
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