Ligand-free CuTC-catalyzed N-arylation of amides, anilines and 4-aminoantipyrine: Synthesis of N-arylacrylamides, 4-amido-N-phenylbenzamides and 4-amino(N-phenyl)antipyrenes

Article abstract of DOI:10.1002/aoc.3080

N-Arylation of amides and anilines with aryl iodides was efficiently catalyzed by copper thiophenecarboxylate under ligand-free conditions with good to excellent yields. A variety of substituted aryl iodides, amides, anilines and 4-aminoantipyrine were found to be applicable to the simple catalytic system. Furthermore, some practical, unique secondary amides, such as N-arylacrylamides and 4-amido-N-phenylbenzamides, and 4-amino(N-phenyl)antipyrenes, which are difficult to obtain by the classical methods, were prepared.

Full text of DOI:10.1002/aoc.3080

Full Paper
Received: 30 August 2013
Revised: 26 September 2013
Accepted: 2 October 2013
Published online in Wiley Online Library: 26 November 2013
(wileyonlinelibrary.com) DOI 10.1002/aoc.3080
Ligand-free CuTC-catalyzed N-arylation of
amides, anilines and 4-aminoantipyrine:
synthesis of N-arylacrylamides, 4-
amido-N-phenylbenzamides and 4-amino
(N-phenyl)antipyrenes
Zheng-Jun Quana,b*, Hai-Dong Xiaa,b, Zhang Zhanga,b, Yu-Xia Daa,b
and Xi-Cun Wanga,b*
N-Arylation of amides and anilines with aryl iodides was efficiently catalyzed by copper thiophenecarboxylate under ligand-
free conditions with good to excellent yields. A variety of substituted aryl iodides, amides, anilines and 4-aminoantipyrine
were found to be applicable to the simple catalytic system. Furthermore, some practical, unique secondary amides, such as
N-arylacrylamides and 4-amido-N-phenylbenzamides, and 4-amino(N-phenyl)antipyrenes, which are difficult to obtain by
the classical methods, were prepared. Copyright © 2013 John Wiley & Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web-site.
Keywords: CuTC; N-arylation; amides; anilines; aryl iodides
been reported.[9] Nevertheless, the reaction conditions as well as
the reaction temperature and substrate scope still remain limited.
Introduction
N-Arylamides and diarylamines are important synthetic building
blocks that are prevalent in many bioactive compounds and
medicinal agents, and have important roles in organic synthesis
and biological and pharmaceutical research.[1] As a more efficient
and facile method, the transition metal-catalyzed coupling
reaction of aryl halides or pseudo halides and amides or anilines
has been attractive for many years.[2] In particular, the
palladium-[3] and copper-catalyzed[4] N-arylation of amides and
anilines with aryl bromides and iodides have become well-
established processes in organic synthesis. However, the use of
expensive palladium and elaborate phosphorated ligands
prevent these reactions from being employed to their full poten-
tial.[5] The classical copper-catalyzed Ullmann and Goldberg
reactions were applied as alternative C—N bond-forming meth-
odologies in academic and industrial laboratories for many de-
cades.[6] Unfortunately, these methods suffered from reduced
synthetic scope, a limited substrate scope, the moderate yields
obtained and harsh reaction conditions such as high temperature
(up to 210°C) and the presence of stoichiometric amounts of
copper reagents.[7] Thus the exploration of new cross-coupling
strategies that use lower reaction temperatures and shorter time
has emerged as a challenging task among the synthetic community.
In recent years, the use of ligands to facilitate the copper-catalyzed
N-arylation of amides and anilines with aryl halides has made great
improvements.[8] However, the high cost and/or tedious prepara-
tion of some ligands used in these important protocols are
drawbacks. In an important advance, the development of ligand-
free catalytic systems for Goldberg-type coupling reactions has also
Therefore, considerable efforts should be channeled to the devel-
opment of new, simple and milder methods for the N-arylation of
amides and anilines.
Recently, copper thiophenecarboxylate (CuTC) has been
developed for organic catalysis;[10] however, to the best of our
knowledge, no CuTC-catalyzed N-arylation of amides, anilines
and 4-aminoantipyrine with aryl iodides has been disclosed. In
continuation of our efforts in copper-catalyzed C—N bond
formations,[11] herein we first report an efficient, simple and
environmentally benign CuTC-catalyzed N-arylation of amides
and anilines with aryl iodides at 100 °C for 6 h in DMSO under
N2. The mild reaction conditions, no requirement for additives
and easy-to-handle procedure make this method attractive.
*
Correspondence to: Xi-Cun Wang, Gansu Key Laboratory of Polymer Materials,
College of Chemistry and Chemical Engineering, Northwest Normal University,
Anning East Road 967#, Lanzhou, Gansu 730070, People’s Republic of China.
Email: wangxicun@nwnu.edu.cn
Zheng-Jun Quan, Key Laboratory of Eco-Environment-Related Polymer Materials,
Ministry of Education of China, Gansu 730070, People’s Republic of China.
Email: quanzhenjun@hotmail.com; quanzj@nwnu.edu.cn
a Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of
Education of China, Gansu 730070, People’s Republic of China
b Gansu Key Laboratory of Polymer Materials, College of Chemistry and
Chemical Engineering, Northwest Normal University, Gansu 730070, People’s
Republic of China
Appl. Organometal. Chem. 2014, 28, 81–85
Copyright © 2013 John Wiley & Sons, Ltd.

Z.-J Quan et al.
acryloyl chloride is prepared by using the toxic thionyl chloride
and it also does harm to our health. Thus we initiated our inves-
tigation by examining the conditions under which the coupling
reaction of iodobenzene (1a) and acrylamide (2a) proceeded
efficiently. Selected results from our screening experiments are
summarized in Table 1. Several simple copper salts were exam-
ined, and only low amounts of products were obtained
(Table 1, entries 1–5). In contrast, this reaction provided promis-
ing results in the presence of catalytic amounts of CuTC, as N-
phenylacrylamide (3aa) was obtained in moderate yield (51%;
entry 6). Further investigation revealed that CuTC (0.15 equiv.)
was sufficient for the cross-coupling reaction (entries 6–8). The
following screening conditions suggested that t-BuONa was
highly efficient for the reaction (entries 7, 9 and 10). Among var-
ious solvents tested, DMSO was the best in yielding the product
(entries 11–13). Mixed solvents using DMSO/H2O and DMF/H2O
were tested and the results indicated that these solvents did
not have a notable influence in this reaction (entries 10–15). We
then examined the reaction temperature and found that low
temperature decelerated the reaction rate, giving a lower yield
(entry 16). Meanwhile, increasing the reaction temperature to
120 °C did not improve the yield, which might be due to the
Experimental
The mixture of aryl iodides (1 mmol), amides, anilines or
4-aminoantipyrine (1.2 mmol), CuTC (0.15 mmol) and t-BuONa
(2.0 mmol) in DMSO (3 mL) was stirred at 100 °C for 6 h under N2.
The reaction mixture was cooled to room temperature, quenched
with saturated NH4Cl solution (2 mL) and then extracted with ethyl
acetate (3 × 10 mL). The combined organic extracts were washed
with NaOH (1 M, 2 ml), brine and dried over Na2SO4. The crude prod-
uct was purified by flash column chromatography (silica gel; ethyl
acetate/petroleum ether) to afford the corresponding secondary
amides, diarylamines and 4-amino(N-phenyl)antipyrenes. Melting
points were determined on an XT-4 electrothermal micromelting
point apparatus and uncorrected. NMR spectra were recorded for
1H NMR (400 MHz) and 13C NMR (100 MHz) on a Varian Mercury
plus-400 instrument, using TMS as internal standard. Mass spectra
were recorded on a Bruker APEX II instrument. Elemental analyses
were performed on a Carlo-Erba 1106 elemental analysis instrument.
See supporting information for spectroscopic data of the products.
Results and Discussion
Usually, the analogues of N-phenylacrylamide are obtained by
the classical procedure using acryloyl chloride,[12] however,
Table 1. Optimization of reaction conditions for iodobenzene (1a) and acrylamide (2a)a
Entry
Catalyst (mol %)
Base
K3PO4
Solvent
DMSO
Temperature (°C)
Time (h)
Yield (%)b
1
Cu2O (10)
CuI (10)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
80
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
6
5
7
6
6
6
22
17
2
K3PO4
DMSO
3
CuSO4.5H2O (10)
CuNPs (10)
K3PO4
DMSO
Trace
12
4
K3PO4
DMSO
5
CuBr(PPh3)2 (10)
CuTC (10)
K3PO4
DMSO
42
6
K3PO4
DMSO
51
7
CuTC (15)
K3PO4
DMSO
65
8
CuTC (20)
K3PO4
DMSO
65
9
CuTC (15)
K2CO3
DMSO
45
10
11
12
13
14
15
16
17
18
19
20
21
22
CuTC (15)
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
t-BuONa
DMSO
79
CuTC (15)
DMF
71
CuTC (15)
Toluene
1,4-Dioxane
DMSO/H2O
DMF/H2O
DMSO
67
CuTC (15)
56
CuTC (15)
78c
71c
70
CuTC (15)
CuTC (15)
CuTC (15)
DMSO
120
100
100
100
100
100
73
CuTC (15)
DMSO
71
CuTC (15)
DMSO
79
CuSO4.5H2O (15)/2-thenoic acid (30)
Cu2O (15)/2-thenoic acid (30)
CuI (15)/2-thenoic acid (30)
DMSO
10
DMSO
27
DMSO
22
aReaction conditions: iodobenzene (1a, 1.0 mmol), acrylamide (2a, 1.2 mmol), base (2.0 mmol), solvent (3.0 ml), under nitrogen.
bIsolated yield.
cH2O (1.0 mmol) was added to the reaction.
wileyonlinelibrary.com/journal/aoc
Copyright © 2013 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2014, 28, 81–85

Ligand-free CuTC-catalyzed N-arylation
aryl iodides bearing electron-donating groups such as methyl
and methoxyl gave the desired products in higher yields
(entries 5 and 6). It was observed that aryl iodides bearing
ortho-substituent still exhibited high reactivity, with the desired
product 3f being isolated in a good yield (entry 7).
thermal polymerization of acrylamide at higher reaction tempera-
tures (entry 17). The time was also screened, and the yield de-
creased to 71% when the cross-coupling reaction proceeded for
only 5 h. Meanwhile, increasing the time to 7 h did not improve
the yield (entries 18 and 19). Under these optimized conditions,
the combination of simple copper salts with thiophene-2-carboxylic
acid as catalyst systems was studied and we found that the effi-
ciency of the combination was not ideal (entries 20–22). Hence
the optimal conditions of 0.15 equiv. CuTC and 2.0 equiv. t-BuONa
in DMSO at 100 °C under N2 were used for further investigations.
With the optimized conditions in hand, the reaction of
acrylamide (2a) with substituted aryl iodides was examined.
In general, all the aryl iodides yielded the corresponding
N-arylacrylamides with good yields (Table 2, entries 1–7). To
date, the construction of such amides by Cu-catalyzed cross-
coupling is rare.[13] The results indicated that aryl iodides
bearing electron-withdrawing groups such as fluoro, chloro
and bromo afforded relatively lower yields (entries 2–4), while
Encouraged by this result, we extended the cross-coupling
reaction of aryl iodides with aromatic amides, such as benzamide
(2b), 3-nitrobenzamide (2c), 4-iodobenzamide (2d) and 3-
methylbenzamide (2e), and found that the corresponding C—N
cross-coupling products were obtained in good to excellent yields
(entries 8–16). In addition, aliphatic amides such as acetamide (2f)
and 2-phenylacetamide (2 g) were adapted to the reaction to give
the N-arylation products in good yields (entries 17–24). We were
pleased to find that the cross-coupling reactions of 4-iodo-N-
phenylbenzamide (3bh) with amides (2b and 2f) were conducted
successfully to afford the thrilling products 3da and 3db (entries
25 and 26), which were difficult to obtain by classical methods
because of protection and deprotection of amino required in the
Table 2. CuTC-catalyzed N-arylation of amidesa
Entry
R1
R2
Product
Yield (%)b
1
H (1a)
Vinyl (2a)
3aa
3ab
3 ac
3ad
3ae
3af
79
65
67
68
75
77
73
86
78
80
87
88
82
75
77
85
85
73
71
75
81
83
77
78
69c
67c
63c
65c
2
4-F(1b)
2a
3
4-Cl (1c)
2a
4
4-Br (1d)
2a
5
4-Me (1e)
2a
6
4-MeO (1f)
2-Me (1 g)
1a
2a
7
2a
3ag
3ba
3bb
3bc
3bd
3be
3bf
3bg
3bh
3bi
8
Ph (2b)
9
1b
2b
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
1d
2b
1e
2b
1f
2b
1 g
2b
1a
3-NO2C6H4 (2c)
1a
4-IC6H4 (2d)
1a
3-MeC6H4 (2e)
1a
Me (2f)
3ca
3cb
3 cc
3 cd
3ce
3cf
1b
2f
1c
2f
1d
2f
1e
2f
1f
2f
1 g
2f
3cg
3ch
3da
3db
3 dc
3dd
1a
benzyl (2 g)
3bh
3bh
3bh
1 h
2b
2f
2a
2a
aReaction conditions: aryl iodides (1.0 mmol), amides (1.2 mmol), CuTC (0.15 mmol), t-BuONa (2.0 mmol), DMSO (3.0 ml), 100 °C, 6 h, under
nitrogen.
bIsolated yield.
c110 °C, 10 h.
Appl. Organometal. Chem. 2014, 28, 81–85
Copyright © 2013 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

Z.-J Quan et al.
operation. However, the coupling reaction of 4-iodo-N-
phenylbenzamide (3bh) with acrylamide (2a) could not
successfully proceed to afford the desired product at 100 °C
for 6 h. Unexpectedly, the coupling reaction of 4-iodo-N-
phenylbenzamide (3bh) with acrylamide (2a) afforded the product
4-amino-N-phenylbenzamide 3 dc when the reaction was carried
out at 110 °C for 10 h (entry 27), and acryloyl group was dissociated
in the process. Next, the reaction of acrylamide (2a) with 4-iodo-
N-m-tolylbenzamide (1 h) was carried out to afford 4-amino-
N-m-tolylbenzamide (3dd), which further confirmed that
acryloyl group was dissociated in the reaction[14] (entry 28).
Next, we explored the scope of this CuTC-catalyzed N-arylation
of the aniline reaction. By using the above-optimized conditions,
we accomplished this transformation. Significantly, all the aryl
iodides yielded the corresponding diarylamines with good to
excellent yields (Figure 1). A poor yield was obtained with 4-
fluorobenzenamine 5e because of the electron-withdrawing group
of fluoro. In contrast, anilines substituted by electron-donating sub-
stituents such as methyl group afforded the desired diarylamine
derivatives (5c, 5d, 5f) in good yields. However, ortho substituents
hampered the reaction and 75% isolated yield of 5 g was obtained
with 2-chlorobenzenamine. It is noteworthy that the heterocyclic
aniline pyridin-2-amine could also be coupled with iodobenzene
to afford the corresponding diarylamine 5i with a yield of 85%.
The 4-aminoantipyrine motif is a ubiquitous feature of natural
products and is also a metabolite of aminopyrine with analgesic.
Also, it is used as a reagent for biochemical reactions producing
peroxides or phenols, and to measure extracellular water.[15]
Based on the above reports, we explored the cross-coupling reac-
tion of 4-aminoantipyrine (6) with aryl iodides. Excitingly, our
catalytic system efficiently promotes the reactions and good to
excellent yields were obtained (Figure 2).
The mechanism for CuTC-catalyzed N-arylation of amides, anilines
and 4-aminoantipyrine lies in the formation of CuI and CuIII interme-
diates, which has been substantiated by several reports.[16] This
mechanism may possibly involve the three following elementary
steps: oxidative addition of the aryl iodides to copper(I) generating
a transient CuIII species, nucleophilic substitution of copper-bound
Figure 1. CuTC-catalyzed cross-coupling reaction of anilines with aryl iodides.
Figure 2. CuTC-catalyzed cross-coupling reaction of 4-aminoantipyrine with aryl iodides.
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Copyright © 2013 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2014, 28, 81–85

Ligand-free CuTC-catalyzed N-arylation
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Conclusions
We have developed a highly efficient, simple, and environmen-
tally friendly protocol for N-arylation of amides, anilines and 4-
aminoantipyrine catalyzed by CuTC. A wide range of aryl iodides,
amides and anilines were found to be applicable to the ligand-
free catalytic systems. In addition, some novel structures of
secondary amides and 4-amino(N-phenyl)antipyrenes, difficult
to obtained by the classical methods, were prepared, which
makes this approach attractive.
Acknowledgments
We are thankful for the financial support from the NSFC (Nos.
21362032, 21362031 and 21062017), the NSF of Gansu Province
(No. 1208RJYA083), and the Scientific and Technological Innova-
tion Engineering program of NWNU (Nos. nwnu-kjcxgc-03-64,
nwnulkqn-10-15).
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