Phosphine-free atmospheric carbonylation of aryl iodides with aniline derivatives in the presence of a reusable silica-supported palladium catalyst

Article abstract of DOI:10.1016/j.molcata.2014.11.008

Various palladium catalysts were obtained by the immobilisation of palladium on silica, modified with imidazolium salts. The efficiency of the catalysts was greatly dependent on the choice of the anion of the imidazolium salt, the palladium precursor and on the conditions of heterogenisation. Palladium acetate immobilised on silica with grafted imidazolium chloride moieties was shown to be a selective and recyclable catalyst for atmospheric aminocarbonylation of aryl iodides with aromatic amines in DMF. It was proved that the greater loss of palladium in DMSO can be explained by the formation of soluble palladium complexes.

Full text of DOI:10.1016/j.molcata.2014.11.008

Accepted Manuscript
Title: Phosphine-free atmospheric carbonylation of aryl
iodides with aniline derivatives in the presence of a reusable
silica-supported palladium catalyst
Author: B e´ la Urb a´ n M a´ t e´ Papp D a´ vid Srank o´ Rita
Skoda-F o¨ ldes
PII:
S1381-1169(14)00495-6
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2014.11.008
MOLCAA 9342
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
24-6-2014
3-11-2014
9-11-2014
Please cite this article as: B. Urb a´ n, M. Papp, D. Srank o´ , R. Skoda-F o¨ ldes, Phosphine-
free atmospheric carbonylation of aryl iodides with aniline derivatives in the presence
of a reusable silica-supported palladium catalyst, Journal of Molecular Catalysis A:
Chemical (2014), http://dx.doi.org/10.1016/j.molcata.2014.11.008
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Highlights
Phosphine-free silica supported palladium catalysts were prepared
Silica support was modified with grafted imidazolium chloride
Optimisation of immobilisation was carried out
Selective synthesis of N-arylamides was achieved under atmospheric conditions
The catalyst was reused with small loss of activity
Page 1 of 19

Phosphine-free atmospheric carbonylation of aryl iodides with aniline derivatives in the
presence of a reusable silica-supported palladium catalyst
a
a
b
a
Béla Urbán , Máté Papp , Dávid Srankó , Rita Skoda-Földes
a
University of Pannonia, Institute of Chemistry, Department of Organic Chemistry, H-8201
Veszprém, P.O.Box 158; Hungary
b
Hungarian Academy of Sciences, Centre for Energy Research, Department of Surface Chemistry
and Catalysis, H-1525 Budapest 114., P.O. Box 49, Hungary
Abstract
Various palladium catalysts were obtained by the immobilisation of palladium on silica,
modified with imidazolium salts. The efficiency of the catalysts was greatly dependent on the
choice of the anion of the imidazolium salt, the palladium precursor and on the conditions of
heterogenisation. Palladium acetate immobilised on silica with grafted imidazolium chloride
moieties was shown to be a selective and recyclable catalyst for atmospheric aminocarbonylation
of aryl iodides with aromatic amines in DMF. It was proved that the greater loss of palladium in
DMSO can be explained by the formation of soluble palladium complexes.
Keywords: aminocarbonylation, N-aryl amides, grafted imidazolium ions, palladium, silica
support
1. Introduction
Palladium catalysed carbonylation in the presence of amine nucleophiles [1] serves as a
powerful tool for the construction of the amide functionality, an important structural motif in
pharmacologically active molecules, agrochemicals and peptides [2]. Although amides can be
prepared under mild reaction conditions by the use of homogeneous palladium catalysts,

Corresponding author Tel.: 00-36-88-624719, Fax: 00-36-88-624469, E-mail address: skodane@almos.uni-
pannon.hu
Page 2 of 19

difficulties in separation of the products and catalyst recycling make this methodology less
attractive from the industrial point of view.
In the past 10 years, several efficient immobilised palladium-catalysts were developed,
primarily for C-C coupling reactions [3]. At the same time, only a few examples have been
reported for the use of supported catalysts in aminocarbonylations [4]. Moreover, most of these
reactions were carried out under CO pressure that required the use of high pressure techniques.
Alkoxycarbonylation [5] and microwave induced aminocarbonylation of aryl iodides [6] as well
as the synthesis of N-substituted phthalimides [7] were performed in the presence of Pd/C under
5-9 bar CO pressure. A polymer supported palladium-N-heterocyclic carbene complex was shown
to be a recyclable catalyst in aminocarbonylations under 6.9 bar CO [8]. A palladium catalyst,
immobilised by a bidentate phosphine ligand grafted on Merrifield resin, was reported to convert
bromoarenes to amides at 4.8 bar CO [9]. Pd nanoparticles supported on a zeolitic imidazole
framework (ZIF-8) were described as an efficient heterogeneous catalyst for the
aminocarbonylation of bromoarenes in the presence of phosphines and iodoarenes under
phosphine-free conditions using a CO pressure of 4 bar [10].
The use of higher pressures (30-40 bar) usually led to selective double carbonylation leading
to α-ketoamides. A silica-supported polytitazane–palladium (Ti–N–Pd) complex [11], Pd/C used
3
together with PPh as ligand [12] or palladium-phosphine complexes grafted onto mesoporous
silica (SBA-15) [13] were proved to be active catalysts in such reactions.
In most cases, atmospheric aminocarbonylations were performed with catalysts obtained by
the immobilisation of special, bidentate ligands on solid supports. Cai’s group reported on the
application of palladium-catalysts with bidentate phosphine [14], arsine [15] and mixed sulphur-
phosphine ligands [16] as well as monodentate selenium ligands [17] grafted on silica [15-17] or
MCM-41 [14].
Recently, Seayad disclosed results on atmospheric pressure carbonylation of aryl iodides in
the presence of palladium nanoparticles supported on a metal-organic framework [18]. At the
same time, 2 bar CO pressure had to be used for an efficient recycling of the catalyst and long
reaction time, 24 h in most cases, was necessary with aromatic amines as nucleophiles. Moreover,
it was admitted that this catalyst needed special handling because MOF-5 was moisture-sensitive,
and structural changes occurred that negatively affected the catalytic performance [10]. The
synthesis of isoindole-1,3-diones by a carbonylative cyclisation reaction was reported by Bhanage
using PdCl
2
immobilised on a supported ionic liquid phase (SILP) [19].
In our group, heterogeneous palladium catalysts were prepared using a SILP with grafted
imidazolium-tetrafluoroborate moieties for the immobilisation of palladium [20]. Under pressure,
excellent yields of α-ketoamides, formed by double carbonylation, were obtained. At the same
time, under atmospheric conditions only low conversion of the aryl iodide was observed.
In this paper our results concerning carbonylation of aryl iodides with aromatic amines,
carried out in the presence of SILP palladium catalysts, are presented. It is shown that the outcome
Page 3 of 19

of the reaction depends greatly on several factors, such as the choice of the IL phase, palladium
precursor and conditions of immobilisation.
2. Experimental
2.1.Preparation of the supported ionic liquid phases SILP-1 and SILP-2
SILP-1 was obtained as described in our previous paper by grafting 1-methyl-3-(3-
triethoxysilylpropyl)imidazolium tetrafluoroborate on silica (Kieselgel 60 (0.040-0.063 mm))
[
20]. Ionic liquid loading: 0.63 mmol/g silica (determined by measuring the weight increase after
o
heating the material to constant weight at 150 C in vacuo).
Preparation of SILP-2: A mixture of 1.66 mmol (400 µl) 3-chloropropyl-triethoxysilane 6
ml toluene and 1 g silica (Kieselgel 60 (0.040-0.063 mm), Merck, pre-treated by heating for 6 h at
o
o
2
50 C) was heated under argon at 120 C for 24 h. Then the solid material was filtered, washed
with 2 ml toluene, 2 ml dichloromethane and 2 ml methanol and dried in vacuo. Then it was
suspended in 5 ml toluene and, under stirring, 5 mmol (397 µl) 1-methylimidazole was added
o
dropwise in an inert atmosphere. The mixture was heated at 80 C for 24 h. Then the solid
material was filtered, washed with 2 ml toluene, 2 ml dichloromethane and 2 ml methanol and
dried in vacuo for 8 h (Anal. Found: C, 7.66; H, 1.18; N, 1.58.). Ionic liquid loading: 0.74 mmol/g
silica (determined by measuring the weight increase after heating the material to constant weight
o
at 150 C in vacuo).
2.2. Preparation of the supported catalysts
2.2.1. Preparation of CAT-1
2 3 3
A solution of 8.95 μmol (9.3 mg) Pd (dba) .CHCl - in 2 ml acetonitrile and 2 ml THF was
stirred for 15 min under inert conditions. Then 500 mg of SILP-1 was added and the resulting
mixture was stirred for 24 h at room temperature. After evaporation of the solvents, the catalyst
o
was dried at 35 C in vacuo for 3 h.
2.2.2. Preparation of CAT-2 and CAT-3
A solution of 17.9 mmol μmol Pd(OAc)
2
(for CAT-2) or PdCl (for CAT-3) in 2 ml ethanol
2
was stirred for 15 min under inert conditions. Then 500 mg of SILP-1 was added and the
resulting mixture was stirred for 24 h at room temperature. Then the solid material was filtered,
o
washed with 2 ml ethanol and 2 ml diethylether and dried at 35 C in vacuo for 3 h.
2.2.3. Preparation of CAT-4 — CAT-8
t
Under inert conditions, 3.12 mmol (350 mg) KO Bu was added with stirring to a mixture
containing 2g of SILP-2 and 20 ml solvent (see Table 1). The resulting mixture was stirred for 10
min, and after the addition of 1.60 mmol Pd-salt (see Table 1), it was stirred at room temperature
for 24 h (CAT-4, CAT-5) or 48 h (CAT-6 — CAT-8). Then the solid material was filtered,
washed with 20 ml ethanol and 20 ml diethylether and dried in vacuo for 5 h.
Page 4 of 19

2
2
.3. Catalytic reactions
.3.1. Catalytic reactions at high pressure
In a typical experiment the catalyst (containing 6 μmol Pd) was placed in a stainless steel
autoclave. Iodobenzene (1) (0.2 mmol, 22.5 μl), aniline (0.5 mmol), 0.7 mmol (100 μl)
triethylamine and DMF (1 ml) were transferred into it under an inert atmosphere. It was charged
o
with carbon monoxide (30 bar) and heated with stirring in an oil bath at 100 C. After cooling to
room temperature, the liquid phase was removed with a syringe. The reaction mixture was
analysed by gas chromatography.
2.3.2. Catalytic reactions at atmospheric pressure
In a typical experiment a solution containing the palladium catalyst (with 6 μmol Pd-
content) was placed in a Schlenk-tube. Under argon, 0.2 mmol (22.5 μl) iodobenzene (1), 0.5
mmol amine reagent, 0.7 mmol (100 μl) triethylamine and 1 ml solvent was added and the
atmosphere was changed to carbon monoxide. The reaction mixture was heated with stirring in an
o
oil bath at 100 C and was analysed by gas chromatography.
In recycling experiments, the catalyst was filtered and a fresh supply of reagents was added.
2.4. Analytical measurements
Solid state NMR experiments were performed on a Bruker Avance 400 spectrometer. IR
spectra were made using a Thermo Nicolet Avatar 330 FT-IR instrument. Samples were prepared
in KBr.
For the determination of Pd content on the surface, X-ray photoelectron spectroscopy were
applied using a KRATOS XSAM 800 XPS machine equipped with an atmospheric reaction
chamber. Al K characteristic X-ray line, 40 eV pass energy and FAT mode were applied for
recording the XPS lines of Pd 3d, C 1s, O 1s and Si 2p. Si 2p binding energy at 103.3 eV was
used as reference for charge compensation.
The palladium-content of the catalysts and palladium leaching were determined by ICP.
Reaction mixtures were analysed by gas chromatography (Hewlett Packard 5890) and GC-
MS (Hewlett Packard 5971A GC-MSD, HP-1 column). Conversions and selectivities of the
reactions were determined by GC.
The products 3, 5a-j, 7a-i, 9a-c, 10a-c and 11a,b were identified on the basis of their MS
spectra.
+
3
5
5
5
5
5
: MS(m/z/rel.int.): 197(M )/42; 105/100; 77/52; 51/14
+
a: MS(m/z/rel.int.): 211(M )/47; 105/100; 77/45; 51/8
+
b: MS(m/z/rel.int.): 211(M )/39; 105/100; 77/47; 51/9
+
c: MS(m/z/rel.int.): 253(M )/57; 210/32; 105/100; 77/46; 51/5
+
d: MS(m/z/rel.int.): 225(M )/25; 120/8; 105/100; 91/4; 77/40; 51/6; 40/17
+
e: MS(m/z/rel.int.): 242(M )/9; 198/23; 105/100; 77/47; 51/9
Page 5 of 19

+
5
5
5
5
5
7
7
7
7
7
7
7
1
7
7
7
9
9
9
1
1
5
1
1
1
f: MS(m/z/rel.int.): 242(M )/7; 105/100; 77/51; 51/8
+
g: MS(m/z/rel.int.): 242(M )/6; 105/100, 77/42; 51/6
+
h: MS(m/z/rel.int.): 227(M )/51; 122/5; 105/100; 95/4; 77/38; 51/6
+
i: MS(m/z/rel.int.): 239(M )/25; 105/100; 77/39; 51/6; 43/3
+
j: MS(m/z/rel.int.): 247(M )/46; 105/100; 77/42; 51/6
+
+
a: MS(m/z/rel.int.): 277(M )/33; 275(M )/33; 185/100; 183/100; 157/39; 155/39;104/6;
6/26; 65/14; 50/8
+
+
b: MS(m/z/rel.int.): 233(M )/9; 231(M )/28; 141/31; 139/100; 113/13; 111/42; 75/13; 65/6
+
c: MS(m/z/rel.int.): 215(M )/32, 123/100; 95/48; 75/10; 65/5
+
d: MS(m/z/rel.int.): 242(M )/32; 150/100; 104/38; 92/8; 76/27; 65/8; 50/8
+
e: MS(m/z/rel.int.): 242(M )/38; 150/100; 120/16; 104/39; 92/19; 76/25; 65/8; 50/8; 39/4
+
+
+
f: MS(m/z/rel.int.): 269(M )/3; 267(M )/18; 265(M )/26; 177/10 175/64; 173/100; 149/3;
47/17; 145/26; 109/12; 75/6; 65/8
+
g: MS(m/z/rel.int.): 227(M )/12; 135/100; 107/6; 92/12; 77/14; 65/5
+
h: MS(m/z/rel.int.): 225(M )/25; 133/100; 105/27; 77/15; 65/6; 51/4
+
i: MS(m/z/rel.int.): 247(M )/18; 155/100; 127/72; 101/5; 77/6; 65/5; 51/3
+
a: MS(m/z/rel.int.): 191 (M )/11; 190/34; 176/9; 160/6; 105/100; 86/12; 77/68; 51/24
+
b: MS(m/z/rel.int.): 175(M )/44; 174/28; 146/28; 105/100; 77/57; 51/16
+
c: MS(m/z/rel.int.): 177(M )/13; 176/42; 148/3; 134/3; 105/100; 77/49; 51/10
+
0a: MS(m/z/rel.int.): 219(M )/6; 114/11; 105/100; 86/4; 77/54; 70/26; 51/22
+
0b: MS(m/z/rel.int.): 203(M )/1; 202/4; 105/70; 98/100; 77/51; 70/30; 56/26; 55/54;
1/21; 50/70
+
0c: MS(m/z/rel.int.): 205/(M )/4; 106/58; 100/100; 77/43; 72/71; 51/17
+
1a: MS(m/z/rel.int.): 115(M )/87; 100/62; 86/49; 72/20; 56/100
+
1b: MS(m/z/rel.int.): 99(M )/100; 98/15; 71/63; 70/25; 56/7
3. Results and Discussion
3.1. Preparation of the supported catalysts
Solid supports SILP-1 and SILP-2 were obtained by grafting 1-methyl-3-(3-
triethoxysilylpropyl)imidazolium tetrafluoroborate and 1-methyl-3-(3-
triethoxysilylpropyl)imidazolium chloride, respectively, on silica (Scheme 1).
Page 6 of 19

CH
N BF4
CH
3
CH
N Cl
3
3
-
+
BF4-
+
-
+
N
CH3
N
N
N
N
N
[
Pd]
[
NH ][BF ]
silica
4
4
CAT-1 ... CAT-3
toluene
CH3CN
CHCl3
Si
Si
Si
OEt
EtO OEt
OEt
O O OEt
EtO OEt
Cl
Si
silica
toluene
SILP-1
CH3
N+ Cl-
OEt
Cl
CH3
N
EtO OEt
N
[
Pd]
N
CAT-4 ... CAT-8
Si
toluene
O O OEt
Si
O O OEt
SILP-2
S
cheme 1. Preparation of the supported catalysts
The heterogeneous catalysts were prepared by the addition of the palladium precursors
Table 1), Pd (dba) .CHCl , Pd(OAc) , PdCl , PdBr or PdSO , to the imidazolium modified
(
2
3
3
2
2
2
4
support. In case of CAT-2, CAT-3 and CAT-5 — CAT-8 EtOH was used as solvent to reduce
Pd(II) to Pd(0) [21]. During the preparation of CAT-4 — CAT-8 KOtBu was also added to
facilitate deprotonation of the C2-H of the imidazolium ring and formation of Pd-NHC complexes
[22] that can act as catalysts themselves or serve as reservoir for palladium nanoparticles [23].
Palladium content of the catalysts was determined by ICP (Table 1).
Table 1. Supported palladium catalysts used during the carbonylation reactions
catalyst
Pd-precursor
solvent
additive
Pd-content
a
[
m/m%]
0.29
0.77
0.26
0.26
0.60
0.49
0.55
0.37
CAT-1
CAT-2
CAT-3
CAT-4
CAT-5
CAT-6
CAT-7
CAT-8
Pd
Pd(OAc)
PdCl
2
(dba)
3
.CHCl
3
CH
3
CN+ THF
-
EtOH
EtOH
THF
-
2
2
-
Pd(OAc)
2
2
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
Pd(OAc)
EtOH
EtOH
EtOH
EtOH
PdCl
PdBr
PdSO
2
2
4
a
:
determined by ICP.
Page 7 of 19

3.2. Aminocarbonylation of iodobenzene (1) with aniline (2)
The activities of the supported catalysts were compared in aminocarbonylation of
iodobenzene with aniline as the nucleophile (Scheme 2, Table 2). Selective monocarbonylation
took place in all cases leading to amide 3.
The catalysts obtained by immobilisation of palladium on SILP-1 (CAT-1 — CAT-3) gave
good results under 30 bar CO pressure, but a significant decrease of activity was observed upon
reuse in each case (Table 2, entries 1, 3, 5). As it could be expected after our previous results
obtained in aminocarbonylation with CAT-1 using morpholine as nucleophile [20], CAT-1 and
CAT-2 showed poor performance at atmospheric pressure. In contrast, catalysts obtained starting
from SILP-2 were considerably more active under atmospheric conditions (entries 6-8). Both
activity and recyclability of these catalysts were affected by the immobilisation method, the choice
of palladium precursor and solvent. Total conversion of iodobenzene to amide 3 was observed in
the first run with CAT-4, CAT-5 and CAT-8. With producing 100% conversion in the first run
and exhibiting little loss of activity upon recycling, the catalyst obtained by immobilisation of
Pd(OAc)
2
in ethanol (CAT-5) was chosen for further investigations.
O
I
NH2
[Pd]
+
+
CO
N
H
base
1
2
3
Scheme 2. Aminocarbonylation of iodobenzene (1) with aniline (2)
a
Table 2. Aminocarbonylation of iodobenzene (1) with aniline (2) with different catalysts
b
entry catalyst
CO pressure yield of 3 [%]
[
bar]
run 1
80
run 2
62
25
72
18
86
88
97
45
53
63
run3
61
10
70
16
57
76
95
33
49
53
1
2
3
4
5
6
7
8
9
1
CAT-1
CAT-1
CAT-2
CAT-2
CAT-3
CAT-4
CAT-5
CAT-6
CAT-7
CAT-8
30
1
37
30
1
81
26
30
1
87
>99
>99
83
1
1
1
66
0
1
>99
a
:
3
reaction conditions: 0.2 mmol 1, 0.5 mmol 2, 0.7 mmol Et N, catalyst (with 6 μmol Pd-content), 1 ml DMF, 4h, 100
o
b
C; : determined by GC.
Page 8 of 19

In order to optimise the reaction conditions, carbonylation was carried out in different
solvents and, as an increase in the reaction time had been shown to lead to a more efficient
recycling [20], with a longer reaction time (8 or 16h). No conversion was obtained in dioxane, and
toluene or acetonitrile were found to be only a bit more effective (Table 3, entries 1-3). Both DMF
and DMSO turned out to be suitable solvents and 1 was fully converted to 3 even in the third runs.
The amount of palladium leached into the reaction mixtures was determined by ICP. As it was
expected, an increase in the reaction time led to lower leaching of palladium but the difference
was found to be not significant (compare entries 4-6 and 7-9). At the same time, a considerably
greater loss of palladium was observed in DMSO (entries 10-12).
To obtain information about the homogeneous or heterogeneous nature of the catalytic
reaction, hot filtration and mercury poising tests were carried out (Table 4).
Catalytic mixtures obtained in DMF and DMSO was filtered after an hour and half an hour,
respectively. One half of the mixtures was heated further in CO atmosphere, the other was treated
similarly but in the presence of mercury.
Page 9 of 19

Table 3. Effect of solvent on the aminocarbonylation of iodobenzene (1) with aniline (2)
a
with CAT-5
c
entry solvent
reaction
run
yield of Pd-leaching [%]
b
time [h]
3 [%]
1
2
3
4
5
6
7
8
9
1
1
1
1,4 dioxane
toluene
CH CN
8
1
1
1
1
2
3
1
2
3
1
2
3
-
n.d.
n.d.
n.d.
2.2
8
17
d
3
8
19
DMF
8
100
100
100
100
100
100
100
100
100
DMF
8
3.6
DMF
8
3.5
DMF
16
16
16
8
1.2
DMF
3.2
DMF
3.4
0
1
2
DMSO
DMSO
DMSO
14.9
12.3
6.7
8
8
a
:
3
reaction conditions: 0.2 mmol 1, 0.5 mmol 2, 0.7 mmol Et N, CAT-5 (with 6 μmol Pd-content) and 1 ml solvent, 1
o
b
c
bar CO, 100 C; : determined by GC; : determined by ICP ((mmol Pd in the reaction mixture/ mmol Pd on the fresh
d
o
catalyst)x100); : the reaction was carried out at 80 C
a
Table 4. Hot filtration and mercury poisoning tests
entry solvent
first step
second step
reaction yield of Hg
reaction yield of
b
b
time [h] 3 [%]
time [h] 3 [%]
1
2
3
4
DMF
1
46
64
-
4
4
4
51
46
85
75
+
-
DMSO
0.5
+
4
a
:
3
reaction conditions: 0.2 mmol 1, 0.5 mmol 2, 0.7 mmol Et N, CAT-5 (with 6 μmol Pd-content) and 1 ml solvent, 1
o
b
bar CO, 100 C; : determined by GC;
According to the results, in DMF only a slow conversion of iodobenzene occurred after the
removal of the heterogeneous catalyst and the reaction could be completely stopped by the
addition of mercury (Table 4, entries 1,2). This shows that a small amount of catalytically active
palladium nanoparticles may have leached to the reaction mixture. In contrast, in DMSO a
noticeable carbonylation took place in the absence of the heterogeneous catalyst and, at a lower
rate, even in the presence of mercury (Table 4, entries 3,4). As DMSO is a good ligand for
Page 10 of 19

palladium [24], it can be assumed that in this case soluble palladium complexes are among the
active catalytic species. This can explain the higher amount of leached palladium in reactions
carried out in DMSO (Table 3, entries 10-12).
3.3. Aminocarbonylation of other substrates
With the optimal reaction conditions in hand, aminocarbonylation of iodobenzene (1) was
carried out using substituted aniline derivatives (4a-j) as nucleophiles (Figure 1) and various aryl
iodides as substrates (Figure 2). As it could be expected, the presence of electron withdrawing
groups in the nucleophiles (Figure 1, 4e-g, 4i), as well as a sterically crowded nitrogen (4d) led to
lower yields of the products (5e-g, 5i 5d) but the catalyst could efficiently be recycled even in
these cases. Excellent results were obtained with different aryl iodides (Figure 2) with the
exception of derivatives with electron donating groups (7g, 7h). It should be mentioned that
selective substitution of iodine was observed in case of chloro- (6b, 6f) or bromo substituted
compounds (6a). Carbonylation of 4-iodophenol or 4-iodoaniline led to some unidentified
polymeric material.
O
I
NH2
CAT-5
R
+
+
CO
N
H
R
DMF, Et N
3
1
bar, 100 oC, 8h
1
4a-j
5a-j
Me
Me
Bu
O
O
O
O
N
N
H
N
H
N
H
H
Me
Me
5a, 100%/98%/99%
5b, 100%/100%/99%
5c, 100%/100%/100%
5d, 90%/87%/88%
NO2
O
O
O
N
NO
2
N
H
N
H
H
NO2
5e, 82%/83%/82%
5f, 84%/83%/83%
5g, 89%/87%/88%
OMe
COMe
O
O
O
N
N
H
N
H
H
5h, 100%/99%/100%
5i, 85%/87%/85%
5j, 86%/83%/84%
Figure 1. Aminocarbonylation of iodobenzene (1) with various aromatic amines (4a-j) in the
presence of CAT-5 (Reaction conditions: 0.2 mmol 1, 0.5 mmol nucleophile, 10 mg catalyst, 1 ml
o
DMF, 1 bar CO, 100 C, 8h. Yields of three successive runs, determined by GC.)
Page 11 of 19

O
I
NH2
CAT-5
+
+
CO
N
DMF, Et N
bar, 100 oC, 8h
H
R
3
R
1
6a-i
2
7a-i
O
O
O
O
Br
Cl
F
O N
2
N
N
N
H
N
H
H
H
7
a, 100%/100%/100%
7b, 100%/100%/100%
7c 100%/99%/100%
7d, 100%/100%/99%
O
O
O
N
H
N
H
N
H
Cl
Cl
O N
MeO
2
7
e, 100%/100%/100%
7f, 100%/99%/99%
7g, 93%/89%/92%
O
O
Me
Me
N
H
N
H
7
h, 88%/83%/85%
7i, 100%/100%/100%
Figure 2. Aminocarbonylation of aryl iodides (6a-i) with aniline (2) in the presence of CAT-
(Reaction conditions: 0.2 mmol aryl iodide, 0.5 mmol 1, 10 mg catalyst, 1 ml DMF, 1 bar CO,
5
o
1
00 C, 8h. Yields of three successive runs, determined by GC.)
Aminocarbonylation of iodobenzene (1) with aliphatic amines (Scheme 3, 8a-c) was also
attempted. Lower conversion of iodobenzene, compared to that in the reaction of aniline, and poor
selectivities were observed in each case (Table 5). Beside the amide products 9a-c, the presence of
the corresponding α-ketoamides (10a-c), obtained by double carbonylation, was also detected.
Moreover, in case of cyclic amines (8a,b) formylation of the amino group led to products 11a,b,
which lowered the concentration of the nucleophilic reagent available for carbonylation.
Page 12 of 19

O
R1
N
O
R1
N CHO
R2
R1
N H
R2
R1
CAT-5
DMF, Et
+
R2
+
N
R
1
+
+ CO
N
2
3
O
o
1
bar, 100 C, 8h
O
9a-c
10a-c
11a, b
8a:
N
H
8b:
8c: Et NH
2
N
H
Scheme 3. Aminocarbonylation of iodobenzene (4) with morpholine (5a) as the nucleophile
a
Table 5. Aminocarbonylation with aliphatic amines
b,d
amine
conversion of 1 product distribution product distribution [%]
b
b,c
[%]
[%]
9
10
30
20
17
9
10
20
16
17
11
morpholine (8a)
pyrrolidine (8b)
67
80
77
70
80
83
47
61
83
33
23
-
diethylamine (8c)
a
:
3
reaction conditions: 0.2 mmol 1, 0.5 mmol amine (8a-c), 0.7 mmol Et N, CAT-5 (with 6 μmol Pd-content) and 1 ml
o
b
c
solvent, 1 bar CO, 100 C; : determined by GC; : for products obtained from iodobenzene (1): [mmol 9 (or 10)/
c
(
mmol 9 + mmol 10)]x100; : for products obtained from the amine (8a-c): [mmol 9 (or 10 or 11)/ (mmol 9 + mmol
1
0+ mmol 11)]x100;
3
.4. Characterisation of catalyst CAT-5
13
Immobilisation of the ionic liquid on the surface of silica was proved by solid state C CP
MAS measurements (Figure 3). The peaks at chemical shifts of 123.7 ppm and 136.8 ppm
correspond to the three imidazole ring carbon atoms. The four signals in the region of 9.0 ppm —
53.0 ppm can be assigned to the carbons of the alkyl side chains. The lack of peaks of ethoxy
groups proves the successful grafting of the ionic liquid on the surface. The spectrum of the spent
catalyst is essentially the same, with signals corresponding to residual DMF (164.4 ppm, 31.8
ppm) and aromatic product (164.4 ppm and around 131 ppm).
Page 13 of 19

13
Figure 3. C CP MAS spectra of CAT-5 (as synthesized (left), spent (right))
Comparison of the IR spectra of silica and CAT-5 (Figure 4) shows the appearance of peaks
corresponding to CH stretching and a decrease in the intensity of the OH stretching band in the
latter spectrum. The spectrum of the spent catalyst is similar, the appearance of a band around
-1
1
660 cm can be attributed to the amide group of residual DMF and product.
Figure 4. IR spectra of silica (left) and CAT-5 (as synthesized (middle), spent (right))
X-ray photoelectron spectroscopy (XPS) analysis was performed on the as-synthesized as
well as on the spent catalyst CAT-5 (after 2 cycles) (Table 6, Figure 5). The Pd 3d regions of the
catalysts are shown in Figure 6. The two bands at around 335.1 eV and 340.4 eV were assigned to
o
Pd (3d5 and 3d3/2 respectively), while the bands at around 337.3 eV and 342.6 eV were
/2
attributed to Pd(II) (3d5/2 and 3d3/2 respectively). These results are strengthened by several
previous ones reported elsewhere [25-27].
The atomic ratios on the surface were calculated using sensitivity factors given by the
o
manufacturer. These ratios for the Pd, Si and C are presented in Table 6. The Pd content were
o
similar for both of the samples, although after the catalytic cycle the Pd(II)/Pd ratio decreased. It
o
can be described as the effect of the Pd enrichment on the surface upon the catalytic reaction.
The effect of the catalytic reaction can be observed in the changes of the Pd/Si and Pd/C ratios as
well. The smaller Pd/Si and Pd/C ratios were typical for the sample after catalytic cycle. These
o
changes of the surface structure coupled with the different Pd(II)/Pd can be described as the
effect of the catalytic reaction.
Page 14 of 19

o
Table 6. XPS Pd 3d5/2 binding energies (eV), Pd(II)/Pd , Pd/Si and Pd/C surface atomic
ratios of as prepared and spent Pd catalysts
Position of the peak
Ratio of the atomic concentrations
Pd 3d5/2
Sample
o
o
Pd (eV) Pd(II) (eV)
Pd(II)/Pd
Pd/Si
Pd/C
CAT-5
-
1
1
-1
-1
-1
-1
3
35.1
35.1
337.3
337.0
2.45×10
2.05×10
2.75×10
4.66×10
CAT-5 (spent)
-
3
1.46×10
1.59×10
O 1s
O 1s
I 3d
F 1s
F 1s
Pd 3d
Pd 3d
Si 2p
Si 2s
Cl 2p
Si 2p
Si 2s
N 1s
N 1s
400
C 1s
C 1s
800
700
600
500
400
300
200
100
0
800
700
600
500
300
200
100
0
Binding Energy (eV)
Binding Energy (eV)
Figure 5. Wide scan XPS spectra of Pd catalyst CAT-5 (as synthesized (left), spent (right))
Intensity(cps)
Intensity(cps)
Pd 3d3/2
Pd 3d5/2
Background(cps)
Pd 3d3/2
Pd 3d5/2
Background(cps)
0
0
Pd 3d5/2
Pd 3d5/2
0
0
Pd 3d3/2
Pd 3d3/2
Pd(II) 3d5/2
Pd(II) 3d5/2
o
Pd(II) 3d3/2
Pd(II) 3d3/2
Pd
Envelope(cps)
o
Envelope(cps)
Pd
Pd(II)
Pd(II)
345
340
335
330
325
345
340
335
330
325
Binding Energy (eV)
Binding Energy (eV)
Figure 6. Pd 3d XPS spectra of Pd catalyst CAT-3 (as synthesized (left), spent (right))
4. Conclusions
Various phosphine-free silica supported palladium catalysts were prepared and tested in
atmospheric aminocarbonylation of iodobenzene in the presence of aromatic amines. Activity of
the catalysts were found to be affected both by the choice of the palladium precursor and
conditions of immobilisation. The catalyst obtained from Pd(OAc) in ethanol and using KOtBu
2
as an additive was found to be the most suitable one for carbonylations carried out in DMF. It
performed high activity and good recyclability for the reaction of iodobenzene with a number of
Page 15 of 19

1
6
aromatic amines, as well as for the carbonylation of substituted iodobenzenes with aniline. It was
shown that the greater drop of catalytic activity, as well as a higher amount of leached palladium
in reactions in DMSO solvent are due to the formation of soluble palladium complexes.
In carbonylations with aliphatic amines, side reactions leading to α-ketoamides and N-
formyl amines could be detected.
Page 16 of 19

1
7
Acknowledgments
The authors thank for the support of the Hungarian National Science Foundation (OTKA
K105632) and project TÁMOP-4.2.2.A-11/1/KONV-2012-0071, realised with the support of the
Hungarian Government and the European Union, with the co-funding of the European Social
Fund. Mr. A. Tóth is acknowledged for his assistance in GC-MS measurements.
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*Graphical Abstract (for review)
Page 19 of 19