Copper(i) catalyzed Sonogashira reactions promoted by monobenzyl nicotinium chloride, a N-donor quaternary ammonium salt

Article abstract of DOI:10.1039/c5ra19028b

A novel and effective catalytic system using monobenzylnicotinium chloride combined with copper(i) chloride was employed for the first time in Sonogashira cross-coupling reactions of phenylacetylene with various aryl halides. The goal was to use an efficient green media by using copper instead of palladium in metal-catalyzed coupling reactions. Monobenzyl nicotinium chloride, a quaternary ammonium salt containing a coordinating centre, plays an important role in this catalytic system and increases the efficiency of Cu(i) species during the reaction. A number of internal alkynes were produced in moderate to excellent yields in short reaction times in DMF at 135-140 °C. The efficiency of this catalytic system was compared with the copper-based catalyst obtained from dibenzylnicotinium chloride which has no N-donor active site, wherein lower activity was observed due to lack of a coordination site.

Full text of DOI:10.1039/c5ra19028b

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ARTICLE
Copper(I) catalyzed Sonogashira reactions promoted
by monobenzyl nicotinium chloride a N- donor
quaternary ammonium salt
Cite this: DOI: 10.1039/x0xx00000x
Abdol Reza Hajipour*a,b, Elaheh Boostania and Fatemeh Mohammadsaleha
Received 00th January 2012,
Accepted 00th January 2012
A novel and effective catalytic system using monobenzylnicotinium chloride combined with
copper (I) chloride was employed for the first time in Sonogashira crossꢀcoupling reactions of
phenylacetylene with various aryl halides. The goal was reaching to an efficient green media
by using copper instead of palladium in metalꢀcatalyzed coupling reactions. Monobenzyl
nicotinium chloride, a quaternary ammonium salt containing a coordinating centre, plays an
important role in this catalytic system and increases the efficiency of Cu(I) species during the
reaction. A number of internal alkynes were produced in moderate to excellent yields in short
reaction times in DMF at 135ꢀ140 °C. The efficiency of this catalytic system was compared
DOI: 10.1039/x0xx00000x
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with the copperꢀbased catalyst obtained from dibenzylnicotinium chloride which has no
donor active site, wherein lower activity was observed due to lack of coordination site.
Nꢀ
are important parameters for these copperꢀassisted catalytic
systems. Various ligands, such as triphenylphosphine ,20 1,10ꢀ
Introduction
Coupling of aryl halides with terminal acetylene in Sonogashira
reaction is one of the most applicable metalꢀcatalyzed carbon–
carbon crossꢀcoupling reactions. There is a wide range of
applications for the compounds containing carbonꢀcarbon triple
bonds, especially aryl alkynes and conjugated enynes, include
phenanthroline,21 ethylenediamine,22
N
,
N
ꢀdimethylglycine,23
24, 25
1,4ꢀdiazabicyclo [2.2.2]ꢀoctane (DABCO)
chloride,26
,
choline
N
ꢀBenzyl DABCO,27 have been investigated for this
reaction system. Recently, we have used dibenzyl nicotinium
chloride as the promoter in palladiumꢀcatalyzed CꢀC and CꢀS
coupling reactions.28, 29 By investigation of a series of Nicotineꢀ
derived ammonium salts as catalysts for chemical fixation of
carbon dioxide into cyclic carbonates, it was found that
monobenzylnicotinium bromide showed a much higher activity
than dibenzylnicotinium bromide.30 We have also reported the
catalytic activity of Cu4Cl5 species in combination with 1ꢀ
pharmaceuticals,
intermediate and etc.1ꢀ9
natural
products,
antibiotics,
drug
In recent years, a variety of competitive methods for the
formation of arylꢀnucleophile bonds such as CꢀC, CꢀN, and also
CꢀO bonds have been developed in crossꢀcoupling chemistry.10ꢀ
14
Quaternary ammonium and phosphonium salts (Q+ X‒) have
been highly successful in enhancing the reactivity and
selectivity of metal catalyzed organic reactions. The efficiency
of these systems is due to the metal nanoparticles stabilized by
quaternary salts and/or the formation of a new catalytic
system.15ꢀ17 Therefore, tremendous attentions have been given
to develop these catalytic systems.
The original catalytic system for Sonogashira couplings involve
the use of palladium catalyst and a copper(I) salt as a coꢀ
catalyst.1, 18 Many different synthetic methods based on copperꢀ
free palladium catalysts have been reported for this reaction,19
but the use of effective palladiumꢀfree systems is much more
interesting in view of modern organic synthesis, due to the cost
of palladium and its pollution. Recent attention has been
benzylꢀ4ꢀazaꢀ1ꢀazoniabicyclo[2.2.2]octane chloride (Nꢀbenzyl
DABCO chloride) in Sonogashira coupling reactions.27 In
continuation of our recent studies on the development of
catalytic systems containing quaternary ammonium and
phosphonium salts,17, 25ꢀ27 herein, we report the new catalytic
system [MBNT]+[Cu4Cl5]‾ as an effective catalyst for
palladium free Sonogashira crossꢀcoupling reactions. To date,
only a few reports are available for the preparation and catalytic
investigation of copper(I) complexes containing ammonium
salts and Cu4Cl5.31ꢀ33
Results and Discussion
concerned with employing copperꢀonly catalytic systems in The new catalytic system [MBNT][Cu4Cl5] was prepared by the
Sonogashira coupling reactions.19 Combinations of copper salts reaction of 1ꢀbenzylꢀ1ꢀmethylꢀ2ꢀ(pyridinꢀ3ꢀyl)pyrrolidinꢀ1ꢀium
and ligands have been reported as efficient catalytic systems for chloride ([MBNT]Cl) with fresh CuCl in methanol solvent. The
this CꢀC bond formation. High catalytic activity and selectivity
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structure of synthesized [MBNT][Cu4Cl5] (catalyst A) was
suggested as shown in Scheme 1.
The reaction of 1ꢀbenzylꢀ3ꢀ(1ꢀbenzylꢀ1ꢀmethylpyrrolidinꢀ1ꢀ
iumꢀ2ꢀyl)ꢀpyridinꢀ1ꢀium dichloride ([DBNT]Cl2) with CuCl in
methanol reflux gave the [DBNT][Cu4Cl6] complex,34 which is
shown as catalyst
B
in Scheme 1.
Ph
N
Ph
Cl
N
N
CuCl
PhCH2Cl (1mmol)
Acetonitrile
Cu4Cl5
Methanol, N2
N
N
N
95%
Catalyst A
96% yield
Fig. 1 EDX spectrum of the catalyst A
Ph
Ph
N
To investigate the optical properties, UVꢀVis analysis was
examined for the samples in DMSO solution at room
temperature. Fig. 2 illustrates a comparison of the absorption
spectra of pure nicotine, [MBNT]Cl and [DBNT]Cl2. As shown
in spectra, [MBNT]Cl spectrum has a sharp absorption in 271
nm and [DBNT]Cl2 shows two sharp absorption in 274 nm and
290 nm. Pure nicotine has almost two absorption, a broad one
in 271ꢀ274 nm and a sharp peak in 285nm
N
2
CuCl
Methanol, N2
Cl
Cu4Cl6
N
N
Cl
93%
Ph
Ph
Catalyst B
94% yield
Scheme 1. The catalyst A and catalyst B preparation
Monobenzylnicotininium chloride [MBNT]Cl as a quaternary
ammonium salt containing a coordinating center plays an
important role and increases the efficiency of Cu(I) species
during the reaction to create an effective and stable catalytic
system, so it plays a role more than a counter ion in this system.
While dibenzyl nicotinium dichloride [DBNT]Cl2 does not
have any coordinating center as a ligand to interact with Cu(I)
species during the reaction, and therefore shows a less
successful performance compared with [MBNT]Cl in this
copper catalyzed coupling reaction. Hence, we continued
further studies using the catalyst A.
[MBNT][Cu4Cl5] catalyst comprises both
Nꢀdonor ligand and
quaternary salt. [MBNT] cation as an efficient ligand and also a
quaternary salt had significant stabilizing effect on the Cu(I)
species. The quaternary ammonium salt prevents nonꢀstable Cu
(I) species from air and aggregation.
Mys’kiv et al. reported the species [Cu4Cl5]– as counter anion
Fig. 2. UV-Vis absorption spectra of pure nicotine, [MBNT]Cl,
[DBNT]Cl2
for
the
quaternary
ammonium
cation
N,N'ꢀ
diallylmorpholinium.31 In addition, Flonani et al. have
investigated a special structure for the species [Cu4Cl5]–.33 This
information, and also the results obtained from the CHN and
ICP analysis of our compound helped us to characterize the
Optical properties of the catalyst
A were also examined by UV–
Vis spectroscopy at room temperature in DMSO solvent. Fig. 3
shows the absorbance spectra of [MBNT]Cl, CuCl and
[MBNT][Cu4Cl5]. The UV–Vis spectrum of [MBNT]Cl shows
a sharp absorption band at 271 nm. The CuCl absorption
spectrum displays a broadening absorption band at around 290
catalyst
A as [MBNT][Cu4Cl5].
By the EDX analysis the presence of copper in the catalyst was
also approved (Fig 1).
nm. In the spectrum of catalyst
A two absorption bands at
around 271 nm and 290 nm are observed.
2 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C5RAA19R0T28ICBLE
K3PO4.3H2O
(1)
DMF
DMF
DMF
DMF
DMF
DMF
140
140
140
130
140
140
10
5
43
95
15
39
ꢀ
8.
K3PO4.3H2O
(3)
9.
K3PO4.3H2O
(3)
1
10.
K3PO4.3H2O
(3)
5
11.
12.
13.
K3PO4.3H2O
(3)
0
K3PO4.3H2O
(3)
5c
32
aReaction conditions: iodobenzene (1 mmol), phenylacetylene (1.1
mmol), oil bath, N2 atmosphere.
Fig. 3. UV–Vis absorption spectra, comparison between pure
CuCl, [MBNT]Cl and [MBNT][Cu4Cl5] spectra.
bGC yield.
cIn the presence of catalyst B.
The catalytic performance of the catalyst
A was examined in
palladiumꢀfree Sonogashira cross coupling reactions. To
evaluate the optimized reaction conditions, a series of screening
experiments was carried out in cross coupling of iodobenzene
with phenylacetylene. We examined the effect of various
reaction parameters including the solvent, base and temperature
on the yields of the coupling products as shown in Table 1. The
results demonstrated that the optimized conditions were as
follows: DMF as the solvent, K3PO4.3H2O (3 eq.) as the base,
140 °C and the catalyst loading 5 mol% (Table 1, entry 9).
As a comparative study, to obtain more information about the
effects of coordination sites in the cation part on the reaction
system, [DBNT][Cu4Cl6] (catalyst
B) in which the cation
[DBNT] has no ꢀdonor active centre was investigated. The
N
results showed that by employing [DBNT][Cu4Cl6] as the
catalyst in the reaction of iodobenzene with phenylacetylene
under the optimized reaction conditions, the corresponding
alkyne product was obtained only in 32% yield after 5 h (Table
1, entry 13), however, the catalyst
A, under the same reaction
Table 1. Optimization of the reaction conditions for the Sonogashira
coupling a
conditions, afforded 95% yield of the corresponding
Sonogashira product. This result indicated that the effect of the
coordination sites in the cation part was an important factor in
the efficiency of the catalyst
A, in which the nitrogenꢀ
coordinating site of cation part can effectively activate and
stable the Cu(I) species during the reaction. Hence,
[MBNT][Cu4Cl5] was chosen as the benchmark catalyst in this
study and applied to the palladiumꢀfree copper catalyzed
Sonogashira crossꢀcoupling reactions of various aryl halides
with phenylacetylene (Table 2) under the optimized parameters.
The electronic and steric effects of various substituted aryl
halides were studied in these reactions. This catalyst complex
was found to be compatible with a wide range of functional
groups such as halogen, cyano, nitro, methoxy and carbonyl on
aryl halides. The aryl halides bearing electronꢀwithdrawing
groups in comparison to the electronꢀrich aryl halides gave
better conversions in shorter reaction times. The steric
hindrance effects of the procedure were examined using 2ꢀ
Temp
(°C)
Catalyst
(mol %)
Yield
(%)b
Entry
Solvent
Base (equiv.)
DMSO
DMF
NMP
DMF
DMF
DMF
140
140
140
140
140
140
tꢀBuOK (3)
tꢀBuOK (3)
tꢀBuOK (3)
KOH (3)
10
10
10
10
10
10
46
79
28
49
62
97
1.
2.
3.
4.
5.
6.
K2CO3 (3)
bromonitrobenzene
(Table
2,
entry
9)
and
2ꢀ
bromochlorobenene (Table 2, entry 18). An increasing
hindrance in the vicinity of the leaving group led to a decrease
in the conversion.
As shown in Table 2, most aryl iodides were successfully
reacted with phenylacetylene to afford the corresponding
K3PO4.3H2O
(3)
K3PO4.3H2O
(2)
DMF
140
10
88
7.
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2ꢀbromopyridine
5
95
alkyne products in excellent yields. Aryl bromides also
converted to the corresponding Sonogashira products.
However, the reactivity of aryl bromides was lower than that of
the aryl iodides and they required longer times giving lower
yields. Substituent effects in the aryl iodides were less
significant than those in the aryl bromides. For example,
coupling of 4ꢀbromoanisole with phenylacetylene (Table 2,
entry 5) was very slow compared with those of 4ꢀiodoanisole
(Table 2, entry 4). Although aryl chlorides are cheaper and
more readily available, they are less reactive substrates than
aryl iodides and bromides in this reaction system.
21.
a
Reaction conditions: aryl halide (1 mmol), phenylacetylene (1.1
mmol), K3PO4.3H2O (3mmol), DMF (3 mL), catalyst
[MBNT][Cu4Cl5] (5 mol%), N2 atmosphere.
b Isolated yield.
The reusability of catalyst is an important topic in the field of
catalysis that is commonly attributed to its stability. We
examined the possibility of recovery and reuse of the catalyst
A
using the Sonogashira reaction between phenylacetylene and 3ꢀ
nitroiodobenzene as the substrates under the same conditions
reported in Table 2. After each run, the reaction solvent was
removed to obtain a solid mixture, which washed with
methanol several times to separate the resulting coupled
product and dried. Then, the resulting mixture was reused
directly for the next run without further purification. As shown
in Fig. 4, the catalyst could be recovered and reused at least 6
times without any significant drop in the product yield, which
indicated a high stability and reusability of the catalyst.
Table 2. Sonogashira coupling reactions of aryl halides with
phenylacetylene using catalyst Aa
Entry
R
H
X
I
Time (h)
Yield (%)
5
7
91
55
43
88
20
91
98
80
38
73
41
59
21
85
20
70
44
5
1.
H
Br
Cl
I
2.
H
8
3.
4ꢀMeO
4ꢀMeO
4ꢀNO2
3ꢀNO2
4ꢀNO2
2ꢀNO2
4ꢀCN
4ꢀCN
4ꢀCHO
4ꢀMeCO
4ꢀI
8
4.
Br
I
10
1.5
1.5
5
5.
6.
I
7.
Br
Br
I
8.
8
Fig. 4 The reusability results of the catalyst A.
9.
2.5
7.5
12
18
0.75
4
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
To date, few studies have been performed to understand the
mechanism of copperꢀassisted Ullmannꢀtype coupling
reactions.35
Br
Br
Cl
I
Taillefer et al36 have reported mechanism of Cuꢀcatalyzed
Sonogashira coupling via an oxidative addition/reductive
elimination pathway, involving a four coordinate Cu(III)
intermediate, which undergoes reductive elimination to expel
the coupled product. Miura and coꢀworkers also suggested a
Cu(I)/Cu(III) mechanistic pathway for copperꢀcatalyzed
coupling reactions.37
4ꢀBr
Br
Br
Br
Br
4ꢀCl
18
13
15
6
Based on these reports, two mechanisms can be put forward for
the our Cu(I)ꢀcatalyzed Sonogashira coupling reactions. In the
oxidative addition/reductive elimination pathway, the chelation
3ꢀCl
2ꢀCl
of Cu(I) with
Nꢀatom of monobenzyl nicotinium, and also
stabilization of Cu(I) species with quaternary salt section,
which inhibit of Cu(I) nonꢀstable species aggregation, makes
Cu(I) catalytic species more reactive toward the oxidative
addition to form the copper(III) complex or stabilizes this
intermediate, promoting the coupling reaction.
9ꢀbromophenanthrene
1ꢀbromonaphthalene
62
40
10
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The first step involves the deprotonation of phenylacetylene by reaction mixture was heated at 65 ˚C in oil bath for 2 hours
K3PO4 base and its coordination with Cu(I) to give a copper(I)ꢀ under N2 atmosphere. The produced solid was isolated by
acetylide intermediate. The copper phenylaceylide can exist in filtration and washed with dichloromethane. Anal. Calcd for
a polymeric form which is in equilibrium with an active C17H21Cl5Cu4N2: C 29.82; H 3.09; N 4.09; Cu 37.12; Found: C
monomeric
catalyst.38
Therefore,
the
structure
of 29.54; H 3.40; N 3.90. The copper content of a 100 ppm
phenylacetylide might be either a monomeric or a polymeric solution of C17H21Cl5Cu4N2 was obtained 36.95% as analyzed
form or both. In the next step, addition of aryl halide by by the ICP technique
oxidative addition leads to formation of fourꢀcoordinated
copper(III) complex, which subsequently undergoes reductive [DBNT][Cu4Cl6]: The obtained [DBNT]Cl2 reacted with CuCl,
elimination and finally, a new C–C bond is formed. Another that this process is similar to the method reported for
mechanism reported by Hwang et al.39 could be proposed for [MBNT]Cl. The Anal.Calcd for C24H28Cl6Cu4N2: C 35.53; H
this ligandꢀaccelerated catalytic reaction, in which the coupling 3.48; N 3.45; Found: C 35.36; H 3.72; N 3.50. The copper
reaction may also proceed by a concerted breaking of the aryl content of a 100 ppm solution of C24H28Cl6Cu4N2 is 30.73% as
halide bond and formation of the new CꢀC bond.
analyzed by the ICP technique.
The absence of Pd contamination in the starting materials,
including the bases and the Cu complex was investigated by General procedure for the Sonogashira cross-coupling:
inductively coupled plasma (ICP) analysis; and no Pdꢀimpurity Aryl halide (1 mmol), phenylacetylene (1.1 mmol, 0.11 ml),
was observed in the used samples.
K3PO4.3H2O (3 mmol, 0.79 g) and
5
mole
%
of
[MBNT][Cu4Cl5] in DMF (2 ml ) were mixed in a round
bottom flask equipped with a condenser under N2 atmosphere.
The mixture was heated in an oil bath at 135ꢀ140 °C and
followed by thinꢀlayer chromatography (TLC) and gas
chromatography (GC). After completion of the reaction, the
mixture was cooled to the room temperature and diluted with
EtOAC and H2O. The coupled product was extracted with
EtOAc and the organic phase was dried over CaCl2, filtered and
concentrated. The residue could be purified by silica gel
column chromatography (hexane:EtOAc). The arylalkyne
products were known compounds and were characterized by 1H
NMR, 13C NMR, FTIR, and MS spectra.
Experimental
Synthesis of pre-catalysts and catalysts
[MBNT]Cl: Monobenzylnicotinium chloride [MBNT]Cl was
prepared in a roundꢀbottom flask by adding benzyl chloride
(0.23 ml, 2 mmol) and nicotine (0.32 ml, 2 mmol) in
acetonitrile solvent (15 ml). The reaction mixture was heated in
70 °C oil bath for 7 hours under an N2 atmosphere. The product
was isolated by solvent evaporation and washing with nꢀ
hexane.
1HꢀNMR(400 MHz, ppm, CDCl3, TMS) δ = 9.32ꢀ9.36 (1H, d,
J= 6.0 Hz), 9.28 (1H, s), 8.19ꢀ8.21 (1H, d, J= 7.6 Hz), 7.40ꢀ7.47
(1H, m), 6.97ꢀ7.07 (5H, m), 5.92 (2H, s), 4.69 (1H, t, J= 12.0
Hz), 3.01 (3H, s), 2.05ꢀ2.14 (2H, m), 1.85ꢀ1.88 (2H, m), 1.45ꢀ
1.65 (1H, m). 13CꢀNMR (100 MHz, CDCl3): δ ppm 143.83,
143.67, 143.39, 132.47, 129.52, 129.28, 129.22, 66.53, 63.74,
56.22, 40.12, 35.61, 26.23.
1-nitro-4-(phenylethynyl)benzene: 1HꢀNMR (400 MHz, ppm,
CDCl3): δ= 8.22 (2H, d, J= 8.8 Hz), 7.66 ( 2H, d, J= 8.8 Hz,),
7.52 ( 2H, m), 7.39 3 H, m). 13CꢀNMR ( 100MHz, ppm,
CDCl3): δ = 147.0, 132.3, 131.9, 130.3, 129.3, 128.5, 123.7,
122.1, 94.7, 87.50.
1-methoxy-4-(phenylethynyl)benzene
ppm, CDCl3): δ= 7.42 (2H, m), 7.38 (2H, d,
(3H, m), 6.79 (2H, d,
= 8.8 Hz), 3.73 (3H, s). 13CꢀNMR (100
:
1HꢀNMR (400 MHz,
= 8.8 Hz), 7.25
J
[DBNT]Cl2: Dibenzylnicotinium chloride [DBNT]Cl2 was
prepared according to the improved method presented in the
previous work.28,29 1 mmol (0.16 ml) of nicotine and 4 mmol
(0.46 ml) of benzyl chloride were mixed in 15 ml acetonitrile
and the reaction mixture was heated at 70°C for 36 h. Then, the
solvent was evaporated and the residue was washed with
dichloromethane.
1HꢀNMR(400 MHz, ppm, DMSOꢀd6, TMS) δ = 9.60 (1H, s),
9.39ꢀ9.41 (1H, d, J= 6.0 Hz), 9.03ꢀ9.05 (1H, d, J= 8.0 Hz),
8.41ꢀ8.45 (1H, t, J= 6.7 Hz), 7.47ꢀ7.63 (10H, m), 5.96 (2H, s),
5.33ꢀ5.37 (1H, t, J= 10.8 Hz), 4.72 (1H, d, J= 12.4), 4.69 (1H,
d, J= 12.0 Hz), 3.36 (3H, s), 2.50ꢀ3.05 (2H, m), 2.12ꢀ2.33 (2H,
m), 1.29ꢀ1.49 (2H, m). 13CꢀNMR (100 MHz, DMSOꢀd6):
δppm 148.20, 147.56, 146.15, 132.91, 132.47, 130.30, 129.48,
129.22, 128.96, 128.37, 74.57, 65.16, 63.77, 62.94, 41.23,
25.58, 18.69.
J
MHz, ppm, CDCl3): δ = 159.60, 133.0, 131.4, 128.30, 127.90,
123.60, 115.40, 114.0, 89.30, 88.0, 55.30.
2-(phenylethynyl)pyridine
CDCl3): δ= 8.55 (1H, d,
7.55(2H, m), 7.46 ( 1H, d,
:
J
1HꢀNMR (400 MHz, ppm,
=5Hz), 7.58ꢀ7.63 (1H, m), 7.51ꢀ
J
=7Hz,), 7.26ꢀ7.35( 2H, m), 7.20
(1H, s), 7.12ꢀ7.17 (1H, m).
1
1,2-diphenylethyne: HꢀNMR (400 MHz, ppm, CDCl3): δ =
7.57ꢀ7.60 ( 4H, m), 7.37ꢀ7.41 ( 6H, m). 13CꢀNMR (100 MHz,
ppm, CDCl3): δ= 131.70, 128.50, 128.40, 123.4, 89.60.
1-Nitro-3-phenylethynyl-benzene: 1HꢀNMR (400 MHz, ppm,
CDCl3): δ = 8.31 (dd, 1H), 8.11 (m, 1H), 7.76 (ddd, 1H), 7.76
(ddd, 1H), 7.46ꢀ7.50 (m, 3H), 7.31ꢀ7.32 (m, 3H). 13CꢀNMR
(100 MHz, CDCl3): δ = 148.2, 137.2, 131.8, 129.4, 129.1,
128.5, 126.4, 125.2, 122.9, 122.2, 91.9, 86.9. FTꢀIR (KBr, cmꢀ
1): ν = 2930, 2214, 1596, 1513, 1345, 853.
[MBNT][Cu4Cl5]: in a round bottom flask [MBNT]Cl (2
mmol) and copper(I) chloride (1 mmol, 0.099 g), freshly
recrystallized from HCl, were mixed in 5 ml of methanol. The
1-(4-Phenylethynyl-phenyl)-ethanone: 1HꢀNMR (300 MHz,
ppm, DMSO): δ = 8.0 (d, 2H), 7.7 (d, 2H), 7.6 (m, 2H), 7.5 (m,
3H), 2.6 (s, 3H). 13CꢀNMR (100 MHz, CDCl3): δ = 197.5,
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 5

RSC Advances
Page 6 of 7
ARTICLE
VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C5RA19028B
136.3, 131.7, 131.6, 128.8, 128.5, 128.2, 122.6, 92.7, 88.6,
26.6. FTꢀIR (KBr, cmꢀ1): ν = 3080, 2930, 2216, 1679, 1603,
1441, 1403, 12651175.
17 A. R. Hajipour, G. Azizi, A. E. Ruoho, Syn. Lett., 2013, 254.
18 K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett.
1975, 16, 4467.
,
19 A. M. Thomas, A. Sujatha, G. Anilkumar, R. S. C. Adv., 2014
, 21688.
4
20 C. H. Lin, Y. J. Wang, C. F. Lee, Eur. J. Org. Chem., 2010, 48
,
Conclusions
4368.
In this work, we found [monobenzyl nicotinium]+[Cu4Cl5]‾ as an
efficient and stable catalyst in palladiumꢀfree Sonogashira crossꢀ
coupling reactions. By catalytic amounts of this ionic complex, a
variety of aryl halides reacted with phenylacetylene and produced
the corresponding substituted aromatic alkynes in good to excellent
yields.
21 P. Saejueng, C. G. Bates, D. Venkataraman, Synthesis, 2005
10, 1706.
22 Y. F. Wang, W. Deng, L. Liu, Q. X. Guo, Chin. Chem. Lett.
2005, 16, 1197.
,
23 D. Ma, F. Liu, Chem. Commun., 2004, 1934.
24 J. H. Li, J. L. Li, D. P. Wang, S. F. Pi, Y. X. Xie, M. B. Zhang,
X. C. Hu, J. Org. Chem., 2007, 72, 2053.
Acknowledgements
25 A. R. Hajipour, F. Rafiee, Appl. Organomet. Chem., 2014, 28
,
595ꢀ597.
We gratefully acknowledge the funding support received for this
project from the Isfahan University of Technology (IUT), IR Iran,
Further financial support from the center of Excellence in Sensor and
Green Chemistry Research (IUT) is gratefully acknowledged.
26 A. R. Hajipour, S. H. Nazemzadeh, F. Mohammadsaleh,
Tetrahedron. Lett., 2014, 55, 654.
27 A. R. Hajipour, F. Mohammadsaleh, Tetrahedron. Lett., 2014,
55, 3459.
†
Electronic Supplementary Information (ESI) available:
28 A. R. Hajipour, R. Pourkaveh, Synlett., 2014, 25, 1101.
29 A. R. Hajipour, R. Pourkaveh, H. Karimi, Appl. Organomet.
Chem., 2014, 28, 879.
Characterization data of products. See DOI: 10.1039/b000000x/
a Pharmaceutical Research Laboratory, Department of Chemistry, Isfahan
University of Technology, Isfahan 84156, IR of Iran
30 A. R. Hajipour, Y. Heidari, G. Kozehgary, R. S. C. Adv., 2015,
Tel.: + 98 313 391 3262; fax: + 98 313 391 2350; e-mail: haji@cc.iut.ac.ir,
arhajipour@wisc.edu
5, 61179ꢀ61183.
b Department of Pharmacology, University of Wisconsin, Medical School,
1300 University Avenue, Madison, 53706ꢀ1532, WI, USA
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29, 505.
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6 | J. Name., 2012, 00, 1-3
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Journal Name
RSC Advances
View Article Online
DOI: 10.1039/C5RAA19R0T28ICBLE
The new catalytic complex [MBNT][Cu4Cl5] having a
synergistic effect of coordination and electrostatic
interactions was found to be efficient in palladiumꢀfree
copperꢀcatalyzed Sonogashira coupling.
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