Synthesis of 3-aroylimidazo[1,2-a]pyridines via CuCl2 catalyzed tandem dual carbon-nitrogen bonding

Article abstract of DOI:10.1016/j.tet.2014.09.067

A novel tandem approach has been demonstrated for the direct synthesis of bioactive 3-aroylimidazo[1,2-a]pyridines from chalcones and 2-aminopyridines. The reported tandem reaction is atom-economical and expected to proceed via 1,4-Michael addition follow

Full text of DOI:10.1016/j.tet.2014.09.067

Accepted Manuscript
Synthesis of 3-Aroylimidazo[1,2-a]pyridines via CuCl Catalyzed Tandem Dual
2
Carbon-nitrogen Bonding
Pinku Kaswan, Kasiviswanadharaju Pericherla, Rajni kant, Anil Kumar
PII:
S0040-4020(14)01370-2
10.1016/j.tet.2014.09.067
TET 26041
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 10 July 2014
Revised Date: 19 September 2014
Accepted Date: 22 September 2014
Please cite this article as: Kaswan P, Pericherla K, kant R, Kumar A, Synthesis of 3-
Aroylimidazo[1,2-a]pyridines via CuCl Catalyzed Tandem Dual Carbon-nitrogen Bonding, Tetrahedron
2
(2014), doi: 10.1016/j.tet.2014.09.067.
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ACCEPTED MANUSCRIPT
Graphical Abstract
Synthesis of 3-Aroylimidazo[1,2-a]pyridines
via CuCl2 Catalyzed Tandem Dual Carbon-
nitrogen Bonding
Leave this area blank for abstract info.
Pinku Kaswan,a Kasiviswanadharaju Pericherla,a Rajnikantb and Anil Kumara,*
aDepartment of Chemistry, Birla Institute of Technology and Science, Pilani, 333031, India, bDepartment of
Physics, University of Jammu, Jammu Tawi 180006, India

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Synthesis of 3-Aroylimidazo[1,2-a]pyridines via CuCl2 Catalyzed Tandem Dual
Carbon-nitrogen Bonding
Pinku Kaswan,a Kasiviswanadharaju Pericherla,a Rajnikantb and Anil Kumara,
aDepartment of Chemistry, Birla Institute of Technology and Science, Pilani, 333031, India,
bDepartment of Physics, University of Jammu, Jammu Tawi 180006, India
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A novel tandem approach has been demonstrated for the direct synthesis of bioactive 3-
aroylimidazo[1,2-a]pyridines from chalcones and 2-aminopyridines. The reported tandem
reaction is atom-economical and expected to proceed via 1,4-Michael addition followed by
copper catalyzed oxidative C−N bonding. Catalytic amount of copper was found to be crucial
for the success of tandem reaction and it altered the reaction pathway to furnish entirely new
products. This protocol proved to be convenient as reaction proceeds smoothly without the
necessity of any ligand in the presence of air as oxidant.
Available online
Keywords:
Tandem reaction
Dual C-N bonding
3-Aroylimidazo[1,2-a]pyridines
Chalcone
2009 Elsevier Ltd. All rights reserved
.
2-Aminopyridine
1. Introduction
acylation was unsuccessful so 3-aroylimidazo[1,2-a]pyridines
were synthesized in three steps; a) formylation of imidazo[1,2-
a]pyridines, b) Grignard reaction of 3-formylimidazo[1,2-
a]pyridines and c) oxidation (Scheme 1).7 The Ila group has
reported an efficient synthesis of 2-methylthio/alkoxy/amino-3-
acyl-imidazo[1,2-a]pyridines by copper catalyzed ring closure.31
Recently, Zhang et al. reported an excellent method for the
synthesis of 2-alkenylimidazo[1,2-a]pyridines via copper
catalyzed aerobic oxidative cyclization of methyl vinyl ketones
(1, R = CH3) and 2-aminopyridines (2) (Scheme 1).32 In spite of
the efforts, reports for the synthesis of 3-aroylimidazo[1,2-
a]pyridines (3)33,7,34 under ligand/additive-free aerobic conditions
are rare.35 Thus, there is an intrinsic need to develop a
straightforward method for the synthesis of these biologically
significant structures.
Imidazo[1,2-a]pyridines are the privileged structural motifs with
endowed applications in multidisciplinary fields such as material
science, organometallics, predominantly in medicinal chemistry.1-
6
These scaffolds are the key structures in many natural products
and in commercially available drugs such as zolpidem, alpidem,
necopidem, and saripidem (Figure 1). Furthermore, analogues of
imidazo[1,2-a]pyridines were also studied against broad
spectrum of biological targets.7-12 Because of their diverse
applications, synthesis and functionalization of imidazo[1,2-
a]pyridines is the subject of current interest in many
laboratories.13-29
Fig. 1 Bio-active imidazo[1,2-a]pyridine derivatives.
The biological activities of imidazo[1,2-a]pyridines has proved to
be greatly dependent on substituents at the C-2 and C-3 positions.
For example, 3-aroylimidazo[1,2-a]pyridines have been studied
as anticancer and antitumor agents.7,30 Direct functionalization of
imidazo[1,2-a]pyridines with aroyl chloride via Friedel-Crafts
———
Scheme 1 Reactions of chalcones with 2-aminopyridines and synthesis
of 3-aroylimidazo[1,2-a]pyridines.
Corresponding author. Tel.: +91-1596-515652; fax: +91-1596-244183; e-mail: anilkumar@pilani.bits-pilani.ac.in

2
Tetrahedron
ACCEPTED MANUSCRIPT
for the tandem cyclization. It was realized that Sc(OTf)3, TFA,
Transition metal catalyzed cross coupling reactions are of
and AcOH were completely ineffective for this transformation
while in case of BF3.Et2O, traces of 3a was observed (Table 1,
entries 10-13). These results indicated that the copper catalyst
was crucial for the success of the tandem cyclization. With
CuCl2.2H2O as the optimum catalyst, we further focussed on
finding the effect of solvent for the tandem process. Excitingly,
toluene was proved to be an ideal choice among the solvents
investigated, while other solvents were proved to be less effective
for the tandem cyclization (Table 1, entries 14-18). Subsequently,
effect of catalyst loading was also investigated. With increasing
CuCl2.2H2O loading from 10 mol % to 30 mol % there was slight
improvement in the yield of 3a (Table 1, entries 20-21).
However, decreasing CuCl2.2H2O loading from 10 mol % to 5
mol % resulted in reduction of the yield of 3a to 50% (Table 1,
entry 22). It should be noted that the same reaction under
microwave irradiation resulted Michael adduct (4a) as a major
product (Table 1, entry 23).
utmost importance and an ever growing part of the arsenal of
useful synthetic tools available in modern organic chemistry.36-38
Highly abundant and inexpensive copper salts have been
employed to a great extent as effective catalysts for these
sequential bond forming step-economy reactions.39 The recent
developments in copper catalyzed C−C and C−heteroatom bond
forming reactions40 have attracted the attention of the synthetic
community to revisit the classical routes for revitalization as well
as to construct the novel libraries for biological screenings. With
the multiple reactive sites, chalcones have been proven to be
important organic scaffolds. Particularly, copper catalyzed
oxidative cyclizations of chalcones delivered a variety of
heterocycles with high regioselectivities.41,42 In the pursuit of our
ongoing interest for the synthesis and functionalization of
imidazo[1,2-a]pyridines,43,44,13,45-47 herein we wish to disclose our
recent findings for the synthesis of 3-aroylimidazo[1,2-
a]pyridines (3) via copper catalyzed tandem reaction between
Table 1 Optimization of reaction conditionsa
chalcones
(1-aryl-3-arylprop-2-en-1-one)
(1)
and
2-
aminopyridines (2) (Scheme 1). The reported novel tandem
approach is practical and expected to proceed via initial 1,4-
Michael addition followed by copper catalyzed oxidative C−N
bond formation to provide medicinally important 2-aryl-3-
aroylimidazo[1,2-a]pyridines in one step.
Entry
1
2
3
4
5
6
7
8
Catalyst
CuI
CuBr2
Cu(OTf)2
Cu(OAc)2
CuO
CuOTf
CuCl2.2H2O
CuBr
Solvent
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
benzene
DMF
Yield (%)b
14
2. Results and discussion
60
76
We envisioned that the reaction between chalcones and 2-
aminopyridines in the presence of a copper catalyst could lead to
the formation of 2-aryl-3-aroylimidazo[1,2-a]pyridines by
oxidative cyclization, which could be a potential alternative for
the synthesis of these motifs, as Friedel-Crafts aroylations of
imidazo[1,2-a]pyridines were unsuccessful.7 We were astonished
to notice that Goswami and co-workers have already reported the
reaction between these precursors, which resulted in exclusive
formation of 1,8-naphthyridines via ring closure condensation
followed by spontaneous aromatization with microwave
assistance (Scheme 1).48 Despite this report, a model reaction has
been conducted using 1,3-diphenylprop-2-en-1-one (1a) and 2-
aminopyridine (2a) in presence of catalytic amount of copper
iodide in toluene at 120 °C for 12 h (Table 1). To our delight,
expected 2-phenyl-3-benzoylimidazo[1,2-a]pyridine (3a) was
isolated in 14% yield. Interestingly, neither the Michael adduct
(4a) nor the 1,8-naphthyridine derivative were detected in the
reaction under these conditions. The structure of 3a was
elucidated by IR and NMR spectroscopic data. In the IR
spectrum of 3a, a strong peak appeared at 1597 cm-1 for C=O
(stretching) and in the 1H NMR spectrum a characteristic doublet
appeared at δ 9.55 for the C-5 proton and the carbonyl carbon
appeared at δ 187.36 along with all other expected carbons in the
13C NMR spectrum. The HRMS of 3a displayed a peak at
299.1184 for [M+H]+, further confirming the structure of the
product.
67
45c
34
81
traces
traces
NRd
NRd
NRd
traces
15
14
44
32
40
9
CuSO4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Sc(OTf)3
CF3CO2H
CH3CO2H
BF3.Et2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
CuCl2.2H2O
THF
1,4-dioxane
MeCN
toluene
toluene
toluene
toluene
toluene
60
82e
87f
50g
54c,h
a
Reagents and conditions: 1a (1.0 mmol), 2a (1.2 mmol), catalyst (10
mol %), solvent (5 mL), 120 °C, 12 h, ambient air.
b Isolated yields.
c Yield corresponds to 4a (1,4-Michael adduct, 1,3-diphenyl-3-(pyridin-
2-ylamino)propan-1-one.
d No reaction.
With these results in hand, we further undertook the
optimization of reaction condition by varying catalysts in
conjunction with different solvents for the tandem reaction
(Table 1). After screening a set of different copper catalysts for
the synthesis of 3a, CuCl2.2H2O was found to give the highest
yield (81%) of tandem product 3a (Table 1, entry 7). Among
other copper salts screened, CuBr2, Cu(OTf)2, Cu(OAc)2 and
CuOTf resulted in moderate to good yields of 3a, whereas only
Michael adduct (4a) was obtained in the case of CuO (entries 2-
6). CuBr and CuSO4 produced only traces of 3a with major
amount being unreacted substrates (entries 8-9). With an
ambiguity, some Lewis as well as Bronsted acids were screened
e 20 mol % of catalyst was used.
f 30 mol % of catalyst was used.
g 5 mol % of catalyst was used. hMW (120 °C, 30 min, 250 psi, 300 W).
The standardized condition is inherently modular and allowed
assimilation of substituents at any site of imidazo[1,2-a]pyridines
(Table 2). Initially, a wide variety of 2-aminopyridines (2) with
substitutions at various positions were reacted with 1a under the
optimized reaction conditions, and moderate to high yields of
tandem oxidative cyclization products were obtained. A labile
bromo substituent at the C-5 position was well tolerated under
the reaction conditions to afford the tandem products in good

3
yields (Table 2, 3m and 3p). Lower yields of 3-aroylimidazo[1,2-
a]pyridines were observed for 2-amino-6-methylpyridine; this
may be due to the steric congestion (Table 2, 3i). Unfortunately,
desired product was not observed when 2-amino-5-nitropyridine
was reacted with 1a.
This observation suggests that the key intermediate in the
ACCEPTED MANUSCRIPT
reported tandem process is 4a. When radical scavenger TEMPO
(1.2 equiv) was used in the oxidative cyclization of the Michael
adduct (4a), there was minimal reduction in yields were
observed, which confirms that the oxidative cyclization proceeds
through a non-radical mechanism pathway (Scheme 2, eq III).
Surprisingly, only traces of product (3a) were observed, together
with low yields of the Michael adduct, when TEMPO was used
in the standard reaction (Scheme 2, eq IV).
With regard to substitutions of aryl rings on chalcones, a range
of diverse groups could be employed, which demonstrates the
high level of flexibility of the present approach. For example,
chalcone derivatives bearing substituents like methyl, methoxy,
fluoro, chloro, bromo, nitro and cyano at ortho, meta and para
positions on aryl rings (Ar and Ar') were well tolerated to afford
the desired products in good yields (Table 2, entries 3e-s).
Generally, chalcones bearing electron donating substituents on
the Ar and/or Ar' rings afforded higher yields of tandem products
3 as compared with the chalcones bearing electron withdrawing
groups. The electron withdrawing substituents such as nitro and
cyano on Ar' of chalcones greatly influenced the yields of tandem
products (Table 2, entries 3q-s). It was also observed that the
chalcones with ortho-substituted aryl rings (Ar') produced lower
yields of tandem product (Table 2, entries 3n-p). Structures of all
the synthesized 3-aroylimidazo[1,2-a]pyridines (3) were
confirmed by IR and NMR spectroscopy and HRMS data.
Table 2 Synthesis of 3-aroylimidazo[1,2-a]pyridines 3a,b
Scheme 2 Control experiments
Based on the results obtained and recent literature,8 the
plausible mechanism for the formation of 3-aroylimidazo[1,2-
a]pyridines (3) is shown in Scheme 3. It is believed that initially
CuCl2 assists in the Michael addition of 2-aminopyridine to give
the Michael adduct, 1,3-diaryl-3-(pyridin-2-ylamino)propan-1-
one (4). Concurrent binding of pyridinium nitrogen followed by
the enolic carbon to the copper salt provides intermediate 5.
Oxidation of 5 to 6 followed by reductive elimination produces
intermediate 7, which on rapid oxidative aromatization under
aerobic conditions leads to the tandem product, 3-
aroylimidazo[1,2-a]pyridines (3). Regeneration of Cu(II) from
Cu(I) under aerobic oxygen completes the catalytic cycle.15
3a, 81%
3b, 76%
3c, 60%
3d, 62%
3e, 86%
3i, 45%
3f, 80%
3j, 76%
3g, 64%
3k, 59%
3h, 76%
3l, 75%
N
Cl
Ar'
Cu
N
O
Cl
+
Michael addn
O
Ar
Ar' H2N
N
3
Ar
1
2
Cu(II)
air
aromatization
Cl
[O]
CuII
N
N
Cl
Ar'
N
Cu(I)
O
N
H
4
Ar'
Ar
O
7
Ar
3m, 61%
3q, 56%
3n, 62%
3r, 51%
3o, 55%
3s, 38%
3p, 57%
HCl
N
N
N
N
Cu
Ar'
X
CuCl
Ar'
O
Ar
N
N
HX
HO
Ar
6
Cu
Ar'
Ar
HCl
a Reagents and conditions: 1 (1.0 mmol), 2 (1.2 mmol), CuCl2.2H2O (10
mol %), toluene (5 mL), 120 °C, 12 h, ambient air.
b Isolated yields.
O
5
Scheme 3 Plausible mechanism for the formation of 3 by copper
catalyzed tandem reaction between 1 and 2.
Some control experiments have been performed to explore the
mechanism for the proposed tandem reaction (Scheme 2). When
the chalcone (1a) was reacted with 2a in the presence of nitrogen
atmosphere, moderate yield of Michael adduct (4a) was obtained
without formation of the cyclized product (3a) clarifies the
crucial role of aerobic conditions for the success of tandem
reaction (Scheme 2, eq I). When Michael adduct (4a) was
subjected to the optimized reaction conditions, quantitative
conversion was observed (isolated yield 85%, Scheme 2, eq II).
3. Conclusion
In summary, we have demonstrated a straightforward, atom-
economical, high yielding one-pot procedure for the synthesis of
bioactive 3-aroylimidazo[1,2-a]pyridines from chalcones and 2-
aminopyridines via unprecedented CuCl2 catalyzed tandem aza-
Michael addition and oxidative C−N coupling. The catalytic
amount of copper catalyst was found to be crucial for the success

4
Tetrahedron
1
of tandem reaction, which altered the synthetic pathway of the
= 0.71 (25% EtOAc in hexane); H NMR (400 MHz, CDCl3) δ
9.48 (d, J = 3.0 Hz, 1H, C-5 ArH), 7.59 (s, 1H, ArH), 7.52 (d, J =
6.2 Hz, 2H, ArH), 7.34 (t, J = 11.5 Hz, 2H, ArH), 7.28 (d, J = 8.5
Hz, 1H, ArH), 7.18 – 7.06 (m, 5H, ArH), 6.97 (d, J = 0.9 Hz, 1H,
ArH), 2.54 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3) δ 187.1
(C=O), 155.4, 147.9, 140.9, 138.8, 134.2, 131.6, 130.2, 129.5,
128.2, 127.8, 127.7, 127.5, 117.1, 116.1, 21.6; IR (KBr) ν:
3060, 1605 (C=Ostr), 1466, 1396, 918, 694 cm-1; HRMS calcd for
C21H17N2O 313.1335 found 313.1335 [M+H]+.
ACCEPTED MANUSCRIPT
reaction to give the aforementioned tandem products, whereas
entirely dissimilar products were reported in the earlier methods
with the same precursors, but in the absence of a copper catalyst.
The method allows regioseletive introduction of an aryl ring at
the C-2 position and an aroyl group at the C-3 position in single
step. Dual C−N bond formation in presence of an economically
attractive copper salt, ligand and additive free conditions, and
ubiquitous air as an oxidant are the salient features of this
protocol.
(6-Methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)(phenyl)
methanone (3d): Yield 62%; Colorless solid; mp 156-158 °C; Rf
= 0.66 (30% EtOAc in hexane); H NMR (400 MHz, CDCl3) δ
4. Experimental section
1
General: Melting points were determined in open capillary tubes
on an EZ-Melt Automated melting point apparatus and are
uncorrected. Reactions were monitored by using thin layer
chromatography (TLC) on 0.2 mm silica gel F254 plates
(Merck). The chemical structures of final products were
determined by nuclear magnetic resonance spectra (1H NMR and
13C NMR) using Bruker AV NMR 300 MHz, Bruker AV 400
MHz and Varian 500 MHz spectrometers. 13C NMR spectra are
fully decoupled. Chemical shifts were reported in parts per
million (ppm) using deuterated solvent peak or tetramethylsilane
(internal) as the standard. The HRMS data were recorded in ESI
mode using Agilent Q-TOF Mass spectrometer, and IR spectra
were obtained an using ABB Bomen MB 3000 FTIR instrument.
The α,β-unsaturated ketones (chalcones) 1 were prepared by the
treatment of an appropriate acetophenone with benzaldehydes in
the presence of sodium hydroxide as reported in literature.[14] All
other chemicals were obtained from the commercial suppliers
and used without further purification.
9.40 (s, 1H, C-5 ArH), 7.73 (d, J = 8.9 Hz, 1H, ArH), 7.53 (d, J =
7.2 Hz, 2H, ArH), 7.40 (d, J = 8.9 Hz, 1H, ArH), 7.33 (d, J = 6.7
Hz, 2H, ArH), 7.31 – 7.24 (m, 1H, ArH), 7.17 – 7.06 (m 5H,
ArH), 2.47 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3) δ 187.3
(C=O), 154.9, 146.4, 138.8, 134.2, 132.1, 131.7, 130.2, 129.6,
128.1, 127.7, 127.7, 126.2, 124.6, 119.9, 116.7, 18.5; IR (KBr) ν:
3063, 1605 (C=Ostr), 1466, 1389, 903, 733 cm-1; HRMS calcd for
C21H17N2O 313.1335 found 313.1339 [M+H]+.
p-Tolyl(2-p-tolylimidazo[1,2-a]pyridin-3-yl)methanone (3e):
Yield 86%; Colorless solid; mp 111-114 °C; Rf = 0.67 (30%
EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.47 (d, J = 6.4
Hz, 1H, C-5 ArH), 7.80 (d, J = 8.7 Hz, 1H, ArH), 7.52 (d, J = 7.3
Hz, 1H, ArH), 7.46 (d, J = 7.4 Hz, 2H, ArH), 7.29 – 7.22 (m, 2H,
ArH), 7.07 (t, J = 6.3 Hz, 1H, ArH), 6.93 – 6.85 (m, 4H, ArH),
2.28 (s, 6H, CH3, CH3); 13C NMR (100 MHz, CDCl3) δ 187.3
(C=O), 154.5, 147.3, 142.5, 138.1, 136.0, 131.1, 130.1, 129.8,
128.8, 128.4, 128.1, 120.0, 117.3, 114.3, 21.5, 21.2; IR (KBr) ν:
3063, 1605 (C=Ostr), 1504, 1412, 1381, 903, 818 cm-1; HRMS
calcd for C22H19N2O 327.1492 found 327.1500 [M+H]+.
Procedure for synthesis of 3-aroylimidazo[1,2-a]pyridine (3a) A
clean oven dried 10 ml RB flask was charged with chalcone (1a)
(200 mg, 0.961 mmol), 2-aminopyridine (2a) (108 mg, 1.15
mmol), CuCl2.2H2O (16 mg, 0.096 mmol) and toluene (5.0 ml).
The resulting solution was stirred at 120 °C for 12 h under
ambient air. On completion, the reaction mass was evaporated to
dryness. The crude residue was purified by column
chromatography (EtOAc: Hexanes, 2: 3) to obtain phenyl(2-
phenylimidazo[1,2-a]pyridin-3-yl)methanone (3a) in 81% yield
(232 mg).
(8-Methyl-2-p-tolylimidazo[1,2-a]pyridin-3-yl)(p-tolyl)meth-
anone (3f): Yield 80%; Colourless solid; mp 127-129 °C; Rf =
0.70 (25% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.34
(d, J = 5.5 Hz, 1H, C-5 ArH), 7.45 (d, J = 7.2 Hz, 2H, ArH), 7.34
– 7.20 (m, 3H, ArH), 7.00 – 6.96 (m, 1H, ArH), 6.93 – 6.85 (m,
4H, ArH), 2.75 (s, 3H, CH3), 2.27 (s, 6H, CH3, CH3); 13C NMR
(100 MHz, CDCl3) δ 187.4 (C=O), 154.1, 147.5, 142.3, 137.9,
136.1, 131.5, 130.2, 129.8, 128.4, 128.4, 127.7, 127.3, 125.8,
120.4, 114.3, 21.5, 21.2, 17.1; IR (KBr) ν: 3060, 1605 (C=Ostr),
1381, 910, 733 cm-1; HRMS calcd for C23H21N2O 341.1648
found 341.1659 [M+H]+.
Phenyl(2-phenylimidazo[1,2-a]pyridin-3-yl)methanone (3a):
Yield 81%; Colourless solid; mp 124-127 °C; Rf = 0.63 (30%
EtOAc in hexane); 1H NMR (300 MHz, CDCl3) δ 9.55 (d, J = 7.0
Hz, 1H, C-5 ArH), 7.81 (d, J = 8.9 Hz, 1H, ArH), 7.57 – 7.45 (m,
3H, ArH), 7.32 (dd, J = 7.8, 1.4 Hz, 2H, ArH), 7.29 – 7.21 (m,
1H, ArH), 7.17 – 7.02 (m, 6H, ArH); 13C NMR (75 MHz, CDCl3)
δ 187.4 (C=O), 155.0, 147.4, 138.7, 134.0, 131.7, 130.2, 129.6,
129.2, 128.3, 128.2, 127.7, 120.0, 117.5, 114.6; IR (KBr) ν:
3070, 1597 (C=Ostr), 1388, 1326, 1218 cm-1; HRMS calcd for
C20H15N2O 299.1179 found 299.1184 [M+H]+.
(7-Methyl-2-p-tolylimidazo[1,2-a]pyridin-3-yl)(p-tolyl)meth-
anone (3g): Yield 64%; Pale yellow solid; mp 190-192 °C; Rf =
0.68 (25% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.38
(d, J = 6.9 Hz, 1H, C-5 ArH), 7.56 (s, 1H, ArH), 7.43 (d, J = 7.4
Hz, 2H, ArH), 7.24 (d, J = 7.3 Hz, 2H, ArH), 6.92 – 6.83 (m,
5H, ArH), 2.52 (s, 3H, CH3), 2.27 (s, 6H, CH3, CH3); 13C NMR
(100 MHz, CDCl3) δ 187.0 (C=O), 154.9, 147.8, 142.2, 140.4,
138.0, 136.2, 131.3, 130.1, 129.7, 128.4, 127.4, 119.7, 116.8,
116.0, 21.6, 21.4, 21.2; IR (KBr) ν: 3024, 1597 (C=Ostr), 1474,
1227, 926, 703 cm-1; HRMS calcd for C23H21N2O 341.1648
found 341.1647 [M+H]+.
(8-Methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)(phenyl)
methanone (3b): Yield 76%; Colourless solid; mp 139-141 °C;
Rf = 0.86 (20% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ
9.44 (d, J = 4.9 Hz, 1H, C-5 ArH), 7.53 (d, J = 6.5 Hz, 2H, ArH),
7.40 – 7.32 (m, 3H, ArH), 7.31 – 7.24 (m, 1H, ArH), 7.17 – 7.07
(m, 5H, ArH), 7.06 – 7.03 (m, 1H, ArH), 2.77 (s, 3H, CH3); 13C
NMR (100 MHz, CDCl3) δ 187.5 (C=O), 154.6, 147.7, 138.9,
134.3, 131.6, 130.3, 129.6, 128.1, 127.8, 127.7, 127.5, 126.0,
120.5, 114.6, 17.2; IR (KBr) ν: 3063, 1606 (C=Ostr), 1466, 1388,
1250, 910, 702 cm-1; HRMS calcd for C21H17N2O 313.1335
found 313.1333 [M+H]+.
(6-Methyl-2-p-tolylimidazo[1,2-a]pyridin-3-yl)(p-tolyl)meth-
anone (3h): Yield 76%; Colourless solid; mp 149-151 °C; Rf =
0.60 (30% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.30
(s, 1H, C-5 ArH), 7.70 (d, J = 8.9 Hz, 1H, ArH), 7.45 (d, J = 7.4
Hz, 2H, ArH), 7.36 (d, J = 8.9 Hz, 1H, ArH), 7.24 (d, J = 7.3 Hz,
2H, ArH), 6.92 – 6.85 (m, 4H, ArH), 2.44 (s, 3H, CH3), 2.27 (s,
6H, CH3, CH3); 13C NMR (100 MHz, CDCl3) δ 187.2 (C=O),
154.4, 146.3, 142.3, 137.9, 136.1, 131.7, 131.3, 130.1, 129.8,
128.4, 126.0, 124.2, 119.8, 116.6, 21.5, 21.2, 18.5; IR (KBr) ν:
(7-Methyl-2-phenylimidazo[1,2-a]pyridin-3-yl)(phenyl)
methanone (3c): Yield 60%; Off-white solid; mp 140-142 °C; Rf

5
3063, 1605 (C=Ostr), 1504, 1412, 1381, 903, 818 cm-1; HRMS
calcd for C23H21N2O 341.1648 found 341.1657 [M+H]+.
(4-Chlorophenyl)(2-(2-fluorophenyl)imidazo[1,2-a]pyridin-
ACCEPTED MANUSCRIPT
3-yl)methanone (3n): Yield 62%; Off-white solid; mp 144-146
°C; Rf = 0.60 (40% EtOAc in hexane); H NMR (400 MHz,
1
(5-Methyl-2-p-tolylimidazo[1,2-a]pyridin-3-yl)(p-tolyl)
CDCl3) δ 9.57 (d, J = 6.6 Hz, 1H, C-5 ArH), 7.85 (d, J = 8.8 Hz,
1H, ArH), 7.61 – 7.49 (m, 2H, ArH), 7.47 (d, J = 8.0 Hz, 2H,
ArH), 7.24 (d, J = 5.4 Hz, 1H, ArH), 7.19 – 7.05 (m, 4H, ArH),
6.72 (t, J = 9.0 Hz, 1H, ArH); 13C NMR (100 MHz, CDCl3) δ
185.8 (C=O), 159.1 (d, J = 248.7 Hz), 148.5, 147.7, 137.8, 136.9,
131.2 (d, J = 2.4 Hz), 131.0, 130.7 (d, J = 8.3 Hz), 129.3, 128.3,
127.7, 124.2 (d, J = 3.5 Hz), 122.8, 122.8 (d, J = 14.1 Hz), 117.7,
115.2 (d, J = 22.0 Hz), 114.98; IR (KBr) ν: 3055, 2924, 1612
(C=Ostr), 1481, 1227, 1080, 764 cm-1; HRMS calcd for
C20H13ClFN2O 351.0695 found 351.0698 [M+H]+.
methanone (3i): Yield 45%; Colorless solid; mp 134-136 °C; Rf
= 0.69 (25% EtOAc in hexane); H NMR (400 MHz, CDCl3) δ
1
7.79 – 7.68 (m, 3H, ArH), 7.47 (d, J = 3.6 Hz, 2H, ArH), 7.39 –
7.25 (m, 1H, ArH), 7.09 – 6.90 (m, 4H, ArH), 6.75 (s, 1H, ArH),
2.43 (s, 3H, CH3), 2.35 (s, 3H, CH3), 2.29 (s, 3H, CH3); 13C NMR
(100 MHz, CDCl3) δ 188.5 (C=O), 149.0, 147.5, 144.4, 137.9,
137.5, 136.0, 130.7, 130.5, 129.3, 129.0, 128.8, 127.0, 120.1,
115.2, 114.5, 22.1, 21.7, 21.2; IR (KBr) ν: 3063, 1651, 1597
(C=Ostr), 1474, 1381, 1234, 926, 733 cm-1; HRMS calcd for
C23H21N2O 341.1648 found 341.1652 [M+H]+.
(4-Chlorophenyl)(2-(2-fluorophenyl)-7-methylimidazo[1,2-
(2-(3-Methoxyphenyl)-8-methylimidazo[1,2-a]pyridin-3-
yl)(p-tolyl)methanone (3j): Yield 76%; Red viscous liquid; Rf =
0.46 (50% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.36
(d, J = 6.6 Hz, 1H, C-5 ArH), 7.47 (d, J = 7.2 Hz, 2H, ArH), 7.31
(dd, J = 9.0, 4.1 Hz, 1H, ArH), 7.02 – 6.94 (m, 3H, ArH), 6.94
(d, J = 7.4 Hz, 2H, ArH), 6.89 (s, 1H, ArH), 6.72 (d, J = 7.5 Hz,
1H, ArH), 3.66 (s, 3H, OCH3), 2.75 (s, 3H, CH3), 2.28 (s, 3H,
CH3). 13C NMR (100 MHz, CDCl3) δ 187.2 (C=O), 159.0, 153.7,
147.5, 142.4, 136.2, 135.6, 129.7, 128.9, 128.4, 127.8, 127.5,
125.9, 123.0, 120.6, 115.0, 114.8, 114.5, 55.2, 21.5, 17.1; IR
(CCl4) ν: 3055, 2955, 1606 (C=Ostr), 1474, 1285, 803, 756 cm-1;
HRMS calcd for C23H21N2O2 357.1598 found 357.1602 [M+H]+.
a]pyridin-3-yl)methanone (3o): Yield 55%; Off-white solid; mp
1
157-159 °C; Rf = 0.63 (30% EtOAc in hexane); H NMR (400
MHz, CDCl3) δ 9.45 (d, J = 7.1 Hz, 1H, C-5 ArH), 7.59 (s, 1H,
ArH), 7.49 (td, J = 7.4, 1.7 Hz, 1H, ArH), 7.46 – 7.41 (m, 2H,
ArH), 7.26 – 7.19 (m, 1H, ArH), 7.12 – 7.04 (m, 3H, ArH), 6.99
(dd, J = 7.1, 1.6 Hz, 1H, ArH), 6.74 – 6.65 (m, 1H, ArH), 2.54 (s,
3H, CH3).13C NMR (100 MHz, CDCl3) δ 185.6 (C=O), 159.1 (d,
J = 248.7 Hz), 148.8, 148.2, 141.1, 137.6, 137.0, 131.3 (d, J = 2.5
Hz), 130.8 (d, J = 8.3 Hz), 130.5, 127.6, 127.5, 124.1 (d, J = 3.4
Hz), 122.9 (d, J = 14.3 Hz), 120.6, 117.5, 116.2, 115.2 (d, J =
22.0 Hz), 21.6; IR(KBr) ν: 3055, 2965, 1612 (C=Ostr), 1481,
1227, 1076, 764 cm-1; HRMS calcd for C21H15ClFN2O 365.0851
found 365.0851 [M+H]+.
(2-(3-Methoxyphenyl)-7-methylimidazo[1,2-a]pyridin-3-
yl)(p-tolyl)methanone (3k): Yield 59%; Pale yellow sold; mp
110-112 °C; Rf = 0.41 (65% EtOAc in hexane); H NMR (400
(6-Bromo-2-(2-fluorophenyl)imidazo[1,2-a]pyridin-3-yl)(4-
chloro phenyl)methanone (3p): Yield 57%; Off-white solid; mp
172-175 °C; Rf = 0.80 (20% EtOAc in hexane); 1H NMR (400
MHz, CDCl3) δ 9.73 (s, 1H, C-5 ArH), 7.75 (d, J = 9.3 Hz, 1H,
ArH), 7.64 (d, J = 9.4 Hz, 1H, ArH), 7.54 (t, J = 6.9 Hz, 1H,
ArH), 7.46 (d, J = 7.4 Hz, 2H, ArH), 7.26 (d, J = 5.4 Hz, 1H,
ArH), 7.15 – 7.06 (m, 3H, ArH), 6.73 (t, J = 9.1 Hz, 1H, ArH);
13C NMR (100 MHz, CDCl3) δ 185.7 (C=O), 159.1 (d, J = 249.1
Hz), 148.3, 146.07, 138.2, 136.4 (d, J = 1.9 Hz), 132.7, 131.2,
131.1, 130.5, 128.3, 127.8, 124.3 (d, J = 3.5 Hz), 122.3 (d, J =
14.0 Hz), 120.9, 118.1, 115.3 (d, J = 22.0 Hz), 109.87; IR (KBr)
ν: 3101, 3055, 2924, 1612 (C=Ostr), 1481, 1389, 1227, 1080, 764
cm-1; HRMS calcd for C20H12BrClFN2O 428.9800 found
428.9801 [M+H]+ 430.9780 [M+H+2]+.
1
MHz, CDCl3) δ 9.43 – 9.41 (m, 1H, C-5 ArH), 7.58 – 7.56 (m,
1H, ArH), 7.47 (d, J = 3.4 Hz, 2H, ArH), 7.11 – 6.92 (m, 5H,
ArH), 6.87 (s, 1H, ArH), 6.75 (d, J = 0.4 Hz, 1H, ArH), 3.66 (s,
3H, OCH3), 2.54 (s, 3H, CH3), 2.29 (s, 3H, CH3); 13C NMR (100
MHz, CDCl3) δ 186.9 (C=O), 159.0, 154.5, 147.7, 142.4, 140.6,
136.2, 135.5, 129.7, 128.8, 128.4, 127.4, 122.9, 119.9, 117.0,
116.0, 115.0, 114.8, 55.2, 21.6, 21.5; IR (KBr) ν: 3063, 2955,
1606 (C=Ostr), 1455, 1281, 833, 746 cm-1; HRMS calcd for
C23H21N2O2 357.1598 found 357.1598 [M+H]+.
(2-(3-Methoxyphenyl)-6-methylimidazo[1,2-a]pyridin-3-yl)(p-
tolyl) methanone (3l): Yield 75%; Off-white solid; mp 83-85 °C;
Rf = 0.40 (60% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ
9.32 (s, 1H, C-5 ArH), 7.73 (d, J = 8.4 Hz, 1H, ArH), 7.49 (d, J =
6.4 Hz, 2H, ArH), 7.39 (d, J = 8.2 Hz, 1H, ArH), 7.10 – 6.92 (m,
4H, ArH), 6.89 (s, 1H, ArH), 6.74 (d, J = 5.9 Hz, 1H, ArH), 3.66
(s, 3H, OCH3), 2.46 (s, 3H, CH3), 2.29 (s, 3H, CH3); 13C NMR
(101 MHz, CDCl3) δ 187.1 (C=O), 159.0, 154.0, 146.2, 142.5,
136.2, 135.4, 131.9, 129.7, 128.8, 128.5, 126.0, 124.4, 122.9,
119.9, 116.7, 115.0, 114.7, 55.2, 21.5, 18.5; IR (KBr) ν: 3055,
2955, 1606 (C=Ostr), 1474, 1281, 833, 756 cm-1; HRMS calcd for
C23H21N2O2 357.1598 found 357.1597 [M+H]+.
4-(3-Benzoylimidazo[1,2-a]pyridin-2-yl)benzonitrile
(3q):
Yield 56%; Off-white solid; mp 173-175 °C; Rf = 0.43 (50%
EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.54 (d, J = 4.5
Hz, 1H, C-5 ArH), 7.84 (d, J = 8.5 Hz, 1H, ArH), 7.59 (d, J = 7.3
Hz, 1H, ArH), 7.50 (d, J = 6.5 Hz, 2H, ArH), 7.45 (d, J = 5.7 Hz,
2H, ArH), 7.39 (d, J = 7.9 Hz, 2H, ArH), 7.35 (d, J = 6.9 Hz, 1H,
ArH), 7.18 – 7.12 (m, 3H, ArH); 13C NMR (100 MHz, CDCl3) δ
186.9 (C=O), 152.4, 147.5, 138.7, 138.4, 132.4, 131.4, 130.7,
129.7, 129.5, 128.3, 128.0, 120.4, 118.6, 117.7, 115.2, 111.7; IR
(KBr) ν: 3109, 3070, 2222 (C≡Nstr), 1612 (C=Ostr), 1474, 1227,
933, 702 cm-1; HRMS calcd for C21H14N3O 324.1131 found
324.1131 [M+H]+.
(6-Bromo-2-(3-methoxyphenyl)imidazo[1,2-a]pyridin-3-yl)(p-
tolyl)methanone (3m): Yield 61%; Yellow liquid; Rf = 0.41 (60%
EtOAc in hexane); 1H NMR (400 MHz, CDCl3) δ 9.65 (s, 1H, C-
5 ArH), 7.71 (d, J = 9.2 Hz, 1H, ArH), 7.59 (d, J = 9.4 Hz, 1H,
ArH), 7.48 (d, J = 7.4 Hz, 2H, ArH), 7.06 (t, J = 7.5 Hz, 1H,
ArH), 6.97 – 6.89 (m, 3H, ArH), 6.88 (s, 1H, ArH), 6.75 (d, J =
7.9 Hz, 1H, ArH), 3.66 (s, 3H, OCH3), 2.29 (s, 3H, CH3); 13C
NMR (100 MHz, CDCl3) δ 187.0 (C=O), 159.1, 154.0, 145.6,
143.1, 135.6, 134.8, 132.3, 129.7, 129.0, 128.6, 128.2, 122.9,
120.2, 118.0, 115.3, 114.7, 109.2, 55.2, 21.5; IR (CCl4) ν: 3060,
2955, 1606 (C=Ostr), 1474, 1381, 910, 703 cm-1; HRMS calcd for
C22H18BrN2O2 421.0546 found 421.0546 [M+H]+ 423.0524
[M+H+2]+.
4-(3-Benzoyl-6-methylimidazo[1,2-a]pyridin-2-yl)benzonitrile
(3r): Yield 51%; Pale yellow solid; mp 179-182 °C; Rf = 0.42
1
(50% EtOAc in hexane); H NMR (400 MHz, CDCl3) δ 9.36 (s,
1H, C-5 ArH), 7.73 – 7.71 (m, 1H, ArH), 7.50 – 7.32 (m, 8H,
ArH), 7.15 (d, J = 5.0 Hz, 2H, ArH), 2.48 (s, 3H, CH3); 13C NMR
(101 MHz, CDCl3) δ 186.9 (C=O), 152.2, 146.5, 138.9, 138.6,
132.7, 132.3, 131.4, 130.6, 129.6, 128.0, 126.1, 120.2, 118.7,
116.9, 111.6, 18.6; IR (KBr) ν: 3102, 3059, 2222 (C≡Nstr), 1608
(C=Ostr), 1478, 1232, 933, 699 cm-1; HRMS calcd for C22H16N3O
338.1288 found 338.1292 [M+H]+.

6
Tetrahedron
18. Nair, D. K.; Mobin, S. M.; Namboothiri, I. N. N. Org. Lett.
(4-Methoxyphenyl)(2-(4-nitrophenyl)imidazo[1,2-a]pyridin-
ACCEPTED MANUSCRIPT
2012, 14, 4580-4583.
3-yl)methanone (3s): Yield 38%; Pale yellow solid; mp 199-202
°C; Rf = 0.44 (65% EtOAc in hexane); H NMR (400 MHz,
1
19. Huang, H.; Ji, X.; Tang, X.; Zhang, M.; Li, X.; Jiang, H. Org.
Lett. 2013, 15, 6254-6257.
20. Wen, L.-R.; Li, Z.-R.; Li, M.; Cao, H. Green Chem. 2012, 14,
707-716.
21. Yan, R.-L.; Yan, H.; Ma, C.; Ren, Z.-Y.; Gao, X.-A.; Huang,
G.-S.; Liang, Y.-M. J. Org. Chem. 2012, 77, 2024-2028.
22. Wang, H.; Wang, Y.; Liang, D.; Liu, L.; Zhang, J.; Zhu, Q.
Angew. Chem. Int. Ed. 2011, 50, 5678-5681.
23. Albrecht, L.; Albrecht, A.; Ransborg, L. K.; Jorgensen, K. A.
Chem. Sci. 2011, 2, 1273-1277.
CDCl3) δ 9.34 (s, 1H, C-5 ArH), 8.03 (d, J = 6.9 Hz, 2H, ArH),
7.83 (d, J = 8.7 Hz, 1H, ArH), 7.64 – 7.51 (m, 5H, ArH), 7.13 –
7.09 (m, 1H, ArH), 6.66 (d, J = 6.8 Hz, 2H, ArH), 3.76 (s, 3H,
OCH3); 13C NMR (100 MHz, CDCl3) δ 185.6 (C=O), 163.4,
150.3, 147.3, 147.2, 140.7, 132.0, 130.9, 130.8, 129.2, 127.9,
123.0, 120.6, 117.7, 114.9, 113.5, 55.5; IR (KBr) ν: 3102, 1597
(C=Ostr), 1512, 1342, 1227, 1026, 756 cm-1; HRMS calcd for
C21H16N3O4 374.1135 found 374.1132 [M+H]+.
24. Palani, T.; Park, K.; Kumar, M. R.; Jung, H. M.; Lee, S. Eur. J.
Org. Chem. 2012, 5038-5047.
Acknowledgments
25. Chandra Mohan, D.; Sarang, N. B.; Adimurthy, S. Tetrahedron
Lett. 2013, 54, 6077-6080.
26. Donohoe, T. J.; Kabeshov, M. A.; Rathi, A. H.; Smith, I. E. D.
Org. Biomol. Chem. 2012, 10, 1093-1101.
27. Starkov, P.; Rota, F.; D'Oyley, J. M.; Sheppard, T. D. Adv.
Synth. Catal. 2012, 354, 3217-3224.
Financial support to carry out this work from CSIR New Delhi
(Grant No. 02(0115)/13/EMR-II) and DST FIST for FTIR is
highly acknowledged. Authors thanks to Kiran Indukuri for his
kind support in analytical services. PK and KP are thankful to
CSIR and UGC, respectively for research fellowship
.
28. Chandra Mohan, D.; Reddy Donthiri, R.; Nageswara Rao, S.;
Adimurthy, S. Adv. Synth. Catal. 2013, 355, 2217-2221.
29. Yu, J.; Jin, Y.; Zhang, H.; Yang, X.; Fu, H. Chem. Eur. J. 2013,
19, 16804-16808.
30. Hsing-Pang, H.; Yu-Sheng, C.; Jing-Ping, L.; Jang-Yang, C.;
Yen-Shih, T., 2006.
31. Barun, O.; Ila, H.; Junjappa, H.; Singh, O. M. J. Org. Chem.
2000, 65, 1583-1587.
32. Zhang, Y.; Chen, Z.; Wu, W.; Zhang, Y.; Su, W. J. Org. Chem.
2013, 78, 12494-12504.
33. Basilio-Lopes, A.; de Aquino, T. M.; Mongeot, A.;
Bourguignon, J.-J.; Schmitt, M. Tetrahedron Lett. 2012, 53,
2583-2587.
34. Ma, L.; Wang, X.; Yu, W.; Han, B. Chem. Commun. 2011, 47,
11333-11335.
35. During the course of our manuscript preparation, similar results
were reported by Hajra group where 3-aroylimidazo[1,2-
a]pyridines were achieved in presence of Cu(OAc)2.H2O, 1,10-
phenanthroline under O2 atmosphere. Monir, K.; Kumar Bagdi,
A.; Mishra, S.; Majee, A.; Hajra, A. Adv. Synth. Catal. 2014,
356, 1105-1112.
36. Shi, W.; Liu, C.; Lei, A. Chem. Soc. Rev. 2011, 40, 2761-2776.
37. Nakamura, I.; Yamamoto, Y. Chem. Rev. 2004, 104, 2127-
2198.
38. Chen, X.; Engle, K. M.; Wang, D.-H.; Yu, J.-Q. Angew. Chem.
Int. Ed. 2009, 48, 5094-5115.
39. Liu, Y.; Wan, J.-P. Org. Biomol. Chem. 2011, 9, 6873-6894.
40. Ueda, S.; Nagasawa, H. J. Am. Chem. Soc. 2009, 131, 15080-
15081.
41. Zhang, Y.; Li, X.; Li, J.; Chen, J.; Meng, X.; Zhao, M.; Chen,
B. Org. Lett. 2011, 14, 26-29.
42. Upadhyaya, K.; Ajay, A.; Mahar, R.; Pandey, R.; Kumar, B.;
Shukla, S. K.; Tripathi, R. P. Tetrahedron 2013, 69, 8547-8558.
43. Pericherla, K.; Jha, A.; Khungar, B.; Kumar, A. Org. Lett. 2013,
15, 4304-4307.
44. Pericherla, K.; Khedar, P.; Khungar, B.; Kumar, A. Chem.
Commun. 2013, 49, 2924-2926.
45. Pericherla, K.; Khungar, B.; Kumar, A. Tetrahedron Lett. 2012,
53, 1253-1257.
46. Kaswan, P.; Pericherla, K.; Kumar, A. Synlett 2013, 24, 2751-
2757.
47. Khedar, P.; Pericherla, K.; Kumar, A. Synlett 2012, 23, 2609-
2614.
Supplementary Material
Supplementary data (Copies of the 1H, 13C NMR and HRMS data
for compound 3a-s) associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/.....
References and notes
1. Wan, J.; Zheng, C.-J.; Fung, M.-K.; Liu, X.-K.; Lee, C.-S.;
Zhang, X.-H. J. Mater. 2012, 22, 4502-4510.
2. Stasyuk, A. J.; Banasiewicz, M.; Cyrański, M. K.; Gryko, D. T.
J. Org. Chem. 2012, 77, 5552-5558.
3. Enguehard-Gueiffier, C.; Gueiffier, A. Mini-Rev. Med. Chem.
2007, 7, 888-899.
4. Katritzky, A. R.; Xu, Y.-J.; Tu, H. J. Org. Chem. 2003, 68,
4935-4937.
5. John, A.; Shaikh, M. M.; Ghosh, P. Dalton Trans. 2009, 10581-
10591.
6. Song, G.; Zhang, Y.; Li, X. Organometallics 2008, 27, 1936-
1943.
7. Tung, Y.-S.; Coumar, M. S.; Wu, Y.-S.; Shiao, H.-Y.; Chang,
J.-Y.; Liou, J.-P.; Shukla, P.; Chang, C.-W.; Chang, C.-Y.; Kuo,
C.-C.; Yeh, T.-K.; Lin, C.-Y.; Wu, J.-S.; Wu, S.-Y.; Liao, C.-C.;
Hsieh, H.-P. J. Med. Chem 2011, 54, 3076-3080.
8. Couty, F.; Evano, G. In Comprehensive Heterocyclic Chemistry
III; Katritzky, A. R.; Ramsden, C. A.; Scriven, E. F. V.; Taylor,
R. J. K. Eds.; Elsevier: Oxford, 2008; pp. 409-499.
9. Lhassani, M.; Chavignon, O.; Chezal, J.-M.; Teulade, J.-C.;
Chapat, J.-P.; Snoeck, R.; Andrei, G.; Balzarini, J.; De Clercq,
E.; Gueiffier, A. Eur. J. Med. Chem. 1999, 34, 271-274.
10. Hamdouchi, C.; de Blas, J.; del Prado, M.; Gruber, J.; Heinz, B.
A.; Vance, L. J. Med. Chem 1998, 42, 50-59.
11. Fisher, M. H.; Lusi, A. J. Med. Chem 1972, 15, 982-985.
12. Masurier, N.; Debiton, E.; Jacquemet, A.; Bussière, A.; Chezal,
J.-M.; Ollivier, A.; Tétégan, D.; Andaloussi, M.; Galmier, M.-J.;
Lacroix, J.; Canitrot, D.; Teulade, J.-C.; Gaudreault, R. C.;
Chavignon, O.; Moreau, E. Eur. J. Med. Chem. 2012, 52, 137-
150.
13. Pericherla, K.; Kaswan, P.; Khedar, P.; Khungar, B.; Parang,
K.; Kumar, A. RSC Adv. 2013, 3, 18923-18930.
14. Cao, H.; Liu, X.; Zhao, L.; Cen, J.; Lin, J.; Zhu, Q.; Fu, M. Org.
Lett. 2013, 16, 146-149.
15. Santra, S.; Bagdi, A. K.; Majee, A.; Hajra, A. Adv. Synth. Catal.
2013, 355, 1065-1070.
48. Goswami, S.; Jana, S.; Hazra, A.; Adak, A. K. J. Heterocyclic
Chem. 2007, 44, 1191-1194.
16. He, C.; Hao, J.; Xu, H.; Mo, Y.; Liu, H.; Han, J.; Lei, A. Chem.
Commun. 2012, 48, 11073-11075.
17. Maiti, B.; Chanda, K.; Selvaraju, M.; Tseng, C.-C.; Sun, C.-M.
ACS. Comb. Sci. 2013, 15, 291-297.

ACCEPTED MANUSCRIPT
zSupporting Information
Synthesis of 3-Aroylimidazo[1,2-a]pyridines via CuCl2 Catalyzed Tandem
Dual Carbon-nitrogen Bonding
Pinku Kaswan,a Kasiviswanadharaju Pericherla,a Rajnikantb and Anil Kumar*a
aDepartment of Chemistry, Birla Institute of Technology and Science, Pilani, 333031, India
bDepartment of Physics, University of Jammu, Jammu Tawi, 180006, India
E-mail: anilkumar@pilani.bits-pilani.ac.in
Content
Copies of 1H NMR, 13C NMR and HRMS for 3a-s
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Copies of 1H NMR , 13C NMR and HRMS for 3a-s
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N
N
O
3g
N
N
O
3g
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N
N
O
3g
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N
N
O
3h
N
N
O
3h
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N
N
OCH3
O
3k
N
N
OCH3
O
3k
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N
N
OCH3
O
3k
10.5
9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0
f1 (ppm)
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