Fe3O4 supported Pd(0) nanoparticles catalyzed alkoxycarbonylation of aryl halides

Article abstract of DOI:10.1016/j.molcata.2013.01.002

This paper describes the simple and efficient method for the alkoxycarbonylation of aryl iodides using magnetically recoverable Pd/Fe ₃O₄ as the catalyst under atmospheric pressure of carbon monoxide. Various aryl iodides on alkoxycarbonylation with alcohols gave the corresponding products in good to excellent yields. The catalyst is completely recoverable with the simple application of an external magnetic field, and the efficiency of the catalyst remains unaltered even after five cycles.

Full text of DOI:10.1016/j.molcata.2013.01.002

Journal of Molecular Catalysis A: Chemical 370 (2013) 205–209
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Catalysis A: Chemical
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Review
Fe3O4 supported Pd(0) nanoparticles catalyzed alkoxycarbonylation
of aryl halides
Aviraboina Siva Prasada,b,∗, Bollikonda Satyanarayanaa
a Process Research and Development, CTO-1, Dr. Reddy’s Laboratories Ltd., Bollaram, Hyderabad 502325, Andhra Pradesh, India
b Institute of Science and Technology, Jawaharlal Nehru Technological University, Kukatpally, Hyderabad 500072, Andhra Pradesh, India
a r t i c l e i n f o
a b s t r a c t
Article history:
This paper describes the simple and efficient method for the alkoxycarbonylation of aryl iodides using
magnetically recoverable Pd/Fe3O4 as the catalyst under atmospheric pressure of carbon monoxide.
Various aryl iodides on alkoxycarbonylation with alcohols gave the corresponding products in good
to excellent yields. The catalyst is completely recoverable with the simple application of an external
magnetic field, and the efficiency of the catalyst remains unaltered even after five cycles.
© 2013 Elsevier B.V. All rights reserved.
Received 6 July 2012
Received in revised form
22 December 2012
Accepted 2 January 2013
Available online 23 January 2013
Keywords:
Alkoxycarbonylation
Aryl iodides
Magnetically recoverable Pd/Fe3O4
Carbon monoxide
Contents
1.
2.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
2.1.
2.2.
2.3.
2.4.
2.5.
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Preparation of the Pd/Fe3O4 catalyst [31] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Typical experimental procedure for the alkoxycarbonylation of aryl iodides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Reuse of catalyst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Spectroscopic data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
2.5.1.
2.5.2.
2.5.3.
2.5.4.
2.5.5.
Butyl 4-methoxybenzoate (Table 2, entry 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
Phenyl 4-methoxybenzoate (Table 2, entry 4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Butyl 2-methylbenzoate (Table 3, entry 3). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Butyl 4-chlorobenzoate (Table 3, entry 6). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Butyl 4-acetylbenzoate (Table 3, entry 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
3.
4.
Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
1. Introduction
[1–4]. “Classic” syntheses of aromatic esters or amides generally
require a carboxylic acid precursor. Alternatively, aryl carboxylic
acid derivatives can be prepared through palladium-catalyzed car-
bonylation of the corresponding aryl halides in the presence of a
suitable nucleophile [5–8,2]. Advantages of this method include the
broad availability of substrates and the high tolerance of palladium
catalysts against a variety of functional groups. Therefore, this route
has become a useful tool for the preparation of substituted benzoic
acid derivatives.
The introduction of carbonyl group into arenes using carbonyla-
tion reactions is an interesting method among the array of catalytic
conversions of aryl halides performed by palladium complexes
∗
Corresponding author at: Process Research and Development, CTO-1,
Dr. Reddy’s Laboratories Ltd., Bollaram, Hyderabad 502325, Andhra Pradesh, India.
Tel.: +91 8458279173; fax: +91 40 23095438.
Despite its well-known toxicity, CO is a very valuable and
convenient reagent for a variety of reasons: (i) it is thermally
E-mail addresses: avirasp006@gmail.com,
avirasp@drreddys.com (A. Siva Prasad).
1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.01.002

206
A. Siva Prasad, B. Satyanarayana / Journal of Molecular Catalysis A: Chemical 370 (2013) 205–209
Scheme 1.
quite stable and yet chemically reactive and (ii) it is an inexpen-
sive carbon source, which can be incorporated into a variety of
organic compounds in its entirety without producing any unde-
sirable byproduct. Since its toxicity problem can satisfactorily be
dealt with in many instances, CO can be considered an environmen-
tally friendly and convenient carbon source in an overall sense [9].
Consequently, considerable effort has been directed to the devel-
opment of efficient and selective methods for the carbonylation
using CO. Generally the phosphine ligands are used to complex
and activate the palladium species, and excellent results have
been reported for the palladium-catalyzed carbonylation reaction
[10–13]. The use of such ligands is undesirable because of their
toxicity and air as well as moisture sensitive with conversion to,
for example, phosphine oxide species. However, few phosphine-
free palladium catalysts have been used for the carbonylation of
aryl halides under high pressure of carbon monoxide [14–17].
Despite the synthetic elegance the non-reusability of the pre-
cious palladium precludes wide synthetic applications in the
industry. In view of the above, it is desirable to develop a ligand-free
and reusable catalytic system for the carbonylation. Heterogeneous
catalysis is particularly attractive as it allows the production and
ready separation of large quantities of products with the use of
a small amount of catalyst. However, heterogenized catalyst gen-
erally requires tedious preparation and/or separation procedures
and there is a need to find new materials with speciality properties
such as magnetic in order to overcome these limitations. Magnetic
nanoparticles are a class of nanostructured materials of current
interest, due largely to their advanced technological and medical
applications, envisioned or realized [18–21]. Among the various
magnetic nanoparticles under investigation, Fe3O4 nanoparticles
are arguably the most extensively studied [22–24] and recently
emerged as promising supports for immobilization metal nanopar-
ticles. Fe3O4-supported metal catalysts can be separated from
the reaction medium by an external permanent magnet [25–29].
Recently Palladium nanoparticles supported on Fe3O4 have been
the subject of interest of several groups and widely used in a variety
of organic reactions [30–33].
of all compounds were recorded on a PerkinElmer, Spectrum GX
FTIR spectrometer using KBr pellet method. The IR values are
reported in reciprocal centimeters (cm−1). The 1H and 13C NMR
spectra were recorded on a Bruker Avance 300 MHz spectrometer.
Chemical shifts (d) are reported in ppm, using TMS (d = 0) as an
internal standard in CDCl3. ESI mass spectra were recorded on a
Finnigan LCQ Advantagemax spectrometer. EI mass spectra were
recorded on a GC–MS QP2010 Plus (Shimadzu).
2.2. Preparation of the Pd/Fe3O4 catalyst [31]
1 g of dopamine-functionalized Fe3O4 nanoparticles were dis-
persed in water and NaPdCl4 solution in water was added to
the mixture to get 10 wt% of Pd. Diluted solution of hydrazine
monohydrate was added drop wise to adjust the pH to 9. The reac-
tion mixture was stirred overnight at room temperature and then
allowed to settle. The product Pd/Fe3O4 was washed several times
with water, centrifuged and dried at room temperature.
2.3. Typical experimental procedure for the alkoxycarbonylation
of aryl iodides
A solution of the aryl iodide (1 mmol) and the alcohol (2 equiv.),
K3PO4 (1.5 equiv.), Pd/Fe3O4 (1.5 mol% of Pd) in DMF (3 mL) was
placed in a 10 mL reaction flask and fitted with condenser and car-
bon monoxide baloon. The resultant solution was stirred under
carbon monoxide atmosphere at 80 ◦C temperature for 10 h. After
completion of the reaction (monitored by TLC) the reaction flask
was cooled to room temperature and carbon monoxide balloon
was removed. The catalyst was easily separated from the reaction
mixture with an external magnet. After removing the solvent from
the reaction mixture, the crude material was chromatographed on
silica gel using hexane–ethyl acetate mixture as eluent.
2.4. Reuse of catalyst
In the present work, we report our investigations on the appli-
cation of Fe3O4 supported Pd(0) nanoparticles (Pd/Fe3O4) for the
carbonylation of aryl halides with oxygen nucleophiles [34–36]
using atmospheric pressure of carbon monoxide under ligand free
conditions (Scheme 1).
After completion of the reaction the catalyst was recovered by
using external magnet and washed several times with ethyl acetate
and then ether and dried for further reuse. The catalyst showed
consistent activity for five cycles.
2.5. Spectroscopic data
2. Experimental
All the products reported here are known compounds and the
spectroscopic data was matched literature values. Data for the some
of the compounds given below.
2.1. General
All chemicals were purchased from Sigma–Aldrich and S.D. Fine
Chemicals, Pvt. Ltd. India and used as received. ACME silica gel
(100–200 mesh) was used for column chromatography and TLC
was performed on Merck precoated silica gel 60 F254 plates. All
the other chemicals and solvents were obtained from commercial
sources and purified using standard methods. The morphology, size
and shape distribution of the Pd nanoparticles were recorded using
TECNAI FE12 TEM instrument operating at 120 kV. The IR spectra
2.5.1. Butyl 4-methoxybenzoate (Table 2, entry 2)
IR (KBr): 2960, 1719, 1274, 1109 cm−1 1H NMR (300 MHz,
.
CDCl3): ı 0.99 (t, 3H, J = 7.4 Hz), 1.45–1.54 (m, 2H), 1.69–1.79 (m,
2H), 3.85 (s, 3H), 4.27 (t, 2H, J = 6.6 Hz), 6.87 (d, 2H, J = 8.8 Hz), 7.95
(d, 1H, J = 8.8 Hz). 13C NMR (75 MHz, CDCl3): 13.6, 19.1, 30.7, 55.2,
64.3, 113.4, 122.8, 131.3, 163.1, 166.2. ESI MS (m/z): 209 (M+H).

A. Siva Prasad, B. Satyanarayana / Journal of Molecular Catalysis A: Chemical 370 (2013) 205–209
207
Fig. 1. TEM images of Pd/Fe3O4 nanoparticles: (a) fresh catalyst and (b) catalyst after five cycles.
2.5.2. Phenyl 4-methoxybenzoate (Table 2, entry 4)
IR (KBr): 2910, 1712, 1606, 1168, 1029, 770 cm−1
3. Results and discussion
.
1H NMR
(300 MHz, CDCl3): ı 3.89 (s, 3H), 6.94 (d, 2H, J = 9.1 Hz), 7.15–7.26
(m, 3H), 7.36–7.42 (m, 2H), 8.13 (d, 2H, J = 8.3 Hz). 13C NMR (75 MHz,
CDCl3): 55.5, 113.8, 121.7, 125.6, 129.4, 132.2, 151.0, 163.8, 164.8.
ESI MS (m/z): 229 (M+H).
The amount of palladium in the prepared Pd/Fe3O4 catalyst was
determined with an inductively coupled plasma, atomic emission
spectroscopy (ICPAES) instrument and palladium content was mea-
sured as 0.14 mmol g−1. The TEM images of both the fresh and used
catalyst, it is seen that the average size of Fe3O4 nanoparticles is
in the range of 20–25 nm in diameter and palladium nanoparticles
of about 2–3 nm and are dispersed on Fe3O4 nanoparticles (Fig. 1).
Furthermore, the TEM image (Fig 1(b)) clearly confirms no change
in the morphology even after five cycles.
In an endeavor to identify the best catalytic system for the
alkoxycarbonylation various bases in combination with different
solvents were investigated using 4-iodoanisole as aryl halide and n-
butanol as the nucleophile and the results are presented in Table 1.
The bases used in this study include NEt3, K2CO3, Na2CO3, K3PO4
and Cs2CO3, out of which K3PO4 and Cs2CO3 are equally effective
and gave the product in good yield. Whereas, K2CO3, Na2CO3 gave
the product in moderate yield (Table 1, entries 2–5). However, by
maintaining carbon monoxide 0.5 kg/cm2 (0.48 atm of CO) pres-
sure in the presence triethylamine as the base gave the product in
good yield (Table 1, entry 1). Among the different solvents used
N,N-dimethylformamide (DMF) proved to be the good solvent and
the reactions with other solvents such as DMA, DMSO and Toluene
generate the desired product in moderate to low yields (Table 1,
entries 6–8).
2.5.3. Butyl 2-methylbenzoate (Table 3, entry 3)
IR (KBr): 2985, 1722, 1259, 1085, 831 cm−1 1H NMR (300 MHz,
.
CDCl3): ı 0.99 (t, 3H, J = 6.8 Hz), 1.48–1.56 (m, 2H), 1.72–1.78 (m,
2H), 2.59 (s, 3H), 4.28 (t, 3H, J = 6.4 Hz), 7.18–7.22 (m, 2H), 7.35 (t,
1H, J = 7.5 Hz), 7.88 (d, 1H, J = 7.5 Hz). 13C NMR (75 MHz, CDCl3):
13.6, 19.2, 21.6, 30.6, 64.4, 125.5, 129.8, 130.3, 131.5, 131.6, 139.8,
167.6. EI MS (m/z): 198 (M+).
2.5.4. Butyl 4-chlorobenzoate (Table 3, entry 6)
IR (KBr): 2943, 1712, 1606, 1261, 1023, 776 cm−1 1H NMR
.
(300 MHz, CDCl3): ı 0.99 (t, 3H, J = 6.8 Hz), 1.46–1.55 (m, 2H),
1.71–1.81 (m, 2H), 4.33 (t, 2H, J = 6.0 Hz), 7.29 (ddd, J = 1.5 Hz, 7.5 Hz,
14.3 Hz), 7.36–7.45 (m, 2H), 7.79 (dd, 1H, J = 1.5 Hz, 7.5 Hz). 13C NMR
(75 MHz, CDCl3): 13.5, 19.1, 30.4, 65.2, 126.3, 130.3, 130.8, 131.1,
132.2, 133.3, 165.6. ESI MS (m/z): 213 (M+H).
2.5.5. Butyl 4-acetylbenzoate (Table 3, entry 9)
Proposed mechanism for the Pd/Fe3O4-catalyzed carbonylation
of aryl halides under ambient pressure of CO (Fig. 2).
IR (KBr): 2973, 1703, 1689, 1278, 989 cm−1 1H NMR (300 MHz,
.
CDCl3): ı 0.99 (t, 3H, J = 7.5 Hz), 1.43–1.56 (m, 2H), 1.73–1.82 (m,
2H), 2.62 (s, 3H), 4.35 (t, 2H, J = 6.8 Hz), 7.97 (d, 2H, J = 8.3 Hz), 8.10 (d,
2H, J = 8.3 Hz). 13C NMR (75 MHz, CDCl3): 13.7, 19.2, 26.8, 30.6, 65.2,
128.1, 129.7, 134.2, 140.1, 165.7, 197.5. ESI MS (m/z): 221 (M+H).
The best reaction conditions found on the model substrates
were applied to different alcohols to obtain the corresponding
ester derivatives as shown in Table 2. Isopropanol, n-butanol and
t-butanol gave the product in moderate to good yields (Table 2,
Table 1
Optimization of reaction conditions for the Pd/Fe3O4-catalyzed carbonylation of aryl halides under ambient pressure of CO.a
O
Pd/Fe3O4
I
CO (baloon)
O
HO
+
base, solvent,
H3CO
H3CO
80 o
C
.
Entry
Base
Solvent
Yield (%)
1
2
3
4
5
6
7
8
NEt3
DMF
DMF
DMF
DMF
82
60
55
83
85
68
75
27
K2CO3
Na2CO3
K3PO4
Cs2CO3
K3PO4
K3PO4
K3PO4
DMF
DMSO
DMA
Toluene
a
Reaction conditions: 4-bromoanisole (1 mmol), n-butanol (2 equiv.), base (1.5 equiv.), Pd/Fe3O4 (1.5 mol%), solvent (3 mL) stirred at 80 ◦C, under CO atmosphere for 10 h.

208
A. Siva Prasad, B. Satyanarayana / Journal of Molecular Catalysis A: Chemical 370 (2013) 205–209
Table 2
Generalization of Pd/Fe3O4-catalyzed alkoxycarbonylation reaction using different alcohols under ambient pressure of CO.a
O
Pd/Fe3O4
I
R
CO (baloon)
O
+
R OH
K3PO4, DMF
H3CO
H3CO
o
80 C, 10 h
.
Entry
R-OH
Product
Yield (%)b
O
O
O
O
O
iPr
nBu
tBu
Ph
O
O
O
O
O
1
2
3
4
(CH3)2CHOH
75
H3CO
C4H9OH
85
70
91
95
H3CO
H3CO
H3CO
H3CO
(CH3)3COH
OH
Ph
OH
5
a
Reaction conditions: 4-iodoanisole (1 mmol), alcohol (isopropanol (10 equiv.), n-butanol, t-butanol (2 equiv.), phenol, p-methyl benzyl alcohol (1.2 equiv.)), Pd/Fe3O4
(1.5 mol% of Pd), base (1.5 equiv.), DMF (3 mL) and reaction stirred at 80 ◦C, under CO atmosphere for 10 h.
b
Isolated yield.
entries 1–3). Whereas, phenol and benzyl alcohols gave esters in
very good yield (Table 2, entries 4 and 5).
Encouraged by these results, we next investigated the scope of
the reaction with respect to the aryl iodide substrate. We tested
a variety of substituted aryl iodides under the optimized reaction
conditions with n-butanol as a oxygen nucleophile. Various aryl
iodides, including the deactivated aryl iodides, were readily con-
verted to the corresponding coupled products in excellent yields
as shown in Table 3. Unsubstituted as well as 4-methyl, 4-methoxy
substituted iodobenzenes underwent smooth reaction with good
yields when compared to 2-methyl-iodobenzene (Table 3, entries
80
60
40
20
0
First
Second
Third
Fourth
Fifth
No.of Cycles
Fig. 3. Recovery and reuse of Pd/Fe3O4 catalyst for the alkoxycarbonylation of
iodobenzene with n-butanol as nucleophile under ambient pressure of CO (reac-
tion conditions: iodobenzene (1 mmol), n-butanol (2 equiv.), Pd/Fe3O4 (1.5 mol% of
Pd), base (1.5 equiv.), DMF (3 mL) and reaction stirred at 80 ◦C, under CO atmosphere
for 10 h. Isolated yield).
Fig. 2. Proposed mechanism for the Pd/Fe3O4-catalyzed carbonylation.

A. Siva Prasad, B. Satyanarayana / Journal of Molecular Catalysis A: Chemical 370 (2013) 205–209
209
Table 3
and reused for five times without significant loss of catalytic activ-
ity. Inductively coupled plasma (ICP) mass-spectrometric analysis
of the filtrate from the reaction mixture demonstrated that the pal-
ladium metal hardly leached into the solution within the limits of
the detector (1 ppm), thus suggesting that the present alkoxycar-
bonylation reaction proceeded by heterogeneous catalysis.
Pd/Fe3O4-catalyzed alkoxycarbonylation of different aryl iodides with n-butanol as
nucleophile under ambient pressure of CO.a
Entry
Aryl halide
Product
Yield (%)b
90
O
O
I
nBu
1
O
O
4. Conclusion
I
In conclusion, we have developed a simple and efficient method
for the alkoxycarbonylation of aryl iodides with different alco-
hols using magnetically recoverable Pd/Fe3O4 at atmospheric CO
pressure under ligand free conditions. The catalyst is completely
magnetically recoverable because of the superparamagnetic behav-
ior of Fe3O4 and the efficiency of the catalyst remains unaltered
even after 5 cycles. The operational simplicity and the mild reaction
conditions add to the value of this method as a practical alternative
to the alkoxycarbonylation.
nBu
2
3
82
66
O
I
nBu
O
O
I
nBu
O
4
85
Acknowledgment
H3CO
H3CO
ASP and BS thank the Dr. Reddy’s Laboratories Ltd., for the finan-
cial assistance.
O
I
nBu
O
5
6
7
8
85
92
78
90
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F
F
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1–4). Among the different halogen substituted aryl iodides 4-
chloro-iodobenzene gave the product in good yield (Table 3, entries
5–7). Furthermore, the reaction was extended to other aryl iodides
having electron withdrawing groups such as trifluoromethyl and
acetyl groups at para position to generate esters in good to excellent
yields (Table 3, entries 8 and 9).
To check the reusability of the catalyst, as can be seen from
Fig. 3, the reaction was performed with iodobenzene and n-butanol
under the optimized reaction conditions. The catalyst was sepa-
rated from the reaction mixture by applying external magnetic field