Green synthetic method of N-arylamides using recyclable cheap metal catalyst

Article abstract of DOI:10.1016/j.tetlet.2020.152327

Magnetically separable and reusable Fe/Cu oxide (Fe₃O₄-Cu₂O) nanoparticles were employed as an efficient catalyst for the arylation of benzamide, which was carried out with a range of both arylboronic acid and benzamide to afford N-arylamide in good to excellent yield.

Full text of DOI:10.1016/j.tetlet.2020.152327

Tetrahedron Letters 61 (2020) 152327
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Green synthetic method of N-arylamides using recyclable
cheap metal catalyst
Xingyang Wang , Jianhui Liu a,b, , Guanghui An a
a
⇑
a
School of Petroleum and Chemical Engineering, Dalian University of Technology, Panjin Campus, Panjin, Liaoning Province 124221, PR China
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Magnetically separable and reusable Fe/Cu oxide (Fe O -Cu O) nanoparticles were employed as an effi-
3
4
2
Received 28 May 2020
Revised 17 July 2020
Accepted 1 August 2020
Available online 26 August 2020
cient catalyst for the arylation of benzamide, which was carried out with a range of both arylboronic acid
and benzamide to afford N-arylamide in good to excellent yield.
Ó 2020 Elsevier Ltd. All rights reserved.
Keywords:
Fe O -Cu O
3 4 2
Chan-Lam reaction
Phenylboronic acids
Benzamide
N-Arylamides are important subunits found in natural products
that have applications in material sciences, pharmaceuticals, and
as biologically active inhibitors[1]. In addition to the traditional
synthetic reactions from carboxylic acid derivatives and amines
Supported-magnetic catalysts have received great attention in
recent years and are an integral part of catalysis science and tech-
nology[8]. A magnetic catalyst can exhibit improved performance
and be conveniently orientated, separated from the catalytic pro-
[
2], modern CAN coupling reactions also appear in the literature..
3 4
cess. Usually, metals and metal oxides can be loaded on Fe O
While many significant Pd-catalysed CAN cross-coupling reactions
have been developed in recent years[3], the use of expensive palla-
dium and elaborate phosphorylated ligands limit their applications
in large-scale production. Therefore, the copper catalytic system
has received extensive attention. Mukkamala et al[4]. reported a
CAN bond-forming reaction between phenylboronic acid and ben-
zamide catalysed by copper(I) iodide. But the reaction needs to be
carried out under oxygen conditions, and the catalyst cannot be
recovered. Constructing CAN bonds with iodobenzene and amine
compounds at the same time has also been a focus of researchers.
Ribas et al.[5] reported a CAN bond-forming reaction between
iodobenzene and benzamide catalysed by copper(I) iodide. Islam
et al.[6] successively reported that copper catalyst was prepared
from chloromethyl polystyrene and nanoparticle-graphene-based
composite materials, used as catalyst for N-arylation and O-aryla-
tion. Punniyamurthy et al.[7] used CuO to catalyze the coupling
of phenylboronic acid and benzamide with a yield of 15%. How-
ever, transition metals as catalysts face problems that are difficult
to separate and recover.
nanoparticles (NPs) for easy separation by magnetism. Wei et al.
[9] reported building a CAN bond catalyzed by recyclable, low-cost
and environmentally benign magnetic nanoparticles of ferrite
complex oxides. Ramon et al.[10] described copper impregnated
in a magnetite catalyst as an efficient and green catalyst for the
selective multicomponent reaction of terminal alkynes, aldehydes
and secondary amines. Phukan et al.[11] reported Cu-doped CoFe
2
-
O
4
nanoparticles as magnetically recoverable catalyst for CAN
cross-coupling reaction. In addition, Gawande[12], Sharma[13],
Shelke[14] and others[15] reported the application of copper
nano-magnetic catalyst for the CAN bond formation. Although
much progress has been achieved, it is still necessary to develop
a green and efficient method for synthesizing N-arylamides by
the coupling reaction. In this paper, we report a N-arylation of ben-
zamides with arylboronic acids using Fe
a catalyst, which can be easily recovered.
Fe -Cu O NPs were prepared according to Guo et al.[16]. The
amount of copper supported on the Fe , measured by induc-
3 4 2
O -Cu O nanoparticles as
3
O
4
2
3 4
O
tively coupled plasma mass spectrometry (ICP-MS) analysis, was
À1
0
.64 g of Cu per g of catalyst (10.1 mmol.g ). The crystalline nat-
ure and composition of the as-synthesized products were charac-
terized by XRD, as shown in Fig 1. Six
⇑
Corresponding author.
E-mail address: liujh@dlut.edu.cn (J. Liu).
https://doi.org/10.1016/j.tetlet.2020.152327
040-4039/Ó 2020 Elsevier Ltd. All rights reserved.
0

X. Wang et al.
Tetrahedron Letters 61 (2020) 152327
3 4 2
Fig. 3. SEM image of Fe O –Cu O NPs.
reaction conditions are summarized in Table1. In an initial trial,
we examined different bases in the absence of ligands. Of the sev-
eral bases chosen, KOH had the best effect for this transformation,
leading to a 42% yield of 3a (Table 1, entry 1). Other bases such as
3 4 3 4 2
Fig 1. XRD patterns of (a) Fe O NPs and (b) Fe O –Cu O NPs..
2 3 2 3 2 3
K CO , Na CO and Cs CO had poorer performance, affording lower
major reflections located at approximately 30.1, 35.4, 43.1, 53.3,
6.9 and 62.5 can be respectively assigned to the diffraction of
yields of 10, 24 and 36%, respectively (Table 1, entries 2–4). Then,
we tested four ligands, triphenylphosphine (L1), N,N’-dimethy-
lethylenedi-amine) (L2), 4-dimethylaminopyridine (L3) and 1,2-
bis(diphenyl-phosphino)ethane (L4). Among them, L3 was
5
Fe
422), (511) and (440) planes (JCPDS 19–0629) (Fig 1 line a), indi-
cating the crystalline cubic phase of the catalyst. For the XRD pat-
tern of the Fe -Cu O composite (Fig 1, line b), the main peaks are
similar to those of the native Fe particles, which reveals that the
crystal structure of the Fe is well-maintained after the loading
by Cu O during the reaction process. Compared to pure Fe
new diffraction peaks located at approximately 29.6, 36.4, 42.3,
1.3, 73.5 and 77.3 can be assigned to the diffraction of Cu
rhombic dodecahedral crystals in the cubic phase from the
3 4
O NPs with a cubic phase from the (220), (311), (400),
(
the most effective, and the yield of 3a was 59% (Table 1, entry
3
O
4
2
7
3
), while those for the other three ligands were 39%, 46% and
3%, respectively (Table 1, entries 5, 6 and 8). Next, the reaction
3 4
O
3 4
O
was carried out using different solvents, including DMF, toluene,
CH OH and CH CN, to examine the solvent effect. We found that
2
3 4
O ,
3
3
none of these four solvents was as good as DMSO, providing 3a
at 49%, 54%, 35% and 28% yields, respectively (Table 1, entries 9–
6
2
O
1
2). We then optimized the amounts of base and catalyst. When
(
(
110), (111), (200), (220), (311) and (222) planes respectively
JCPDS 05–0667).
The morphology of the samples was determined using SEM
the amount of the base increased to 1.5 mmol, the yield of 3a
increased to 69% (Table 1, entry 13). While the use of 2 mmol of
base led to a yield of 80% (Table 1, entry 14). The further addition
of KOH to 2.5 mmol did not further improve the yield (Table 1,
entry 15). Notably, the amount of base is an important parameter
in this reaction system. Regarding the amount of catalyst, it was
found that the yield decreased when 25 mol% of the catalyst was
used (Table 1, entry 16). When the catalyst was increased to
images (Fig 2). It can be seen that the Fe
ticles with a uniform size and a diameter between 18 and 23 nm.
From Fig 3, the Cu O is supported on the surface of the Fe
The Cu O is visible as spherical particles with a particle size of
3 4
O NPs are spherical par-
2
3 4
O .
2
approximately 580 nm.
After we obtained the Fe
3 4 2
O -Cu O NPs, we started our investiga-
3
5 mol%, the yield did not change and remained at 80% (Table 1,
entry 17).
After optimizing the reaction conditions, we explored the scope
of the substrates for this Cu O-catalysed coupling of benzamides
tion by performing an optimization of the solvents, bases and
ligands used for the coupling of benzamide and phenylboronic acid,
which were used as model substrates. The results for the different
2
and arylboronic acids (Table 2). Under optimal conditions, most
substrates were obtained in excellent yields. First, a series of aryl-
boronic acids were employed to react with benzamide (Table 2,
entries 1–6). As shown in this table, the yields from arylboronic
acids with an electron-withdrawing group on the benzene ring
were high, such as those achieved with 4-chloro (85%), 3-chloro
(
82%) and 4-fluoro (89%) (Table 2, entries 2–4). For phenylboronic
acids with an electron-donating group, such as 4-methyl or 4-
methoxy groups (Table 2, entries 5 and 6), relatively low yields
were obtained 79 and 78%, respectively.The results indicate that
electron-withdrawing
groups on the aryl ring are more favourable than electron-
donating groups. Then, benzamide with various substituents (Cl,
F, NO
2
and Me) was used for the present coupling reaction. Strong
and F, afforded a bet-
electron-withdrawing groups, including NO
2
ter yield (85 and 89% respectively), followed by the chlorinated
product (ca. 70%). The weaker electron-donating methyl group
had a somewhat lower yield of 65% (Table 2, entries 7–11). Further
3 4
Fig 2. SEM image of Fe O NPs.
2

X. Wang et al.
Tetrahedron Letters 61 (2020) 152327
Table 1
Table 2
a
a
Optimization of reaction conditions
Reaction of different benzamides and different phenylboronic acids .
Entry
1
Benzamide
Phenylboronic acid
Yield b
%
80 3a
2
3
4
5
6
7
85 3b
82 3c
89 3d
79 3e
78 3f
71 3g
.
Yield b(%)
Entry
Ligand
Solvent
Base
KOH
1
2
3
4
5
6
7
8
9
—
—
—
—
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
42
10
24
36
39
46
59
33
49
54
35
28
69
80
80
78
80
K
2
CO
3
Na
Cs
2
CO
3
CO
2
3
L1
L2
L3
L4
L3
L3
L3
L3
L3
L3
L3
L3
L3
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
KOH
10
11
12
13
14
15
16
17
Toluene
CH
CH
3
OH
CN
3
c
d
e
f
DMSO
DMSO
DMSO
DMSO
DMSO
8
9
70 3h
85 3i
g
[
a] Reaction conditions: phenylboronic acid (1 mmol), benzamide (0.5 mmol),
catalyst (30 mol%), ligand (20 mol%), solvent (2 mL), base (1 mmol), 100℃, 2 h, air.
b] Isolated yield. [c] 1.5 mmol of KOH. [d] 2 mmol of KOH. [e] 2.5 mmol of KOH. [f]
5 mol% of catalyst. [g] 35 mol% of catalyst.
[
2
10
89 3j
1
1
1
2
65 3k
93 3l
illustrative examples of the coupling reactions of benzamides and
arylboronic acids with various substituents on the phenyl ring of
both substrates are outlined below (Table 2, entries 12–18). Gener-
ally, a variety of combinations were compatible, and the CAN cou-
pling proceeded with a range of amides and arylboronic acids with
good to excellent yields (78–93%). In particular, upon the treat-
ment of an aliphatic amide with phenylboronic acid, the corre-
sponding coupling product was obtained with a moderate yield
of 68% (Table 2, entry 19).
1
3
4
90 3m
85 3n
87 3o
1
3 4 2
To evaluate the reusability the of Fe O -Cu O NPs, six continu-
ous runs were performed using benzamide and phenylboronic acid
under optimal conditions. After the end of each reaction, the reac-
tion mixture was filtered, and the catalyst was reused in the next
batch. We found that the catalyst can be reused up to the 5th cycle
without any significant loss of catalytic activity. After the 5th cycle,
though, a significant loss of catalytic activity was observed (Fig 4).
The putative N-arylation mechanism is shown in Fig 5. Initially,
the ligand DMAP binds to the copper in catalyst A, and then mono-
valent copper is inserted into the NAH bond of the aryl formamide
through oxidative addition to form a copper coordination complex
B. The arylboronic acid undergoes ligand exchange to obtain C
through metal transfer reaction, and finally the coupling product
is obtained after reduction elimination. At the same time, the
monovalent copper catalyst is regenerated and enters a new cat-
alytic cycle.
15
16
83 3p
86 3q
78 3r
68 3s
1
1
1
7
8
9
In summary, we have developed a highly efficient, green and
simple method for synthesizing N-arylbenzamides starting from
[
(
a] Reaction conditions: phenylboronic acid (1 mmol), benzamide (0.5 mmol), KOH
2 mmol), Fe -Cu O (30 mol%), DMAP (20 mol%), DMSO (2 mL), 100℃, 2 h, air. [b]
3
O
4
2
benzamide and phenylboronic acid by using Fe
3
O
4 2
-Cu O NPs as a
Isolated yield.
3

X. Wang et al.
Tetrahedron Letters 61 (2020) 152327
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgments
The financial support for this research comes from the State Key
Laboratory of Fine Chemicals (Panjin) (Grant No. JH2014009) pro-
ject and basic research from key universities fund.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tetlet.2020.152327.
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