Heterogeneous catalysis in protodecarboxylation and c c bond formation 1

HETEROGENEOUS CATALYSIS IN
PROTODECARBOXYLATION AND C-C BOND
FORMATION












TOY XIU YI
(B. Sc. (Hons.), National University of Singapore)









A THESIS SUBMITTED

FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

DEPARTMENT OF CHEMISTRY

NATIONAL UNIVERSITY OF SINGAPORE

2013
! ! ! ! ! ! ! !
II!

DECLARATION




I hereby declare that this thesis is my original work and it has been written by
me in its entirety, under the supervision of A/P Stephan Jaenicke, Chemistry
Department, National University of Singapore, between 01/08/2009 and
01/08/2013.

I have duly acknowledged all sources of information which have been used in
the thesis.

This thesis has also not been submitted for any degree in any university
previously.

The content of the thesis has been partly published in:

(1) Xiu Yi Toy, Irwan Iskandar Bin Roslan, Gaik Khuan Chuah and
Stephan Jaenicke, Catal. Sci. Technol., 2013, DOI:
10.1039/c3cy00580a

Name

Signature

Date


















Toy!Xiu!Yi!
19/11/2013!
! ! ! !

III!
ACKNOWLEDGEMENT

This dissertation would not have been possible without the guidance and the
help of several individuals who extended their valuable assistance in the
preparation and completion of this study. The 4 years of Ph.D research study
have been a truly memorable learning journey.
First and foremost, I would like to express my sincere appreciation to my
supervisor Associate Professor Dr. Stephan Jaenicke for giving me the
opportunity to work on the project in his research lab. His stimulating
suggestions, encouragement and immense knowledge helped me greatly
throughout the project.
I would also like to thank Associate Professor Dr. Chuah Gaik Khuan for her
help and invaluable advices throughout my research and writing of this thesis.
I truly appreciate all time she has taken to read and correct my writings and
manuscript.
My sincere thanks also goes to Madam Toh Soh Lian, Madam Tan Lay San
and Miss Sabrina Ou from Applied Chemistry lab for all the help they have
rendered during my work.
This thesis would not have been possible without the help and support from
my fellow lab mates: Miss Nie Yuntong, Miss Ng Jeck Fei, Mr. Do Dong
Minh, Mr. Fan Ao, Miss Liu Huihui, Mr. Wang Jie, Miss Gao Yanxiu, Miss
Han Aijuan, Mr Goh Sook Jin, Mr Sun Jiulong, Mr Irwan Iskandar Bin Roslan
and Miss Angela Chian.
I am also grateful to my parents and my family for their unconditional love,
encouragement and motivation. I would like to give my special thanks to my
fiance for believing in me and giving me the moral support when it was most
! ! ! ! ! ! ! !
IV!
required.

Last but not least, I am indebted to the National University of Singapore for
providing me with a valuable research scholarship and for funding the project.






















! ! ! !
V!
TABLE OF CONTENTS

PAGE
Declaration

II
Acknowledgement
III
Table of contents
V
Abstract
XI
List of tables
XII
List of figures
XV
List of schemes
XXII
List of journal publications and conferences paper
XXV


PAGE
Chapter 1: Introduction
1
1.1
Supported nanosized transition metal catalysts in fine
chemical synthesis
1

1.1.1 Homogeneous catalysts versus heterogeneous
catalysts
2

1.1.2 Heterogeneous catalysts: Supported metal catalysts

9

1.1.3 Catalyst preparation methods
12

1.1.3.1 Impregnation
12

1.1.3.2 Co-precipitation
15

1.1.3.3 Deposition-precipitation
15

1.1.3.4 Ion exchange
17
1.2
Ag, Cu and Pd nanocatalysts in cross coupling reactions
18

1.2.1 Suzuki coupling
21
! ! ! ! ! ! ! !
VI!

1.2.2 Ullmann reaction
23
1.3
Decarboxylative cross-coupling
26

1.4
Aim and outline of the thesis
32
1.5
References
34

Chapter 2: Experimental- Catalyst characterisation techniques
40
2.1
Powder x-ray diffraction
40

2.1.1 Principles of measurement
41
2.2
N
2
sorption porosimetry
44

2.2.1 Principles of measurement
45

2.2.1.1 Brunauer-Emmett-Teller (BET) Theory
45

2.2.1.2 Barrett-Joyner-Halenda (BJH) method
47

2.2.2 Sample preparation and data measurement
48
2.3
Transmission electron microscopy (TEM)
49

2.3.1 Principles of measurement
49
2.4
X-ray photoelectron spectroscopy (XPS)
53

2.4.1 Principles of measurement
53
2.5
Inductively coupled plasma atomic emission
spectroscopy (ICP-AES)
57

2.5.1 Principles of measurement
57
2.6
Temperature programmed reduction (TPR)
60

2.6.1 Principles of measurement
60
2.7
References
62

! ! ! !
VII!
Chapter 3: Homocoupling of aryl halides using palladium-
poly(ethylene glycol) catalysts
64
3.1
Introduction
64

3.1.1 Transition metal-catalysed coupling reactions
64

3.1.2 Polyethylene glycol as reaction medium
64

3.1.3 Examples of coupling reactions carried out in PEG
reaction medium
66
3.2
Experimental
67

3.2.1 Typical procedure for homocoupling of aryl bromide
68

3.2.2 Recovery and reuse of the catalyst
68
3.3
Results and discussion
69

3.3.1 Catalyst testing
69

3.3.2 Recycling of the catalyst
77

3.3.3 Scope of reaction
83

3.3.4 Mechanism and characterisation of the Pd-PEG-EG
catalyst
84

3.3.5 Proposed mechanism
87
3.4
Conclusion
90
3.5
References
91
3.6
Appendix

95

Chapter 4. Protodecarboxylation of carboxylic acids using
heterogeneous silver catalyst
97
4.1
Introduction
97
4.2
Experimental
101

4.2.1 Preparation of supported silver catalysts
101

4.2.2 Procedures for catalytic studies
101
! ! ! ! ! ! ! !
VIII!
4.3
Results and discussion
102

4.3.1 Catalyst characterisation
102

4.3.2 Catalytic testing
109

4.3.2.1 Optimisation of reaction conditions

109

4.3.2.2 Effect of Ag loading
113

4.3.2.3 Effect of temperature and determination of
reaction parameters
117

4.3.2.4 Scope of reaction
119

4.3.3 Study of reaction mechanism
122

4.3.3.1 Role of K
2
CO
3
in the reaction mechanism
122

4.3.3.2 Proposed reaction mechanism
128
4.4
Conclusion
129
4.5
References
130

4.6
Appendix
132

Chapter 5: Alumina supported copper catalyst for
protodecarboxylation of aromatic carboxylic
acids
135
5.1
Introduction
135
5.2
Experimental
136

5.2.1 Preparation of supported copper catalyst
136

5.2.2 Catalytic studies
137
5.3
Results and Discussion
137

5.3.1 Catalyst characterisation
137

5.3.2 Catalyst activity testing and optimisation of reaction
conditions
150

5.3.3 Study of catalyst properties
154
! ! ! !
IX!

5.3.3.1 Cu weight loading
154

5.3.3.2 Effect of H
2
pretreatment of the Cu/Al
2
O
3

WI-SG catalyst
156

5.3.4 Study of reaction mechanism: kinetic rate expression
and nature of the reaction
157

5.3.5 Proposed Mechanism
160

5.3.6 Leaching and recycling test
162

5.3.7 Effect of oxidant

166

5.3.7.1 Effect of inert atmosphere and use of oxidant
166

5.3.7.2 Effect of amount of K
2
S
2
O
8

168

5.3.8 Scope of reaction
170
5.4
Conclusion
171
5.5
References
172

Chapter 6: Heterogeneous catalysts for the decarboxylative
cross-coupling of aryl carboxylic acids and aryl
halides
174
6.1
Introduction
174

6.2
Experimental
179

6.2.1 Preparation of supported Cu catalyst
179

6.2.2 Catalytic studies
181
6.3
Results and discussion
181

6.3.1 Characterisation of catalysts
181

6.3.2 Catalytic testing
191

6.3.2.1 Effect of moisture-free reaction conditions
194

6.3.2.2 Optimisation of reaction conditions
196

6.3.2.3 Effect of amount of iodobenzene
198
! ! ! ! ! ! ! !
X!

6.3.2.4 Effect of Cu loading, amount of catalyst and
reaction time
200

6.3.2.5 Cu·Pd/Al
2
O
3
-catalysed decarboxylative cross-
coupling
201

6.3.2.6 Proposed reaction mechanism
206
6.4
Conclusion
209
6.5
References
210
6.6
Appendix
212

Chapter 7: Final conclusion
213

! ! ! !
XI!
ABSTRACT
Ullmann reaction and decarboxylative cross-coupling reactions are
green alternatives for the formation of C-C bonds between aromatic
compounds. These methods do not require preformed organometallic reagents
which improve their atom efficiency. Since heterogeneous catalysts offer
many advantages over homogeneous catalysts such as easy separation and
recovery, the aim of this study is to develop and improve heterogeneous
catalysts for the Ullmann reaction and decarboxylative cross-coupling. In
chapter 3, the development of a Pd(OAc)
2
-PEG-EG catalytic system for
Ullmann coupling of bromobenzene is described. In chapter 4 and 5, we
present the use of alumina supported Ag and Cu catalysts for
protodecarboxylation of ortho-substituted aromatic benzoic acids. In chapter 6,
monometallic Ag/Al

2
O
3
and Cu/Al
2
O
3
catalyst, and bimetallic Cu!Pd/Al
2
O
3

catalysts were used in the study of decarboxylative cross-coupling of the
potassium salt of 2-nitrobenzoic acid and iodobenzene.










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XII!
LIST OF TABLES
PAGE
Table 1.1
A list of PZC of some common oxides in water

17
Table 1.2
Physical properties of Pd, Cu and Ag
19
Table 1.3
Scope of reaction for ligand-free Pd/C catalysed
Suzuki coupling
22
Table 3.1
Summary of results for homocoupling of
bromobenzene using Pd-PEG catalysts
69
Table 3.2
Homocoupling of bromobenzene carried out using
PEG 2000-Pd(OAc)
2
with different additives and
reaction temperature
71
Table 3.3
Homocoupling of bromobenzene carried out using
PEG of different average molecular weight
73
Table 3.4
Homocoupling of bromobenzene carried out using
PEG 900 with varying amount of DMA
75
Table 3.5
Homocoupling of bromobenzene carried out in the
presence of 4g of PEG 900 and varying amounts of

ethylene glycol (EG)
77
Table 3.6
Influence of the halogen atom on the Pd-PEG-EG
catalysed homocoupling
83
Table 4.1
BET surface area, pore volume and Ag crystallite
size of the supported silver catalysts
102
Table 4.2
XPS results for Ag/Al
2
O
3

107
Table 4.3
Influence of support and active metal
109
Table 4.4
Particle size, total number of surface atoms in the
reaction mixture, initial rate and turnover frequency
of supported silver catalysts
116
Table 4.5
Protodecarboxylation of various aromatic carboxylic
acids using 10 wt. % Ag/Al
2
O

3

121
Table 4.6
Protodecarboxylation of 2-nitrobenzoic acid or
potassium nitrobenzoate using 10 wt. % Ag/Al
2
O
3

under different conditions
124
Table 4.7
Ionic radii of alkali metal ions, Ag
+
, O
2-
and Ag-O
bond length
126
Table 5.1
Summary of BET surface area and pore volume of
γ-Al
2
O
3
(commercial and sol-gel), 10 wt. %
141
! ! ! !
XIII!

Cu/Al
2
O
3
WI catalyst, WI-SG catalysts with 1 wt. %
to 15 wt.% Cu weight loadings
Table 5.2
Copper (Cu) and aluminium (Al) ratio obtained from
ICP measurements.
142
Table 5.3
XPS binding energies (BE) for Cu 2p
3/2
transitions,
Cu LMM kinetic energy (KE) and the modifed Auger
parameter, α’
143
Table 5.4
Reference values for XPS binding energy values
(BE) of Cu 2p
3/2
transitions, Cu LMM kinetic energy
(KE) and the modified Auger parameter, α’ for Cu,
Cu
2
O and CuO.
144
Table 5.5
Summary of the copper and aluminium ratio obtained
from the XPS measurements

147
Table 5.6
Summary of the results obtained using 10.0 wt. %
Cu/Al
2
O
3
WI catalyst for the optimisation of reaction
conditions. The 10.0 wt. % Cu/Al
2
O
3
WI catalyst was
pretreated under flowing H
2
at 300
o
C for 2 h before
use except for 1
a

151
Table 5.7
Reaction conditions used to obtain rate order
information
159
Table 5.8
Scope of reaction using optimised reaction conditions
170
Table 6.1

BET surface area, pore volume and average particle
size

186
Table 6.2
Elemental analysis results obtained using ICP-AES
186
Table 6.3
XPS binding energies of the electronic transitions of
Pd, Cu and Al species 2.5 wt. % Cu·1.0 wt. %
Pd/Al
2
O
3

187
Table 6.4
XPS binding energies and normalised intensity ratios
for bimetallic Cu·Pd catalysts prepared by selective
adsorption with 1.0 and 5.0 wt. % Cu
190
Table 6.5
Preliminary results obtained for decarboxylative
cross-coupling of 2-nitrobenzoic acid and
iodobenzene using alumina supported metal catalysts
192
Table 6.6
Effect of moisture-free conditions on the
decarboxylative cross-coupling of potassium
2–nitrobenzoate and iodobenzene

194
Table 6.7
Summary of results obtained from the solvent screen
196
! ! ! ! ! ! ! !
XIV!
Table 6.8
Optimisation of the ratio iodobenzene : potassium
nitrobenzoate
199
Table 6.9
Study of Cu loading, amount of Cu catalyst used and
reaction time
200
Table 6.10
Summary of results obtained with bimetallic
2.5 wt.% Cu·1.0 wt. % Pd/Al
2
O
3
catalysts
204

! ! ! !
XV!
LIST OF FIGURES

Figure 1.1
A plot of the calculated fraction of Au atoms at the
corner (red), edge (blue), and crystal face (green) of
a truncated octahedral gold nanoparticle. The insert
shows the top half of a truncated octahedral gold
nanoparticle and the position of the corner, edge and
surface atoms
4
Figure 1.2
Furfural hydrogenation pathways on Pt(111) surface
5
Figure 1.3

Examples of reactions of organometallic complexes
7
Figure 1.4
Formation of ammonia on a heterogeneous catalyst
surface
8
Figure 1.5
Selective hydrogenation of crotonaldehyde to crotyl
alcohol
10
Figure 1.6
The surface-to-volume ratio decreases with
increasing volume of a particle
11
Figure 1.7
A schematic representation of the typical features of
a metal surface
12
Figure 1.8
Active phase distribution during impregnation, (a)
uniform; (b) egg-shell, (c) egg-white and (d) egg-
yolk
13
Figure 2.1
Schematic diagram of the scattering of x-rays by a
crystalline material
42
Figure 2.2
A typical adsorption/desorption isotherm
45

Figure 2.3
Operating modes of TEM: (a) diffraction mode and
(b) imaging mode
51
Figure 2.4
The energy levels involved in the emission and
detection of the photoelectrons
53
Figure 2.5
(a) Emission of photoelectron and Auger electron; (b)
XPS spectrum collected from a silicon wafer
54
Figure 2.6
Wagner plot for B.E.
XPS
Cu 2p
3/2
photoelectron and
K.E Cu LMM Auger electron
57
Figure 3.1
Conversion and selectivity of products obtained over
3 consecutive Pd-PEG-EG catalysed homocoupling
reaction runs
77
Figure 3.2
Kinetic profile of Pd-PEG-EG catalysed
homocoupling reaction carried out in a closed system
78
! ! ! ! ! ! ! !

XVI!
in the presence of air with addition of fresh
bromobenzene after 100 % conversion was achieved
Figure 3.3
Pd-PEG-EG catalysed homocoupling of
bromobenzene carried out in a closed system in the
presence of (♦) no Cs
2
CO
3
, (■) 2 mmol Cs
2
CO
3
, and
(▲) 4 mmol Cs
2
CO
3

79
Figure 3.4
Kinetic profile of recycling test carried out in a
closed system in the presence of (□) air and (♦) N
2

80
Figure 3.5
Total conversion and selectivities towards benzene,
biphenyl and terphenyl obtained in each of the 4

consecutive Pd-PEG-EG catalysed homocoupling
reaction runs
81
Figure 3.6
TEM images of Pd nanoparticles formed in PEG-EG
(a) before reaction (stir 1 h at 120
o
C), (b) after
reaction at 120
o
C for 24 h using 4 mmol of
bromobenzene
82
Figure 3.7
(a) PEG-EG mixture and (b) PEG-EG immediately
after addition of Pd(OAc)
2
and (c) PEG-EG after
stirring with Pd(OAc)
2
at 120
o
C for 2 mins
86
Figure 3.8
X-ray diffractograms of Pd-EG-PEG carried out at
120
o
C taken (a) at every hour for 5 h from 2 Theta =
30-90

o
, (b) at 6 h from 2 Theta = 38-42
o

86
Figure 3.9
Typical GC-MS spectrum of the homocoupling of
bromobenzene
95
Figure 3.10
GC spectrum of the homocoupling of chlorobenzene
95
Figure 3.11
GC spectrum of homocoupling of iodobenzene
96
Figure 3.12
GC spectrum of homocoupling of 1-chloro-4-
bromobenzene
96
Figure 4.1
Chelating agents used in protodecarboxylation
reactions: 1: 1,10-phenanthroline, 2: 2,2’ bipyridyl
98
Figure 4.2
X–ray diffractograms of 10 wt. % Ag supported on
(a) SiO
2
(b) Al
2
O

3
(c) MgO (d) TiO
2
and (e) ZnO.
The positions of the silver lines are indicated with a
star *
103
Figure 4.3
Nitrogen adsorption and desorption isotherms for
Al
2
O
3
supported silver catalysts with 10 wt. % Ag
loading. Insert: pore size distribution
104
! ! ! !
XVII!
Figure 4.4
X-ray diffraction patterns of (a) calcined Al
2
O
3

support, and the catalysts with (b) 5 wt. % Ag,
(c) 10 wt. % Ag, (d) 15 wt. % Ag, (e) 20 wt. % Ag
(traces are offset by 1000 counts). The positions of
the silver lines are indicated with a star *
104
Figure 4.5

TEM images of (a) 5 wt. %, (b) 10 wt. %,
(c) 15 wt. %, (d) 20 wt. % Ag/Al
2
O
3

106
Figure 4.6
XPS spectra for 5-15 wt. % Ag/Al
2
O
3

108
Figure 4.7
Kinetic profile of model reaction catalysed by
10 wt. % Ag/Al
2
O
3
with different catalyst
pretreatment
112
Figure 4.8
Kinetic profile of model reaction catalysed by fresh
and recycled 10 wt. % Ag/Al
2
O
3
.

113
Figure 4.9
Kinetic profiles of the model reaction carried out
using 5-20 wt. % Ag/Al
2
O
3
and AgOAc
114
Figure 4.10
Plot of initial rate against silver loading of the
supported silver catalysts
114
Figure 4.11
Kinetic profile of protodecarboxylation of
2-nitrobenzoic acid carried out at (") 100
o
C,
(#) 110
o
C, (▲) 120
o
C, (!) 130
o
C
118
Figure 4.12
Arrhenius plot of ln k against 1/T.
119
Figure 4.13

Ortho-substituent coordinating to a surface Ag
δ
+

centre during the decarboxylation process
120
Figure 4.14
Kinetic profiles of 10 wt. % Ag/ Al
2
O
3
-catalysed
protodecarboxylation of (") 2-nitrobenzoic acid
(2 mmol), with K
2
CO
3
(0.3 mmol);
(#) 2-nitrobenzoic acid (2 mmol), without K
2
CO
3
;
(▲) Potassium 2-nitrobenzoate (2 mmol) without
AcOH; (!) Potassium 2-nitrobenzoate (2 mmol) with
AcOH (2 mmol)
124
Figure 4.15
Influence of added potassium salts: Kinetic profiles
of the protodecarboxylation of 2-nitrobenzoic acid

catalysed by 10 wt. % Ag/ Al
2
O
3
in the presence of
(") 0.3 mmol of KCl; (#) 0.3 mmol of K
2
SO
4
; and
(▲) 0.3 mmol of K
2
CO
3
; ($) 0.3 mmol of KOH,
(×) 0.6 mmol of KOH
125
Figure 4.16
Effect of alkali metal carbonates on
protodecarboxylation of 2-nitrobenzoic acid
127
! ! ! ! ! ! ! !
XVIII!
Figure 4.17
Plot of initial rate against mol. % of K
2
CO
3
used
128

Figure 4.18
N
2
adsorption and desorption isotherms of the
5-20 wt. % Ag/Al
2
O
3.
Insert: Pore size distribution
132
Figure 4.19
XRD pattern of (a) fresh 10 wt. % Ag/Al
2
O
3
and
(b) recycled 10 wt. % Ag/Al
2
O
3

132
Figure 4.20
N
2
adsorption and desorption isotherms of (#) fresh
and (▲) recycled and recalcined 10 wt. % Ag/Al
2
O
3

133
Figure 4.21
Pore size distribution of (#) fresh and (▲) recycled
and recalcined 10 wt. % Ag/Al
2
O
3

133
Figure 4.22
HPLC spectrum of a typical test reaction carried out
using 2-nitrobenzoic acid as substrate, K
2
CO
3
as
base, 10 wt. % Ag/Al
2
O
3
as catalyst at 120
o
C. The
spectrum was recorded for 30 mins to ensure that no
other products are formed
134
Figure 4.23
Kinetic profiles for protodecarboxylation of 2-
nitrobenzoic acid over (") 10 wt % Ag/Al

2
O
3
, (×)
Ag
2
O (commercial) and (#) Ag powder.
134
Figure 5.1
Powder XRD patterns of 10 wt. % Cu/Al
2
O
3
: (a) WI
catalyst without H
2
pretreatment, (b) WI catalyst
with H
2
pretreatment, (c) WI-SG catalyst with H
2

pretreatment ( + : lattice plane of γ-Al
2
O
3;
* : lattice
plane

of metallic Cu, # : lattice plane of CuO)

138
Figure 5.2
N
2
adsorption and desorption isotherms of 10 wt. %
Cu/Al
2
O
3
: (")WI and (▲) WI-SG catalyst
139
Figure 5.3
Pore size distribution of 10 wt. % Cu/Al
2
O
3
: (")WI
and (▲) WI-SG catalyst
139
Figure 5.4
Powder XRD patterns of γ-Al
2
O
3
supported with
(a) 1.0 wt. % Cu, (b) 2.5 wt. % Cu, (c) 5.0 wt. % Cu,
(d) 10.0 wt. % Cu, and (e) 15.0 wt. % Cu. ( + : lattice
plane of γ-Al
2
O

3,
* : lattice plane

of metallic Cu)
141
Figure 5.5
Cu XPS spectrum of (a) 1.0 wt. %, (b) 2.5 wt. %,
(c) 5.0 wt. %, (d) 10.0 wt. % and (e) 15.0 wt. %
Cu/Al
2
O
3
WI-SG catalyst. (dotted lines indicate the
peak maxima detected)
143
Figure 5.6
The Cu LMM Auger peak of (a) 1.0 wt. %,
(b) 2.5 wt. %, (c) 5.0 wt. %, (d) 10.0 wt. % and
(e) 15.0 wt. % Cu/Al
2
O
3
WI-SG catalyst. (dotted
lines indicate the 2 peak maximum observed.)
146
! ! ! !
XIX!
Figure 5.7
TEM images and Cu particle size distribution of (a)
1.0 wt. %, (b) 2.5 wt. %, (c) 5.0 wt. %,

(d) 10.0 wt. %, (e) 15.0 wt. % Cu/Al
2
O
3

148
Figure 5.8
Plot of ion current for CO
2
(m/z= 44) against
temperature for 2.5 wt. % Cu/Al
2
O
3
WI-SG catalyst
(a) without pretreatment; (b) after H
2
pretreatment
for 2 h at 150
o
C; (c) after H
2
pretreatment for 2 h at
300
o
C
149
Figure 5.9
Kinetic profile of protodecarboxylation of 2-
nitrobenzoic acid carried out in the presence of

(♦) Li
2
CO
3
, (■) Na
2
CO
3
, (▲) K
2
CO
3
, (x) Cs
2
CO
3

152
Figure 5.10
Kinetic profile of protodecarboxylation reaction
carried using 10 wt. % Cu/Al
2
O
3
WI and WI-SG
catalyst
153
Figure 5.11
Kinetic profile protodecarboxylation of 2-
nitrobenzoic acid carried using Cu/Al

2
O
3
WI-SG
catalyst with 1.0 wt. % to 15.0 wt. % Cu loading
154
Figure 5.12
Plot of initial rate of reaction (mmol/mmol
cat
h)
against weight loading of copper (%)
154
Figure 5.13
Kinetic profile of protodecarboxylation of 2-
nitrobenzoic acid using (♦) 2.5 wt. % Cu/Al
2
O
3
WI-
SG catalyst without pretreatment; (■) 2.5 wt. %
Cu/Al
2
O
3
WI-SG catalyst after H
2
pretreatment for
2 h at 150
o
C; (▲) 2.5 wt. % Cu/Al

2
O
3
WI-SG
catalyst after H
2
pretreatment for 2 h at 300
o
C
156
Figure 5.14
Optimised structure of Cu
2
O (111) and (100)
surface: (a) side view of Cu
2
O (111) and (b) side
view of Cu
2
O (100). The red, brick red and yellow
spheres represent oxygen, coordinatively saturated
copper (Cu
CSA
) and coordinatively unsaturated
copper (Cu
CUS
) atoms. The white line defines the
uppermost layer.
157
Figure 5.15

Leaching test at 165
o
C - Kinetic profile for the
protodecarboxylation of 2-nitrobenzoic acid carried
out (▲) without hot filtration and (■) with hot
filtration after 0.5 h
163
Figure 5.16
Leaching test at 150
o
C- Kinetic profile of
protodecarboxylation of 2-nitrobenzoic acid carried
out (▲) without hot filtration and (■) with hot
filtration after 2 h
165
! ! ! ! ! ! ! !
XX!
Figure 5.17
Results of multiple reaction runs carried out using
recycled 2.5 wt. % Cu/Al
2
O
3
WI-SG catalyst
165
Figure 5.18
Kinetic profile of 10.0 wt. % Cu/Al
2
O
3

(WI-SG) -
catalysed protodecarboxylation of 2-nitrobenzoic
acid carried out in the presence of air or Ar
166
Figure 5.19
Kinetic profile of 10.0 wt. % Cu/Al
2
O
3
(WI-SG)
catalysed protodecarboxylation of 2-nitrobenzoic
acid carried out under Ar (♦) without oxidant;
(▲) with 10 mol. % K
2
S
2
O
8
; and (■) with 10 mol. %
of NH
4
S
2
O
8

167
Figure 5.20
Leaching test at 150
o

C - Kinetic profile for the
protodecarboxylation of 2-nitrobenzoic acid carried
out in the presence of 10 mol. % K
2
S
2
O
8

(▲) without hot filtration and (■) with hot filtration
after 1 h
168
Figure 5.21
Kinetic profiles of 10.0 wt. % Cu/Al
2
O
3
(WI-SG) –
catalysed protodecarboxylation of 2-nitrobenzoic
acid catalysed by (■) 2.5 mol. %; (♦) 5 mol. %;
(▲) 10 mol. %; (x) 20 mol. %; (□) 100 mol. %; and
(o) 1 equivalent of TEMPO and 10 mol. % K
2
S
2
O
8

169
Figure 6.1

Continuous flow reactor set-up for decarboxylative
cross-coupling
175
Figure 6.2
Proposed mechanism for Pd-catalysed
decarboxylative cross-coupling of heteroaromatic
carboxylic acids and aryl halide
176
Figure 6.3
XRD pattern of 2.5 wt. % Cu · 1.0 wt. % Pd/Al
2
O
3

prepared by (a) sequential impregnation; (b) co-
impregnation; (c) surface activation (*: lattice plane
of CuO, #: lattice plane of γ-Al
2
O
3
)
182
Figure 6.4
TEM images and particle size distributions for 2.5
wt. % Cu !1.0 wt. % Pd/ Al
2
O
3
prepared via
(a) sequential impregnation; (b) co-impregnation;

(c) surface activation
184
Figure 6.5
N
2
adsorption-desorption isotherm of 2.5 wt. % Cu ·
1.0 wt. % Pd/Al
2
O
3
prepared by (a) sequential
impregnation; (b) co-impregnation; (c) surface
activation
185
Figure 6.6
Pore size distribution of 2.5 wt. % Cu · 1.0 wt. %
Pd/Al
2
O
3
prepared by (a) sequential impregnation;
(b) co-impregnation; (c) surface activation
185
! ! ! !
XXI!
Figure 6.7
Cu 2p
3/2
XPS spectra of 2.5 wt. % Cu · 1.0 wt. %
Pd/Al

2
O
3
prepared via (a) sequential impregnation
(SI); (b) co-impregnation (CI); and (c) surface
activation (SA)
188
Figure 6.8
Pd 3d
3/2
XPS spectra of 2.5 wt. % Cu · 1.0 wt. %
Pd/Al
2
O
3
prepared via (a) sequential impregnation
(SI); (b) co-impregnation (CI); and (c) surface
activation (SA)
189
Figure 6.9
HPLC spectrum of a typical test reaction carried out
using potassium 2-nitrobenzoate, iodobenzene,
K
2
CO
3
, 10 wt. % Cu/Al
2
O
3

in DMA at 150
o
C, Ar
212
Figure 6.10
HPLC spectrum of a typical test reaction carried out
using potassium 2-nitrobenzoate, iodobenzene,
K
2
CO
3
, 2.5 wt. % Cu·1.0 wt. % Pd/Al
2
O
3
in DMA at
150
o
C, Ar

212

! ! ! ! ! ! ! !
XXII!
LIST OF SCHEMES

Scheme 1.1
General mechanism of cross-coupling reactions
catalysed by Pd catalyst
20
Scheme 1.2
Ligand-free Pd/C-catalysed Suzuki coupling
22
Scheme 1.3
Cu-catalysed Ullmann homocoupling of iodobenzene
24
Scheme 1.4
Pd/C-catalysed Ullmann coupling of aryl chlorides
24
Scheme 1.5
Proposed mechanism for decarboxylative cross-
coupling
27
Scheme 1.6
Catalytic transformations of carboxylic acids
28

Scheme 1.7
Protodecarboxylation of ortho-substituted benzoic
acids
29
Scheme 1.8
Decarboxylative cross-coupling of ortho-substituted
benzoic acids and bromobenzene in the presence of
Pd and Cu catalyst
29
Scheme 1.9
Mechanism of decarboxylative Heck reaction
30
Scheme 1.10
Direct arylation of 2,6-dimethoxylbenzoic acid
31
Scheme 3.1
Ullmann coupling of aryl halides
64
Scheme 3.2
Homocoupling of bromobenzene catalysed by
Pd(OAc)
2
-PEG system
69
Scheme 3.3
(a) Pd-PEG-EG catalysed homocoupling of
bromobenzene; (b) neutralisation reaction of HBr and
Cs
2
CO

3

80
Scheme 3.4
Pd-catalysed homocoupling of aryl halides using
isopropanol as reductant
85
Scheme 3.5
Reductive homocoupling of aryl halides on
supported Pd catalyst
85
Scheme 3.6
Oxidation of hydroxyl functional group of ethylene
oxide oligomers to aldehyde functional group
85
Scheme 3.7
Proposed mechanism for the Pd-catalysed
homocoupling of bromobenzenes
87
Scheme 3.8
Proposed mechanism for the Pd-catalysed formation
of benzene byproduct
88
! ! ! !
XXIII!
Scheme 3.9
Proposed mechanism for Pd-PEG-EG catalysed
homocoupling of bromobenzene for formation of
terphenyls
89

Scheme 3.10
Proposed intermediate structures for the formation of
ortho- and para- terphenyls
89
Scheme 4.1
Protodecarboxylation of (1) 2-nitrobenzoic acid and
(2) 4-methoxylbenzoic acid using the Cu
2
O/1,10-
phenantroline system
99
Scheme 4.2
Protodecarboxylation of 2-nitrobenzoic acid using
supported Ag catalyst
100
Scheme 4.3
Delocalisation of electrons in (a) DMSO and
(b) DMA
111
Scheme 4.4
Proposed mechanism of protodecarboxylation of
ortho-substituted benzoic acids
129
Scheme 5.1
Cu/Al
2
O
3
-catalysed protodecarboxylation of
2-nitrobenzoic acid

136
Scheme 5.2
Possible reaction mechanisms for proto-
decarboxylation of 2-nitrobenzoic acid via:
(a) anionic pathway and (b) radical pathway
158
Scheme 5.3
(a) Trapping of aryl anion using iodobenzene,
(b) Trapping of aryl radicals using TEMPO
159
Scheme 5.4
Proposed mechanism of Cu/Al
2
O
3
- catalysed
protodecarboxylation of 2-nitrobenzoic acid
161
Scheme 6.1
Decarboxylative cross-coupling of 2-nitrobenzoic
acid and aryl bromides using Cu·Pd catalytic system
174
Scheme 6.2
Decarboxylative cross-coupling of potassium
2-nitrobenzoate and iodobenzene
177
Scheme 6.3
Decarboxylative coupling of 2-nitrobenzoic acid and
iodobenzene (main reaction) and proto-
decarboxylation of 2-nitrobenzoic acids (side

reaction)
191
Scheme 6.4
Proposed mechanism for Cu-catalysed
decarboxylative cross-coupling of potassium
2-nitrobenzoate and iodobenzene
207
Scheme 6.5
Proposed mechanism for bimetallic Cu·Pd catalysed
decarboxylative cross-coupling of potassium
2-nitrobenzoate and iodobenzene
208
! ! ! ! ! ! ! !
XXIV!
Scheme 6.6
Proposed mechanism for formation of 3-NBP
208
Scheme 6.7
Proposed mechanism for formation of DNBP
209

! ! ! !
XXV!
LIST OF JOURNAL PUBLICATIONS & CONFERENCE PAPERS
Journal publication
(1) Protodecarboxylation of carboxylic acids over heterogeneous silver
catalysts
Xiu Yi Toy,

Irwan Iskandar Bin Roslan,

Gaik Khuan Chuah

and
Stephan Jaenicke*
Catalysis Science & Technology (Accepted 30 October 2013)

Conference paper
(1) Novel Catalytic Green Processes for the Syntheses of Conductive
Polymer
Xiu Yi Toy, Stephan Jaenicke*
(Poster Presentation at 6
th
Singapore International Chemical
Conference, 15-18 December 2009, Suntec International Convention
and Exhibition centre, Singapore)

(2) Novel Catalytic Green Processes for the Syntheses of Conductive
Polymer
Xiu Yi Toy, Stephan Jaenicke*
(Poster Presentation at 6
th
Asian-European Symposium on metal
mediated efficient reactions, 7-9 June 2010, Nanyang Technological
University, Singapore)