Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable Ti0.97Pd0.03O1.97 Catalyst

Article abstract of DOI:10.1007/s10562-021-03560-5

Abstract: Facile protocol for the synthesis of biaryls from aryl halides in presence of magnesium metal without prior formation of organometallic intermediate has been exploited. Irrespective of aqueous medium, Ti_0.97Pd_0.03O_1.97 catalyst supports C–C bond formation reaction in presence of metals rather than dehalogenation without any additives. Homocoupling of 16 different aryl halides furnished corresponding biphenyls in good yield with better functional group tolerance. The recovery of the catalyst was carried out by employing catalyst coated cordierite monolith up to 7th cycle with high yields. A new approach for the cross-coupling reaction is also attempted. Graphic Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-021-03560-5

Catalysis Letters
https://doi.org/10.1007/s10562-021-03560-5
Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous
Media with Recyclable Ti Pd O Catalyst
0
.97 0.03 1.97
Prasanna1,2 · Shrikanth K. Bhat · K. M. Usha · M. S. Hegde
1
2
1
Received: 15 December 2020 / Accepted: 7 February 2021
©
The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature 2021
Abstract
Facile protocol for the synthesis of biaryls from aryl halides in presence of magnesium metal without prior formation of
organometallic intermediate has been exploited. Irrespective of aqueous medium, Ti Pd catalyst supports C–C
O
0.03 1.97
0
.97
bond formation reaction in presence of metals rather than dehalogenation without any additives. Homocoupling of 16 diꢀer-
ent aryl halides furnished corresponding biphenyls in good yield with better functional group tolerance. The recovery of the
catalyst was carried out by employing catalyst coated cordierite monolith up to 7th cycle with high yields. A new approach
for the cross-coupling reaction is also attempted.
Graphic Abstract
Keywords Noble metal ionic catalyst · Cordierite monolith · Organometallic intermediate
1
Introduction
The trend has been continuously changing from classical
method for the synthesis of biaryls by Ullmann coupling at
elevated temperature above 200 °C to obtain milder aqueous
conditions [1]. Recent developments such as ligand promoted
couplings reduce the harsh conditions required for the Ull-
mann type coupling. Coupling reactions can be carried by
using ligands like P(Ph) , P(o-tol) and As(o-tol) at mild con-
*
*
K. M. Usha
usha.km@rediꢀmail.com
M. S. Hegde
mshegde@iisc.ac.in
1
2
3
3
3
Talent Development Centre, Indian Institute of Science
Challakere Campus at Kudapura, Chitradurga,
Karnataka 577536, India
ditions [2]. The homogeneous catalysts supported by complex
organic frame works and organic reductants like hydroquinone
will increase the rate of the reaction as well as the selectivity
Department of Chemistry, University College Mangalore,
Chitradurga, Karnataka 575001, India
Vol.:(0
1
123456789)
3

Prasanna et al.
[
2–4]. But isolation of the desired products is diꢁcult and also
2 Experimental
includes loss of expensive ligands.
Ever since Makato Kumada showed formation of biaryls
from organomagnesium compounds and aryl halides with
metal catalysts, coupling reactions in presence of organoz-
inc, organosilicon and organotin compounds were reported
in contrast with Kumada coupling [5–9]. In organometallic
compounds, metal is electropositive and aryl moiety is electron
negative. So, aryl moiety attacks aryl halide very easily and
increases the rate of coupling reaction. But feasibility of these
reactions in aqueous condition was considered to be impos-
sible. These reactions should be carried in anhydrous condi-
tions due to moisture sensitive organometallic compounds.
So, in situ formation of organometallic compounds in aqueous
phase by using metals has got importance in coupling reactions
2.1 Synthesis, Coating and Characterization
of the Catalyst
Synthesis, characterization and coating method of
Ti Pd
O
catalyst over cordierite monolith hon-
0
.97
0.03 1.97
eycomb were reported in earlier studies [27–29]. Brieꢂy,
Al(NO ) (3.751 g, 10 mmol) and glycine (1.246 g,
3
3
16.6 mmol) were dissolved in 40 mL of water. Honeycomb
was dipped and kept for combustion in pre-heated muf-
ꢂed furnace at 400 °C. The procedure was repeated to load
γ-Al O up to 2–3% of honeycomb weight. This method is
2
3
called as wash coating which helps to increase the surface
area and adhesion to the catalyst. After this, titanium iso-
[
10]. But in these reactions, dehalogenation of aryl halides
propoxide (2.757 g, 9.7 mmol), PdCl (0.053 g, 0.3 mmol)
2
was found to be major product because metal having nega-
tive reduction potential displaces hydrogen gas from water.
This can be ruled out to the higher extent by using π-acids
like formaldehyde, acetonitrile, ethyl formate and DMF. But it
leads to the side reactions such as formylation reaction which
is also feasible in the similar reaction condition [11]. There-
fore, there is a need for better catalysts which can tackle these
complexities.
and glycine (0.808 g, 10.77 mmol) were dissolved in 25 mL
of water. A piece of pre-weighed γ-Al
O coated monolith
2
3
was dipped in the solution and kept in the muꢃed furnace
at 350 °C for combustion. Then monolith was cooled and
kept for sonication in water to remove loosely held parti-
cles. The monolith was dried and weighed. This procedure
was repeated to get desired weight of catalyst to be coated.
X-ray diꢀraction patterns were recorded on a Bruker X-ray
diꢀractometer at a scan rate of 0.02°/s with a step size in the
Hedge et al. developed a new series of metal oxide sup-
ported noble metal ionic catalysts by solution combustion
method [12–21]. Among those, palladium metal ion substi-
2
θ range between 10° and 85° to conꢄrm the catalyst phase
formation. There are no Pd or PdO peaks in the X-ray dif-
fraction pattern which conꢄrmed that Pd ion has substituted
tuted TiO was found to be unique in contrast with normal
2
palladium metal-based catalysts such as Pd/C and PdCl
in the TiO lattice.
2
2
4+
2+
[
22,23]. Only 3% of Ti in TiO substituted by Pd forms
2
single phase Ti Pd
O
catalyst crystallizing in anatase
0
.97 0.03 1.97
2+
phase. This catalyst is non-toxic and highly stable with Pd
2.2 General Procedure for Homocoupling Reaction
ion as electrophilic site and oxide ion vacancy as nucleophilic
2
+
site. Pd substituted TiO in form of stoichiometric oxide
234 mg of 4-methoxyiodobenzene (1 equiv., 1 mmol) and
100 mg of Mg powder (4 equiv., 4 mmol) were taken in
screw cap vial with catalyst coated cordierite monolith, sus-
pended in 4 mL of water and reꢂuxed. Completion of the
reaction was checked with TLC and extracted with diethyl
ether. Anhydrous sodium sulphate was added to organic
layer to remove trace amount of water and ꢄltered. Solvent
was evaporated in rotary evaporator. Product obtained was
puriꢄed by column chromatography by taking 5% Ethyl
acetate in petroleum ether as eluent. All isolated products
2
Ti Pd O where x=0.03 showed excellent catalytic activ-
1−x
x
2−x
ity in Heck coupling, oxidative C–C bond formation reactions
and Suzuki coupling reactions [24–26]. To extend the appli-
cation of this catalyst in organic synthesis, we developed an
easier protocol for the synthesis of biaryls from aryl halides. In
this paper we report, facile methods to the synthesize biaryls
employing this catalyst with base or magnesium metal in aque-
ous media. The rate of coupling reactions has been compared
with various metals. Ti Pd O catalyst coated cordierite
1−x
x
2−x
1
13
monolith can be reused after each cycle then avoiding handling
of powder catalyst. An approach for the cross-coupling reac-
tion is also attempted.
were characterized by H NMR and C NMR.
1
3

Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable…
3
Results and Discussions
as well as metal is needed for coupling. Without any one of
them, there is no coupled product (Table 1, entry 18 and 20).
This reaction was carried out in THF as solvent gave trace
amount of coupled product (Table 1, entry 19). Instead of
powder catalyst, Ti0.97Pd0.03O1.97 coated cordierite mono-
lith was used along with magnesium aꢀorded 100% yield in
1 h (Table 1, entry 21). Therefore, the optimized condition
for obtaining biaryls was Ti0.97Pd0.03O1.97 catalyst coated
cordierite monolith with excess magnesium metal powder
in water at reꢂux temperature.
3.1 Screening Studies for Homocoupling Reaction
For screening studies, 4-methoxyiodobenzene (1 equiv.) was
chosen as a model substrate in water along with powder
catalyst. The results of base screening for homocoupling
reaction of aryl halide in presence of only base are given
in Table 1. Reactions in presence of sodium hydroxide and
caesium carbonate furnished 2a in 30% and 35% yields,
respectively (Table 1, entry 1 and 2). But, to our delight,
in presence of K CO and NEt yields were 99% (Table 1,
3.2 Homocoupling of Various Aryl Halides
2
3
3
3
and 4). Triethyl amine has characteristic ammonia like
odour and it is hazardous [30]. Bases like aqueous ammonia,
diethylamine, pyrollidine, piperidine and sodium tert-butox-
ide were showing lesser activity in homocoupling reaction
Substrate scope was carried in water in presence of magne-
sium metal with honeycomb coated Ti0.97Pd0.03O1.97 cata-
lyst (Table 2). Comparatively, aryl iodides show higher rate
of coupling than aryl bromide analogues. Despite having
electron donating and electron withdrawing groups, every
substrate has shown high yield of homo-coupled product.
The homocoupling reactions of 4-methoxyiodobenzene
and 4-methoxybromobenzene furnished biaryl derivative
2a in 99% and 90% yield, respectively (Table 2, entry 1
and 2). The reaction of unsubstituted aryl halides such as
iodobenzene, bromobenzene and chlorobenzene proceeded
well furnishing the product 2b in 95%, 80% and 45% yield,
respectively (Table 2, entry 3–5). Derivatives of aniline such
as 4-iodoaniline and 4-bromoaniline aꢀorded the product
2c with 96% and 85% yield, respectively in homocoupling
reactions (Table 2, entry 6 and 7). The reactions of ꢂuoro-
substituted substrates like 4-iodoꢂuorobenzene and 4-bro-
moꢂuorobenzene gave corresponding biphenyl 2d in 92%
and 80% yield, respectively (Table 2, entry 8 and 9). The
homocoupling of 4-iodobenzonitrile converted into biaryl
derivative 2e in 70% yield (Table 2, entry 10). The cou-
pling reaction of methyl substituted aryl halides such as
3-methyliodobenzene and 3-methylbromobenzene gave 2f
as well as 2-methyliodobenzene and 2-methylbromobenzene
aꢀorded 2 g in 92%, 83%, 90% and 82% yield, respectively
(Table 2, entry 11–14). Homocoupling of 3-chloroiodoben-
zene proceeded smoothly furnishing the product 2 h with
94% yield in 2 h (Table 2, entry 15). Biphenyl derivative
2i was obtained from coupling of 3,4-dichloroiodobenzene
with 93% yield in 3 h (Table 2, entry 16).
(
Table 1, entry 5–9). Therefore, optimized reaction condition
for Ullmann type coupling reaction is K CO as base with
2
3-
Ti Pd
O
catalyst in water.
0
.97
0.03 1.97
Although, the reaction in presence of K CO furnished
2
3
2
a in 100% yield, time required for the completion of the
reaction was 16 h. In order to reduce the reaction time, we
performed next set of screening reactions with metals. Cou-
pling reaction terminates in 3 h with zinc and 1.5 h with
magnesium metal powder, furnished 2a above 99% yields
(
Table 1, entry 10–11). We found drastic increase in rate of
the reaction compared to the coupling reaction in presence
of only base without metal. Therefore, base is not needed
if we add Mg metal in coupling reaction (Table 1, compare
entry 11 and 12). The same reaction was carried in pres-
ence of MgO instead of magnesium metal powder which was
unsuccessful (Table 1, entry 13). This indicates that high
rate of coupling occurs only in presence of metal. There-
fore, we suspected there may be formation of organometallic
intermediates and literature also conꢄrms the same [11]. So,
reaction mechanism resembles that of Kumada and Negishi
coupling reaction pathway with magnesium and zinc metal
powder respectively [31,32].
The magnesium metal in water enhances hydrogenolysis
of aryl halide in presence of palladium acetate catalyst [11].
Earlier studies suggest that the addition of π-acids like for-
maldehyde enhances coupling, which is again leads to the
side reactions like formylation. Therefore, Ti Pd O
0.03 1.97
0
.97
catalyst extensively supports coupling reaction rather than
dehalogenation in water with metal powder. The coupling
reaction was carried out in presence of π-acids like formal-
dehyde, acetonitrile, dimethyl formamide and ethyl formate
furnished 2a in 99% yields (Table 1, entry 14–17). This indi-
cates, π-acids do not alter the rate of reaction. Both catalyst
3.3 Reactivity of Various Metals in Homocoupling
Reaction and Recycling of the Catalyst
Coupling reaction of 4-methoxyiodobenzene proceeded
well with magnesium metal in 1.5 h to complete the reaction
1
3

Prasanna et al.
Table 1 Screening studies for homocoupling reactiona
Ti . Pd . O .
0 03 1 97
CH3
0
97
O
I
O
O
H C
H C
3
3
2
a
Entry
Metal
Base
π-acid
Time (h)
16
Yield (%)
30
1
2
3
4
5
6
7
-
-
-
-
-
-
-
NaOH
-
-
-
-
-
-
-
2
Cs CO
3
16
35
K
2
CO
3
16
>99
NEt
3
16
>99
NH
3
16
Trace
Trace
10
NHEt
2
16
H
N
16
8
-
-
16
Trace
N
H
9
-
tert – BuONa
-
16
3
Trace
>99
10
11
12
13
14
Zn
Mg
Mg
-
-
-
-
-
1.5
1.5
12
>99
K
2
CO
3
-
-
>99
MgO
Trace
Mg
Mg
-
-
HCHO
1.5
1.5
99
99
15
16
17
18
19
20
21
CH
DMF
HCO Et
3
CN
Mg
Mg
Mg
Mg
-
-
-
-
-
-
-
1.5
1.5
12
12
12
1
99
2
99
-
-
-
-
Traceb
Tracec
Trace
100d
Mg
a
Reaction conditions: 0.5 mmol substrate, 2 mmol metal powder, 10 mg powder catalyst, 2 mmol of π-acid, 1 mmol base, 2 mL water and
b
c
d
1
00 °C. All are isolated yields. Without catalyst, THF as solvent. 10 mg catalyst cartridge
1
3

Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable…
Table 2 Homocoupling of aryl halides in optimized reaction condition
Ti . Pd . O .
0
97
0 03 1 97
R
X
o
R
1
Mg, H O, 100 C
R
2
2
Entry
1
Substrate
Product
Time (h)
1
Yield
99
H C
3
O
I
H C
3
O
O
H C
2
3
CH3
2
90
O
Br
2
a
3
4
5
6
7
1.5
2
95
80
45
96
85
I
Br
Cl
4.5
2
2
b
H N
I
2
H N
NH2
2
3.5
H N
Br
2
2
c
8
9
2
3
92
80
F
F
I
F
F
Br
I
2d
10
3
70
NC
NC
CN
2e
1
3

Prasanna et al.
Table 2 (continued)
H C
1
1
3
2.5
4
92
83
I
H C
3
H C
1
2
3
CH3
Br
2f
CH3
1
3
2.5
4.5
90
82
I
CH3
CH3
H C
3
Br
1
1
4
5
2g
Cl
Cl
Cl
2
3
94
93
I
Cl
2h
Cl
16
Cl
I
Cl
Cl
Cl
2i
Reaction conditions: 1 mmol substrate, 4 mmol Mg powder, 20 mg catalyst cartridge, 4 mL water and 100 °C. All are isolated yields
whereas with zinc metal that was 3 h. So, there will be a clue
for diꢀerent rates of coupling reactions with various metals.
Therefore, we performed coupling reactions with various
metals with same reaction conditions as that of in magne-
sium. Percentage yield of product obtained in an hour for
each metal was considered and results are shown in Fig. 1.
Iron, zinc, aluminium and manganese aꢀorded moderate
yields in coupling reactions as compared to magnesium [33].
Chromium, cobalt, antimony and silicon gave lesser yields
but reactions in presence of tin and copper were unsuccess-
ful. Percentage yield obtained when reaction was carried
only in presence of K CO in 2 h was 15% whereas addition
2
3
1
3

Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable…
3.4 Scope for Cross‑Coupling Reactions
Cross-coupling reactions were carried under optimized reac-
tion conditions and results are given in Table 3. Reaction
of 4-methoxyiodobenzene with iodobenzene proceeded fur-
nishing the cross-coupled product 2ab in 50% yield (Table 3,
entry 1). Because of the competition towards the homocou-
pling reaction in both the substrates are almost same. But in
the case of the coupling reaction of 4-methoxyiodobenzene
with bromobenzene and 4-bromoꢂurobenzene, aꢀorded
only the cross-coupled products 2ab and 2ad with 96%
and 95% yield, respectively in 1 h (Table 3, entry 2 and
4
). Reaction of 4-methoxybromobenzene with iodobenzene
and 4-ꢂuoroiodobenzene aꢀorded 2ab and 2ad with 94%
yield each (Table 3, entry 3 and 5). Cross-coupled product
Fig. 1 Percentage yield of coupled product with diꢀerent metals in
h and reusability of catalyst with magnesium metal
2
aj was obtained by the coupling of 4-methoxyiodobenzene
1
with 1-bromonaphthalele with 60% yield (Table 3, entry 6).
Cross-coupling reaction of iodobenzene with 2-bromonaph-
thalene furnished the product 2bk with 62% yield (Table 3,
entry 7). The required time in cross-coupling reaction resem-
bles that of homocoupling of the aryl iodide in the reaction.
This indicates that the cross-coupling reaction can be carried
eꢀectively by employing aryl iodides with aryl bromides.
of Sn metal increased the rate of reaction to 70%, which is
signiꢄcant. When the coupling reaction was carried at room
temperature, trace amount of yield was observed in 1 h. In
alkaline condition, reaction mixture was reꢂuxed for 16 h to
complete the reaction, whereas in presence of magnesium
metal reaction time reduced to 1 h. Therefore, we suspect
there will be in situ formation of organometallic intermedi-
ate in presence of excess magnesium metal which drastically
increases the rate of coupling.
3.5 Reaction Mechanism of the Coupling Reaction
Recycling of the catalyst was carried by employing cata-
lyst coated cordierite monolith with 1 mmol of 4-methox-
yiodobenzene in each cycle. Catalyst coated cartridge was
suspended in screw cap tube containing reaction mixture.
After the reaction, catalyst cartridge was washed with dis-
tilled water to remove inorganic impurities followed by
n-hexane to remove organic residues. Then the cartridge
was sonicated for half an hour to remove loosely held par-
ticles followed by wash with deionised water. Catalyst was
activated by heating at 350 °C in the furnace for the next
run. The catalyst was recycled for 7 cycles without much
increase in the reaction time with good yield of coupled
product.
Proposed mechanism of coupling reaction is depicted in
Scheme 1. In the ꢄrst step, oxidative addition of aryl hal-
ide forms an organopalladium complex A. In the next step,
organomagnesium complex formed from aryl halide with
excess magnesium metal interacts with complex A resulting
the formation of complex B. Finally, reductive elimination of
the complex B yields homocoupled product and the catalyst
recovers for next run. In case of cross-coupling, aryl iodide
is favoured to form complex A in oxidative addition and
aryl bromide forms organomagnesium complex. So, oxida-
tive addition is the rate determining step. Therefore, reac-
tion time for cross-coupling reaction resembles as that of
homocoupling of aryl iodide.
1
3

Prasanna et al.
Table 3 Cross-coupling reaction of aryl halides in optimized reaction condition
Entry
Aryl halides
Product
Time (h)
Yield
%)
(
1
2
3
4
5
1
1
50
96
94
95
94
I
O
I
Br
O
2ab
1.5
1
O
Br
I
I
O
Br
I
F
O
F
2
O
Br
F
2ad
6
1
60
O
I
Br
O
2aj
Br
7
1.5
62
I
2bk
Reaction conditions: 0.5 mmol aryl iodide, 0.55 mmol aryl bromide, 4 mmol Mg powder, 20 mg catalyst coated cartridge, 4 mL water and
00 °C. All are isolated yields
1
4
Conclusion
several cycles. An approach for the cross-coupling reaction
is also attempted with good yields.
In summary, we have developed a facile protocol for the
Supplementary Information The online version contains supplemen-
synthesis of biaryls with Ti Pd
O
catalyst. This
0
.97
0.03 1.97
tary material available at https://doi.org/10.1007/s10562-021-03560-5.
catalyst is compatible with aqueous and aerobic conditions.
Important features of the catalyst in this coupling reaction
are, non-toxic, easy to handle, easy to recover and reused for
1
3

Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable…
1
1
1. Bhattacharjya A, Klumphu P, Lipshutz BH (2015) Kumada-Grig-
nard-type biaryl couplings on water. Nat Commun 6:7401
Pd
PhX
O
O
2. Bera P, Patil KC, Jayaram V, Subbanna GN, Hegde MS (2000)
Ph-Ph
Ionic dispersion of Pt and Pd on CeO by combustion method:
2
eꢀect of metal-ceria interaction on catalytic activities for NO
reduction and CO and hydrocarbon oxidation. J Catal 196:293
3. Hegde MS, Patil KC, Madras G (2009) Noble metal ionic cata-
lysts. Acc Chem Res 42:704
1
1
1
1
Ph
Ph
O
4. Bera P, Hegde MS (2010) Recent advances in auto exhaust
catalysis. J Indian Inst Sci 90:299
X
Ph
O
Pd
Pd
5. Bera P, Hegde MS (2011) NO reduction over noble metal ionic
catalysts. Catal Surv Asia 15:181
O
O
B
A
6. Hedge MS, Bera P (2015) Noble metal ion substituted CeO
2
catalysts: electronic interaction between noble metal ions and
CeO lattice. Catal Today 253:40
2
1
7. Singh P, Hegde MS (2008) Controlled synthesis of nanocrys-
talline CeO and Ce M O (M = Zr, Y, Ti, Pr and Fe) solid
PhMgX
PhX + Mg
MgX2
2
1−x
x
2−δ
solutions by the hydrothermal method: structure and oxygen
storage capacity. J Solid State Chem 181:3248
Scheme 1 Plausible mechanism of coupling reaction
1
1
2
8. Singh P, Hegde MS, Gopalakrishnan J (2008) Ce /3Cr /3O +y: a
2
1
2
new oxygen storage material based on the ꢂuorite structure. Chem
Mater 20:7268
Compliance with Ethical Standards
9. Singh P, Hegde MS (2009) Ce Ru O (x=0.05, 0.10): a new
1
−x
x
2−δ
high oxygen storage material and Pt, Pd-free three-way catalyst.
Conflicts of interest The authors declare that there is no conꢂict of
Chem Mater 21:3337
interest.
0. Roy S, Hegde MS, Ravishankar N, Madras G (2007) Creation of
2
+
redox adsorption sites by Pd ion substitution in nanoTiO for
2
high photocatalytic activity of CO oxidation, NO reduction, and
NO decomposition. J Phys Chem C 111:8153
2
1. Roy S, Hegde MS, Sharma S, Lalla NP, Marimuthu A, Madras G
References
(
2008) Low temperature NO and N O reduction by H : mecha-
x 2 2
nism and development of new nano-catalysts. Appl Catal B
84:341
1
2
.
.
Ullmann F, Bielecki J (1901) Ueber Synthesen in der Biphenyl-
reihe. Chem Ber 34:2174–2185
22. Mukri BD, Dutta G, Waghmare UV, Hegde MS (2012) Activation
2
+
Hennings D, Iwama T, Rawal VH (1999) Palladium-catalyzed
of lattice oxygen of TiO by Pd ion: correlation of low-tempera-
2
(
Ullmann-type) homocoupling of aryl halides: a convenient and
ture CO and hydrocarbon oxidation with structure of Ti Pd O
1–x
x
2–x
general synthesis of symmetrical biaryls via inter- and intramo-
lecular coupling reactions. Org Lett 1:1205–1208
(x=0.01–0.03). Chem Mater 24:4491
23. Mukri BD, Waghmare UV, Hegde MS (2013) Platinum ion-doped
2
4+
+
3
4
.
.
Alonso F, Riente P, Yus M (2008) Homocoupling of aryl iodides
promoted by nickel (0) nanoparticles. Arch Org Chem 4:8–15
Courtois V, Barhdadi R, Troupel M, Perichon J (1997) Electrore-
ductive coupling of organic halides in alcoholic solvents. An
example: the electrosynthesis of biaryls catalysed by nickel-2,2′
bipyridine complexes. Tetrahedron 53(34):1569–1576
TiO : high catalytic activity of Pt with oxide ion vacancy in
2
4
4
+
+
2+
4+
Ti
Ti
Pt
O
compared to Pt without oxide ion vacancy in
1
1
−x
−x
x
2−x
Pt O . Chem Mater 25:3822
x
2
24. Bhat KS, Prasad DJ, Hegde MS (2019) Recyclable Pd ionic cata-
lyst coated on cordierite monolith for high TOF Heck coupling
reaction. J Chem Sci 131(3):20
5
6
7
.
.
.
Tamao K, Sumitani K, Kumada M (1972) Selective carbon-car-
bon bond formation by cross-coupling of grignard reagents with
organic halides. Catalysis by Nickel-Phosphine complexes. J Am
Chem Soc 94:4374–4376
25. Bhat KS, Prasanna, Prasad DJ, Hegde MS (2020) Palladium ion
catalysed oxidative C-C bond formation reactions in arylboronic
acid: application of cordierite monolith coated catalyst. Catal Lett
150:2911–2927
Negishi E, King AO, Okukado N (1977) Highly general stereo-,
regio-, and chemo-selective synthesis of terminal and internal
conjugated enynes by the Pd-catalysed reaction of alkynylzinc
reagents with alkenyl halides. J Org Chem 42:1821–1823
Hatanaka Y, Hiyama T (1988) Cross-coupling of organosi-
lanes with organic halides mediated by palladium catalyst and
tris(diethylamino)sulfonium diꢂuorotrimethylsilicate. J Org Chem
26. Bhat KS, Lanke V, Prasad DJ, Prabhu KR (2020) Ligand-free
Suzuki coupling reaction with highly recyclable ionic palladium
catalyst Ti Pd O (x=0.03). Appl Catal A Gen 596:117516
1
−x
x
2−x
27. Patil KC, Hegde MS, Rattan T, Aruna ST (2008) Chemistry of
nanocrystalline oxide materials: combustion synthesis, properties
and applications. World Scientiꢄc, Singapore
28. Bera P, Hegde MS (2015) Noble metal ions in CeO and TiO :
2
2
5
3:918–920
synthesis, structure and catalytic properties. RSC Adv 5:94949
8
9
.
.
Stille JK (1986) The palladium-catalyzed cross-coupling reactions
of organotin reagents with organic electrophiles. Angew Chem Int
Ed Engl 25:508–524
29. Sanjaykumar SR, Mukri BD, Patil S, Madras G, Hegde MS (2011)
Recyclable, ligand free palladium(II) catalyst for Heck reaction. J
Chem Sci 123:47–54
Kumada M (1980) Nickel and palladium complex catalyzed cross
coupling reactions of organometallic reagents with Organic hal-
ides. Pure Appl Chem 52:669–679
30. Lynch DW, Moorman WJ, Lewis TR, Stober P, Hamlin RD, Schueler
RL (1990) Subchronic inhalation of triethylamine vapor in Fis-
cher-344 rats: organ system toxicity. Toxicol Ind Health 6:403–414
31. King AO, Okukado N, Negishi E (1977) Highly general stereo-,
regio-, and chemo-selective synthesis of terminal and internal
conjugated enynes by the Pd-catalysed reaction of alkynylzinc
1
0. Krasovskiy A, Duplais C, Lipshutz BH (2009) Stereoselective
Negishi-like couplings between alkenyl and alkyl halides in water
at room temperature. J Am Chem Soc 131:15592–15593
1
3

Prasanna et al.
reagents with alkenyl halides. J Chem Soc Chem Commun
Publisher’s Note Springer Nature remains neutral with regard to
0
:683–684
jurisdictional claims in published maps and institutional aꢁliations.
3
3
2. Huo S (2003) Highly eꢁcient, general procedure for the prepara-
tion of alkylzinc reagents from unactivated alkyl bromides and
chlorides. Org Lett 5:423–425
3. Gosmini C, Ernst CB, Durandetti M (2009) Synthesis of func-
tionalized 2-arylpyridines from 2-halopyridines and various aryl
halides via a nickel catalysis. Tetrahedron 65:6141–6146
1
3